Nanosize Magnetic Films and Powders Prepared by Extraction-Pyrolysis Technique

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微米镍粉在太赫兹波段的Mie散射特性研究

烟雾的能力，以实现全天候工作。太赫兹通信可
作者简介：罗
轶（９６一）男，１８，在读硕士，主要从事基于太赫兹
的非均质材料和太赫兹屏蔽材料的研究。Ｅｍａ：ｏ６＠ｇｉｃｍ・ｉｌｙ７ｍａ．ｏｌｕｌ
收稿日期：００１ —８修订日期：００１－３２１．０１；２１－２２
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关键成分］但将其作为太赫兹屏蔽材料的研究却，鲜有报道。研究材料的散射和吸收特性可以了解材料在应用中的物理机制，为其作为屏蔽材料的应能用提供一定的理论指导Ｊ。
２理论基础
料的研究已有报它
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金属镍具有良好的导电性和铁磁性、化学腐抗蚀性和吸波能力强等优点，电磁屏蔽方面有很好在的应用前景］已成为欧美等国电磁屏蔽材料的，
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物理学英文词汇

物理专业英语词汇(M)Favorite m center m 中心mach angle 马赫角mach cone 马赫锥mach number 马赫数mach wave 马赫波mach zehnder interferometer 马赫曾德耳干涉仪mach's principle 马赫原理machine language 机骑言machine oriented language 面向机颇语言macleod gage 麦克劳计macro crystal 粗晶macrography 宏观照相术macroinstability 宏观不稳定性macromolecule 高分子macron 宏观粒子macroparticle 宏观粒子macrophysics 宏观物理学macroscopic brownian motion 宏观布朗运动macroscopic particle 宏观粒子macroscopic quantization 宏观量子化macroscopic system 宏观系统macrostate 宏观态macrostructure 宏观结构macrosystem 宏观系统magdeburg hemispheres 马德堡球magellanic clouds 麦哲伦星系magellanic galaxy 麦哲伦星系magic eye 光党指示管magic lantern 幻灯magic number 幻数magic t t 形波导支路magma 岩浆magneli structure 马格涅利结构magnesium 镁magnet 磁铁magnetic 磁的magnetic amplifier 磁放大器magnetic analyzer 磁分析器magnetic anisotropy 磁蛤异性magnetic anomaly 磁异常magnetic axis 磁轴magnetic balance 磁力天平magnetic birefringence 磁双折射magnetic breakdown 磁哗magnetic bubble 磁泡magnetic bubble storage 磁泡存储器magnetic character figure 磁特正magnetic charge 磁荷magnetic chart 磁图magnetic circuit 磁路magnetic conductance 磁导magnetic core storage 磁芯存储器magnetic current 磁流magnetic declination 磁偏角magnetic deflection 磁偏转magnetic deflection mass spectrometer 磁偏转型质谱仪magnetic dip 磁倾角magnetic dipole 磁偶极子magnetic dipole moment 磁偶极矩magnetic dipole radiation 磁偶极辐射magnetic disk 磁盘magnetic disturbances 磁扰magnetic domain 磁畴magnetic domain walls 磁畴壁magnetic drum 磁鼓magnetic elements 磁元magnetic energy 磁能magnetic entropy 磁熵magnetic equator 磁赤道magnetic field 磁场magnetic field energy 磁场能量magnetic field intensity 磁场强度magnetic field strength 磁场强度magnetic fluid 磁铃magnetic flux 磁通量magnetic flux compression 磁通量紧缩magnetic flux density 磁通密度magnetic flux quantization 磁通量量子化magnetic fluxmeter 磁通量计magnetic focusing 磁致聚焦magnetic force 磁力magnetic head 磁头magnetic hysteresis 磁滞magnetic image 磁象magnetic inclination 磁倾角magnetic induction 磁感应magnetic induction flux 磁感应束magnetic kerr effect 克尔氏磁效应magnetic latitude 磁纬度magnetic leakage 磁漏magnetic lens 磁透镜magnetic line of force 磁力线magnetic loss 磁损耗magnetic map 磁图magnetic material 磁性材料magnetic memory 磁存储器magnetic mirror 磁镜magnetic moment 磁矩magnetic monopole 磁单极子magnetic needle 磁针magnetic north 磁北magnetic permeability 磁导率magnetic perturbation 磁扰magnetic point group 磁点群magnetic polarization 磁极化magnetic polaron 磁极化子magnetic pole 磁极magnetic potential 磁势magnetic pressure 磁压magnetic prism 磁棱镜magnetic probe 磁探针magnetic prospecting 磁法勘探magnetic quantum number 磁量子数magnetic recorder 磁记录器magnetic recording 磁记录magnetic refrigeration 磁冷却magnetic refrigerator 磁致冷机magnetic relaxation 磁弛豫magnetic reluctance 磁阻magnetic remanence 顽磁magnetic resistance 磁阻magnetic resonance 磁共振magnetic reynolds number 磁雷诺数magnetic rigidity 磁刚性magnetic rotatory dispersion 磁致旋光色散magnetic saturation 磁饱和magnetic semiconductor 磁性半导体magnetic separation 磁力选矿magnetic shell 磁壳magnetic shield 磁屏蔽magnetic sound recording 磁录音magnetic space group 磁空间群magnetic spectrometer 磁谱仪magnetic spin quantum number 自旋磁量子数magnetic star 磁星magnetic store 磁存储器magnetic storm 磁暴magnetic structure 磁结构magnetic substance 磁体magnetic superconductor 磁超导体magnetic surface 磁面magnetic susceptibility 磁化率magnetic tape 磁带magnetic thermometer 磁温度计magnetic thin film 磁薄膜magnetic torque 磁转矩magnetic transition 磁跃迁magnetic trap 磁阱magnetic variable 磁变星magnetic variable star 磁变星magnetic variations 磁变magnetic viscosity 磁粘滞性magnetics 磁学magnetism 磁magnetization 磁化magnetization curve 磁化曲线magnetization vector 磁化矢量magnetized black hole 磁化黑洞magnetizing 磁化magnetizing coil 磁化线圈magnetizing current 磁化电流magnetizing force 磁化力magneto aerodynamics 磁空气动力学magneto optic effect 磁光效应magneto oscillatory absorption 磁振荡吸收magneto rotation 磁致旋光magneto volume effect 磁体积效应magnetoacoustic effect 磁声效应magnetoacoustic wave 磁声波magnetocaloric effect 磁热效应magnetochemistry 磁化学magnetocircular dichroism 磁圆二向色性magnetodielectric 磁性电介质magnetodiode 磁敏二极管magnetoelastic effect 磁弹性效应magnetoelastic wave 磁弹性波magnetoelectricity 磁电学magnetogram 磁强记录图magnetograph 磁强记录仪magnetohydrodynamic instability 磁铃力学不稳定性magnetohydrodynamic wave 磁铃波magnetohydrodynamics 磁铃动力学magnetology 磁学magnetomechanical factor 磁力学因数magnetomechanics 磁力学magnetometer 磁强计magnetomotive force 磁通势magneton 磁子magnetooptics 磁光学magnetophotophoresis 磁光致泳动magnetoplasma 磁等离子体magnetoplasmadynamics 磁等离子体动力学magnetoplumbite 氧化铅铁淦氧磁体magnetopolaron 磁极化子magnetoreflection 磁反射magnetoresistance 磁阻效应magnetoresistor 磁致电阻器magnetosphere 磁层magnetostatic field 静磁场magnetostatics 静磁学magnetostriction 磁致伸缩magnetostriction oscillator 磁致伸缩振荡器magnetostrictive effect 磁致伸缩效应magnetothermal effect 磁致热效应magnetothermoelectric effect 磁致热电效应magnetron 磁控管magnetron vacuum gage 磁控管真空计magnification 放大率magnifier 放大镜magnifying glass 放大镜magnitude 量magnitude of the eclipse 食分magnon 磁振子magnus effect 马格努斯效应main quantum number 挚子数main sequence 烛main sequence stars 烛星main storage 宙储器major planets 大行星majorana force 马约喇纳力majorana neutrino 马约喇纳中微子majorana particle 马约喇纳粒子majorana spinor 马约喇纳旋量majority carrier 多数载劣majoron 马约喇纳量子maksutov telescope 马克苏托夫望远镜malleability 展性malter effect 马尔特效应malus law 马吕斯定律man made satellite 人造卫星mandelstam representation 曼德尔斯坦表象mandrin 细探针manganese 锰manganin 锰镍铜合金manifold 廖manipulator 机械手manometer 压力表manoscope 气体密度计manoscopy 气体密度测定manostat 稳压器mantle 地幔mantle convection 地幔对流mantle rayleigh wave 地幔瑞利波manual 手册many body force 多体力many body problem 多体问题many body system 多体系many wave approximation 多波近似mare 海margin 余量margin of error 误差范围margin of safety 安全因子marginal rays 边缘光线marine physics 海洋物理学mariner project 马里纳计划marisat system 海洋卫星系统mark 标记markoff chain 马尔柯夫链markoff process 马尔柯夫过程marriage of cable and satellites 电缆和人造卫星的联接mars 火星martensite 马氏体maser 微波激射器脉塞mass 质量mass absorption coefficient 质量吸收系数mass analysis 质量分析mass analyzer 质谱仪mass defect 质量筐mass effect 聚集效应mass energy conversion formula 质能换算公式mass energy equivalence principle 质能相当性原理mass energy relation 质能关系mass filter 滤质器mass flowmeter 质量量计mass formula 质量公式mass luminosity relation 质量发光度关系mass number 质量数mass renormalization 质量重正化mass separator 质量分离器mass shell 质壳mass spectrograph 质谱仪mass spectrometer 质谱仪mass spectroscopy 质谱法mass spectrum 质谱mass stopping power 质量阻止本领mass transfer 质量传递mass unit 质量单位massey criterion 梅涡据master equation 纸程master gyroscope 自由陀螺仪matching 匹配material 物质material point 质点material wave 物质波materials science 材料科学materials testing reactor 材料试验反应堆mathematical crystallography 数学晶体学mathematical expectation 数学期望值mathematical pendulum 单摆mathematical physics 数学物理mathematical programming 数学规划mathieu functions 马提厄函数matrix mechanics 矩阵力学matrix representation 矩阵表示matter 物质matter dominated universe 物质为诸宙matter wave 德布罗意波matthias rule 马赛厄斯定则matthiessen rule 马苇定则maupertuis' principle 莫佩尔秋原理maximum deviation 最大偏差maximum load 最大负载maximum lyapunov index 最大李亚普诺夫指数maximum permissible concentration 最大容许浓度maximum permissible dose 最大容许剂量maximum postulated accident 最大假设事故maximum speed 最大速度maximum stress 最大应力maximum temperature 最高温度maximum thermometer 最高温度表maximum velocity 最大速度maxwell 麦克斯韦maxwell boltzmann distribution 麦克斯韦玻耳兹曼分布maxwell boltzmann statistics 麦克斯韦玻耳兹曼统计maxwell bridge 麦克斯韦电桥maxwell demon 麦克斯韦妖maxwell field 麦克斯韦场maxwell relations 麦克斯韦关系maxwell velocity distribution 麦克斯韦的速度分布maxwell's distribution law 麦克斯韦分布律maxwell's equations 麦克斯韦方程maxwellian distribution 麦克斯韦分布maxwellmeter 磁通计mb 微巴mean acceleration 平均加速度mean deviation 平均偏差mean ergodic theorem 平均脯历经定理mean error 平均误差mean free path 平均自由程mean life 平均寿命mean lifetime 平均寿命mean solar day 平太阳日mean solar time 平太阳时mean square error 均方误差mean sun 平太阳mean value 平均值mean velocity 平均速度mean velosity 平场速度measure 测度measurement 测量measurement error 测量误差measuring 测量measuring apparatus 测量仪器measuring eyepiece 目镜测微计measuring instrument 测试仪器度量仪表measuring method 测量法measuring technique 测量技术mechanical energy 力学能mechanical equivalent of heat 热功当量mechanical filter 机械滤波器mechanical monochromator 机械单色器mechanical motion 力学运动mechanical system 力学系mechanical vibrations 机械振动mechanical world view of nature 机械的自然观mechanics 力学mechanism 机构mechanocaloric effect 机械热效应mechanochemistry 机械化学mechanoelectric conversion 机电变换mechanostriction 机致伸缩mechnical equivalent of light 光功当量medical electronics 医疗电子学medical physics 医用物理学medium 介质medium energy electron diffraction 中能电子衍射medium energy electron scattering spectroscopy 中能电子散射能谱学mega 兆mega electron volt 兆电子伏megacycle 兆周megawatt 兆瓦megger 高阻表megohm 兆欧meissner effect 迈斯纳效应meldometer 熔点测定计melt growth 熔体生长melting 熔化melting heat 熔化热melting point 熔点melting temperature 熔解温度membrane 膜memory 存储;记忆memory capacity 存储容量memory cell 存储单元memory effect 记忆效应memory register 存储寄存器mendeleev's periodic law 门捷列夫周期律mendelevium 钔meniscus 弯月面meniscus lens 弯月透镜mensa 山案座mercury 水星;水银mercury arc lamp 水银灯mercury arc rectifier 汞弧整流mercury barometer 水银气压表mercury cell 汞电池mercury diffusion pump 汞扩散泵mercury i chloride structure 氯化汞i型结构mercury relay 水银继电器mercury telemetry 水星遥测术mercury thermometer 水银温度表mercury vacuum gage 水银真空计mercury vapor lamp 水银灯meridian 子午线meridian passage 中天meridian transit 中天meridional ray 子午光线mesa transistor 台面型晶体管mesoatom 介子原子mesodynamics 介子动力学mesomolecule 介子分子mesomorphic state 介晶态meson 介子meson factory 介子工厂meson theory 介子理论meson theory of nuclear forces 核力的介子理论mesonic atom 介子原子mesonic molecule 介子分子mesopic vision 黄昏黎糜觉mesoscopic effect 介观效应mesosphere 中间层messier catalog 梅味星云星团表metacenter 定倾中心metal 金属metal film resistor 金属薄膜电阻器metal foil 金属箔metal insulator semiconductor light emitting diod 金属绝缘膜半导体发光二极管metal insulator transition 金属绝缘体跃迁metal nonmetal transition 金属非金属跃迁metal organic compound 有机金属化合物metal oxide semiconductor structure mos 结构metal vapor laser 金属蒸汽激光器metallic 金属的metallic binding 金属键metallic bond 金属键metallic crystal 金属晶体metallic element 金属元素metallic glass 金属玻璃metallic lustre 金属光泽metallic microcluster 金属微簇metallic reflection 金属反射metallic thin film 金属薄膜metallic valence 金属原子价metallized paper capacitor 镀金属纸介电容器metallography 金相学metallomicroscope 金相显微镜metallurgy 冶金学metamagnetism 亚磁性metastability 亚稳定性metastable atom 亚稳原子metastable equilibrium 亚稳平衡metastable level 亚稳能级metastable molecule 亚稳分子metastable nucleus 亚稳核metastable phase 亚稳相metastable state 亚稳状态meteor 燎meteor astronomy 燎天文学meteor camera 燎照相机meteor shower 燎雨meteor stream 燎群meteoric dust 燎尘meteoric iron 陨铁meteoric stone 石陨星meteorite 陨星meteorite crater 陨星坑meteoritic iron 陨铁meteoritics 陨石学meteorological acoustics 气象声学meteorological optics 气象光学meteorological radar 气象雷达meteorological satellite 气象卫星meteorological thermodynamics 气象热力学meteorology 气象学meter 米meter convention 米条约meter standard 米原器meter wave 米波metering 计量metglass 金属玻璃method 方法method of approximation 近似法method of crystal projection 晶体投影法method of difference 差分法method of images 镜象法method of iteration 迭代法method of least squares 最小二乘法method of measurement 测量法method of molecular orbitals 分子轨迹法method of perturbation 微扰法method of steepest descent 最陡下降法method of successive approximation 逐次逼近法method of undetermined coefficients 待定系数法metonic cycle 太阴周metre 米metre wave 米波metric 度规metric space 度量空间metric system 米制metric tensor 度规张量metrology 计量学metronome 节拍器mhd arc mpd 弧光mho 闻子mica 云母micelle 胶体微粒michel parameter 米歇尔参数michelson interferometer 迈克耳逊干涉仪michelson morley experiment 迈克耳逊莫雷实验michelson stellar interferometer 迈克耳逊恒星干涉计micro 微microaccelerometer 微加速计microaerotonometer 微量气体张力计microampere 微安microanalysis 微量化字分析microbalance 微量天平microbar 微巴microcanonical ensemble 微正则系综microchemical analysis 微量化字分析microchemistry 微量化学microcomputer 微型计算机microcrystal 微晶microcrystalline 微晶的microcrystallography 微观结晶学microengineering 微工程学microfarad 微法microfield 微场microfilm 缩微胶片micrography 显微照相术microinstability 微不稳定性microlaser 微型激光器microlock 卫星遥测系统micromagnetics 微磁学micromanometer 微压力计micrometer 测微计micrometer microscope 测微显微镜micrometron 自动显微镜micromicrocurie 微微居里micromicrofarad 微微法micron 微米microoscillograph 显微示波仪microparticle 微观粒子microphone 传声器microphotograph 显微镜照片microphotometer 测微光度计microphysics 微观物理学microplasma 微等粒子体microprobe 微探针microprogram 微程序microprojector 显微投影仪micropyrometry 微测高温术microscope 显微镜microscopic brownian motion 微观布朗运动microscopic particle 微观粒子microscopic state 微观状态microscopic system 微观系统microscopium 显微镜座microsecond 微秒microseismics 微地震学microseismograph 微震记录仪microspectrofluorimeter 显微荧光光谱仪microspectrograph 显微光谱仪microspectrophotometry 显微分光光度学microspectroscope 显微分光镜microspectroscopy 显微光谱学microstate 微观状态microstructure 显微结构microsystem 微观系统microtelescope 显微望远镜microthermometer 微温度计microthermometry 显微温度学microtron 电子回旋加速器microwave 微波microwave circuit 微波电路microwave diode 微波二极管microwave method 微波法microwave resonator 微波谐振器microwave spectroscopy 微波谱学microwave spectrum 微波频谱microwave transistor 微波晶体管microwave tube 微波电子管microwave ultrasound 微波超声microwave weapon 微波武器mie scattering 米散射migdal approximation 米格达尔近似migration length 迁移长度mil 密耳mile 英里milky way 银河miller index 密勒指数miller's notation 密勒记号milli 毫milliampere 毫安millibar 毫巴millimeter 毫米millimeter wave 毫米波millimetre 毫米million electorn volt 兆电子伏millisecond 毫秒millivolt 毫伏millivoltmeter 毫状计mimosa seismic foreteller 含羞草地震预报器miniature tube 微型管miniature valve 微型管minicomputer 小型计算机miniinfraredtracer 微型红外示踪器minilaser 微型激光器minimal interaction 最小耦合相互酌minimax principle 极大极小原理minimum b field 最小磁场minimum deviation 最小偏向minimum entropy production 最小熵产生minimum thermometer 最低温度表minkowski space time 闵科夫斯基时空minor planet 小行星minority carrier 少数载劣minus 减minus sign 减号minute 分mira stars 刍藁变星mira type variables 刍藁变星mirage 蜃景mirror field 磁镜场mirror nuclei 镜象核mirror reflection 镜反射mirror surface 镜面mirror telescope 反射望远镜misfit dislocation 错配位错missile 导弹missing line 丢失线missing mass 暗物质mistake 错误mixed crystal 混合晶体mixed state 混合态mixer diode 基模mixer tube 混频管mixing length 混合长度mixing ratio 混合比mixture 混合物mks system of units mks 单位制;mks单位制mksa system of units mksa 单位制mobile laser tracking station 移动激光追踪站mobility 迁移率mobility of ions 离子迁移率mode 模mode coupling 模耦合mode locked laser 锁模激光器mode locking 锁模mode of oscillation 振动型mode of vibration 振动型mode pulling 波模牵引model 模型model of nucleus 核模型model of the galaxy 银河系模型moderated neutron 慢化中子moderation 减速moderation of neutrons 中子减速moderator 减速剂modern biology 现代生物学modern physics 现代物理学modification 变形modular invariance 模数不变性modulated structure 灯结构modulation 灯modulation method 灯法modulation spectroscopy 灯光谱学modulation transfer function 灯传递函数modulator type vacuum gage 灯仆真空计module 模件modulus 模数modulus of elasticity 弹性模数modulus of rigidity 剪切殚性模量moffatt's vortex 莫法特涡旋mohoroviris discontinuity 莫霍洛维奇不连续性mohs hardness 莫氏硬度moist labile energy 潮湿不稳能moisture examining instrument 水气检查仪mol 克分子molar fraction 克分子分率molar heat 分子热molar polarization 克分子极化molar refraction 分子折射molar susceptibility 克分子磁化率molar volume 克分子体积molding 制模mole 克分子mole fraction 克分子分率molectronics 分子电子学molecular absorption coefficient 分子吸收系数molecular acoustics 分子声学molecular astronomy 分子天文学molecular beam 分子束molecular beam epitaxy 分子束外延molecular beam magnetic resonance 分子束磁共振molecular beam maser 分子束微波激射器molecular beam scattering 分子束散射molecular beam spectroscopy 分子束光谱学molecular biology 分子生物学molecular bond 分子键molecular chaos 分子混沌态molecular clock 分子钟molecular cloud 分子云molecular compound 分子化合物molecular conductivity 分子导电率molecular crystal 分子晶体molecular diffusion 分子扩散molecular dynamics 分子动力学molecular electronics 分子电子学molecular field 分子场molecular field approximation 分子场近似molecular flow 分子流molecular force 分子力molecular force field 分子力场molecular gas laser 分子气体激光器molecular heat 分子热molecular image 分子图象molecular integral 分子积分molecular inversion 分子倒转molecular ion 分子离子molecular kinetic theory 分子运动论molecular lattice 分子晶格molecular magnet 分子磁铁molecular mass 分子质量molecular motion 分子运动molecular orbital 分子轨函数molecular physics 分子物理学molecular polarizability 分子极化度molecular polarization 分子极化molecular pump 分子泵molecular radius 分子半径molecular rays 分子束molecular reaction 分子反应molecular refraction 分子折射molecular rotation 分子转动molecular scattering 分子散射molecular science 分子科学molecular sieve 分子筛molecular structure 分子结构molecular structure theory 分子结构论molecular viscosity 分子粘性molecular volume 克分子体积molecular weight 分子量molecule 分子moletron 分子加速器molten high polymer 熔融高聚物molybdenum 钼moment 矩moment of couple 力偶矩moment of force 力矩moment of impulse 冲量矩moment of inertia 转动惯量moment of momentum 角动量momentum 动量momentum space 动量空间momentum transfer 动量转移momentum transfer cross section 动量转移截面momentum transfer theory 动量转移理论monaural audition 单耳听力monitor 监测器监视器monoatomic gas 单原子气体monoatomic layer 单原子层monoceros 座monochord 弦音计monochromat 单色透镜monochromatic aberration 单色象差monochromatic light 单色光monochromatic radiation 单色辐射monochromatic rays 单色射线monochromaticity 单色性monochromatization of neutron 中子的单色化monochromatization of x rays x 射线单色化monochromator 单色器单色光镜monoclinic system 单斜晶系monocrystal 单晶monocular 单筒望远镜monodispersive system 单分散系monolithic circuit 单片电路monomer 单体monomode laser 单模激光器monomolecular film 单分子膜monopole 单极monopole moment 单极子矩monopole transition 单极跃迁monostable multivibrator 单稳多谐振荡器monotectic 偏晶体monte carlo method 蒙特卡罗法month 月moon 月球moon power station 月球发电站moon's age 月龄morning star 晨星morphophysics 形态物理学morse potential curve 莫尔斯势能曲线mos diode mos 二极管mos field effect transistor mos 金属氧化物半导体场效应晶体管mos integrated circuit mos 集成电路mos structure mos 结构mosaic crystal 嵌镶晶体mosaic structure 嵌镶结构moseley's law 莫塞莱定律mosfet mos 金属氧化物半导体场效应晶体管motion 运动motion equation 运动方程motor 电动机mott insulator 莫脱绝缘体mott scattering 莫脱散射mott transition 莫脱跃迁mottelson valatin effect 莫特尔逊瓦拉廷效应movement of the pole 极运动movement stability 运动的稳定性moving cluster 移动星团moving coil galvanometer 动圈检疗moving iron vane instrument 动叶式仪表moving magnet galvanometer 动磁型电疗moving magnet instrument 动磁式仪表moving medium acoustics 运动介质声学moving striation 活动条纹mpd arc mpd 弧光mtller scattering 摩利尔散射mts system of units mts单位制mu factor 放大系数multi color photometry 多色测光multi crystal x ray spectrometer 多晶x 射线光谱仪multi function observer 多功能观测器multichannel interferometric spectrometer 多道干涉光谱仪multichannel pulse height analyzer 多道脉冲高度分析器multienzymatic reaction 多酶反应multifilament composite wire 多丝结构复合线multigroup model 多群模型multilayer film 多层胶片multilayer mirror 多层反射镜multimode laser 多模激光器multimolecular layer 多分子层multiparticle correlation 多粒子关联multiparticle production 多粒子产生multiphase flow 多相流multiphoton absorption 多光子吸收multiphoton dissociation 多光子离解multiphoton process 多光子过程multiphoton transition 多光子跃迁multiple beam interference 多光束干涉multiple beam interferometry 多光束干涉测量法multiple collision 多次碰撞multiple correlation 多重相关multiple coulomb scattering 多次库仑散射multiple electrode tube 多栅管multiple electrode valve 多栅管multiple excitation 多次激发multiple galaxy 多重星系multiple ionization 多次电离multiple mirror telescope 多镜望远镜multiple periodic motion 多周期运动multiple process 多重过程multiple production 多重产生multiple reflection 多次反射multiple refraction 多次折射multiple scattering 多次散射multiple star 聚星multiple structure 多重结构multiplet 多重线multiplet term 多重项multiplication 增殖multiplication factor 倍增系数multiplicity 多重性multiplier 倍增器multiply connected region 多连通域multiply periodic motion 多重周期运动multiply twinned particle 多重孪晶粒子multiplying factor 倍率multipole 多极multipole expansion 多极展开multipole moment 多极矩multipole radiation 多极辐射multipurpose minicamera 多功能缩微照相机multipurpose reactor 多用堆multislit spectrometry 多狭缝能谱测定法multispectral photography 多谱照像术multispectral satellite data 多谱卫星数据multitarget tracking 多目标跟踪multivariate analysis 多变量分析multivibrator 多谐振荡器multiwire chamber 多丝室multiwire counter 多丝计数管mumeson 介子muon 介子muon beam 子束muon capture 子俘获muon catalyzed fusion 子催化聚变muon neutrino 子中微子muon number 子数muon spin rotation 子自旋转动muonic atom 原子muonic catalysis 子催化muonium 子偶素murchison meteorite 默基森陨星musca 苍蝇座musical acoustics 音乐声学musical scale 音阶musical sound 乐音muspace 空间mutarotation 变旋mutation 突变mutual conductance 互导mutual inductance 互感mutual induction 互感应mutual neutralization 互中性化myopia 近视myria 万myriad 一万myriads 无数myriameter 万米myriametric wave 超长波。

