水热法制备表面修饰的钛酸锶纳米微粉

以工业原料和常用试剂TiCl4、Sr(NO3)2和KOH为基础原料,通过添加表面活性剂十二烷基苯磺酸(DBS),采用水热法制备出表面包裹有DBS的钛酸锶纳米微粉,并应用红外光谱,X射线衍射谱,透射电子显微镜,热分析等一系列手段对其微结构进行了表征.结果表明:样品为表面包裹有DBS的钛酸锶纳米微粉,其形状较为规则,粒度分布较窄,单分散性较好.粒子的平均粒径为120nm,包裹膜的平均厚度为6nm左右.根据X光谱测量,表面修饰后的钛酸锶纳米微粉均以立方相存在.一般体相钛酸锶微粉为极性粉体.而表面修饰后的钛酸锶纳米微粉能够较为稳定地悬浮于非极性液体如正己烷中,说明SrTiO3粉体的极性表面被DBS包裹后,变为非极性.     

单分散钛酸钡纳米晶的制备

采用溶剂热法制备出表面包裹油酸的单分散立方相钛酸钡纳米晶, 晶粒平均尺寸为6.0 nm, 采用TEM和XRD对其微结构进行了表征; 研究了醇的链长度、油酸用量和热处理温度等对钛酸钡的相组成和形貌的影响规律. 研究结果表明, 产物粒径较小, 粒度分布较窄, 单分散性较好, 其表面为非极性, 可溶于非极性试剂; 由于纳米晶表面由亲油性的长链烷基所覆盖, 与周围的水性环境不相容, 产生一定的斥力; 在重力和该斥力的共同作用下, 纳米晶可以有效地从液相环境中分离出来.     

不同Ti/Ba比钛酸钡纳米粉体及其陶瓷的制备和介电性能研究

采用溶胶-凝胶(Sol-gel)法制备了不同Ti/Ba比的钛酸钡纳米粉体及其陶瓷。通过XRD、SEM和TEM对钛酸钡粉体及陶瓷进行了表征,并测试了陶瓷的介电性能,研究了Ti/Ba比对陶瓷微观结构和介电性能的影响。结果表明:通过溶胶-凝胶工艺制备的纳米粉体主要为立方相钛酸钡,平均粒径约19~33 nm:随Ti/Ba比的增加,钛酸钡纳米粉体平均粒径呈先稍递减后增大的趋势,当粉体平均粒径大于30 nm吋,四方相在混合相中所占比例逐渐增大;Ti/Ba=1.01~1.03时,陶瓷中异常长大的晶粒较多,室温介电常数降低;1300℃烧结2 h的Ti/Ba=1.04的钛酸钡陶瓷具有较好的介电性能。     

纳米氧化锌的合成及表面改性

以硫酸锌、尿素为原料,采用均相沉淀法合成了纳米氧化锌.研究了硬脂酸对所制的纳米氧化锌粉体表面改性的机理及其对粉体亲油性的影响.实验结果表明,硬脂酸中的羧基与纳米氧化锌粉体颗粒表面的羟基发生了酯化反应,并在表面形成单分子膜.经过表面改性的纳米氧化锌由亲水性转化为亲油性.同时,就纳米氧化锌粉体硬脂酸表面改性反应,探讨了反应摩尔分数、反应温度和反应时间对产物的影响,从而筛选出粉体亲油性最大的反应条件为:硬脂酸质量分数为7%;反应温度为50℃;反应时间为1h.     

纳米钛酸钡及其烧结物的制备

溶胶 凝胶技术已为制备各种金属氧化物纳米材料的较普遍方法[1],其优点是产物具有超细颗粒尺寸 ,高纯度和化学均匀性 .溶胶 凝胶法制备纳米钛酸钡时一般将钛的有机醇盐与钡盐反应生成溶胶 ,然后形成凝胶 ,再进行热处理制得纳米钛酸钡[2 ,3].本文以钛酸丁酯和氢氧化钡为原料 ,采用溶胶 凝胶工艺制备出纳米钛酸钡晶体粉末 .用ＴＧ ＤＴＡ和ＦＴＩＲ技术考查了纳米晶钛酸钡凝胶先体热分解反应过程 ,用ＳＥＭ和ＸＲＤ对粉体形貌和晶型进行分析 ;并用上述粉体制成了微观组织结构仍保持纳米尺寸的陶瓷材料 .粉体制备 :称 15 7ｇ氢氧化钡 (Ｂａ(…     

溶胶-凝胶法制备钛酸钡超细粉体的研究

钛酸钡是一种非常重要的铁电材料 ,其合成方法主要分为固相反应法和液相反应法。传统的固相反应法是以ＴｉＯ2 和ＢａＣＯ3 经高温反应制取钛酸钡粉体 ,该法产品杂质含量高 ,颗粒粗 ,均匀性差 ,粉体烧结温度高。与高温固相反应相比 ,液相法合成的钛酸钡粉体具有化学纯度高 ,颗粒细小 ,粒度分布均匀等优点。特别是以醇盐为原料 ,采用溶胶 凝胶法制备的钛酸钡粉体 ,其性能非常优异 ,已为许多研究者所关注[1,2 ] 。文献[3 ] 报道了以异丙醇钛和醋酸钡为原料 ,采用溶胶 凝胶法制备钛酸钡物体的研究 ,但未见有以钛酸丁酯及醋酸钡为原料制备钛酸钡…     

