Kinetics of crystallization of FeB-based amorphous alloys studied by neutron thermo-diffrac

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热分析(结晶动力学)

95 100 105 110 115 120 125
Temperature,oC
G R t
CHANGZHOU UNIVERSITY
影响结晶速度的因素
➢ 结晶过程主要分为成核与生长两个过程, 因此, 影响成核和生长过程的因素都对结晶速度有影响
➢ 主要包括: 结晶温度外力, 溶剂, 杂质分子量
不过绝大多数处理非等温结晶动力学的方法或理论是在等温结晶动力学的基础上发展演变来的。
※ 等温结晶动力学 (Isothermal)
※ 非等温结晶动力学 (Non-isothermal)
结晶速度与测量方法
CHANGZHOU UNIVERSITY
➢ 结晶动力学主要研究聚合物的结晶速度（Rate of Crystallization), 分析其结晶过程
➢ 生长过程: 涉及分子链向晶核扩散与规整堆砌; 温度越低, 分子链(链段)的活动能力越小, 生长速度越慢
➢ 总结晶速度: 在Tg~Tm之间可以结晶, 但结晶速度在低温时受生长过程控制, 在高温时受成核过程控制, 存在一个最大结晶速度温度
等温结晶动力学
CHANGZHOU UNIVERSITY
测试方法
CHANGZHOU UNIVERSITY
在高纯氮气保护下，氮气流量为 50ml/min，样品重量为2 mg－6mg。将样品以20℃/min的速度加热至熔点以上20度左右后，恒温10min，以便消除样品的热历史和受力历史。然后以100℃/min的速度迅速降至某一设定的结晶温度Tc，记录所有 DSC曲线。
CHANGZHOU UNIVERSITY
研究目的：
为高分子加工过程提供理论依据，而高分子材料的实际生产过程（如挤出（Extrusion)、注射（Injection)、模压（Molding)等成型过程）常常是在动态、非等温条件下进行并完成的，因此定量地研究其非等温结晶动力学过程对选择合适的加工成型条件、制备性能良好的高分子材料或制品具有十分重要的现实意义。

化工专业英语词汇汇总

reaction kinetics 反应动力学reactant反应物purify精制提纯recycle循环回收unconverted reactant未转化的反应物chemical reactor transfer of heat, evaporation, crystallization 结晶drying干燥screening筛选，浮选chemical reaction 化学反应cracking of petroleum 石油裂解catalyst催化剂，reaction zone 反应区conservation of mass and energy 能量与质量守衡定律technical advance 技术进步efficiency improvement 效率提高reaction 反应separation 分离heat exchange 热交换reactive distillation 反应精馏capital expenditure 基建投资setup装置capital outlay 费用，成本，基建投资yield产率，收率reaction byproduct 反应副产物equilibrium constant 平衡常数waste废物feedstock进料，原料product产物，产品percent conversion百分比转化率ether乙醚gasoline 汽油oxygenate content 氧含量catalyst催化剂reactant反应物inert惰性物，不参加反应的物质reactive distillation 反应精馏energy saving节约能量energy efficiency 能量效率heat-sensitive material 热敏性物质pharmaceutical 制药foodstuff 食品gas diffusivity气体扩散性，气体扩散系数gas adsorption 吸收；absorption：吸附specialty chemical特殊化学品，特种化学品batch间歇的；continuous：连续的micro-reactor微型反应器hydrogen and methane oxidation氢气和甲烷氧化反应ethylene epoxidation乙烯环氧化反应phosgene synthesis 光气合成. commercial proportions 商业规模replication 复制sensor传感器，探头separation of solids 固体分离suspension 悬浮液porous medium 多孔介质filtration 过滤medium介质filter过滤器trap收集，捕集Buchner funnel 布氏漏斗Vacuum真空conical funnel 锥形漏斗filter paper 滤名氏area面积filter cake 滤饼factor因数，因子，系数，比例viscosity 黏度density 密度corrosive property 腐蚀性particle size 颗粒尺寸shape形状size distribution 粒度分布packing characteristics 填充性质concentration 浓度filtrate 滤液feed liquor 进料液pretreatment 预处理latent heat 潜热resistance 阻力surface layer 表面层filtering medium 过滤介质drop in pressure 压降filtering surface 过滤表面filter cake 滤饼cake filtration 饼层过滤deep bed filtration 深层过滤depth深度law定律net flow净流量conduction 传导convection 对流radiation 辐射temperature gradient 温度梯度metallic solid 金属固体thermal conduction 热传导motion of unbound electrons 自由电子的运动electrical conductivity 导电性thermal conductivity 导热性poor conductor of electricity 不良导电体transport of momentum 动量传递the random motion of molecules 分子无规则运动brick wall 墙壁furnace火炉，燃烧器metal wall of a tube 金属管壁macroscopic particle 宏观的粒子control volume 控制体enthalpy 焓macroscopic phenomenon 宏观现象forces of friction 摩擦力fluid mechanics 流体力学flux （通量，流通量）of enthalpy 焓通量eddy尾流，涡流turbulent flow 湍流natural and forced convection自然对流和强制对流buoyancy force 浮力temperature gradient 温度梯度electromagnetic wave 电磁波fused quartz熔化的石英reflect 反射，［肝住戊由门:折射matte无光泽的，无光的temperature level 温度高低inter-phase mass transfer界相际间质量传递rate of diffusion 扩散速率acetone 丙酮dissolve 溶解ammonia 氨ammonia-air mixture 氨气-水混合物physical process 物理过程oxides of nitrogen 氮氧化物nitric acid 不硝酸carbon dioxide 二氧化碳sodium hydroxide 氢氧化钠actualrate of absorption 实际吸收速率two-film theory 双膜理论concentration difference 浓度差in the vicinity of在…附近，靠近..,大约…，在…左右molecular diffusion 分子扩散laminar sub-layer 层流底层resistance阻力，阻止boundary layer 边界层Fick' s Law费克定律is proportional to 与…成比例concentration gradient 浓度梯度plate tower 板式塔installation 装置feed 进料bottom底部，塔底solvent 溶剂top顶部，塔顶partial vaporization 部分汽化boiling point 沸点equimolecular counter-diffusion 等分子反向扩散ideal system理想系统ratio of A to B A 与B 的比值with the result that：由于的缘故，鉴于的结果tray塔板packed tower 填料塔bubble-cap tower 泡罩塔spray chamber 喷淋室maintenance expense 维修费foundation 基石出tower shell 塔体packing material 填料pump 泵blower风机accessory heater附属加热器cooler冷却器heat exchanger 换热器solvent-recovery system 溶剂回收系统operating cost 操作费用power动力circulating gas 循环气labor劳动力steam蒸汽regenerate 再生cooling water 冷却水solvent make-up补充溶剂optimum最优的unabsorbed component 未吸收组分purity 纯度volatility 挥发性vapor pressure 蒸汽压liquid mixture液体混合物condense凝缩，冷凝binary distillation 双组分精馏multi-component distillation 多组分精馏stage-type distillation column 级板式精馏塔mount安装，固定conduit导流管）,downcomer降液管gravity 重力weir溢流堰vapor-liquid contacting device 汽液接触装置valve tray浮阀塔板reboiler 再沸器vaporization 汽化condensate冷凝液，凝缩液overhead vapor 塔顶汽体condenser冷凝器i feed tray进料板base塔底，基础bottoms product 塔底产品condensation 冷凝stripping section汽提段，提馏段distillate section 精馏段total condense 全凝器distillate product塔顶馏出产品reflux回流thermodynamic equilibrium 热力学平衡solution 溶液fractional crystallization 分步结晶solubility，溶解度，溶解性soluble可溶解的solvent溶剂employ采纳，利用miscible可混合的，可溶的，可搅拌的mechanical separation 机械分离）liquid-liquid extraction 液液萃取aromatic芳香烃的paraffin石蜡，链烷烃lubricating oil 润滑油decompose分解，离解，还原，腐烂penicillin 青霉素streptomycin （链霉素）precipitation 沉淀，沉析ethyl alcohol 乙醇）extract萃取液heat requirement 热负荷solute溶质extract phase 萃取相baffle-plate折流挡板，缓冲挡板settling tank 沉降槽centrifuge离心.离心机，离心分离emulsifying agent 孚L化剂Idensity difference 密度差raffinate萃余液extract萃取液drying of Solids 固体干燥process material过程物料（相对最终产品而言的）organic有机的，有机物的benzene 苯humidity 湿度moisture content 湿含量drying rate干燥速率critical moisture content 临界湿湿含量falling-rate 降速concave （凸的，凸面）or convex （凹的，凹面）approximate to：接近，趋近straight line：直线constant-rate drying period 恒速干燥阶段convection drying 对流干燥drying gas干燥气体falling-rate period降速干燥阶段mean value平均值vacuum drying 真空干燥discolor变色，脱色sublime 升华freeze drying冷冻干燥adiabatic绝热的，不传热的pressure gradientperpendicular to：与----垂直counter-current 逆流per unit area单位面积water-cooling tower 水冷塔sensible heat（sensible heat：显热）water droplet 水珠，水滴quantitative relation 定量关系thermal diffusion 热扩散at right angles to 与…成直角，与…垂直by virtue of由于，根据，凭借于molecular transfer 分子传递balance抵消，平衡drag forces 曳力a function of …的函数of the same order具有同一数量级eddy diffusion 涡流扩散is almost inversely proportional to 几乎与•一成反比Reynolds number 雷诺准数fully developed turbulent flow 充分发展湍流coefficient 系数In principle从原理而言exothermic （放热的，endothermic 吸热的,adiabatic 绝热的）triple bond 三健，三价nitrogen oxides 氮氧化物compound化合物conversion转化，转化率protein蛋白质compress 压缩reaction yield 反应产率reaction speed 反应速度one-pass （单程）reactor energy input 能量输入maximum最大的near toequilibrium 接近平衡output产出，输出，产量fertilizer 化肥urea尿素ammonium nitrate 硝酸铵ammonium phosphate 磷酸铵ammonium sulfate 硫酸铵diammonium hydrogen phosphate 磷酸二氢铵ash纯碱pyridine而砒啶polymers聚合物nylon尼龙acrylics丙烯酸树脂via经，由，通过，借助于hydrogen cyanide 氰化氢nitric acid 不硝酸bulk explosive 集装炸药crude oil 原油natural gas 天然气bitumen 沥青fossil fuel化石燃料seepage渗出物asphalt 沥青oil drilling 采油gasoline 汽油paint涂料plastic 塑料synthetic rubber 合成橡胶fiber纤维soap肥皂cleansing agent 清洗剂wax石蜡explosive 炸药oil shale油页岩deposit沉积物aquatic plant水生植物sedimentary rock 沉积岩sandstone 砂岩siltstone 泥岩tar sand沥青石chain-shaped 链状的methane 甲烷paraffin石蜡，烷烃ring-shaped （环状的）hydrocarbon naphthene 环烷烃naphtha石脑油tarry柏油的，焦油的，焦油状的asphaltene 沥青油impurity 杂质pollutant污染物combustion 燃烧capillarity毛细现象，毛细管力viscous resistance 粘性阻力barrel桶（国际原油计量单位）tanker 油轮kerosene 煤油heavy gas oil重瓦斯油reforming 重整cracking 裂化octane number of gasoline 汽油辛烷值branched-chain （带支链的）materials science 材料科学mechanical, thermal, chemical, electric, magnetic, and optical behavior.（机械性能、热学性能、化学性能、电学性能、磁性能、光学性能）Amalgam汞齐，水银；混合物，交叉solid state physics 固体物理学metallurgy冶金学，冶金术magnet磁铁，有吸引力的人或物insulation 绝缘catalytic cracking 催化裂化structural steels 结构钢computer microchip 计算机芯片Aerospace 航空Telecommunication 电信information processing 信息处理nuclear power 核能energy conversion 能量转化internal structure 内部结构defect structure 结构缺陷crystal flaw晶体瑕疵vacant atomic site 原子空位dislocation 错位precipitate 沉淀物semiconductor 半导体mechanical disturbance 机械扰动ductility延展性brittleness 脆性spinning electrons 旋转电子amorphous非定型的，非晶型的，非结晶的，玻璃状的;无一定目的的，乱七八糟chemical process safety 化工过程安全exotic chemistry 奇异化学hydrodynamic model 水力学模型two-phase flow 两相流dispersion model 分散模型toxic有毒的release释放，排放probability of failure 失效概率accident prevention 事故预防hard hat安全帽safety shoe 防护鞋rules and regulations 规章制度loss prevention 损失预防hazard identification 危害辩识，technical evaluation 技术评估safety management support安全管理基础知识safety experience 安全经验technical competence 技术能力safety knowledge 安全知识design engineer 设计师cost engineer 造价师process engineering 过程工程plant layout工厂布局general service facilities 公用工程plant location 工厂选址close teamwork紧密的团队协作specialized group 专业组storage 仓库waste disposal 废物处理terminology术语，词汇accountant会计师，会计，出纳final-proposal 决议tangible return 有形回报Empirical model 经验模型process control （过程控制）first-principles基本原理，基本规则regression model 回归模型.operating condition 操作条件nonlinear-equation-solving technique 非线性方程求解技术process-simulation software packages 过程模拟软件包least-squares-regression 最小二乘法statistical technique 统计技术intensity强度，程度phenomenological model 现象模型model identification 模式识另Uneural network 神经网络a priori：先验的，既定的,不根据经验的，由原因推出结果的，演绎的,直觉的process data historian：过程数据历史编撰师qualitative 定性的quantitative precision 定量的精确high-fidelity 高保真的computationally intensive 计算量大的mathematical expression steady-state model 稳态模型bioengineering 生物工程artificial 人工的hearing aid 助听器artificial limb 假肢supportive or substitute organ 辅助或替代器官biosynthesis生物合成life scientist生命科学家agricultural engineer 农艺师fermentation 发酵civil engineer 土木工程师sanitation 卫生physiologists 生理学criteria 指标human medicine 人体医学medical electronics 医疗电子medical instrumentation 医疗器械blood-flow dynamics血液流动动力学prosthetics假肢器官学biomechanics生物力学surgeon外科医生replacement organ 器官移植physiologist生理学家counterpart对应物，配对物psychology 心理学self-taught 自学barrier障碍物medical engineering医学工程，医疗工程health care 保健diagnostic application of computers 计算机诊断agricultural engineering 农业工程biological production 生物制品生产bionics （仿生学）human-factors engineering 人类与环境工程environmental health engineering 环境健康工程environmentally benign processing 环境友好力口工commodity or specialty通用商品或特殊化学品styrene苯乙烯ibuprofen异丁苯丙酸the Chemical Manufacturers Association 化工生产协会as a whole整体而言emission释放物，排放物voluntary自愿的，无偿的，义务的；有意的，随意的；民办的in the absence of 无---存在deactivate 失活bulk chemical大宗化工产品Fine chemical精细化工Pharmaceutical 制药segment段，片，区间，部门，部分；弓形，圆缺；分割，切断tonnage吨位，吨数，吨产量inorganic salt 无机盐hydroquinone 对苯二酚demonstrate论证，证明，证实；说明，表明，显示forefront最前线，最前沿Lewis acid不可再生的路易斯酸anhydrous无水的phaseout 消除HF alkylation氰氟酸烷基化catalytic oxidation 催化氧化governmental regulation 政府规定pharmaceutical intermediate 药物中间体stereoselective立体选择性的ketone 酮functional group 官能团detrimental 有害的chlorofluorocarbon二氯二氟化碳，氟里昂carbon tetrachloride 四氯化碳straightforward 简单明了的coordinating ligand配合体，向心配合体kilogram 千克thermal stability 热稳定性devastate破坏，蹂躏outline描绘，勾勒membrane technology 膜技术production line 生产线dairy牛奶water purification 水净化ifetime 寿命membrane module 膜组件durability耐久性，寿命，使用期限，强度chemical additive 添加剂end-of-pipe solution 最终方案closed system封闭系统substitute取代，替代technical challenge技术挑战，技术困难wastewater treatment 污水处理fouling污垢，发泡surface treatment 表面处理applied Chemistry 应用化学nomenclature of chemical compound 化学化合物的命名法descriptive描述性的refix前缀alkane烷烃family 族carbon skeleton 碳骨架chain 链Latin or Greek stem拉丁或者希腊词根suffix后缀constitute取代物，取代基homologous series 同系物branched chain 支链烷烃parent母链，主链derivative 衍生物substituent 取代基locant位次，位标replicating prefix 重复前缀词Gas and Liquid Chromatography气相色谱与液相色谱analytical chemistry 分析化学moving gas stream 移动的气流heats of solution and vaporization 溶解热和汽化热activity coefficient 活度系数counteract 抵消milliliter 毫升essential oil 香精油test mixture测试混合物sample样品helium 氦argon 氩carrier 载体injection 注射stationary nonvolatile phase 静止的不挥发相detector检测器fraction collector 馏分收集器columnar liquid chromatography 柱状液相色谱仪retention volume 保留体积retention times 保留时间high-performance 高性能mobile phase 移动相high-efficiency 高效的analyte分析物plane chromatography 薄层色谱capillary action毛细管作用assay分析化验fluorescence荧光色，荧光retardation factor保留因子，延迟因子。

草酸钙的结晶动力学及不同种类羧酸盐的影响

草酸钙的结晶动力学及不同种类羧酸盐的影响李君君;杨锦;夏志月;欧阳健明【摘要】通过检测体系中游离Ca2+离子浓度及草酸钙(CaOxa)的粒径随时间的变化,研究了CaOxa的结晶动力学及3种羧酸盐对CaOxa结晶动力学的影响,这些羧酸盐为:一元羧酸盐甘氨酸钠(NaGlu)、二元羧酸盐酒石酸钠(Na2Tart)和三元羧酸盐柠檬酸三钠(Na3Cit).在生理盐水中CaOxa的结晶动力学方程为r=kc3.3±0.36,平均反应速率常数(-k)为(3.1±1.8)×109;3种抑制剂对k的影响程度从大到小为:Na3Cit＞Na2Tart＞NaGlu,但其平均反应级数(-α)相差不大,-α=3.2±0.1.Na3Cit 、Na2Tart可抑制CaOxa晶体的生长和聚集过程,是潜在的肾结石抑制剂.%The kinetics of calcium oxalate (CaOxa) crystallization and the effect of three carboxylates were studied by determining the changes of free Ca2+ ions concentration and the size of CaOxa crystallites with the reaction time. These carboxylates were monocarboxylic acid salt (NaGlu), dicarboxylie-acid salt (Na2Tart), and tricarboxylic acid salt (NajCit), respectively. The dynamics equations of calcium oxalate crystallization in normal saline was r=Ac33±0.3, t he average reaction rate constant (k) was (3.1±1.8)×l09. The effect of three inhibitors on k values was in the order from large to small: Na3Cit>Na2Tart>NaGlu>blank. However, there is little difference for the average reaction order (a) value and α =3.2 ±0.1. Since Na3Cit and Na3Tart can inhibit the growth and aggregation of CaOxa crystals, they may be potential inhibitors for formation of kidney stones.【期刊名称】《无机化学学报》【年(卷),期】2012(028)006【总页数】8页(P1091-1098)【关键词】草酸钙;结晶动力学;羧酸盐;反应级数;ξ电位【作者】李君君;杨锦;夏志月;欧阳健明【作者单位】广东药学院药科学院,广州510006;暨南大学生物矿化与结石病防治研究所,广州 510632;暨南大学生物矿化与结石病防治研究所,广州 510632;暨南大学生物矿化与结石病防治研究所,广州 510632;暨南大学生物矿化与结石病防治研究所,广州 510632【正文语种】中文【中图分类】O614.23+1;O643.13+2;O743+3肾结石是人体内的病理矿化所致，其主要组分为草酸钙(CaOxa)。

The kinetics of desilication of synthetic spent Bayer liquor and sodalite crystal growth