纳米磁性粉体材料及其磁流体的制备

中文摘要本文是围绕着磁流体的制备来进行研究的，并根据磁流体的组成将其制备流程分为以下三大环节：纳米级磁性粉体颗粒（粒径在１０ｒｉｍ左右）的制备；磁性粉体颗粒的表面处理；磁流体的制备。

首先，是小粒径的磁性粉体颗粒的制备。

根据大量试验探索，本文找到制备小粒径（～１０ｒｉｍ）磁性粉体材料的较好方法——低温相转化法。

并通过对反应中升温顺序的控制，发现用先升温法在制备１０ｒｉｍ左右的小粒径磁性颗粒材料方面较具有优越性，并用这种方法相继制得了一系列纳米尖晶石型磁性粉体材料。

另外还通过在制各样品的过程中掺杂ｚｎ：＋，使Ｚｎ２＋进入所制备的尖晶石型样品的四面体间隙内，并通过尖晶石结构中离子间的超交换作用，可以使所制样品的磁性能得到很大的提高，从而优选出可以用来制备磁流体的纳米磁性粉体样品。

其次，是用油酸对适合用来制备磁流体的磁性粉体颗粒进行表面处理，以降低粒子的表面能，从而可防止因两个磁性粒子互相接近而引起颗粒在载液中聚凝和沉降。

并用紫外光谱仪对磁性粉体颗粒表面改性效果进行定量评估，探讨了ｐＨ值、温度、时间以及复合表面活性剂对颗粒表面包覆效果的影响，从而确定了磁性粉体颗粒表面改性效果的最佳条件。

最后，是把表面改性效果最佳的磁性粉体颗粒通过过渡液均匀分散于载液中而制得磁流体。

试验中采用ＤＯＰ作载液，这是因为ＤＯＰ的凝固点为．５０℃，沸点为３８４℃，用其作载液不仅能耐一定的低温，而且也能耐高温，具有很宽的温度适用范围。

文中探讨了过渡液、温度对制备磁流体稳定性的影响以及固液比与粘度的关系。

试验表明，在制各磁流体时，温度不宜太高，否则会影响制各的磁流体的稳定性；并且磁流体的粘度随其所包含磁性颗粒量的增加而增大。

本文对磁流体制备过程中的各个环节进行了较为详尽的研究，并进行了相应的表征、分析，取得了一些极为有价值的数据，尤其是在纳米磁性粉体颗粒的制备及其表面处理效果的评估方面作了很有意义的探索。

