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

合集下载

热分析(结晶动力学)

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

化工专业英语词汇汇总

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

草酸钙的结晶动力学及不同种类羧酸盐的影响

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

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

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

Fe-B非晶合金的等温晶化动力学研究

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

反溶剂诱导结晶法英文

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

多晶型与添加剂之经典文献3

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

电石渣可控制备多晶型、多形貌纳米碳酸钙的研究进展

第52卷第4期2023年4月人㊀工㊀晶㊀体㊀学㊀报JOURNAL OF SYNTHETIC CRYSTALS Vol.52㊀No.4April,2023电石渣可控制备多晶型、多形貌纳米碳酸钙的研究进展丁㊀羽,张金才,王宝凤,郭彦霞,薛芳斌,程芳琴(山西大学资源与环境工程研究所,国家环境保护废弃资源高效利用重点实验室,太原㊀030006)摘要:碳酸钙有不同的晶体特征,使其在各个领域发挥不同的作用,对碳酸钙晶型㊁形貌和尺寸的控制是无机材料制备的研究热点㊂以电石渣为原料制备纳米碳酸钙能够实现变废为宝,是含钙固废综合利用的研究方向之一㊂因此在电石渣制备纳米碳酸钙过程中同步实现晶型㊁形貌的调控,能够将低附加值的电石渣固废转化为高附加值的纳米碳酸钙产品,具有良好的环境效应和经济效益㊂本文总结了电石渣制备纳米碳酸钙的方法,重点讨论了制备过程中晶型和形貌控制方面的研究进展㊂结果表明,在碳酸钙晶体成核和生长的过程中,控制工艺条件可以通过影响过饱和度进一步实现对晶型和形貌的调控,且不同种类的添加剂作用机理也不尽相同㊂热力学㊁动力学作为控制结晶各过程平衡的基础,可以用来解释各影响因素的作用机理㊂关键词:纳米碳酸钙;电石渣;晶型;形貌;可控制备;热力学;动力学中图分类号:TB321;TQ132.3+2㊀㊀文献标志码:A ㊀㊀文章编号:1000-985X (2023)04-0710-11Progress on Controllable Preparation of Polycrystalline and Polymorphic Nano Calcium Carbonate by Calcium Carbide SlagDING Yu ,ZHANG Jincai ,WANG Baofeng ,GUO Yanxia ,XUE Fangbin ,CHENG Fangqin (State Environmental Protection Key Laboratory of Efficient Utilization of Waste Resources,Institute of Resources and Environmental Engineering,Shanxi University,Taiyuan 030006,China)Abstract :Calcium carbonate has different crystal characteristics,which makes it play different roles in various application fields.The control of calcium carbonate crystal structure,morphology and size is a hot research topic in the preparation of inorganic materials.The preparation of nano