Colloids and SurfacesA:Physicochemical and Engineering Aspects147(1999)283–295The kinetics of desilication of synthetic spent Bayer liquor andsodalite crystal growthM.C.Barnes,J.Addai-Mensah*,A.R.GersonIan Wark Research Institute,Uni6ersity of South Australia,The Le6els,Adelaide5095,AustraliaReceived30October1997;accepted15May1998AbstractThe kinetics of desilication of synthetic,sodium aluminosilicate solution(spent Bayer liquor)and growth of sodalite crystals have been studied under isothermal,batch crystallization conditions close to those prevailing in Bayer process heat exchangers.The desilication rate of the liquor via the formation and growth of sodalite scale on steel substrates was found to be independent of agitation rate.With sodalite seeding,the desilication rate was observed to increase dramatically due to seed crystal growth with the suppression of scale formation.An activation energy of30kJ mol−1 and a second order dependence of the desilication rate on relative supersaturation of SiO2were obtained for sodalite crystal growth.©1999Elsevier Science B.V.All rights reserved.Keywords:Desilication kinetics;Sodalite crystals;Sodium aluminosilicate scale;Spent Bayer liquor1.IntroductionThe presence of dissolved SiO2in sodium alumi-nate solutions,used for gibbsite precipitation dur-ing the Bayer process,causes an unwanted sodium aluminosilicate scale formation in alumina reﬁner-ies[1].The SiO2impurities originate from kaolin-ite and quartz present in the bauxite ores.The ore is digested at elevated temperatures(]150°C) with recycled sodium hydroxide solution to extract alumina hydrates(gibbsite and boehmite).Subse-quent to the precipitation of gibbsite at ca70°C the resulting liquor,which typically contains 0.6g dm−3SiO2,is recycled via a series of heat exchangers and evaporators for further bauxite digestion.Reheating the liquor from70to240°C after gibbsite precipitation results in the formation of sodium aluminosilicate scale due to the in-creased SiO2supersaturation caused by the low alumina content of the solution[1].The formation of sodium aluminosilicate scale in the heat exchangers is a costly phenomenon which results in a pressure drop,ﬂow restriction and energy consumption as well as serious foul-ing.Several studies have been carried out to un-derstand the mechanism of the formation of sodium aluminosilicate scale and desilication ki-netics of spent liquor[2–14].Most of these studies[3–5,7–10,13]investigated sodium alu-minosilicate precipitation kinetics in the presence of bauxite,red mud or sodium aluminosili-*Corresponding author.Tel:+61883023683;fax:+61883023673;e-mail:jonas.addai-mensah@.au0927-7757/99/$-see front matter©1999Elsevier Science B.V.All rights reserved. PII S0927-7757(98)00570-6M.C.Barnes et al./Colloids and Surfaces A:Physicochem.Eng.Aspects147(1999)283–295 284cate and their mixtures of complex mineralogyor ambiguously deﬁned crystallographic charac-teristics.Recent studies[14,19,20]carried out onthe mechanism of sodium aluminosilicate scalinghave shown that in heat exchangers,two sodiumaluminosilicate phases,sodalite and cancrinite,are formed from unseeded liquors.Sodalite hasbeen reported to be the less thermodynamicallystable phase and always precipitatesﬁrst.It thentransforms to cancrinite,at a rate which in-creases with increasing temperature.The authorshave observed that the time for transformationvaries from\350h at relatively low tempera-tures(B160°C)to ca4h at high temperatures(\240°C).Sodalite is cubic with space group P43n andhas AB–BA–AB layer packing.Cancrinite ishexagonal belonging to the space group P63withAB–AB type layer packing[15–18].The stoi-chiometry of the two dimorphs may be generi-cally written as Na6[AlSiO4]62NaX·n H2O,where X can be1/2CO2−3,1/2SO2−4,Cl−,OH−and NO−3[15–18].The SiO2equilibrium solubility of sodalite and cancrinite in spent Bayer liquors(solutions from which gibbsite has been precipitated)are signiﬁcantly different with that of the latter being lower[19,26].Hence,the solubility of SiO2may change from that relative to sodalite to that relative to cancrinite,as sig-niﬁcant phase transformation from sodalite to cancrinite occurs during aging of the crystalline products in situ.This may lead to a signiﬁcant change in the supersaturation of SiO2,the mech-anism of precipitation and hence,the desilication kinetics.Recent studies[14,21,27,28]have shown that the SiO2supersaturation which prevails in spent liquors is insufﬁcient to cause nucleation in the bulk solution.The desilication reaction which leads to sodalite scale formation was reported to be substrate mediated[14].It has been reported that seeding with sodalite or cancrinite greatly accelerates the desilication reaction rate[20]. However to date,the complete studies of spent liquor desilication kinetics for the sodalite or cancrinite seeded precipitation system have not yet been carried out.Only one desilication kinet-ics study which clearly speciﬁed sodalite as the seed crystals used has so far been reported in the literature[9].In other desilication kinetics studies[3–5,9–11,13]in which synthetic sodium aluminosilicate seeds were used,the crystallo-graphic phases and their equilibrium solubilities involved were not fully determined.When baux-ite,red mud or plant scale deposit was used as the seeding material in other studies[4,5,8,11], the mineralogical composition of the products and the effect of the impurities on the desilica-tion reaction rate were not reported.As a large proportion of reactive SiO2in bauxite is in the form of kaolin,it may react with the NaOH in the solution to change liquor composition and/ or act as a seed to promote desilication and additional reactions to seed growth[2,4,9,10]. Seeding with bauxite may also increase the solu-tion alumina concentration and thus change the liquor composition and driving force[1].Fur-thermore in some of the investigations,the sur-face areas of the seed and products were not taken into account during the analysis and cor-relation of the kinetic data[3,8,13].The above variations in the experimental methodologies used by the various investigators have resulted in a lot of uncertainties to be associated with the reported desilication mechanisms and kinetic parameters.To date it has not been clearly es-tablished whether the reported kinetics of spent liquor desilication were predominantly due to a nucleation mechanism and/or growth mechanism of a known sodium aluminosilicate phase.Con-sequently there has been a great deal of varia-tion in the kinetic parameters reported in the literature for the desilication of spent Bayer liquor.Activation energies in the range of38–92kJ mol−1and order of desilication reactions between1and3have been reported[3–5,8–11,13].The main aim of the present work was to determine the kinetics of desilication of self-nu-cleating and sodalite-seeded,synthetic spent Bayer liquors under conditions of which sodalite precipitation or crystal growth occurred.This was achieved by investigating the effect of SiO2 supersaturation,temperature,agitation rate and sodalite seeding on the rate of SiO2desupersatu-ration under isothermal,batch crystallization of sodalite crystals.M.C.Barnes et al./Colloids and Surfaces A:Physicochem.Eng.Aspects147(1999)283–2952852.MethodologyThe following chemicals,experimental proce-dures and analytical techniques were used.Syn-thetic spent Bayer liquors were prepared from: 179.9g dm−3gibbsite(C-31Hydrate,Alcoa Ar-kansas,U.S.A.)and216.7g dm−3sodium hy-droxide(Ajax Chemicals,Australia,97.5%pure, 2.5%Na2CO3).51.7g dm−3anhydrous sodium carbonate(BDH,Merck,Kilsyth,Australia, Analar,99.9%)and Milli-Q water(surface ten-sion of72.8mN m−1at20°C and a speciﬁc conductivity B0.5m S).To prepare a sodium aluminate solution,the required weight of sodium hydroxide was added to25%of theﬁnal volume of water in a stainless steel beaker.Af-ter complete dissolution,a known weight of alu-minium hydroxide was added.The mixture was then heated to105°C.After complete dissolu-tion,a known weight of sodium carbonate was dissolved in0.25dm−3of water and added to the sodium aluminate solution.Water was added to make up1litre of liquor.In order to bring the solution to the required experimental concentrations of154.8g dm−3 NaOH,128.5g dm−3Al(OH)3and40g dm−3 Na2CO3,0.25dm3of the liquor was placed in a 0.6dm3stainless steel autoclave operating at a 400rpm agitation rate at a constant tempera-ture.With unseeded experiments,0.10dm3of a solution containing0.741g of sodium metasili-cate(Ajax Chemicals,27.8–29.2%SiO2,28.1% Na2O,42–43%H2O by weight)was added to give aﬁnal volume of0.35dm3.With seeded experiments both a0.05dm3solution containing 0.741g of sodium metasilicate and0.05dm3of water containing0.645g of sodalite seed were added to the liquor sequentially once it had reached the required experimental temperature. The addition of the sodium metasilicate solution and seed slurry was carried out via a vertical, 0.1dm−3,high pressure steel tube whose bot-tom end is attached to the autoclave via a one-way valve.Discharge of the tube contents into the autoclave is achieved by metering com-pressed N2gas at a pressure exceeding the inter-nal pressure of the autoclave through the top end of the tube.As soon as the temperature required was achieved(typically within2min), the experimental time was set as zero.Each experiment was replicated at least three times.Samples were taken periodically during desilication.The solutions SiO2concentration was analysed by inductively coupled plasma (ICP,Spectro Analytical Instruments,Spectro SIM-SEQ ICP-OES).The error in SiO2analysis was determined experimentally to be B5%by both multiple ICP analysis of the same ICP so-lution and analysis of multiple preparations of ICP solutions prepared from the same replicate liquor sample.The errors given in the present work have been calculated on the basis of95% conﬁdence interval.In the seeded experiments,pure sodalite crys-tals were used as a seed.The seed was synthe-sized by adding75g of kaolin to a300g dm−3 sodium hydroxide solution and heating the mix-ture in an autoclave at160°C for12h.The re-sulting product was identiﬁed as sodalite with a unit cell parameter of8.85A˚by powder X-ray diffraction(XRD)analysis[17].The analysis also conﬁrmed that the sodalite seed crystals,as synthesized above,were not contaminated by aluminium trihydroxide(e.g.gibbsite).The crys-tals were washed in milli-Q water until they were neutral to litmus and the coarser fraction (1–40m m diameter)were allowed to settle for decantation of the unwantedﬁne crystals(B 1m m).The seed crystals were in the size range of1–40m m and had a BET(Brunauer,Emmett and Teller,[29])surface area of16.3m2g−1.A316stainless steel,high-pressure,Parr auto-claveﬁtted with an external heater and an inter-nal cooling system was used as the batch crystallizer.The vessel wasﬁtted with a central four blade,45°-pitch,two-tier impeller which provided constant agitation to within92rpm. Two,316stainless steel strips of dimensions 10mm×6mm were attached to the shaft of the impeller to provide scaling substrates for scan-ning electron microscopy(SEM)and X-ray powder diffraction analysis.The control of the heating rate,the agitation and the temperature of the autoclave was achieved through an auto-matic proportional,integral and derivative(PID) control system.M.C.Barnes et al./Colloids and Surfaces A:Physicochem.Eng.Aspects147(1999)283–295 286To prevent the solution from undergoing nu-cleate orﬁlm boiling,the autoclave was pre-pressurized,by using N2gas,to a pressure 100kPa higher than the estimated saturated va-pour pressure of the solution determined accord-ing to the experimental temperature and solution concentration.This also ensured that no signiﬁ-cant differences existed between the temperatures of the vessel surface,the bulk solution and satu-ration temperatures of the solution or suspen-sion to cause signiﬁcant solution water loss by vaporization.To ascertain whether or not sodium alumi-nosilicate scale formation occurred by nucleation in the bulk solution followed by adsorption of nuclei at the substrate surface or by a direct nucleation at the surface of the substrate,solu-tion samples were periodically removed and sub-jected to light scattering analysis(Brice Phoenix, Universal Light Scattering Photometer,Virtis Co.Gardiner,NY,USA).Light scattering analyses for sodalite seeded suspensions were carried out onﬁltrates obtained byﬁltering the sampled solution through a0.20m m membrane, to determine whether there were colloidal parti-cles present as a result of secondary nucleation. Dissymmetry ratios(DR),deﬁned as the ratio of intensity(I)of monochromatic light(u= 540nm)scattered at60°to that scattered at 120°(i.e.DR=I60°/I120°),were measured.DR= 1if there are no signiﬁcant number of particles in suspension of diameter\30nm,otherwise DR\1.All crystal samples were analysed using a par-ticle sizer(Malvern Mastersizer,Malvern,Eng-land),N2BET analysis(Coulter Omnisorp100, Hialeah,FL,USA),SEM(15kV on carbon coated samples by using a high resolutionﬁeld emission Cam Scan CS44FF,Cambridge,Eng-land)and XRD(Phillips PW1130/90).These lat-ter two techniques were used for crystal imaging and crystalline phase analysis,respectively.Parti-cle size analysis of product crystals were carried out on wet slurry samples subsequent toﬁltra-tion and washing.XRD patterns were collected on powdered samples in u/2u scanning mode us-ing Cu K a radiation(u=1.5418A˚).The scan speed was1°min−1between10°and70°2u.3.Results3.1.Isothermal,batch desilication kinetics3.1.1.The effect of supersaturationThe kinetic behaviour of unseeded spent liquors was investigated over4hours at three initial SiO2 supersaturation levels with solutions initially con-taining0.4,0.6and0.8g dm−3SiO2(with all other variables kept the same),in order to gain further understanding of the desilication mecha-nism and to establish the basis for comparison with seeded solutions.For analysis of the data, the driving force for desilication/sodalite precipi-tation has been expressed as a function of relative supersaturation of SiO2deﬁned as:|=C−C eqC eqwhere C and C eq are the respective solution SiO2 concentration at any time and at equilibrium.As sodalite has been observed to precipitateﬁrst,that is,prior to cancrinite formation,in present and previous studies[1,2,7,14,27],the supersaturation of the unseeded solutions has been deﬁned in terms of the sodalite equilibrium SiO2concentra-tions[26].Fig.1depicts typical SiO2desupersaturation curves of unseeded desilication process obtained for the three solutions at160°C.A very smallFig.1.The variation of relative supersaturation of SiO2with time during unseeded,batch desilication of spent sodium aluminate liquors at160°C:",0.4g dm−3; ,0.6g dm−3; and ,0.8g dm−3initial SiO2concentrations.M.C.Barnes et al./Colloids and Surfaces A:Physicochem.Eng.Aspects147(1999)283–295287 decrease in solution SiO2concentration occurredover4h at0.4and0.6g dm−3initial SiO2con-centrations.However,at0.8g dm−3SiO2concen-tration,desilication occurred rapidly after1h andcaused the relative SiO2supersaturation in theproduct solution to be lower than that obtainedfor the0.6g dm−3SiO2after4h.Similar obser-vations of increasing rate of desilication with in-creasing SiO2concentration were made at othertemperatures(90–220°C).The results suggest thatunder batch conditions,negligible desilication oc-curred over a4h period from supersaturated so-lutions which contained SiO2at concentrations inthe range of those experienced in plant spent liquors(0.3–0.6g dm−3SiO2).Thisﬁnding agrees with other literature reports for similar solutions [14,20].However,it must be noted that plant spent liquors have lower SiO2solubilities than synthetic spent liquors and may thus be slightly more supersaturated in general.All the solutions,including those from the ex-periments which contained0.8g dm−3SiO2ini-tially,sampled over the4h period were found to be optically clear with no crystal content upon ﬁltration through a0.20m m membrane.Light scattering analysis conﬁrmed that theﬁltrate did not contain any signiﬁcant number of colloidal size particles(of diameter\30nm).However, when a detectable decrease in SiO2concentration occurred,a layer of scale was always formed on the autoclave steel wall,regardless of the tempera-ture used.At temperatures up to220°C,XRD analysis identiﬁed the scale to be sodalite.3.1.2.The effect of temperatureFig.2shows the variation of relative supersatu-ration of SiO2as a function of time for solutions initially containing0.6g dm−3SiO2at the tem-perature range of90–240°C.The results show that between90and160°C,there was no signiﬁ-cant decrease in SiO2concentration over4h.At higher temperatures(\160°C),a sharp increase in the desilication rate was observed,although the initial relative supersaturation were only ca50–75%of those in the90–160°C temperature range. This observation suggests that at temperatures \160°C,increasing the temperature has a more profound effect on the desilication reaction than Fig.2.The relative supersaturation of SiO2as a function of time during unseeded,batch desilication of spent sodium aluminate liquors at90–240°C:",90°C; ,120°C; , 140°C;×,160°C; ,180°C; ,220°C;+,240°C. increasing SiO2relative supersaturation.At220°C the desilication reaction approached sodalite-seeded SiO2equilibrium solubility within4h.De-silication reactions using sodalite seeding showed that the SiO2concentration at180and220°C were the same as that for unseeded experiments at the same temperatures after4h.At240°C,the sodalite seeded SiO2solubility was exceeded after 3h,as the desilication curve crossed the zero relative supersaturation line established with so-dalite equilibrium solubility(Fig.2).XRD analy-sis of the scale product at240°C indicated that an almost complete transformation from the sodalite to cancrinite phase had occurred.Thus the forma-tion of cancrinite which has a lower equilibrium SiO2solubility[20,26],resulted in theﬁnal SiO2 concentration lower than was expected for a so-dalite contain system.This sodalite to cancrinite phase transformation is known to be sodalite dissolution-mediated[27].Hence in the determina-tion of the true solubility at240°C without signiﬁ-cant cancrinite contamination,a very high seed charge ofﬁne sodalite crystals for a predomi-nantly sodalite-solution interfacial area as well as strong agitation may be used to approach equi-librium over a short time(B3h).This approach was used to measure the equilibrium solubility of sodalite in spent liquors at temperatures up to 240°C and is reported elsewhere[26].M.C.Barnes et al./Colloids and Surfaces A:Physicochem.Eng.Aspects147(1999)283–295 288SEM images and XRD analysis of the stainless steel substrate surface obtained from the unseeded desilication experiments after4h,indicated that when signiﬁcant desilication occurred at higher temperatures(\160°C,Fig.2),there was a con-comitant formation of sodalite scale(Fig.3).The extent of scale coverage and size of the crystals increased with increasing temperature as shown in Fig.3.The primary particles of the scale were observed to be pseudo-hexagonal,prismatic crys-tals formed by twinning at an angle about the [001]axis in a characteristic manner as to produce a‘‘cauliﬂower-like’’stacking.The observed mor-phology of the scale particles are notably differentFig.3.SEM photomicrographs of316stainless steel substrates used in isothermal batch desilication of unseeded,spent sodium aluminate liquors,before experiment(A)and at:(B)90–160°C;(C and D)180°C;and(E and F)220°C.Images C–F show sodalite crystals formed on the surface as scale.M.C.Barnes et al./Colloids and Surfaces A:Physicochem.Eng.Aspects147(1999)283–295289Fig.4.The variation of relative supersaturation of SiO2with time at different rates of agitation during batch desilication of unseeded spent sodium aluminate liquors at160°C;", 100rpm; ,400rpm;and ,700rpm agitation rates.out under similar solution composition and tem-perature conditions[21].It was reported that un-der continuous,laminar plugﬂow precipitation of sodalite scale on stainless steel substrates,the extent of scale formation was independent of the solutionﬂow velocity for Reynolds numbers in the range of100–400.The results indicate that there is no signiﬁcant limitation of volume diffu-sion imposed on the solution scale forming species during transport to the reaction sites for precipitation.3.1.4.The effect of seeding with sodaliteA seed charge of0.645g to give30m2of sur-face area per1dm3of spent liquor was used.The effect of seeding on the extent of spent liquor desilication over4h was investigated at90,120, 140,160,180and220°C.Rapid desilication of the spent liquor occurred,the extent increasing with increasing temperature(Fig.5Table1).For exam-ple,at the higher temperatures(180and220°C), the solution SiO2concentration decreased to within0.1g dm−3of the equilibrium solubilities after4h.In Table1,the solution SiO2concentra-tions observed at140and180°C,for both seeded and unseeded spent liquors are given for compari-sons.The data clearly demonstrate that both seeding and temperature had a marked effect on the rate of SiO2desupersaturation of the spent liquor.from that of the scale-forming,globular or poorly faceted sodalite crystals precipitated at similar steel surfaces from spent liquors of lower Al(OH)3/NaOH molar ratio at160°C[14,20].The morphology is also different from the poorly faceted/globular sodalite seed crystals precipitated from the bulk solution at160°C(Fig.8).The exact crystallographic cause of the variation in the sodalite crystal morphology and their orientation on the steel surface is as yet unknown.3.1.3.The effect of agitationDetermining whether the desilication reaction and its concomitant scaling process are volume diffusion controlled,chemical reaction controlled or a combination of both is crucial to the under-standing of the mechanism of scale formation. This was investigated by varying the rate of agita-tion to give turbulentﬂow at constant tempera-ture and constant initial SiO2supersaturation. The SiO2desupersaturation curves obtained under turbulentﬂow at agitation rates of100,400and 700rpm(Reynolds numbers:7000–35000)at 160°C were found to be substantially similar, within the limits of uncertainty of SiO2concentra-tion determination(Fig.4).The lack of inﬂuence of the agitation rate on the kinetics of desilication of the unseeded spent liquors at160°C agrees with theﬁndings of a recent desilication study carried Fig.5.SiO2relative supersaturation of sodalite-seeded(30m2 crystal dm−3),spent sodium aluminate liquors as a function of time at90–220°C:",90°C; ,120°C; ,140°C;×, 160°C;*,180°C;and ,220°C.M.C.Barnes et al./Colloids and Surfaces A:Physicochem.Eng.Aspects147(1999)283–295290Table1Comparisons of solution SiO2concentrations obtained at various times during unseeded and sodalite-seeded,isothermal,batch desilication of spent sodium aluminate liquors140°C Seeded(g dm−3)180°C Unseeded(g dm−3)Time(min)140°C Unseeded(g dm−3)180°C Seeded(g dm−3)0.590.600.600.600.560.440.540.43300.400.550.420.54600.420.441200.570.360.380.351800.560.320.330.380.320.57240The size distribution of sodalite seed crystals used in the present work ranged from1–40m m (Fig.7).Size analyses of representative product crystal samples were carried out.At agitation rates of up to450rpm,gross breakage of these sodalite crystals does not occur during desilication [5,19].Hence the detection of colloidal size parti-cles(B1m m)would suggest secondary nucleation occurred.DRs of 1.090.1were observed for solutions obtained byﬁltering the slurries periodi-cally removed from the crystallizer vessel through a0.2m m membrane.This indicated the absence of colloidal size crystals that might have been formed as a result of secondary nucleation in the bulk solution.X-ray powder diffraction analysis of the seed and the products(Fig.6)showed that they did not undergo any phase transformation to can-crinite during the4h experiments carried out at temperatures B220°C.At220°C,however,a small amount of cancrinite was formed as a result of phase transformation,indicated after4h by the appearance of the cancrinite101diffraction peak at19°2u.Thus the desilication of the liquor was concluded to proceed by sodalite precipitation. The results of the crystal number and size anal-ysis(Fig.7)showed that there was an overall increase in average size of the crystals but no increase in their number and with no signiﬁcant smaller size fraction present in the product up to 4h.Therefore,the desilication occurred through growth of the seed crystals.This observation was supported by SEM imaging as demonstrated by the photomicrographs of the product crystals from experiments at140°C(Fig.8).Although the crystals appear to be composed of agglomerates,it can be seen that the individual primary particles became larger during the course of precipitation with noﬁne particle generation[Fig.8(B,D and F)].Similar observations of crystal growth only (of seeds)were made from the crystal size analysis at other plementary particle sizing,light scattering,SEM analysis of seed and products all lead to the conclusion that the addi-tion of sodalite seeds did not promote secondary nucleation but only mass deposition or growth on parent crystals.The seed and product crystals’surface area analysis by BET showed that al-though the speciﬁc surface area of the product crystals decreased with time,their total surface area remained substantially the same.The individ-ual,total surface areas were used in the desilica-tion kinetics analysis described below.SEM imaging of stainless steel substrates used in the seeded experiments showed that there were Fig.6.X-ray powder diffraction patterns of sodalite seed and product crystals obtained from the seeded desilication of spent sodium aluminate liquors at140–220°C over4h.M.C.Barnes et al./Colloids and Surfaces A:Physicochem.Eng.Aspects147(1999)283–295291Fig.7.Typical cumulative number-size distribution of sodalite crystals obtained during seeded desilication of spent sodium aluminate liquor at140°C.crystal growth,respectively.In the absence of signiﬁcant nucleation of any kind(i.e.secondary or heterogeneous nucleation),Eq.(1)simply re-duces to the form below for pure crystal growth.−d|d t=Ak g|g(2) With no seeding,the rate of desilication was extremely slow at temperatures below180°C.This did not allow accurate determination of the mech-anisms(i.e.nucleation and/or growth)and kinet-ics of the unseeded desilication reaction.With seeding,the rate of desilication was found to be sufﬁciently fast at all temperatures to enable the measurement of reliable kinetic data.The results shown in the preceding section demonstrated that the desilication reaction proceeds by sodalite crys-tal growth.As a result,the kinetic data and parameters presented here have been evaluated for the sodalite crystal growth mechanism.By plotting log((1/A)(−d|/d t))against log(|),g is obtained as the slope and log(k g)as the y-inter-cept from linear regression analysis.A typical plot is shown in Fig.9for seeded desilications carried out at140,180and220°C which indicates that a very goodﬁt of the kinetics data to Eq.(2)can be obtained.The rate constant k g and the reaction order g were estimated at each separate temperature.The analysis gave a reaction order of2.039 0.06for the temperatures and relative supersatu-ration used in this investigation.Consequently the overall reaction order for sodalite crystal growth was approximated to 2.The value of2is in agreement with some of the values found in the literature[8–10,13,28],although the values of1 and3have also been reported by some investiga-tors[3,4,11].The effect of temperature on the desilication or growth kinetics of sodalite crystals was further analysed by expressing the rate con-stants k g as a function of temperature using the Arrhenius relationship of the form:k g=k o exp(−E a/RT)(3) where k o is the pre-exponential factor (min−1m−2),E a is the activation energy for so-dalite crystal growth(kJ mol−1),T is the temper-ature(K),R is the gas constant (8.314Jmol−1K−1).no noticeable sodalite crystals(secondary nuclei) formed as scale on the steel surface.However,a few seed crystals were occasionally found to ad-here to the surfaces in a manner similar to the surface shown in Fig.3(B).The mechanism of adherence,either by van der Waals and electrical double layer or other chemical forces,has not yet been determined.3.2.The kinetics of desilication of seeded solutions and growth of sodaliteFor isothermal batch desilication of the SiO2-supersaturated sodium aluminate liquor,the su-persaturation may be dissipated by nucleation and crystal growth mechanisms.The kinetics of the two mechanisms may be quantiﬁed by a power law relationship of the form:−d|d t=k n|n+Ak g|g(1)where|is the relative supersaturation,(C−C eq)/ C eq;k n is the rate constant for nucleation (min−1);n is the order of the nucleation reaction; k g is the growth rate constant(min−1m−2);g is the order of crystal growth reaction;and A is the total surface area of crystals(m2).Theﬁrst and second terms on the right-hand side of Eq.(1)correspond to nucleation and。

Fe-B非晶合金的等温晶化动力学研究

* 收稿日期:2021-03~03 基金资助：国家重点研发计划(2017YFB0703001,2017YFB0305100)；国家自然科学基金(51134011,51431008,51790481)；中央高校基本科研业务费专项资金(3102017jc01002)o 第一作者简介：马亚珠(1985-),女，西北工业大学博士研究生，主要研究方向为非晶及纳米晶等亚稳材料制备及稳定性, E-mail： 419256325@qq. com。通信作者简介：刘峰(1974 — )男，西北工业大学教授，主要研究方向为非平衡凝固理论与技术等，E-mail：lifeng@。
本文将通过DSC研究Fe85 B】5非晶合金在不同温度下的等温晶化动力学行为。结合X-射线衍射仪和透射电子显微镜，确定其等温晶化后的显微结构。用解析相变模型结合碰撞模式判断对所有实验数据进行拟合，明确该合金的等温晶化动力学。
1实验材料与分析方法
1. 1实验材料
本文的实验对象为Fe85 B：5非晶合金。在氩气保护下利用电磁感应熔炼纯铁和Fe-B中间合金制
得Fe85B“母合金。在下方有直径0. 8 mm喷嘴的坩埚中放入8 g母合金，置入超快速液淬装置中，在氩气保护下用8 kW功率加热使合金快速熔化，通过加压0. 03 MPa向坩埚中充入高纯氩气使得
高温熔体通过喷嘴连续流向以5 000 r • min-1转速旋转的冷却铜辐上，从而制备出约32 gm厚的非晶合金薄带。用X，pert Pro MRD型X射线衍射仪(X-Ray Diffractometer, XRD，Cu-Ka)对制备的薄带进行物相检测。薄带的化学成分用感应耦
了很多实验结果［1012］ o解析模型具有类似JMA 方程［913］的结构，但是在等温转变中生长指数"、有效激活能Q和指数前因子犓0是时间的函数。然而，在用解析相变模型对实验结果的拟合过程中，由于不同形核生长模式组合及参数选取的范围大，会增大计算的时间。因此，研究者提出了转变速率

反溶剂诱导结晶法英文

反溶剂诱导结晶法英文Antisolvent-Induced Crystallization: A Comprehensive Overview.Introduction:Antisolvent-induced crystallization (AIC) is a versatile technique widely employed in the pharmaceutical, chemical, and food industries to produce crystalline materials with tailored properties. This method involves introducing an antisolvent into a supersaturated solution of the target compound, triggering the nucleation and growth of crystals. AIC offers numerous advantages over other crystallization techniques, including enhanced control over crystal size, shape, and purity.Mechanism of AIC:The antisolvent, typically a non-solvent or a solvent with low solubility for the target compound, plays acrucial role in the AIC process. When added to a supersaturated solution, the antisolvent reduces the solubility of the solute, leading to the formation of a metastable zone. Within this zone, small crystal nuclei form and begin to grow. The antisolvent concentration, temperature, and solution composition influence the nucleation and growth kinetics, ultimately determining the characteristics of the final crystals.Advantages of AIC:AIC offers several advantages over conventional crystallization methods, including:Control over Crystal Morphology: AIC allows for the manipulation of crystal size, shape, and surface structure by varying process parameters such as antisolvent type, concentration, and temperature.Enhanced Purity: The antisolvent acts as a washing agent, removing impurities from the growing crystals and improving their purity.Scalability: AIC is a scalable process suitable for both small-scale laboratory experiments and large-scale industrial production.Energy Efficiency: Compared to other crystallization techniques, AIC often requires lower energy input due to reduced evaporation and milder operating conditions.Applications of AIC:AIC finds applications in a wide range of industries, including:Pharmaceuticals:Production of active pharmaceutical ingredients (APIs) with controlled bioavailability and dissolution rates.Development of drug delivery systems with specific release profiles.Chemicals:Synthesis of fine chemicals and specialty materials.Crystallization of inorganic compounds for electronic and optical applications.Food:Production of food additives and flavors.Crystallization of sugars and sweeteners.Process Parameters:The success of AIC depends on the careful optimization of several process parameters, including:Antisolvent Selection: The choice of antisolvent is crucial and depends on its solubility characteristics, miscibility with the solvent, and ability to promote nucleation.Antisolvent Concentration: The concentration of the antisolvent determines the degree of supersaturation andthe nucleation rate.Temperature: Temperature plays a significant role in crystal growth and morphology. Lower temperatures generally favor smaller crystal sizes.Mixing: Efficient mixing is essential for uniform distribution of the antisolvent and to preventagglomeration of crystals.Crystal Seeding: Seeding with pre-formed crystals can control nucleation and promote the growth of specificcrystal faces.Equipment for AIC:AIC can be carried out using various types of equipment, such as:Batch Crystallizers: Simple vessels where the antisolvent is added to a supersaturated solution.Continuous Crystallizers: Allow for continuous operation and better control over crystal growth.Fluidized Bed Crystallizers: Suspend crystals in a fluidized bed, facilitating efficient mass transfer and crystal growth.Challenges and Considerations:Despite its versatility, AIC also faces some challenges:Crystal Agglomeration: High supersaturation or insufficient mixing can lead to agglomeration, resulting in non-uniform crystal properties.Nucleation Control: Controlling the nucleation rate is crucial to obtain the desired crystal size and distribution.Solvent Selection: The choice of solvent andantisolvent combination must consider their solubility and stability under process conditions.Conclusion:Antisolvent-induced crystallization is a powerful technique that offers significant advantages for the production of crystalline materials with tailored properties. Its versatility, scalability, and ability to control crystal morphology and purity make AIC a valuable tool for various industries, including pharmaceuticals, chemicals, and food. Continued research and development in AIC aim to further optimize the process and expand its applications.。

