Ab Initio Study of Aluminum-Phosphorus Co-doped Graphene

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第八届国际凝聚态理论与计算材料学会议

大会将请专家对以下领域作专题性的特邀报告:
(1). 凝聚态物理的最新进展:
A. 自旋电子学
B. 纳米材料
C. 固体量子信息和计算
D. 玻色－爱因斯坦凝聚
E. 强关联电子系统
F. 高温超导
G. 量子霍尔效应
H. 磁学
I 表面和界面
J. 半导体物理
K. 低维凝聚态物理
L. 介观物理
M. 软凝聚态物质
N. 生物物理
structure Metallic Phases in Solid Germane (GeH4) under Pressure 锗烷在
压力下的金属相
11:45 -12:15
12:15 -13:00
午餐
张振宇橡树岭国家实验室
柳百新
清华大学
林海青香港中文大学牛谦美国德克萨斯大学
7 月 16 日
凝聚态理论专题邀请报告 I 主持人：谢心澄地点：芙蓉厅
14:30 -14:55 14:55 -15:20 15:20 -15:45 15:45 -16:10 16:10 -16:35 16:35 -16:50
7 月 16 日
Manipulating Magnetization States of Nanostructures Two-spin decoherence in semiconductor quantum dots
稀磁半导体(Al,Cr)N 中的氮空位与高温铁磁性的第一原理研究
蒋青刘邦贵
吉林大学中科院物理所
15:20 -15:45 15:45 -16:10 16:10 -16:35
Theoretical and experimental studies of semiconductor dilute nitrides and devices

铝硅磷质胶凝材料的微观结构与性能_周新涛

2 结果分析与讨论
2.1 偏高岭土粒度特性对铝硅磷质胶凝材料胶凝性能及力学性能的影响采用不同粒度组成的偏高岭土按 P2O5 与 Al2O3
的摩尔比为 0.202 与磷酸盐溶液混合，充分搅拌后，分别测试其终凝时间及 7 d 抗压强度，其结果见表 2。由表 1 和表 2 可以看出：随着偏高岭土粉体细度的减小到一定的程度，偏高岭土与磷酸盐溶液反应的速度成倍地加快，当其 D50 从 3.98 µm 降到 1.80 µm 时，其与磷酸盐溶液反应后所对应的胶凝材料的终凝时间从 96 h 急降为 6 h，随着其粒径的继续减小，其凝结时间下降的趋势趋于平缓。主要是由于偏高岭土颗粒比表面积的增大，致使其与磷酸盐的有效接触面积增加，更容易被磷酸盐溶液润湿包敷。 Torres–Sanchez 等[5]的研究指出：偏高岭土经过一定时间的机械处理后，其颗粒表面的 Si 与 Al 的摩尔比减小，形成一个富 Al 的包敷层，并有大约 30% 的活性更高的游离 Al2O3 形成。在常温高岭土可以与磷酸盐溶液发生较为温和的反应(相对于 MgO)，形成无定形相的 Al2(HPO4)3 或 AlPO4 胶体，并包敷于未反应的偏高岭土颗粒表面。相应地，随着偏高岭土粒度的减小，其与磷酸盐溶液反应所得铝硅磷质胶凝材料的力学性能呈明显上升的趋势，当其中位径低至 1.80 µm 时，其 7 d 强度达到 92.5 MPa，随着其粒度继续减小，其强度的上升趋势趋于平缓。
µm
(m2·g–1)
1
1.52 3.98 8.53 3.10
1.94
2
1.09 1.98 5.28 1.89
3.18
3
0.90 1.96 4.23 1.70
3.53
4

杂原子取代的磷酸铝系列分子筛的合成及进展

杂原子取代的磷酸铝系列分子筛的合成及进展XX(==========学院地址邮编 )摘要对沸石和沸石类分子筛材料的合成研究进行了综述, 介绍了磷酸铝系列分子筛的结构特点，对杂原子取代的磷酸铝系列分子筛的合成种类与方法进行了总结关键词沸石沸石分子筛杂原子磷酸铝分子筛无机合成Synthesis and March of the Hetero-atom Substituted the Aluminum phosphate’s cCoarse Zeolite-like Molecular SieveXX( )Abstract Research on synthesis of zeolite and zeolite-like molecular sieve materials were reviewed, introduce the composition’s characteristic of aluminum phosphat e’s coarse zeolite-like molecular sieve, summarize the synthetic method of the hetero-atom substituted the aluminum phosphate’s coarse zeolite-like molecular sieve.Keywords zeolite; zeolite-like molecular sieves; (APO)ALPO4-n ;hetero-atom; inorganic synthesis收稿：××××年××月。

收修改稿：××××年××月* 国家自然科学基金资助项目(No. xxxxxxxx)* * Corresponding author e-mail: aaa@1756年瑞典矿物学家Cronstedt[1]发现有一类天然硅铝酸盐矿物在灼烧时会产生泡沸现象，就称之为沸(Zeolite)。

镁铝水滑石催化剂英文

镁铝水滑石催化剂英文Magnesium-Aluminum Layered Double Hydroxide (LDH) CatalystsMagnesium-Aluminum Layered Double Hydroxides (LDHs) have emerged as promising catalysts due to their unique structure and properties. These materials are composed of positively charged hydroxide layers analogous to brucite (Mg(OH)2), which are intercalated with various anions or anion clusters. The versatility of LDHs lies in their ability to incorporate a wide range of anions into their layers, making them suitable for various catalytic applications.The structure of LDH consists of an alternating stacking of brucite-like layers and interlayer spacing that accommodates anions. This structure allows LDHs to exhibit tunable physicochemical properties, such as surface area, pore volume, and acid-base properties, which can be tailored to optimize catalytic performance.LDHs are often used as catalysts or catalytic supports due to their high surface area, excellent thermal stability, and ability to resist sintering at high temperatures. They can be activated by incorporating transition metals or transition metal oxides into their layers, which can significantly enhance their catalytic activity.One of the primary applications of magnesium-aluminum LDH catalysts is in the catalytic reforming of refinery by-products. LDHs can effectively catalyze the cracking of heavy hydrocarbons, facilitating the production of valuable light hydrocarbons, such as gasoline and jet fuel. This catalytic process is achieved under conditions of moderate temperatures and pressures, making it economically viable.Additionally, LDHs have been studied for their role in the catalytic hydrolysis of cellulose, a major component of biomass. The catalytic hydrolysis of cellulose represents a significant step towards the production of sustainable biofuels. LDHs areconsidered potential catalysts in this process due to their ability to facilitate cellulose breakdown through the activation of acid sites.The synthesis of magnesium-aluminum LDH catalysts can be achieved through various methods, including coprecipitation, hydrothermal synthesis, and sol-gel methods. The choice of synthesis method can significantly influence the physicochemical properties of the resulting LDH catalyst.In conclusion, magnesium-aluminum LDH catalysts are versatile materials with significant potential for industrial applications, particularly in the refining of fuels and the production of biofuels. The ability to tailor the properties of LDHs through their synthesis and modification offers an excellent opportunity for developing efficient and environmentally friendly catalytic processes. Future research is expected to explore further the potential of LDHs in catalytic applications and to develop new synthesis strategies to enhance their catalyticperformance.。

汽车发动机零部件用压铸铝合金

《铝加工》2016年第6期总第233期技术工程/专利荟萃散，尺寸较细小；样品沿宽度方向晶粒组织基本平；0°和90°方向卷边性能不理想，有待改进。

均勻，平均晶粒尺寸小于50um;漆刷线处于2级水Analysis on Samples of Aluminum Alloy Automotive Body SheetWEN Qing-hong, FENG Wang(Southwest Aluminum (Group) Co.,Ltd., Chongqing 401326, China)Abstract：Automobile lightweight has become a trend of automobile industry development in the world, demand for automotive sheet of aluminum alloy has increased daily. Analysis results have been evaluated after analyzing various compound properties of aluminum alloy automotive body sheet samples of certain plant.Keywords: microstructure; baking paint property; paintbrush line; crimping factor具有较好抗铝铸件表面粘砂的型芯砂欧洲专利WO2014077203本专利提供了一种由原砂、水玻璃粘结剂和无机粒状化合物等组成的铸造用型芯砂，其中无机粒状化合物是不溶于水的。

采用本专利所发明的无机粒状化合物，在金属液浇注的高温作用下能释放出水蒸气或C02气体，它可使粘结薄膜发生裂纹，使粘结剂失去粘结能力而溃散，从而将型芯砂很轻易地从铝铸件表面剥离下来。

研究生经典文献阅读要求

经典文献目录要求：1.每名同学结合本专业某一部经典著作写一份2000字以上的读书报告，入学时交到学院办公室。

2.每位硕士阅读经典文献时力求课内和课外相结合，以课内阅读监督课外阅读。

必须在第二学期期末之前提交一份2000字书面文献阅读报告。

无机化学专业学术规范与科技写作：1．中华人民共和国著作权法（2001年修正）。

全国人民代表大会常务委员会公报，2001 2．中华人民共和国著作权法实施条例。

中国出版，2002（9）。

高等有机化学：1．K. Fukui, “Molecular Orbitals in Chemistry,Physics, and Biology,” P.0. Löwdin and B.Pullman, Ed., Academic Press, New Y ork, N. Y., 1964, p 513,2．R.B.Woodward and R.Hoffmann,J.Am.Chem.Soc.,87,395(1965)3．Alvarez S, Vicente R, R. Hoffmann, J.Am.Chem.Soc.,107,6253-6277(1985)4．Cao Y W,Cai X D, Li T J et al. mon, 1999:16055．Pope M, Kallmann H P, Magnante P. J Chem Phys, 1963,38:2042.配位化学：1．Stynes, H. C. and Ibers, J. A. Inorg. Chem., 1971, 10, 2304.2．Gaswick, D. and Haim, A. J. Am. Chem. Soc., 1974, 96, 7845.3．Basolo, F., Gray, H. B. and Pearson, R. G. J. Am. Chem. Soc., 1960, 82, 4200. 4．Cannon, R. D. and Gardiner, J. Inorg. Chem., 1974, 13, 390.高等无机化学：1．Ralph G. Pearson, J. Am. Chem. Soc.; 1969; 91(5); 1252-1254.2．Steven A. Sunshine, Douglas A. Acc. Chem. Res.; 1987; 20(11); 395-400.3．William C. Bray, Chem. Rev.; 1932; 10(1); 161-177多酸化学：1．Pope, M. T., Heteropaly and Isopaly Oxometalates, Berlin, Heidelberg New York, Spring Verlay,1983.2．王恩波，等：《多酸化学导论》，北京化工出版社。

拟薄水铝石发展实验文献

The raw materials used were mainly sodium metaaluminate, carbon dioxide, and ammonium nitrate. The operation procedure is as follows: the aqueous phase which first flowed through the channel did not mix with the original sodium metaaluminate solution; after that, the circulation of the NaAlO2 solution was started. The volume of NaAlO2 aqueous phase was 0.5 L. The reaction occurred at the temperature of 25 ℃, and the pH was recorded during the whole reaction process. After the pH reached a certain value, the reaction was stopped, and the product was aged for 1 h at a temperature of 70 ℃ and then washed by an ammonium nitrate concentration of 0.01%(amount of substance fraction). After that, it was leached out and dried at 70 ℃ for 10 h. After the calcination of the PB at 550 ℃ for 4 h in a muffle furnace, the microporous γ-Al2O3 could be obtained.