关键词：尖晶石超顺磁性纳米粒子低温相转化法包覆磁性液体ＡｂｓｔｒａｃｔＩＩｌｔｈｉｓａｒｔｉｃｌｅ，ｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆｍａｇｎｅｔｉｃｆｌｕｉｄｓｗａｓｔｈｅｃｅｎｔｅｒｏｆｉｎｖｅｓｔｉｇａｔｉｏｎ．Ａｃｃｏｒｄｉｎｇｔｏｔｈｅｍａｋｅｕｐｏｆｔｈｅｍａｇｎｅｔｉｃｆｌｕｉｄｓ，ｆｏｒｗｈｉｃｈｔｈｅｐｒｏｃｅｓｓｏｆｐｒｅｐａｒａｔｉｏｎｖｃａｓｄｏｎｅａｓｆｏｌｌｏｗ，ｆｉｒｓｔ，ｔｈｅｆａｂｒｉｃａｔｉｏｎｏｆｍａｇｎｅｔｉｃｐｏｗｄｅｒｓｗｉｔｈｎａｎｏｓｉｚｅａｂｏｕｔ１０ｎｍ；ｓｅｃｏｎｄ，ｔｈｅｄｉｓｐｏｓａｌｆｏｒｔｈｅｓｕｒｆａｃｅｏｆｍａｇｎｅｔｉｃｐｏｗｄｅｒｓ；ｆｉｎａｌｌｙ，ｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆｍａｇｎｅｔｉｃｆｌｕｉｄｓ．ｗｉｔｈｓｍａｌｌｎａｎｏｓｉｚｅｗｅｒｅｆａｂｒｉｃａｔｅｄ．ＡｃｃｏｒｄｉｎｇｔｏＦｉｒｓｔｌｙ，ｍａｇｎｅｔｉｃｐｏｗｄｅｒｓａｂｕｎｄａｎｔｒｅｓｅａｒｃｈｉｎｅｘｐｅｒｉｍｅｎｔ，ａｂｅｔｔｅｒｍｅｔｈｏｄ，ｐｈａｓｅｔｒａｎｓｆｏｒｍａｔｉｏｎａｔｌｏｗｔｅｍｐｅｒａｔｕｒｅ．Ｗａｓｆｏｕｎｄｕｓｉｎｇｆｏｒｔｈｅｓｙｎｔｈｅｓｉｓｏｆｍａｇｎｅｔｉｃｐｏｗｄｅｒｓ、ｖｉｔｌｌｓｍａｌｌｎａｎｏｓｉｚｅａｂｏｕｔｌＯｎｍ．Ｂｙｍｅａｎｓｏｆｔｈｅｃｏｎｔｒｏｌｆｏｒｔｈｅｏｒｄｅｒｏｆｔｅｍｐｅｒａｔｕｒｅ－ｒａｉｓｉｎｇｉｎｔｈｅｐｒｏｃｅｓｓｏｆｓｙｎｔｈｅｓｉｓ，ｐｒｅ－ｔｅｍｐｅｒａｔｕｒｅ·ｒａｉｓｉｎｇｍｅｔｈｏｄｗａｓｏｆｍｏｒｅｓｕｐｅｒｉｏｒｉｔｙｉｎｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆｍａｇｎｅｔｉｃｐｏｗｄｅｒｓｗｉｔｈｓｍａｌｌｎａｎｏｓｉｚｅａｂｏｕｔｌＯｎｍ．Ａｎｄａｓｅｒｉｅｓｏｆｍａｇｎｅｔｉｃｐｏｗｄｅｒｓｗｉｔｈｎａｎｏｃｒｙｓｔａｌｌｉｎｅ￥ｔｎｌｅｔｕｒｅｗａｓｓｙｎｔｈｅｓｉｚｅｄ．Ｉｎａｄｄｉｔｉｏｎ，ｉｎｔｈｅｐｒｏｃｅｓｓｏｆｔｈｅｓａｍｐｌｅｓｆａｂｒｉｃａｔｅｄ，ａｌｉｔｔｌｅｏｆｍａｔｔｅｒｗｉｔｈＺｎ２＋ｉｏｎｖｃａｓａｄｄｅｄｉｎｏｒｄｅｒｔｏｍａｋｅＺｎ２＋ｉｏｎｓｅｎｔｅｒｔｈｅｉｎｔｅｒｓｐａｃｅｏｆｔｅｔｒａｈｅｄｒｏｎｆｏｒｔｈｅｓａｍｐｌｅｓ、Ⅳｉｔｌｌｓｐｉｎｅｌｓｔｒｕｃｔｕｒｅ．Ｔｈｒｏｕｇｈｔｈｅｓｕｐｅｒ－ｅｘｃｈａｎｇｅｒｅｃｉｐｒｏｃｉｔｙａｍｏｎｇｔｈｅｄｉｆｆｅｒｅｎｔｉｏｎｓｉｎｔｈｅｓｐｉｎｅｌ，ｔｈｅｍａｇｎｅｔｉｚａｔｉｏｎｏｆｔｈｅｓａｍｐｌｅｓｐｒｅｐａｒｅｄｃｏｕｌｄｂｅｒａｉｓｅｄｉｎｌａｒｇｅｄｅｇｒｅｅ．Ｓｏｓａｍｐｌｅｓｏｆｍａｇｎｅｔｉｃｐｏｗｄｅｒｓ稍ｔｌｌｎａｎｏｓｉｚｅａｂｏｕｔｌＯａｍｗｅｒｅｃｈｏｓｅｎｓｕｉｔａｂｌｅｆｏｒｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆｍａｇｎｅｆｉｃｆｌｕｉｄ．ｍａｇｎｅｔｉｃｐｏｗｄｅｒｓ，ｗｈｉｃｈｍｅｔｔｈｅＳｅｃｏｎｄｌｙ，ｔｈｅｄｉｓｐｏｓａｌｆｏｒｔｈｅｓｕｒｆａｃｅｏｆｒｅｑｕｉｒｅｍｅｎｔｓｏｆｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆｔｈｅｍａｇｎｅｔｉｃｆｌｕｉｄｓ，ｖｃａｓｄｏｎｅＳＯ懿ｔｏｒｅｄｕｃｅｔｈｅｓｕｒｆａｃｅｅｎｅｒｇｙｏｆｔｈｅｍａｇｎｅｔｉｃｐａｒｔｉｃｌｅｓ，ａｎｄｔｈｕｓｔｏｐｒｅｖｅｎｔｔｗｏｍａｇｎｅｔｉｃｐａｒｔｉｃｌｅｓｆｒｏｍａｐｐｒｏａｃｈｉｎｇｗｈｉｃｈｍｉｇｈｔｌｅａｄｔｏｃｏｎｇｒｅｇａｔｉｏｎａｎｄｓｅｄｉｍｅｎｔａｔｉｏｎｏｆｐａｒｔｉｃｌｅｓｉｎｃａｒｒｉｅｄｌｉｑｕｉｄｓ．ＴｈｅｅｆｆｅｃｔｓｏｆｔｈｅｄｉｓｐｏｓａｌｆｏｒｔｈｅｓｕｒｆａｃｅｏｆｍａｇｎｅｔｉｃｐｏｗｄｅｒｓｗｅｒｅｅｖａｌｕａｔｅｄｂｙＵＶｓｐｅｃｔｒａａｐｐａｒａｔｕｓ，ｒｅｓｅａｒｃｈｉｎｇｔｈｅｉｍｐａｃｔｓａｂｏｕｔｖａｌｅｓｏｆｐＨ，ｔｅｍｐｅｒａｔｕｒｅ，ｔｉｍｅａｎｄｃｏｍｐｏｕｎｄｓｕｒｆａｃｔａｎｔｓｏｎｔｈｅｅｆｆｅｃｔｓｏｆｔｈｅｄｉｓｐｏｓａｌｆｏｒｔｈｅｐａｒｔｉｃｌｅｓｕｒｆａｃｅ．Ｓｏｔｈｅｂｅｓｔｃｏｎｄｉｔｉｏｎｓｏｎｔｈｅｅｆｆｅｃｔｓｏｆｃｏａｔｉｎｇｆｏｒｐａｒｔｉｃｌｅｓｕｒｆａｃｅｗｅｒｅａｃｈｉｅｖｅｄ．Ｆｉｎａｌｌｙ，ｍａｇｎｅｔｉｃｐａｒｔｉｃｌｅｓ，ｗｈｉｃｈｗｅｒｅｃｏａｔｅｄｂｅｓｔ，ｗｅｒｅｄｉｓｐｅｒｓｅｄｕｎｉｆｏｒｍｌｙｉｎｔｈｅｃａｒｒｉｅｄｌｉｑｕｉｄｓｂｙｍｅａｎｓｏｆｔｒａｎｓｉｔｉｏｎｌｉｑｕｉｄｓ，ａｎｄｔｈｕｓｍａｇｎｅｔｉｃｌｉｑｕｉｄｓｗｅｒｅｆｏｒｍｅｄ．Ｉｎｔｈｅｅｘｐｅｒｉｍｅｒｉｔ，ＤＯＰｗａｓｕｓｅｄｆｏｒｃａｒｒｉｅｄｌｉｑｕｉｄｓ．Ｂｅｃａｕｓｅｉｔｓｆｒｅｅｚｉｎｇｐｏｉｎｔａｎｄｂｏｉｌｉｎｇｐｏｉｎｔｗｅｒｅａｔ－５０。

磁性氧化铁纳米粒子造影剂在MRI应用进展

中国实验诊断学
２１年１０１２月
第１５卷
第１２期
一
２１５一８
后介导的胞吞作用：常用的转染试剂有多聚左旋赖氨酸（Ｌ）硫酸鱼精蛋白等。通过静电相互作用，负电荷的ＰＬ、带ＳＩＰＯ与带正电荷的转染试剂结合形成复合物刺激细胞膜内
束（ｏ合成。这个反胶束的水相内核可溶解亲水的复合ｗ／）
物、盐类等。将含有Ｆ３ｅ和Ｆ２摩尔比２：）ｅ（１的溶液溶于
ＡＴｎ己烷形成的反胶束水核中，Ｏ／－加入氢氧化钠溶液实现沉
淀反应。更小的、均一的粒子可在低温下，更在氮气存在的条件下通过沉淀反应制备。反胶束内部水核的大小是纳米级的，以这些纳米反应器内部制备的磁粒子很小（于１所小５
备时常加入稳定剂如表面活性剂或聚合物以防止纳米粒子
的聚集。大多数的聚合物都吸附在表面特定的基质上。
但是选择包覆材料需要谨慎。粒子包覆材料可分为无
和基质中形成细小的晶体核，然后晶体长大。生长的过程通过物质转运和单体（即原子、子或分子）离的附加和移除维持
吞作用，从而将铁颗粒转运至细胞内。脂质体介导的胞吞作用：由于带有负电荷，氧化铁颗粒能被带正电荷的脂质体包
围。２— ４个脂质体与１个单个的对比剂分子或颗粒结合，然后这种脂质复合物与细胞胞浆膜融合，将对比剂转运至细胞液中。ＣｕＬ等 …对照脂质体介导的ＳＩｒｚＪＰＯ与单纯ＳＩＰＯ分别标记细胞，单纯使用ＳＩ接标记细胞所需ＳＩ度为转ＰＯ直ＰＯ浓染试剂介导后所需标记浓度的１０倍，０且细胞内的自由基生成增加，对细胞产生毒副作用。会

微纳米流动和核磁共振技术

微纳米流动和核磁共振技术英文回答：Microfluidics and nuclear magnetic resonance (NMR) are two important technologies that have revolutionized various fields of science and engineering.Microfluidics refers to the study and manipulation of fluids at the microscale level, typically in channels or chambers with dimensions ranging from micrometers to millimeters. It allows precise control and manipulation of small volumes of fluids, enabling a wide range of applications such as chemical analysis, drug delivery systems, and lab-on-a-chip devices. Microfluidic devices are often fabricated using techniques such as soft lithography, which involve the use of elastomeric materials to create microchannels and chambers.NMR, on the other hand, is a powerful analytical technique that utilizes the magnetic properties of atomicnuclei to study the structure and dynamics of molecules. It is based on the principle of nuclear spin, which is the intrinsic angular momentum possessed by atomic nuclei. By subjecting a sample to a strong magnetic field and applying radiofrequency pulses, NMR can provide information about the chemical composition, molecular structure, and molecular interactions of the sample. NMR has diverse applications in fields such as chemistry, biochemistry, medicine, and materials science.Microfluidics and NMR can be combined to create powerful analytical tools for studying various biological and chemical systems. For example, microfluidic devices can be used to precisely control the flow of samples and reagents, while NMR can provide detailed information about the composition and structure of the samples. This combination has been used in the development ofmicrofluidic NMR systems, which allow rapid and sensitive analysis of small sample volumes. These systems have been applied in areas such as metabolomics, drug discovery, and environmental monitoring.中文回答：微纳米流体力学和核磁共振技术是两种重要的技术，已经在科学和工程的各个领域引起了革命性的变化。