多晶型与添加剂之经典文献3

Journal of Crystal Growth 235(2002)471–481Stabilization of a metastable polymorph of sulfamerazine bystructurally related additivesChong-Hui Gu a,c ,Koustuv Chatterjee a ,Victor Young Jr.b ,David J.W.Grant a,*aDepartment of Pharmaceutics,College of Pharmacy,University of Minnesota,Weaver-Densford Hall,308Harvard St.S.E.,Minneapolis,MN 55455-0343,USAbDepartment of Chemistry,University of Minnesota,207Pleasant St.S.E.,Minneapolis,MN 55455,USAcBristol-Myers Squibb Co.,1Squibb Drive,P.O.191,New Brunswick,NJ 08903,USAReceived 30April 2001;accepted 8October 2001Communicated by A.A.ChernovAbstractThe inﬂuence of structurally related additives,namely N4-acetylsulfamerazine (NSMZ),sulfadiazine (SD)or sulfamethazine (SM),on the rate of the solvent-mediated polymorphic transformation (I -II)of sulfamerazine in acetonitrile (ACN)at 241C was studie d.Thetransformation rateis controlle d by thecrystallization rateof themore stable Polymorph II.All three impurities exhibit inhibitory effects on the crystallization of Polymorph II and hence stabilize the metastable Polymorph I in ACN suspension.The rank order of the inhibitory effect (NSMZ b SD>SM)is thesameas therank orde r of thebinding e ne rgy of theimpurity mole culeto thesurfaceof thehost crystal.The relationship between the concentration of the impurity and the inhibitory effect was ﬁtted to various models and was found to be best described by a model based on the Langmuir adsorption isotherm.r 2002Published by Elsevier Science B.V.Keywords:Al.Adsorption;puter simulation;Al.Crystal structure;A1.Impurities;A1.Nucleation;A2.Growth from solutions1.IntroductionPolymorphs arecrystallinesolids with thesame chemical composition but with different arrange-ments and/or conformation of the molecules in a crystal lattice.The discovery and characterization of polymorphs areimportant in various ﬁe lds,because different polymorphs exhibit signiﬁcantlydifferent physicochemical properties.In the phar-maceutical ﬁeld,for example,the sudden appear-anceof a morestablepolymorph,that was not discovered at the early stage of pharmaceutical development,can cause loss of time and resources [1].Solvent-mediated polymorphic transformation is an efﬁcient method to prepare more stable polymorphs [2,3].Traceamounts of a structurally related impurity may exert signiﬁcant effects on thekine tics of dissolution [4]and crystallization [5],leading to changes in the polymorphic transformation rate in solution.Such effects may delay the discovery of a more stable polymorph.*Corresponding author.Tel.:+1-612-624-3956;fax:+1-612-625-0609.E-mail address:grant001@ (D.J.W.Grant).0022-0248/02/$-see front matter r 2002Published by Elsevier Science B.V.PII:S 0022-0248(01)01784-5On the other hand,the presence of an impurity or additivemay assist thepre paration of theme ta-stablepolymorph,which may othe rwiserapidly transform to themorestablepolymorph [6].To exploit the superior properties of a metastable polymorph,additives may be used to stabilize kinetically the metastable polymorph by inhibiting the formation of more stable polymorphs.There-fore,it is important to understand the effects of impurities or additives on the polymorphic trans-formation ratein solution.Thetransformation from theme tastablePoly-morph I of sulfamerazine (SMZ)to the more stablePolymorph II at 241C (room temperature)was chosen as the model system,while N4-acetylsulfamerazine (NSMZ),sulfadiazine (SD),and sulfamethazine (SM)were each chosen in turn as theimpurity (Sche me1).2.Materials and methods 2.1.MaterialsSulfamerazine (SMZ,4-amino-N-[4-methyl-2-pyrimidinyl]benzenesulfonamide,Lot #47H0114,purity >99.9%),SD,and SM were purchased from Sigma Co.(St.Louis,MO).Polymorphs I and II of SMZ were prepared as described in a previous paper [3].HPLC grade acetonitrile (ACN)was purchased from Fischer Scientiﬁc (Pittsburgh,PA).Residual water in ACN wasminimized by adding molecular sieves and anhy-drous calcium sulfate (Drierite,Hammond,Xenia,OH).N4-acetylsulfamerazine (NSMZ,4-acetamido-N-[4-methyl-2-pyrimidinyl]benzene-sulfonamide)was synthesized as described by Roblin and Winneck [7].The starting materials,namely acetylsulfanilyl chloride and 2-amino-4-methyl-pyrimidine,were purchased from Aldrich Chemi-cal Co.(Milwaukee,WI).The ﬁnal precipitated product was recrystallized twice from tetrahydro-furan.The water content of NSMZ,determined by Karl Fischer titrimetry,was 6.3%(w/w),which corresponds to the monohydrate [theoretically 5.6%(w/w)water].Dehydration was achieved by storing at zero humidity for 2weeks.The anhydrate form of NSMZ (water content o 0.5%,w/w)was used in the later experiments.2.2.Solvent-mediated polymorphic transformationThetransformation from theme tastablePoly-morph I to Polymorph II at 241C was studied in ACN [3].Polymorph I was suspended in its presaturated solution containing a known amount of an impurity at 241C.Thewe ight/volumeratio of suspended solid to solvent was 20mg/ml.The suspension was shaken by a wrist-action shaker (Model 75,Burrell,Pittsburgh,PA)at B 300strokes/min.A portion of the suspension was withdrawn and ﬁltered at designated times and the polymorphic composition of thesolid phasewasS NHOONNC H3NH 2C H 3S N HOONN NH 2S NHOO N NC H 3C H 3C ONHsulfamerazine (SMZ)N4-acetylsulfamerazine (NSMZ)sulfamethazine (SM) sulfadiazine (SD)Scheme 1.Molecular structure of the host molecule,SMZ,and the impurity molecules,NSMZ,SD,SM.C.-H.Gu et al./Journal of Crystal Growth 235(2002)471–481472determined by powder X-ray diffractometry (PXRD,Siemens D5005,Germany),which was described in detail in the previous reports[3,8]. Meanwhile,the concentration of SMZ in the solution during thetransformation proce ss was determined at l¼307nm with a spectrophot-ometer(DU7400,Beckman,Irvine,CA)[9].The standard solution contained the same concentra-tion of theimpurity as thesolution in which SMZ was suspended.To determine the crystal growth rate of Form II, 270mg(90%)of Polymorph I and30mg(10%)of Polymorph II were geometrically mixed and were suspended in the solutions described above,to determine the polymorphic transformation rate. This high proportion of seeds(10%of II)obviated the primary nucleation step in the transformation. Thepolymorphic transformation rateso de te r-mined corresponded to the crystal growth rate of themorestablePolymorph II in solution[3].2.3.Scanning electron microscopy(SEM) Themorphology was analyze d by SEM(S-800, Hitachi,Tokyo,Japan)at an accelerating voltage of10kV.The samples were sputter-coated with platinum to a thickness of50(A.2.4.Calculation of the impurity–surface binding energyTheinte raction of theimpurity with a growing surfacemay becalculate d,assuming that the solvent has no effect on the available conforma-tions of the impurity molecule[10].Commercial software(Ce rius2t,Molecular Simulation Inc. San Diego,CA)was employed to calculate the binding energy of the impurity molecule to the crystal surface.The Dreiding2.21forceﬁeld was used to minimize the structure and to calculate the energy.For purposes of comparison,the binding energy of one molecule of each impurity to aﬁxed and deﬁned crystal face was calculated according to the procedure described by Jang and Myerson [10].The binding energy was obtained by sub-tracting the energy of the impurity molecule in the corresponding conformation from the minimum total energy of the surface bound with a single impurity molecule.3.Results and discussion3.1.Inhibitory effect of impurities on the transformation of SMZ Polymorph I to Polymorph II in ACN suspensionSolvent-mediated transformation consists of three consecutive steps:dissolution of the less stablepolymorph;nucle ation of themorestable polymorph;and crystal growth of themorestable polymorph.Theimpurity may affe ct any or all of these three steps.It was found in a previous study that thetransformation ratein pureACN is controlled by the crystallization rate of SMZ Polymorph II[3].To determine the rate-limiting step in the presence of the impurity,the concen-tration of SMZ in thesolution was monitore d.The concentration vs.time proﬁle(Fig.1)indicated that thetransformation ratein thepre se nceof impurity is still controlled by the crystallization rate of Polymorph II,because the concentration of SMZ was closeto thesolubility of theme tastable Polymorph I until all Polymorph I in thesuspe n-sion had transformed to Polymorph II.In the presence of impurity,both the nucleation rate and crystal growth rate(Table1)were reduced signiﬁcantly.However,the effect of NSMZ is 01234560102030Time (h)Conc.ofSMZinsolution(mg/ml)Fig.1.SMZ concentration–time proﬁle during polymorphic transformation(I-II)in ACN solution containing the impurity,NSMZ(E)or SM(’)or SD(m),at molefraction 1.71Â10À5.C.-H.Gu et al./Journal of Crystal Growth235(2002)471–481473much greater than that of SM and SD.The morphology of SMZ Polymorph II grown from solutions containing each of these impurities is shown in Fig.2.Themorphology of SMZ grown in the presence of SM or SD is similar to that grown in its absence.However,in the presence of NSMZ at a molefraction as low as3.43Â10À6, themorphology is change d to a plateshapewith dominant\001\faces.These results indicate that all three impurities inhibit the crystallization of SMZ Polymorph II and that therank orde r of the inhibitory effect is NSMZ b SD>SM.The rank order of the inhibitory effect of the impurity may be explained by examining the crystal structureof SMZ Polymorph II,which is shown in Fig.3[11].Theamino group on the phenyl ring serves as a hydrogen bond donor in thecrystal of Polymorph II.If a NSMZ mole cule substitutes for a SMZ molecule in the crystal lattice,the acetyl group of NSMZ,which has replaced a hydrogen atom in SMZ,will hence disrupt the hydrogen bond interaction with incoming SMZ molecules(Scheme1).Therefore, the rate of molecule incorporation,i.e.,the crystallization rate,will be reduced.In addition, at the nucleation stage,the incorporated impurity molecule may destabilize the molecular aggregates and facilitate the dissolution of the aggregate, resulting in a reduction of the nucleation rate.In this way,the nucleation and crystal growth process can be greatly disrupted by NSMZ.However,SM and SD differ from SMZ only in the methyl group on thepyrimidinering,which doe s not participate in the hydrogen bonding interaction.Therefore, SM and SD are less effective in inhibiting the crystallization process than is NSMZ.The inhibitory effect of the impurity does not follow therank orde r of themole cular sizeof the impurity.The molecular volumes and mole-cular surface areas of the impuritymolecules, Fig.2.Morphologies of the crystals of SMZ Polymorph II grown from ACN in the presence of impurities,NSMZ,SM,and SD.The molefraction of theimpurity in thesolution is1.71Â10À5.C.-H.Gu et al./Journal of Crystal Growth235(2002)471–481475respectively,are:NSMZ,244.6(A3,295.4(A 2;SM,225.1(A3,275.2(A 2;SD,196.3(A 3,233.4(A 2.3.2.Surface–impurity binding energyThe effects of impurities on crystallization kinetics are related to the strength of the inter-molecular interaction between the impurity and the terraces,steps,and kinks of the nuclei or crystals.Because crystal growth of SMZ in ACN follows theBCF me chanism,theimpurity inhibits crystal growth mainly by being adsorbed on to the steps and kinks.Chernov found that the decrease in step rate is proportional to the time when the kinks are free of impurities [12–14].If the lifetime of adsorbed molecules at kinks,steps,and terraces is shorter than the time required for the step to cover the interstep distance,impurities with great-er adsorption energy at kinks and steps are more likely to be adsorbed and thereby to inhibit the crystal growth.The adsorption energy at kinks and steps includes the adsorption energy on the terrace,which is proportional to the calculated solute–surface binding energy.The calculated solute and solvent binding energies (kcal/mol)to the crystal faces (001),(100),and (110),respec-tively,of SMZ Polymorph II are:NSMZ,À23.0,À20.4,À19.8;SM,À8.1,À14.5,À18.4;SD,À21.8,À17.6,À19.0;SMZ (host molecule),À19.5,À13.9,À12.2;ACN (solvent),À6.52,À6.13,À5.28.The greater the absolute value of the surface–impurity binding energy,the stronger the binding of impurity molecule to the surface,indicating higher probability of absorption on theste ps or kinks.The results show that all three impurities have greater binding energies to the individualcrystalFig.3.Crystal structure of SMZ Polymorph II [11].The dotted lines represent the hydrogen bonds.C.-H.Gu et al./Journal of Crystal Growth 235(2002)471–481476faces than does the host molecule,SMZ,and the solvent molecule,ACN,which supports the fact that all three impurities exert inhibitory effects. Among the three impurities,the binding energy of NSMZ is the greatest,followed by SD and then by SM,which is in agreement with the rank order of their inhibitory effects on both nucleation and crystal growth.Desolvation of both solute mole-cules and growth sites is an essential step in crystal growth.The difference in solvation energy be-tween the host molecule and the impurity mole-cule,compared to that at the growth sites,might also affect the binding preference of the solute molecules during crystal growth.This effect is neglected when the binding energy is compared.3.3.Relationship between the concentration of the impurity and the inhibitory effect on crystallization Several models have been developed to describe the dependence of the growth inhibitory effect of theimpurity on theconce ntration of theimpurity [15–19].The impurity molecules areﬁrst adsorbed onto the surface of a growing crystal,where they interfere with the further incorporation of SMZ molecules,causing the reduction in growth rate. Theamount of impurity adsorbe d onto thesurface may be described by the classical Langmuir adsorption isothermy¼kc1þkc;ð1Þwhere y is thefraction of thesurfacecove re d bythe impurity molecules,c is theconce ntration oftheimpurity in solution,and k is theratio of theadsorption rate coefﬁcient to desorption ratecoefﬁcient.If the adsorption of new molecules is subject toblocking by the adsorbed molecule or the surfacecontains unﬁllablevoids,themaximum proportionof the occupied area available for adsorption,y max;is less than unity(0o y max o1),corresponding to an empirical Langmuir equation[20].At equili-brium,the percentage of the surface coverage,y;may be expressed byy¼y max kc1þkc;ð2Þwhere y max is themaximum proportion of thesurfaceavailablefor adsorption,and theothe rparameters have the same meaning as deﬁnedpreviously.Because the classical Langmuir ad-sorption isotherm(Eq.(1))and the empiricalLangmuir adsorption isotherm(Eq.(2))have thesame form and therefore cannot be distinguishedwhe nﬁtting thedata,theclassical Langmuiradsorption isotherm is applied toﬁt the data inthe following models.The same value of theﬁttedparameters will be obtained when applying theempirical Langmuir adsorption isotherm toﬁt themodel,although theﬁtted parameters have differ-ent meanings.In order to model the inhibitory effect of theadsorbed impurity molecule on the crystal growth,the crystal growth mechanism needs to be deter-mined.The Jackson factor[5,21],a;may becalculated to estimate the growth mechanism bythefollowing e quation:a¼E sliceh k lE crystalD H sRT;ð3Þwhere E sliceh k lis the slice energy,E crystal is the energyof crystal formation,D H s is thehe at of solution,Ris thegas constant,and T is thete mpe rature[22].The a values are8.4for the(001)face,7.9for the(010)face,5.4for the(100)face,and6.5for theð1%11Þface[23].Be causethe a values are>5,crystal growth is likely to follow the BCFmechanism[5].Several established models fordescribing the dependence of the growth inhibitoryeffect on the impurity concentration[15–19]weretested byﬁtting to the experimental data[23].Boththe Cabrera–Vermileya model and the Kubota–Mullin model may describe the inhibitory effect ofimpurity on crystal growth following theBCFmechanism,but that proposed by Kubota andMullin[15]gave the bestﬁt to the experimentalresults.This equation for the latter model isf¼1Àe y;ð4Þwhere f is theratio of thecrystal growth ratein thepresence of impurity to that in its absence and e isthe inhibitory effectiveness factor of the impurity.The other symbols have the same meaning asdeﬁned previously.In this model,the growth rateis assumed to be proportional to the step-C.-H.Gu et al./Journal of Crystal Growth235(2002)471–481477advancement velocity.The impurities are adsorbed onto a linear array of active sites of steps to inhibit the step advancement.The inhibitory effect,e ;is determined by both the size of the impurity molecule and the strength of interaction between theimpurity and thecrystal surface .Be cause 0o y max p 1;when e >1and theconce ntration of impurity is high enough to make y ¼y max ;crystal growth may be blocked completely when the e y X 1:However,when e o 1;thecrystal growthrate will be reduced maximally to a value equal to (1Àe ),and the dependence of the inhibitory effect on the concentration of the impurity will level off at high concentrations of the impurity.Rearran-ging Eq.(4)with inserting Eq.(1)gives the following linear expression:1=ð1Àf Þ¼ð1=ek Þð1=x Þþð1=e Þ;ð5Þwhere x is themolefraction of theimpurity in the solution and theothe r symbols havethesame(a)(b)x (mole fraction)x (mole fraction)0.00000.00020.00040.00060.00080.00100.00120.00.20.40.60.80.00.20.40.60.8F r a c t i o n o f n u c l e a t i o n r a t e ( f )F r a c t i o n o f c r y s t a l g r o w t h r a t e ( f )Fig.4.Fitting of the experimental data to Eq.(4),which describes the model proposed by Kubota and Mullin [11].The lines are drawnbased on the parameters determined by Eq.(5),and the symbols represent the experimental results.(a)Fitting of the crystal growth data;and (b)ﬁtting of the nucleation data.The impurities are NSMZ, ;SD,.;and SM,J .C.-H.Gu et al./Journal of Crystal Growth 235(2002)471–481478meaning as deﬁned previously.The data in Table1 wereﬁtted to Eq.(5)to determine the values of k and e(Table2).Theﬁt of thedata to Eq.(4)is shown in Fig.4a.The e valuefor NSMZ is slightly>1,which indicates that the crystal growth may cease completely when the concentration of NSMZ is high enough,at which point y is closeto unity.We found that,when the concentration of NSMZ reaches3.26Â10À4molefraction,thetransforma-tion virtually ceases.At this concentration,the model also predicts that the crystal growth rate will be equal to zero,which is in agreement with the experimental observations.In the presence of SM or SD,the e values are o1,which means that the maximum extent of reduction in the crystal growth rate by these two impurities is(1Àe).TheKubota–Mullin mode l predicts that the minimum crystal growth rate in the presence of SM or SD is27%or22%, respectively,of that in their absence.In Table1, the conversion time in the presence of SM reaches a plateau,2h,despite the increase of the SM concentration.This maximum time corresponds to theminimum growth ratein thepre se nceof SM, which is25%of thegrowth ratein its abse nce.In the presence of SD,the plateau value is2.25h, corresponding to22%of the growth rate in its absence.The predicted value agrees with the experimental value.In Table2,the rank orders of the values of k and e follow the rank order of the inhibitory effect and the rank order of the surface–impurity binding energy.The k value is directly related to the surface–impurity binding energy by the Arrhenius equation[24].The value of the effectiveness factor, e;is related to the strength of the interaction between the impurity molecule and the crystal surface,which may reﬂect the surface–impurity binding energy[25].Therefore,the calculated surface–impurity binding energy may serve to screen the inhibitory effect of the impurity. Unlike the mechanism for impurity effect on the crystal growth rate,the dissolved impurity may reduce the nucleation rate by occupying the active sites on prenuclear aggregates,thereby inhibiting their growth beyond the critical size of a stable nucleus,and/or by becoming incorporated into the prenuclear aggregates or nuclei,thereby disrupting them and facilitating their dissolution.If the impurity acts primarily by inhibiting thegrowth of prenuclei,the models for crystal growth may be applied to describe the relationship between the concentration of the impurity and the inhibitory effect on nucleation.However,if the impurity acts primarily by its incorporation,there lationship between the segregation coefﬁcient and the con-centration of the impurity must be known to model the dependence of the inhibitory effect on theimpurity conce ntration.In this study,the relative nucleation rate is estimated by the reciprocal of the induction time (Table1).When the inhibitor prevents the molecular aggregates from growing into stable nuclei,the relationship between the concentration of theimpurity and there duction in nucle ationTable2Estimated parameters of the Kubota–Mullin model[15]for crystal growth inhibition based on Eq.(5)NSMZ SM SD Langmuir(Eq.(5))k 5.66Â105 4.55Â105 5.31Â105e 1.020.7280.781 Estimated minimum crystal growth rate a00.270.22 Minimum experimental crystal growth rate b00.250.22a Theminimum crystal growth rateis theminimum ratio of thecrystal growth ratein thepre se nceof an impurity to that in its absence.b The minimum experimental crystal growth rate is the ratio of the growth time in the absence of impurity to that with the highest concentration of impurity(Table1).C.-H.Gu et al./Journal of Crystal Growth235(2002)471–481479ratemay bede scribe d by Eq.(4),in which f is the fraction of the nucleation rate in the presence of impurity to that in its absence.Fig.4b summarizes theﬁt to Eq.(4).Theﬁtting appears satisfactory,and the esti-mated minimum nucleation rates in the presence of various impurities agree with the experimental values.These results suggest that the impurity may retard the nucleation of Polymorph II by inhibit-ing the growth of the molecular aggregates. However,the experimental results do not exclude thepossibility that theimpurity may beincorpo-rated into the host lattice in the form of prenuclei and destabilizes them.With increasing concentra-tion of theimpurity in thesolution,theamount of incorporated impurity may reach a maximum, corresponding to the solid solubility limit of the impurity in thehost crystal[26].This maximum incorporation may also explain the constancy of the inhibitory effect at higher concentrations of SM and SD.The solid-state relationship between thehost crystal and theimpurity mole culewill be studied to examine the possibility of solid solution formation.4.Conclusions1.Structurally related additives signiﬁcantly in-hibit thetransformation of Polymorph I of SMZ to Polymorph II in suspension in ACN, by inhibiting both thenucle ation and thecrystal growth of themorestablePolymorph II.2.The rank order of the inhibitory effect isN4-acetylsulfamerazine(NSMZ)b sulfadiazine (SD)>sulfamethazine(SM).This rank order agrees with the rank order of the binding energy of theimpurity to thecrystal surface.3.The relationship between the inhibitory effectand theconce ntration of theimpurity is be st described by a model proposed by Kubota and Mullin[15,16].When the concentration of NSMZ is sufﬁciently high(>6.86Â10À5mole fraction for nucleation or>3.26Â10À4mole fraction for crystal growth),both thenucle ation rateand thecrystal growth ratebe come negligible.However,in the presence of SD or SM,the nucleation rate is maximally reduced to13%or29%,respectively,with respect to that in theabse nceof theimpurity.Thecrystal growth rate is maximally reduced to25%by SM or22%by SD with respect to that in its absence.Theimpurity e ffe ct on thestabilization of a particular polymorph should be considered during polymorph screening.Because the impurity may delay the discovery of a polymorph,it is necessary to repeat the screen for polymorphs after the chemical purity of the material has been opti-mized.On the other hand,stabilization of a metastable polymorph with superior physicochem-ical properties may be achieved by adding an acceptable additive with a suitable binding energy. The kinetic models discussed in this paper may be used to estimate the concentration of the additive necessary to achieve stabilization of the metastable phase over the shelf life of a product. AcknowledgementsWethank Bristol–Mye rs Squibb for an unre st-ricted grant and also the Supercomputing Institute of the University of Minnesota forﬁnancially supporting our use of the Medicinal Chemistry/ Supercomputing Institute Visualization F Work-station Laboratory.References[1]S.R.Chemburkar,et al.,Org.Process Res.Dev.4(2000)413.[2]N.Rodriguez-Hornedo,D.Murphy,J.Pharm.Sci.88(1999)651.[3]C.H.Gu,V.Young Jr.,D.J.W.Grant,J.Pharm.Sci.90(2001)1878.[4]H.Bundgaard,J.Pharm.Pharmacol.26(1974)535.[5]J.W.Mullin,Crystallization,3rd Edition,Butterworth-Heinemann,London,UK,1993.[6]R.Vrcelj,H.Gallagher,J.Sherwood,J.Am.Chem.Soc.123(2001)2291.[7]R.O.Roblin Jr.,P.S.Winneck,J.Am.Chem.Soc.62(1940)2002.[8]G.Zhang,Inﬂuence of solvents on properties,structures,and crystallization of pharmaceutical solids,Ph.D.Thesis, Department of Pharmaceutics,University of Minnesota, Minneapolis,MN1998,pp.70–122.C.-H.Gu et al./Journal of Crystal Growth235(2002)471–481 480[9]R.D.G.Woolfender,in:K.Florey(Ed.),AnalyticalProﬁles of Drug Substances,Academic Press,New York, NY,1977,pp.515–517.[10]A.S.Myerson,S.M.Jang,J.Crystal Growth156(1995)459.[11]K.R.Acharya,K.N.Kuchela,J.Crystallogr.Spec.Res.12(1982)369.[12]A.A.Chernov,in: A.V.Shubnikov(Ed.),Growth ofCrystals,3rd Edition,Consultant Bureau,NY,1962,p.31.[13]A.A.Chernov,p.4(1961)116.[14]A.A.Chernov,Modern Crystallography III CrystalGrowth,Springer,Berlin,1984,p.162.[15]N.Kubota,J.W.Mullin,J.Crystal Growth152(1995)203.[16]N.Kubota,M.Yokota,J.W.Mullin,J.Crystal Growth182(1997)86.[17]M.C.van der Leeden,D.Kashchiev,G.M.van Rosmalen,J.Crystal Growth130(1993)221.[18]R.J.Davey,J.Crystal Growth34(1976)109.[19]N.Cabrera,D.Vermilyea,in:B.Doremus,B.W.Roberts,D.Turnbull(Eds.),Growth and Perfection of Crystals,Wiley,New York,NY,1958,p.393.[20]Z.Adamczyk,B.Siwek,M.Zembala,P.Belouschek,Adv.Colloid Interface Sci.48(1994)151.[21]K.A.Jackson,Liquid Metals and Solidiﬁcation,AmericanSociety of Metals,Cleveland,OH,1958.[22]P.Bennema,J.Phys.D26(1993)B1.[23]C.H.Gu,Inﬂuence of solvent and impurity on thecrystallization process and properties of crystallized product.Ph.D.Thesis,Department of Pharmaceutics, University of Minnesota,Minneapolis,MN,2001.[24]M.Rauls,K.Bartosch,M.Kind,S.Kuck,cmann,A.Mersmann,J.Crystal Growth213(2000)116.[25]N.Kubota,M.Yokota,J.W.Mullin,J.Crystal Growth212(2000)480.[26]Z.J.Li,D.J.W.Grant,Int.J.Pharm.137(1996)21.C.-H.Gu et al./Journal of Crystal Growth235(2002)471–481481。