熔盐电镀制取铝电解用TIB2惰性阴极

收稿日期：2004-01-02基金项目：国家重点基础研究与发展规划项目（G 1999064903）；·第25卷第9期2004年9月东北大学学报（自然科学版）Journal o f Nort heastern U ni versit y （N at ural S cience ）V o l.25，No.9S e p !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.2004文章编号：1005-3026（2004）09-0873-03熔盐电镀制取铝电解用T i B 2惰性阴极徐君莉，石忠宁，邱竹贤（东北大学材料与冶金学院，辽宁沈阳110004）摘要：采用熔盐电解法在碳阴极上电镀T i B 2铝电解用惰性阴极材料，电解温度800C ，电解质组成（质量分数，%）为KC l 4.8，KF 55.7，K 2T i F 615.3，KBF 424.2，电流密度为0.3A ／c m 2，电解3h ·对制得的镀层做XRD 和EM P 电子探针形貌分析，实验结果表明，镀层成分为单一的T i B 2，无杂相·镀层厚度可达0.2mm ，表面平整，分布均匀，与碳基体结合良好，且有金属光泽·说明该电解条件下，T i 和B 能够在阴极上共沉积并生成T i B 2·关键词：铝电解；惰性阴极；熔盐电镀；T i B 2涂层中图分类号：T F 821文献标识码：A现在工业铝电解槽的槽破损主要是阴极碳块的破损，这主要是目前铝电解槽的阴极是碳阴极，它虽能够较好地满足铝电解生产的需要，但由于碳对铝液的湿润性不好，使冰晶石熔体，尤其是其中的钠浸入碳块，促使碳阴极体积膨胀甚至产生裂缝，导致电解槽破损［1，2］·另外，电解质还可能渗漏至阴极钢棒，致使阴极产品铝中含铁量升高，降低产品质量·近年来T i B 2被公认为是较为合适的可代替碳阴极的材料［3!5］，因为T i B 2在铝中溶解度很小，具有良好的导电性和热稳定性，对铝液有良好的湿润性，能有效防止电解质熔体和钠的侵蚀［6，7］·T i B 2阴极表面不易生成沉淀或结壳，这不仅能使炉膛比较规整，使电流分布均匀，减少磁场对铝液的扰动，减缓二次反应过程，提高电流效率，也能改善铝的质量·炉底沉淀和结壳的减少，使得炉底电压降较低，降低了生产能耗·如果它能和惰性阳极配合使用，则可以进一步降低极距，降低电耗，提高电流效率［8!10］，使铝工业工艺获得重大突破·生产铝电解工业用T i B 2阴极的方法主要有：熔盐电解法、固相反应法、溶胶-凝胶法、化学气相沉积法·除了熔盐电解法外，其余几种方法生产纯度高的二硼化钛，成本甚高；因此往往采用在碳阴极上电镀T i B 2层作铝电解用惰性阴极，况且此项技术工艺过程简单，涂层费用低，能满足经济效益的要求［11］·国外对T i B 2涂层的研究比较深入，但目前也还没有在工业上得到完全应用·国内相关研究工作主要集中于东北大学、中南大学等高校，与国外水平相近·本文在前人的研究基础上对熔盐电解T i B 2工艺进行了进一步实验研究，希望能改进硼化钛涂层技术·1实验本文采用熔盐电镀法制取铝电解用T i B 2阴极·实验所用的装备如图1所示·图1熔盐电镀制取T i B 2阴极装置图F i 9.1Ex P e ri ment a l se tu P f o r e l ec tr o P l ati n 9T i B 2coati n 9实验中采用垂直方式电解，为了提高阳极电流密度，在碳阳极侧部套上刚玉套，避免电流从阳极侧部流过·本实验所用的电解质组成（质量分数，%）为Kc l4.8，KF55.7，K2t i F615.3，KBF424.2，均为化学纯·电解温度为8 C，电解时间为3h，电流密度为.3A／c m2·实验前预先把电解质烘干·氟化钾的烘干方法为：先把氟化钾加热到13 C时恒温24h，然后将其与NH4HF2按1I4质量混匀，在2 C恒温2h后，在45 !5 C下恒温3h·实验中观察到从炉中冒出白烟，直到白烟消失为止·其他的电解质均在2 C下烘干4h·电解过程中定时加入K2t i F6，KBF4以维持t i F2-6和BF-4的活度·2实验结果与讨论2.1槽电压与电解时间关系本实验中槽电压与电解时间关系如图2所示·图2槽电压与电解时间关系图F i9.2The r e l ati onshi P be t ween ce l l vo l t a9eand e l ec tr o l y ti c ti me从上图中可以看出，电解过程槽电压比较稳定，说明电解过程反应恒定·电镀实验后，发现t i B2镀层表面平整，有金属光泽·2.2镀层形貌分析对镀层表面作了电子探针形貌分析，如图3a；图3b为镀层中的钛的面分布图；图3c为碳基体和t i B2镀层界面形貌图·图3T i B2镀层形貌分析F i9.3Mo r P ho l o9y o f T i B2coati n9（a）—镀层表面；（b）—钛的面分布图；（c）—碳基体与t i B2镀层界面·从图3可以看出：镀层中钛含量的分布比较均匀，镀层比较致密，镀层的厚度约为.2mm·2.3XRD分析结果对镀层进行XRD成分分析，结果如图4所示·从XRD分析结果来看，镀层成分单一，均为t i B2·电解过程在电解槽中可能发生的反应有：t i F2-6+4e!-t i+6F-，!"=-1.19V；BF-4+3e!-B+4F-，!"=-1.6V；K++e!-K，!"=-2.924V；N a++e!-N a，!"=-2.714V·在此电解质体系中，从上述各物质的析出电位看，t i和B的析出电位比K，N a的高，更容易析出·而且t i F2-6和BF-4的分解电压很接近，t i 和B在阴极上可同时沉积出来，进一步反应生成t i B2或t i B·反应式为478东北大学学报（自然科学版）第25卷!G （T i B 2!!!）-461541+92.3T （J ／m o l ）·也有可能是T i （s ）+B （s !!!）T i B （s ），!G （T i B !!!）-302990+82.8T （J ／m o l ）·总反应为T i F 2-6+2BF -4+10e !!!-T i B 2+14F -，或T i F 2-6+BF -4+7e !!!-T i B +10F -·在800C 下，!G （T i B 2!!!）-362503.1（J ／m o l ），!G （T i B !!!）-214145.6（J ／m o l ）·由热力学计算可知：在实验条件下，反应T i F 2-6+2BF -4+10e !!!-T i B 2+14F -更有可能发生，但是并不能排除有T i B ，K ，N a 等在阴极上析出·从XRD 分析结果来看，本实验中没有在镀层中发现T i B ，K 20等杂质，这说明此种电镀工艺条件是比较优良的·3结论（1）熔盐电解制取T i B 2镀层，镀层成分均一，分布均匀，表面平整有金属光泽·（2）电解温度为800C ，电解质组成（质量分数，%）为KC l 4.8，KF 55.7，K 2T i F 615.3，KBF 424.2，在0.3A ／c m 2的电流密度下电解3h ，能得到较为理想的T i B 2涂层·参考文献：［1］邱竹贤·铝电解原理与应用［M ］·徐州：中国矿业大学出版社，1998.274-278（@i u Z X.T heor y and a 11lication o f al u m inu melectrol y sis［M ］.Xuzhou ：Ch i na U n ivers it y of M i n i n g and T echno lo gy P ress ，1998.274-278.）［2］M cleod A D ，~a gg ert y J S ，S adoW a y D R.E lectricalres istivities o f m onocr y stalli ne and p o l y cr y stalli ne T i B 2［J ］.Journal o f Am erican c era m ic s ociet y ，1984，67（9）：705-708.［3］王兆文，孙淑萍，李冰，等·M oS i 2对二硼化钛惰性阴极材料性能的影响［J ］·东北大学学报（自然科学版），1999，20（6）：619-621·（W an g Z W ，S un S P ，L i B ，et al .E ff ects o f M oS i 2add ition on p ro p erties o f t he T i B 2cat hode m aterial ［J ］.Journal o fN ort heastern Uniuersit y （Nat ural s cience ），1999，20（6）：619-621.）［4］Christi n i R A ，D a W less R K ，R a y S P.A dvanced anodes and cat hodes utilized i n ener gy efficient alu m i nu m p roduction ce lls ［R ］.C oo p erative A g ree m ent Nu m ber DE -FC 07-98I D 13666.W ash i n g ton ：U S D e p art m ent o f Ener gy ，2001.［5］邱竹贤·铝工业应用新型电极材料的研究［J ］·轻金属，2001，30（9）：30-34·（@i u Z X.R esearch and deve lo p m ent o f t he i nert cat hodeand anode i n alu m i n i u m e lectro l y s is ［J ］.L i g ht M etals ，2001，30（9）：30-34.）［6］B illehau g K ，0y e ~ A.I nert cat hode f or alu m i nu me lectro l y s is i n hall-heroult ce lls ［J ］.A l u m inu m ，1980，56（10）：642-648.［7］M ak y ta M ，D anek V.E lectrode p os it of titan i u m d i bori defrom f used salts ［J ］.Journal o f A 11lied electroche m istr y ，1996，26（3）：319-324.［8］@i u Z X ，L i @F.T i B 2coati n g on cat hode carbon b locks i nalu m i nu m ce lls ［A ］.L i g ht M etals ［C ］.W arrendale ：TM S ，1992.431-437.［9］Rob i n A ，R i be iro R P.Pulse e lectrode p os ition of titan i u m oncarbon stee l i n t he L i F -N aF -KF eutectic m e lts ［J ］.Journalo f A 11lied e lectroche m istr y ，2000，30（2）：239-246.［10］G ro t he i m K ，K vande ~.A lu m i nu m e lectro l y s is i n a 100Alaborator y ce ll W it h i nert e lectrodes ［J ］.M et all ，1988，42（6）：587-589.［11］L i B ，Zhou F ，@i u Z X.P re p aration o f T i B 2coated cat hodefrom m o lten salts ［J ］.Journal o f M aterials o f s cience and T echnolo gy ，2002，17（S 1）：171-173.Pre p arati on of T i B 2I nert C at hode b y E lectrode p ositi on Process f orA l u m i nu m E lectro l y sisXU Jun -li ，s~I zhon g -nin g ，@I U zhu -o ian （S choo l o f M aterials &M etallur gy ，N ort heastern U n ivers it y ，S hen y an g 110004，Ch i na .C orres p ondent ：XU Jun-li ，E -m ail ：j lxu " ）Abstract ：T he T i B 2as i nert cat hode m aterial f or alu m i nu me lectro l y s is ，W as e lectrode p os ited successf ull y on carbon cat hode as acoati n g b y W a y o f m o lten salts e lectro l y s is at 800C f or 3hours W it h a current dens it y 0.3A／c m 2，o f Wh ich t he com p os ition o f t he e lectro l y te used is 4.8KC l-55.7KF -15.3K 2T i F 6-24.2KBF 4i n %as m ass fraction.XRD W as used to detect t he com p os ition o f t he coati n g W it h t he E lectron P robe M icro A nal y zer （EPM ）used f or m or p ho lo gy observation.T he results shoW ed t hat t he coati n g is com p osed o f a s i n g le com p ound ，i .e.，T i B 2W it hout i nclus ions.T he 0.2mm -t h ick T i B 2coati n g is s m oo t h and a pp earsm etallic luster ，es p eciall y it is bonded fir m l y to t he carbon substrate.It is confir m ed t hat T i and B can be co -de p os ited to f or m a T i B 2coati n g on carbon surf ace as an i nert cat hode i n t h is W a y .K e y words ：alu m i nu m e lectro l y s is ；i nert cat hode ；m o lten salt e lectro l y s is ；T i B 2coati n g（R eceiued Januar y 2，2004）578第9期徐君莉等：熔盐电镀制取铝电解用T i B 2惰性阴极。

中英文翻译-铅元素对AZ91镁合金形成过程的影响{修}

Effect of Pb addition on ageing behavior of AZ91 magnesium alloyAbstractThe ageing behavior of AZ91 alloy containing 2wt.% lead is investigated. The results show that addition of Pb suppresses the discontinuous precipitation and thereby slows down the ageing kinetics. Even though the peak hardness obtained for both alloys is almost same, the peak hardness reaches after 2400min for Pb added alloy against 900min for the base alloy. The presence of Pb in solid solution might have inhibited the diffusion of Al and Mg atoms, which is essential for the formation, and growth of discontinuous precipitation in this alloy.Keywords: AZ91 magnesium alloy, Pb addition, Ageing behavior, Microstructure, DTA1. IntroductionMagnesium-based alloys are increasingly used in the auto-mobile industries. The reasons for this lie principally in their improved speciﬁc properties compared with aluminum alloys or steels and light weight (30% less than Al, and 75% less than steels) [1]. Among the most common commercial magnesium alloys, AZ91 is endowed with one of the best combinations of castability, mechanical strength and ductility [2]. Presence of aluminum provides mechanical and casting properties as well as corrosion resistance, whereas zinc contributes to solid solution strengthening. The maximum solid solubility of alu-minum in Mg is 12.7wt.% at 437 ◦C and decreasing to about 2wt.% at room temperature. Hence castings (sand and perma-nent mould castings) of this alloy are heat-treated to obtain better mechanical properties and studies are available in the lit-erature to understand the ageing behavior of this alloy [3–6].During solution treatment at 410℃, the Mg17Al12—βphase redissolves in to the Mg matrix and forms a homogenized solid solution. On subsequent ageing at lower temperature, aluminum precipitates out in two forms: i.e. discontinuous and contin-uous precipitates. Discontinuous precipitation is the cellular growth of alternating layers of phase (Mg17Al12) and near equilibrium magnesium matrix at high angle grain boundary[2,7,8].Growth of the discontinuous precipitation regions ceases relatively early in the precipitation process. Continuous pre-cipitation forms in the remaining regions of the matrix that are not already occupied by discontinuous precipitates [7].It is demonstrated that the continuous precipitates are responsi-ble for age hardening, whereas the discontinuous precipitates are detrimental to agehardening [6]. Moreover, the discon-tinuous precipitates formed during high temperature exposure(creep) reduce the creep properties considerably [9]. Dynamic discontinuous precipitates occur at the grain boundaries from the supersaturated eutectic solid solution lead to the sliding of grain boundaries and weaken the material [9]. Hence sup-pressing this dynamic discontinuous precipitation during high temperature exposure is inevitable to improve its high temper-ature properties. It is also reported that addition of some of the trace elements like gold and rare earth suppresses the discontin-uous precipitation during ageing [10,11]. But these elements are costlier.The preliminary study on the Pb addition to Mg–7Al has reported that addition of Pb has the tendency to suppress the discontinuous precipitation [12]. Besides, Pb is cheaper mate-rial compared to gold and rare earth. So, in this study a detailed investigation on the effect of Pb addition on the ageing behavior of gravity。

双草酸硼酸锂libob是一种新型的锂盐具有很

论文题目：锂离子电池新型电解质的研究作者简介：余碧涛，女，1977年6月出生，2003年9月师从于北京科技大学李福燊教授，于2007年3月获博士学位。

中文摘要随着人们环境保护意识的日渐增强，对绿色能源的渴求越来越迫切。

锂离子电池以其工作电压高，体积小、质量轻、比能量高、无记忆效应、无污染、自放电小，循环寿命长等优点，成为目前所有电池产品中最有前途的体系之一。

目前商品锂离子电池所用的锂盐为LiPF6。

LiPF6易水解且热稳定性不好，与大气的水分或溶剂的残余水接触时，会立即形成氢氟酸HF，对电池的性能有不利的影响；而且，LiPF6通常与碳酸乙烯酯（EC）合用配成电解液才能在负极形成有效SEI膜，但是EC的熔点较高（37℃），这限制了电池的低温使用性能。

双草酸硼酸锂（LiBOB）是一种新型的锂盐，具有很好的成膜性能和热稳定性，是一种很有潜力替代现有商品化锂盐LiPF6的物质。

本文创造性地采用固相反应法合成了LiBOB，并对反应过程进行了动力学和热力学分析；研究了所得LiBOB的基本性质，将其配制成电解液，研究了LiBOB在各种正极材料和石墨负极材料中的应用情况；考察了LiBOB的独特成膜性能，研究LiBOB-PC基电解液体系在锂离子电池中的应用性能；测定了不同LiBOB电解液的电导率，并引入了质量三角形模型对LiBOB电解液的电导率进行预报计算；采用密度泛函理论分析了LiBOB的分子结构与其物理化学性能之间的关系。

此外，还研究了亚硫酸酯类物质在锂离子电池中的应用。

已有的LiBOB合成方法都是在溶液体系中制备，其中采用草酸、氢氧化锂和硼酸在水相中制备LiBOB较具优势，但是，此种合成方式比较复杂，反应过程不好控制。

在此基础上，本研究提出了一种崭新的LiBOB合成方法固相反应法，TG/DTA曲线表明固相反应合成LiBOB经历五个不同的温度段，结合原料草酸、氢氧化锂和硼酸的热重曲线和XRD分析，推测了各温度段发生的化学反应。

离子热合成磷酸铝分子筛AlPO_4_11的研究

离子热合成磷酸铝分子筛AlPO 4211的研究苏家鹏1,　李坤兰31,　王少君1,　刘　娜1,　马英冲1,　林励吾2(1大连轻工业学院化学工程系,辽宁大连116034;2中国科学院大连化学物理研究所天然气化工与应用催化研究室,辽宁大连116023)摘　要:应用离子热合成法以溴化N 2烷基取代咪唑离子液体为反应介质,合成了AlPO 4211分子筛,考察了离子液体用量、磷铝比、HF 用量、晶化时间、晶化温度等条件对分子筛结构的影响,并对离子液体进行回收再利用,通过X 射线衍射、扫描电子显微照片、红外光谱等手段进行表征。