calcium carbonate produced from calcium carbide slag can realize the transformation of waste into resource,which is one of the important research fields concerning the recycling of calcium-containing solid wastes.The controllable preparation of calcium carbonate with different crystalline structure and morphology from calcium carbide slag can make the worthless calcium carbide slag transform into high value-added nano grade products with good environmental and economic effects.The preparation methods of nano calcium carbonate from calcium carbide slag are summarized in this paper,the research progress of the control of crystal structure and morphology during the preparation process is discussed emphatically.The results indicate that,during the nucleation and growth of calcium carbonate crystals,controlling the process conditions can further achieve the regulation of crystal structure and morphology by influencing the degree of supersaturation,and the action mechanism varies from different kinds of additives.As the basis for controlling the equilibrium of the crystallization processes,thermodynamics and kinetics can be used to explain the mechanism of action of each influencing factor.Key words :nano calcium carbonate;calcium carbide slag;crystal structure;morphology;controllable preparation;thermodynamics;kinetics㊀㊀㊀收稿日期:2022-12-07㊀㊀基金项目:2022年度国家重点研发计划项目(2022YFB4102100)㊀㊀作者简介:丁㊀羽(1998 ),女,山东省人,硕士研究生㊂E-mail:2553646458@㊀㊀通信作者:张金才,副教授㊂E-mail:chaner9944@ 0㊀引㊀㊀言电石渣是生产聚氯乙烯的副产品,其主要成分Ca(OH)2含量在71%~95%,钙质含量高[1-4]㊂利用电石㊀第4期丁㊀羽等:电石渣可控制备多晶型㊁多形貌纳米碳酸钙的研究进展711㊀渣制备纳米碳酸钙,不仅可以吸收二氧化碳,减少碳排放,还能产生优质的纳米碳酸钙产品㊂在当前双碳目标的大背景下,发展该产业具有重要的现实意义㊂普通碳酸钙制造成本低,在我国产能和用量大,被广泛应用于各个行业中㊂涂料㊁造纸㊁塑料㊁橡胶等行业对高品质碳酸钙市场需求巨大,纳米碳酸钙作为性能优异的无机填料可以满足不同行业的使用要求[5]㊂当前我国纳米碳酸钙产品主要是石灰岩经过煅烧-消化-碳化-压滤-干燥-粉碎几道工艺步骤制成[6],产品性能好㊂该工艺中碳化利用的是煅烧释放的二氧化碳,实质上是实现了碳循环利用,并没有实现碳减排,还面临石灰岩开采带来的生态环境问题㊂在绿色㊁可持续发展的背景之下,以电石渣为原料生产纳米碳酸钙不仅能够消除固