电石渣可控制备多晶型、多形貌纳米碳酸钙的研究进展

第52卷第4期2023年4月人㊀工㊀晶㊀体㊀学㊀报JOURNAL OF SYNTHETIC CRYSTALS Vol.52㊀No.4April,2023电石渣可控制备多晶型、多形貌纳米碳酸钙的研究进展丁㊀羽,张金才,王宝凤,郭彦霞,薛芳斌,程芳琴(山西大学资源与环境工程研究所,国家环境保护废弃资源高效利用重点实验室,太原㊀030006)摘要:碳酸钙有不同的晶体特征,使其在各个领域发挥不同的作用,对碳酸钙晶型㊁形貌和尺寸的控制是无机材料制备的研究热点㊂以电石渣为原料制备纳米碳酸钙能够实现变废为宝,是含钙固废综合利用的研究方向之一㊂因此在电石渣制备纳米碳酸钙过程中同步实现晶型㊁形貌的调控,能够将低附加值的电石渣固废转化为高附加值的纳米碳酸钙产品,具有良好的环境效应和经济效益㊂本文总结了电石渣制备纳米碳酸钙的方法,重点讨论了制备过程中晶型和形貌控制方面的研究进展㊂结果表明,在碳酸钙晶体成核和生长的过程中,控制工艺条件可以通过影响过饱和度进一步实现对晶型和形貌的调控,且不同种类的添加剂作用机理也不尽相同㊂热力学㊁动力学作为控制结晶各过程平衡的基础,可以用来解释各影响因素的作用机理㊂关键词:纳米碳酸钙;电石渣;晶型;形貌;可控制备;热力学;动力学中图分类号:TB321;TQ132.3+2㊀㊀文献标志码:A ㊀㊀文章编号:1000-985X (2023)04-0710-11Progress on Controllable Preparation of Polycrystalline and Polymorphic Nano Calcium Carbonate by Calcium Carbide SlagDING Yu ,ZHANG Jincai ,WANG Baofeng ,GUO Yanxia ,XUE Fangbin ,CHENG Fangqin (State Environmental Protection Key Laboratory of Efficient Utilization of Waste Resources,Institute of Resources and Environmental Engineering,Shanxi University,Taiyuan 030006,China)Abstract :Calcium carbonate has different crystal characteristics,which makes it play different roles in various application fields.The control of calcium carbonate crystal structure,morphology and size is a hot research topic in the preparation of inorganic materials.The preparation of nano calcium carbonate produced from calcium carbide slag can realize the transformation of waste into resource,which is one of the important research fields concerning the recycling of calcium-containing solid wastes.The controllable preparation of calcium carbonate with different crystalline structure and morphology from calcium carbide slag can make the worthless calcium carbide slag transform into high value-added nano grade products with good environmental and economic effects.The preparation methods of nano calcium carbonate from calcium carbide slag are summarized in this paper,the research progress of the control of crystal structure and morphology during the preparation process is discussed emphatically.The results indicate that,during the nucleation and growth of calcium carbonate crystals,controlling the process conditions can further achieve the regulation of crystal structure and morphology by influencing the degree of supersaturation,and the action mechanism varies from different kinds of additives.As the basis for controlling the equilibrium of the crystallization processes,thermodynamics and kinetics can be used to explain the mechanism of action of each influencing factor.Key words :nano calcium carbonate;calcium carbide slag;crystal structure;morphology;controllable preparation;thermodynamics;kinetics㊀㊀㊀收稿日期:2022-12-07㊀㊀基金项目:2022年度国家重点研发计划项目(2022YFB4102100)㊀㊀作者简介:丁㊀羽(1998 ),女,山东省人,硕士研究生㊂E-mail:2553646458@㊀㊀通信作者:张金才,副教授㊂E-mail:chaner9944@ 0㊀引㊀㊀言电石渣是生产聚氯乙烯的副产品,其主要成分Ca(OH)2含量在71%~95%,钙质含量高[1-4]㊂利用电石㊀第4期丁㊀羽等:电石渣可控制备多晶型㊁多形貌纳米碳酸钙的研究进展711㊀渣制备纳米碳酸钙,不仅可以吸收二氧化碳,减少碳排放,还能产生优质的纳米碳酸钙产品㊂在当前双碳目标的大背景下,发展该产业具有重要的现实意义㊂普通碳酸钙制造成本低,在我国产能和用量大,被广泛应用于各个行业中㊂涂料㊁造纸㊁塑料㊁橡胶等行业对高品质碳酸钙市场需求巨大,纳米碳酸钙作为性能优异的无机填料可以满足不同行业的使用要求[5]㊂当前我国纳米碳酸钙产品主要是石灰岩经过煅烧-消化-碳化-压滤-干燥-粉碎几道工艺步骤制成[6],产品性能好㊂该工艺中碳化利用的是煅烧释放的二氧化碳,实质上是实现了碳循环利用,并没有实现碳减排,还面临石灰岩开采带来的生态环境问题㊂在绿色㊁可持续发展的背景之下,以电石渣为原料生产纳米碳酸钙不仅能够消除固废资源堆积的环境隐患,还能获得应用广泛㊁附加值高的纳米碳酸钙产品,经济效益好[7]㊂电石渣制备纳米碳酸钙产业前景好㊁发展潜力大,但是当前在我国还没有实现大规模工业化生产㊂为尽快推进该产业的快速发展,本文广泛分析总结该领域的研究成果,综述了电石渣制备纳米碳酸钙产品的研究进展㊂从制备方法㊁晶体控制两方面展开论述,并对未来的发展趋势作出展望,期望能够对该产业的从业人员有所帮助㊂1㊀纳米碳酸钙的结构与性质碳酸钙主要有三种晶型,为方解石型㊁球霰石型㊁文石型,它们分别属于三方㊁六方和斜方晶系[8]㊂其中:方解石能量最低,热力学最稳定;球霰石能量最高,热力学最不稳定;文石介于方解石和球霰石之间㊂纳米碳酸钙颗粒的形貌主要受其内在晶体结构的影响,方解石型常以规则的菱面体存在,文石型以柱状㊁针簇状存在,球霰石型以球状聚集而成,图1为三种晶体结构及对应典型形态[9]㊂在不同的条件下颗粒形貌会发生变化,常见的晶体形态有立方形㊁球形㊁针形㊁链形等,不同形态的碳酸钙具有不同的性质,能够适用于不同领域的应用[10]㊂图1㊀碳酸钙的三种晶体结构和典型形态[9]Fig.1㊀Three crystal structures and typical morphologies of calcium carbonate [9]立方形碳酸钙具有一定的强度优势,作为填充剂可以起到补强作用,常用于塑料㊁橡胶行业[11];球形碳酸钙具有比较大的比表面积和良好的分散性,对油墨有很好的吸收性,多用于造纸行业[12];针形碳酸钙能够增加橡胶制品的耐曲挠性,添加到复合材料中能够起到补强增韧的作用[12-13];链形碳酸钙颗粒混入橡胶或712㊀综合评述人工晶体学报㊀㊀㊀㊀㊀㊀第52卷塑料时,可以有效地起到补强作用[11]㊂不同行业对最终得到的纳米碳酸钙产品的品质有不同的指标要求,归纳起来主要有纯度㊁白度㊁形貌㊁晶型㊁粒径范围㊁沉降体积㊁比表面积㊁分散性和白度等㊂在制备纳米碳酸钙的过程中,各项指标受多种因素的影响,最终得到的产品指标要符合国标要求[13],国标中规定了在橡胶㊁塑料㊁涂料等行业中纳米碳酸钙产品性能指标要求,具体如表1所示㊂表1㊀纳米碳酸钙产品性能指标要求[14]Table1㊀Performance index requirements of nano calcium carbonate product[14]项目橡胶塑料用指标Ⅰ型Ⅱ型Ⅲ型涂料用指标平均粒径/nm<5050~70<100ɤ60~90比表面积BET/(m2㊃g-1)ȡ18ȡ18ȡ18ȡ20碳酸钙干基质量分数/%ȡ95ȡ95ȡ95ȡ95白度ȡ95ȡ95ȡ94ȡ93吸油值ɤ30ɤ30ɤ40ɤ30~50控制结晶过程能够制备出不同晶型㊁形貌的纳米碳酸钙产品,从而提高产品最终的附加值与适用性,控制的变量有各项工艺参数以及添加剂的种类㊁用量等,如何可控制备纳米碳酸钙将在下文详细论述㊂2㊀纳米碳酸钙的制备纳米碳酸钙是指尺寸在纳米数量级的碳酸钙,与常规的无机材料不同,它具有特殊的小尺寸效应㊁宏观量子隧道效应㊁量子尺寸效应和表面效应等特性,增韧补强的效果非常显著[15-16]㊂通过物理㊁化学方法可以加工得到适用于不同应用场景的产品㊂2.1㊀传统纳米碳酸钙的制备方法纳米碳酸钙主要有以下三种合成体系:1)Ca(OH)2 H2O CO2;2)Ca2+ H2O CO2-3;3)Ca2+ R CO2-3㊂根据合成过程中化学反应的不同进行划分,CaCO3的合成可以分成碳化法㊁复分解法和乳液法[6]㊂表2列出了纳米碳酸钙的制备方法及其各自特点㊂表2㊀纳米碳酸钙的制备方法[17]Table2㊀Preparation method of nano calcium carbonate[17]反应体系制备方法优点不足Ca(OH)2 H2O CO2反应体系间歇鼓泡碳化法成本低,操作简单,生产能力大能耗高,产品粒径不均匀连续喷雾碳化法可连续,生产能力大,产品可控设备要求高,技术含量高,管理难度大间歇搅拌碳化法产品可控,常用设备投资大,操作复杂超重力反应结晶法时间短,产品粒径范围集中反应装置要求高,能耗大Ca2+ H2O CO2-3反应体系氯化钙碳酸铵法氯化钙碳酸氢钠法原料易得且成本低,制备工艺操作简单,产品白度较高杂质离子难去除石灰碳酸钠法Ca2+ R CO2-3反应体系凝胶法产品可控,适合研究结晶过程有机物难去除微乳液法避免产品团聚,操作简单主要应用于试验其中Ca(OH)2 H2O CO2反应体系即碳化反应体系,是目前工业生产纳米碳酸钙最常用的方法㊂碳化反应属于气-液-固三相反应,具体反应过程为[18]:Ca(OH)2(s)⇌Ca2+(aq)+2OH-(aq)(1)CO2(g)⇌CO2(aq)(2)CO2(aq)+2OH-(aq)⇌CO2-3(aq)+H2O(aq)(3)Ca2+(aq)+CO2-3(aq)⇌CaCO3(s)(4) 2.2㊀电石渣制备纳米碳酸钙电石渣是以Ca(OH)2为主要成分,还有少量Fe㊁Si㊁Al㊁Mg杂质的固废资源[19]㊂通过预处理方法提取其㊀第4期丁㊀羽等:电石渣可控制备多晶型㊁多形貌纳米碳酸钙的研究进展713㊀中钙离子,形成的含钙溶液与CO 2进行碳化反应生产纳米碳酸钙,典型工艺如图2所示㊂在制备过程中需要解决杂质去除㊁钙离子有效提取㊁碳化成核㊁晶体生长与控制几个方面的问题,针对这些问题不断进行工艺的选择和优化㊂图2㊀电石渣制备纳米碳酸钙的典型工艺[11]Fig.2㊀Typical preparation process of nano calcium carbonate produced from calcium carbide slag [11]2.2.1㊀预处理电石渣制备纳米CaCO 3需经过预处理,常见的方法有高温煅烧法和溶液浸提法㊂电石渣中含有一些焦炭和氧化物杂质,去除不彻底将会影响最终产品的白度和活度㊂高温煅烧法可去除残留的微量碳组分,但不能去除Fe㊁Si㊁Al㊁Mg 的氧化物杂质,获得产品纯度不高[20]㊂溶液浸提法能够有效地从电石渣中提取钙,电石渣中不与溶液反应的含硅铝铁的固体杂质经过滤去掉,得到纯度好㊁白度高的纳米碳酸钙[21]㊂提钙过程中涉及很多影响因素,如浸提液以及各项工艺参数温度㊁pH 值㊁搅拌速度等㊂浸提液的选择:使用酸类㊁盐类溶液来促进碱性原料中有效钙的溶解,然后进行固液分离,利用液相进一步生产高纯度的CaCO 3[22]㊂在这一过程中,NH 4Cl㊁NH 4HSO 4㊁甘氨酸㊁柠檬酸等均可以作为浸提液,提高在碳酸化反应的溶液中Ca 2+的可用性,表3总结了不同浸提液的效果㊂表3㊀浸提过程的主要参数[23-26]Table 3㊀Main parameters of the extraction process [23-26]浸提液浓度反应条件钙的转化率文献NH 4Cl 2.5mol /L 室温㊁浸提时间30min㊁pH =892%[23]NH 4HSO 4 1.4mol /L 100ħ㊁3h 接近100%[24]柠檬酸0.08mol /L 室温㊁持续搅拌92%[25]甘氨酸2mol /L 原料粉煤灰㊁室温42%[26]总结近几年的研究[23-30],酸性铵盐(NH 4Cl㊁NH 4HSO 4等)被认为是常见㊁效果优良的浸提液㊂柠檬酸㊁甘氨酸等浸提液在制备过程中能够呈现多重作用:水溶液中的氨基酸可以根据环境的变化灵活地转移质子,甘氨酸在浸提过程中能够促进Ca 2+浸出,在碳酸盐沉淀过程中既利于CO 2吸收又可在晶体生长过程中充当晶型调节剂[26];柠檬酸盐中的柠檬酸根离子对钙离子具有配位作用,可以显著提高电石渣的浸出率,在结晶过程中可以减缓晶体生长并有利于纳米尺度上的沉淀[25]㊂工艺参数的影响:浸提过程中涉及很多影响因素,为探究最佳工艺条件,分别研究了pH 值㊁反应时间㊁NH 4Cl 过量程度这三个影响因素的作用效果㊂在浸提过程中Fe㊁Si㊁Al㊁Mg 的氧化物或氢氧化物是主要的杂质,利用缓冲溶液控制pH >7,此时杂质物质的溶解度小,杂质的影响作用较小[31]㊂如图3(b)所示,随着氯化铵过量程度的增加,Ca 2+提取率呈现先降低后增加的趋势,但都低于不过量时的值,因此一般选择不过量进行实验;如图3(c)所示,随着反应时间的增加,Ca 2+提取率呈现上升趋势,30min 时Ca 2+提取率达到最高值,说明化学反应已完成㊂2.2.2㊀碳化反应比较而言,碳化法更容易对碳酸钙的晶型以及形貌进行控制[5]㊂碳酸钙晶体的产生发生在碳化阶段,通过控制碳化阶段的工艺参数如Ca 2+浓度㊁温度㊁pH 值㊁添加剂等,最终可以得到不同的产品㊂工艺条件的影响:在碳化反应过程中,化学反应㊁成核和生长是同时发生的3个主要步骤[32]㊂因此,在碳化反应过程中改变条件控制这3个步骤,能够得到不同的纳米CaCO 3产品㊂反应物盐(Ca 2+)的初始浓度影响合成CaCO 3颗粒的大小㊁形貌等㊂例如,在乙二醇的存在条件下控制714㊀综合评述人工晶体学报㊀㊀㊀㊀㊀㊀第52卷Ca2+的添加量,可以使产品颗粒的大小和形态可控㊂Ca2+浓度的差异对体系中的反应有不同的影响,过量的Ca2+减缓颗粒的形成过程,促进CaCO3颗粒的生长,Ca2+少而CO2-3过量时加速反应,促进早期成核,高浓度Ca2+能够形成各向异性菱形和椭球形产品,而低浓度下能形成各向同性球状体[33]㊂图3㊀pH值(a)㊁NH4Cl过量程度(b)㊁反应时间(c)对Ca2+转化率的影响[31]Fig.3㊀pH value(a),excessive degree of NH4Cl(b),leaching time(c)on Ca2+conversion rate[31]温度影响CaCO3沉淀的生成和溶解平衡,成核和生长速率受温度的影响,CaCO3沉淀在水中的溶解度随温度的变化而变化,从而对最终形成晶体的形貌和大小有显著影响㊂Domingo等[34]在45ħ时获得了菱形锐边颗粒,而通过将温度降低至25ħ观察到了偏三角面体颗粒的存在;García Carmona等[35]通过提高温度获得了粒径更大的晶体㊂pH值的作用影响具体表现为水溶液中各离子的平衡,CaCO3在水溶液中的沉淀和溶解涉及不同离子的平衡,H+㊁OH-㊁HCO-3㊁Ca2+和CO2-3的整体平衡可调节pH范围从中酸性到碱性,相关离子之间的平衡可以用各自的方程和平衡常数(K x)来描述[36]㊂可以计算出溶液中所有物种的浓度和反应活性,还可以根据公式(12)估计系统的过饱和状态从而推断晶体类型[37]㊂H++OH-↔H2O(K w)(5)CO2(g)↔CO2(aq)↔H2CO3(aq)(K H)(6)H++CO2-3↔HCO-3(K1)(7)H++HCO-3↔H2CO03(K2)(8)Ca2++CO2-3↔CaCO03(K CaCO3)(9)Ca2++HCO-3↔CaHCO+3(K CaHCO+3)(10)Ca2++OH-↔CaOH+(K CaOH+)(11)S={[a(Ca2+)㊃a(CO2-3)]/(K0sp)}1/2(12)添加剂的影响:不同的添加剂通过进入晶体内部㊁吸附在晶体表面上和改变晶体表面能等方式来影响晶体的生成过程,从而达到可控制备特定产品的目的[38-40]㊂从种类上可分为无机盐类㊁醇类㊁酸类㊁糖类和表㊀第4期丁㊀羽等:电石渣可控制备多晶型㊁多形貌纳米碳酸钙的研究进展715㊀面活性剂类等,表4总结了不同添加剂对获得的CaCO3性能的主要影响㊂表4㊀添加剂对纳米碳酸钙颗粒性能的影响[41-47]Table4㊀Effect of additives on the properties of nano calcium carbonate particles[41-47]添加剂添加剂类型浓度操作条件主要作用参考文献磷酸酸 3.5~10g/L70ħ促进文石形成[41]蔗糖㊁葡萄糖糖 Mg2+存在促进方解石超过文石[42]乙醇醇10%~50%v/v n(NH+4)/n(Ca2+)ȡ1促进球霰石㊁文石形成[43] NH+4无机盐n(NH+4)/n(Ca2+)>1低pH促进球霰石的形成[44] Mg2+无机盐n(Mg2+)/n(Ca2+)>1低pH,温度>30ħ促进文石的形成[45] CTAB阳离子表面活性剂2% 降低粒径,有利于菱形形成[46] SDS阴离子表面活性剂2g/L室温㊁4.9~12.04MPa形成具有粗糙表面的菱形方解石颗粒[47] Tween80非离子表面活性剂2g/L室温㊁4.9~12.04MPa促进纳米粒子聚集成片状[47]㊀㊀注:CTAB为十六烷基三甲基溴化铵;SDS为十二烷基硫酸钠㊂1)酸类添加剂的影响常见的有机酸类添加剂含有羧基,在晶体生长的过程中,羧酸的加入可能与碳酸钙发生强烈吸附作用,羧酸被吸附在晶体的表面上,阻碍了碳酸钙颗粒的进一步生成,从而对晶体的形貌和粒径产生影响[48]㊂而无机酸能够通过发生化学反应影响最终碳酸钙的生成,例如加入无机酸H3PO4时,H3PO4与Ca2+迅速反应形成非常细的针状羟基磷灰石(HAP,最稳定的磷酸钙),在碳化过程中针状HAP作为异质成核剂,有利于文石的形成[49-50]㊂2)糖类添加剂的影响常见的糖类添加剂有蔗糖㊁葡萄糖㊁可溶性淀粉等,含有羟基㊂Ca2+可以与糖类中所含的羟基发生电荷匹配作用,降低CaCO3结晶的成核活化能,促进成核,抑制晶体生长㊂根据徐大瑛等[51]的研究结果,添加糖类添加剂后生成的纳米碳酸钙颗粒均以方解石为主,形状比较规则,具体表现为添加葡萄糖后颗粒边界不够清晰,加入蔗糖后边界清晰但分散性一般,加入可溶性淀粉后粒径明显减少㊂3)醇类添加剂的影响醇类添加剂的加入有利于亚稳态晶型的生成,在50%乙醇的存在下,球形球霰石颗粒与方解石晶体一起出现[43]㊂乙醇对亚稳态球霰石形成的影响可以通过两种机制来解释,乙醇降低了CaCO3的溶解度,最终增加了其过饱和,这促进了动力学有利的球霰石相的产生,而不是热力学有利的方解石;另一种机制与Ca2+和CO2-3的相互作用有关,与水相比,Ca2+与乙醇的相互作用较弱,这有利于亚稳态球霰石的形成[52]㊂4)无机盐类添加剂的影响在碳酸钙生成过程中添加氨,NH+4能够提供碱性环境使反应混合物产生高过饱和度和成核率,有利于亚稳态球霰石的沉淀㊂此外,NH+4能够在吸收二氧化碳的过程中产生氨基甲酸盐来稳定球霰石颗粒[43-44]㊂Mg2+可以取代方解石中的Ca2+并结合到Mg-方解石的晶格中,由此产生的晶格畸变导致结构不稳定,Mg-方解石的溶解度增加,Ca2+在溶液中含量增加成为过饱和溶液,有利于文石的形成[42]㊂5)表面活性剂类添加剂的影响表面活性剂可能与特定的晶面发生特异性结合,在碳酸钙可控制备的过程中表现出显著的优势㊂SDS的烷基链带负电荷,可以吸附到CaCO3的正电荷面上,有利于形成表面粗糙的立方CaCO3颗粒;添加CTAB 对颗粒形态影响较小,这是由于带正电荷的烷基链和Ca2+之间的静电排斥作用使得它很难吸附到CaCO3的表面上;Tween80作为一种非离子表面活性剂能够优先吸附在中性面上,最终形成片状形貌[47]㊂尽管对CaCO3的多晶型㊁形貌和尺寸分布的控制已经成为许多学术研究的焦点,但是对CaCO3结晶的相关理论理解以及对实际技术的应用仍然存在挑战,下文将从碳酸钙结晶过程以及动力学㊁热力学方面来深入探讨相关调控理论机制㊂3㊀结晶调控理论为了可控合成纳米碳酸钙,可以选择不同的制备方法以及添加剂,通过不断调整实验参数来控制结晶过程,最终得到特定晶型和形貌的碳酸钙产品㊂因此,了解碳酸钙的结晶生长过程是十分重要的㊂结晶过程实716㊀综合评述人工晶体学报㊀㊀㊀㊀㊀㊀第52卷际上受热力学和动力学的共同控制,因此动力学和热力学是控制结晶的理论基础,通过对基础规律的研究进一步认识调控的机理,最终实现晶型和形貌的调控[53]㊂3.1㊀碳酸钙结晶过程要实现对碳酸钙晶体的结晶调控,首先要明确结晶过程的各个阶段,以及各个阶段对产物晶型㊁形貌的影响㊂一般来说,结晶过程包括了竞争成核和晶体生长㊂碳酸钙是研究结晶矿物成核和结晶的一个重要模型体系,图4为碳酸钙的两种结晶路线㊂碳酸钙成核阶段的理论可分为经典成核理论和新型成核理论,经典成核理论基础源于热力学基本定律,溶液中的分子在热运动作用下发生相互碰撞,生成具有临界尺寸的晶核前体,这些晶核继续生长为最终晶体㊂而新型理论认为在结晶过程中先形成预成核离子团簇,预成核离子团簇PNCs 聚集进一步形成无定形碳酸钙(amorphous calcium carbonate,ACC)前驱体,最后ACC 转化成为矿物晶体[54]㊂晶体生长阶段的理论可以分为平衡生长理论和晶面生长理论㊂晶体的平衡态理论认为,晶体最终会生长为稳定㊁平衡的形态,而一个晶体上所有晶面的表面能之和最小的晶体形态是最稳定的,因此在晶体生长过程中趋向于使体系的表面能最小;晶面生长理论主要讨论界面处的作用,目前存在几种典型模型用以解释晶面生长的过程㊂层生长模型认为从某一晶面开始生长,长满一层开始循环层列生长过程;螺旋生长模型认为各晶体层的生长同时进行,实际晶体表面产生的错位㊁缺陷成为倾斜螺旋生长起点;负离子配体生长基元模型可以用来解释许多同质异构体晶体的形成,生长环境的差异导致晶体生长基元的维度或结构产生不同,最终导致不同形态晶体的生成[55]㊂图4㊀碳酸钙结晶路线图[54]Fig.4㊀Calcium carbonate crystallization roadmap [54]3.2㊀动力学、热力学对结晶控制的影响碳酸钙晶体在热力学和动力学驱动下的结晶路径如图5所示,其中A 表示碳酸钙在热力学控制下的结晶路径,热力学研究物质变化过程的能量效应及反应的方向和限度,即有关平衡的规律,热力学决定了结晶的终态,是一个状态函数;B 表示在动力学控制下的结晶路径,动力学研究反应速率以及实现反应过程的具体步骤,动力学决定了亚稳态相向稳态相转化的方式和速率,是一个过程函数[56]㊂图5㊀热力学和动力学驱动下的结晶路径示意图[57]Fig.5㊀Schematic diagram of crystallization pathways driven by thermodynamics and kinetics [57]在碳化反应过程中,成核过程是控制晶型的关键步骤㊂在经典成核理论中将晶核形成能表示为体自由能和表面能两项,可以定量地表征成核速率随过饱和比或温度的变化规律,不同晶型的可控制备可能取决于过饱和度[55]㊂在新型成核理论中,只有当初始过饱和度很高时,热力学亚稳相ACC 才可能会产生,这一现象满足奥斯特瓦尔德阶段规则,亚稳相的形成通常在较高的过饱和度时获得,在动力学上是有利的,并先于热力学稳定相的形成[10]㊂含有羧基㊁羟基等不同官能团的添加剂能够诱导亚稳态多晶相的优先形成,有利于多晶型的制备[58]㊂晶体生长过程对形貌的影响较大,过饱和度低时,晶体的生长方式通常为螺旋生长;提高过饱和度时,层㊀第4期丁㊀羽等:电石渣可控制备多晶型㊁多形貌纳米碳酸钙的研究进展717㊀状生长方式逐渐占据主导地位;而在高饱和度的溶液中晶体表现为活性位点多的枝状生长方式[55]㊂溶液体系中的过饱和度差异使晶体中各个晶面的生长速率不同,而低表面能的晶面由于生长速度慢㊁晶面大的优势能够得到优先表达,从而导致晶体最终形貌的不同[59]㊂添加剂除了对晶型产生决定性的作用以外,还会在晶体生长过程中影响不同表面的表面能,从而对晶体的形貌起到一定的调控作用[60]㊂4㊀结语与展望本文综述了电石渣制备纳米碳酸钙的方法和结晶调控的研究进展,具体总结如下:对比分析不同体系下的制备方法,碳化法合成纳米碳酸钙是简便㊁环保和可控的方法,在工业上也得到广泛应用,被研究最多;在预处理过程中,酸性铵盐浸提能够获得较高的Ca2+转化率,具有巨大的发展潜力,并且通过浸提工艺的优化可以进一步提高转化率,在碳化反应过程中,工艺参数主要影响晶体的形貌和粒径,添加剂对晶型㊁形貌的影响较大;从热力学和动力学的角度出发,改变成核过程中的过饱和度有利于实现内部晶体结构调控,改变晶体生长方式能够实现晶体外部形貌调控㊂综合电石渣可控制备纳米碳酸钙的研究进展,提出以下几点展望:在制备方法的选择方面,大多数研究处于实验室阶段,有待产业化推广;选择电石渣等固体废弃物制备碳酸钙产品,与传统的原料石灰石相比,成分较为复杂,需要全面考虑杂质的去除和Ca2+的提取;如何有效控制纳米碳酸钙粒子的晶型㊁形貌等性质,目前还没有形成成熟的理论,需深入了解结晶学相关理论及各种影响因素的内在逻辑,实现调控碳酸钙结构的目标㊂参考文献[1]㊀CHENG J,ZHOU J H,LIU J Z,et al.Physicochemical characterizations and desulfurization properties in coal combustion of three calcium andsodium industrial wastes[J].Energy&Fuels,2009,23(5):2506-2516.[2]㊀李彦鑫,张金山,曹永丹,等.电石渣的理化性质表征及其应用研究[J].无机盐工业,2018,50(4):49-52.LI Y X,ZHANG J S,CAO Y D,et al.Characterization of physiochemical property of carbide slag and its application study[J].Inorganic Chemicals Industry,2018,50(4):49-52(in Chinese).[3]㊀YANG H,CAO J W,WANG Z,et al.Discovery of impurities existing state in carbide slag by chemical dissociation[J].International Journal ofMineral Processing,2014,130:66-73.[4]㊀董永刚,曹建新,刘㊀飞,等.电石渣理化性质的分析与表征[J].环境科学与技术,2008,31(9):95-98.DONG Y G,CAO J X,LIU F,et al.Analysis and characterization of physiochemical property of carbide slag[J].Environmental Science& Technology,2008,31(9):95-98(in Chinese).[5]㊀孔祥波.超微细无定形碳酸钙粉体的制备㊁改性及其应用[D].厦门:厦门大学,2017.KONG X B.The preparation,modification of superfine amorphous calcium carbonate and its application[D].Xiamen:Xiamen University,2017 (in Chinese).[6]㊀冯文华.纳米碳酸钙制备新工艺研究[D].上海:华东理工大学,2015.FENG W H.Study on preparing new technology for nano calcium 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高分子材料纳米二氧化硅外文文献翻译