透射电镜差分相位分析技术磁畴研究

㊀第40卷㊀第11期2021年11月中国材料进展MATERIALS CHINAVol.40㊀No.11Nov.2021收稿日期:2021-07-14㊀㊀修回日期:2021-09-28基金项目:国家自然科学基金资助项目(11804343)第一作者:汤㊀进,男,1989年生,副研究员通讯作者:杜海峰,男,1979年生,研究员,博士生导师,Email:duhf@DOI :10.7502/j.issn.1674-3962.202107019透射电镜差分相位分析技术磁畴研究汤㊀进1,吴耀东1,2,熊奕敏1,田明亮1,杜海峰1(1.中国科学院合肥物质科学研究院强磁场科学中心极端条件凝聚态物理安徽省重点实验室,安徽合肥230031)(2.合肥师范学院物理与材料工程学院,安徽合肥230061)摘㊀要:透射电子显微镜具有高空间磁分辨率和易集成的多场调控等特点,成为当下纳米尺度下先进磁结构观测的主要手段之一㊂首先介绍和比较了透射电镜磁表征的3种模式:洛伦茨模式㊁电子全息模式和差分相位分析模式,然后详细综述了差分相位分析技术表征一类中心对称晶体Fe 3Sn 2材料中新型磁畴结构的研究进展㊂在该研究中,首先结合差分相位分析技术和三维微磁学模拟,阐释了中心对称材料中复杂多拓扑态磁畴起源于磁结构的三维特性,随后基于该材料温度诱导自旋重取向内禀物性,在Fe 3Sn 2受限纳米盘中,利用差分相位分析技术发现了一类全新的涡旋状磁结构靶磁泡 ,研究了其磁场演化行为,最后提出了斯格明子-磁泡基存储器的概念,并实现了磁场和电流高度可控斯格明子-磁泡拓扑磁转变㊂差分相位分析技术揭示的中心对称磁性材料纳米结构中的新颖磁畴及丰富的电流驱动动力学,有望促进未来基于新型磁畴结构的拓扑相关自旋电子学器件的开发㊂关键词:透射电子显微镜;差分相位分析;磁畴;斯格明子-磁泡;中心对称磁体中图分类号:TH742㊀㊀文献标识码:A㊀㊀文章编号:1674-3962(2021)11-0851-10Magnetic Domain Imaging by Differential PhaseContrast Technique of Transmission Electronic MicroscopyTANG Jin 1,WU Yaodong 1,2,XIONG Yimin 1,TIAN Mingliang 1,DU Haifeng 1(1.Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions,High Magnetic Field Laboratory,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,China)(2.School of Physics and Materials Engineering,Hefei Normal University,Hefei 230061,China)Abstract :Transmission electronic microscopy (TEM)has become one of the most advanced techniques to observe nano-metric-sized magnetic domains,owing to its high spatial magnetic resolution and easy accessibility in integrating multiple physic fields.Here,we compared three techniques of TEM observing magnetic domains:Lorentz-TEM,electronic hologra-phy and differential phase contrast scanning TEM (DPC-STEM).Then we reviewed recent advances in magnetic domains imaging of a centrosymmetric magnet Fe 3Sn 2by DPC-STEM.We demonstrated physical clarifications to multiple topological states ,which are attributed to three-dimensional (3D)depth-modulated spin configurations,using DPC-STEM and 3D mi-cromagnetic simulations.We then reported a new class of vortex-like spin configurations named target bubble and their field-driven magnetic evolutions in Fe 3Sn 2nanodisks.Finally,we proposed a new strategy to design memory named Skyrmi-on-bubble-based memory,which utilizes Skyrmions and bubbles as binary bits 1 and 0 ,respectively.Current-field-controlled topological Skyrmion-bubble transformations have been also achieved.The novel magnetic domains and their in-triguing electronic-magnetic properties shed by DPC-STEM are expected to facilitate advances in developing topology-related spintronic devices.Key words :transmission electronic microscopy;differential phase contrast;magnetic domain;Skyrmion-bubble;cen-trosymmetric uniaxial magnet1㊀前㊀言磁性材料已经被广泛应用于现代生活中,具有很大的市场价值,其中一个典型代表是自旋电子学磁功能器件[1]㊂自旋电子学是将电子的两个内禀属性电荷和自旋博看网 . All Rights Reserved.中国材料进展第40卷相结合的研究学科㊂以机械硬盘为代表的自旋电子学器件已经取得了较大的商业成功[2]㊂机械硬盘是利用磁化反平行排列的磁畴来表征双数据比特,通过读头的机械转动来实现读写㊂但是传统机械硬盘受到机械振动和热扰动的影响,其性能已趋于功能极限㊂为了突破功能极限,科学家们期望通过发现新型磁结构来构建新一代自旋电子学器件㊂磁斯格明子是新型磁结构的代表[3-5]㊂磁斯格明子是一类涡旋状新型磁结构,具有拓扑非平庸类粒子行为㊁可调的小尺寸和丰富的电磁相关动力学行为等特点[6]㊂磁斯格明子的关键稳定机制是材料体系中的Dzyaloshinskii-Moriya(DM)相互作用[7]㊂根据DM 相互作用类型,磁斯格明子主要分为3种:①具有体DM 相互作用的材料,如B 20型FeGe 和MnSi 材料中的布洛赫(Bloch)型磁斯格明子[3,4,8,9](图1a);②具有表面DM相互作用的材料,如铁磁/重金属异质结薄膜和C 3v 对称晶体GaV 4S 8中的奈尔(Néel)型磁斯格明子[10,11];③具有二维各向异性DM 相互作用的材料,如D 2d 晶体MnPdPtSn 中的反磁斯格明子[12]㊂此外,在传统中心对称单轴铁磁体中,偶极相互作用与单轴磁晶各向异性等的竞争也会产生出一类局域柱状畴磁结构磁泡,其中类型I 磁泡的闭合畴壁贡献了与Bloch 型手性斯格明子相同的整数拓扑荷,因此其也被称为磁泡斯格明子(图1b)[13-22]㊂近年来,这些具有丰富磁学㊁电学性质的磁斯格明子可以作为信息载体,用来构建存储器㊁逻辑器件㊁神经网络器件和互联信息器件等[23-25],形成了一类新兴的自旋电子学亚类学科拓扑自旋电子学[26-28]㊂图1㊀非中心对称螺磁体中布洛赫型磁斯格明子(a)[3,4,8,9];中心对称单轴铁磁体中的磁泡斯格明子(b)[13-22]Fig.1㊀Bloch-type Skyrmion in an noncentrosymmetric screw magnet (a)[3,4,8,9];Skyrmion bubble in a centrosymmetric uniaxialferromagnet (b)[13-22]拓扑自旋电子学研究领域关键的科学问题之一是磁斯格明子的电调控[23]㊂而未来自旋电子学器件高存储密度要求磁信息载体的尺寸为纳米尺度,因此需要探索纳米尺度下的磁斯格明子的相关性能,这要求磁表征技术的高空间分辨率㊂现代磁学的发展也得益于先进磁表征技术的发展㊂依据自旋与电流㊁电子㊁光等的相互作用,科学家们已经开发出了多种先进的磁表征技术[26],如表1所示[11,23,29-31]㊂其中,透射电镜不仅能够观测纳米尺度范围内的磁畴,也易于集成多物理场条件,对样品和外界环境要求相对较低[32]㊂因此,透射电镜成为了近年来高分辨率磁表征的重要技术手段,极大地推动了磁斯格明子相关的研究进展,例如磁斯格明子的首次实空间观测[4]㊁磁浮子的首次实空间观测[33]㊁反斯格明子的首次实空间观测等,都是利用透射电镜技术实现的[12]㊂本文将首先介绍基于透射电镜的3种基本磁表征手段,并随后着重综述透射电镜差分相位分析技术表征一类中心对称晶体中的新型磁畴结构的研究进展㊂表1㊀磁表征技术:洛伦茨透射电子显微镜㊁磁力显微镜㊁自旋极化扫描隧道显微镜㊁X 射线显微学㊁表面磁光克尔效应㊁X-射线磁圆二色仪-光发射电子显微镜[11,23,29-31]Table 1㊀Magnetic imaging techniques :Lorentz-transmission elec-tronic microscopy (Lorentz-TEM ),magnetic force mi-croscopy (MFM ),spin-polarized scanning tunneling mi-croscopy (spin-polarized STM ),X-ray holography (X-ray holography ),surfacemagneto-opticalKerreffect(SMOKE ),X-ray magnetic circular dichroism-photoe-mission electron microscopy (XMCD-PEEM )[11,23,29-31]Techniques ResolutionSpatial /nm Time Field /T Temperature/K Lorentz-TEM ~2ms -2~25~1300MFM~10s -16~162~400Spin-polarized STM~0.5s-9~9<10X-ray holography~20nsSMOKE~300ns -9~92~800XMCD-PEEM~25s02~3002㊀透射电镜磁表征技术透射电镜磁表征技术是基于电子在磁场运动过程中受到的洛伦茨力,因此磁表征的透射电镜也被称作洛伦茨透射电镜[4,32]㊂透射电镜电子束的传输方向为垂直于样品表面,由于电子的轨迹只受到与其运动方向垂直的磁场的影响,因此洛伦茨透射电镜只能表征面内磁矩㊂此外,透射模式也表明透射电镜探测到的是样品厚度方向积分的磁矩㊂依据电子受到洛伦茨力发生偏转的探测方式,透射电镜磁表征技术可以分成3种(图2):欠焦/过焦情况下的菲涅尔磁衬度,即传统洛伦茨技术[4];通过分辨样品和全息丝的干涉条纹宽度的变化来获得磁相位,即电子全息技术[34-37];扫描聚焦电子束通过样品后,4个分立探头探测的电子束强度的差异等价于磁相位衬度差分,即差分相位分析扫描透射电镜技术[13,15,16,38-40]㊂258博看网 . All Rights Reserved.㊀第11期汤㊀进等:透射电镜差分相位分析技术磁畴研究图2㊀透射电镜3种磁表征技术示意图:洛伦茨[4]㊁电子全息[34-37]和差分相位分析[13,15,16,38-40]Fig.2㊀Schematic designs of three magnetic imaging techniques of trans-mission electronic microscopy:Lorentz [4],electronic hologra-phy [34-37]and differential phase contrast scanning [13,15,16,38-40]根据不同透射电镜磁成像技术的特点,3种方式各具特色,但也存在着缺点㊂传统离焦下表征的洛伦茨模式是最早也是现在最流行的透射电镜磁成像表征方式[20],具有易于操作㊁比较直观反射磁结构和成像速度快等优点,但是这种方法也有以下缺点:①由于离焦状态下样品边缘具有菲涅尔强衍射,使得该方法不适用于太小受限结构的磁分辨[41];②作为一种间接获得磁相位的方法,传统输运强度分析(transport of intensity equation,TIE)技术解析磁结构的过程中可能会引入一些人为的磁信息,造成严重的偏差[42]㊂电子全息技术是一种正焦模式下直接表征磁相位的方法,能够非常准确和定量地解析磁结构[34-37],但是这种方法也有以下缺点:①电子全息模式观测到的是干涉条纹[34],不能直观反映磁结构,不适用于一些快速磁结构动力学响应的表征;②由于干涉所需的参考光束需要经过真空,因此电子全息只能表征靠近样品边缘的磁结构,有效观测尺寸大约为1μm [37]㊂差分相位分析扫描透射模式也是一种正焦状态下直接探测磁矩的方式(图3),具有磁成像精度高㊁范围广等优点,特别是能够精确表征样品缺陷处的磁结构信息[13,15,16,38-40],但是该方法也有以下缺点:①扫描聚焦模式成像较慢(数十秒以上),不适用于实时磁结构动力学表征;②扫描聚焦模式下会对样品造成损伤㊂从以上讨论可以得出,相比于传统洛伦茨模式,电子全息和差分相位分析都是更为精确的磁相位表征技术,但是电子全息只适用于一些小样品的表征,而差分相位分析技术并不受到样品尺寸的限制,可以表征任意尺寸磁样品的磁结构㊂本文将着重介绍差分相位分析方法在偶极磁斯格明子材料的新型磁结构表征中的近期科研进展㊂3㊀差分相位分析磁畴表征3.1㊀三维磁斯格明子与磁泡由于单轴磁晶各向异性㊁偶极-偶极相互作用㊁交换图3㊀差分相位分析方法分析磁畴的过程[13,15,16,38-40]:(a ~d)扫描透射模式下,4个分立的差分衬度探头A㊁B㊁C 和D 得到聚焦电子束穿过一个直径为1550nm 的Fe 3Sn 2纳米盘的衬度图像;(e)探头A 和C 的差分衬度,与样品中沿着y 轴的磁场强度成正比;(f)探头B 与D 的差分衬度,与样品中沿着x 轴的磁场强度成正比;(g)通过(A -C)2+(B -D)2计算出的整个面内磁场强度分布图;(h)最终重构的面内场强分布图Fig.3㊀Analysis procedure for determining the magnetic structure in a1550nm Fe 3Sn 2disc by using differential phase contrast scan-ning TEM [13,15,16,38-40]:(a ~d)differential phase contrastcomponent images from the four segments of the detectors A,B,C and D,respectively;(e)differential phase contrast compo-nent obtained by subtracting C from A (A -C),which is propor-tional to the field component along the y axis;(f)differential phase contrast component obtained by subtractingD from B (B -D),which is proportional to the field component along the x axis;(g )totalin-planefieldstrengthobtainedfrom(A -C)2+(B -D)2;(h)in-plane magnetization mapping相互作用和外磁场赛曼能的竞争,中心对称单轴磁性材料能够形成局域的柱状磁畴结构,该结构被称为磁泡(图1b)[20,43,44]㊂虽然磁泡在20世纪70~90年代得到了大量的研究,并构建了磁泡存储器等功能性器件[45],但由于该器件的大尺寸(微米尺度)不适用于紧凑的器件设计而逐渐被淘汰[43]㊂最近,新型涡旋局域磁结构斯格明子的发现也重新引起了研究人员对传统磁泡的广泛兴趣[21,22,31,42,46-54]㊂依据柱状磁畴的畴壁磁化分布,磁泡可分为类型I 拓扑非平庸磁泡和类型II 拓扑平庸磁泡[21]㊂其中具有闭合畴壁的类型I 磁泡具有与磁斯格明子相同的拓扑性,也被称为斯格明子磁泡[31,51-54]㊂特别地,最近的研究发现了直径小于50nm 的斯格明子磁泡和自旋转移力矩驱动磁泡动力学行为[17,31,54]㊂这些研究成果也预示着传统磁泡可以被用来构建新型高性能自旋电子学器件[18]㊂为简便表述,后文将中心对称晶体中的类型I 斯格明子磁泡和类型II 磁泡分别称为磁斯格明子和磁泡㊂358博看网 . All Rights Reserved.中国材料进展第40卷虽然中心对称晶体中的磁斯格明子和磁泡结构已经得到了很好的理论解析[55],但在近期采用透射电镜研究磁泡材料磁畴工作中发现了复杂的多拓扑态磁结构[22,47]㊂这些复杂磁结构与传统磁斯格明子和磁泡结构有很大差异,同时一直没有得到很好的物理解释,限制了磁泡材料的未来应用性㊂分析可知,这些复杂多拓扑态磁结构均是通过透射电镜洛伦茨模式得到,且解析的磁结构被认为是二维的㊂传统洛伦茨模式表征磁结构是通过TIE 技术解析过焦㊁正焦和欠焦菲涅尔磁衬度得到的㊂而为了得到更清晰的磁结构,TIE 技术通常需要设定滤波参数来过滤噪音和非磁背景,但滤波也可能会得到偏离真实情况的磁结构[42];同时TIE 技术也不适用于解析传统均匀铁磁磁畴[14,16]㊂透射电镜技术得到的是沿着样品厚度方向的积分磁化分布,但以往的研究认为磁结构在厚度方向为磁化均匀的[22,47]㊂作者团队[16]采用透射电镜差分相位分析-扫描透射模式和三维微磁学计算模拟相结合的方式,系统地研究了Kagome 中心对称晶体材料Fe 3Sn 2中的复杂多拓扑态多环和Φ形-圆弧形磁涡旋结构,如图4所示㊂Fe 3Sn 2是一类室温单轴铁磁体[56-61],单轴磁化易轴在室温下沿着c 轴㊂同时,Fe 3Sn 2为低品质因子材料,即单轴磁晶各向异性K u 小于12μ0M 2s ,μ0和M s 分别为真空磁导率和饱和磁化率㊂通过三维微磁学计算模拟发现[62],对于低品质因子的Fe 3Sn 2薄片样品,强的偶极-偶极相互作用会导致磁斯格明子和磁泡沿着厚度方向发生连续自旋扭转,形成界面涡旋状磁结构㊂因此,上述模拟结果表明,Fe 3Sn 2纳米薄片样品的磁斯格明子和磁泡沿着厚度方向不是均匀磁化的(图4e 和4f),因此在透射电镜解析的磁结构中必须考虑厚度方向的积分磁化分布㊂同时,利用差分相位分析进一步得到了Fe 3Sn 2纳米薄片样品的多环状和圆弧形涡旋磁结构(图4a 和4b),发现其与传统洛伦茨模式解析磁结构有很大差异,但与三维微磁模拟的磁斯格明子和磁泡的积分磁化分布高度一致(图4c 和4d)㊂这些研究结果表明, 多拓扑态起源于传统中心对称材料中的三维磁斯格明子和磁泡结构,磁结构的复杂性是由于非均匀三维磁结构投射到二维平面后的积分相加所导致的㊂3.2㊀靶磁泡的发现及其磁场驱动演化过程Fe 3Sn 2的磁晶各向异性具有强温度依赖性,单轴磁各向异性常数K u 随着温度降低而减小,因此易磁化方向会由高温时的c 轴转变到低温时的ab 易磁化面,即温度诱导自旋重取向[61]㊂本课题组[13]制备了不同尺寸受限Fe 3Sn 2纳米盘,利用差分相位分析研究了其零磁场下的图4㊀Fe 3Sn 2纳米结构中类型I 斯格明子磁泡和类型II 拓扑平庸磁泡的三维磁结构[16]:(a,b)差分相位分析方法得到的面内自旋分布;(c,d)三维微磁模拟得到的平均面内磁化分布;(e,f)三维微磁模拟得到的厚度调制磁结构Fig.4㊀3D spin texture of type-I Skyrmion bubble and type-II topologi-cally trivial bubble in the Fe 3Sn 2nanostructure [16]:(a,b)in-plane magnetization mappings of two types of bubbles obtainedfrom differential phase contrast technique;(c,d)average in-plane magnetization mappings of two types by 3D micromagnetic simulation;(e,f)depth-modulated 3D magnetic bubbles by 3Dmicromagnetic simulation磁畴演化行为,如图5所示㊂由于在传统洛伦茨模式离焦磁表征模式下,受限小尺寸样品边缘强的菲涅尔衍射条纹给磁结构解析带来极大的干扰,因此正焦模式下工作的差分相位分析技术更适用于精确研究受限体系下的磁畴结构㊂不同于在高温300K 的条纹畴磁基态(图5a),在低温100K 的易面磁化Fe 3Sn 2(001)纳米盘中,偶极-偶极相互作用会诱导面内磁矩沿着圆盘边缘排列,形成经典的软磁磁涡旋结构(图5b)㊂以软磁磁涡旋为种子磁结构,当升高温度到室温,易面磁纳米盘转变为垂直磁纳米盘,Fe 3Sn 2(001)纳米盘中会形成多环靶态磁结构,命名其为靶磁泡 (图5c)㊂通过分析靶磁泡的中间层磁化分布,发现其自旋从中心到最外边缘旋转了π的整数(k )倍(图5d),因此中心对称晶体中的靶磁泡也可以被看作k π-磁斯格明子㊂这种自旋重取向导致的软磁磁涡旋到靶磁泡的转变可被微磁模拟重复出来(图5e ~5h)㊂458博看网 . All Rights Reserved.㊀第11期汤㊀进等:透射电镜差分相位分析技术磁畴研究图5㊀在Fe 3Sn 2纳米盘中通过在零磁场下加热到室温的方式,利用差分相位分析技术观测到的室温下的条纹畴到低温下的软磁磁涡旋到室温下的靶磁泡(k π-磁斯格明子)的转变[13]:(a)300K 室温条纹畴;(b)100K 磁涡旋;(c)300K 室温靶磁泡;(d)沿着图5c 中A 到B 位置连线相关面内磁化强度;(e)模拟的室温条纹畴;(f)模拟的100K 磁涡旋;(g)模拟的室温靶磁泡;(h)模拟的沿着图5g 中C 到D 位置连线相关面内磁化强度Fig.5㊀Transformation from a soft magnetic vortex at 100K to a target bubble (k π-Skyrmion)at 300K through zero-field warming in an Fe 3Sn 2nanodisk obtained by differential phase contrast [13]:(a)experimental stripes at 300K;(b)soft vortex at 100K;(c)target bubble at300K;(d)position dependent in-plane magnetization amplitude along the line A to B in Fig.5c;(e~g)simulated stripes with uniaxi-al magnetic anisotropy K u =53.0kJ /m 3,soft vortex with K u =2.3kJ /m 3and target bubbles with K u =53.0kJ /m 3;(h)simulated posi-tion dependent in-plane magnetization amplitude along the line C to D in Fig.5g㊀㊀k π-磁斯格明子的拓扑荷为0(k 为奇数)或1(k 为偶数)㊂前期研究表明,k π-磁斯格明子具有k 相关可调自旋波激发和多场调控磁性等特点,其中2π-磁斯格明子(也叫做类斯格明子Skyrmionium)被提出可以用来构建无垂直漂移赛道存储器和斯格明子互联器件等[63,64]㊂但k π-磁斯格明子的研究多为理论模拟研究,仅仅在极少数的磁系统中被观察到[65,66],k π-磁斯格明子(k >2)的实验发现尤其充满挑战㊂通过以软磁磁涡旋为种子磁结构以及调节Fe 3Sn 2(001)纳米盘的直径,得到了丰富的零磁场稳定的k π-磁斯格明子(k =2,3,4和5)㊂与手性磁体中零磁场下两种简并的k π-磁斯格明子相比较,理论上中心对称材料中的零磁场k π-磁斯格明子有2k +1种㊂此外,之前的理论研究也预言了磁场诱导的k π-磁斯格明子的新颖磁性[67-70],但相关的实验研究还很少㊂因此,本课题组[15]进一步利用差分相位分析研究了Fe 3Sn 2(001)纳米盘中的磁场演化行为,如图6所示㊂磁场驱动下,Fe 3Sn 2(001)纳米盘k π-磁斯格明子主要呈现出3个特点:①零磁场下的不规则形状转变为高磁场下的轴对称形状(图6a);②磁场诱导k 系数的减小;③k π-磁斯格明子直径随磁场增强而连续减小(图6b)㊂中心对称Fe 3Sn 2纳米盘中的k π-磁斯格明子具有室温和零磁场稳定性㊁丰富多重简并态以及利用外磁场和图6㊀Fe 3Sn 2纳米结构中采用差分相位分析技术观测到的磁场诱导的k π-磁斯格明子(靶磁泡)的磁演化行为[15]:(a)实验观测的高磁场下稳定的圆形k π-磁斯格明子;(b)k π-磁斯格明子的直径随着磁场强度的变化关系,图中正方形点㊁三角形点和圆形点分别代表4π㊁3π和2π磁斯格明子Fig.6㊀Field-driven magnetic evolutions of k π-Skyrmion in Fe 3Sn 2nan-odisks obtained by differential phase contrast [15]:(a)roundk π-Skyrmions stabilized at high fields;(b)field B dependent diameter of k π-Skyrmions,the square,triangle,and circle sym-bols in Fig.6b denote the parameter k with values of 4,3,and2,respectively558博看网 . All Rights Reserved.中国材料进展第40卷纳米盘直径可实现可调k参数等特点,有望进一步被应用于新型磁电子学器件的设计中㊂3.3㊀可逆电流调控磁斯格明子-磁泡拓扑磁转换中心对称Fe3Sn2材料中有两种局域磁结构:磁斯格明子和磁泡㊂传统的磁斯格明子基存储器是将磁斯格明子和铁磁态看作数据比特的 1 和 0 [29]㊂但是由于热扰动和斯格明子间的相互作用[33,71],斯格明子的非定向运动会造成数据链的混乱㊂而为了抑制斯格明子的无序运动,需要在传统斯格明子基存储器中的每个数据比特位构建人工缺陷,这无疑会增加器件构建的成本㊂我们提出采用磁泡替代传统铁磁空隙当作数据比特 0 来构建磁斯格明子-磁泡存储器,如图7a~7d所示[18]㊂当磁场完全垂直于Fe3Sn2(001)纳米结构时,为了使偶极-偶极相互作用能最小化,柱状畴形成具有闭合磁畴的磁斯格明子稳定相㊂当磁场不是完全垂直于Fe3Sn2 (001)纳米结构而具有大的面内磁场时,为了使赛曼能最小化,柱状畴形成具有朝向面内磁场方向磁畴的磁泡稳定相㊂当磁场的倾斜角度适中时,磁斯格明子和磁泡是稳定共存,也是磁斯格明子-磁泡存储器实现的前提㊂在强受限Fe3Sn2(001)纳米条带中,通过施加一个5ʎ倾斜的磁场,成功实现了磁斯格明子-磁泡单链(图7e),这种磁斯格明子-磁泡单链被当作一串数据比特㊂图7㊀一种基于磁斯格明子和磁泡的存储器原型的提出[18]:(a)斯格明子-磁泡存储器概念设计图;(b)代表数据比特 1 的斯格明子磁结构;(c)用磁泡替代铁磁来代表数据比特 0 ;(d)磁泡的菲涅尔磁衬度;(e)Fe3Sn2纳米条带中实现的磁斯格明子-磁泡单链,可以用来代表磁斯格明子-磁泡存储器中的一串 11011000001 数据链Fig.7㊀Propose of a magnetic memory based on Skyrmions and bubbles[18]:(a)schematic design of Skyrmion-bubble-based magnetic memory;(b)a Skyrmion representing the data bit 1 ;(c)a bubble replacing ferromagnet to represent the data bit 0 ;(d)Fresnel contrast of the bubble;(e)experimental realization of a single Skyrmion-bubble chain to represent the data bit11011000001 in a Fe3Sn2nanostripe㊀㊀磁斯格明子和磁泡的拓扑荷分别为1和0,具有截然不同的拓扑相关物性,如斯格明子霍尔效应和拓扑霍尔效应[72-75]㊂可控的磁斯格明子和磁泡的产生及其相互转换能够促进拓扑相关的磁电子学器件的开发㊂依据磁斯格明子和磁泡的产生机制,通过倾转外磁场能够有效调控磁斯格明子和磁泡的产生和转换[21,50]㊂本课题组[19]研究了Fe3Sn2纳米盘中磁斯格明子和磁泡的稳定性以及他们之间磁场诱导的拓扑磁转换,发现磁盘中磁斯格明子和磁泡的数量不仅与纳米盘直径有关,还与磁场角度相关㊂当纳米盘直径减小到~540nm时,该受限结构中最多只能稳定一个磁斯格明子或磁泡㊂通过固定外磁场强度同时调节其相对于磁盘法向的角度,成功实现了单斯格明子-单磁泡间可控的拓扑磁转换,如图8所示㊂两类磁状态间的拓扑磁转变可以用于器件的写入和删除等功能,但磁场方法不兼容于当代和未来的电子学器件设计和应用,而电学调控磁斯格明子-磁泡的拓扑转变的研究仍有待发掘㊂因此,本课题组进一步探索了电流可控磁斯格明子-磁泡相互转变的可能性[17]㊂在Fe3Sn2(001)纳米薄片中,磁场小角度倾斜于薄片法向时,磁斯格明子和磁泡都是稳定的磁状态㊂当设置磁斯格明子晶格为初始磁状态,施加高密度纳秒电流脉冲后,会发生磁斯格明子到磁泡的转变;当设置磁斯格658博看网 . All Rights Reserved.㊀第11期汤㊀进等:透射电镜差分相位分析技术磁畴研究图8㊀Fe 3Sn 2纳米结构中磁场诱导的斯格明子-磁泡转换[19]:(a~e)洛伦茨模式观测的斯格明子-磁泡转换,(f ~j)对应的微磁模拟的斯格明子-磁泡转变,(k)斯格明子-磁泡转变过程中的拓扑数的变化,(l)斯格明子-磁泡转变过程中的总自由能密度随磁场角度的变化Fig.8㊀Field-induced topological Skyrmion-bubble transformations in Fe 3Sn 2nanodisks [19]:(a ~e)Skyrmion-bubble transformationsobtained by Lorentz-TEM,(f ~j)corresponding Skyrmion-bubble transformations obtained by micromagnetic simulation,(k)winding number as a function of tilted field angle,(l)total free energy density as a function of tilted field angle明子晶格为初始磁状态,施加低密度纳秒电流脉冲后,会发生磁泡到磁斯格明子的转变㊂重要的是,通过调控电流幅度,这种磁斯格明子-磁泡相互转变是完全可逆的,如图9所示[17]㊂利用微磁学计算模拟发现,电流可控磁斯格明子-磁泡相互转变可被归因于自旋转移力矩和焦耳热效应的综合作用㊂当施加高密度电流脉冲时,电流的焦耳热会导致样品升温而发生热退磁,而在两个电流脉冲的间隙,样品又会降温而发生磁恢复过程㊂在热退磁的过程中,样品的饱和磁场强度会降低,而外加磁场强度固定不变,因此会发生磁斯格明子到铁磁态的转变㊂由于磁场是倾斜于样品垂直方向的,因此铁磁态是具有一定面内分量的倾斜铁磁态,面内磁化分量平行于面内磁场分量㊂而在降温的磁化恢复过程中,由于磁泡的畴壁磁化是与倾斜磁化背景一致,因此磁泡更优先于磁斯格明子从倾斜磁化背景中产生㊂特别地,即使磁泡的总自由能能量高于磁斯格明子,这种磁斯格明子到倾斜铁磁到磁泡转变的过程也能够发生㊂而低密度脉冲电流诱导的磁泡到磁斯格明子的产生归因于自旋转移力矩效应㊂磁泡的能量要高于磁斯格明子,自旋转移力矩相当于一个外界激发,能够使高能亚稳磁泡产生变形而处于一个非稳定状态,从而能够越过能量势垒转变到低能磁斯格明子稳定态㊂此外,在Fe 3Sn 2(001)纳米薄片中,在较低外磁场下,磁泡会转变为条纹磁畴㊂之前的研究中已经能够实现电流控制条纹磁畴到磁斯格明子的转变,但其逆过程磁斯格明子到条纹磁畴的转变还比较少见[31,76-82]㊂通过高低纳秒脉冲电流切换,同样能够实现磁斯格明子-条纹磁畴的可逆和可重复的拓扑磁转换㊂4㊀结㊀语本文阐述了将差分相位分析技术应用到偶极磁斯格明子/磁泡材料Fe 3Sn 2中的新型磁结构观测和电驱动拓扑磁转变动力学研究中的进展,研究结果表明,差分相位技术推动了三维磁结构㊁靶磁泡/k π-磁斯格明子等新型磁结构的精确表征,澄清了中心对称晶体中复杂磁结构的起源,并为后续的新型磁结构相关自旋电子学的应用奠定了重要基础㊂本课题组也提出了磁斯格明子-磁泡存储器的概念设计,并在实验室实现了单链磁斯格明子-758博看网 . All Rights Reserved.。