废资源堆积的环境隐患,还能获得应用广泛㊁附加值高的纳米碳酸钙产品,经济效益好[7]㊂电石渣制备纳米碳酸钙产业前景好㊁发展潜力大,但是当前在我国还没有实现大规模工业化生产㊂为尽快推进该产业的快速发展,本文广泛分析总结该领域的研究成果,综述了电石渣制备纳米碳酸钙产品的研究进展㊂从制备方法㊁晶体控制两方面展开论述,并对未来的发展趋势作出展望,期望能够对该产业的从业人员有所帮助㊂1㊀纳米碳酸钙的结构与性质碳酸钙主要有三种晶型,为方解石型㊁球霰石型㊁文石型,它们分别属于三方㊁六方和斜方晶系[8]㊂其中:方解石能量最低,热力学最稳定;球霰石能量最高,热力学最不稳定;文石介于方解石和球霰石之间㊂纳米碳酸钙颗粒的形貌主要受其内在晶体结构的影响,方解石型常以规则的菱面体存在,文石型以柱状㊁针簇状存在,球霰石型以球状聚集而成,图1为三种晶体结构及对应典型形态[9]㊂在不同的条件下颗粒形貌会发生变化,常见的晶体形态有立方形㊁球形㊁针形㊁链形等,不同形态的碳酸钙具有不同的性质,能够适用于不同领域的应用[10]㊂图1㊀碳酸钙的三种晶体结构和典型形态[9]Fig.1㊀Three crystal structures and typical morphologies of calcium carbonate [9]立方形碳酸钙具有一定的强度优势,作为填充剂可以起到补强作用,常用于塑料㊁橡胶行业[11];球形碳酸钙具有比较大的比表面积和良好的分散性,对油墨有很好的吸收性,多用于造纸行业[12];针形碳酸钙能够增加橡胶制品的耐曲挠性,添加到复合材料中能够起到补强增韧的作用[12-13];链形碳酸钙颗粒混入橡胶或712㊀综合评述人工晶体学报㊀㊀㊀㊀㊀㊀第52卷塑料时,可以有效地起到补强作用[11]㊂不同行业对最终得到的纳米碳酸钙产品的品质有不同的指标要求,归纳起来主要有纯度㊁白度㊁形貌㊁晶型㊁粒径范围㊁沉降体积㊁比表面积㊁分散性和白度等㊂在制备纳米碳酸钙的过程中,各项指标受多种因素的影响,最终得到的产品指标要符合国标要求[13],国标中规定了在橡胶㊁塑料㊁涂料等行业中纳米碳酸钙产品性能指标要求,具体如表1所示㊂表1㊀纳米碳酸钙产品性能指标要求[14]Table1㊀Performance index requirements of nano calcium carbonate product[14]项目橡胶塑料用指标Ⅰ型Ⅱ型Ⅲ型涂料用指标平均粒径/nm<5050~70<100ɤ60~90比表面积BET/(m2㊃g-1)ȡ18ȡ18ȡ18ȡ20碳酸钙干基质量分数/%ȡ95ȡ95ȡ95ȡ95白度ȡ95ȡ95ȡ94ȡ93吸油值ɤ30ɤ30ɤ40ɤ30~50控制结晶过程能够制备出不同晶型㊁形貌的纳米碳酸钙产品,从而提高产品最终的附加值与适用性,控制的变量有各项工艺参数以及添加剂的种类㊁用量等,如何可控制备纳米碳酸钙将在下文详细论述㊂2㊀纳米碳酸钙的制备纳米碳酸钙是指尺寸在纳米数量级的碳酸钙,与常规的无机材料不同,它具有特殊的小尺寸效应㊁宏观量子隧道效应㊁量子尺寸效应和表面效应等特性,增韧补强的效果非常显著[15-16]㊂通过物理㊁化学方法可以加工得到适用于不同应用场景的产品㊂2.1㊀传统纳米碳酸钙的制备方法纳米碳酸钙主要有以下三种合成体系:1)Ca(OH)2 H2O CO2;2)Ca2+ H2O CO2-3;3)Ca2+ R CO2-3㊂根据合成过程中化学反应的不同进行划分,CaCO3的合成可以分成碳化法㊁复分解法和乳液法[6]㊂表2列出了纳米碳酸钙的制备方法及其各自特点㊂表2㊀纳米碳酸钙的制备方法[17]Table2㊀Preparation method of nano calcium carbonate[17]反应体系制备方法优点不足Ca(OH)2 H2O CO2反应体系间歇鼓泡碳化法成本低,操作简单,生产能力大能耗高,产品粒径不均匀连续喷雾碳化法可连续,生产能力大,产品可控设备要求高,技术含量高,管理难度大间歇搅拌碳化法产品可控,常用设备投资大,操作复杂超重力反应结晶法时间短,产品粒径范围集中反应装置要求高,能耗大Ca2+ H2O CO2-3反应体系氯化钙碳酸铵法氯化钙碳酸氢钠法原料易得且成本低,制备工艺操作简单,产品白度较高杂质离子难去除石灰碳酸钠法Ca2+ R CO2-3反应体系凝胶法产品可控,适合研究结晶过程有机物难去除微乳液法避免产品团聚,操作简单主要应用于试验其中Ca(OH)2 H2O