纳米二氧化硅对成核、结晶和热塑性能的影响外文文献翻译(含：英文原文及中文译文)文献出处：Laoutid F, Estrada E, Michell R M, et al. The influence of nanosilica on the nucleation, crystallization andtensile properties of PP–PC and PP–PA blends[J]. Polymer, 2013, 54(15):3982-3993.英文原文The influence of nanosilica on the nucleation, crystallization andtensileproperties of PP–PC and PP–PA blendsLaoutid F, Estrada E, Michell R M, et alAbstractImmiscible blends of 80 wt% polypropylene (PP) with 20 wt% polyamide (PA) or polycarbonate (PC) were prepared by melt mixing with or without the addition of 5% nanosilica. The nanosilica produced a strong reduction of the disperse phase droplet size, because of its preferential placement at the interface, as demonstrated by TEM. Polarized Light Optical microscopy (PLOM) showed that adding PA, PC or combinations of PA-SiO2 or PC-SiO2 affected the nucleation density of PP. PA droplets can nucleate PP under isothermal conditions producing a higher nucleation density than the addition of PC or PC-SiO2. PLOM was found to be more sensitive to determine differences in nucleation than non-isothermal DSC. PP developed spherulites, whose growth was unaffected by blending, while its overall isothermal crystallizationkinetics was strongly influenced by nucleation effects caused by blending. Addition of nanosilica resulted in an enhancement of the strain at break of PP-PC blends whereas it was observed to weaken PP-PA blends. Keywords：Nanosilica，Nucleation，PP blends1 OverviewImmiscible polymer blends have attracted attention for decades because of their potential application as a simple route to tailor polymer properties. The tension is in two immiscible polymerization stages. This effect usually produces a transfer phase between the pressures that may allow the size of the dispersed phase to be allowed, leading to improved mixing performance.Block copolymers and graft copolymers, as well as some functional polymers. For example, maleic anhydride grafted polyolefins act as compatibilizers in both chemical affinities. They can reduce the droplet volume at the interface by preventing the two polymers from coalescing. In recent years, various studies have emphasized that nanofillers, such as clay carbon nanotubes and silica, can be used as a substitute for organic solubilizers for incompatible polymer morphology-stabilized blends. In addition, in some cases, nanoparticles in combination with other solubilizers promote nanoparticle interface position.The use of solid particle-stabilized emulsions was first discovered in 1907 by Pickering in the case of oil/emulsion containing colloidalparticles. In the production of so-called "Pickling emulsions", solid nanoparticles can be trapped in the interfacial tension between the two immiscible liquids.Some studies have attempted to infer the results of blending with colloidal emulsion polymer blends. Wellman et al. showed that nanosilica particles can be used to inhibit coalescence in poly(dimethylsiloxane)/polyisobutylene polymers. mix. Elias et al. reported that high-temperature silicon nanoparticles can migrate under certain conditions. The polypropylene/polystyrene and PP/polyvinyl acetate blend interfaces form a mechanical barrier to prevent coalescence and reduce the size of the disperse phase.In contrast to the above copolymers and functionalized polymers, the nanoparticles are stable at the interface due to their dual chemical nature. For example, silica can affect nanoparticle-polymer affinities locally, minimizing the total free energy that develops toward the system.The nanofiller is preferentially placed in equilibrium and the wetting parameters can be predicted and calculated. The difference in the interfacial tension between the polymer and the nanoparticles depends on the situation. The free-diffusion of the nanoparticle, which induces the nanoparticles and the dispersed polymer, occurs during the high shear process and shows that the limitation of the viscosity of the polymer hardly affects the Brownian motion.As a result, nanoparticles will exhibit strong affinity at the local interface due to viscosity and diffusion issues. Block copolymers need to chemically target a particular polymer to the nanoparticle may provide a "more generic" way to stabilize the two-phase system.Incorporation of nanosilica may also affect the performance of other blends. To improve the distribution and dispersion of the second stage, mixing can produce rheological and material mechanical properties. Silica particles can also act as nucleating agents to influence the crystallization behavior. One studies the effect of crystalline silica on crystalline polystyrene filled with polybutylene terephthalate (polybutylene terephthalate) fibers. They found a stable fibril crystallization rate by increasing the content of polybutylene terephthalate and silica. On the other hand, no significant change in the melt crystallization temperature of the PA was found in the PA/ABS/SiO2 nanocomposites.The blending of PP with engineering plastics, such as polyesters, polyamides, and polycarbonates, may be a useful way to improve PP properties. That is, improving thermal stability, increasing stiffness, improving processability, surface finish, and dyeability. The surface-integrated nano-silica heat-generating morphologies require hybrid compatibilization for the 80/20 weight ratio of the thermal and tensile properties of the blended polyamide and polypropylene (increasedperformance). Before this work, some studies [22] that is, PA is the main component). This indicates that the interfacially constrained hydrophobic silica nanoparticles obstruct the dispersed phase; from the polymer and allowing a refinement of morphology, reducing the mixing scale can improve the tensile properties of the mixture.The main objective of the present study was to investigate the effect of nanosilica alone on the morphological, crystalline, and tensile properties of mixtures of nanosilica alone (for mixed phases with polypropylene as a matrix and ester as a filler. In particular, PA/PC or PA/nano The effect of SiO 2 and PC/nanosilica on the nucleation and crystallization effects of PP as the main component.We were able to study the determination of the nucleation kinetics of PP and the growth kinetics of the particles by means of polarization optical microscopy. DSC measures the overall crystallization kinetics.Therefore, a more detailed assessment of the nucleation and spherulite growth of PP was performed, however, the effect of nanosilica added in the second stage was not determined. The result was Akemi and Hoffman. And Huffman's crystal theory is reasonable.2 test phase2.1 Raw materialsThe polymer used in this study was a commercial product: isotactic polypropylene came from a homopolymer of polypropylene. The Frenchformula (B10FB melt flow index 2.16Kg = 15.6g / 10min at 240 °C) nylon 6 from DSM engineering plastics, Netherlands (Agulon Fahrenheit temperature 136 °C, melt flow index 240 °C 2.16kg = 5.75g / 10min ) Polycarbonate used the production waste of automotive headlamps, its melt flow index = 5g / 10min at 240 °C and 2.16kg.The silica powder TS530 is from Cabot, Belgium (about 225 m/g average particle (bone grain) about 200-300 nm in length, later called silica is a hydrophobic silica synthesis of hexamethyldisilane by gas phase synthesis. Reacts with silanols on the surface of the particles.2.2 ProcessingPP_PA and PP-PC blends and nanocomposites were hot melt mixed in a rotating twin screw extruder. Extrusion temperatures range from 180 to 240 °C. The surfaces of PP, PA, and PC were vacuumized at 80°C and the polymer powder was mixed into the silica particles. The formed particles were injected into a standard tensile specimen forming machine at 240C (3 mm thickness of D638 in the American Society for Testing Materials). Prior to injection molding, all the spherulites were in a dehumidified vacuum furnace (at a temperature of 80°C overnight). The molding temperature was 30°C. The mold was cooled by water circulation. The mixture of this combination is shown in the table.2.3 Feature Description2.31 Temperature Performance TestA PerkineElmer DSC diamond volume thermal analysis of nanocomposites. The weight of the sample is approximately 5 mg and the scanning speed is 20 °C/min during cooling and heating. The heating history was eliminated, keeping the sample at high temperature (20°C above the melting point) for three minutes. Study the sample's ultra-high purity nitrogen and calibrate the instrument with indium and tin standards.For high temperature crystallization experiments, the sample cooling rate is 60°C/min from the melt directly to the crystal reaching the temperature. The sample is still three times longer than the half-crystallization time of Tc. The procedure was deduced by Lorenzo et al. [24] afterwards.2.3.2 Structural CharacterizationScanning electron microscopy (SEM) was performed at 10 kV using a JEOL JSM 6100 device. Samples were prepared by gold plating after fracture at low temperature. Transmission electron microscopy (TEM) micrographs with a Philips cm100 device using 100 kV accelerating voltage. Ultra-low cut resection of the sample was prepared for cutting (Leica Orma).Wide-Angle X-Ray Diffraction Analysis The single-line, Fourier-type, line-type, refinement analysis data were collected using a BRUKER D8 diffractometer with copper Kα radiation (λ = 1.5405A).Scatter angles range from 10o to 25°. With a rotary step sweep 0.01° 2θ and the step time is 0.07s. Measurements are performed on the injection molded disc.This superstructure morphology and observation of spherulite growth was observed using a Leica DM2500P polarized light optical microscope (PLOM) equipped with a Linkam, TP91 thermal stage sample melted in order to eliminate thermal history after; temperature reduction of TC allowed isothermal crystallization to occur from the melt. The form is recorded with a Leica DFC280 digital camera. A sensitive red plate can also be used to enhance contrast and determine the birefringence of the symbol.2.3.3 Mechanical AnalysisTensile tests were carried out to measure the stretch rate at 10 mm/min through a Lloyd LR 10 K stretch bench press. All specimens were subjected to mechanical tests for 20 ± 2 °C and 50 ± 3% relative humidity for at least 48 hours before use. Measurements are averaged over six times.3 results3.1 Characterization by Electron MicroscopyIt is expected that PP will not be mixed with PC, PA because of their different chemical properties (polar PP and polar PC, PA) blends with 80 wt% of PP, and the droplets and matrix of PA and PC are expectedmorphologies [ 1-4] The mixture actually observed through the SEM (see Figures 1 a and b).In fact, because the two components have different polar mixtures that result in the formation of an unstable morphology, it tends to macroscopic phase separation, which allows the system to reduce its total free energy. During shearing during melting, PA or PP is slightly mixed, deformed and elongated to produce unstable slender structures that decompose into smaller spherical nodules and coalesce to form larger droplets (droplets are neat in total The size of the blend is 1 ~ 4mm.) Scanning electron microscopy pictures and PP-PC hybrid PP-PA neat and clean display left through the particle removal at cryogenic temperatures showing typical lack of interfacial adhesion of the immiscible polymer blend.The addition of 5% by weight of hydrophobic silica to the LED is a powerful blend of reduced size of the disperse phase, as can be observed in Figures 1c and D. It is worth noting that most of the dispersed phase droplets are within the submicron range of internal size. The addition of nano-SiO 2 to PA or PC produces finer dispersion in the PP matrix.From the positional morphology results, we can see this dramatic change and the preferential accumulation at the interface of silica nanoparticles, which can be clearly seen in FIG. 2 . PP, PA part of the silicon is also dispersed in the PP matrix. It can be speculated that thisformation of interphase nanoparticles accumulates around the barrier of the secondary phase of the LED, thus mainly forming smaller particles [13, 14, 19, 22]. According to fenouillot et al. [19] Nanoparticles are mixed in a polymer like an emulsifier; in the end they will stably mix. In addition, the preferential location in the interval is due to two dynamic and thermodynamic factors. Nanoparticles are transferred to the preferential phase, and then they will accumulate in the interphase and the final migration process will be completed. Another option is that there isn't a single phase of optimization and the nanoparticles will be set permanently in phase. In the current situation, according to Figure 2, the page is a preferential phase and is expected to have polar properties in it.3.2 Wide-angle x-ray diffractionThe polymer and silica incorporate a small amount of nanoparticles to modify some of the macroscopic properties of the material and the triggered crystal structure of PP. The WAXD experiment was performed to evaluate the effect of the incorporation of silica on the crystalline structure of the mixed PP.Isotactic polypropylene (PP) has three crystalline forms: monoclinic, hexagonal, and orthorhombic [25], and the nature of the mechanical polymer depends on the presence of these crystalline forms. The metastable B form is attractive because of its unusual performance characteristics, including improved impact strength and elongation atbreak.The figure shows a common form of injection molding of the original PP crystal, reflecting the appearance at 2θ = 14.0, 16.6, 18.3, 21.0 and 21.7 corresponding to (110), (040), (130), (111) and (131) The face is an α-ipp.20% of the PA incorporation into PP affects the recrystallization of the crystal structure appearing at 2θ = 15.9 °. The corresponding (300) surface of the β-iPP crystal appears a certain number of β-phases that can be triggered by the nucleation activity of the PA phase in PP (see evidence The following nucleation) is the first in the crystalline blend of PA6 due to its higher crystallization temperature. In fact, Garbarczyk et al. [26] The proposed surface solidification caused by local shear melts the surface of PA6 and PP and forms during the injection process, promoting the formation of β_iPP. According to quantitative parameters, KX (Equation (1)), which is commonly used to evaluate the amount of B-crystallites in PP including one and B, the crystal structure of β-PP has 20% PP_PA (110), H(040) and Blends of H (130) heights (110), (040) and (130). The height at H (300) (300) for type A peaks.However, the B characteristic of 5 wt% silica nanoparticles incorporated into the same hybrid LED eliminates reflection and reflection a-ipp retention characteristics. As will be seen below, the combination of PA and nanosilica induces the most effective nucleatingeffect of PP, and according to towaxd, this crystal formation corresponds to one PP structure completely.The strong reductive fracture strain observations when incorporated into polypropylene and silica nanoparticles (see below) cannot be correlated to the PP crystal structure. In fact, the two original PP and PP_PA_SiO2 hybrids contain α_PP but the original PP has a very high form of failure when the strain value.On the other hand, PP-PC and PP-PC-Sio 2 blends, through their WAXD model, can be proven to contain only one -PP form, which is a ductile material.3.3 Polarized Optical Microscopy (PLOM)To further investigate the effect of the addition of two PAs, the crystallization behavior of PC and silica nanoparticles on PP, the X-ray diffraction analysis of its crystalline structure of PP supplements the study of quantitative blends by using isothermal kinetic conditions under a polarizing microscope. The effect of the composition on the nucleation activity of PP spherulite growth._Polypropylene nucleation activityThe nucleation activity of a polymer sample depends on the heterogeneity in the number and nature of the samples. The second stage is usually a factor in the increase in nucleation density.Figure 4 shows two isothermal crystallization temperatures for thePP nucleation kinetics data. This assumes that each PP spherulite nucleates in a central heterogeneity. Therefore, the number of nascent spherulites is equal to the number of active isomerous nuclear pages, only the nucleus, PP-generated spherulites can be counted, and PP spherulites are easily detected. To, while the PA or PC phases are easily identifiable because they are secondary phases that are dispersed into droplets.At higher temperatures (Fig. 4a), only the PP blend inside is crystallized, although the crystals are still neat PP amorphous at the observed time. This fact indicates that the second stage of the increase has been able to produce PP 144 °C. It is impossible to repeat the porous experiment in the time of some non-homogeneous nucleation events and neat PP exploration.The mixed PP-PC and PP-PC-SiO 2 exhibited relatively low core densities at 144 °C, (3 105 and 3 106 nuc/cm 3) suggesting that either PC nanosilica can also be considered as good shape Nuclear agent is used here for PP.On the other hand, PA, himself, has produced a sporadic increase in the number of nucleating events in PP compared to pure PP, especially in the longer crystallization time (>1000 seconds). In the case of the PP-PA _Sio 2 blend, the heterogeneous nucleation of PP is by far the largest of all sample inspections. All the two stages of the nucleating agent combined with PA and silica are best employed in this work.In order to observe the nucleation of pure PP, a lower crystallization temperature was used. In this case, observations at higher temperatures found a trend that was roughly similar. The neat PP and PP-PC blends have small nucleation densities in the PP-PC-SiO 2 nanocomposite and the increase also adds further PP-PA blends. The very large number of PP isoforms was rapidly activated at 135°C in the PP-PA nanoparticle nanometer SiO 2 composites to make any quantification of their numbers impossible, so this mixed data does not exist from Figure 4b.The nucleation activity of the PC phase of PP is small. The nucleation of any PC in PP can be attributed to impurities that affect the more complex nature of the PA from the PC phase. It is able to crystallize at higher temperatures than PP, fractional crystallization may occur and the T temperature is shifted to much lower values (see References [29-39]. However, as DSC experiments show that in the current case The phase of the PA is capable of crystallizing (fashion before fractionation) the PP matrix, and the nucleation of PP may have epitaxy origin.The material shown in the figure represents a PLOAM micrograph. Pure PP has typical α-phase negative spherulites (Fig. 5A) in the case of PP-PA blends (Fig. 5B), and the PA phase is dispersed with droplets of size greater than one micron (see SEM micrograph, Fig. 1) . We could not observe the spherulites of the B-phase type in PP-PA blends. Even according to WAXD, 20% of them can be formed in injection moldedspecimens. It must be borne in mind that the samples taken using the PLOAM test were cut off from the injection molded specimens but their thermal history (direction) was removed by melting prior to melting for isothermal crystallization nucleation experiments.The PA droplets are markedly enhanced by the nucleation of polypropylene and the number of spherulites is greatly increased (see Figures 4 and 5). Simultaneously with the PP-PA blend of silica nanoparticles, the sharp increase in nucleation density and Fig. 5C indicate that the size of the spherulites is very small and difficult to identify.The PP-PC blends showed signs of sample formation during the PC phase, which was judged by large, irregularly shaped graphs. Significant effects: (a) No coalesced PC phase, now occurring finely dispersed small droplets and (B) increased nucleation density. As shown in the figure above, nano-SiO 2 tends to accumulate at the interface between the two components and prevent coalescence while promoting small disperse phase sizes.From the nucleation point of view, it is interesting to note that it is combined with nanosilica and as a better nucleating agent for PP. Combining PCs with nanosilica does not produce the same increase in nucleation density.Independent experiments (not shown here) PP _ SiO 2 samplesindicate that the number of active cores at 135 °C is almost the same as that of PP-PC-SiO2 intermixing. Therefore, silica cannot be regarded as a PP nucleating agent. Therefore, the most likely explanation for the results obtained is that PA is the most important reason for all the materials used between polypropylene nucleating agents. The increase in nucleation activity to a large extent may be due to the fact that these nanoparticles reduce the size of the PA droplets and improve its dispersion in the PP matrix, improving the PP and PA in the interfacial blend system. Between the regions. DSC results show that nano-SiO 2 is added here without a nuclear PA phase.4 Conclusion5% weight of polypropylene/hydrophobic nanosilica blended polyamide and polypropylene/polycarbonate (80E20 wt/wt) blends form a powerful LED to reduce the size of dispersed droplets. This small fraction of reduced droplet size is due to the preferential migration of silica nanoparticles between the phases PP and PA and PC, resulting in an anti-aggregation and blocking the formation of droplets of the dispersed phase.The use of optical microscopy shows that the addition of PA, the influence of PC's PA-Sio 2 or PC-Sio 2 combination on nucleation, the nucleation density of PP polypropylene under isothermal conditions is in the following approximate order: PP <PP-PC <PP -PC-SiO 2<<PP-PA<<< PP-PA-SiO 2. PA Drip Nucleation PP Production of nucleation densities at isothermal temperatures is higher than with PC or PC Sio 2D. When nanosilica is also added to the PP-PA blend, the dispersion-enhanced mixing of the enhanced nanocomposites yields an intrinsic factor PP-PA-Sio2 blend that represents a PA that is identified as having a high nucleation rate, due to nanoseconds Silicon oxide did not produce any significant nucleation PP. PLOAM was found to be a more sensitive tool than traditional cooling DSC scans to determine differences in nucleation behavior. The isothermal DSC crystallization kinetics measurements also revealed how the differences in nucleation kinetics were compared to the growth kinetic measurements.Blends (and nanocomposites of immiscible blends) and matrix PP spherulite assemblies can grow and their growth kinetics are independent. The presence of a secondary phase of density causes differences in the (PA or PC) and nanosilica nuclei. On the other hand, the overall isothermal crystallization kinetics, including nucleation and growth, strongly influence the nucleation kinetics by PLOAM. Both the spherulite growth kinetics and the overall crystallization kinetics were successfully modeled by Laurie and Huffman theory.Although various similarities in the morphological structure of these two filled and unfilled blends were observed, their mechanical properties are different, and the reason for this effect is currently being investigated.The addition of 5% by weight of hydrophobic nano-SiO 2 resulted in breaking the strain-enhancement of the PP-PC blend and further weakening the PP-PA blend.中文译文纳米二氧化硅对PP-PC和PP-PA共混物的成核，结晶和热塑性能的影响Laoutid F, Estrada E, Michell R M, et al摘要80(wt%)聚丙烯与20(wt %)聚酰胺和聚碳酸酯有或没有添加5%纳米二氧化硅通过熔融混合制备不混溶的共聚物。

三种有机成核剂成核聚丙烯的非等温结晶动力学研究

1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. 第23卷第2期中国塑料Vol.23No.22009年2月CHINAPLASTICSFeb.2009三种有机成核剂成核聚丙烯的非等温结晶动力学研究罗筑12宋帅12于杰2田瑶珠12秦军23何敏121.贵州大学材料科学与冶金工程学院贵州贵阳5500032.国家复合改性聚合物材料工程技术研究中心贵州贵阳5500253.教育部喀斯特重点实验室贵州贵阳550003摘要:采用DSC研究了聚丙烯PP和三种有机成核剂成核的PP在不同的降温速率下的非等温结晶动力学。

用Avrami 方程对DSC的测试结果进行了分析。

结果表明三种有机透明成核剂能显著提高PP的结晶温度和结晶速率。

可以用修正Avrami方程的Jeziorny法来处理三种有机成核剂成核PP的非结晶等温结晶行为结果表明:三种有机透明成核剂成核PP的半结晶时间减少结晶动力学常数Zc增加结晶速率增加松香型成核剂能最快提高PP的结晶速率同一降温速率下三种有机成核透明剂成核PP的n值较纯PP减少结晶成核方式发生了改变。

关键词:聚丙烯松香成核剂山梨醇成核剂有机磷酸盐成核剂非等温结晶动力学中图分类号:TQ325.14文献标识码:B文章编号:10012927820090220079205StudyonNon2isothermalCrystallizitionKineticsofPolypro pyleneFilledwithThreeTypesofOrganicNucleatingAgentsLUOZhu12SONGShuai12YUJi e2TIANYao2zhu12QINJun23HEMin121.SchoolofMaterialsScienceandMetallurgicalEng ineeringGuizhouUniversityGuiyang550003China2.NationalCompositeModifiedPloymer MaterialsEngineeringResearchCenterGuiyang550025China3.KeyLaboratoryofKarstDrain ageMinistryofEducationGuiyang550003ChinaAbstract:Non2isothermalcrystallizationbeh aviorofpolypropylenesneatandcontainingthreetypesnucleatingagentwasstudiedusingdiffer entialscanningcalorimetryDSCwiththedataanalyzedwithJeziornymethod.Itshowedthatallth ethreenucleatingagentsincreasedthecrystallizationtemperatureandrateofPPindicatedbydecr easedt1/2andincreasedZc.Therosintypenucleatingagentwasproventobethemosteffective.In additionatsamecoolingratesthepresenceofnucleatingagentdecreasedthenvalueofPP.Keywo rds:polypropylenerosintypenucleatingagentsorbitolnucleatingagentorganicphosphoricacid nucleatingagentnon2isothermalcrystallizitionkinetics等规PP是高结晶性聚合物通常是不透明的。