纳米化Fe2O3粉体的制备与表征

采用分析纯FeCl3·6H2O和NH3·H2O为主要原料,以均匀沉淀法制备了Fe2O3纳米粉体.通过X射线衍射(XRD)、红外光谱(IR)、扫描电子显微镜(SEM)及差热分析(DTA)等手段研究了热处理温度、分散剂、反应pH值对Fe2O3相变、结构、形貌及纳米属性的影响.结果表明:纳米化增大了Fe2O3的表面能,γ-Fe2O3转变为α-Fe2O3的温度仅为238.2 ℃,比常规粉体降低了约312 ℃;由于量子尺寸效应和表面效应,使用分散剂后α-Fe2O3纳米粉体的分散性、均匀性得到改善,粒径下降,Fe-O键伸缩及弯曲振动IR吸收频率发生蓝移;尤其是硬脂酸钠分散后α-Fe2O3的Fe-O伸缩、弯曲振动吸收频率分别蓝移11.57、10.93 cm-1;获得了液相均匀沉淀法制备Fe(OH)3纳米粉体的最佳工艺条件.     

超细钛酸钡的表面改性

利用Sol-gel法成功地在超细钛酸钡粉体表面包覆了厚度约5nm的均匀SiO2膜。采用HRTEM,XPS和XRD等多种分析方法,证实了SiO2薄膜的存在。并首次提出钛酸钡水解后水玻璃在TiO2-x表面溶胶-凝胶化的包覆机理。改性后的钛酸钡与纯钛酸钡相比,SiO2包覆可促进烧结,包覆SiO2坯体在1190℃达到最大收缩速率,而纯钛酸钡坯体达到最大收缩速率的温度为1260℃。坯体的收缩率由未包覆前的-15%变化到-19.3%。包霖工艺改善了介电性能,使介温曲线平坦,对制造钛酸钡薄层电容器有重要的价值。     

表面修饰二氧化钛纳米粒子的结构表征及形成机理

利用溶胶 凝胶法在混合溶剂中制备了硬脂酸表面修饰TiO2纳米粒子,对所合成的纳米粒子通过FTIR、XPS、XRD和TEM对其结构进行表征.结果确证了表面有机修饰层的存在,并且是羧酸根与无机内核以双齿配位形式结合;无机纳米内核的结晶度很低,但是可以确定为锐钛矿成分,平均粒径约为6～8 nm.提出了表面修饰纳米粒子的形成机理,认为在体系中硬脂酸和水之间发生竞争反应,其过程类似于聚合 阻聚反应,最后给出了硬脂酸表面修饰TiO2纳米粒子的结构模型.     

CO2超临界干燥制备超细TiO2粉体的研究

采用溶胶-凝胶法结合CO2超临界流体干燥技术制备了平均粒径为8nmTiO2粉体颗粒,并采用BET、TEM、SEM、XRD、及DTA-TG技术对制得的粉体进行了表征.结果显示出CO2超临界干燥技术在制备大孔高比表面TiO2纳米粉体时具有较大的优越性.     

Nd-doped barium titanate ceramics with various Ti/Ba ratios prepared by sol-gel method

The Nd-doped BaTiO3 nanocrystalline powders and ceramics with different Ti/Ba ratios were prepared by sol-gel method. Phases and microstructures of the Nd-doped BaTiO3 based powders and ceramics were characterized by XRD, SEM and TEM methods. The results revealed that the powders synthesized by sol-gel method were nanometer scale (30-60 nm) and were mainly composed of cubic BaTiO3 with a small amount of BaCO3. After sintering at high temperature, both cubic BaTiO3 and BaCO3 were transformed into tetrahedron BaTiO3 phase. The dielectric properties of the ceramics were also determined and the influence of Ti/Ba ratio on the dielectric properties was discussed. The Tc did not change with the variation of Ti/Ba ratio, while theεmax increased firstly and then decreased. The excess TiO2 is benefit for the modification of ceramics' microstructure and dielectric properties.     