结果表明,在磷铝比1.5～4范围内,能合成出具有独特晶粒形貌的AlPO 4211分子筛,且离子液体能多次循环利用。

关键词:离子热合成;离子液体;磷酸铝分子筛;晶化条件中图分类号:O 611.4;T Q 050.4 文献标识码:A 文章编号:036726358(2007)012005205Study on I onothermal Synthesis of AluminophosphateM olecular Sieve AlPO 4211S U Jia 2peng ,　LI K un 2lan ,　W ANG Shao 2jun ,　LI U Na ,　MA Y ing 2chong ,　LI N Li 2wu(1Department o f Chemical Engineering ,Dalian Institute o f Light Industry ,Liaoning Dalian 116034,China ;2National Gas Utilization and Applied Catalysis Laboratory ,Dalian Institute o f Chemcial Physics ,The Chinese Academy o f Sciences ,Liaoning Dalian 116023,China )Abstract :AlPO 4211m olecular sieves with AE L structure were ionothermally synthesized using 12etyl 232methylimidazolium bromide ionic liquid ([emim]Br )as medium.The effects of ionic liquid am ount 、P ΠAl 、HF am ount 、crystallization time and tem perature on the structure of AlPO 4211were investigated.Besides ,the ionic liquid was recycled during the synthesis of AlPO 4211.The structure of the m olecular sieve sam ples were characterized by XRD 、SE M and IR.AlPO 4211m olecular sieve with unique particle m orphology can be synthesized only when the P ΠAl m olar ratio ranges from 1.5to 4.The ionic liquid can be recycled several times in the synthesis of AlPO 4211.K ey w ords :ionothermal synthesis ;ionic liquid ;aluminophosphate m olecular sieve ;crystallization conditions收稿日期:2006208210;修回日期:2006210225基金项目:国家“973”项目(2003C B615805)作者简介:苏家鹏(1982～),男,硕士生,主要从事分子筛催化等研究。

金属离子对硅酸聚合胶凝影响的研究_许韵华

文章编号:1000-1506(2003)06-0097-04金属离子对硅酸聚合胶凝影响的研究许韵华1,尹承龙2,朱红1,王永生1(北京交通大学1.理学院;2.土木建筑工程学院,北京100044)摘要:针对硅酸聚合胶凝而使聚硅酸金属盐混凝剂失活的特性,研究了Fe 3+、Al 3+、Cu 2+和Mg 2+金属离子对硅酸聚合胶凝曲线的影响作用.结果表明:在酸性实验pH 范围内,对硅酸的阻聚作用的大小顺序为:Fe 3+>Al 3+>Cu 2+>M g 2+.认为其影响作用是由于金属离子与硅酸的化学反应所致,但主要的还是对溶液中pH 值的缓冲效应.对铁Fe 3而言,由于其具有强烈的水解倾向,对羟基具有较好的捕获能力,从而减少了因硅酸聚合而释放出的OH -的催化影响作用,因而表现出良好的阻聚效应.关键词:分析化学;硅酸聚合;金属离子;阻凝效应中图分类号:X703.1 文献标识码:B Study on Effect of Metal Ions onPolymerization and Gel Reaction of Silicic AcidX U Yun -hua 1,YIN Cheng -long 2,ZH U Hong 1,WAN G Yong -sheng1(1.School of Science;2.School of Civil Eng ineering and Architectur e,Beijing JiaoT ong U niversity,Beijing 100044,China)Abstract:The effects of metal ions such as Fe 3+、Al 3+、Cu 2+and Mg 2+on the silicic acid polymer -ization and gel w ere studied.The experimental results show that the ability of anti-polymeriza -tion of metal ions is in the order:Fe 3+>Al 3+>Cu 2+>Mg 2+.T he effects were attributed partlyto the reaction between metal ions and silicic acid and mainly to the buffer effects of metal ions.The iron ion is the best due to its hydrolysis inclination and hydroxyl capturing ability.Key words:anahytical chemistry ;silicic acid polymerization;metal ion;resistance polymerizationeffect诸多的研究发现,聚硅酸中引入铝、铁等金属离子后,不仅具有絮凝架桥作用,还具有电中和效应,从而显著地改善了其混凝(絮凝)沉降性能;表现出许多类似于有机高分子絮凝剂的性质:沉降速度快,形成聚合态的网状分子结构和链状大分子,以及与颗粒物之间的架桥卷扫作用等.因此,对聚硅酸金属盐的研究一直成为人们关注的热点.国内外均有许多专利文献进行过报道[1~3].聚硅酸的胶凝问题,一直是阻碍聚硅酸金属盐商业化的因素.为延缓聚硅酸的胶凝,增长其保存时间,长谷川孝雄[4]、Hasegaw a T [5]等人开展了聚硅酸的改性工作,但最终都避免不了它的胶凝.范德顺[6]则在聚硅酸溶液中引入对羟基苯甲醚,试图待硅酸聚合到一定程度以后,用化合物阻止其进一步聚合,但效果并不明显,且由于有机物的引入,影响了絮凝剂的正常使用.金属离子的引入也使聚硅酸溶液的稳定性得到了改善.栾兆坤[7]等在进行铝硅复合絮凝剂的制备研收稿日期:2003-06-09基金项目:北方交通大学校基金资助(2002SM 050)作者简介:许韵华(1963))女,浙江临安人,高工,博士生.email:xyh3643@王永生(1963))男,吉林长春人,教授,博士,博士生导师.第27卷第6期2003年12月北方交通大学学报JO UR NAL OF N ORT HERN JIAO T ONG U NI VERSIT Y Vol.27No.6Dec.2003究时,通过向其引入适量的含Fe 3+化合物,从而较大地延长了铝硅复合絮凝剂的存放时间,而不致因聚硅酸的胶凝而失活.但其研究中没有指明铁盐加入前后的pH 变化情况.而铁盐是强酸性化合物,它的加入将会使溶液中的pH 值降低很多,因此难于判断这种改善是否为Fe 3+本身所为.外加盐对硅酸聚合形成凝胶速度的影响已有报道,国内外学者先后提出了催化作用[8]、桥联机理、第二盐效应和电解质增强感胶性机理[9]等.但这些机理难以说明广泛pH 范围内的实验事实,均有其局限性.本文在进一步探讨聚硅酸聚合机理的同时,就金属离子对硅酸的阻抑作用进行了研究,以求取改善聚硅酸稳定性能的有效途径.1 实验材料与方法1.1 试剂(1)单硅酸钠(Na 2SiO 3#9H 2O)为分析纯,配成溶液后,静置数日,吸取上层清液使用;(2)硫酸为酸化剂,为分析纯试剂并配制成不同浓度待用;(3)硫酸铁、硫酸铝、硫酸锌、硫酸铜、硫酸镁等金属盐,均为分析纯试剂.1.2 仪器(1)pHS -2C 数字式酸度计(每次测定pH 前,酸度计均经标准缓冲溶液校正);(2)加热恒温水浴温度为35?0.5e 、50?0.5e ;(3)磁力搅拌器.1.3 实验方法取给定浓度的单硅酸钠溶液15ml,置于试管中,再取酸化剂和蒸馏水合计15ml 的混合液置于另一试管中.将两试管在恒温水浴中恒温15min 后,取出立即倾入到有剧烈搅拌器搅拌的烧杯中,充分混和后分成二份:一份测定其pH 值,2min 后读数(每次测定前,pH 计均经标准缓冲溶液校正);另一份注入试管中,置于恒温水浴中继续恒温,并测定胶凝时间.从溶液混合开始到形成硅酸凝胶的判断标准为:将试管倾斜以凝胶不流动的时间为胶凝时间.对于金属离子的影响则为在硫酸酸化剂中加入一定量的硫酸金属盐后用蒸馏水稀至15m l,再与单硅酸钠溶液混合.2 结果分析2.1 单种金属离子的影响为研究金属离子对硅酸聚合的影响作用,实验选择M g 2+、Cu 2+、Al 3+、Fe 3+4种金属离子进行硅酸胶凝曲线测定.由于这些金属的硅酸盐均属于难溶性化合物,故实验时采用的金属离子浓度相对较低,且集中在酸性区域内进行.结果如图1所示.(a)镁、铜离子的影响(b)铝、铁离子的影响图1 单金属对硅酸聚合速度的影响从图1所示的结果可知,金属离子在不同的pH 值区域对硅酸聚合胶凝的影响作用不同.在pH <6,98北方交通大学学报第27卷即在酸性氛围中,实验的金属离子基本上是对硅酸的聚合胶凝具有抑制作用,使硅酸聚合胶凝的时间得以延长.但其影响作用的大小以及所处的pH 值范围对各金属离子的表现不尽相同.4种金属离子中以镁离子的阻凝效果最差,而铁和铝离子的阻聚效果相对较好.其中镁离子的阻凝区域位于pH 值2.5~ 3.5的之间,而铝和铜离子在pH >1.8时基本上表现为阻凝作用,但pH< 1.8时则就表现出一定的促凝作用,镁在pH 低于2.5时也表现为促凝作用.而铁离子在所选定的实验范围内基本上为阻凝作用,其中在pH 为2左右时其阻凝效果最佳.总之,实验的4种金属离子,其对硅酸聚合的抑制作用的大小顺序为Fe 3+>Al 3+>Cu 2+>Mg 2+.硅酸是一种弱酸,往单硅酸钠溶液中加入酸后,硅酸钠溶液中的单硅酸根离子将随着pH 值的降低而逐步质子化.依pH 值不同,其存在形态依次为:H 2SiO 2-4、H 3SiO -4、H 4SiO 4和H 5SiO +4.按照戴安邦教授[10]提出的硅酸聚合理论,硅酸聚合有两种机制:在酸性区域,硅酸存在的形式主要是H 3SiO -4和H 4SiO 4,硅酸聚合主要是硅酸分子和硅酸负离子间所进行的四配位的氧联反应,生成的反应产物可按同样机制进一步聚合成三聚体直至高聚物.在碱性区域,硅酸的聚合速度取决于H 4SiO 4浓度,将随着H 4SiO 4浓度的增加而增大.而在微酸性区域,硅酸的聚合速度取决于H 3SiO -4浓度.在硅酸聚合的酸性机制区,硅酸主要以H 4SiO 4存在,硅酸聚合则主要以六配位羟联反应进行,其聚合速度依H 5SiO +4浓度的增加而增大.季明德[11]认为:当硅酸溶液中有金属离子存在时,这些金属离子可与硅酸发生反应.在碱性机制区,硅酸的聚合速度取决于溶液中H 4SiO 4的浓度.硅酸在自身聚合的同时,硅酸负离子还将与金属离子发生反应M n++n H 3SiO -4=M(H 3SiO 4)n(1)M n++1/2n H 2SiO 2-4=M(H 2SiO 4)n/2(2)n >1时,形成的硅酸盐难溶于水,但适当控制金属离子和硅酸的浓度及溶液的pH 值,硅酸盐沉淀就可避免.M (H 3SiO 4)n 可与硅酸聚合,即M (H 3SiO 4)+n H 3SiO -4=(H 3SiO 4)n -1M (H 5Si 2O 7)+OH -(3)形成的产物还可与单硅酸进一步聚合直至形成高聚物.因此,在曲线最低点的右侧,[H 3SiO 4]->H 4SiO 4,硅酸的聚合速度随H 4SiO 4增加而增大.式(1)和式(2)均使硅酸负离子浓度降低,硅酸中性分子(含有金属离子的硅酸分子)浓度增加,故可加速硅酸的聚合反应.金属离子对硅酸的聚合将起促进作用,这一点也为图1的实验结果所证实.在胶凝聚合曲线最低点的左侧,[H 3SiO 4]-<H 4SiO 4,硅酸聚合速度随[H 3SiO -4]浓度增加而加快.若上述两反应在此区间显著发生,[H 3SiO 4]-的浓度将下降,这时外加盐的金属离子将起缓凝作用.这一点也为图1的实验结果所证实.聚合反应中将释放出氢氧根离子,而氢氧根已经证明其对硅酸聚合胶凝具有催化作用,使聚合速度加快.在选择的4种金属离子中,均能吸收氢氧根从而形成羟基络合物,其形成羟基络合能力的大小为:Fe 3+>Al 3+>Cu 2+>Mg 2+;特别是Fe 3+和Al 3+具有强烈的水解倾向,总是从溶液中捕获OH -离子,使溶液发生pH 弛豫现象,使溶液的pH 向低值方向移动,从而使硅酸的聚合速度降低,使胶凝时间延长.另一方面阻碍pH 值的变化,使pH 值不利于聚合反应的进行.由于这些金属离子对OH -的捕获能力随pH 的降低而减弱,故在pH<2时其对硅酸的阻聚效果也随之下降.铁离子等对硅酸聚合胶凝具有较好的阻聚效应的另一个原因是可以与硅酸间发生较强的配位络合作用.在4种离子中,铁、铝和铜离子能发生配位反应,而镁离子基本上不发生这类反应;以铁离子为例,在pH 等于3.5以下,铁离子与单体硅酸之间形成可溶性的络合物,即Fe 3++Si(OH)4Fe OSi(OH )2+3+H +(4)这就使一定量的硅酸被固定在铁硅络合物中,从而使硅酸的自聚效应因为络合作用的存在而得到抑制,表现出一定的缓凝效应.但对铁、铝金属离子而言,其对硅酸聚合的缓凝作用主要表现为对溶液pH 的缓冲效应上.99第6期许韵华等:金属离子对硅酸聚合胶凝影响的研究2.2 双金属组分的影响向聚硅酸溶液中同时引入两种金属离子,看其对硅酸胶凝的影响.图2(a)所示为引入铁、铜两种金属离子时的硅酸胶凝曲线,此时两金属离子的加入量相同,其和(mol 量)与铁离子的加入量相同.图2(b)为引入铁、铝两种金属离子时的硅酸胶凝曲线,此时两金属离子的加入量相同,其和(mol 量)与铁离子的加入量相同.从图2(b)也可以看出,由于铁离子的引入,在pH 大于2时,对硅酸的阻聚效应有所改善,但当pH 小于2时,仍表现出一定的促凝效应.这些说明,对抑制硅酸聚合而言,单组分金属离子要比双组份金属离子的要好些,也从另一方面说明铁离子是最好的硅酸阻抑剂.(a)铜铁离子(b)铝铁离子图2 双金属组份对硅酸聚合速度的影响从图2可以看出,用部分铝离子或铜离子代替部分铁离子后,其对硅酸的聚合阻抑效应并没有大的改善,相反随着pH 值的降低,却表现出明显的促凝效应.3 结语通过对选择的金属离子的研究表明:在不同的pH 值范围,金属离子对硅酸的聚合将产生不同的影响作用.其对硅酸的阻聚作用大小顺序为:Fe 3+>Al 3+>Cu 2+>M g 2+.其影响作用除表现在与硅酸的化学反应方面外,主要的是对溶液pH 值的缓冲效应.Fe 3+具有强烈的水解倾向,对羟基具有较好的捕获能力,减少了硅酸自聚合反应释放出OH -的影响作用;同时其与硅酸具有较强的配位络合能力,因而表现出良好的阻聚效应.参考文献:[1]汉迪化学品有限公司.聚合碱式硅硫酸铝[P].CN 1042340,1990-05-23.[2]张伯温,吴位能.聚合硅酸)盐絮凝剂及制备方法[P].CN 1050708,1991-04-17.[3]高宝玉,岳钦艳,王淑仁.含铝离子的聚硅酸絮凝剂研究[J].环境科学,1990,11(5):37-41.[4]桥本克,长谷川孝雄.一种水处理方法及其絮凝剂[P].CN 87101246,1988-09-21.[5]Hasegaw a T ,Hashimoto K ,O nitsuka T .Characteristics of M eta-l Po lysilicate Co agulants[J].Wat.Sci.T ech.,1991,23:1713-1722.[6]范德顺.商品活性硅酸助凝剂的生产技术[P].CN 1052294,1991-06-19.[7]栾兆坤,宋永会.聚硅酸金属盐絮凝剂的制备和絮凝性能[J].环境化学,1997,16(6):534-539.[8]Iler R K.T he Chemistry of Silica[M ].NY :T he John -W iley and Sons,1979.97.[9]Moulik S P,M ullick D K.Catalysis in the Polymer i zation of Silicic Aci d[J].Polymer Sci.(PART A-1),1966,4:811-820.[10]戴安邦,陈荣三.硅酸聚合理论的研究[J].南京大学学报(自然科学版),1964,8(1):80.[11]季明德.多价离子对硅酸聚合速度的影响[J].江西大学学报(自然科学版),1982,4:71-76.100北方交通大学学报第27卷。