柠檬酸盐络合_共沸蒸馏_低温燃烧法制备纳米铁酸镍粉及其表征

柠檬酸盐络合共沸蒸馏低温燃烧法制备纳米铁酸镍粉及其表征谢宇1,2,傅毛生1,魏娅1,洪小伟1,余远福1,钟荣1,高云华2(1.南昌航空大学材料与化学工程系,南昌330063;2.中国科学院光化学转换与功能材料重点实验室,理化技术研究所,北京100190)摘要:采用柠檬酸盐络合法制备出铁酸镍湿凝胶,经共沸蒸馏后将所得的前驱体在电炉上直接加热低温燃烧制备出了铁酸镍粉体,运用XRD、T EM和激光粒度仪等对铁酸镍粉体进行了表征。

结果表明:经过共沸蒸馏脱水制备的铁酸镍粉体具有单一尖晶石结构,颗粒尺寸均匀,粒径在80~100nm,颗粒分散性好。

关键词:柠檬酸盐络合法;低温燃烧法;共沸蒸馏脱水;铁酸镍中图分类号:T B383 文献标志码:A 文章编号:1000 3738(2011)05 0069 03Preparation of Nanosize Nickel Ferrite Powders by Citrin Coordination Azeotropic Distillation Process Low TemperatureCombustion Method and Its CharaterizationXIE Yu1,2,FU Mao sheng1,WEI Ya1,HONG Xiao wei1,Y U Yuan fu1,ZHONG Rong1,GAO Yun hua2(1.Department of M ater ial Chemistr y,Nanchang H ang ko ng U niv er sity,N anchang330063,China;2.K ey L aborat ory of P ho tochemical Conver sion and O pto electro nic M aterials,T IPC,CA S,Beijing100190,China)Abstract:N ickel fer rit e wet g elat in was prepared by citrin co or dination method fir stly,and then the pr ecur so r prepared via azeotr opic distillation process was dir ect ly heated on a electric co oker and ig nited at low temper atur e to prapare the nickel ferr ite pow der s,w hich wer e characterized by X ray diffractio n,T r ansmissio n electro nic microscopy(T EM)and laser scatter ing particle size analy zer.T he r esult s show that the nickel fer rite po wders prepared by using azeo tro pic distillatio n process to dehy dr ate a mount o f fr ee w at er had sing le spinel st ructur e,uniform and well dispersed part icles,and the particles diamet er w as80-100nm.Key words:citr in co or dination metho d;low temperature co mbustio n;azeo tro pic distillation process;nickel ferr ite0 引言铁酸镍(NiFe2O4)是一种性能优良的软磁铁氧体材料,在电子工业领域中常用作磁头材料、矩磁材料、微波吸收材料和磁致伸缩材料[1],同时其还在CO2直接还原成碳的反应中表现出良好的催化性收稿日期:2010 04 23;修订日期:2011 01 07基金项目:国家自然科学基金资助项目(20904019);航空科学基金资助项目(2008ZF56017、BA200902350);中国科学院光化学转换与功能材料重点实验室开放课题基金资助项目(PCOM201028);江西省教育厅科技项目(GJJ11501)作者简介:谢宇(1975-),男,江西宜黄人,教授,博士。

脉冲电化学法制备_海绵状_聚苯胺

2
2． 1
结果与讨论
产物的形貌和结构表征
图 1 是脉冲电化学聚合法制备的 PANI 以及剥离了 PANI 后的 ITO 导电玻璃表面的扫描电镜图（ SEM）．
PANI（ a、 b、 c）和 PANI 剥离后 ITO 导电玻璃表面（ d）的 SEM 图图 1 “海绵状” Fig． 1 SEM images of spongelike polyaniline （ a， b， c） and the surface （ d） of ITO substrate after removal of the PANI film
+
振动频率 / cm 804 1 135 1 241 1 303 1 482 1 575
－1
注： B 表示聚苯胺的苯环结构； Q 表示聚苯胺的醌环结构
FTIR spectrum of the PANI
1 575 cm － 1 处为 NQN 中 CN 伸缩振动吸收峰， 1 482 cm － 1 对应由图 2 及表 1 可知， NBN 中 CN 伸缩振动吸收峰， 1 303 cm － 1 处为 NH 弯曲振动吸收峰， 1 241 cm － 1 为 CN －1 伸缩振动吸收峰，此外，在 1 135 cm 处的吸收峰的强度非常大，而该吸收峰对应 CH 的（ CH 来自 BN 或 QN 中）面内弯曲振动吸收峰，该结构中的 CH 键与制备 PANI 过程中质子化作用相
表1 Tab． 1 图 2 中 PANI 的主要 FTIR 振动频率 Main FTIR vibration frequencies of the PANI in Fig． 2 振动模式 CH 面外弯曲振动 BNH B 或 QN CN 伸缩振动 CH 弯曲振动 NBN 伸缩振动 NQN 伸缩振动图2 Fig． 2 PANI 的红外谱图

二硫化钛纳米片材料用于光声成像指导下的肿瘤光热治疗研究

二硫化钛纳米片材料用于光声成像指导下的肿瘤光热治疗研究随着肿瘤的发病率不断增加，对于肿瘤的治疗研究也越来越受到重视。

近年来，光声成像指导下的肿瘤光热治疗逐渐成为一种被广泛研究的方法。

在这种治疗方法中，纳米材料被用作光热转换剂，以实现对肿瘤组织的精确灭活。

二硫化钛纳米片作为一种具有优良光热转换性能的纳米材料，近年来在肿瘤光热治疗研究中受到了广泛的关注。

首先，二硫化钛纳米片具有优异的光热转换性能。

作为一种二维纳米材料，二硫化钛纳米片具有高比表面积和特殊的电子结构，这使得它具有良好的光热转换效率。

在光照作用下，二硫化钛纳米片能够吸收光能并迅速转化为热能，从而产生高温。

这种光热效应可以被应用于肿瘤光热治疗中，将其置于肿瘤组织中，然后通过外部激光的照射来激活其光热效应，从而实现对肿瘤组织的灭活。

其次，二硫化钛纳米片具有较好的可控性。

二硫化钛纳米片的光热效应能够通过调节外部激光的功率、波长和持续时间来实现精确控制。

即使在低功率激光照射下，二硫化钛纳米片也能够产生足够的热量，从而实现对肿瘤组织的灭活。

此外，二硫化钛纳米片还可以通过改变其形态和尺寸来实现对光热效应的调控，以满足不同肿瘤组织的治疗需求。

此外，二硫化钛纳米片还具有良好的生物相容性。

二硫化钛纳米片的合成方法多种多样，可以通过化学气相沉积法、热蒸发法和溶液法等多种方法来制备。

这些方法可以得到具有良好生物相容性的纳米片材料。

此外，二硫化钛纳米片在体内能够被肿瘤组织选择性富集，从而减少了对正常组织的伤害。

这使得二硫化钛纳米片成为一种理想的纳米材料，用于光声成像指导下的肿瘤光热治疗。

综上所述，二硫化钛纳米片作为一种具有优异光热转换性能、可控性和生物相容性的纳米材料，有望在光声成像指导下的肿瘤光热治疗中发挥重要的作用。

未来的研究可以进一步探索二硫化钛纳米片的制备方法和生物效应，以期实现其在临床肿瘤治疗中的应用。

Film and method for producing nano-particles for m

专利名称：Film and method for producing nano-particles for magnetoresistive device发明人：Rachid Sbiaa,Isamu Sato,Haruyuki Morita申请号：US12179293申请日：20080724公开号：US08023232B2公开日：20110920专利内容由知识产权出版社提供专利附图：摘要：A method of generating a thin film for use in a spin valve of a magnetoresistive (MR) sensor having a nano-constricted spacer is provided. The bottom portion of the spin valve is deposited up to the pinned layer, a deposition chamber is provided, and thespacer layer is sputtered thereon. A main ion beam generates ions onto a composite surface including magnetic chips and insulator material. Simultaneously, an assisted ion beam provides ions directly to the substrate, thus improving the softness of the free layer and smoothness of the spacer layer. Neutralizers are also provided to prevent ion repulsion and improve ion beam focus. As a result, a thin film spacer can be formed, and the nano-constricted MR spin valve having low free layer coercivity and low interlayer coupling between the free layer and pinned layer is formed.申请人：Rachid Sbiaa,Isamu Sato,Haruyuki Morita地址：Tokyo JP,Tokyo JP,Tokyo JP国籍：JP,JP,JP代理机构：Sughrue Mion, PLLC更多信息请下载全文后查看。