水化热抑制剂对复合胶凝材料体系早期水化动力学的影响　

第42卷第8期2023年8月硅㊀酸㊀盐㊀通㊀报BULLETIN OF THE CHINESE CERAMIC SOCIETY Vol.42㊀No.8August,2023水化热抑制剂对复合胶凝材料体系早期水化动力学的影响曾柯林1,温东昌1,杨㊀蓉2,孙㊀涛2,王雷冲2,韩金龙3(1.中交路桥建设有限公司,北京㊀101100;2.中山市武汉理工大学先进工程技术研究院,中山㊀528400;3.珠海春禾新材料研究院有限公司,珠海㊀519000)摘要:本文研究了水化热抑制剂(TRI)对水泥-粉煤灰-矿渣复合胶凝材料早期水化过程㊂通过改变矿物掺合料在胶凝材料中的质量占比以及TRI 的掺量,研究了胶凝材料的水化特性,并基于Krstulovic-Dabic 水化动力学模型计算了反应速率常数㊁几何晶体生长指数等动力学参数㊂结果表明,矿物掺合料和TRI 复合使用会延缓胶凝材料水化并降低最大放热速率;复合胶凝材料的水化过程均有结晶成核与晶体生长㊁相边界反应以及扩散3个阶段,Krstulovic-Dabic 水化动力学模型能较好地模拟各复合胶凝材料的水化过程;矿物掺合料和TRI 会影响复合胶凝材料水化产物的结晶成核以及晶体生长,并降低复合胶凝材料各阶段的水化速率㊂关键词:水化热抑制剂;粉煤灰;矿渣;水化历程;水化动力学;Krstulovic-Dabic 模型中图分类号:TU528.42㊀㊀文献标志码:A ㊀㊀文章编号:1001-1625(2023)08-2712-10Effect of Temperature Rising Inhibitor on Early Hydration Kinetics of Composite Cementitious MaterialZENG Kelin 1,WEN Dongchang 1,YANG Rong 2,SUN Tao 2,WANG Leichong 2,HAN Jinlong 3(1.Road &Bridge International Co.,Ltd.,Beijing 101100,China;2.Wuhan University of Technology Advanced Engineering Technology Research Institute of Zhongshan City,Zhongshan 528400,China;3.Zhuhai Chunhe New Material Research Institute Co.,Ltd.,Zhuhai 519000,China)Abstract :The effect of temperature rising inhibitor (TRI)on early hydration process of cement-fly ash-slag composite cementitious material was studied.By changing mass proportion of mineral additives in gel materials and amount of TRI,the hydration characteristics of cementitious materials were measured.The reaction rate constant,geometric crystal growth index and other dynamic parameters were calculated based on the Krstulovic-Dabic model.The results show that mineral additives and TRI delay the time of hydration and reduce the maximum hydration rate of cementitious materials.The hydration process of composite cementitious material can involve three stages,i.e.nucleation and crystal growth,interactions at phase boundaries and diffusion.The hydration process can be predicted by Krstulovic-Dabic model well.Mineral additives and TRI affect the crystallization of nucleation and crystal growth,and reduce the hydration rate of composite cementitious material at every stage.Key words :temperature rising inhibitor;fly ash;slag;hydration process;hydration kinetics;Krstulovic-Dabic model 收稿日期:2023-03-03;修订日期:2023-06-06基金项目:2019年度中山市高端科研机构创新专项(2019AG010)作者简介:曾柯林(1985 ),男,高级工程师㊂主要从事公路桥梁工程的研究㊂E-mail:413907478@ 0㊀引㊀言我国跨海大桥中使用的大体积海工混凝土,其胶凝体系一般由水泥㊁粉煤灰和/或矿粉材料组成[1-3]㊂粉煤灰和矿粉玻璃体早期水化时,由于受到溶解-沉淀机制的影响,水化速率较小,因此通过单掺或复掺辅助胶凝材料替代部分水泥能缓解水泥矿相快速水化释放热量而造成混凝土内外温差的现象[4-5],从而抑制温度收缩造成的有害裂缝[6-9]㊂此外,还通过引入水化热抑制剂对水泥水化速率进行调控,在不影响强度发展第8期曾柯林等:水化热抑制剂对复合胶凝材料体系早期水化动力学的影响2713㊀的同时有效降低了水化温度并获得了足够的凝结时间㊂水化热抑制剂主要分为羟基类化合物和反应吸热型盐类抑制剂:前者是通过生成氢键并与水分子缔合后在水泥表面形成水膜,从而延缓水泥水化;后者主要是通过盐类溶解吸热,从而中和水化放热,降低总热㊂辜振睿等[8]研究了多羟基羧酸酯类水化热抑制剂对纯水泥体系的影响,结果表明该类水化热抑制剂能有效降低水泥早期的水化放热速率和峰值,降低早期强度,但是对后期强度没有影响;严宇[10]㊁秦媛[11]和陈炜一等[12]研究了淀粉基水化热抑制剂对掺25%(质量分数)粉煤灰胶凝材料的影响,发现该类水化热抑制剂对早期水化放热的抑制作用明显,会大幅度降低早期强度,但对后期强度影响较小㊂魏小胜等[13]研究了糊精类水化热抑制剂对水泥-粉煤灰体系的影响,结果表明该类水化热抑制剂能显著降低水化放热速率峰值,抑制水化反应,但抑制作用主要发生在水化前7d㊂以上研究表明矿物掺合料可以缓解水泥水化快速释放热量的情况,水化热抑制剂可以缓解水泥水化同时降低水化放热速率,二者均可减少混凝土内外温差,抑制温度收缩造成的有害裂缝㊂而目前对于水化热抑制剂是否会和双掺粉煤灰和矿粉胶凝材料体系产生复合变化特征的研究较少㊂因此,本文采用大体积混凝土中常用的矿粉-粉煤灰双矿物掺合料体系,研究水化热抑制剂对水泥-粉煤灰-矿渣复合胶凝材料体系早期水化的影响㊂应用动力学可用来研究各种化学㊁物理因素对化学反应速率的影响,通过控制反应条件和速率实现对胶凝材料凝结硬化的调控㊂国内外研究人员[14-15]从理论角度分析和总结了水泥基胶凝材料的水化过程,其中被广泛接受的是Krstulovic-Dabic水化模型㊂本文通过调整矿物掺合料在胶凝材料中的质量占比以及水化热抑制剂(temperature rising inhibitor,TRI)的质量掺量,探究了其对胶凝材料水化特性的影响,并应用Krstulovic-Dabic模型研究其对胶凝材料的水化机理和水化过程的影响,从而为TRI和矿物掺合料在海工大体积混凝土中的应用提供基础理论支撑㊂1㊀实㊀验1.1㊀原材料原材料包含P㊃II42.5水泥㊁I级粉煤灰以及S95级矿渣粉,分别由海螺水泥有限公司㊁珠海市粤珠环保技术有限公司以及粤裕丰钢铁有限公司生产,原材料的主要化学组成和基本物理性能如表1和表2所示㊂通过扫描电子显微镜(SEM)对三种原材料微观形貌进行表征,SEM照片如图1所示,水泥与矿渣呈不规则块状,粉煤灰呈光滑圆球状㊂三种原材料的颗粒粒径分布和通过率如图2所示㊂由图2可知,在这三种原材料中,粉煤灰颗粒相对较细,其中值粒径D50为2.42μm,矿渣和水泥的D50分别为4.58和8.67μm㊂采用的水化热抑制剂为中山市灵湾新材料有限公司生产的淀粉基类水化热抑制剂,其红外光谱如图3所示, 3440cm-1处的宽峰主要是由羟基( OH)的伸缩振动引起的,2870cm-1处的吸收峰是由淀粉的环状骨架振动引起的,1020和1100cm-1处的吸收峰是由C O基团振动引起的,879cm-1处的吸收峰是由C O C 基团伸缩振动引起的㊂根据FTIR谱显示,水化热抑制剂中存在大量的亲水性基团 OH㊂表1㊀原材料的主要化学组成Table1㊀Main chemical composition of raw materialsRaw materialMass fraction/%Al2O3SiO2Fe2O3CaO K2O TiO2SO3P2O5Na2O MgO F LOICement 6.4521.75 3.2458.020.740.51 2.470.250.14 2.25 3.80 Slag15.4530.60 1.0736.660.510.95 2.610.090.558.900.82 1.06 Fly ash32.5652.2 4.01 3.880.890.55 1.010.120.790.840.21 2.16表2㊀原材料的基本物理性能Table2㊀Basic physical properties of raw materialsProperty Cement Slag Fly ash Initial setting time/min157 Final setting time/min189 Standard consistency/%27Mass quality K 1.932714㊀水泥混凝土硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷续表Property Cement Slag Fly ash Basicity coefficient M 00.99 Activity index at 3d /% 86.374.9Activity index at 7d /% 85.279.0Activity index at 28d /% 97.195.1图1㊀水泥㊁粉煤灰和矿渣的SEM 照片Fig.1㊀SEM images of cement,fly ash andslag 图2㊀水泥㊁粉煤灰和矿渣的颗粒粒径分布和通过率Fig.2㊀Particle size distribution and passing percent of cement,fly ash andslag 图3㊀水化热抑制剂的FTIR 谱Fig.3㊀FTIR spectrum of TRI1.2㊀测试方法净浆配合比如表3所示㊂采用TAM 等温量热仪连续测定净浆在20ħ环境温度下水化72h 后的放热速率和累积放热量㊂为了保持浆体温度和环境温度相同,在搅拌前将胶凝材料和水放置在同温度下的恒温箱中,净浆搅拌均匀后立即放入等温量热仪设备中㊂根据测试的水化热数据,采用Knudson [16]提出的水化动力学公式(1)求出最大放热量Q max ㊂1/Q (t )=1/Q max +t 50/Q max (t -t 0)(1)式中:t 0为加速期开始时间,t 50为半衰期,Q (t )为胶凝材料从加速期开始水化t 时所放出的热量,Q max 为胶凝材料在ɕ龄期时的水化放热量(即最大放热量)㊂采用耐驰热重分析仪对样品进行热分析㊂TG 测试条件:30~1000ħ,氮气气氛,升温速度为10ħ/min㊂DTG 为TG 曲线对温度的一阶导数㊂为了终止样品水化,对样品进行如下处理:先用异丙醇浸第8期曾柯林等:水化热抑制剂对复合胶凝材料体系早期水化动力学的影响2715㊀泡样品1d,然后更换新异丙醇溶液再次浸泡半天,最后将样品置于真空干燥器中连续抽真空[17-18]㊂为修正其他水化产物和碳化对结果的影响,采用切线法计算Ca(OH)2(CH)的含量[19-20]㊂采用Bruker D8X 射线衍射仪(XRD)定性测试各样品在1㊁3和28d 龄期时的物相组成,样品终止水化方式与上述测试相同㊂采用Phenom 扫描电子显微镜观察各样品在1㊁3和28d 龄期时的微观形貌,样品终止水化方式与上述测试相同㊂表3㊀净浆配合比Table 3㊀Mix proportion of pasteSampleWater-binder ratio Mass fraction /%Cement Fly ash Slag TRI C 0.33100 CFASG 0.33402535 CFASG-T0.5%0.334025350.5CFASG-T1.0%0.33402535 1.0CFASG-T1.5%0.33402535 1.5㊀㊀Note:C means that cementitious material is cement;CFASG means that cementitious material is 40%cement,35%slag and 25%(all are mass fraction)fly ash;T x %means that the mass fraction of TRI is x %of cementitious material.2㊀结果与讨论2.1㊀水化放热特性图4为水化温度为20ħ时复合胶凝材料的水化放热特性,表4为水化温度为20ħ时复合胶凝材料的水化放热特征值㊂由图4(a)和表4可知,矿物掺合料取代部分水泥后,诱导期略延长,达到最大放热速率的时间增加,同时最大水化放热速率明显降低,由13.30J㊃g -1㊃h -1降低到6.66J㊃g -1㊃h -1,降低了49.9%㊂当进一步掺入不同比例TRI 后,所有胶凝材料的诱导期以及达到最大放热速率的时间明显延长㊂与未掺TRI 组相比,当TRI 的掺量(质量分数)为1.5%时,经过65.56h 才达到最大水化速率,延缓了近41.56h㊂由此可知,矿物掺合料主要是降低胶凝材料的早期水化放热速率,而TRI 则能延缓早期水化㊂由图4(b)和表4可知,随着矿物掺合料和TRI 的掺入,早期的总水化热量均减小㊂与C 相比,CFASG 水化3d 的累积放热量由283.6J /g 降到187.4J /g,降低了33.9%;最终的放热量Q max 由328.9J /g 降到237.5J /g,降低了27.8%㊂与CFASG 相比,CFASG-T1.5%水化3d 的累积放热量由187.4J /g 降到120.6J /g,降低了35.6%;而最终的放热量Q max 几乎没有变化㊂这说明矿物掺合料和TRI 均能降低胶凝材料的总水化放热量,其中矿物掺合料是降低胶凝材料水化放热量的主要因素,而TRI 主要是延缓胶凝材料早期水化,对最终的放热量基本没影响㊂图4㊀水化温度为20ħ时复合胶凝材料的水化放热特性Fig.4㊀Characteristics of hydration heat evolution of composite cementitious materials with hydration temperature at 20ħ2716㊀水泥混凝土硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷表4㊀水化温度为20ħ时复合胶凝材料的水化放热特征值Table 4㊀Characteristic values of hydration heat evolution of composite cementitious materialswith hydration temperature at 20ħSampleTime of second heat evolution peak t 2/h Rate of second heat evolution peak q max /(J㊃g -1㊃h -1)Total heat evolution Q /(J㊃g -1)24h 48h 72h Q max C 10.8113.30212.9268.5283.6328.9CFASG 14.00 6.66123.0162.4187.4237.5CFASG-T0.5%18.16 4.4690.1146.6171.8240.4CFASG-T1.0%31.83 4.6353.8128.4156.1235.3CFASG-T1.5%65.56 4.9438.440.9120.6233.12.2㊀相组成和微观结构图5为不同复合胶凝材料水化1㊁3和28d 的XRD 谱㊂由图5(a)可知,水化1d 时,CFASG 已生成了Ca(OH)2和钙矾石等产物㊂随着TRI 掺量的增加,水化产物的衍射峰强度逐渐降低,对于TRI 掺量为1.5%的CFASG-T1.5%而言,水化产物衍射峰几乎消失,这表明TRI 能显著降低胶凝材料在1d 时的水化程度㊂由图5(b)可知,水化3d 时,各胶凝材料的水化产物衍射峰强度均较高,其中CFASG-T0.5%的水化产物衍射峰强度与CFASG 相差不多㊂随着水化的进行,当水化龄期为28d 时,对于各TRI 掺量的胶凝材料,硬化浆体中水化产物的衍射峰强度几乎相同,这表明水化热抑制剂对胶凝材料的水化抑制作用主要发生在早期,随着龄期的增长,掺TRI 的胶凝材料水化程度将逐渐恢复至与未掺TRI 胶凝材料时相近㊂值得注意的是,水化1d 时CFASG 水化产物衍射峰强度明显低于C 的衍射峰强度,随着水化的进行,CFASG 水化产物衍射峰强度与C 的衍射峰强度差距逐渐减小,但始终低于C㊂图5㊀复合胶凝材料硬化浆体的XRD 谱Fig.5㊀XRD patterns of hardening slurry of composite cementitious materials 由于胶凝材料的水化产物受热会分解,并且每种水化产物的分解温度不同,因此可以通过热重分析来研究水化产物㊂室温到300ħ为水化硅酸钙(C-S-H)㊁水化铝酸钙㊁单硫型水化硫铝酸钙(AFm)㊁高硫型水化硫铝酸钙(AFt)等水化产物失水分解,370~450ħ为CH 的分解[19]㊂图6为复合胶凝材料的水化产物在1㊁3和28d 的TG 和DTG 曲线(HC 为水化碳铝酸钙,MC 为碳酸酯),表5为切线法计算的复合凝胶材料中Ca(OH)2含量㊂当水化1和3d 时,300ħ前C 硬化浆体的失重速率显著大于CFASG,而CFASG 硬化浆体的失重速率明显大于掺TRI 样品,表明C 中水化产物含量大于CFASG,而CFASG 的水化产物含量大于掺TRI 的复合胶凝材料;在370~450ħ,C 硬化浆体的失重速率显著大于CFASG,CFASG 硬化浆体的失重速率仍然大于掺TRI 样品,表明C 中CH 含量大于CFASG,CFASG 中CH 含量大于掺TRI 的复合胶凝材料,这与通过切线法计算得到的CH 含量趋势一致㊂当水化龄期为28d 时,掺TRI 和未掺TRI 的复合胶凝材料的TG 和DTG 曲线几乎重叠,并且反应生成的CH 含量也几乎相等,再次证明TRI 不会影响复合胶凝材料的最终水化程度㊂图7为C㊁CFASG 和CFASG-T1.5%不同龄期硬化浆体的SEM 照片㊂水化1d 时,C 中的颗粒表面已覆第8期曾柯林等:水化热抑制剂对复合胶凝材料体系早期水化动力学的影响2717㊀盖了绒毛状的C-S-H 凝胶(见图7(a));CFASG 中只有水泥颗粒表面生成绒毛状的C-S-H 凝胶(见图7(d)),但由于水泥只占总粉料的40%,生成的C-S-H 凝胶含量明显少于C 中生成的C-S-H 凝胶含量;而CFASG-T1.5%中的颗粒则几乎未发生水化反应(见图7(e))㊂当水化3d 时,样品中的水泥和矿粉颗粒均发生了水化,且矿粉水化程度不及水泥,而粉煤灰未明显水化㊂当龄期达到28d 时,样品均呈现出致密的形貌㊂结果表明,水化热抑制剂对于硬化浆体微观结构的负面作用主要发生在早龄期;随着水化的进行,水化热抑制剂对浆体微观结构的负面影响已不明显㊂图6㊀复合胶凝材料硬化浆体的TG 和DTG 曲线Fig.6㊀TG and DTG curves of hardening slurry of composite cementitious materials表5㊀切线法计算的复合凝胶材料中Ca (OH )2含量Table 5㊀Ca (OH )2content of composite cementitious materials calculated by tangent methodTime /d Mass fraction /%C CFASG CFASG-T0.5%CFASG-T1.0%CFASG-T1.5%111.52 4.94 3.37 2.28 1.85314.497.24 6.95 5.87 4.872817.617.907.747.907.822718㊀水泥混凝土硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷图7㊀复合凝胶材料硬化浆体的SEM照片Fig.7㊀SEM images of hardening slurry of composite cementitious materials2.3㊀水化放热动力学分析Krstulovic-Dabic模型认为水泥基胶凝材料的水化由结晶成核与晶体生长(NG)㊁相边界反应(I)和扩散(D)三个反应组成[15]㊂结晶成核与NG阶段微分式如(2)所示㊂dα/d t=F1(α)=Kᶄ1n(1-α)[-ln(1-α)](n-1)/n(2) I阶段微分式如(3)所示㊂dα/d t=F2(α)=Kᶄ2㊃3(1-α)2/3(3) D阶段微分式如(4)所示㊂dα/d t=F3(α)=Kᶄ3㊃3(1-α)2/3/[2-2(1-α)1/3](4)式中:α为水化程度,n为反应级数,t为水化时间,Kᶄi为表观反应速率常数,F i(α)为反应机理函数㊂本文将复合胶凝材料视为均质体进行处理,并以整个复合胶凝材料为研究对象进行动力学分析㊂图8为复合胶凝材料在20ħ时的水化反应速率曲线,结果表明所研究材料的水化动力学过程均经历NG-I-D 阶段㊂由图8(a)可知,模型模拟的各阶段曲线均能较好地拟合纯水泥实际水化热速率㊂图8(b)为复合胶凝材料的水化过程,该过程由快速的水泥水化和较慢的矿物掺合料水化组成,在水化最初的几小时内,复合胶凝材料中水泥快速水化生成了大量水化产物C-S-H,并伴随着孔溶液pH值的快速增长,当CH达到过饱和后形成稳定晶核[9],粉煤灰和矿粉由于早期水化反应速率较慢,因此主要发挥物理填充作用,增大复合胶凝材料的有效水胶比,并为水化产物提供初始成核点,故其水化的NG阶段模拟效果好㊂由于矿物掺合料占总胶凝材料的60%,矿粉水化发生在I阶段,粉煤灰的火山灰反应产生的热效应在D阶段,从而使得I和D阶段的模拟误差增大,但仍能较好地反映实际的水化㊂由图8(b)~(e)可知,复合胶凝材料掺入水化热抑制剂后,相边界反应控制的时间增加,这是由于水化热抑制剂对水泥和矿物掺合料具有延缓效果㊂表6为不同TRI掺量的复合凝胶材料的动力学参数㊂其中α1为反应控制机制由NG转变为I时的水化程度,α2为反应控制机制由I转变为D时的水化程度㊂由表6可知,矿物掺合料取代部分水泥后,n值略微增加,说明大掺量复掺粉煤灰和矿粉对水化产物的产生过程影响不大㊂而在复合胶凝材料中掺入水化热抑第8期曾柯林等:水化热抑制剂对复合胶凝材料体系早期水化动力学的影响2719㊀制剂,n 值显著增加,表明水化热抑制剂会大大影响复合胶凝材料水化产物的结晶成核以及晶体生长[21]㊂图8㊀20ħ时复合胶凝材料的水化反应速率曲线Fig.8㊀Hydration rate curves of composite cementitious materials at 20ħ表6㊀不同TRI 掺量的复合凝胶材料的动力学参数Table 6㊀Kinetic parameters of composite cementitious materials with different TRI contentSamplen K ᶄ1K ᶄ2K ᶄ3Kinetic α1α2C 1.95550.054960.014870.00297NG-I-D 0.2100.387CFASG 2.00640.045210.010190.00132NG-I-D 0.1170.182CFASG-T0.5% 2.67670.033230.006770.00101NG-I-D 0.0950.286CFASG-T1.0% 3.19880.031030.006680.00091NG-I-D 0.1060.180CFASG-T1.5% 4.63150.024550.006300.00085NG-I-D 0.1300.253各复合凝胶材料的反应速率K ᶄ1约是K ᶄ2的3~5倍,约是K ᶄ3的15~35倍㊂结果表明,在常温时NG 过程的反应速率明显比I 和D 过程的反应速率大㊂这是因为在NG 过程中,水泥发生自催化反应,迅速生成水化产物㊂与纯水泥胶凝材料相比,掺有矿粉和粉煤灰的复合胶凝材料的K ᶄ1㊁K ᶄ2和K ᶄ3值均减小㊂这是因为水泥被矿物掺合料取代后,CH 的总生成量降低且被矿物掺合料的火山灰反应消耗,延长了达到过饱和状态的时间,因此析晶沉淀速率受到影响㊂同时,水泥水化生成的钙离子含量减小,从而使扩散到矿物掺合料表面的钙离子含量减小[21]㊂另外,由于D 阶段浆体较致密,使得水化速率降低㊂与CFASG 相比,掺入水化热抑制剂后其他凝胶材料的K ᶄ1㊁K ᶄ2和K ᶄ3值均减小,这是因为水化热抑制剂在水泥水化早期能持续抑制C-S-H 凝胶的成核过程,进而影响C-S-H 凝胶成核生长,CH 的生成量随之降低,从而进一步抑制矿物掺合料的火山灰反应[11]㊂矿物掺合料取代水泥后,α1和α2减小,说明其在较低水化程度下发生了NG ңI 和I ңD 反应控制机制的转变㊂这是因为水泥被矿物掺合料取代后,CH 生成量随之降低,矿物掺合料受碱性离子激发发生反应,使得材料在较低水化程度下发生反应机制的转变㊂在复合胶凝材料中掺入水化热抑制剂后,α1先减小再增大,表明NG 阶段的水化程度先减小后增大㊂由α2可知,水化热抑制剂会抑制材料的D 阶段反应程度㊂2720㊀水泥混凝土硅酸盐通报㊀㊀㊀㊀㊀㊀第42卷3㊀结㊀论1)粉煤灰㊁矿渣和TRI三种材料复合使用时能有效缓解胶凝材料早期集中放热现象,其中粉煤灰和矿渣主要降低胶凝材料的最大放热速率,TRI延缓水化反应㊂2)粉煤灰㊁矿渣和TRI三种材料复合使用时也会影响水化放热量,矿粉和粉煤灰会降低胶凝材料的早期和最终的水化放热量,而TRI只会降低早期水化放热量,但对最终水化放热量没有任何影响㊂3)采用Krstulovic-Dabic水化动力学模型计算的曲线能较好地分段模拟不同掺量TRI的水泥-粉煤灰-矿粉复合胶凝材料体系的实际水化速率曲线;其水化动力学过程均可表示为NG㊁I和D3个阶段,且水化机理均为NGңIңD㊂4)矿渣㊁粉煤灰和TRI三种材料复合使用会影响胶凝材料水化产物的结晶成核以及晶体生长,即动力学参数n增大,其中TRI影响最明显;同时会降低复合胶凝材料各阶段的水化速率,即Kᶄ1㊁Kᶄ2和Kᶄ3减小㊂参考文献[1]㊀谭㊀昱,陈儒发,谭逸波,等.港珠澳大桥低温升抗裂C45承台大体积混凝土研究与应用[J].公路,2016,61(5):282-288.TAN Y,CHEN R F,TAN Y B,et al.Research and application of C45mass concrete with low temperature rise and crack resistance for bearing platform of Hong Kong-Zhuhai-Macao bridge[J].Highway,2016,61(5):282-288(in Chinese).[2]㊀王冬松.杭州湾跨海大桥高性能海工混凝土配合比设计[J].公路,2009,54(7):299-303.WANG D S.Mix proportion 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Chinese).[6]㊀朱鹏飞,宫经伟,唐新军.大体积混凝土胶凝材料体系水化放热规律研究[J].长江科学院院报,2018,35(6):111-116.ZHU P F,GONG J W,TANG X w of hydration heat of mass concrete cementitious materials[J].Journal of Yangtze River Scientific Research Institute,2018,35(6):111-116(in Chinese).[7]㊀SHI M X,WANG Q,ZHOU Z parison of the properties between high-volume fly ash concrete and high-volume steel slag concrete undertemperature matching curing condition[J].Construction and Building Materials,2015,98:649-655.[8]㊀辜振睿,刘晓琴,王海龙.水化热抑制剂对水泥水化的调控作用[J].新型建筑材料,2021,48(8):47-50+54.GU Z R,LIU X Q,WANG H L.Regulating effect of hydration heat inhibitor on cement hydration process[J].New Building Materials,2021, 48(8):47-50+54(in Chinese).[9]㊀张㊀浩.水化热抑制剂对水泥基材料水化行为的影响[D].南京:东南大学,2021.ZHANG H.Effct of temperature rising inhibitor on hydration behaviour of cementitious materials[D].Nanjing:Southeast University,2021(in Chinese).[10]㊀严㊀宇.水化温升抑制材料调控水泥水化放热历程的作用机制[D].南京:东南大学,2020.YAN Y.Mechanism study of temperature rise inhibitor affecting the exothermic process of cement hydration[D].Nanjing:Southeast University, 2020(in Chinese).[11]㊀秦㊀媛.水化温升抑制材料对水泥-粉煤灰/矿粉性能的影响规律及作用机制[D].南京:东南大学,2021.QIN Y.Influence law and mechanism of hydration temperature rise inhibiting materials on properties of cement-fly ash/mineral powder[D].Nanjing:Southeast University,2021(in Chinese).[12]㊀陈炜一,周予启,李㊀嵩,等.水化热抑制剂对水泥-粉煤灰胶凝材料水化和混凝土性能的影响[J].硅酸盐学报,2021,49(8):1609-1618.CHEN W Y,ZHOU Y Q,LI S,et al.Impact of temperature rising inhibitor on hydration of cement-fly ash cementitious materials and performance of concrete[J].Journal of the Chinese Ceramic Society,2021,49(8):1609-1618(in Chinese).㊀第8期曾柯林等:水化热抑制剂对复合胶凝材料体系早期水化动力学的影响2721 [13]㊀魏小胜,肖莲珍,李宗津.采用电阻率法研究水泥水化过程[J].硅酸盐学报,2004,32(1):34-38.WEI X S,XIAO L Z,LI Z J.Study on hydration of Portland cement using an electrical resistivity method[J].Journal of the Chinese Ceramic Society,2004,32(1):34-38(in Chinese).[14]㊀孔祥明,卢子臣,张朝阳.水泥水化机理及聚合物外加剂对水泥水化影响的研究进展[J].硅酸盐学报,2017,45(2):274-281.KONG X M,LU Z C,ZHANG C Y.Recent development on understanding cement hydration mechanism and effects of chemical admixtures on cement hydration[J].Journal of the Chinese Ceramic Society,2017,45(2):274-281(in Chinese).[15]㊀SCRIVENER K L,NONAT A.Hydration of cementitious materials,present and future[J].Cement and Concrete Research,2011,41(7):651-665.[16]㊀KNUDSEN T.On particle size distribution in cement hydration[C]//7th International Congress on the Chemistry of Cement.1980(2):170-175.[17]㊀ZHANG J,SCHERER G parison of methods for arresting hydration of cement[J].Cement and Concrete Research,2011,41(10):1024-1036.[18]㊀史才军,元㊀强.水泥基材料测试分析方法[M].北京:中国建筑工业出版社,2018:131.SHI C J,YUAN Q.Test and analysis method of cement-based materials[M].Beijing:China Construction Industry Press,2018:131(in Chinese).[19]㊀SMITH B J,ROBERTS L R,FUNKHOUSER G P,et al.Reactions and surface interactions of saccharides in cement slurries[J].Langmuir,2012,28(40):14202-14217.[20]㊀KIM T,OLEK J.Effects of sample preparation and interpretation of thermogravimetric curves on calcium hydroxide in hydrated pastes and mortars[J].Transportation Research Record:Journal of the Transportation Research Board,2012,2290(1):10-18.[21]㊀BEZJAK A.Nuclei growth model in kinetic analysis of cement hydration[J].Cement and Concrete Research,1986,16(4):605-609.。

不同形态石英玻璃的析晶动力学研究

石英玻璃及其复合材料具有一系列优异性能, 广泛用于重要的高技术领域如精密仪器, 通讯和航天工业中作为光学镜片, 光导线路 , 通讯窗口和防热材料 . 然而由于石英玻璃处于热力学不稳定状态, 并且其结构与方石英最为接近 , 所以一旦析晶 , 往往以方石英形式析出 . 方石英的高低温转变时较大的体积效应严重地制约石英玻璃材料的制备和使用. 正因如此, 研究石英玻璃的析晶问题
Crystallization kinetics of different morphologies of fused silica glass
WEN Guang wu, LEI T ing quan, ZHOU Yu
( School of Materials Science and Engineering, Harbin Institute of T echnology, Harbin 150001, China)
Crystallinity variation vs heat- treatment temperature for
至于析晶量随温度变化出现极值的情况 , 对于块状玻璃, Wagstaff 等 [ 8] 曾报道, 在 1 680 析晶速
第 1期
温广武 , 等 : 不同形态石英玻璃的析晶动力学研究
glass powders, ( 3) Silica glass fibers
晶量 I b < I p < I f; ∃ 粉末和纤维的析晶量 - 温度曲线在 1 450 时出现峰值, 而块状则没有 . 可见块状石英玻璃的析晶倾向明显地低于粉末和纤维. 这是因为石英玻璃析晶往往是从表面开始( 见 2. 3) , 由表及里进行, 因此具有较高比表面积、较高表面活性的粉末和纤维 , 成核- 长大势垒较低, 因此析晶能力高于块状石英玻璃. 纤维具有最大析晶倾向的原因除了比表面积大以外 , 其较高的杂质含量和较低的氧空位浓度的重要因素.