英文文献翻译(聚硅氯化铝的电动特性凝固行为)

聚硅氯化铝（ PASiC ）的电动特性凝固行为（北京大学环境工程学院，环境科学与工程系，山东大学，济南250100 Email : bygao @sdu. edu. cn)摘要：电动特性和凝固行为的聚硅氯化铝（PASiC）和聚合氯化铝（PAC）进行了研究，并比较了流动电流（SC）的测量和JAR测试方法。

实验结果表明，相比较PAC，聚硅酸与带负电荷的铝水解产物相互作用减少了PASiC 电荷中和能力。

聚硅氯化铝（PASiC）盐基度（B）和Al / Si摩尔比的减少有着密切的关系。

聚硅氯化铝（PASiC）的电荷中和能力随B值和Al / Si摩尔比的降低而降低。

与此相反，制备工艺也会影响聚硅氯化铝（PASiC）的电荷中和能力。

此外，对比聚合氯化铝，聚硅氯化铝（PASiC）有更好的絮凝效果。

关键词：絮凝剂聚合氯化铝（PASiC）;流动电流（SC）;电动特性;混凝效果。

引言无机高分子絮凝剂在水和废水处理的絮凝过程一般涉及两个方面：一方面是研究水解聚合过程，物质在水中转化成无机金属盐，而另一方面是研究胶体粒子在水解过程中的不稳定因素。

因为在水中增加絮凝剂后胶体粒子与电荷密度是密切相关的，絮凝剂本身的不稳定电动特性是一个重要的的研究方面。

目前，调查电动特性和判断絮凝效果的方法有两个，分别是流动电流（SC）和微电脉测量技术（Black , 1965 ; Tang , 1995）。

微电泳测量技术是观察带电粒子在电场的时间速度后计算出Zeta电位的胶体粒子。

Zeta电位是一个重要的参数来表明胶体的电动特性，它可以被视为一种有效的指标来判断水中胶体粒子在加入絮凝剂后的破坏程度，也对观察絮凝剂的絮凝效果有所帮助。

然而，测量Zeta电位也存在着以下缺点：低精度，可重复性差，并且不能被用于在线监测和连续检测。

为了克服这些缺点，最近SC被广泛用于调查絮凝剂表面上胶体粒子的电动特性和电荷中和能力(Qu , 1997)，此外， Zeta电位反映的电荷中和能力为胶体分散，被称为分离弥漫层，而SC所研究的结果是分离弥漫层和固定层。

叔丁基取代水杨醛亚胺钛配合物的合成及其催化性能

科学研究2006,Vol.23N o.3化学与生物工程Ch emistry &B ioengin eerin g10 基金项目:湖北省教育厅技术创新项目(J200511001)收稿日期:2005-12-15作者简介:程正载(1967-),男,湖北天门人,博士生,从事金属有机催化研究。

叔丁基取代水杨醛亚胺钛配合物的合成及其催化性能程正载,伍林,吕早生,颜晓潮(武汉科技大学化工与资源环境学院,湖北武汉430081)摘要:以乙醇为溶剂,3,5 二叔丁基水杨醛与2,6 二异丙基苯胺通过希夫碱缩合得到3,5 二叔丁基水杨醛缩2,6 二异丙基苯胺配体I a,收率92 5%。

配体Ia 在四氢呋喃中分别与N aH 和T iCl 4 2T HF 反应得到相应的水杨醛亚胺钛配合物I 。

气相色谱-质谱联用(GC/M S)表征了配体结构,核磁共振氢谱(1HN M R )、元素分析等手段表征了配合物I 。

以甲苯为溶剂、M AO (甲基铝氧烷)为助催化剂,在25~75 钛配合物I 催化乙烯聚合活性较高(1 080!105~1 986!106g PE (mo l T i)-1 h -1),在55 达到最高。

所得聚乙烯粘均分子量在13 1!104~60 5!104之间,反应压力从0 2M Pa 提高到1 0M Pa,I /M A O 催化体系活性和聚合产物分子量能大幅提高。

G PC 和DSC 表征结果说明所得聚合物为窄分布低支化度聚乙烯。

关键词:水杨醛亚胺;钛配合物;乙烯聚合;催化剂中图分类号:O 627 文献标识码:A 文章编号:1672-5425(2006)03-0010-03近年来采用含苯氧基配体开发高性能聚烯烃催化剂成为配位聚合研究的热点[1]。

通过引入具有一定空间位阻和/或电子效应的取代基团对配体进行结构修饰,能裁剪配合物分子结构,制备出具有独特性能的高分子材料。

Wang 等[2]最早提出用水杨醛亚胺为配体骨架合成后过渡金属配合物催化乙烯聚合。

声子散射对载流子输运特性的影响

声子散射对载流子输运特性的影响吕英波【摘要】分析了晶格振动对固体材料中载流子输运特性的影响,重点阐述了长声学波对载流子的散射作用.使用玻尔兹曼输运理论描述了弱场下载流子的输运特性,给出了使用形变势散射和压电散射机制计算载流子迁移率的详细分析和具体公式.【期刊名称】《大学物理》【年(卷),期】2017(036)012【总页数】5页(P10-14)【关键词】迁移率;声子散射;形变势散射;压电散射【作者】吕英波【作者单位】山东大学(威海)空间科学与物理学院,山东威海264209【正文语种】中文【中图分类】O472+.4在固体材料包括各种半导体材料的研究中，载流子的输运特性一直是当前新型光电材料的一个热点研究问题.在半导体中带正电的空穴和带负电的电子在电场力的作用下会发生定向漂移，形成沿电场方向的电流 .载流子的迁移率μ用漂移速度和场强|E|表示载流子在导体或者半导体中传输时，除了受到电场力驱动的定向运动外，还受到持续的散射作用，使得载流子的运动方向不断改变.散射主要来源于晶界散射、杂质散射、缺陷散射和晶格振动散射等，它们在半导体材料的周期性势场之外引入附加势场ΔV，使得载流子在运动过程中遭遇散射.载流子在连续两次散射之间的时间平均值称为平均弛豫时间(〈τ〉).一般使用玻尔兹曼输运理论来描述弱场下载流子的输运特性，将弛豫时间近似和蒙特卡洛方法应用于玻尔兹曼输运方程的求解过程中，可得迁移率为[2]要提高载流子的迁移率，应该提高平均弛豫时间τ或者减小载流子的有效质量m*.传统的半导体材料如硅单晶的迁移率约为102～103cm2/V·s.目前人们希望获得迁移率更高的替代材料，如一维碳纳米管和二维石墨烯层状材料，因此就必须得清楚的了解载流子在材料中所遭受到的散射作用机制.目前学界研究较多且在固体材料中起到重要作用的散射机制为晶格振动/声子散射.因此声子散射是大学物理专业教学中非常重要的一个问题，本文给出声学声子散射的具体分析和计算方法.学生们如能对这个问题有清晰的认识，将非常有助于他们今后从事光电材料研发或者凝聚态物理相关领域的研究.晶格在平衡位置处的热振动使用格波表示.在三维晶格中，每一个格波的波矢q有3n个分支，其中频率最低的3支格波为声学波，频率高的3n-3支格波为光学波.每一支格波都含有1个纵波和2个横波.原胞中所有原子同向振动产生声学波，反向振动产生光学波.电子在晶体中被格波散射可视为电子与声子的碰撞.长声学波散射可近似看为弹性散射，而长光学波散射为非弹性散射.在长声学波中只有纵波在散射中起主要作用.长纵声学波会造成原子分布的疏密变化，使在一个波长中的原子中的一半处于压缩状态，另一半处于膨胀状态.半导体的禁带宽度会随着原子间距的变化而产生变化，如图1(c)所示.纵波引起的能带起伏产生了附加势场ΔE，这一附加势场破坏了原来势场的严格周期性，令电子从k状态散射到k′状态.声学波散射机制通过形变势散射和压电散射来主导迁移率.但是除非特别说明，一般声学声子散射就是指形变势散射.因为在氮化物中压电效应很明显，所以形变势散射和压电散射都必须考虑.一般来讲，在200 K以下形变势散射所占比重大于压电散射，但是在高温下压电效应变强.形变势散射在非极性半导体材料(如Si、Ge)中非常重要.声学声子振动引起晶格原子在平衡位置附近振动，这也意味着原子间距有轻微扰动，进而引起带宽的局域变化，如图1所示.因为带边能级位置的变化是由局域化的晶格形变引起的，所以称这种势能变化为形变势.它的大小就是单位体积变化导致的带边位置变化，通常用Edp或者Dac表示.载流子所遭遇到的形变势散射通常可由电子波动图像来解释[3].电子波遇到较高的势垒时，就会发生透射或者反射，这就是形变势散射的具体形式，如图1(d)所示.根据量子力学理论，在定量分析形变势散射的过程中：1) 不考虑横声学波的作用；2) 散射概率与电子态动量无关；3) 假设电荷输运方向平行于声子的传播方向.在弛豫时间近似下，将形变势理论和第一性原理能带计算以及玻尔兹曼输运理论结合起来，就可以很好的描述碳和有机系统等的输运特性.形变势散射的平均弛豫时间为因此由形变势散射决定的迁移率为[4-6]其中kB为玻尔兹曼常量，e为电子电荷的绝对值，T为温度，ћ为约化普朗克常量为态密度有效质量为电导有效质量，m*为能带有效质量，B为体弹性模量，Ξ为电子-声子耦合能量，由形变势来计算.Ξ代表了载流子和声子的作用，因此Ξ越小，表明载流子被声子散射的概率越小.ρ为材料的密度，s为声速.ΔEi为应力下带边能级的变化值，这里我们选择导带底和价带顶作为电子和空穴的能级.如果考虑载流子浓度的影响，则载流子浓度为f为费米狄拉克分布函数：ε为约化载流子能量，ξ=EF/kBT，为电子的约化化学势.NV为能带简并度(带边态密度方程的意义在于假设对输运性质有贡献的电子限制在费米能级10 kBT的范围之内.在三维晶体中，沿某个晶格方向的迁移率为其中β表示迁移率的方向(β=x, y, z).Cβ为β方向的弹性常数，纵声学波引起的Cβ可由下述公式表示：E0、V0和l0分别为平衡状态下晶体的能量、体积和β方向的晶格常数，而E、Δl 为沿着晶格β方向施加应力之后晶格的总能量和晶格常数的改变值.在这种情况下形变势的计算公式变为如果使用形变势散射模型来计算二维材料的迁移率，则[7，8]其中md=为状态密度平均有效质量.对于一维材料，迁移率公式变为[6]需要注意：在三维材料中Cβ的单位为J·m-3，而在二维材料中Cβ的单位为J·m-2，而在在一维材料中Cβ的单位为J·m-1.应力会使非中心对称的晶体材料中的正负电荷中心发生偏移，从而产生极化电场，这就是压电效应，如图2(a)所示.极化电场使得能带同时上升或下降，如图2(b)所示.这些能带的起伏变化同样会对载流子产生散射作用，形成压电散射.在这种散射作用中，横声学波和纵声学波都起到重要的作用.与形变势散射不同，压电散射中波矢q的方向也非常重要，而且q较小的声子散射中，压电散射的影响大于形变势散射的影响.在共价键为主的半导体中，波矢小的声子不能对载流子的动量进行有效的弛豫，所以在这种材料中形变势散射占主导地位.而在离子键为主或者压电效应比较明显的半导体(如GaN等)中，压电散射则居于主导地位.在低温下由压电散射来决定GaN或者GaN基二维电子气的载流子迁移率.压电散射的平均弛豫时间为[9-11]其中求和是针对纵波和横波模式进行求和，(K2)av的纵向分量和横向分量分别为其中el、et分别为纵向和横向压电应力常数，单位为分别为纵波和横波的球面平均值.cl和ct分别为纵波和横波的球面弹性常数，单位为GPa，m*的单位为me，εs为相对介电常量.1) 对于具有轴向对称性的晶格，如四方结构(4 mm)、纤锌矿和闪锌矿结构，压电应力常量e的纵向(沿r方向)分量[12，13]：而两个横向分量则分别为：他们的球面平均值则为[9]：(e31+2e15)2(e33-e31-e15)22) 对于正交晶格：对于三角晶系：横向弹性常数为Ct=ρ(vt)2=G，为剪切模量；纵向弹性常数为Cl=ρ(vl)2=B+(4/3)G，B为体弹性模量.1) 对于纤锌矿或闪锌矿[9]：2) 对于立方材料如RbCaX3(X= F和Cl)[15]3) 对于四方相晶体[16]：BR=[(2S11+S33)+2(S12+2S13)]-1BV= (2C11+C33)+(C12+2C13)B=GR=15[(4(2S11+S33)-4(S12+2S13)+3(2S44+S66)]-1GV= (2C11+C33-2C12-2C13)+(2C44+C66)G=其中S=1/C,称为弹性压缩系数，S13=[C13/C1]S33=[(C11+C12)/C1]S44=， S66=在固体材料中由于声学支格波具有与电子波动相同量级的波长，因此在载流子的输运过程中起到决定性的作用.声学支格波振动改变晶格点阵的位置，从而引入形变势散射和压电散射.本文根据玻尔兹曼输运理论详细分析了载流子的形变势散射和压电散射，并给出了迁移率的具体计算公式，这有助于应用物理专业的学生从事凝聚态物理的研究工作.【相关文献】[1] 黄昆，韩汝琦.固体物理[M].北京：高等教育出版社，1988: 292.[2] 刘恩科，朱秉生，罗晋升.半导体物理学[M].北京：电子工业出版社，2011：98.[3] Morkoç H. Devices Fundamentals and Applicat ions, in:Nitride Semiconductor Devices[M].Wiley-VCH Verlag GmbH & Co.KGaA, 2013:121.[4] Wang H, Pei Y, LaLonde A D, et al.Weak electron-phonon coupling contributing to high thermoelectric performance in n-type PbSe[J].PNAS,2012, 109: 9705.[5] Xi J, Long M, Tang L,et al. First-principles prediction of charge mobility in carbon and organic nanomaterials[J].2012, Nanoscale 4:4348.[6] Beleznay F B, Bogr F, Ladik J. Charge carrier mobility in quasi-one-dimensional systems: Application to a guanine stack[J].J Chem Phys, 2003, 119: 5690.[7] Bruzzone S, Fiori G. Ab-initio simulations of deformation potentials and electron mobility in chemically modified graphene and two-dimensional hexagonal boron-nitride[J].Appl Phys Lett, 2011, 99: 222108.[8] Qiao J, Kong X, Hu Z X, et al.High-mobility transport anisotropy and linear dichroism in few-layer black phosphorus[J].Nature communications, 2014, 5: 4475.[9] Vitanov S, Nedjalkov M, Palankovski V. in:Proceedings of the 6th international conference on Numerical methods and applications[J].Springer-Verlag, Borovets, Bulgaria, 2007: 197.[10] Kang N L, Choi S D. Scattering effects of phonons in two polymorphic structures ofgallium nitride[J].J Appl Phys, 2009, 106: 063717.[11] Hutson A R. Piezoelectric Scattering and Phonon Drag in ZnO and CdS[J].J Appl Phys,1961, 322287.[12] Zook J D. Piezoelectric Scattering in Semiconductors[J].Phys Rev,1964, 136: A869.[13] Kholkin A L, Pertsev N A, Goltsev A V. Piezoelectricity and Crystal Symmetry, in:A.Safari, E.K. (Eds.) Piezoelectric and Acoustic Materials for TransducerApplications[M].Boston:Springer 2008:23.[14] Feng J. Mechanical properties ofhybrid organic-inorganic CH3NH3BX3 (B= Sn, Pb; X= Br, I) perovskites for solar cell absorbers[J].Apl Materials, 2014, 2: 081801.[15] Mubarak A A. The elastic, electronic and optical properties of RbCaX3 (X= F, Cl) compounds[J].Int.J.Mod.Phys.B, 2014, 28: 1450192.[16] 丁建刚，冯丽萍，刘其军，等.四方晶相SrHfO3弹性性质、电子结构和光学性质的第一性原理计算[J].应用物理, 2014, 1: 64.。