纳米晶高性能永磁材料特邀论文

Journal of Magnetism and Magnetic Materials242–245(2002)1277–1283Invited paperNanocrystalline high performance permanent magnets O.Gutﬂeisch*,A.Bollero,A.Handstein,D.Hinz,A.Kirchner,A.Yan,K.-H.M.uller,L.SchultzInstitute of Solid State and Materials Research,IFW Dresden,P.O.Box270016,01171Dresden,GermanyAbstractRecent developments in nanocrystalline rare earth–transition metal magnets are reviewed and emphasis is placed on research work at IFW Dresden.Principal synthesis methods include high energy ball milling,melt spinning and hydrogen assisted methods such as reactive milling and hydrogenation-disproportionation-desorption-recombination. These techniques are applied to NdFeB-,PrFeB-and SmCo-type systems with the aim to produce high remanence magnets with high coercivity.Concepts of maximizing the energy density in nanostructured magnets by either inducing a texture via anisotropic HDDR or hot deformation or enhancing the remanence via magnetic exchange coupling are evaluated.r2002Elsevier Science B.V.All rights reserved.Keywords:Permanent magnets;Nanocrystalline materials;Exchange coupling;Texture;Hydrogen absorption1.IntroductionNanocrystalline materials,including those of mag-netic materials,have been at the centre of numerousR&D activities during the last decade because of theirparticular scientiﬁc and technological properties.In thecase of hard magnetic rare earth–transition metal(R–T)compounds,it is the grain size and the presence orabsence of intergranular phases which give rise tounusual magnetic properties because of surface/interfaceeffects different from those of bulk or microcrystallinerge coercivities can be obtained once thegrain size is below a certain threshold where thecrystallites become single domain.In most of the R–T-compounds discussed here,the critical single-domainparticle size d c is a fraction of a micron.Assuming idealized microstructures,three prototypesof NdFeB-type magnets can be distinguished on thebasis of the ternary phase diagram[1]:Type(I)israre earth rich and the individual crystallites are sepa-rated by a thin paramagnetic layer,the rare earth-richintergranular phase.This structure leads to a decouplingof the hard magnetic grains resulting in high coercivities.Type(II)is obtained using the stoichiometric R2Fe14Bcomposition and the hard magnetic grains are in directcontact with each other(‘single-phase exchange coupledmagnets’)[2].Type(III)nanocomposite magnets are Rdeﬁcient(i.e.,R concentrations o11.76at%)and thecoupling occurs between the R2Fe14B grains(to providehigh coercivity)and soft magnetic Fe3B or Fe rich grains(to provide high magnetisation;e.g.J sða2FeÞ¼2:16T).The exchange interaction between the grains of thedifferent phases leads to single-phase demagnetisationcurves despite a multi-phase microstructure providedgrain sizes are below a certain threshold and para-magnetic intergranular phases are absent[3–5].En-hanced remanences of the isotropic hard magneticmaterials,larger than those predicted by the Stoner-Wohlfarth theory[6]for systems of isotropicallyoriented,magnetically uniaxial,non-interacting singledomain particles where M r=M S p0:5;are the conse-quence.The development of melt-spun or rapidly quenchedNd–Fe–B magnets by Croat and Herbst[7]coincidedwith that of sintered magnets by Sagawa[8].Nanocrys-talline structures can also be synthesised by mechanical *Corresponding author.Tel.:+49-351-4659-664;fax+49-351-4659-781.E-mail address:o.gutﬂeisch@ifw-dresden.de(O.Gutﬂeisch).0304-8853/02/$-see front matter r2002Elsevier Science B.V.All rights reserved.PII:S0304-8853(01)00989-1alloying [9],intensive milling or hydrogenation dispro-portionation desorption and recombination (HDDR)processing [10,11].These nanostructures,provide energy barriers preserving the metastable,permanently magne-tised state.The resulting isotropic powders are most commonly used for the production of bonded magnets,where they are usually mixed with polymer resin and are then injection or compression moulded.Bonded mag-nets have the advantage of easily accomplished near net-shape processing,the avoidance of eddy-currents and good mechanical properties.The disadvantage being the dilution of magnetic properties due to the polymer binder.The randomly oriented grain structure results in magnetically isotropic magnets,with the remanent polarisation,J r ;and (BH )max limited to 0.5and 0.25,respectively,of the values obtainable for ideal micro-structures consisting of single domain grains and with full crystallographic alignment.Therefore various con-cepts have to be developed in order to increase remanence as shown in Fig.1.The three most relevant ways of maximising the energy density (BH )max are hot deformation [12,13],inducement of texture via ‘aniso-tropic’HDDR [14]or thirdly,remanence enhancement via exchange coupling [3,4].In summary,the task of transferring good intrinsic properties such as high values of Curie temperature (T C >500K),high saturation magnetisation (M s >1T)and high anisotropy ﬁeld,H A into useful extrinsic properties of nanocrystalline magnets such as coercive ﬁeld H C ;remanent magnetisation B r and maximum energy density (BH )max by appropriate processing is described in this paper.2.Maximising the energy density (BH)max 2.1.High energy ball millingAs a non-equilibrium processing technique,mechan-ical alloying circumvents,like rapid quenching,many limitations of conventional alloying and thus can be used for the preparation of metastable alloys.The mixing of the elements is achieved by an interdiffusional reaction,enabled by the formation of ultraﬁne layered composite particles during high energy ball milling.Depending on the thermodynamics of the alloy system,energy input and the mechanical workability of the starting powders,the alloying can take place during milling or during a subsequent heat treatment [9].A variation of this high energy ball milling technique is intensive milling,where an alloy is exposed to high energy ball milling rather than the elemental powders.Here,an example is given for the intensive milling of a Pr–Fe–B-based alloy.Pr 2Fe 14B-type alloys are compar-able in terms of their intrinsic magnetic properties [15]and phase relations with the advantage of a much lower spin reorientation temperature.An alloy with the nominal composition Pr 9Nd 3Dy 1Fe 72Co 8B 6.9Zr 0.1has been milled for 60h (leading to a type II magnet)and also with various amounts of Fe powder (leading to type III magnets)and subsequently annealed at 6001C for 30min.The partly amorphous structure after milling is illustrated in Fig.2.The Curie-temperature of the alloy is T C ¼3801C.The magnetic properties of various annealed powders are shown in Fig.3.Optimised valued for (BH )max were above 175kJ/m 3when adding 20–25wt%Fe (B r ¼1:18T and i H c ¼0:66T).A key issueFig.1.Flow chart illustrating the principal processing routes of high energy density magnets based on micro-and nano-crystalline powders.The right branch shows the three principal ways of maximizing the energy product (BH )max of nanocrystalline magnets.O.Gutﬂeisch et al./Journal of Magnetism and Magnetic Materials 242–245(2002)1277–12831278for the effectiveness of the exchange coupling and thus the degree of remanence enhancement is the develop-ment of a uniform nanoscale microstructure of hard and soft magnetic grains.This can be realised by micro-alloying using additions such as Zr and Co having grain growth inhibiting effects [16,17]or leading to a modiﬁcation of the tie lines in the phase diagram and thus changed volume fractions of the different phases [18].An effective coupling occurs when the soft regions with a small anisotropy are no bigger than a few times the exchange length l ex ;i.e.o 20nm and thus a complete coupling of the soft magnetic grain occurs.The crystal-lite size of the annealed sample was evaluated from the broadening of the X-ray diffraction peaks (see Fig.3)using the Williamson-Hall method [19]and it was found to be around 20nm.Remanence enhanced high energy density magnets,synthesised by melt spinning or ball milling techniques,are of great commercial interest because no magnetic alignment and less of the costly rare earth element arerequired and an improved corrosion behaviour can be expected.2.2.Rapid quenchingCurrently,rapidly quenched Nd–Fe–B forms the basis for almost the entire bonded magnet industry.The ﬂexibility of bonded Nd–Fe–B-type magnets in proces-sing,shape and magnetic properties and the highly stable nature of the ribbons contribute to its success in a fast growing permanent magnet market [20–22].De-pending on the wheel speed,ejection conditions and melt temperature substantial undercooling below the equili-brium freezing temperature and,consequently,a very high frequency of crystal nucleation are achieved (‘‘over-quenching’’).Lower wheel speeds can lead directly to nano-crystalline material (‘‘direct-quenching’’).The inset of Fig.4shows the DSC curves on ﬁrst heating of melt-spun Nd 15DyFe 75.9B 8Zr 0.1and Pr 15Dy-Fe 75.9B 8Zr 0.1alloys.XRD patterns of both melt-spun materials showed a partly amorphous structure which explains the presence of a second order thermodynamic phase transition around 3101C and 2951C,respectively,during ﬁrst heating corresponding to the Curie-tem-perature of the remaining R 2Fe 14B phase.A comparison of the onset of crystallization of both alloys prepared by this technique and by intensive milling showed lower values in the case of the latter method:5801C for the Nd-based alloy and 5301C for the Pr-based alloy whereas values of 6001C and 5751C,respectively,were obtained when using melt-spinning [23].Annealing of the melt-spun alloys at 6501C leads to the com-plete formation of the R 2Fe 14B phase achieving coerciv-ities as high as 2.7T for PrDyFeBZr and 2.37T for3035404550556065707580••600˚Cafter millingi n t e n s i t y (a .u .)2 theta (degree)Fig.2.XRD patterns of Pr 9Nd 3Dy 1Fe 72Co 8B 6.9Zr 0.1after 60h of intensive milling in argon and after annealing at 6001C for 30min.Intensity peaks of a –Fe ( )are indicated.-1.5-1.0-0.50.00.51.01.5P o l a r i s a t i o n J ( T )Applied field µ0H ( T )Fig.3.Hysteresis loops of intensively milled (with various amounts of Fe)and annealed Pr 9Nd 3Dy 1Fe 72Co 8B 6.9Zr 0.1.P o l a r i s a t i o n J ( T )Applied field µ0H ( T )Fig.4.Demagnetisation curves of melt-spun NdDyFeBZr and PrDyFeBZr materials annealed at 6501C for 10min (inset:DSC curves on ﬁrst heating (40K/min)of melt-spun NdDyFeBZr and PrDyFeBZr showing Curie temperature,T C ;and crystal-lization onset,T x ).O.Gutﬂeisch et al./Journal of Magnetism and Magnetic Materials 242–245(2002)1277–12831279NdDyFeBZr (see Fig.4).The room temperature aniso-tropy ﬁeld of Pr 2Fe 14B is around 25%larger than of its Nd counterpart,and the saturation magnetisation is only slightly lower.Melt-spun precipitation hardened Sm 2(Co,Cu,-Fe,Zr)17magnets have been produced using single roller melt-spinning at low velocity and their magnetic proper-ties in the as-spun state and after hardening are shown in Fig.5.Coercivity is developed only during the complex annealing treatment leading to the formation of a cellular structure (see inset in Fig.5)similar to that in sintered 2:17-type magnets.However,the resulting powder in this case is isotropic.It has been found that this type of material can show an abnormal temperature dependence of the coercivity [24]leading to excellent high temperature magnetic properties also reported for sintered magnets [25,26].Another interesting aspect is the production of magnetically anisotropic SmCo 5-type ribbons also using low wheel speeds [27]and a (BH )max of 146kJ/m 3was obtained for Sm 1.1Co 5[28].The c -axis of the crystallites after direct-quenching were found to be parallel to the longitudinal axis of the ribbon.This phenomenon is shown here for various Sm 2(Co)17-type alloys with the successive addition of Fe,Zr and Cu.XRD patterns of Fig.6show that the degree of texture decreases when adding Zr and Cu.This is illustrated by the weaker (110)and (200)and stronger (111)and (002)peaks for the Sm 2(Co,Cu,Fe,Zr)17alloy.2.3.Hydrogen assisted processingThe HDDR process is established as a processing technique for the production of highly coercive Nd 2Fe 14B [10,11]and Sm 2Fe 17N y magnets [29,30].A special type of powder suitable for bonded magnets is the anisotropic powder made by HDDR [14]which could close the gap in the market for high energyproduct bonded magnets.Very recently,excellent magnetic values of B r ¼1:38T,i H c ¼1122kA/m and (BH )max =342kJ/m 3have been obtained for NdFe-GaNbB using a process which controls the reaction rates during exothermic hydrogen absorption (dispro-portionation)and endothermic desorption (recombina-tion)by pressure adjustments [31,32].This multistage HDDR process is beneﬁcial to optimise remanence and coercivity without expensive additions such as Co.Strictly,HDDR does not lead to nanoscale (usually deﬁned as o 100nm)material,as the ﬁnal product resulting from the reversible,hydrogen-induced chemi-cal reaction shows typical grain sizes of around 300nm.The disproportionated state is certainly nanoscale and it is this intermediate product which should clarify the mechanism of the inducement of texture.Various models have been suggested and they have been detailed in a recent review [33].Intermediate boride phases have been linked with the transfer of the original cast grain orientation to that of the recombined 2-14-1-type grains in both,NdFeCoGaB [34]and NdFeB [35]alloys.The HRSEM micrograph in Fig.7shows the solid-dispro-portionated state of a Nd 16.2Fe 78.2B 5.6alloy.The eutectoid-type decomposition into NdH 27x rods of appr.20nm and Fe and a build-up of ﬁnely dispersed Fe 3B particles of 10–50nm diameter in the intercolony regions due to an ejection of this phase from the rod-like areas can be observed.The principal solid-disproportionation reactions of the R 2Fe 14B (with R=Nd or Pr)phases can be described as follows:R 2Fe 14B þð27x ÞH 2)2RH 27x þ11Fe þFe 3B )2RH 27x þ12Fe þFe 2B :ð1ÞIn the case of a Pr 13.7Fe 63.5Co 16.7Zr 0.1B 6alloy a new intermediate boride phase,Pr(Fe,Co)12B 6(R3m),has been found recently after solid-disproportionation[36]Fig.5.Hysteresis loops of as-spun and precipitation hardened (T h =11601C,1h,T a =8501C,20h,cooling to 4001C with 0.75K/min)Sm(Co 0.74Cu 0.12Fe 0.1Zr 0.04)7.5(inset:TEM bright ﬁeld image of the latter).3035404550556065707580Sm 2Co 17Sm 2(Co 0.9Fe 0.1)17Sm 2(Co 0.86Fe 0.1Zr 0.04)17Sm 2(Co 0.74Fe 0.1Cu 0.12Zr 0.04)17(201)(002)(111)(110)(200)I n t e n s i t y (a .u .)2 theta (degree)Fig.6.XRD patterns of as-spun (using a low wheel speed)Sm 2(Co)17-type alloys with the successive addition of Fe,Zr and Cu.O.Gutﬂeisch et al./Journal of Magnetism and Magnetic Materials 242–245(2002)1277–12831280and a high degree of texture has also been reported for this type of alloys after conventional processing [37].The application of the HDDR process to the Nd–Co–B or Sm–Co systems requires more severe hydrogena-tion conditions which is due to the higher thermo-dynamic stability of the R–Co phases against the disproportionation by hydrogen compared to those of the Nd 2Fe 14B and Sm 2Fe 17phases.Recently,it was shown that HDDR in thermodynamically stabilised compounds such as Sm 2Fe 16Ga,SmCo 5,Sm 2Co 17and Nd 2Co 14B is successful when using high hydrogen pressures [38]or reactive milling in hydrogen [39].In case of Sm 2Co 17,the latter mechanically activated gas-solid reaction leads to the disproportionation of the rhombohedral 2:17phase into Sm-hydride and FCC Co according to the following equation:Sm 2Co 17þð27x ÞH 232SmH 27x þ17Co :ð2ÞIntimate mixtures of R-hydride with grain sizes o 10nm and BCC Fe or FCC Co are obtained after reactive milling which is not possible when applying the conventional HDDR process [33].For SmCo-type alloys,the following desorption treatment at tempera-tures as low as 5001C leads to the recombination to the original structure either of CaCu 5and Th 2Zn 17type.In dependence on Sm content,milling parameters and desorption temperature additional phases are synthe-sised,partly of metastable character,such as the Sm 2Co 7phase.The recombined multiphase material exhibits grain sizes of the scale o 30nm (compare Fig.8)which makes an effective exchange coupling and thus rema-nence enhancement possible.Magnetically single phase demagnetisation loops are observed and a clear tendency of increased coercivity and decreased reman-cence with increasing Sm content is found [40].2.4.Hot deformationHot deformation-induced texturing of nano-grained materials is an option for producing fully dense,anisotropic magnets with maximised energy densities.A grain alignment along the c -axis of the tetragonal 2:14:1phase based on either Nd–Fe–B or Pr–Fe–B alloys perpendicular to the plastic ﬂow is achieved after high temperature compressive deformation [12,13].The production of a fully dense isotropic precursor at about 7251C is followed by placing this compact in an oversized die-cavity where die-upsetting is carried out at similar temperatures.After this second step,an anisotropic magnet is obtained with the alignment of the crystallographic c -axis parallel to the pressing direction.Alternatively,backward extrusion [41]can be carried out as a second step to produce near net-shape ring magnets which can show,especially for smaller dimensions,superior magnetic properties to sintered magnets.A radial preferential orientation is obtained,again with the c -axis alignment perpendicular to the material ﬂow.Small variations in the magnetic properties have been observed along the cross-section and along the axial direction of the ring magnets which were attributed to inhomogeneities in material ﬂow inherent to the deformation process [42].Additions of Co are used to improve the thermal stability and to increase the Curie-temperature in sintered NdFeB magnets.Simultaneously the coercivity is reduced,which again can be compensated by small additions of Ga.The same positive effect of Co and Ga was found in hot deformed NdFeB magnets,prepared from melt-spun material (MQU-F).The addition of Ga decreases melting point and viscosity of the Nd-rich grain boundary phase.This accelerates mass transfer through the liquid and improves the isolation of the grains leading to enhanced coercivities.TEM-EDX analysis showed a preferential solution of Ga intotheFig.8.TEM bright ﬁeld image of reactively milled and recombined Sm 2Co 17powder.Fig.7.Scanning electron microscopy image in the backscat-tered mode showing the rod-like structure of NdH 27x (A)and a –Fe (B)and ﬁnely dispersed Fe 3B (C)obtained after 15min of solid-disproportionation at 9001C.O.Gutﬂeisch et al./Journal of Magnetism and Magnetic Materials 242–245(2002)1277–12831281Nd-rich grain boundary phase,now a neodymium–iron–gallium phase.Ga reduces the surface energy of this phase resulting in smoothed grain boundaries and a more uniform distribution [43].Thus,lower deformation forces are required for hot deformation and higher B r material can be produced because of an increased volume fraction of the hard magnetic 2:14:1phase with a commensurate reduction in the non-ferromagnetic grain boundary material.Demagnetisation curves of hot pressed and die-upset melt-spun NdFeB-type powders are shown in Fig.9.As a comparison,hot pressed and die-upset intensively milled Pr 14.7Fe 77.3B 8.0powder is also included.The already mentioned much lower spin reorientation temperature make them attractive for low temperature applications such as superconducting bearings.Opti-mised deformation conditions were used for the production of MQ-type magnets [43]and remarkably higher coercivities were found in hot pressed and in hot deformed MQU-F magnets.A reduction in coercivity after die-upsetting can be observed which amounts to 25%in MQU-F magnets and to 40%in MQP-A.The higher coercivity in MQU-F magnets is due to the beneﬁcial effect of the additives resulting in smaller grains after hot deformation.A remanence of B r ¼1:3T and a (BH )max =326kJ/m 3were measured for the MQU-F die-upset magnet.The loop shape ((BH )max =307kJ/m 3)and the hot workability of the Pr 14.7Fe 77.3B 8.0die-upset magnet made from intensively milled powder are excellent and it can be expected that compositional modiﬁcations will improve the magnetic properties further.3.ConclusionsNowadays about 85%of the limit for the energy density (BH )max (based on the Nd 2Fe 14B phase)can beachieved in commercially produced sintered Nd–Fe–B grades [44,45].Coercivity values 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中国团队成功研发提取外泌体的新型片上磁性提取系统