CO2反应体系即碳化反应体系,是目前工业生产纳米碳酸钙最常用的方法㊂碳化反应属于气-液-固三相反应,具体反应过程为[18]:Ca(OH)2(s)⇌Ca2+(aq)+2OH-(aq)(1)CO2(g)⇌CO2(aq)(2)CO2(aq)+2OH-(aq)⇌CO2-3(aq)+H2O(aq)(3)Ca2+(aq)+CO2-3(aq)⇌CaCO3(s)(4) 2.2㊀电石渣制备纳米碳酸钙电石渣是以Ca(OH)2为主要成分,还有少量Fe㊁Si㊁Al㊁Mg杂质的固废资源[19]㊂通过预处理方法提取其㊀第4期丁㊀羽等:电石渣可控制备多晶型㊁多形貌纳米碳酸钙的研究进展713㊀中钙离子,形成的含钙溶液与CO 2进行碳化反应生产纳米碳酸钙,典型工艺如图2所示㊂在制备过程中需要解决杂质去除㊁钙离子有效提取㊁碳化成核㊁晶体生长与控制几个方面的问题,针对这些问题不断进行工艺的选择和优化㊂图2㊀电石渣制备纳米碳酸钙的典型工艺[11]Fig.2㊀Typical preparation process of nano calcium carbonate produced from calcium carbide slag [11]2.2.1㊀预处理电石渣制备纳米CaCO 3需经过预处理,常见的方法有高温煅烧法和溶液浸提法㊂电石渣中含有一些焦炭和氧化物杂质,去除不彻底将会影响最终产品的白度和活度㊂高温煅烧法可去除残留的微量碳组分,但不能去除Fe㊁Si㊁Al㊁Mg 的氧化物杂质,获得产品纯度不高[20]㊂溶液浸提法能够有效地从电石渣中提取钙,电石渣中不与溶液反应的含硅铝铁的固体杂质经过滤去掉,得到纯度好㊁白度高的纳米碳酸钙[21]㊂提钙过程中涉及很多影响因素,如浸提液以及各项工艺参数温度㊁pH 值㊁搅拌速度等㊂浸提液的选择:使用酸类㊁盐类溶液来促进碱性原料中有效钙的溶解,然后进行固液分离,利用液相进一步生产高纯度的CaCO 3[22]㊂在这一过程中,NH 4Cl㊁NH 4HSO 4㊁甘氨酸㊁柠檬酸等均可以作为浸提液,提高在碳酸化反应的溶液中Ca 2+的可用性,表3总结了不同浸提液的效果㊂表3㊀浸提过程的主要参数[23-26]Table 3㊀Main parameters of the extraction process [23-26]浸提液浓度反应条件钙的转化率文献NH 4Cl 2.5mol /L 室温㊁浸提时间30min㊁pH =892%[23]NH 4HSO 4 1.4mol /L 100ħ㊁3h 接近100%[24]柠檬酸0.08mol /L 室温㊁持续搅拌92%[25]甘氨酸2mol /L 原料粉煤灰㊁室温42%[26]总结近几年的研究[23-30],酸性铵盐(NH 4Cl㊁NH 4HSO 4等)被认为是常见㊁效果优良的浸提液㊂柠檬酸㊁甘氨酸等浸提液在制备过程中能够呈现多重作用:水溶液中的氨基酸可以根据环境的变化灵活地转移质子,甘氨酸在浸提过程中能够促进Ca 2+浸出,在碳酸盐沉淀过程中既利于CO 2吸收又可在晶体生长过程中充当晶型调节剂[26];柠檬酸盐中的柠檬酸根离子对钙离子具有配位作用,可以显著提高电石渣的浸出率,在结晶过程中可以减缓晶体生长并有利于纳米尺度上的沉淀[25]㊂工艺参数的影响:浸提过程中涉及很多影响因素,为探究最佳工艺条件,分别研究了pH 值㊁反应时间㊁NH 4Cl 过量程度这三个影响因素的作用效果㊂在浸提过程中Fe㊁Si㊁Al㊁Mg 的氧化物或氢氧化物是主要的杂质,利用缓冲溶液控制pH >7,此时杂质物质的溶解度小,杂质的影响作用较小[31]㊂如图3(b)所示,随着氯化铵过量程度的增加,Ca 2+提取率呈现先降低后增加的趋势,但都低于不过量时的值,因此一般选择不过量进行实验;如图3(c)所示,随着反应时间的增加,Ca 2+提取率呈现上升趋势,30min 时Ca 2+提取率达到最高值,说明化学反应已完成㊂2.2.2㊀碳化反应比较而言,碳化法更容易对碳酸钙的晶型以及形貌进行控制[5]㊂碳酸钙晶体的产生发生在碳化阶段,通过控制碳化阶段的工艺参数如Ca 2+浓度㊁温度㊁pH 值㊁添加剂等,最终可以得到不同的产品㊂工艺条件的影响:在碳化反应过程中,化学反应㊁成核和生长是同时发生的3个主要步骤[32]㊂因此,在碳化反应过程中改变条件控制这3个步骤,能够得到不同的纳米CaCO 3产品㊂反应物盐(Ca 2+)的初始浓度影响合成CaCO 