磷原子在金刚石(001)表面吸附和迁移的第一性原理研究

磷原子在金刚石(001)表面吸附和迁移的第一性原理研究刘学杰;曹晔【摘要】采用第一性原理计算方法对磷原子在金刚石(001)表面上的吸附和迁移行为进行了系统研究.结果表明:在全氢终止金刚石(001)表面上,磷原子不能够稳定吸附.当氢终止表面上出现1个、2个活性位时,磷原子可以在活性位处稳定吸附,吸附能为2.8至4.5 eV.分波态密度分析表明:磷原子吸附后,仍然有未成对电子,保持化学活性,有利于后续沉积粒子的吸附.当氢终止表面上出现3个活性位时,磷原子可以在活性位处吸附,并且可以在活性位之间迁移.迁移激活能小于1.7 eV.综上所述,磷原子在金刚石(001)表面上的吸附和迁移行为与表面上活性位的数量和分布密切相关.【期刊名称】《内蒙古科技大学学报》【年(卷),期】2019(038)002【总页数】8页(P131-138)【关键词】第一性原理;磷掺杂金刚石;迁移激活能;吸附和迁移【作者】刘学杰;曹晔【作者单位】内蒙古科技大学机械工程学院,内蒙古包头 014010;内蒙古科技大学机械工程学院,内蒙古包头 014010【正文语种】中文【中图分类】O647.3磷掺杂金刚石薄膜用于许多领域，如：制备n型半导体[1]、热电子发射[2-3]、场发射[4-6]、制备双极结型晶体管[7]等.磷被认为是n型掺杂金刚石最有潜力的施主元素，能级位于导带底以下0.58 eV，在金刚石薄膜中可以形成较低的施主能级[8]磷掺杂金刚石薄膜的实验研究，重点是考察磷掺杂浓度、载流子浓度和迁移率[1,9-11].文献[12]报道了在磷浓度为2×1015 cm-3时薄膜在室温下的电子迁移率为1 000 cm2/V·s，掺入效率为0.1%.文献[13]指出磷浓度为1016 cm-3时，霍尔迁移率可达到660 cm2/V·s.文献[14]表明采用微波等离子体在硅基底上沉积n型磷掺杂多晶金刚石，二次质谱测得的磷浓度至少为1017 cm-3；阴极发光和拉曼效应光谱证实，当晶粒尺寸减小时，残余压应变强度在降低，结晶质量得到改善.文献[15]报道，利用微波等离子体在(111)金刚石表面上进行重磷掺杂结果表明：在1020 cm-3高的掺杂浓度下，可以将施主活化能从0.58 eV降低到0.05 eV.通过优化生长参数，制备出了室温下电阻率为120～150 Ω·cm，活化能为0.027 eV的重磷掺杂金刚石薄膜.磷掺杂金刚石薄膜的生长率一般在1 μm/h左右[15-16]，也有生长速率达到33μm/h的情况[17].文献[18]指出添加2 000×10-6的PH3可使薄膜生长速率提高2～3倍，并有利于(100)晶粒的生长；但在较高的PH3浓度0.3%～0.5%下，生长速率再次降低，且晶粒主要是(111)取向.对磷掺杂金刚石的实验研究结果表明：工艺参数会影响薄膜的微观结构以及薄膜性能和质量.因此，有必要采用第一性原理方法研究磷掺杂金刚石薄膜的生长.关于磷掺杂的第一性原理计算基本上是研究磷掺入金刚石后电子结构的情况和施主的活化能[19-20].本文采用第一性原理计算研究磷原子在氢终止金刚石(001)表面上吸附和迁移性能.针对钝化表面和具有不同数量活性位的表面，系统研究磷原子的吸附能势能面和迁移激活能.并根据电荷转移、态密度和磁矩计算结果，分析磷原子吸附后的活性.1 计算方法本文采用基于密度泛函(DFT)理论的VASP[21](Vina Ab-initio Simulation Package)软件包来进行第一性原理计算.用投影缀加平面波赝势(PAW)[22]描述离子与电子间的相互作用.采用基于PBE[23](Perdew Burke Enzerhoff)泛函的广义梯度近似(GGA)来计算电子密度的分布情况.采用基于Monkhorst-Pack方法[24]的5×5×1 k点网格来做布里渊区积分.计算中截断能定为350 eV.所有的计算都采用了自旋极化.电子和离子弛豫收敛精度分别为10-4和10-3 eV.采用VASP中的NEB方法来计算原子在金刚石(001)表面的最小迁移激活能.采用一个4×4×(1+8+1+16)模型模拟氢终止金刚石(001)表面.该模型包括8个碳(C)原子层，每层有(4×4)16个碳原子；在碳原子层的上下各覆盖1个氢层；再加上16个真空层.真空层厚度为1.28 nm，用以防止超胞模型的周期性干扰.计算时将模型最下面3层的碳原子固定，其它层的碳原子可以自由地移动.经弛豫后，氢终止金刚石(001)表面发生了重构.在氢终止金刚石(001)的重构表面上有6个高对称位，如图1(a)和图2(b)所示.将沉积的磷(P)原子分别放置于6个位置松弛下落，以计算磷原子的吸附能.图1 6个高对称位和重构的氢终止金刚石(001)表面模型上的活性位Fig.1 The active sites on the six high symmetrysites and the reconstructed hydrogen terminateddiamond (001) surface model(a)主视图和(b)俯视图显示6个高对称位；(c)在A，B，C，D和E位移除氢原子则在表面出现活性位图1(c)显示在氢原子萃取后，表面上出现活性位的分布情况.当C位的氢原子被移除，该构型是具有1个活性位的氢终止金刚石(001)表面模型，记为1ORS；当A和C位的氢原子被移除，该构型是沿着二聚体列方向具有2个活性位的表面模型，记为2ORS-R；当C和D位的氢原子被去除，该构型是沿着二聚体链开环侧具有2个活性位的表面模型，记为2ORS-CO；当B和C位的氢原子被去除，该构型是沿着二聚体链闭环侧具有2个活性位的表面模型，记为2ORS-CC.当A，C和E位的氢原子被移除，该构型是沿着二聚体列具有3个活性位的表面模型，记为3ORS-R；当B，C和D位的氢原子被去除，该构型是沿着二聚体链具有3个活性位的表面模型，记为3ORS-C.2 结果和讨论2.1 在全氢终止金刚石(001)表面根据吸附能公式(1)可以计算磷原子的吸附能Ead，见式(1)：Ead=-(Etot-Eslab-nEP).(1)式中：Etot为磷原子吸附后的模型总能；Eslab为不包含沉积磷原子的氢终止金刚石表面构型总能；EP为单个磷原子的能量；n为吸附磷原子个数.由式(1)所计算出的单个磷原子在全氢终止的金刚石(001)表面的吸附能列在从表1中.从表1中数据显示，在P5位置磷原子没有与表面原子结成键.在其它的5个位置虽然吸附能为正值，但吸附能值很低，是范德瓦尔斯力的相互作用，属物理吸附.我们验证了范德瓦尔斯力对吸附能大小的影响，计算结果表明：范德瓦尔斯力对物理吸附影响非常小，对化学吸附几乎无影响.在P3位置，磷原子的吸附能最大，但也仅为0.033 eV，此时磷原子与表面碳原子间的距离为4.03×10-10 m，这比碳原子、磷原子的共价半径之和1.83×10-10 m大很多.表明磷原子没有和金刚石表面的碳原子成键.表1 单个磷原子在全氢终止的金刚石(001)表面的吸附能Table 1 Adsorption energy of a single phosphorus atom on the surface of the fully hydrogen terminated diamond (001)位置P1P2P3P4P5P6Ead/eV0.0250.0260.0330.028脱附0.027由以上数据和分析可以得出结论：磷原子不能稳定地吸附在全氢终止的金刚石(001)表面.其原因是表面的碳原子和氢原子结合已经达到稳定饱和状态.2.2 在1ORS的表面图2(a)为磷原子在此构型中吸附能的势能面(PES).在P4和P6位置时，吸附能为负值，磷原子在表面解吸.在P3位置时，吸附能很小为0.578 eV，是物理吸附.在P1和P2位置吸附能分别达到了1.796 eV和2.511 eV，表明磷原子可以与表面的碳原子成键，键长分别为1.85×10-10 m和1.86×10-10 m，与碳、磷原子的共价半径之和1.83×10-10 m基本相同.图2(b)和图2(c)分别展示了磷原子在P2位置吸附前和吸附后的差分电荷密度图.红色区域代表电荷密度的增加，蓝色区域代表电荷密度的减少.从图2(c)中可以看出与磷原子最近邻的碳原子CNN和磷原子之间聚集了电荷，表明磷原子已与表面的碳原子成键.表2列出磷原子在P2位置吸附前和吸附后的电荷量和磁矩变化.电荷转移量的大小与原子的电负性大小密切相关.碳原子的电负性为2.55.磷原子的电负性为2.19.因此，在它们之间发生了电荷转移时，碳原子的电荷量增加了0.253电子，磷原子的电荷量减少了0.323电子.磷原子吸附后，碳原子的磁矩变为-1.020×10-25 A·m2，而磷原子的磁矩变为0.751×10-24 A·m2.这表明：磷原子吸附后，仍有未配对的电子，保持了活性.图2(d),2(e)和2(f)展示了磷原子吸附在P2位时，CNN原子和磷原子的分波态密度(PDOS).由图2可知，磷原子的电子上旋和下旋明显不对称，表明磷原子存在未成对的电子，为其它粒子或基团提供了键合的机会.由图2(f)可知，CNN原子和磷原子的p轨道在-0.42 eV处形成了态密度共振.表明CNN原子和磷原子之间存在着较强的相互作用，也证明了2个p轨道结合成键.图2(a)中可以看出磷原子在P5位有比较大的吸附能.在P5位置，磷原子会萃取附近的氢原子，并与下方的2个碳原子成键.表3列出了磷原子在P5位置吸附的电荷量和磁矩变化数据.CNN原子和氢原子的电荷量分别增加了0.17，0.404和0.429电子，磷原子的电荷量减少了0.86电子.吸附后各原子的磁矩均变为0 A·m2，表明该系统中所有粒子都没有未配对的电子，均达到饱和状态.图2 PES、差分电荷密度图和P及CNN原子在1ORS模型的PDOSFig.2 PES,differential charge density map,and PDOS of P and CNN atoms in1ORS(a)1ORS 构型的PES；(b)P原子吸附前P2位的差分电荷密度图(截面图)；(c)P原子吸附后P2位的差分电荷密度图(截面图)；(d)P2位CNN原子的PDOS；(e) P2位P原子的PDOS；(f)P2位CNN原子的2p轨道和P原子的3p轨道的PDOS.表2 在1ORS模型P2位置P原子吸附前后CNN原子和P原子的电荷量和磁矩Table 2 Charge and magnetic moments of CNN and P atoms before andafter P atom adsorption at the P2 position of the 1ORS model吸附前吸附后电荷(e)磁矩/(A·m2)电荷(e)磁矩/(A·m2)CNN原子4.1543.857×10-244.407-1.020×10-25P原子5.0001.108×10-234.6777.001×10-24表3 磷原子在P5位置吸附前后CNN原子、P原子和H原子的电荷量和磁矩Table 3 Charge and magnetic moment of CNN, P and H atoms before andafter adsorption of phosphorus atom at P5 position吸附前吸附后电荷量(e)磁矩/(A·m2)电荷量(e)磁矩/(A·m2)CNN1原子4.1543.875×10-244.3240CNN2原子3.9211.113×10-254.3250P原子5.0001.108×10-234.1400H原子0.97101.4000由以上分析表明：磷原子不能稳定吸附在全氢的氢终止金刚石(001)表面，但可以稳定吸附在具有活性位的氢终止金刚石(001)表面，这表明磷原子会在全氢终止的金刚石表面迁移，当遇到1个活性位，就会在此活性位处稳定吸附下来.2.3 在2ORS的表面图3(a)为磷原子在2ORS-R构型中的势能面(PES).由图3(a)可知，将磷原子放置在P5位置时吸附能最大，达到了4.132 eV.此时磷原子与表面的两个碳原子成键，键长均为1.93×10-10 m，比碳、磷原子的共价半径之和稍长.在P2位时，吸附能次最大，为2.54 eV，此时磷原子与其正下方的碳原子成键，键长为1.85×10-10 m，与它们的共价半径相近.在其余位置处吸附能都很小，属于物理吸附.图3(b)和图3 (c)分别为磷原子在2ORS-R构型P5位置吸附前和吸附后的差分电荷密度图.由图3(c)中可以看出磷原子和CNN原子之间有电荷聚集，并且偏向CNN原子，说明磷原子已和表面的CNN原子成键.图3(d)，3(e)和3(f)展示了磷原子在2ORS-R构型中P5位置时，CNN原子和磷原子的分波态密度.由图可知，磷原子的电子上旋和下降明显不对称，表明磷原子存在未成对的电子，为后来的碳粒子或碳氢基团提供了吸附的机会.由图3(f)可知CNN原子和磷原子p轨道在-0.7 eV处形成了态密度共振，说明CNN原子和磷原子之间相互作用，两个p轨道结合成键.表4列出了磷原子在2ORS-R构型中P5位置吸附前后CNN原子和磷原子电荷量及磁矩.由表4可知磷原子吸附后，碳原子的电荷量都增加了0.192电子，而磷原子的电荷量减少了0.49电子.吸附后，碳原子的磁矩几乎变为0 A·m2，而磷原子的磁矩变为3.533×10-24 A·m2，表明CNN原子已经达到饱和状态，而磷原子还有未成对电子，保持了活性.图3 PES、差分电荷密度图和2ORS-R的C原子和P原子的PDOSFig.3 PES, differential charge density map,and PDOS of 2ORS-R C and Patoms(a)2ORS-R构型的PES；(b)P原子吸附前P5位的差分电荷密度图(截面图)；(c)P原子吸附后P5位的差分电荷密度图(截面图)；(d)P5位CNN原子的PDOS；(e)P5位P原子的PDOS；(f)P5位CNN原子的2p轨道和P原子的3p轨道的PDOS.表4 在2ORS-R模型P5位置P原子吸附前后CNN原子与P原子的电荷量和磁矩Table 4 Charge and magnetic moments of CNN and P atoms before andafter P atom adsorption at P5 position of 2ORS-R model吸附前吸附后电荷量(e)磁矩/(A·m2) 电荷量(e)磁矩/(A·m2)CNN1原子4.1454.033×10-244.337-7.418×10-26CNN2原子4.1454.033×10-244.337-7.418×10-26P原子5.0001.108×10-234.510-3.533×10-24图4(a)为磷原子在2ORS-CO中的势能面，由图可知，当磷原子在P3位置时吸附能最大，为4.125 eV，此时磷原子与表面的2个碳原子成键.磷原子在P5位置的吸附能为2.93 eV，在此位置磷原子会萃取附近的氢原子，并与邻近的2个碳原子成键.在P1，P2位的吸附能分别为1.8 eV和2.5 eV，磷原子可与表面的碳原子成键.其余位置吸附能很小，为物理吸附.图4(b)为单个磷原子在2ORS-CC中的势能面，由图可知，当把磷原子放在P1位时吸附能最大，达到了4.28 eV，磷原子与处于同一个二聚体上的2个碳原子成键.在P2位置时，磷原子与其正下方的碳原子成键，吸附能达到较大值3.60 eV.在P5位置时，磷原子会萃取邻近的氢原子并与下方的2个碳原子成键，吸附能为2.975 eV.将磷原子放在P3，P4和P6位置时吸附能较小，且磷原子与表层碳原子的距离也较大(2.2×10-10～3.4×10-10 m)，所以磷原子不能稳定吸附在P3，P4和P6位置.磷原子在2ORS-CO中P3位、2ORS-CC中P1位吸附前后电荷量、磁矩的变化与ORS-R中P5位相近，PDOS图也相似，表明吸附后磷原子存在未成对的电子，保持了活性，有利于后来的碳粒子或碳氢基团的吸附.图4 PESFig.4 PES of P atom in 2ORS-CO and in 2ORS-CC(a)磷原子在2ORS-CO中的PES；(b)磷原子在2ORS-CC中的PES2.4 在3ORS的表面图5为单个磷原子在3ORS-C和3ORS-R中的势能面.当图1(c)中去除B，C和D位的氢原子是3ORS-C的构型，相当于2ORS-CO与2ORS-CC的合并.图5(a)显示，磷原子在3ORS-C中P1位置的吸附能最大，为4.597 eV，此时磷原子与表面的2个碳原子成键，键长均为1.84×10-10 m.在P2和P3位置时，磷原子也可以与表面的碳原子成键，键长分别为1.80×10-10 m和2.03×10-10 m.在P5位置时，磷原子会萃取附近的1个氢原子并与表面的2个碳原子成键，碳、磷原子的键长为1.96×10-10 m.在P4和P6位时，吸附能较小，为物理吸附.当图1(c)中移除A，C和E位的氢原子是3ORS-R构型，相当于2个2ORS-R相连.图5(b)显示磷原子3ORS-R在A位置与C位置之间的势能面，它与2ORS-R 中的势能面图3(a)基本相同，各个位置的吸附能也相差无几，其成键情况也一样. 图5 PESFig.5 PES of P atom in 3ORS-C and in 3ORS-R(a)磷原子在3ORS-C 中的PES；(b)磷原子在3ORS-R中的PES由PES图5中可以确定出磷原子在3ORS-C和3ORS-R中的迁移路径.在3O4S-C 中，磷原子将从P3位经P2位迁移到P1位.在3ORS-R中，磷原子将从P5位迁移到P2位然后再滑向图1(c)C位置与E位置之间的P5'位.利用VASP中的NEB 文件，沿迁移路径计算了迁移过程中系统能量的变化，绘制了最小迁移能量曲线，如图6所示.图6 (a)3ORS-C中磷原子的迁移曲线(b)3ORS-R中磷原子的迁移曲线Fig.6 Migration curve of phosphorus atom in 3ORS-C and in 3ORS-R根据图6可以得出以下结论：在3ORS-C表面上，磷原子从P3位到P1位时，需要1.356 eV的能量来越过Ⅱ位置然后滑向P1位；当磷原子从P1位迁移到P3位时，其激活能为1.717 eV.在3ORS-R表面上，磷原子从P5位迁移到P2位，需要1.587 eV的激活能；当磷原子从P2位迁移到P5'位时，磷原子自发的从P2位下滑到Ⅳ'位，然后需要0.176 eV的能量跨过Ⅲ'位置，最终滑向P5'位.由此可以看：出磷原子需要1.717 eV的激活能就可以在具有3个活性位的氢终止金刚石(001)表面进行迁移.3 结论(1)在全氢终止的金刚石(001)表面上，磷粒子不能够稳定吸附.(2)当氢终止表面上出现1个、2个活性位时，磷粒子可以在活性位处稳定吸附，吸附能为2.8～4.5 eV.PDOS分析表明：磷粒子吸附后，仍然有未成对电子，保持化学活性，这有利于后续沉积粒子的吸附.(3)当氢终止表面上出现3个活性位时，磷粒子可以在活性位处吸附，并且可以在活性位之间迁移.迁移激活能小于1.7 eV.按照Arrhenius迁移率计算公式[25]，在通常的金刚石膜沉积温度下，磷粒子比较容易迁移.参考文献：【相关文献】[1] OKANO K , KIYOTA H , IWASAKI T , et al. Synthesis of n-type semiconducting diamond film using diphosphorus pentaoxide as the doping source[J]. Applied Physics A (Solids and Surfaces), 1990, 51(4):344-346.[2] KATAOKA M , MORIOKA N , KIMURA Y , et al. Enhanced thermionic electron emission from a stacked structure of phosphorus-doped diamond with a nitrogen-doped diamond surface layer[J]. physica status solidi (a), 2016, 213(10):4.[3] YAMADA T . Heavily phosphorus-doped nano-crystalline diamond electrode for thermionic emission application[J]. Diamond & Related Materials, 2016, 63:165-168. [4] SUGINO T , KURIYAMA K , KIMURA C , et al. Field emission from phosphorus-doped polycrystalline diamond films[J]. Journal of Applied Physics, 1999, 86(8):4635.[5] MASUZAWA T , KUDO Y , MIMURA H , et al. Modification of internal barrier in hydrogen-terminated heavily phosphorus-doped diamond for field emission[J]. physica status solidi (a), 2016.[6] KATO H , MAKINO T , OGURA M , et al. 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Diamond and Related Materials, 2005, 14(11-12):2007-2010.[12] KATO H , OGURA M , MAKINO T , et al. n-Type control of single-crystal diamond films by ultra-lightly phosphorus doping[J]. Applied Physics Letters, 2016, 109(14):142102. [13] KATAGIRI M , ISOYA J , KOIZUMI S , et al. Lightly phosphorus-doped homoepitaxial diamond films grown by chemical vapor deposition[J]. Applied Physics Letters, 2004,85(26):6365-6367.[14] GHODBANE S , OMNES, F, BUSTARRET E , et al. n-Type phosphorus-doped polycrystalline diamond on silicon substrates[J]. Diamond and Related Materials, 2008,17(7-10):1324-1329.[15] GROTJOHN T A , TRAN D T , YARAN M K , et al. Heavy phosphorus doping by epitaxial growth on the (111) diamond surface[J]. Diamond and Related Materials, 2014, 44:129-133.[16] MAIDA O , TADA S , ITO T. High growth rate deposition of phosphorus-doped homoepitaxial (001) diamond films for deep-ultraviolet light emitting device[J]. Thin Solid Films, 2014, 557:227-230.[17] BALASUBRAMANIAM Y , POBEDINSKAS P , JANSSENS S D , et al. Thick homoepitaxial (110)-oriented phosphorus-doped n-type diamond[J]. Applied Physics Letters, 2016 , 062105:1-4.[18] TSANG R S, MAY P W , ASHFOLD M N R , et al. Influence of phosphine on the diamond growth mechanism: a molecular beam mass spectrometric investigation[J]. Diamond and Related Materials, 1998, 7(11-12):1651-1656.[19] 王广文, 邵庆益. 磷掺杂金刚石薄膜的电子结构及空位对其的影响[J]. 中国科学:物理学力学天文学，2010，(7):869-875.[20] CZELEJ K . Electronic structure and n-Type doping in diamond from first principles[J]. Mrs Advances, 2016, 1(16):1093-1098.[21] KRESSE G, HAFNER J. Ab initio molecular dynamics for liquid metals[J]. Phys Rev B Condens Matter, 1993, 48(17):13115-13118.[22] BLOCHL P E. Projector augmented-wave method[J]. Phys Rev B Condens Matter, 1994, 50(24):17953-17979.[23] PERDEW J P, BURKE K, ERNZERHOF M. Generalized gradient approximation made simple[J]. 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Phosphorus-containing epoxy resin for an electronic application