中国团队成功研发提取外泌体的新型片上磁性提取系统外泌体是平均大小约为200 nm 的脂质双层纳米级膜颗粒，由许多细胞类型分泌。

外泌体在认知药物给药和液体活检领域显示出巨大的潜力，因为它们具有天然产生的成分，并通过转移和递送生物分子作为细胞间通讯工具。

Image Credit: / Meletios Verras外泌体的大小为纳米级（30-200 nm），它们的浮力密度很低，因此很难将它们与复杂的生物体液分离。

近日，中科院深圳先进技术研究院（SIAT）杨辉教授的研究团队在中国科学院深圳先进技术研究院（SIAT）的指导下，研发了一种无标记且具有生物相容性的片上磁分离系统，用于有效提取外泌体。

基于负磁泳的思想，研究人员在这项研究中构建了一种无标记的片上磁分离装置。

该系统的核心部件是一个具有极高梯度磁场的磁性模块，由片上磁极阵列、对称分布的永磁体和具有高磁导率的永磁合金组成。

该装置可以在微流控通道中产生超高的磁场梯度，用于基于磁性模块的样品提取。

因此，可以收集非常微小（以纳米为单位）的生物样本，并且现有方法显着增强了区分不同大小样本的能力。

通过使用片上磁极阵列，微通道中的磁场梯度急剧增加。

因此，利用极低浓度的铁磁流体实现了纳米尺寸分辨率的片上负磁泳分离。

在低浓度的铁磁流体中，生物样品的活力大大提高。

|小囊泡(sEV) 与许多疾病密切相关，因为它们携带各种生物标志物。

从复杂的生物样本中有效分离sEV 是后续治疗和进一步疾病诊断的必要条件和先决条件。

在这里，研究人员提出了一种无标记且生物相容的片上磁分离系统，用于从细胞培养上清液中高效提取sEV。

通过片上超高梯度磁场模块，在分离微通道内部产生接近100 000 T m-1的磁场梯度。

通过使用 200 nm 和 1000 nm 的荧光粒子模拟复杂样品中的sEV 和其他生物粒子，优化了系统设计和实验参数。

流式细胞仪和提出的荧光强度分析方法均验证了200 nm颗粒的回收率和纯度分别可以达到84.91%和98.02%。

纳米粉末样品制备方法对扫描电镜成像的影响

纳米粉末样品制备方法对扫描电镜成像的影响周丽花【摘要】The preparation of well dispersed SEM samples is significantly important to the observation for the accurate morphology and particle sizes of nano-powder. In this study, conductive platinum and non-conductive yttrium vanadate were chosen as study objects. Direct-fixing method and the fixing method using copper mesh with carbon supporting film were used to prepare SEM samples, respectively. The influences of the two methods on the observation results of SEM were investigated. The results showed that the fixing method using copper mesh with carbon supporting film can effectively improve the dispersion of nano-powders, and eliminate the possibility of the occurrence of fusion between nano-particles and conductive adhesive. It enables the accessibility to true SEM image of nano -powders, and improves the accuracy and the efficiency of SEM measurement.%制备出分散良好的电镜样品对准确观察纳米粉末的形貌和尺寸尤为重要.以导电类铂和不导电类钒酸钇纳米粉末为研究对象,分别采用直接固定法和铜网碳载膜固定法制备样品,并对比这两种方法对扫描电镜成像的影响.结果表明:采用铜网碳载膜固定制备法可以有效改善纳米粉末样品的分散性,杜绝纳米颗粒与导电胶发生溶合,易获得纳米粉末样品扫描电镜真实像,明显提高扫描电镜观察的准确性和检测效率.【期刊名称】《中国测试》【年(卷),期】2012(038)005【总页数】4页(P15-17,21)【关键词】纳米粉末;扫描电镜;铜网碳载膜;直接固定法;准确性【作者】周丽花【作者单位】中国科学院福建物质结构研究所,福建福州350002【正文语种】中文【中图分类】TB92;TH742.9;TM930.12;O641.10 引言众所周知，纳米材料的性能与其微结构（如表面形貌、尺寸等）密切相关[1-5]，因此对纳米材料的微结构进行有效观察是研究其构效关系的前提条件之一。