3颗粒的大小㊁形貌等㊂例如,在乙二醇的存在条件下控制714㊀综合评述人工晶体学报㊀㊀㊀㊀㊀㊀第52卷Ca2+的添加量,可以使产品颗粒的大小和形态可控㊂Ca2+浓度的差异对体系中的反应有不同的影响,过量的Ca2+减缓颗粒的形成过程,促进CaCO3颗粒的生长,Ca2+少而CO2-3过量时加速反应,促进早期成核,高浓度Ca2+能够形成各向异性菱形和椭球形产品,而低浓度下能形成各向同性球状体[33]㊂图3㊀pH值(a)㊁NH4Cl过量程度(b)㊁反应时间(c)对Ca2+转化率的影响[31]Fig.3㊀pH value(a),excessive degree of NH4Cl(b),leaching time(c)on Ca2+conversion rate[31]温度影响CaCO3沉淀的生成和溶解平衡,成核和生长速率受温度的影响,CaCO3沉淀在水中的溶解度随温度的变化而变化,从而对最终形成晶体的形貌和大小有显著影响㊂Domingo等[34]在45ħ时获得了菱形锐边颗粒,而通过将温度降低至25ħ观察到了偏三角面体颗粒的存在;García Carmona等[35]通过提高温度获得了粒径更大的晶体㊂pH值的作用影响具体表现为水溶液中各离子的平衡,CaCO3在水溶液中的沉淀和溶解涉及不同离子的平衡,H+㊁OH-㊁HCO-3㊁Ca2+和CO2-3的整体平衡可调节pH范围从中酸性到碱性,相关离子之间的平衡可以用各自的方程和平衡常数(K x)来描述[36]㊂可以计算出溶液中所有物种的浓度和反应活性,还可以根据公式(12)估计系统的过饱和状态从而推断晶体类型[37]㊂H++OH-↔H2O(K w)(5)CO2(g)↔CO2(aq)↔H2CO3(aq)(K H)(6)H++CO2-3↔HCO-3(K1)(7)H++HCO-3↔H2CO03(K2)(8)Ca2++CO2-3↔CaCO03(K CaCO3)(9)Ca2++HCO-3↔CaHCO+3(K CaHCO+3)(10)Ca2++OH-↔CaOH+(K CaOH+)(11)S={[a(Ca2+)㊃a(CO2-3)]/(K0sp)}1/2(12)添加剂的影响:不同的添加剂通过进入晶体内部㊁吸附在晶体表面上和改变晶体表面能等方式来影响晶体的生成过程,从而达到可控制备特定产品的目的[38-40]㊂从种类上可分为无机盐类㊁醇类㊁酸类㊁糖类和表㊀第4期丁㊀羽等:电石渣可控制备多晶型㊁多形貌纳米碳酸钙的研究进展715㊀面活性剂类等,表4总结了不同添加剂对获得的CaCO3性能的主要影响㊂表4㊀添加剂对纳米碳酸钙颗粒性能的影响[41-47]Table4㊀Effect of additives on the properties of nano calcium carbonate particles[41-47]添加剂添加剂类型浓度操作条件主要作用参考文献磷酸酸 3.5~10g/L70ħ促进文石形成[41]蔗糖㊁葡萄糖糖 Mg2+存在促进方解石超过文石[42]乙醇醇10%~50%v/v n(NH+4)/n(Ca2+)ȡ1促进球霰石㊁文石形成[43] NH+4无机盐n(NH+4)/n(Ca2+)>1低pH促进球霰石的形成[44] Mg2+无机盐n(Mg2+)/n(Ca2+)>1低pH,温度>30ħ促进文石的形成[45] CTAB阳离子表面活性剂2% 降低粒径,有利于菱形形成[46] SDS阴离子表面活性剂2g/L室温㊁4.9~12.04MPa形成具有粗糙表面的菱形方解石颗粒[47] Tween80非离子表面活性剂2g/L室温㊁4.9~12.04MPa促进纳米粒子聚集成片状[47]㊀㊀注:CTAB为十六烷基三甲基溴化铵;SDS为十二烷基硫酸钠㊂1)酸类添加剂的影响常见的有机酸类添加剂含有羧基,在晶体生长的过程中,羧酸的加入可能与碳酸钙发生强烈吸附作用,羧酸被吸附在晶体的表面上,阻碍了碳酸钙颗粒的进一步生成,从而对晶体的形貌和粒径产生影响[48]㊂而无机酸能够通过发生化学反应影响最终碳酸钙的生成,例如加入无机酸H3PO4时,H3PO4与Ca2+迅速反应形成非常细的针状羟基磷灰石(HAP,最稳定的磷酸钙),在碳化过程中针状HAP作为异质成核剂,有利于文石的形成[49-50]㊂2)糖类添加剂的影响常见的糖类添加剂有蔗糖㊁葡萄糖㊁可溶性淀粉等,含有羟基㊂Ca2+可以与糖类中所含的羟基发生电荷匹配作用,降低CaCO3结晶的成核活化能,促进成核,抑制晶体生长㊂根据徐大瑛等[51]的研究结果,添加糖类添加剂后生成的纳米碳酸钙颗粒均以方解石为主,形状比较规则,具体表现为添加葡萄糖后颗粒边界不够清晰,加入蔗糖后边界清