Phosphorus-Containing Epoxy Resin for an Electronic ApplicationCHUN-SHAN WANG,JENG-YUEH SHIEHDepartment of Chemical Engineering,National Cheng Kung University,Tainan,Taiwan,701,Republic of ChinaReceived25July1998;accepted23September1998ABSTRACT:A phosphorus-containing epoxy resin,6-H-dibenz[c,e][1,2]oxaphosphorin-6-[2,5-bis(oxiranylmethoxy)phenyl]-6-oxide(DOPO epoxy resin),was synthesized andcured with phenolic novolac(Ph Nov),4,4Ј-diaminodiphenylsulfone(DDS),or dicyan-diamide(DICY).The reactivity of these three curing agents toward DOPO epoxy resinwas found in the order of DICYϾDDSϾPh Nov.Thermal stability and the weight lossbehavior of the cured polymers were studied by TGA.The phosphorus-containing epoxyresin showed lower weight loss temperature and higher char yield than that of bisphe-nol-A based epoxy resin.The high char yields and limiting oxygen index(LOI)valuesas well as excellent UL-94vertical burn test results of DOPO epoxy resin indicated theﬂame-retardant effectiveness of phosphorus-containing epoxy resins.The DOPO epoxyresin was investigated as a reactiveﬂame-retardant additive in an electronic encapsu-lation application.Owing to the rigid structure of DOPO and the pendant P group,theresulting phosphorus-containing encapsulant exhibited betterﬂame retardancy,higherglass transition temperature,and thermal stability than the regular encapsulantcontaining a brominated epoxy resin.High LOI value and UL-94V-0rating could beachieved with a phosphorus content of as low as1.03%(comparable to bromine contentof7.24%)in the cured epoxy,and no fume and toxic gas emission were observed.©1999John Wiley&Sons,Inc.J Appl Polym Sci73:353–361,1999Key words:phosphorus-containing epoxy resin;6-H-dibenz[c,e][1,2]oxaphosphorin-6-[2,5-bis(oxiranylmethoxy)phenyl]-6-oxide;phenolic novalac;4,4Ј-diaminodiphenyl-sulfone;dicyandiamide;bisphenol-A;ﬂame retardant;limiting oxygen index;UL-94VtestINTRODUCTIONEpoxy resins have excellent moisture,solvent and chemical resistance,low shrinkage on cure,supe-rior electrical and mechanical properties,and good adhesion to many substrates.The versatility in formulation also makes epoxy resins widely applicable industrially for surface coatings,adhe-sives,painting materials,pottings,composites, laminates,encapsulants for semiconductors,and insulating materials for electric devices,etc.1–4 However,the common epoxy systems cannot sat-isfyﬁeld applications that require high thermal andﬂame resistance.Considerable environmen-tal attention and health restrictions have been considered in the last three decades in regard to controlling inherentﬂammability of common or-ganic polymer by incorporation ofﬁre-retardant additives.Several approaches for modiﬁcation of the epoxy backbone to enhance the thermal prop-erties of epoxy resins have been reported.5–8 Flame retardants such as tetrabromobisphenol A,phosphorus–halogen mixtures,ammonium phosphate,and organophosphorus compounds have been used to impartﬂame retardancy to epoxy resins.9–12In aﬁre,halogens(i.e.,of broCorrespondence to:C.-S.Wang.Contract grant sponsor:National Science Council of the Re-public of China;contract grant number:NSC87-2622-E006-001.Journal of Applied Polymer Science,Vol.73,353–361(1999)©1999John Wiley&Sons,C0021-8995/99/030353-09353mine and chlorine)produce problems of smoke and possibly enhanced toxicity,and corrosion.Or-ganic phosphates have less tendency to cause these problems.Recently,organophosphorus compounds have demonstrated good ability as ﬂame retardants for epoxy resins,and also have been found to generate less toxic gas and smoke than halogen-containing compounds.13–21Flame-retardant epoxy resins can be obtained by chem-ically bondingﬂame-retardant groups onto epoxy resins,and the permanent attachment of aﬂame retardant frequently leads to high efﬁciency in ﬂame retardancy.17–18,22–23In this study,a rigid phosphorus-containing reactive2-(6-oxido-6-H-dibenzo[c,e][1,2]oxaphos-phorin-6-yl)-1,4-benzenediol(ODOPB)is con-verted to a phosphorus-containing epoxy resin, 6-H-dibenz[c,e][1,2]oxaphosphorin-6-[2,5-bis-(oxiranylmethoxy)phenyl]-6-oxide(DOPO epoxy resin),which is expected to exhibit the required ﬂame retardancy,less fumes,and higher thermal stability than the conventionalﬂame-retardant epoxy resin systems containing tetrabromobis-phenol A(TBBA).EXPERIMENTALReagentsODOPB was prepared in our laboratory.26Epi-chlorohydrin(EPI)from Janssen Co.and potas-sium hydroxide from Showa Co.were used as received.All solvents were reagent grade or were puriﬁed by standard methods before use.The dig-lycidyl ether of bisphenol-A[Bis-A epoxy resin, epoxy equivalent weight(EEW)ϭ189]was ob-tained from Chang Chun Plastic Co.(Taiwan). 4,4Ј-Diaminodiphenylsulfone(DDS)and dicyan-diamide(DICY)used as curing agents were from Aldrich and used as received.A phenol-formalde-hyde novolac resin(Ph Nov)with an average hy-droxyl functionality of6and a hydroxy equivalent weight of about104(Schenectady Chemical,HRJ-2210)was also used as a curing agent.The A-1 catalyst was(ethyl)triphenyl phosphonium ace-tate acetic complex;Ph3P was triphenylphos-phine,which was used as curing accelerator. InstrumentalInfrared spectra(IR)were obtained using a Nico-let550Fourier Transfer Infrared Spectrophotom-eter.Mass spectra were recorded by a VG70-250s gas chromatography/mass spectroscopy.Differen-tial scanning calorimetry(DSC)data were ob-tained in a nitrogen atmosphere at a20°C minϪ1 heating rate using a Perkin-Elmer DSC7differ-ential scanning calorimeter.Thermal gravimetric analysis(TGA)was employed with a Perkin-Elmer TGA7at a heating rate of20°C minϪ1in nitrogen or air atmosphere.Limiting oxygen in-dex(LOI)values were measured on an ATLAS limiting oxygen index chamber.The percentage of O2in the O2–N2mixture just sufﬁcient to sus-tain theﬂame was taken as the LOI.EEW of DOPO epoxy resin was determined by the HClO4/ potentiometric titration method.Synthesis of DOPO Epoxy ResinInto a1-L reaction vessel equipped with temper-ature and pressure controls and indicators, means for the continuous or intermittent addition of aqueous sodium hydroxide,means for condens-ing and separating water from a codistillate mix-ture of water,solvent,and epichlorohydrin,and means for returning the solvent and epichlorohy-drin to the reaction vessel was added64.8g(1 equivalent)of ODOPB,185g(5equivalents)of epichlorohydrin,and54g of the methylether of propylene glycol(1-methoxy-2-hydroxypropane) as a solvent.After stirring at room temperature and atmospheric pressure to thoroughly mix the contents,the temperature was raised to65°C and the pressure was reduced to160mm Hg absolute. To the resultant solution was continuously added 8g,2equivalents of a50%aqueous sodium hy-droxide solution at a constant rate over a period of 1h.During the addition of the sodium hydroxide, the water was removed by codistilling with epi-chlorohydrin and solvent.The distillate was con-densed,thereby forming two distinct phases,an aqueous phase(top)and an organic epichlorohy-drin–solvent phase(bottom).The organic phase was continuously returned to the reactor.After completion of the sodium hydroxide addition,the reaction mixture was maintained at a tempera-ture of65°C and a pressure of about160mm Hg absolute for an additional30min.A sample of the reaction mixture was washed to remove salt and subsequently distilled resulting in an epoxidized ODOPB resin(DOPO epoxy resin)having a hy-drolyzable chloride content of0.02%and an epox-ide content ofϳ23.5%,which corresponds to an epoxide equivalent weight of about223ϳ228. Curing Procedure of Epoxy ResinsThe thermal andﬁre retardant properties of the phosphorus-and nonphosphorus-containing epoxy354WANG AND SHIEHresin were evaluated by preparing six cured epoxyresins,i.e.,DOPO epoxy resin cured with Bis-A/PhNov,DOPO/Ph Nov;Bis-A/DDS,DOPO/DDS,Bis-A/DICY,DOPO/DICY.To obtain a highlycrosslinked polymer with good thermal stability,one epoxy equivalent weight of the epoxy resinswas cured with one functional equivalent weightof the curing agents.Curing steps were predeter-mined by DSC thermograms of respective epoxy/curing agent compositions(Table I). Preparation of DOPO Epoxy Resin Modified EncapsulantsTo determine the amount of phosphorus neededto achieveﬂame retardancy,various amount ofDOPO epoxy resin was added to Bis-A epoxy resinand cured with Ph Nov.The mixtures of epoxyresins consisted of Bis-A epoxy/DOPO epoxy(orBis-A epoxy/TBBA epoxy)in various weight ra-tios(87.5/12.5,77.8/22.2,71.4/28.6)were pre-pared.Ph3P was used as a curing accelerator.Each epoxy mixture was mixed with Ph Nov and0.2%Ph3P in a mill at25°C to give thermoset-table epoxy resin powders.The resin powderswere cured in a mold at150°C and50kg/cm2fora period of1h and then at185°C for2h,andfurther postcured at210°C for3h to obtain curedspecimens.LOI and UL-94V Flame Retardant TestThe LOI is the minimum fraction of O2in a mix-ture of O2and N2that will just supportﬂamingcombustion.The LOI test was performed accord-ing to the testing procedure of ASTM D2836Oxygen Index Method with test specimen bar of7–15cm in length,6.5Ϯ0.5mm in width,and3.0Ϯ0.5mm in thickness.Ten sample bars sus-pended vertically were ignited by a Bunsenburner.Theﬂame was removed and the timerwas started.The concentration of oxygen was raised if the specimen extinguished before burn-ing3min or5cm.The oxygen content was ad-justed until the limiting concentration was deter-mined.The UL-94V test was performed according to the testing procedure of FMVSS302/ZSO3975 with test specimen bars of127mm length,12.7 mm width,and about maximum up to12.7mm thickness.The UL-94V test determines the up-ward-burning characteristics of a solid.Five sam-ple bars suspended vertically over surgical cotton were ignited by a Bunsen burner;two ignitions with10s burning time were applied to each sam-ple bar.The samples of cured epoxy resins with various curing agents of Ph Nov,DDS,and DICY were subjected to the UL-94V test.RESULTS AND DISCUSSIONSynthesis of DOPO Epoxy ResinThe synthesis of the phosphorus-containing epoxy resin(DOPO epoxy resin)was performed by re-acting ODOPB with EPI(Scheme1).The product was characterized by IR.The IR spectrum of DOPO epoxy resin is shown in Figure1.The peak at917cmϪ1absorption indicates the oxirane ring and the peak at1180–1120cmϪ1indicates the P—O—Ph linkage.Other absorption peaks of DOPO epoxy resin are1248cmϪ1(—P A O)and 1400–1500cmϪ1(—P—Ph).The EEW of DOPO epoxy resin was determined by the HClO4/poten-tiometric titration method and found to be229 (theoretical is218).Curing ReactivityThe curing behaviors of the mixtures of DOPO epoxy and various curing agents were studied by DSC.The relative reactivities of various curing agents toward DOPO epoxy resin areaTable I Curing Steps of Epoxy ResinsEpoxy Resin/ Curing AgentPrecureTemperature(°C)PrecureTime(min)CuringTemperature(°C)CuringTime(min)PostcureTemperature(°C)PostcureTime(min)Bis-A/Ph Nov15060175120200180 DOPO/Ph Nov15060175120190180 Bis-A/DDS15060175120200180 DOPO/DDS13560155120175180 Bis-A/DICY15060175120200180 DOPO/DICY13060145120165180PHOSPHORUS-CONTAINING EPOXY RESIN355shown in (Fig.2).For the epoxy resin used,the exothermic starting temperatures increased in the order of DICY ϽDDS ϽPh Nov.A curing agent that exhibits a lower exothermic starting temperature under the same set of curing con-dition is more reactive toward the epoxy resin.Since the reactivity of the hydroxyl group to-ward the oxirane ring is lower than that of the amine group,Ph Nov showed lower reactivity than DDS and DICY.Dynamic Viscoelastic Analyses of DOPO Epoxy Resins with Various Curing AgentsDynamic viscoelastic analysis can give informa-tion on the microstructure of cured epoxy res-ins.The tan ␦curves for the control network exhibit a major relaxation observed in most ep-oxy polymers.25The transition corresponds to the major T g of the cured epoxy resin,above which signiﬁcant chain motion takes place.Fig-ure 3showed the storage modulus G Јand tan ␦of DOPO epoxy and Bis-A epoxy cured with Ph Nov.The results (shown in Table II)indicated that the DOPO epoxy resin cured with Ph Nov,DDS,and DICY had higher T g (181,254,and 198°C)than that of Bis-A epoxy resin cured with Ph Nov,DDS,and DICY (123,212,and 138°C).The result may be attributed totheScheme 1Synthesis of DOPO epoxyresin.Figure 1IR spectrum of DOPO epoxy.356WANG AND SHIEHincorporation of a bulky rigid group that in-creases the rotational barrier.Thermal Properties for Cured Epoxy Resins TGA is the most favored technique for rapid evaluation in comparing and ranking the ther-mal stability of various polymers.Themogravi-metric analyses of both DOPO and Bis-A epoxy resins cured with various curing agents of Ph Nov,DDS,and DICY in nitrogen and air are shown in Table II.The results indicated that DOPO epoxy resin cured with Ph Nov,DDS,Figure 2DSC thermograms of DOPO epoxy resin cured with (A)Ph Nov,(B)DDS,and (C)DICY.Figure 3Dynamic viscoelastic analysis of cured epoxy resins.