Kinetics of non-isothermal crystallization(非等温结晶owaza法)

perature at t, that at r and the temperature above which the process cannot proceed. The number j of the nuclei per unit volume or area which form from Tm to 0 is given by
Kinetics of nollization
T. OZAWA Non-isothermal kinetics of the process of nucleation and its growth are derived by extending Avrami's equation. Kinetic analysis of the thermoanalytical data of the process is also described and applied to DSC curves of crystallization obtained by cooling poly(ethylene terephthalate) at constant rates. Crystallization is thought to proceed by nuclei being formed randomly and growing in three-dimensions. INTRODUCTION ALTHOUGH THE kinetics of isothermal process have been thoroughly studied, few attempts to elucidate the kinetics of dynamic, non-isothermal processes have been made. Recently Flynn 1 proposed non-isothermal kinetics for simple homogeneous chemical reactions and the present author also published papers on the subject 2,3. Practical processes such as industrial synthesis proceed under dynamic, non-isothermal conditions and not under isothermal conditions. It is necessary to extend the isothermal kinetics to non-isothermal dynamic kinetics for various types of processes. One of the kinetic studies of importance is the process of growth and nucleation; crystallization is a typical part of nucleation and growth. Avrami's equation is proposed for these processes 4-7, and many processes such as tinning and galvanizing were found to follow Avrami's kinetic equation. Crystallization of high polymers also follows Avrami's equation 8, and in practical processes including melt-spinning of synthetic fibres and fabrication of crystalline polymers crystallization of the polymer occurs under nonisothermal conditions. However there have been no kinetic investigations of these processes. Kinetic investigations have been carried out isothermally, since isothermal kinetics are simpler than non-isothermal kinetics, but isothermal measurement is only possible when the thermal response time of the measured system is small compared with the rate of the process. Otherwise the process begins to occur before the system reaches the desired temperature. In this case, one should use a thermoanalytical method in which observations of the sample are made under a constant rate of heating or cooling. Such a situation seems to be encountered in crystallization under high pressure. For these cases the method of kinetic analysis of thermoanalytical data should be developed. In this paper, non-isothermal kinetics of the process of nucleation and growth are investigated theoretically, extending Avrami's equation to the non-isothermal situation, and a method of kinetic analysis of thermoanalytical data of the process is derived from the theory. The theory and the method obtained have been applied to the thermoanalytical data of the crystallization of poly(ethylene terephthalate). 150

纳米氧化镱对熔融石英析晶动力学机制的影响

第50卷第1期2021年1月人㊀工㊀晶㊀体㊀学㊀报JOURNAL OF SYNTHETIC CRYSTALS Vol.50㊀No.1January,2021纳米氧化镱对熔融石英析晶动力学机制的影响谷莹蕾1,2,闫亚汐1,卜景龙2,马㊀超3,王志发2(1.华北理工大学轻工学院,唐山㊀064000;2.华北理工大学材料科学与工程学院,河北省无机非金属材料重点实验室,唐山㊀063210;3.唐山时创高温材料股份有限公司,唐山㊀064000)摘要:本文研究引入纳米氧化镱对熔融石英析晶机制及动力学过程的影响㊂通过X 射线衍射仪(XRD)测试结果分析了纳米氧化镱的引入对熔融石英陶瓷析晶率的影响,采用动力学方法分析了纳米氧化镱的引入对熔融石英陶瓷析晶机制的影响,同时探讨了其等温析晶动力学过程㊂研究表明,熔融石英陶瓷的晶粒向二维兼有一维及三维的方式生长,引入纳米氧化镱的熔融石英陶瓷的晶粒则向二维兼有三维的方式生长;试样B 和试样Y 的析晶活化能E 分别为874kJ /mol 和1188kJ /mol㊂在熔融石英陶瓷中引入纳米氧化镱能够大幅度减少SiO 2玻璃脱玻为方石英的活性成核点 ,增加玻璃表面结构稳定性,提高析晶活化能,大大降低熔融石英的析晶率㊂关键词:熔融石英;纳米氧化镱;析晶;动力学;活化能中图分类号:TQ174.1㊀㊀文献标志码:A ㊀㊀文章编号:1000-985X (2021)01-0144-07Effect of Nano-Yb 2O 3on Crystallization Kinetics Mechanism of Fused QuartzGU Yinglei 1,2,YAN Yaxi 1,BU Jinglong 2,MA Chao 3,WANG Zhifa 2(1.Qinggong College,North China University of Science and Technology,Tangshan 064000,China;2.Hebei Provincial Key Laboratory of Inorganic Nonmetallic Materials,College of Materials Science and Engineering,North China University of Science and Technology,Tangshan 063210,China;3.Tangshan Strong Refractories Co.,Ltd.,Tangshan 064000,China)Abstract :The effect of nano-Yb 2O 3on the crystallization mechanism and kinetics of fused quartz were studied.The effect of nano-Yb 2O 3on crystallization ratio of fused quartz ceramics was studied by means of XRD,and the effect of nano-Yb 2O 3on the crystallization mechanism of fused quartz ceramics was studied by kinetic method,meanwhile,the isothermal crystallization kinetics of two kinds of fused quartz ceramics were discussed.The results show that the grain growth mode of fused quartz ceramics is two-dimensional growth accompanied by one-dimensional and three-dimensional growth,while the grain growth mode of fused quartz ceramics with nano-Yb 2O 3is two-dimensional accompanied by three-dimensional growth.The activation energy E of samples B and samples Y are 874kJ /mol and 1188kJ /mol,respectively.With the introduction of nano-Yb 2O 3in fused quartz ceramics,the "active nucleation point"of SiO 2glass for cristobalite reduce greatly,the stability of the glass surface structure increases,the crystallization activation energy increases,and the crystallization ratio of fused quartz reduces greatly.Key words :fused quartz;nano-Yb 2O 3;crystallization;kinetic;activation energy㊀㊀收稿日期:2020-10-01㊀㊀基金项目:国家自然科学基金(51072046)㊀㊀作者简介:谷莹蕾(1986 ),女,河北省人,讲师㊂E-mail:490557762@0㊀引㊀㊀言熔融石英陶瓷具有热膨胀系数小㊁导热率低㊁电绝缘性好㊁热震稳定性优异㊁耐玻璃及金属液侵蚀等特点,广泛应用于冶金㊁电力㊁航天等领域[1]㊂然而熔融石英在高温使用下易析晶为方石英,同时伴随较大的体积效应,使得其热膨胀系数升高㊁强度降低,造成开裂,大大降低了材料的使用安全性㊂因此,对熔融石英的析晶行为研究变得极为重要㊂国内外学者针对熔融石英陶瓷析晶行为和析晶动力学进行了探讨[2-4],发现引入传统氧化物和非氧化物作为添加剂可以在一定程度上改善熔融石英的析晶情况[5-6],但有关添加剂对熔融石英陶瓷晶化抑制机㊀第1期谷莹蕾等:纳米氧化镱对熔融石英析晶动力学机制的影响145㊀理的研究报道较少[7-8]㊂一些学者发现在某些硅酸盐玻璃体系中引入稀土氧化物可以改善某些玻璃的析晶情况,对玻璃的网络结构进行补充,提高析晶活化能[9-10]㊂在实验室前期工作中发现,添加少量纳米氧化物可以有效改善熔融石英陶瓷析晶情况[11-12]㊂本文在前期研究基础上,对含纳米氧化镱的熔融石英陶瓷材料的析晶动力学和析晶机理进行初步探讨,为熔融石英晶化抑制剂的选择和安全可靠性熔融石英陶瓷材料的应用研究提供理论基础㊂1㊀实㊀㊀验1.1㊀样品制备本实验所采用的主要原料为微细熔融石英粉,其物相为非晶态的SiO2,纯度为99.5%,颗粒粒径d50为30μm㊂用于熔融石英析晶抑制的添加剂为纳米氧化镱,其纯度为99.9%,颗粒粒径d50为40nm㊂试样以熔融石英细粉为主要原料,引入3%的纳米氧化镱(质量比)为添加剂,试样采用模压方法成型,成型及干燥后的熔融石英陶瓷试样放入设定温度的电炉中进行高温处理(1300ħ㊁1350ħ㊁1400ħ和1450ħ)㊂含纳米氧化镱的试样标记为Y,不含纳米氧化镱的空白试样标记为B㊂1.2㊀性能测试使用D/MAX2500PC型X射线衍射仪对试样的物相组成进行测试分析;试样的析晶率f通过式(1)进行计算:f=A1A0ˑ100%(1)其中:A1是实验试样的物相衍射峰面积,A0是标准样的物相衍射峰面积㊂2㊀结果与讨论2.1㊀不同温度析晶处理后试样的析晶率图1㊁图2分别为熔融石英陶瓷空白试样和添加纳米氧化镱试样在不同烧成温度和保温时间的XRD图谱㊂不同熔融石英试样的析晶率f可以根据图1㊁图2的物相衍射峰及式(1)计算求得㊂图3㊁图4给出了两种熔融石英陶瓷析晶量随烧成温度和保温时间变化的曲线㊂从图1(a)可以看出,熔融石英陶瓷空白试样在1300ħ烧成后保温0.5~1.5h条件下,XRD图谱中没有明显的析晶现象;至保温3h时试样B出现了析晶现象㊂由图1(b)~(d)可以发现,保温0.5h的熔融石英陶瓷试样B中,在1350ħ烧成温度时可看到明显的析晶现象,当温度升至1400ħ㊁1450ħ时析晶现象更加明显,表明随烧成温度的提高,熔融石英析晶的程度在不断增大㊂由图2(a)~(d)可见,含纳米氧化镱试样Y中的主要物相为方石英,图2(c)及图2(d)中出现微弱的焦硅酸镱(Yb2Si2O7)衍射峰,表明氧化镱与熔融石英中的SiO2在1400ħ以上烧成后发生化学反应,形成第二相Yb2Si2O7㊂方石英衍射峰随烧成温度升高及保温时间延长也在不断增强,但相对于同等条件下的熔融石英陶瓷试样B有较大幅度的降低,表明引入纳米氧化镱能够有效地影响熔融石英的析晶行为㊂由图3㊁图4可见,随烧成温度升高或保温时间延长,空白试样B和含纳米氧化镱试样Y的析晶率f逐渐增大,但两种试样的析晶率f变化曲线存在较大差异㊂若以保温时间0.5h㊁熔融石英析晶率f值5%为熔融石英的起始析晶温度标志,由图3㊁图4可直观看出,空白试样B的熔融石英起始析晶温度为1350ħ,引入纳米氧化镱的试样Y的熔融石英起始析晶温度为1400ħ㊂若以保温时间3.0h㊁熔融石英析晶率f值50%为熔融石英的显著析晶温度标志,由图3㊁图4可直观看出,空白试样B的熔融石英显著析晶温度为1350ħ,引入纳米氧化镱的试样Y的熔融石英显著析晶温度为1400ħ㊂结果表明,在熔融石英陶瓷材料中引入纳米氧化镱可明显提高熔融石英的析晶温度㊂2.2㊀熔融石英高温析晶动力学分析由图3㊁图4给出的试样B和试样Y在不同温度及不同保温时间t的析晶率f,采用Avrami方程(式2)及其对数式(式3)[13-15],对不同热处理条件的试样B及试样Y进行熔融石英析晶过程动力学分析㊂f=1-exp(-kt n)(2)146㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第50卷lnln(1-f)-1=ln k+n ln t(3)其中:f是析晶率,%;k是与成核生长和析晶活化能有关的常数,s-1;t是保温时间,s;n是与析晶机理有关的常数,它反映了晶化过程的成核和长大机制㊂k值与析晶相变反应过程的温度㊁析晶活化能的关系如式(4)所示㊂[16-17]图1㊀不同烧成温度和保温时间条件下试样B的XRD图谱Fig.1㊀XRD patterns of samples B sintered at different temperatures and holding time图2㊀不同烧成温度和保温时间条件下试样Y的XRD图谱Fig.2㊀XRD patterns of samples Y sintered at different temperatures and holding time㊀第1期谷莹蕾等:纳米氧化镱对熔融石英析晶动力学机制的影响147㊀图3㊀不同温度烧成后试样B 的f -t 关系Fig.3㊀Relation of f -t for samples B sintered at differenttemperatures 图4㊀不同温度烧成后试样Y 的f-t 关系Fig.4㊀Relation of f-t for samples Y sintered at different temperaturesk =νexp(-E /RT )(4)其中:ν是频率因子;E 是析晶活化能;T 是热力学温度;R 是气体常数㊂由试样B 和试样Y 在不同保温时间t 的析晶率f ,按式(3)计算出lnln(1-f )-1及ln t ,试样B 与试样Y的lnln(1-f )-1-ln t 的拟合直线分别如图5㊁图6所示㊂由拟合直线及式(3)可分别确定出不同温度烧成后试样的直线斜率n 值和直线截距ln k 值,计算结果列于表1㊂随试样烧成温度的升高,试样B 的ln k 值波动于-12.72~-6.95,试样Y 的ln k 值波动于-15.66~-7.53,表明纳米氧化镱的引入明显降低了熔融石英的析晶速度㊂图5㊀不同温度烧成后试样B 的lnln(1-f )-1-ln t 的拟合曲线Fig.5㊀Fitting curves of lnln(1-f )-1-ln t for samples B sintered at differenttemperatures 图6㊀不同温度烧成后试样Y 的lnln(1-f )-1-ln t 的拟合曲线Fig.6㊀Fitting curves of lnln(1-f )-1-ln t for samples Y sintered at different temperatures㊀㊀对公式(4)取自然对数后结果如式(5)所示,将表1中试样B 及试样Y 的ln k 值代入式(5),对试样B 和试样Y 分别作ln k 与1/T 的拟合直线,如图7㊁图8所示㊂ln k =ln ν-E /RT (5)应用图7㊁图8的ln k -1/T 直线及式(5),可计算确定出直线斜率-E /R 值,由E /R 值进而计算出试样B 和试样Y 的析晶活化能E ,其值分别为874kJ /mol 和1188kJ /mol㊂从动力学角度分析,熔融石英析晶转化为方石英的过程中,晶格质点重排需要克服一定的势垒(即析晶活化能E ),因此熔融石英陶瓷析晶的难易程度可以用析晶活化能E 来判断㊂通过上述计算可知,含有纳米氧化镱的试样Y 的析晶活化能要大于熔融石英陶瓷试样B 的析晶活化能,表明在熔融石英陶瓷中引入纳米氧化镱可以提高熔融石英的析晶活化能,降低熔融石英的析晶率㊂148㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第50卷表1㊀不同温度烧成后试样B与试样Y的n值和ln k值Table1㊀The n values and ln k values of samples B and Y sintered at different temperatures Samples type Temperatures/ħn ln k1300 1.04-12.72Samples B1350 1.19-11.231400 1.06-9.1214500.89-6.951300 1.21-15.66Samples Y1350 1.26-14.151400 1.16-11.981450 1.08-7.53图7㊀试样B的ln k-1/T拟合曲线Fig.7㊀Fitting curve of ln k-1/T for samples B图8㊀试样Y的ln k-1/T拟合曲线Fig.8㊀Fitting curve of ln k-1/T for samples Y2.3㊀熔融石英高温析晶机理分析Avrami指数n是一个非常重要的动力学参数,它可以用来表征晶化转变过程中的形核和长大机制以及析晶机理㊂表2[18]列出了应用Avrami方程对玻璃态物质进行析晶机理分析的n值㊂由图5㊁图6及式(3)计算出不同温度烧后试样B的n值波动于0.89~1.19,试样Y的n值波动于1.08~1.26,表明随着烧成温度升高,试样B与试样Y中熔融石英的析晶机理发生了改变㊂表2㊀不同析晶机理对应的n值[18]Table2㊀The n values of different crystallization mechanisms[18]Nucleation type Grain growth mode Phase control interface Diffusion controlOne dimensional growth10.5Heterogeneous nucleation Volume mechanism Two dimensional growth21Three dimensional growth3 1.5Surface mechanism Two dimensional growth~21One dimensional growth2 1.5Homogeneous nucleation Volume mechanism Two dimensional growth32Three dimensional growth4 2.5Surface mechanism Two dimensional growth3~2㊀㊀本实验的熔融石英陶瓷试样是由玻璃态熔融石英微细颗粒制备的烧结体,熔融石英是由硅氧四面体[SiO4]顶点无序连接的三维网络结构的玻璃体,熔融石英颗粒的析晶行为或析晶机理与其物相成分㊁粒径及颗粒表面缺陷㊁添加剂纳米氧化镱与熔融石英颗粒的相互作用等因素有关㊂因加工过程中的机械粉磨作用,熔融石英颗粒表面层结构形成了很多缺陷大㊁能态高的Si-O断键,这些断键在高温时极易形成SiO2玻璃脱玻为方石英的活性成核点 [12]㊂因此在1300ħ以上高温时,熔融石英微细颗粒的表面层结构获得足够热能后,这些活性成核点随即发生SiO2玻璃脱玻为方石英的析晶成核,随时间延长或温度升高,析晶成核逐步向内部扩散进行㊂本实验不同温度烧成后试样B的n值接近于1,表㊀第1期谷莹蕾等:纳米氧化镱对熔融石英析晶动力学机制的影响149㊀明熔融石英颗粒的析晶成核属于非均匀成核类型㊂本实验各温度烧成后试样B的n值为0.89~1.19,将其与表2中析晶过程控制类别的n值比较,试样B 的n值处于表2中0.5~1.5范围内㊂熔融石英颗粒成分是纯度高达99.5%的SiO2,物相基本为单相SiO2玻璃相,其结构与普通的锂铝硅酸盐微晶玻璃的多组分玻璃结构有较大的不同㊂因此熔融石英析晶成核后的晶粒生长不属于相界面控制,而属于扩散控制㊂将试样B的n值与表2中晶粒生长方式的n值类属进行比较,发现试样B中熔融石英析晶成核后的晶粒生长方式以二维生长的表面机制为主,同时伴随有一定程度的一维及三维生长方式㊂此种情况可分析为,试样B的熔融石英颗粒表面层在1450ħ高温获得足够热能后,表面层大多数的活性成核点随即快速发生SiO2玻璃脱玻为方石英的析晶成核㊂成核后的晶粒生长是沿熔融石英颗粒表面进行的二维生长,当晶粒二维生长的空间饱和后,晶粒开始进行垂直于颗粒表面的一维生长,并伴随三维生长方式㊂2.4㊀纳米氧化镱对熔融石英析晶机理的影响含有纳米氧化镱的试样Y的n值波动于1.08~1.26,略高于试样B的n值,与表2中n值类属比较,试样Y中熔融石英颗粒同样为不均匀成核类型,成核后晶粒的长大为表面机制或体积机制,主要受扩散控制㊂但试样Y的n值略高于试样B的n值,处于表2的1~1.5范围内,与试样B的n值的差异主要表现在1450ħ时熔融石英成核后的晶粒生长方式不同,即试样Y中熔融石英成核后晶粒生长向着二维方向生长(伴随三维方向),没有一维方向㊂重稀土氧化物氧化镱中的镱离子具有较高的电荷和场强,对试样Y中的玻璃网络结构起到了很强的积聚作用[19-23],使得玻璃网络结构的稳定性大大提高㊂另一方面,由于熔融石英颗粒表层存在非桥氧离子,高温时非桥氧离子被镱离子吸引,或与部分Yb离子结合形成Yb2Si2O7,使得熔融石英颗粒表面层的活性成核点大大减少,玻璃网络结构的稳定性得到了提高,熔融石英的析晶率降低,熔融石英的析晶活化能得到了提高[19]㊂这与试样Y和试样B的熔融石英析晶率f的差异情况(见图3㊁图4)基本一致,也与试样B 和试样Y析晶活化能E的差异情况具有较好的一致性㊂因此,1450ħ时试样Y的熔融石英颗粒表面层的析晶成核少,成核后的晶粒在沿颗粒表面层的二维方向上有较多的生长空间,所以试样Y的熔融石英析晶的晶粒生长为二维生长并伴随三维生长方式㊂综上,在熔融石英陶瓷材料中引入纳米氧化镱,具有减少活性成核点㊁稳定熔融石英玻璃表面结构㊁提高析晶活化能的作用㊂试样Y与试样B在熔融石英析晶机理方面的差异,表现为成核后晶粒生长方式的不同㊂3㊀结㊀㊀论(1)在熔融石英陶瓷材料中引入纳米氧化镱可明显提高熔融石英的析晶温度,表明纳米氧化镱的引入对熔融石英析晶过程产生了一定的影响㊂(2)动力学研究表明,引入纳米氧化镱会对熔融石英陶瓷析晶后的晶粒生长方式产生影响㊂熔融石英陶瓷空白试样的晶粒生长主要为二维生长兼有一维及三维的生长方式,而含纳米氧化镱的熔融石英陶瓷试样的晶粒生长则为二维兼有三维的生长方式;二者的析晶活化能分别为874kJ/mol和1188kJ/mol㊂(3)在熔融石英陶瓷中引入纳米氧化镱能够大幅度减少SiO2玻璃脱玻为方石英的活性成核点 ,增加玻璃表面结构稳定性,提高析晶活化能,大大降低熔融石英的析晶率㊂参考文献[1]㊀陈肇友.熔融石英陶瓷[J].耐火材料,1973,7(3):11-28.CHEN Z Y.Fused silica ceramics[J].Refractories,1973,7(3):11-28.[2]㊀WAGSTAFF F E.Crystallization and melting kinetics of cristobalite[J].Journal of the American Ceramic Society,1969,52(12):650-654.[3]㊀GARIBINA N V,PAVLOVSKII V K,SEMENOV A D.The effect of Al and Ca impurities on the properties of quartz ceramics[J].Glass andCeramics,1998,55(5/6):161-163.[4]㊀温广武,雷廷权,周㊀玉.不同形态石英玻璃的析晶动力学研究[J].材料科学与工艺,2001,9(1):1-5.WEN G W,LEI T Q,ZHOU Y.Crystallization kinetics of different morphologies of fused silica glass[J].Material Science and Technology,150㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第50卷2001,9(1):1-5(in Chinese).[5]㊀南守宇,卜景龙,王志发,等.熔融石英晶化抑制与烧结性能[J].河北理工大学学报(自然科学版),2009,31(3):95-98.NAN S Y,BU J L,WANG Z F,et al.Research on inhibiting crystallization and sintering performance of fused quartz[J].Journal of Hebei Polytechnic University(Natural Science Edition),2009,31(3):95-98(in Chinese).[6]㊀赵增宝,刘福田,吴翠珍,等.氮化硅对注凝成型熔融石英陶瓷性能影响的研究[J].硅酸盐通报,2010,29(5):1145-1148.ZHAO Z B,LIU F T,WU C Z.Effects of Si3N4on the fused silica ceramics by gel-casting[J].Bulletin of the Chinese Ceramic Society,2010, 29(5):1145-1148.[7]㊀卜景龙,王志发,窦光涛,等.熔融石英陶瓷材料的晶化抑制研究[J].稀有金属材料与工程,2007,36(S1):357-360.BU J L,WANG Z F,DOU G T,et al.Study on inhibiting crystallization of fused quartz ceramic materials[J].Rare Metal Materials and Engineering,2007,36(S1):357-360(in Chinese).[8]㊀张会芳,卜景龙,申书斌,等.Ho2O3-Y2O3对熔融石英晶化性能的影响[J].中国陶瓷,2015,51(7):12-15.ZHANG H F,BU J L,SHEN S B,et al.Effect of Ho2O3-Y2O3on crystallization behavior of fused quartz[J].China Ceramics,2015,51(7): 12-15(in Chinese).[9]㊀张保国,王玺堂,刘㊀浩.Y2O3对CaO-MgO-SiO2系可溶性陶瓷纤维析晶性能的影响[J].材料导报,2008,22(S2):382-384.ZHANG B G,WANG X T,LIU H.Effects of Y2O3additive on crystallization behavior of CaO-MgO-SiO2soluble ceramic fiber[J].Materials Review,2008,22(S2):382-384(in Chinese).[10]㊀王觅堂,程金树,李㊀梅,等.Y2O3掺杂对硅酸盐玻璃结构及其熔体黏度的影响[J].硅酸盐学报,2013,41(1):115-121.WANG M T,CHENG J S,LI M,et al.Effect of Y2O3dopant on structure and viscosity of silicate glass and melt[J].Journal of the Chinese Ceramic Society,2013,41(1):115-121(in Chinese).[11]㊀卜景龙,陈越军,于立学,等.纳米ZnO或纳米Y2O3对熔融石英陶瓷烧结性能的影响[J].耐火材料,2012,46(5):334-336.BU J L,CHEN Y J,YU L X,et al.Effect of nano-ZnO or nano-Y2O3on sintering property of fused quartz[J].Refractories,2012,46(5): 334-336(in Chinese).[12]㊀卜景龙,陈越军,王志发.纳米氧化铈和氧化镧对熔融石英高温晶化特性的影响[J].硅酸盐通报,2013,32(12):2611-2617.BU J L,CHEN Y J,WANG Z F.Effect of nano-CeO2and nano-La2O3on crystallization characteristic of fused quartz in high temperture[J].Bulletin of the Chinese Ceramic Society,2013,32(12):2611-2617(in Chinese)[13]㊀徐祖耀,李鹏兴.材料科学导论[M].上海:上海科学技术出版社,1986:189-193.XU Z Y,LI P X.Introduction to materials science[M].Shanghai:Shanghai Science and Technology Press,1986:189-193(in Chinese).[14]㊀冯㊀端,师昌绪,刘治国.材料科学导论[M].北京:化学工业出版社,2002:570-572.FENG D,SHI C X,LIU Z G.Introduction to materials science[M].Beijing:Chemical Industry Press,2002:570-572(in Chinese). [15]㊀KIM K D,LEE S H,AHN H K.Observation of nucleation effect on crystallization in lithium aluminosilicate glass by viscosity measurement[J].Journal of Non-Crystalline Solids,2004,336(3):195-201.[16]㊀YILMAZ S,ÖZKAN O T,GÜNAY V.Crystallization kinetics of basalt glass[J].Ceramics International,1996,22(6):477-481.[17]㊀胡丽丽,姜中宏.玻璃析晶难易的一种新判据[J].硅酸盐学报,1990,18(4):315-321.HU L L,JIANG Z H.A new criterion for crystallization of glass[J].Journal of the Chinese Ceramic Society,1990,18(4):315-321(in Chinese).[18]㊀PÉREZ-MAQUEDA L A,CRIADO J M,MÁLEK bined kinetic analysis for crystallization kinetics of non-crystalline solids[J].Journal ofNon-Crystalline Solids,2003,320(1/2/3):84-91.[19]㊀SONG S F,WEN Z Y,LIU Y,et al.Influence of dopants on the crystallization of borosilicate glass[J].Ceramics International,2009,35(8):3037-3042.[20]㊀董㊀伟,卢金山.MgF2含量对Li2O-Al2O3-SiO2微晶玻璃组织和光学性能的影响[J].材料热处理学报,2011,32(6):21-25.DONG W,LU J S.Effect of MgF2content on microstructure and optical properties of Li2O-Al2O3-SiO2glass-ceramics[J].Transactions of Materials and Heat Treatment,2011,32(6):21-25(in Chinese).[21]㊀陈国华,刘心宇.CeO2含量对MgO-Al2O3-SiO2系玻璃结构和晶化特性的影响[J].中南大学学报(自然科学版),2006,37(1):6-10.CHEN G H,LIU X Y.Effect of CeO2content on glass structure and crystallization behaviour of MgO-Al2O3-SiO2system[J].Journal of Central South University(Science and Technology),2006,37(1):6-10(in Chinese).[22]㊀LIN S L,HWANG C S.Structures of CeO2-Al2O3-SiO2glasses[J].Journal of Non-Crystalline Solids,1996,202(1/2):61-67.[23]㊀LU P,ZHENG Y,CHENG J S,et al.Effect of La2O3addition on crystallization and properties of Li2O-Al2O3-SiO2glass-ceramics[J].Ceramics International,2013,39(7):8207-8212.。

10.3聚合物的流动性汇总

不存在粘流态的状况
1〕、Td < Tf 的Linear Polymer: PAN、PTIF
2〕交联度很大〔体型〕或分子链刚性过强的 Polymer
Cured Epoxy resin 、 PF 、聚乙炔、联苯
2
10.3.2 流动机理
低分子物质：分子通过分子间的孔穴相继向某一方向移动〔外力作用方向〕，形成液体宏观流淌现象高分子的流淌：〔不是简洁的整条分子链的跃迁〕
是通过链段的相继跃迁来实现，即通过链段的逐步位移完成整条大分子链的位移
形象地说,这种流淌类似于蚯蚓的蠕动
这模型并不需在高聚物熔体中产生整个分子链那
样大小的孔穴,而只要如链段大小的孔穴就可以了。
这里的链段也称流淌单元,尺寸大小约含几十个主
链原子
3
聚合物粘性流淌时的形变
高弹形变:由链段运动产生的
为什么?
又如：橡胶加工中要求分子量分布宽，由于低分子量的相当于优良的增塑剂，对高分子量的局部起着增塑的作用，与其它协作剂混炼捏合时，比较简洁吃料，流淌性较好，可削减动力消耗提高产品的外表光滑度，而高分子量则保证产品物理力学性能。
28
③链支化的影响：短支链：比线形略微降低，不能产生缠结，并使分子间距离增加,分子间作用力减小使粘度下降。长支链：长支链使分子间易缠结，粘度增大，如当支链的分子量大于临界分子量的 2～4倍，则粘度升为线性的100倍以上。
12
1.在足够小的切变速率下,大分子处于高度缠结的拟网状构造,流淌阻力很大,此时缠构造造的破坏速度等于生成速度,故粘度保持恒定最高值,表现为牛顿流体的流淌行为;
2.当切变速率变大时,大分子在剪切作用下由于构象的变化而解缠结并沿流淌方向取向,此时缠构造造破坏速度大于生成速度,故粘度渐渐变小,表现出假塑性流体的行为;