晰但分散性一般,加入可溶性淀粉后粒径明显减少㊂3)醇类添加剂的影响醇类添加剂的加入有利于亚稳态晶型的生成,在50%乙醇的存在下,球形球霰石颗粒与方解石晶体一起出现[43]㊂乙醇对亚稳态球霰石形成的影响可以通过两种机制来解释,乙醇降低了CaCO3的溶解度,最终增加了其过饱和,这促进了动力学有利的球霰石相的产生,而不是热力学有利的方解石;另一种机制与Ca2+和CO2-3的相互作用有关,与水相比,Ca2+与乙醇的相互作用较弱,这有利于亚稳态球霰石的形成[52]㊂4)无机盐类添加剂的影响在碳酸钙生成过程中添加氨,NH+4能够提供碱性环境使反应混合物产生高过饱和度和成核率,有利于亚稳态球霰石的沉淀㊂此外,NH+4能够在吸收二氧化碳的过程中产生氨基甲酸盐来稳定球霰石颗粒[43-44]㊂Mg2+可以取代方解石中的Ca2+并结合到Mg-方解石的晶格中,由此产生的晶格畸变导致结构不稳定,Mg-方解石的溶解度增加,Ca2+在溶液中含量增加成为过饱和溶液,有利于文石的形成[42]㊂5)表面活性剂类添加剂的影响表面活性剂可能与特定的晶面发生特异性结合,在碳酸钙可控制备的过程中表现出显著的优势㊂SDS的烷基链带负电荷,可以吸附到CaCO3的正电荷面上,有利于形成表面粗糙的立方CaCO3颗粒;添加CTAB 对颗粒形态影响较小,这是由于带正电荷的烷基链和Ca2+之间的静电排斥作用使得它很难吸附到CaCO3的表面上;Tween80作为一种非离子表面活性剂能够优先吸附在中性面上,最终形成片状形貌[47]㊂尽管对CaCO3的多晶型㊁形貌和尺寸分布的控制已经成为许多学术研究的焦点,但是对CaCO3结晶的相关理论理解以及对实际技术的应用仍然存在挑战,下文将从碳酸钙结晶过程以及动力学㊁热力学方面来深入探讨相关调控理论机制㊂3㊀结晶调控理论为了可控合成纳米碳酸钙,可以选择不同的制备方法以及添加剂,通过不断调整实验参数来控制结晶过程,最终得到特定晶型和形貌的碳酸钙产品㊂因此,了解碳酸钙的结晶生长过程是十分重要的㊂结晶过程实716㊀综合评述人工晶体学报㊀㊀㊀㊀㊀㊀第52卷际上受热力学和动力学的共同控制,因此动力学和热力学是控制结晶的理论基础,通过对基础规律的研究进一步认识调控的机理,最终实现晶型和形貌的调控[53]㊂3.1㊀碳酸钙结晶过程要实现对碳酸钙晶体的结晶调控,首先要明确结晶过程的各个阶段,以及各个阶段对产物晶型㊁形貌的影响㊂一般来说,结晶过程包括了竞争成核和晶体生长㊂碳酸钙是研究结晶矿物成核和结晶的一个重要模型体系,图4为碳酸钙的两种结晶路线㊂碳酸钙成核阶段的理论可分为经典成核理论和新型成核理论,经典成核理论基础源于热力学基本定律,溶液中的分子在热运动作用下发生相互碰撞,生成具有临界尺寸的晶核前体,这些晶核继续生长为最终晶体㊂而新型理论认为在结晶过程中先形成预成核离子团簇,预成核离子团簇PNCs 聚集进一步形成无定形碳酸钙(amorphous calcium carbonate,ACC)前驱体,最后ACC 转化成为矿物晶体[54]㊂晶体生长阶段的理论可以分为平衡生长理论和晶面生长理论㊂晶体的平衡态理论认为,晶体最终会生长为稳定㊁平衡的形态,而一个晶体上所有晶面的表面能之和最小的晶体形态是最稳定的,因此在晶体生长过程中趋向于使体系的表面能最小;晶面生长理论主要讨论界面处的作用,目前存在几种典型模型用以解释晶面生长的过程㊂层生长模型认为从某一晶面开始生长,长满一层开始循环层列生长过程;螺旋生长模型认为各晶体层的生长同时进行,实际晶体表面产生的错位㊁缺陷成为倾斜螺旋生长起点;负离子配体生长基元模型可以用来解释许多同质异构体晶体的形成,生长环境的差异导致晶体生长基元的维度或结构产生不同,最终导致不同形态晶体的生成[55]㊂图4㊀碳酸钙结晶路线图[54]Fig.4㊀Calcium carbonate crystallization roadmap [54]3.2㊀动力学、热力学对结晶控制的影响碳酸钙晶体在热力学和动力学驱动下的结晶路径如图5所示,其中A 表示碳酸钙在热力学控制下的结晶路径,热力学研究物质变化过程的能量效应及反应的方向和限度,即有关平衡的规律,热力学决定了结晶的终态,是一个状态函数;B 表示在动力学控制下的结晶路径,动力学研究反应速率以及实现反应过程的具体步骤,动力学决定了亚稳态相向稳态相转化的方式和速率,是一个过程函数[56]㊂图5㊀热力学和动力学驱动下的结晶路径示意图[57]Fig.5㊀Schematic diagram of