喷雾热分解法制备的钛酸钡颗粒内钡钛元素分布

基于氯化钡和二氧化钛具有不同的溶解特性,采用溶剂萃取法分别对喷雾热分解法和喷雾水解反应法制备的钛酸钡前驱体干燥产物颗粒内钡和钛分布进行定性分析,从而间接钛酸钡颗粒内的钡和钛分布情况。实验结果表明,该法可快速而准确地分析组合分析组分偏析情况。     

低温-低压水热合成Ba1-xSrxTi1-ySnyO3纳米材料及其 结构与性能研究

采用低温-低压水热法,在150℃,0.5MPa以下合成了一系列Ba1-xSrxTi1-ySnyO3固溶体纳米粉末(0≤x≤0.5≤y≤0.4),经XRD物相分析和d-间距-组成图证明,产品为立方晶系的完全互溶取代固溶体,结果符合Vegard定律,TEM形貌观察,粒子为均匀球形,平均粒径80nm。通过制陶实验,分别测定了该系列固溶体的室温介电常数、介电损失以及介电常数随温度的变化。结果发现,用该方法在BaTiO3中掺入适量锶和锡,由于掺杂离子均匀进入母体晶格,引起Tc降低,介电性能改善显著,当x=0.1,y=0.08时,室温介电常数达17000,比BaTiO3纯相提高10倍,而介电损失却降低88%。     

溶胶-凝胶法制备掺锰钛酸钡纳米粉体及其陶瓷

The Mn-doped barium titanate nanosized powders and ceramics were prepared via the sol-gel process. The powders and ceramics were characterized by XRD， SEM and TEM. The dielectric properties of the ceramics were also measured. The influences of calcination temperature and Mn concentration on the microstructure， dielectric properties and phase composition of BaTiO₃ nano-powders and ceramics were discussed. The results indicated that the BaTiO₃-based powders doped with 1.0mol% Mn were mainly in cubic BaTiO₃ phase， but the tetragonal phase became more evident when the calcination temperature increased. After sintering， Mn-doped ceramics were mainly composed of cubic BaTiO₃. Specially， a new phase of hexagonal crystal BaTiO₃ and BaMnO₃ existed in the ceramics doped with 5.0mol% Mn and the ceramic grains were in ‘clintheriform’. The structure of ‘clintheriform’ led to the poor densification of ceramics， reducing the dielectric constant obviously. The dielectric constants of BaTiO₃ ceramics first increased and then decreased as the Mn concentration increased. The room temperature dielectric constant was 2 290 and the lowest dielectric loss was 0.004 when the Mn concentration was 0.5mol%.     

聚苯胺颗粒材料的表面改性

用改性的溶胶-凝胶法制备了表面包覆有一定厚度的钛酸钡薄膜的聚苯胺,通过TEM和FT-IR分析方法研究了其形貌及微结构,并探讨了改性聚苯胺材料的电流变性能.FT-IR研究结果表明,在聚苯胺与钛酸钡之间存在着N－O间的氢键作用.TEM研究结果表明,改性聚苯胺粒子的直径在1.0～1.5 μm之间.此外,包覆工艺显著改善了材料的介电性能和电流变性能,为制备出高性能的电流变材料提供了一条可行的途径,值得进一步研究.     

Hydrotherrnal synthesis, structure and property of nano-BaTiO3-based dielectric materials

A series of Ba1-xSrxTi1-yZryO3 (0≤x≤0.5, 0≤y≤0.4) and Ba1-xZnxTi1-ySnyO3 (0≤x≤0.3, 0≤y≤0.3) solid solutions were synthesized by Iow-temperature/Iow-pressure hydrothermal method below 170℃, 0.8 MPa. XRD pattern and cell parameters-composition figures of these prepared powders demonstrated that they are completely miscible solid solutions based on BaTiO3. Furthermore, TEM showed that they have a shape of uniform, substantially spherical particles with an average particle size of 70 nm in diameter. The sintered ceramics of those powders doped by Sr2+ and Zr4+ or Zn2+ and Sn4+ have dielectric constant twelve times higher than and dielectric loss 1/6 those of pure BaTiO3 phase at room temperature.     

核壳型聚苯胺/钛酸钡的结构及其电流变性能

用改进的溶胶-凝胶法制备了核壳型聚苯胺/钛酸钡复合微粉,通过TEM及FT-IR分析表征了其形貌及微观结构,用复合微粉与氯化石蜡油配制成无水电流变(ER)液,研究其不同膜厚核壳粒子的电流变性能.研究结果表明,聚苯胺/钛酸钡复合粒子配置成的电流变液的电流变性能较纯聚苯胺的为强;钛酸钡的涂层厚度对复合粒子电流变性能有重要影响;并在d=20 nm时获得最佳电流变性能.     

Volatile Compounds Present in Carbon Blacks Produced by Thermal Plasmas

Carbon black nanopowders were produced using two thermal plasma processes based on DC, respectively ICP plasma torches. Although the produced particles were in the nanometer size range, the values obtained for the surface area of the particles using a Brunauer Emmett Teller technique were very small. This indicated the presence of contaminants in the experimental powders, as confirmed by Raman spectroscopy and Thermogravimetric Analysis. A thermal treatment process was developed in order to extract these volatile compounds, which were then identified using a Gas Chromatography—Mass Spectrometry method. The experimental powders were analyzed using Scanning and Transmission Electron Microscopy, X-Ray Diffraction and Raman Spectroscopy before and after the thermal treatment in order to determine the effect of the heat treatment on the powder structural properties.