热退火条件下球状纳米硅晶粒成核势垒阈值研究

热退火条件下球状纳米硅晶粒成核势垒阈值研究邓泽超;付念;褚立志;丁学成;傅广生;王英龙【摘要】利用纳秒脉冲激光烧蚀(PLA)技术,在室温、真空环境中沉积制备了非晶Si薄膜,并通过热退火实现了薄膜样品的晶化,利用扫描电子显微镜(SEM)、X线衍射(XRD)仪和Raman散射(Raman)仪等技术对退火后的样品进行形貌表征和晶态成分分析,确定了非晶Si薄膜晶化的热退火阈值温度以及在该条件下所形成球状纳米Si晶粒的平均直径,结果分别为850℃和15 nm.假定纳米Si晶粒为理想球体,结合固相晶化过程中的能量变化,计算得到了晶化形成直径15 nm球状晶粒所需要的能量,即成核势垒阈值,量级约为10-11 mJ.%Amorphous Si films were prepared by pulsed laser ablation in vacuum at room temperature.These samples were heated by annealing furnace in order to transform into crystalline film.Threshold of nucleation barrier and mean diameter of Si nanoparticle were determined through the results of SEM,Raman and XRD,which were 850 ℃ and 15 nm,respectively.If the shape of nanoparticle is assumed to be ideal sphere,we can obtain the magnitude of threshold nucleation barrier for the nanoparticle through calculation,which is in the order of 10-11 mJ.【期刊名称】《河北大学学报（自然科学版）》【年(卷),期】2017(037)005【总页数】5页(P471-475)【关键词】脉冲激光烧蚀;热退火;纳米晶粒;成核势垒【作者】邓泽超;付念;褚立志;丁学成;傅广生;王英龙【作者单位】河北大学物理科学与技术学院,河北省光电信息材料重点实验室,河北保定071002;河北大学物理科学与技术学院,河北省光电信息材料重点实验室,河北保定071002;河北大学物理科学与技术学院,河北省光电信息材料重点实验室,河北保定071002;河北大学物理科学与技术学院,河北省光电信息材料重点实验室,河北保定071002;河北大学物理科学与技术学院,河北省光电信息材料重点实验室,河北保定071002;河北大学物理科学与技术学院,河北省光电信息材料重点实验室,河北保定071002【正文语种】中文【中图分类】TN304尺寸均一可控的纳米Si晶粒(薄膜)在光电器件[1]、太阳能电池[2]和医学[3]等领域应用前景广阔.与此同时，随着社会发展和科技进步，许多Si基器件的性能提高对纳米Si晶薄膜面密度均匀性以及薄膜中的晶粒尺寸也提出了更高的要求.近年来，人们从不同的角度研究了纳米Si晶粒的气相成核与生长动力学过程，并且取得了很大的进展，到目前为止，人们对纳米Si晶粒气相成核生长动力学的原理，依然没有给出定论.在诸多纳米晶粒制备方法中，PLA[4-6]技术由于具有粒子蒸气浓度高、加热速度快以及样品污染小等特点而倍受青睐.采用PLA技术，可以通过引入惰性环境气体、改变气体种类或压强，通过气相成核沉积形成纳米Si晶薄膜；也可以先在真空环境中沉积得到非晶态薄膜后，再利用后续的激光退火[7]或热退火[8]等方法实现其由非晶态向晶态的转变.通过热退火方式处理在室温、真空条件下制备得到的非晶薄膜，实现其晶化的过程具有操作简单、实用性强和样品纯度高等优点.其原理是通过对非晶薄膜高温加热，为原子提供能量，使其运动加剧直至摆脱周围原子的束缚，发生迁移，从而实现弥补缺陷，完成结构由短程有序向长程有序的转变，即晶化.本实验首先采用PLA技术在室温、真空条件下制备非晶薄膜，然后通过退火炉高温热退火，实现了其向晶态的转化，通过图像分析软件确定了晶化阈值温度下形成的纳米Si晶粒平均尺寸，结合固相晶化过程中的能量变化计算得到了球状纳米Si 晶粒成核势垒阈值.实验光源为XeCl 准分子脉冲激光，波长308 nm，脉宽15 ns.在非晶Si薄膜制备过程中，反应室温度为室温、真空度为2×10-4 Pa；激光能量密度为3 J/cm2，脉冲频率3 Hz，衬底平行于靶面放置，间距3 cm.靶材采用电阻率为3 000 Ω·cm 的高阻单晶Si(111)，为保证烧蚀的均匀性，靶材安装在匀速转动的步进电动机上，转速为6 r/min.为避免单晶Si(111)衬底Raman和XRD本征谱线影响样品分析结果，便于表征，薄膜分别沉积在石英衬底和单晶Si(111)衬底上，厚度约为100 nm.将在石英衬底上沉积所得非晶薄膜样品放在退火炉中进行热退火，环境气体为高纯N2气，退火温度在700～1 100 ℃可调，热电偶测量误差±1 ℃.退火时间为30 min.退火结束后继续保持高纯N2气氛围，以保证样品在N2气环境中冷却至室温，这样可以有效避免样品发生高温氧化、氢化等现象，从而对样品质量和后续测量造成影响.需要指出的是，在热退火过程中，为准确确定非晶薄膜的晶化阈值温度，最初的退火温度调节步长为20 ℃，然后逐渐减小至10、5和2 ℃，最终确定了晶化阈值温度为850 ℃.采用XL 30 S-FEG型SEM(10 kV，×400 000)表征样品表面形貌；用MLI-2000型Raman光谱仪(6 328 nm，1 mW)和XRD (12 kW，Cuka Radiation)衍射仪分析样品的晶态成分.退火后的样品SEM图、Raman光谱和XRD 光谱分别如图1、2、3所示.由SEM图可以看出，当退火温度在晶化阈值以下，即848 ℃时，样品中未见明显纳米颗粒，升高到850 ℃时，薄膜中出现纳米颗粒，粒径平均尺寸为15 nm，但数量很少，表明非晶薄膜的晶化阈值温度为850 ℃；随着退火温度的进一步升高，晶粒数量增加，均匀度提高，如950 ℃和1 050 ℃结果所示.相同的结果在Raman谱线和XRD谱线上也得到了验证.从Raman 谱线可以看出，退火温度为848 ℃ 时，谱线主峰位在480 cm-1 附近，为非晶态特征峰；温度升高到850 ℃ 时，谱线主峰位在515 cm-1 附近，与此同时，在480 cm-1 左右还存在1个相对较弱的峰，这表明有纳米晶粒出现，但仍然存在一定比例的非晶成分.晶态特征峰峰位随着温度的升高右移，对称性增强，同时，非晶态特征峰强度减弱，说明样品的晶化程度越来越高，也就是晶态成分增加、非晶态成分减少.晶化程度进一步提高是由于提供给非晶薄膜晶化的能量在增大，当温度升至1 050 ℃ 时，谱线峰位在520 cm-1，非常接近于单晶Si 的特征峰，表明样品达到了一个很高的晶化度.由XRD谱可以看出，当退火温度为848 ℃ 时，谱线上并没有明显的特征峰，温度为850 ℃ 时，在28°附近出现了1个比较明显的峰，这个峰是晶态Si (111)特征峰，且比相应单晶Si特征峰要宽，这表明薄膜中已经有纳米晶粒形成.随着退火温度的升高，Si (111)特征峰越来越明显，峰值半高全宽逐渐减小，表明样品晶化度也越来越高，可以理解为样品中晶粒数量越来越多，变化规律与SEM图和Raman谱线的结果一致.从SEM、Raman光谱和XRD 光谱的分析结果，可以得出，当热退火温度达到晶化阈值温度时，非晶薄膜开始晶化并形成纳米晶粒.随着温度的升高，晶化程度进一步提高.非晶薄膜在热退火条件下的晶化属于固相晶化法(SPC).所谓固相晶化，是指非晶固体发生晶化的温度低于其熔融后结晶的温度.固相晶化过程中，非晶材料晶化的驱动力是晶化相对于非晶化的较低的吉布斯自由能，自由能差为负值，因此产生了促使非晶材料晶化的相变驱动力，在数值上等于单位体积相变所引起的系统自由能的降低，可表示为其中，ΔG为系统自由能的变化，ΔV为晶体体积变化量.非晶薄膜为不稳定结构，在加热的过程中吸收能量，发生向稳定态的转变，热退火会使得非晶结构中的一些原子离开原来的位置，迁移到另一更稳定结晶相原子团中.当温度增加产生的相变驱动力达到并越过势垒的高度时，非晶薄膜就完成了由非晶向结晶相的转移.随着更多原子越过两相之间的势垒加入到结晶相原子团中，原子团长大形成纳米晶粒.从能量的角度来讲，退火温度越高，所能提供晶化的能量就越大，当所需能量达到跃迁一个势垒的阈值时，就会发生晶相变化，到达一个相对稳定的位置，实现晶化.实验过程中制备的非晶薄膜厚度约为100 nm，通过扫描电子显微镜对样品的切面进行观察，发现样品表面比较平整，厚度均匀，表面并未出现类似山峰和丘陵状结构，可近似认为薄膜厚度一致，密度均匀.由于非晶Si与单晶Si的密度几乎相同，因此在晶化过程中，可认为形成纳米晶粒所需非晶薄膜的体积与晶粒体积相等.假设形成一个纳米晶粒的非晶部分为圆柱体结构，纳米晶粒为球状.根据体积相等的特点，有πr2hα=其中r为圆柱体底面半径，hα为非晶薄膜厚度，rSi为球状纳米晶粒半径.通过前面的实验结果可知rSi=7.5 nm，通过计算可得r=2.4 nm.晶化过程中能量变化可通过如下公式表述：其中ΔG为晶化过程中总的能量变化、ΔHac是单位体积Si非晶-晶态相变的能量变化，取ΔHac=-5×103 J/cm3[9]；2πrhα为圆柱体非晶薄膜的侧面面积，σac 为非晶Si/单晶Si的单位面积界面能，取σac=3 ×10-5J/cm2[10]；πr2为圆柱体非晶Si薄膜与衬底接触的底面积，σao为非晶Si/石英衬底的单位面积界面能，取σao=2×10-3 J/cm2[11].根据公式(2)可得出阈值温度下，形成半径为7.5 nm的晶粒，系统自由能变化量ΔG=0.9×10-11mJ，此值即为形成直径15 nm的晶粒所需要的能量，即成核势垒. 直径为15 nm的球状晶粒约包含8.7×104个Si原子， Si—Si键合能约为1.15 eV [12]，则直径为15 nm的晶粒具有的键合能为1.7×10-11 mJ，与晶化过程所需能量量级相同，均为10-11 mJ.采用脉冲激光烧蚀技术，在室温、真空环境中，沉积制备了一系列非晶Si薄膜，通过热退火的方式实现了非晶薄膜的晶化.通过扫描电子显微镜、X线衍射仪和Raman散射仪对晶化薄膜中晶粒进行表征，确定了在850 ℃晶化阈值温度下所形成的纳米Si晶粒平均直径约为15 nm.结合固相晶化过程中能量的变化，通过数值计算得到了直径约为15 nm的晶粒所需要的能量，即成核势垒，量级约为10-11 mJ.本实验通过从能量角度，定量分析了纳米Si晶粒的形成，为进一步研究纳米Si晶粒的气相成核生长动力学、制备尺寸均匀可控的纳米Si晶粒、达到产业化应用标准提供了参考.关于成核势垒大小的精确计算是下一步工作的重点，将通过朗缪尔探针对纳米Si晶粒的成核过程及其成核势垒进行深入研究．【相关文献】[1] KIM K,PARK J H,DOO S G,et al.Generation of size and structure controlled Si nanoparticles using pulse plasma for energy devices [J].Thin Solid Films，2009,517 (14): 4184-4187.DOI:10.1016/j.tsf.2009.02.016.[2] 梁伟华，郝东宁，丁学成，等.钛掺杂对纳米Si晶结构和光学性质的影响 [J].河北大学学报(自然科学版)，2017，37(3)：231-236.LIANG W H,HAO D N,DING X C,et al.Effects of Ti-doped on structures and optical properties of silicon nanocrystals [J].Journal of Hebei University(Natural Science Eition),2017,37 (3): 231-236.DOI:10.3969/j.issn.1000-1565.2017.03.002.[3] OUYANG Z,PILLAI S,BECK F,et al.Effective light trapping in polycrystalline silicon thin-film solar cells by means of rear localized surface plasmons [J].Applied PhysicsLetters,2010,96 (26): 1109-13.DOI:10.1063/1.3460288.[4] 秦爱丽，王英龙，丁学成，等.脉冲激光烧蚀铕粒子速度劈裂的蒙特卡罗模拟 [J].河北大学学报(自然科学版)，2014,34(5)：475-478.QIN A L，WANG Y L，DING X C，et al.Monte Carlo simulation of velocity splitting of europium ions produced by pulsed laser ablation [J].Journal of Hebei University(Natural Science Eition),2014,34 (5)：475-478.DOI:10.3969/j.issn.1000-1565.2014.05.006.[5] UMEZU I,SUGIMURA A，SUGIMURA.Formation of nanoscale fine-structured silicon by pulsed laser ablation in hydrogen background gas [J].Physical Review B,2007,76 (4)：045328-1-10.DOI: 10.1103/PhysRevB.76.045328.[6] WANG Y L,DENG Z C,FU G S,et al.The average size of Si nanoparticles prepared by pulsed laser ablation in the gas mixture of He/Ar,Ne/Ar or He/Ne [J].Thin SolidFilms,2006,515 (4): 1897-1900.DOI: 10.1016/j.tsf.2006.07.031.[7] KUO C C,YEH W C,CHEN J B,et al.Monitoring explosive crystallization phenomenon of amorphous silicon thin films during short pulse duration XeF excimer laser annealing using real-time optical diagnostic measurements [J].Thin Solid Films,2006,515 (4): 1651-1657.DOI: 10.1016/j.tsf.2006.05.046.[8] MISHRA P,JAIN K P.Temperature-dependent Raman scattering studies in nanocrystalline silicon and finite-size effects [J].Physical Review B,2000,62 (22): 14790-14795.DOI: 10.1103/PhysRevB.62.14790.[9] DONOVAN E P,SPAEPEN F,TURNBULL D,et al.Calorimetric studies of crystallization and relaxation of amorphous Si and Ge prepared by ion implantation [J].Journal of Appllied Physics,1985,57 (6): 1795-1804.DOI: 10.1063/1.334406.[10] PERSANS P D,RUPPERT A,ABELES B.Crystallization kinetics of amorphous Si/SiO2 superlattice structures [J].Journal of Non-Crystal Solids，1988,102 (1-3): 130-135.DOI:10.1016/0022-3093(88)90123-8.[11] TAGAMI T,WAKAYAMA Y,TANAKA S I.Influence of interfaces on crystal growth of Si in SiO2/a-Si/SiO2 layered Structures [J].Japanese Journal of Applied Physics.1997,36 (6B):L734-L736.DOI: 10.1016/0022-3093(88)90123-8.[12] MCPHERSON J W,REDDY V K,MOGUL H C.Field-enhanced Si-Si bond-breakage mechanism for time-dependent dielectric breakdown in thin-film SiO2 dielectrics [J].Applied Physics Letters，1997,71 (8): 1101-1103.DOI: 10.1016/0022-3093(88)90123-8.。

聚丙烯成核剂研究进展

聚丙烯成核剂研究进展马文辉;陈旭;韩振刚;张长军;吴冬;许云波【摘要】介绍了聚丙烯(PP)成核剂的种类和成核剂的作用机理以及其在聚丙烯改性中的作用,综述了国内外PP成核剂的研究现状,对PP成核剂的发展趋势进行了展望.%The variety and mechanism of nucleating agent for PP and its role in the modification of polypropylene were introduced.The progress of the nucleating agent for PP were reviewed,the development trend of nucleating agent for PP was discussed.【期刊名称】《合成材料老化与应用》【年(卷),期】2017(046)003【总页数】5页(P114-118)【关键词】聚丙烯;成核剂;改性【作者】马文辉;陈旭;韩振刚;张长军;吴冬;许云波【作者单位】中国石油兰州化工研究中心,甘肃兰州730060;中国石油兰州化工研究中心,甘肃兰州730060;中国石油兰州化工研究中心,甘肃兰州730060;中国石油兰州化工研究中心,甘肃兰州730060;中国石油兰州化工研究中心,甘肃兰州730060;中国石油兰州化工研究中心,甘肃兰州730060【正文语种】中文【中图分类】TQ325.1+4聚丙烯(PP)作为一种热塑性塑料，具有力学性能好、无毒、相对密度低、耐热、耐化学品、电绝缘性好、易于加工成型等优点，加之原料易得、价格相对较低，因而在家电、化工、建筑、轻工、汽车以及包装等领域得到了广泛应用，是五大通用合成树脂中增长速度最快、新品种开发最活跃的品种[1-5]。

但是在一些特殊的应用领域，聚丙烯还存在着刚性低、脆性高、对切口的冲击强度比较低等缺点与不足，这些缺点与不足严重影响了聚丙烯应用范围的扩展。

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Kinetics of crystallization of FeB-based amorphous alloys studied by neutronthermo-diffractometryA. Fernández-Martínez a, P. Gorría b,*, G. J. Cuello a, J. D. Santos b, M. J. Pérez ba Institut Laue-Langevin, B.P. 156, 38042 Grenoble, Franceb Departamento de Física, Universidad de Oviedo, C/Calvo Sotelo s/n, 33007 Oviedo, SpainAbstractKinetics of crystallization of two amorphous alloys, Fe70Cr10B20 and Fe80Zr10B10, have been followed up by neutron thermodiffractometry experiments performed in the two axis diffractometer D20 (Institut Laue-Langevin, Grenoble). The structural changes are directly correlated with the temperature dependence of the magnetization. Fe70Cr10B20 crystallizes following a two-step process: an eutectic crystallization of α-Fe (bcc) and the metastable tetragonal phase (Fe0.8Cr0.2)3B followed by another eutectic transformation to the stable phase (Fe0.75Cr0.25)2B and more segregation of α-Fe. These tetragonal phases are magnetically anisotropic, giving rise to a large increase of the coercivity. This behaviour is similar to that of Fe80B20 alloys, with Cr atoms replacing the Fe positions in both crystalline phases. Fe80Zr10B10 shows also a two-step process in which two polymorphic transformations take place.PACS: 61.12.Ld; 61.43.Dq; 77.80.Bh; 73.63.Bd.Keywords: Crystallization; Amorphous alloys; Neutron diffraction.* Corresponding author: Tel: +34 985 102899 ; fax; +34 985 103324. E-mail address: pgorria@uniovi.es (P. Gorría).Amorphous FeCrB and FeZrB alloys form part of a group of materials with both soft magnetic response at room temperature and anomalous magnetic behaviour like spin-glass, reentrant spin-glass and INVAR effect at low temperatures, especially in Fe-rich compounds. The addition of B to FeZr amorphous alloys increases the Curie temperature and the Fe magnetic moment [1]. Introduction of Cr changes the magnetic and mechanical properties of FeB-based metallic glasses, including higher resistance to corrosion [2-4]. Thermal treatments are usually carried out to get nanocrystalline or strain-relaxed states, which optimize the soft magnetic behaviour. They give rise to the appearance of nanocrystalline grains that overcome structural phase transitions when rising the temperature. These structural transitions are correlated to changes in the magnetic response of the materials. In this work, a neutron thermodiffraction experiment has been carried out in order to correlate the changes in the magnetization with structural phase transitions.Ribbons of compositions Fe70Cr10B20 and Fe80Zr10B10 were synthesized by means of the melt spinning technique in a vacuum chamber. The magnetization vs. temperature curves, M(T), were measured in a Faraday susceptometer under an applied magnetic field of 1 kOe and in the temperature range between 293 and 1073 K. In situ neutron thermodiffraction experiments were carried out at the two axis diffractometer D20 (ILL, Grenoble, France) in the same temperature range. The wavelength used was λ≈ 1.3 Å and the angular range, in 2θ, 0-157º. Differential scanning calorimetry (DSC) and hysteresis loops obtained from induction measurements [5] (not shown here) were performed to study both the crystallization process and the increase of coercivity with temperature due to magneto-crystalline anisotropy.The thermomagnetic curves for both materials (Fig. 1) show that in the heating-up, the magnetization, M, of the as-quenched Fe70Cr10B20 sample deeply decreases at around 390 K, indicating the Curie temperature, T C, of the initial amorphous phase.A sharp increase of M at above 723 K suggests the beginning of the crystallization of any ferromagnetic phase. Further heating leads to a progressive increase of M up to 1020 K, and then decreases. This indicates the presence of some amount of BCC-Fe (T C = 1043 K). On cooling down from high temperature, a change in the slope of M(T) curve is observed below 500 K, a signature of the Curie temperature of any ferromagnetic phase different from BCC-Fe. For the Fe80Zr10B10 sample a similar behaviour is observed, with a sudden increase of M at about 975 K, a change in the slope at around 1000 K and a Curie temperature close to that of the BCC-Fe. On cooling down, the existence of a Curie temperature around 400 K is also evident.Neutron thermodiffraction experiments for the Fe70Cr10B20 sample show that the crystallization process is qualitatively identical to that of the Fe80B20 amorphous alloys [6]: an eutectic crystallization of BCC-Fe (≈ 20%) and a tetragonal metastable phase with 4I symmetry (≈ 80%)takes place in a first stage at a temperature of 750 K. A composition for unit cell of Fe20Cr4B8 for the tetragonal phase fits well in the Rietveld analyses of the diffraction patterns (see Fig. 2.) When the temperature rises up to around 920 K, another eutectic crystallization of BCC-Fe (up to 40%, thus explaining the increase of magnetization, see Fig. 1) and a tetragonal phase with I4/mcm symmetry and composition Fe6Cr2B4 (≈ 60%) takes place. BCC-Fe is segregated also from the first tetragonal phase. Hence, the two changes in the slope of the M(T) curve on cooling can now be identified with the T C for BCC-Fe and (FeCr)2B phases.These two tetragonal phases are the same appearing during the eutectic crystallization of Fe80B20 metallic glasses, thus confirming the tendency of Cr to occupy the Fe atomic positions in FeCrB alloy.In the case of Fe80Zr10B10 the crystallization takes place following several primary transformations (see Fig. 3). The crystallization of FeZr mechanically-alloyed amorphous alloys has been already studied by different authors [7-10] and it seems to be very composition-dependent [7]. For the Fe90Zr10 alloy, a sequence of amorphous + BCC-Fe → BCC-Fe + FCC-Fe3Zr → BCC-Fe + FCC-Fe3Zr + FCC-Fe2Zr has been found [10]. In our case, the introduction of B modifies the process. Above 850 K, crystallization of the Fe2Zr phase with HCP structure takes place. This phase is paramagnetic at this temperature, because it is not found any change in M around 850 K. Heating above 975 K results in the segregation of BCC-Fe together with the beginning of the transformation between HCP and FCC crystal structures for the Fe2Zr phase. Also, some amount of metastable Fe3B phase with tetragonal crystal structure is formed. This phase has been found earlier in mechanically-induced phase transitions of Fe70Zr10B20 [11]. Further heating above 1020 K leads to a supplementary segregation of BCC-Fe (reflected in an increase of M, see Fig. 1.) accompanied by the crystallization of another phase of FeB-type. Different candidates are hold for this phase, as its indexation is quite difficult since the peaks are broad and have tiny intensities. The more suitable phase would be an orthorhombic phase of equiatomic FeB. A similar phase has been found from Mössbauer spectroscopy during the crystallization of FeZrB-based metallic glasses [11,12]. Moreover, the M(T) curve, on cooling, suggest the existence of a ferromagnetic phase with a T C below 450 K (see Fig. 1), significantly lower to that of FeB (598 K [13]). However, some Zr atoms could be dissolved in such FeB phase, leading to a decrease of T C.We can propose the following as the complete crystallization process for Fe80Zr10B10: amorphous → amorphous + HCP-Fe2Zr →HCP-Fe2Zr + BCC-Fe + tetragonal-FeB + FCC-Fe2Zr → FCC-Fe2Zr + FeB + BCC-Fe.In conclusion, these metallic glasses present complex crystallization processes. In the case of FeCrB alloy, the affinity of Cr for the Fe atomic positions in the crystallization products is shown. On the other hand, the crystallization behaviour for FeZrB is strong composition-dependent,exhibiting several primary transformations. A new crystallization sequence is proposed, with the appearance of the HCP-Fe2Zr phase.References[1] J. M. Barandiarán, P. Gorría, J. C. Gómez Sal, et al., IEEE Trans. Magnet. 30 (1994) 4776-4778.[2] A. Lovas, L. F. Kiss and F. Sommer, J. Non-Cryst. Solids 192,193 (1995) 608-611.[3] J. A. Verduzco, I. Betancourt, F. Saavedra, et al., J. Non-Cryst. Solids 329 (2003) 163.[4] U. Güntzel and K. Westerholt, Phys. Rev. B 41 (1990) 740.[5] J. D. Santos, J. Olivera, P. Gorría, et al., J. Magn. Mag. Mat. 294 (2005) e155-e158.[6] H. J. Günterhodt et al. Glassy Metals I. Topics in Applied Physics. Volume 46. Ed. Springer-Verlag (1981).[7] P. Gorría, J. S. Garitaonaindía, R. Pizarro et al., Phys. B 350 (2004) e1075-e1077.[8] M. Fujinami and Y. Ujihira, J. Appl. Phys. 59 (1986) 2387- 2391.[9] F. Aubertin, U. Gonser, S. J. Campbell, et al., Z. Metallkunde 76 (1985) 237.[10] N. Zarubova, N. Moser and H. Kronmüller, Mat. Sci. Engineer. A151 (1992) 205-215.[11] A. Grabias, M. Kopcewicz and D. Oleszak, J. Allo. Comp. 339 (2002) 221-229.[12] T. Shinjo, F. Itoh, H. Takaki, et al., J. Phys. Soc. Jpn. 19 (1964) 1252.[13] C.L. Chien, K.M. Unruh, Phys. Rev. B 24 (1981) 1556.Figure captionsFig. 1. Thermomagnetization curves for both alloys. The arrows show the crystallization temperatures of magnetic phases (see inset for Fe80Zr10B10).Fig. 2. Weight fraction diagram from the Rietveld refinement of the Fe70Cr10B20diffraction patterns. The crystallization of BCC-Fe at 750 K and 950 K explains the increase of M in Fig. 1.Fig. 3. Neutron diffraction patterns showing the structural evolution of the Fe80Zr10B10 sample at some selected temperatures.Fig. 1.A.Fernández-Martínez et al.Fig. 2.A.Fernández-Martínez et al.Fig. 3.A.Fernández-Martínez et al.。