crystallization pathways driven by thermodynamics and kinetics [57]在碳化反应过程中,成核过程是控制晶型的关键步骤㊂在经典成核理论中将晶核形成能表示为体自由能和表面能两项,可以定量地表征成核速率随过饱和比或温度的变化规律,不同晶型的可控制备可能取决于过饱和度[55]㊂在新型成核理论中,只有当初始过饱和度很高时,热力学亚稳相ACC 才可能会产生,这一现象满足奥斯特瓦尔德阶段规则,亚稳相的形成通常在较高的过饱和度时获得,在动力学上是有利的,并先于热力学稳定相的形成[10]㊂含有羧基㊁羟基等不同官能团的添加剂能够诱导亚稳态多晶相的优先形成,有利于多晶型的制备[58]㊂晶体生长过程对形貌的影响较大,过饱和度低时,晶体的生长方式通常为螺旋生长;提高过饱和度时,层㊀第4期丁㊀羽等:电石渣可控制备多晶型㊁多形貌纳米碳酸钙的研究进展717㊀状生长方式逐渐占据主导地位;而在高饱和度的溶液中晶体表现为活性位点多的枝状生长方式[55]㊂溶液体系中的过饱和度差异使晶体中各个晶面的生长速率不同,而低表面能的晶面由于生长速度慢㊁晶面大的优势能够得到优先表达,从而导致晶体最终形貌的不同[59]㊂添加剂除了对晶型产生决定性的作用以外,还会在晶体生长过程中影响不同表面的表面能,从而对晶体的形貌起到一定的调控作用[60]㊂4㊀结语与展望本文综述了电石渣制备纳米碳酸钙的方法和结晶调控的研究进展,具体总结如下:对比分析不同体系下的制备方法,碳化法合成纳米碳酸钙是简便㊁环保和可控的方法,在工业上也得到广泛应用,被研究最多;在预处理过程中,酸性铵盐浸提能够获得较高的Ca2+转化率,具有巨大的发展潜力,并且通过浸提工艺的优化可以进一步提高转化率,在碳化反应过程中,工艺参数主要影响晶体的形貌和粒径,添加剂对晶型㊁形貌的影响较大;从热力学和动力学的角度出发,改变成核过程中的过饱和度有利于实现内部晶体结构调控,改变晶体生长方式能够实现晶体外部形貌调控㊂综合电石渣可控制备纳米碳酸钙的研究进展,提出以下几点展望:在制备方法的选择方面,大多数研究处于实验室阶段,有待产业化推广;选择电石渣等固体废弃物制备碳酸钙产品,与传统的原料石灰石相比,成分较为复杂,需要全面考虑杂质的去除和Ca2+的提取;如何有效控制纳米碳酸钙粒子的晶型㊁形貌等性质,目前还没有形成成熟的理论,需深入了解结晶学相关理论及各种影响因素的内在逻辑,实现调控碳酸钙结构的目标㊂参考文献[1]㊀CHENG J,ZHOU J H,LIU J Z,et al.Physicochemical characterizations and desulfurization properties in coal combustion of three calcium andsodium industrial wastes[J].Energy&Fuels,2009,23(5):2506-2516.[2]㊀李彦鑫,张金山,曹永丹,等.电石渣的理化性质表征及其应用研究[J].无机盐工业,2018,50(4):49-52.LI Y X,ZHANG J S,CAO Y D,et al.Characterization of physiochemical property of carbide slag and its application study[J].Inorganic Chemicals Industry,2018,50(4):49-52(in Chinese).[3]㊀YANG H,CAO J W,WANG Z,et al.Discovery of impurities existing state in carbide slag by chemical dissociation[J].International Journal ofMineral Processing,2014,130:66-73.[4]㊀董永刚,曹建新,刘㊀飞,等.电石渣理化性质的分析与表征[J].环境科学与技术,2008,31(9):95-98.DONG Y G,CAO J X,LIU F,et al.Analysis and characterization of physiochemical property of carbide slag[J].Environmental Science& Technology,2008,31(9):95-98(in Chinese).