(A)and (B)Bis-A/Ph Nov;(B)and (D)DOPO/Ph Nov.PHOSPHORUS-CONTAINING EPOXY RESIN 357and DICY have higher char yield than that of cured Bis-A epoxy resin.TGA thermograms of cured Bis-A epoxy/Ph Nov and DOPO epoxy/Ph Nov in a nitrogen atmo-sphere are illustrated in Figure4.Bis-A/Ph Nov exhibited1%weight loss at257°C and then a rapid weight loss at442°C.On the other hand, DOPO epoxy resin showed its1%weight loss at 207°C,and a10%weight loss at around367°C. DOPO epoxy exhibited a lowerﬁrst step rapid weight loss temperature(at376°C)than that of Bis-A epoxy resin(at442°C).However,unlike the one-stage weight loss behavior of the Bis-A ep-oxy/Ph Nov system,the DOPO epoxy/Ph Nov showed a second-stage weight loss at around 521°C.This phenomenon indicates an important role in improving theﬂame retardancy of the resins.While the resin is burning,the phospho-rus-containing groupsﬁrst decompose at around 376°C,and then form a phosphorus-rich residue that prevents further decomposition of the epoxy resin by raising the second decomposition temper-ature to521°C and results in a high char yield. The char yields at700°C for the Bis-A epoxy/Ph Nov system and DOPO epoxy/Ph Nov system were19and48%.TGA thermograms of DOPO and Bis-A epoxy resins cured with various curing agents are shown in Table II.Table II Thermal Properties of Cured Epoxy Resins Epoxy Resin/Curing Agent P%Tg (°C)Temperature of WeightLoss Rapid Weight Loss Temp(Tr,°C)CharYield(%)1%10%Step I Step II Step III700°CAir N2Air N2Air N2Air N2Air N2Air N2Bis-A/Ph Nov0.0123267257413367449442621———219 DOPO/Ph Nov 4.8181183207373363377376544521745—3748 Bis-A/DDS0.0212237277371377424408656———011 DOPO/DDS 4.5254187207347327363363557411753—3240 Bis-A/DICY0.0138243243367357398395443429595—08DOPO/DICY7.2198167159321313212344344491472—2832Figure4TGA thermograms of cured epoxy resins in N2:(A)Bis-A/Ph Nov,(B) DOPO/Ph Nov and derivative,(C)Bis-A/Ph Nov,and(D)DOPO/Ph Nov.358WANG AND SHIEHLOI andUL-94V Test for Cured Epoxy ResinsTheﬂame-retardant properties of cured epoxy resins were examined by measuring the LOI.To demonstrate theﬂame-retardant properties of DOPO epoxy resin,DOPO epoxy,and Bis-A epoxy were cured with(1)Ph Nov,(2)DDS,and(3) DICY for comparison.The LOI values are shown in Table III.Increased char formation can limit the production of combustible carbon-containing gases,decrease the exothermicity due to pyrolysis reactions,as well as decrease the thermal conduc-tivity of the surface of a burning material.24 DOPO epoxy cured with Ph Nov,DDS,and DICY had LOI values of34,32,and36that were higher than those of Bis-A epoxy cured with Ph Nov, DDS,and DICY(LOIϭ26,22,21).The UL-94Vtest determines the upward-burning charac-teristics of a solid.Five sample bars of each cured epoxy resins suspended vertically over surgical cotton were ignited by a Bunsen burner;two ig-nitions of10s each were applied to the sample. The results of UL-94V and LOI test are listed in Table III.DOPO epoxy resin,besides being supe-rior to phosphorus-free epoxy resin inﬂame re-tardancy,also generated much less visible smoke than phosphorus-free epoxy resin.Dynamic Viscoelastic and Thermal Properties of Flame-Retardant Epoxy EncapsulantsOwing to excellent heat,solvent and chemical-resistance,good adhesion and inexpensiveness, epoxy resin has been widely employed in the en-capsulation of microelectronic devices.In this study,DOPO epoxy and TBBA epoxy(tetrabro-mobisphenol A epoxy resin)were compared for theirﬂame retardancy in the encapsulation for-mulation.Bis-A epoxy was blended with various amount of DOPO epoxy and then cured with Ph Nov to give the cured products with phosphorus content of0,0.58,1.03,and1.45%(Bis-A/Ph Nov, DOPO-A,DOPO-B,DOPO-C).In the same man-ner,Bis-A epoxy was blended with TBBA epoxy and then cured with Ph Nov to give the cured products with bromine content of4.01,7.24,and 9.91%(TBBA-A,TBBA-B,TBBA-C).Thermal properties of cured epoxy resins are shown in Table IV.It should be noted that T g of cured epoxy resins increased with the increase in phosphorusTable III UL-94v Test Rating and LOI Values for Cured Epoxy ResinsEpoxy Resin/Curing Agent P%Average BurningTime(s)VisibleSmoke DripUL94-VClassiﬁcation LOIBis-A/Ph Nov0.078Slight No V-226 DOPO/Ph Nov 4.80No No V-034 Bis-A/DDS0.0123Heavy Heavy V-222 DOPO/DDS 4.50No No V-032 Bis-A/DICY0.0158Heavy Slight V-221 DOPO/DICY7.20No No V-036 Table IV Thermal Properties of Cured Epoxy Resin with Various P or Br ContentsSample P%Tg (°C)Temperature of WeightLossRapid Weight Loss Temp(Tr,°C)CharYield(%)1%10%Step I Step II600°C700°CAir N2Air N2Air N2Air N2Air N2Air N2Bis-A/Ph Nov0.0122267257413367449442——2125019 DOPO-A0.58133267277403403424428—6033136731 DOPO-B 1.03135253273393397409419—59933381134 DOPO-C 1.4513824726938338739941454858739432136 Br%TBBA-A 4.01130273247387377403411625—2727023 TBBA-B7.24127277261387357406393641—2930226 TBBA-C9.91124297267367383400388647—3134429PHOSPHORUS-CONTAINING EPOXY RESIN359content while T g decreased with the increase in bromine content .The result may be attributed to the bulky rigid phosphorus-containing group.TGA were also performed to compare the ther-mal stabilities of the cured epoxy resins;the results are also shown in Table IV.DOPO-A (0.58%P)exhibited higher char yield (31%in N 2at 700°C)and higher thermal stability than any TBBA con-taining resins studied.The result indicates that 0.58%P provided a char yield equivalent to that of 9.91%Br.Figure 5shows the thermogravimetric traces of cured resins of Bis-A ,DOPO-C,and TBBA-C in N 2.The Bis-A resin exhibited 1%weight loss at 257°C and 10%weight loss at 367°C,and then a rapid weight loss at around 442°C in N 2.TBBA-C exhibited 1%weight loss at 247°C and 10%weight loss at 267°C,and then a rapid weight loss at around 388°C.On the other hand,the phospho-rus-containing DOPO-C showed 1%weight loss at 269°C and 10%weight loss at 387°C.If the thermal stability of cured epoxy resins were compared by 1%and 10%weight loss,the following order may be given:DOPO-C ϾTBBA-C ϾBis-A.The rapid weight loss temperature (T r )of Bis-A epoxy resin occurred at 442°C,slightly higher than that of DOPO-C;however,it is unlike the one-stage rapid weight loss of the Bis-A epoxy resin.DOPO-C ex-hibited a higher second-stage rapid weight loss at 587°C.This phenomenon played an important role in providing the ﬂame retardancy to the cured ep-oxy resin,and was conﬁrmed by the higher char yields at 600°C (DOPO-C 43%;TBBA-C 34%;Table VUL-94v Test Rating and LOI Value of Cured Epoxy Resins with Various P and Br ContentSample Flame-RetardantElementAverage BurningTime (s)Visible SmokeDrip UL 94-V ClassiﬁcationLOIP%Bis-A/Ph Nov 0.078SlightNo V-226DOPO-A 0.5832Very slight No V-228DOPO-B 1.036No No V-030DOPO-C 1.450No No V-034Br%TBBA-A 4.0138Heavy No V-227TBBA-B 7.244Slight No V-030TBBA-C9.91NoNoV-035Figure 5TGA thermograms of cured epoxy resins in N 2:(A)Bis-A/Ph Nov,(B)TBBA-C,and (C)DOPO-C.360WANG AND SHIEHBis/Ph Nov25%)and700°C(DOPO-C36%;TBBA-C29%;Bis-A19%)for DOPO-C.LOI and UL-94V Test for Flame-RetardantEpoxy ResinCured epoxy resin with high phosphorus content is expected to have a high char residue on pyrol-ysis.The char residue on pyrolysis is reported to be linearly proportional to the oxygen index for halogen-free polymers.27Theﬂame-retardant properties of cured epoxy resins with various phosphorus or bromine contents were examined by measuring their oxygen index(LOI).It is clear from the results of Table V that the higher the phosphorus content the higher the LOI value, which agrees well with previous reports.28,29 For the UL-94test,ﬁve specimens of each cured epoxy resin were prepared and the test results are also shown in Table V.Theﬂame retardancy of cured epoxy resins increases with phosphorus or bromine content in the cured products.Besides phosphorus being much more effective than bro-mine as aﬂame retardant(1.03%P is almost equiv-alent to7.24%bromine by comparing DOPO-B with TBBA-B),it also generates much less visible smoke than the bromine-containing resin. CONCLUSIONThe phosphorus-containing DOPO epoxy resin was successfully synthesized.DOPO epoxy resin cured with Ph Nov,DDS,or DICY yields products with higher T g,thermal stability,and better ﬂame retardancy than those of Bis-A epoxy resin. DOPO epoxy resin may be suitable as a reactive ﬂame retardant by mixing with Bis-A epoxy resin for encapsulation applications.DOPO epoxy resin exhibits betterﬂame retardancy and thermal sta-bility than that of TBBA,but also generated much less visible smoke during combustion.Financial support of this work by the National Science Council of the Republic of China is gratefully appreci-ated(NSC87-2622-E006-027).REFERENCES1.Kinjo,N.;Ogata,M.;Nishi,K.;Kaneda,A.AdvPolym Sci1989,88,1.2.Iijima,T.;Horiba,T.;Tomoi,M.Eur Polym J1991,27(a),851.3.Nakamura,Y.;Yamaguchi,M.;Okubo,M.;Matsu-moto,T.J Appl Polym Sci1992,45,1281.4.Ho,T.H.;Wang,C.S.J Appl Polym Sci1994,54,13.5.Mantecon,A.;Cadiz,V.;Serra,A.;Martinez,P.A.Eur Polym J1987,23,481.6.Cadi,A.S.V.;Martinez,P.A.;Mantecon,A.AngewMakromol Chem1986,140,113.7.Martinez,P.A.;Cadiz,V.;Mantecon,A.;Serra,A.Angew Makromol Chem1985,133,97.8.Chin,W.K.;Hsau,M.D.;Tsai,W.C.J Polym SciPolym Chem Ed1995,33,373.9.Mikroyannidis,J.A.;Kourtides,D.A.J Appl PolymSci1984,29,197.10.Nagata,M.;Tsutsumi,N.;Kiyotsukuri,T.J PolymSci Polym Chem Ed1998,6,235.11.Yang;C.P.;Hsiao,S.H.J Appl Polym Sci1988,36,1221.12.Derouet,D.;Morvan,F.;Bross,J.C.J Appl PolymSci1996,62,1885.13.Maiti,S.;Banerjee,S.;Palit,S.K.Prog Polym Sci1993,18,227.14.Sirrier,H.;Gorgier,S.;Borissov,G.Eur Polym J1990,26,73.15.Liu,Y.L.;Hsiu,G.H.;Chiu,Y.S.;Jeng,R.J.J Appl Polym Sci1996,61,1789.16.Banks,M.;Ebdon,J.R;Johnson,M.Polymer1994,35,3470.17.Banks,M.;Ebdon,J.R.;Johnson,M.Polymer1993,34,4547.18.Annakurtty,K.S.;Kishore,K.Polymer1988,29,756.19.Kishore,K.;Annakurtty,K.S.;Mallick,I.M.Poly-mer1988,29,762.20.Banerjee,S.;Palit,S.K.;Maiti,S.J Polym SciPolym Chem1984,22,1259.21.Mikroyannidis,J.A.;Kourtides,D.A.1984,J ApplPolym Sci29,941.22.Liu,Y.L.;Hsiue,G.H.;Chiu,Y.S.;Jeng,R.J.;Perng,L.H.J Appl Polym Sci1996,61,613. 23.Liu,Y.L.;Hsiu,G.H.;Lee,R.H.;Chiu,Y.S.J ApplPolym Sci1997,63,895.24.Wang,C.S.;Shieh,J.Y.Polymer1998,39,5819.25.Yorkgitis,Jr.,E.M.;Eiss,N.S.;Tran,C.;Willkes,G.L.;McGrath,J.E.Advances in Polymer Science72;Springer-Verlag,NewYork,1985;Vol79.26.Van Krevelen,D.W.Polymer1975,16,615.27.Pearce,E.M.;Liepins,R.Environ Health Perspect1975,11,69.28.Sato,M.;Yokoyama,M.Eur Polym J1975,15,75.29.Liu,Y.L.;Hsiue,G.H.;Chiu,Y.S.;Jeng,R.J.;Ma,C.J Appl Polym Sci1996,59,1619.PHOSPHORUS-CONTAINING EPOXY RESIN361。