Annealing temperature effect on microstructure, magnetic and microwave

Annealing temperature effect on microstructure,magnetic and microwave properties of Fe-based amorphous alloy powdersJinghua He,Wei Wang,Aimin Wang,Jianguo Guan nState Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology,Wuhan430070,PR Chinaa r t i c l e i n f oArticle history:Received12November2011Received in revised form18April2012Available online5May2012Keywords:Fe-based amorphous alloyAnnealingMagnetic propertyMicrowave absorbing propertyNanocrystalline particlea b s t r a c tFe74Ni3Si13Cr6W4amorphous alloy powders were annealed at different temperature(T)for1.5h tofabricate the corresponding amorphous and nanocrystalline powders.The inﬂuences of T on thecrystalline structure,morphology,magnetic and microwave electromagnetic properties of the resultantsamples were investigated via X-ray diffraction,scanning electron microscopy,vibrating samplemagnetometer and vector network analyzer.The results show that the powder samples obtained atT of6501C or more are composed of lots of ultra-ﬁne a-Fe(Si)grains embedded in an amorphousmatrix.When T increases from350to7501C,the saturated magnetization and coercivity of theas-annealed powder samples both increase monotonously whereas the relative real permittivity showsa minimal value and the relative real permeability shows a maximal value at T of6501C.Thus thepowder samples annealed at6501C show optimal reﬂection loss underÀ10dB in the whole C-band.These results here suggest that the annealing heat treatment of Fe-based amorphous alloy is aneffective approach to fabricate high performance microwave absorber with reasonable permittivity andlarge permeability simultaneously via adjusting T.&2012Elsevier B.V.All rights reserved.1.IntroductionWith the expansion of electronic devices and satellite commu-nication devices,a large number of harmful electromagnetic(EM)signals in the frequency range of C-band(3.95–5.85GHz)radiate inour surroundings,resulting in the occurrence of serious electro-magnetic interference(EMI)problems.This has led to a search forsuitable EM wave absorption materials which can restrain EMI.Asone of the good candidates of EM wave absorption materials,magnetic metals such as iron powders show remarkable advantagesof high saturation magnetization(M s),high Curie temperature,andlarge magnetic permeability(m r)[1–5],but the permeability of themat microwave frequencies decreases drastically because of the eddycurrent effect resulting from their high conductivity.In order tosuppress the eddy-current effect,some surface-modiﬁcation meth-ods for the magnetic metal particles,including surface passivation[6–8],insulating materials coating and compounding[9–13],havebeen developed.However,surface modiﬁcation can only effectivelyprevent the electronic conduction between metal particles,butcannot radically eliminate the eddy current effect within the interiorof single metal particle.Therefore,it is of signiﬁcance to explore analternative to restrain the eddy current effect within the magneticmetal powders.Recently,iron-based amorphous alloys have attracted technolo-gical and scientiﬁc interests as they exhibit some obvious merits ofexcellent soft magnetic properties(e.g.high m r and M s),highelectrical resistivity,small eddy current losses,high hardness andstiffness etc.due to the absence of magnetocrystalline anisotropyand grain boundaries[14–16].Furthermore,the Fe-based amor-phous alloy precursors can be readily transformed by an appropriateheat treatment into Fe-based amorphous and nanocrystalline alloymaterials with an unique microstructure of nanocrystalline a-Fe(Si)grains embedded in an amorphous matrix,which may exhibit moreexcellent magnetic properties,depending on the magnetic exchangecoupling between the grains through the amorphous boundaries[17].This suggests that the iron-based amorphous alloys possiblybecome one of the most promising candidates for many engineeringapplications[18].In this paper,amorphous alloy powders of Fe74Ni3Si13Cr6W4with an ellipsoidal shape were annealed at various temperatures(T).The structures,magnetic and microwave properties of theas-prepared samples have been investigated as functions of T.Theresults indicate that annealing the Fe-based amorphous alloypowders at6501C leads to optimal introduction of grain bound-aries and ultraﬁne nanocrystalline grains in the powders,andendows them with enhanced M s and m r,decreased permittivity.Their-based single-layer composites show excellent reﬂective lossContents lists available at SciVerse ScienceDirectjournal homepage:/locate/jmmmJournal of Magnetism and Magnetic Materials0304-8853/$-see front matter&2012Elsevier B.V.All rights reserved./10.1016/j.jmmm.2012.04.036n Corresponding author.Tel.:þ862787218832;fax:þ862787879468.E-mail address:guanjg@(J.Guan).Journal of Magnetism and Magnetic Materials324(2012)2902–2906in the whole frequency range of3.95–5.85GHz.The annealing treatment of Fe-based amorphous alloy powders reported here provides an effective method to suppress the eddy current effect. The as-prepared Fe-based amorphous and nanocrystalline alloy powders can effectively absorb the C-band electromagnetic wave.2.ExperimentsThe Fe-based amorphous alloy powders(as-cast)used here had a nominal composition of Fe74Ni3Si13Cr6W4and were prepared by gas atomization method.The amorphous and nanocrystalline alloy pow-ders with different structures were obtained by annealing the above Fe-based amorphous alloy powders at different temperatures ranging from3501C to7501C for 1.5h under nitrogen atmosphere.The differentiation scanning calorimeter(DSC)analysis of the as-cast amorphous alloy powders was conducted on a NETZSEC STA-449C Thermal Analyzer(Germany)at a heating rate of10K/min in ultrapure argon gas.The X-ray diffraction(XRD)patterns were obtained by using a Rigaku D/max-IIIA diffractometer(Japan)at a voltage of40kV and a current of200mA with Cu-K a radiation (l¼1.5406˚A),in the2y range from20to901at a scanning step of 0.021.Scanning Electron Microscopy(SEM)images were obtained using a Hitachi S-4800Field-emission SEM(Japan).The magnetic hysteresis loops were measured by a Model-4HF vibrating sample magnetometer(VSM,ADE Co.Ltd.,USA)with a maximum magnetic ﬁeld of15kOe at room temperature.The complex dielectric permit-tivity(e r¼e0Àj e00)and complex permeability(m r¼m0Àj m00)were obtained using an Agilent N5230vector network analyzer in the frequency range3.95–5.85GHz.The composite samples were pre-pared by completely mixing30%volume concentration of the as-cast or annealed powder samples with parafﬁn wax,and then pressed into a toroidal shape with an outer diameter of7mm,an inner diameter of3.04mm,and a length of$3mm for microwave measurement.3.Results and discussionFig.1shows the typical DSC curve for the as-cast Fe-based amorphous alloy powders.It can be seen that the as-cast Fe-based amorphous alloy powders show three main exothermic peaks in their DSC curve.This is similar to the previous reports in the amorphous ribbons[19–21].Theﬁrst peak at about6401C is reasonably attributed to the formation of the primary nanocrystalline a-Fe(Si)soft magnetic phase.The second and third peaks at approximately 6921C and7801C both are possibly related to the further crystal-lization of the remaining amorphous phase,or to the phase transformation of the existing metastable phases,following the primary crystallization.Furthermore,it is worth noting that the intensity of the heatﬂow increases gradually when T increases from 1001C to the primary crystallization temperature,implying that the samples annealed at T lower than the primary crystallization temperature may form a very small quantity of the nanocrystalline a-Fe(Si)phase.This is different from the results of the Fe-based amorphous ribbons[21–23],whose intensity of the heatﬂow remains almost constant in the same heating process.Based on the DSC results,the as-cast Fe-based amorphous alloy powders were annealed at different T ranging between350and7501C for1.5h in nitrogen atmosphere in order to achieve the nanocrystalline a-Fe(Si) phase.Fig.2shows the XRD patterns of the as-cast and annealed Fe-based amorphous alloy powders at different T.It is clear that the as-cast amorphous alloy powders exhibit only one broad and weak peak around2y¼451in their XRD pattern,indicating that they are amorphous.However,for the annealed amorphous alloy powders,the intensity of the a-Fe(Si)(100)diffraction peaks increase gradually as T increases from350to6501C.This suggests that the mean grain size of the annealed samples increases gradually with increasing T.This case is different from that of the reported annealed Fe-based amorphous ribbons,whose mean grain size remains almost constant until T reaches the primary crystallization temperature of5401C[22].This implies that a trace amount of ultraﬁne nanocrystalline a-Fe(Si)grains are formed below the primary crystallization temperature.Besides the a-Fe(Si)diffraction peaks,no impurity phase in the samples annealed at r6501C is detectable by the XRD patterns.When T increases up to7501C,some week peaks corresponding to the CrW(Fe,Ni)phase are present in the as-annealed powders.This may be attributed to the further crystallization of the remained amorphous matrix,and is consistent with the above DSC results. In terms of Scherrer’s equation,the crystalline sizes of the samples annealed at6501C and7501C are calculated to be approximately13nm and30nm,respectively.The SEM images of the samples annealed at various T are shown in Fig.3.One can see that the as-cast particles have an ellipsoidal shape with an almost smooth surface besidessome Fig.1.DSC curve for the as-cast Fe74Ni3Si13Cr6W4amorphous alloypowders.Fig.2.XRD patterns of the as-cast and annealed amorphous alloy powders atdifferent T for1.5h.J.He et al./Journal of Magnetism and Magnetic Materials324(2012)2902–29062903tiny crumbs attached.The average particle size is about 12m m.The shape and particle size hardly change as T increases from 350to 5501C,while a great number of a -Fe(Si)nano-grains of typically 10–15nm are observed in the surfaces when T increases up to 6501C.As T increases up to 7501C,the grain size enhances obviously.This further proves that the powder samples annealed at 6501C are composed of lots of ultra-ﬁne a -Fe(Si)grains embedded in an amorphous matrix,and a lot of the grain bound-aries also exist in the as-annealed Fe-based powders.During the heat treatment process the particle size is almost independent of T .These results are in good agreement with the results of the DSC and XRD measurements.Similar phenomena were also observed in the previous reports [24,25].The magnetic properties are sensitive to the structural and compositional changes during the annealing process.Fig.4shows the magnetic hysteresis loops of the as-cast and annealed amor-phous alloy powders at room-temperature.It is evident that M s monotonously increases from 78to 101emu/g with T increasing from 350to 7501C.This can be attributed to the growth of the ultraﬁne a -Fe(Si)nanocrystalline with high M s in the amorphous matrix.As shown in the inset of Fig.4,the coercivities (H c )of the samples annealed at lower than 6501C almost keep unaltered.Further increasing T ,H c ﬁrst increases slightly at T of 6501C,then increases greatly at T of 7501C.These behaviors can be well explained in terms of the grain size dependence of H c [17].It is noticed that compared with the as-cast amorphous alloy powders,the powder samples annealed at 6501C show a slightly increased H c but a substantially enhanced M s .This suggests that the as-annealed Fe-based alloy powders possess excellent soft magnetic properties because of the formation of nanocrystalline phase with grain size much smaller than the ferromagnetic exchange length [26].Hence,Fig.3.SEM images of the as-cast and annealed amorphous alloy powders at different T for 1.5h.Fig. 4.Typical hysteresis loops of the amorphous alloy powders annealed at different T .The inset is an enlarged part near the central region of the loops.J.He et al./Journal of Magnetism and Magnetic Materials 324(2012)2902–29062904the as-annealed amorphous alloy powders can become promising as microwave absorbers.In order to determine the microwave absorbing properties of the as-annealed amorphous alloy powders,we have investigated the electromagnetic parameters of the parafﬁn wax-based com-posites containing 30%volume concentration of the as-annealed powder samples in the frequency range of 3.95–5.85GHz.Fig.5(a)and (b)shows that with increasing T from 350to 6501C the real part (e 0)and imaginary part (e 00)of the complex permittivity of the as-annealed powders both decrease.As the particle size and morphology of the as-annealed powders are almost independent of T ,the reduced complex permittivity can be ascribed to the appearance of the grain boundaries,which reduce space charge polarization and lead to electron scattering.Fig.5(c)and (d)indicates that with increasing T ,the real part (m 0)of the complex permeability increases while the imaginary part (m 00)decreases for the as-annealed powder samples.The former further suggests that nanocrystalline particles with a long-range order can enhance the magnetic coupling,and thus M s .In contrast,the latter can be ascribed to the stronger natural exchange resonance at higher frequency because of the occur-rence of the a -Fe(Si)nanocrystalline particles.In addition,when T increases up to 7501C,e 0and e 00begin to increase while m 0and m 00begin to decrease.This is because with T further increasing from 6501C to 7501C,the grain size signiﬁcantly grows and the number of the grain boundaries decreases,leading to the decrease of e 0and e 00.It suggests that the concentration of the grain boundaries can be used to adjust the permittivity.As a result,both m 0and m 00also begin to decrease due to the enhancement of the eddy current effect,which restrains the ingress of the EM wave.The above results clearly indicate that the in-situ formation of the nanograins and grain boundaries in the as-cast Fe-basedamorphous alloy powders via annealing heat treatment not only can enhance the magnetic permeability,but also can decrease the permittivity.Selecting an appropriate T may realize impedance match and improve the microwave absorbing property.According to the transmission line theory,the reﬂection loss (RL )of a single-layered absorbing material backed a conductor can be calculated using the relative complex permeability (m r )and permittivity (e r )at a given frequency (f )and thickness (d )[27]RL ðdB Þ¼20log 9ðz in À1Þ=ðz in þ1Þ9ð1Þz in ¼ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃm r =e r q tan h j ð2p =c Þﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃm r =e r q f dð2Þwhere c is the speed of light.Fig.6shows the RL curves for the 2.0mm thickness of single-layered composites consisting of 30vol%of the powder samples annealed at different T .One can see that RL depends sensitively on T.As T increases from room temperature to 6501C,the frequency corresponding to the attenuation peak (f min )shifts toward a high frequency from 3.95to 4.95GHz and the minimal RL decreases gradually.The composite containing the powders annealed at 6501C shows an excellent absorption with a minimal RL of À18.65dB at 4.95GHz due to its highest m 0and its lowest e 0.However,for the composites containing the powder samples annealed at T of 7501C,the minimal RL begins to increase slightly and f min shifts to a low frequency of 4.73GHz.The RL for the composites containing the alloy powders annealed at T ¼550,650and 7501C are all under À10dB in the whole C-band,suggesting that the as-annealed powder samples have a promising application in absorbing materials especially for microwaves of pared with the previously reported modiﬁcation methods of the magnetic metal particles,such as surface passivation [6–8],surfacecoatingFig.5.(a)Real part (e 0)and (b)imaginary part (e 00)of complex permittivity,and (c)real part (m 0)and (d)imaginary part (m 00)of complex permeability of the parafﬁn wax-based composites containing amorphous alloy powders annealed at different T in the frequency range 3.95–5.85GHz.J.He et al./Journal of Magnetism and Magnetic Materials 324(2012)2902–29062905and composites with insulating materials [9–13]which usually reduces the permittivity and the permeability at the same time,the annealing heat treatment of Fe-based amorphous alloy not only can decrease the permittivity substantially,but also can increase the permeability simultaneously.Thus the composites containing the as-annealed powder samples with large perme-ability and small permittivity can steadily meet the requirement of impedance matching,and exhibit excellent microwave absorb-ing properties.4.ConclusionsThe Fe-based amorphous and nanocrystalline alloy powders composed of ultra-ﬁne a -Fe(Si)nanograins embedded in an amorphous matrix,which exhibit reasonable electromagnetic parameters,can be obtained by annealing amorphous alloy powders with a nominal composition of Fe 74Ni 3Si 13Cr 6W 4pre-pared by gas atomization method at an appropriate temperature,such as 6501C.With the annealing temperature increasing from 3501C to 7501C,M s and H c of the as-annealed alloy powders both increase monotonously whereas e 0shows a minimum value and m 0shows a maximum value at T ¼6501C.The 2mm thickness of single-layered composites containing the alloy powders annealed at T ¼550,650and 7501C all show RL under À10dB in the whole C-band.All these phenomena are reasonably explained by the fact that in the as-annealed amorphous alloy powder,the a -Fe(Si)nanograins are well separated by the grain boundaries with large resistance,which can effectively eliminate the eddy effect and improve the magnetic permeability at microwave frequency dueto the existence of the exchange coupling between the ultra-ﬁne grains.AcknowledgmentsThis work described here was ﬁnancially supported by New Century Excellent Talents (no.NCET-05-0660)from the Ministry of Education,China Postdoctoral Science Fund (20100480886),University Industry Cooperation project (guangdong ﬁnancial education [2011]362)from guangdong province and Fundamen-tal Research Funds for the Central Universities (2011-IV-059).References[1]S.Yoshida,M.Sato,E.Sugawara,Y.Shimada,Journal of Applied 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磁性分子印迹聚合物最新进展

磁性分子印迹聚合物最新进展卫泽辉;牟丽娜【摘要】Magnetic nanoparticles (MNPs) because of their attractive properties such as small size, high surface-to-volume ratio, high magnetic susceptibility and effective ability for binding have been used in various fields. MNPs can be easily and effectively separated with an external magnetic field without any additional centrifugation or filtration procedures, and surface molecular imprinted polymers (MIPs) have high selective and effective recognition for template molecule. The combination of the two technologies has become a research hot spot for solid phase extraction. This review focused on the preparations and applications in the field of magnetic molecular imprinted polymer in recent years.%磁性纳米颗粒因其具有粒径小、比表面积大、磁化率高、键合力强等优点而被广泛的应用到多种领域。

磁性纳米颗粒仅在外加磁场作用下就可实现高效分离，无需离心和过滤，而表面分子印迹聚合物具有高度识别特性，两种技术的结合成为近期分子印迹聚合物应用到固相萃取中的研究热点。

关于磁流体PEG coating Fe3O4 nanoparticles(30nm)纳米材料

关于磁流体PEG coating Fe3O4 nanoparticles（30nm）纳米材料今天小编瑞禧RL整理并分享关于磁流体PEG coating Fe3O4 nanoparticles（30nm）纳米材料简介:四氧化三铁（Fe3O4）可以作为一种磁流体。

Fe3O4是一种具有磁性的磁性材料，由铁（Fe）和氧（O）元素组成。

它具有良好的磁性响应，可以在外部磁场的作用下产生明显的磁化，使得整个材料呈现磁性。

磁流体（Magnetic Fluid）是一种微米至纳米级别的颗粒悬浮在液体介质中，具有磁性的复合材料。

这种特殊的液体由磁性颗粒和分散剂（通常是液体）组成，其中磁性颗粒可以是铁、镍、钴等磁性材料的纳米颗粒。

这些磁性颗粒在外部磁场的作用下，可以产生磁性响应，表现出磁性特性。

磁流体具有以下特点和应用：特点：磁性响应：磁流体中的颗粒在外部磁场作用下会发生磁化，使得整个液体呈现出磁性。

可控性：磁流体的磁性响应可以通过改变外部磁场的强度来控制，实现对液体的精准操作。

分散性：磁流体的颗粒通常具有良好的分散性，这使得它们在液体介质中能够均匀分布。

稳定性：磁流体在合适的分散剂中可以保持稳定分散状态，不易发生沉淀。

应用领域：磁性流体密封：由于磁流体可以被外部磁场控制，因此被广用于制造磁性密封，例如在机械设备中，用于密封液体或气体，替代传统的机械密封。

磁性制动器和减震器：磁流体可以用于制造磁性制动器和减震器，通过调整磁场的强度，实现制动和减震的功能。

磁共振成像（MRI）对比剂：磁流体被用作MRI对比剂，用于提高MRI图像的对比度。

声波和光学装置中的振动控制：磁流体也被用于声波和光学装置中的振动控制，通过外部磁场调节磁流体的粘性和流动性，实现振动的控制。

以上来源于文献整理，如有侵权，请联系删除，RL2023.10。

氮化硅微纳米粉制备的新进展

第46卷第2期氮化硅微纳米粉制备的新进展唐艳东马北越(东北大学冶金学院，沈阳110819)摘要：介绍了氮化硅材料的特点及其在生产中的应用,综述了氮化硅微粉的特性与制备研究进展，并特别关注了氮化硅微纳米粉的研究。

对当前氮化硅微纳米粉合成的研究思路进行了一定的剖析与总结，并展望了其未来发展方向。

关键词:氮化硅；微粉；纳米粉；研究进展中图分类号：TQ175.61文献标识码：A文章编号：1673-7792(2021)02-0009-06 Development on preparation of silicon nitride micro-nano powders Tang Yandong Ma Beiyue(School of Metallurgy,Northeastem University袁Shenyang110819袁China)Abstract:In t his paper,the characteristics and application in the production of silicon nitride materials are introduced袁the latest research development about the characteristics and preparation of silicon nitride micro powder are reviewed.Moreover袁the research work of silicon nitride micro-nano powder has been paid special attention.The current research ideas of silicon nitride micro-nano powders are analyzed and summarized袁and the future development trends are prospected.Key words:Silicon nitride；Micro powder；Nano-powder；Research development氮化硅是综合性能优异的结构陶瓷材料，其硬度大，耐磨性好,耐热和抗腐蚀性能良好，且具有优异的抗热震性、抗氧化性以及化学稳定性,高温蠕变小,热膨胀系数小,被广泛应用在冶金、航空航天、电子信息、化工机械以及半导体等行业［|-4］遥自然界中含有大量的氮元素和硅元素,原料价格低廉,容易获取。

清华大学科技成果——功能性纳米脂质体美容化妆品

清华大学科技成果——功能性纳米脂质体美容化妆品成果简介纳米脂质体美容化妆品技术是国际美容化妆品界追求的目标，是世界化妆品未来重要发展方向。

目前此领域主要是法国、德国和美国处于领先地位，多为高端奢侈产品，价格十分昂贵。

清华大学将现代生物医药技术成果与先进纳米脂质体工业化技术结合，成功研制系列功能性纳米脂质体美容化妆品，将有力推动和促进我国相关技术产业经济的发展。

本技术及其相关应用在国家“十一五”期间，已获得“重大新药创制”重大专项、“973”和“863”计划生物医药领域立项资助，并已获得国家发明专利授权。

应用说明具有较高美容价值的功能性药物或营养成分很多，如中草药有效成份提取物、化学/生化药物、维生素类和动植物油类等，具有很好的美容功效（如抗氧化、美白滋养、祛斑等），这些功效成份绝大多数为难溶性物质，使用时难以透过皮肤屏障发挥其功效作用。

我们采用生理相容性好、安全性高的卵磷脂为载体材料，利用现代纳米脂质体技术将这些难溶性功效物质制成粒度小于50nm的纳米脂质体微囊，能够携带药物自然穿透人体皮肤屏障，运输功效物质至真皮细胞层间形成营养储囊，从而使其功效性充分发挥成为现实。

重要代表性应用实例：1、辅酶Q10（生化药物）抗氧化/延缓衰老纳米脂质体系列辅酶Q10是人体细胞线粒体呼吸链合成ATP的关键作用酶，具有抗氧化，提高细胞活性和延长细胞周期的作用，是现代生命科学研究发现的一种重要参与调节细胞生理活性的难溶性物质。

辅酶Q10广泛存在人体各组织脏器组成细胞内，尤其以心脑部位含量最高。

人体细胞内辅酶Q10含量水平约在20岁时开始衰减，人体出现衰老现象，外源性的补充辅酶Q10，有助于细胞抗氧化、活性提高以及生存周期延长。

辅酶Q10纳米脂质体技术能够运送药物有效穿透皮肤屏障，大大提高药物吸收利用度为细胞维持重要生理活性提供有效物质基础，从细胞水平本质上提高促进人体细胞的活性，达到优良的抗氧化/延缓衰老功效作用。

详细介绍石墨烯英文版

Notes Best electrical conductor of any known metal
59.6 × 106
Commonly used in electrical wire applications due to very good conductivity and price compared to silver.
Introduction
Properties of graphene
Mechanical properties
- High Young’s modulus (~1,100 Gpa) High fracture strength (125 Gpa)
- Graphene is as the strongest material
Content
Introduction to graphene. Preparation and characterization graphene Potential application of graphene Conclusions
Introduction to graphene
Graphene is a one-atom-thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice The name ‘graphene’ comes from graphite + -ene = graphene
Molecular structure of graphene
High resolution transmission electron microscope images (TEM) of graphene