[5]㊀孔祥波.超微细无定形碳酸钙粉体的制备㊁改性及其应用[D].厦门:厦门大学,2017.KONG X B.The preparation,modification of superfine amorphous calcium carbonate and its application[D].Xiamen:Xiamen University,2017 (in Chinese).[6]㊀冯文华.纳米碳酸钙制备新工艺研究[D].上海:华东理工大学,2015.FENG W H.Study on preparing new technology for nano calcium carbonate[D].Shanghai:East China University of Science and Technology, 2015(in Chinese).[7]㊀郭琳琳,范小振,张文育,等.电石渣制备高附加值碳酸钙的研究进展[J].化工进展,2017,36(1):364-371.GUO L L,FAN X Z,ZHANG W Y,et al.Research progress on preparation of calcium carbonate with carbide slag[J].Chemical Industry and Engineering Progress,2017,36(1):364-371(in Chinese).[8]㊀王倩倩.碳酸钙矿物的晶型调控试验研究[D].包头:内蒙古科技大学,2020.WANG Q Q.Study on crystal regulation of calcium carbonate mineral[D].Baotou:Inner Mongolia University of Science&Technology,2020 (in Chinese).[9]㊀NIU Y Q,LIU J H,AYMONIER C,et al.Calcium carbonate:controlled synthesis,surface functionalization,and nanostructured materials[J].Chemical Society Reviews,2022,51(18):7883-7943.[10]㊀CHONG K Y,CHIA C H,ZAKARIA S,et al.Vaterite calcium carbonate for the adsorption of Congo red from aqueous solutions[J].Journal ofEnvironmental Chemical Engineering,2014,2(4):2156-2161.[11]㊀石㊀闯.利用电石渣制备超细活性碳酸钙的技术与机理[D].北京:中国地质大学(北京),2016.SHI C.Thetechnology and mechanism of the preparation of superfine active calcium carbonate by using carbide slag[D].Beijing:China University of Geosciences,2016(in Chinese).[12]㊀马蓝宇.碳酸钙微粒的形貌控制与应用[D].柳州:广西科技大学,2017.。

高分子材料纳米二氧化硅外文文献翻译

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

三种有机成核剂成核聚丙烯的非等温结晶动力学研究

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

用Avrami 方程对DSC的测试结果进行了分析。

结果表明三种有机透明成核剂能显著提高PP的结晶温度和结晶速率。

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

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

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

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