纳米孔缺陷导致单层黑磷电荷局域极大抑制非辐射电子-空穴复合的时域模拟

物理化学学报Acta Phys. -Chim. Sin. 2022, 38 (5), 2006064 (1 of 9)Received: June 24, 2020; Revised: July 24, 2020; Accepted: July 25, 2020; Published online: August 4, 2020. *Correspondingauthor.Email:***************.cn;Tel.:+86-10-58806786.The project was supported by the National Natural Science Foundation of China (21973006). 国家自然科学基金(21973006)资助项目© Editorial office of Acta Physico-Chimica Sinica[Article] doi: 10.3866/PKU.WHXB202006064 Charge Localization Induced by Nanopore Defects in Monolayer Black Phosphorus for Suppressing Nonradiative Electron-Hole Recombination through Time-Domain SimulationHaoran Lu 1, Yaqing Wei 1,2, Run Long 1,2,*1 College of Chemistry, Beijing Normal University, Beijing 100875, China.2 Key Laboratory of Theoretical & Computational Photochemistry of Ministry of Education, Beijing Normal University,Beijing 100875, China.Abstract: Black phosphorus (BP) is a promising candidate for photovoltaic and optoelectronic applications owing to its excellent electronic and optical properties. It is believed that defects generally accelerate non-radiative electron-hole recombination in BP and hinder improvement of device performance. Experiments defy this expectation. Using state-of-the-art ab initio time-dependent density functional theory combined with non-adiabatic molecular dynamics, we investigate the non-radiative electron-hole recombination in monolayer(MBP) and MBP containing nanopore defects (MBP-ND). We demonstrate that non-radiative electron-hole recombination is promoted by the P ―P stretching vibrations, and the recombination time of MBP-ND is approximately 5.5 times longer than that of the MBP system. This is mainly attributed to the following three factors: First, the nanopore creates no mid-gap state when increasing the bandgap by 0.22 eV owing to the downshift of the valence band maximum, caused by the decrease in the inter-layer P ―P bond length, thereby weakening the antibonding interaction. Second, the nanopore reduces the overlap of electron and hole wave functions by diminishing the charge densities near the defect. Simultaneously, the nanopore significantly inhibits the thermal-driven atomic fluctuations. The increased bandgap correlated with the decreased wave function overlap and slowed thermal motions of the nuclei in the MBP-ND system reduces the non-adiabatic coupling by a factor of approximately 2 with respect to the pristine system. Third, the slow atomic motions weaken the electron-vibrational interaction and decrease the intensity of the major vibration mode at 440 cm −1, which is the main source for creating non-adiabatic coupling, leading to loss of coherence formed between a pair of electronic states via non-adiabatic coupling and causing electron-hole recombination that results in a 1.5-fold increase in the coherence time in the MBP-ND system with respect to the MBP system. Consequently, the increased bandgap and decreased non-adiabatic coupling compete successfully with the prolonged coherence time, extending the excited-state lifetime to 2.74 ns in the system containing nanopore defects, which is only 480 ps in the pristine system. These phenomena arise owing to a complex interplay of the unusual chemical, structural, electrostatic, and quantum properties of BP with and without nanopore defects. This study is of great significance for understanding the excited-state properties of BP . The detailed mechanistic understanding of the prolonged charge carriers lifetime of MBP decorated with nanopore defects provides key insights for defect engineering in BP and other 2-dimensional materials for a broad range of solar and electro-optic applications by reducing the non-radiative charge and energy losses.Key Words: Monolayer black phosphorus; Nanopore defect; Non-radiative electron-hole recombination;Time-dependent density functional theory; Non-adiabatic molecular dynamics纳米孔缺陷导致单层黑磷电荷局域极大抑制非辐射电子-空穴复合的时域模拟卢浩然1，魏雅清1,2，龙闰1,2,*1北京师范大学化学学院，北京 1008752北京师范大学教育部理论与计算光化学重点实验室，北京 100875摘要：通常认为缺陷加速黑磷的非辐射电子-空穴复合，阻碍器件性能的持续提高。