Preparation of highly dispersed antimony-doped tin oxide nanopowders by azeotropic drying with isoamyl acetate

Antimony-doped tin hydroxide colloid precipitates were prepared by hydrolysis of SnCl4·5H2O and SbCl3 ethanol solutions. Isoamyl acetate was selected as azeotropic drying solvent and was compared with the most commonly used n-butanol solvent on treating precipitate for low hard agglomeration precursor powders. The FT-IR, BET, XRD, and TEM results of the precursor powders and calcinated antimony-doped tin oxide powders were recorded. The results demonstrate that isoamyl acetate is an excellent azeotropic drying solvent that can effectively prevent the agglomeration of particles and greatly improve the fluffiness of the obtained dried powders. After these precursor powders are calcined, antimony-doped tin oxide nanopowders with tetragonal futile structure and high dispersivity can be obtained.     

PREPARATION OF NANOMETER ZrO2-8%Y2O3 POWDERS BY AZEOTROPIC DISTILLATION PROCESSING

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微乳法制备氧化锆纳米粉体

以可溶性锆盐溶液—环己烷—聚乙二醇辛基苯醚—正戊醇体系的微乳液反应为基础 ,以氨水为沉淀剂 ,在微乳液中发生化学反应产生凝胶状沉淀 ,经洗涤、焙烧得到超细分散 Zr O2 纳米粒子。本文在微乳液法的基础上加入了一种较新的脱水工艺—共沸蒸馏制备了纳米 Zr O2 粉末。通过比表面积 (BET)、透射电镜 (TEM)、X-射线衍射 (XRD)对样品进行了形态表征和物相分析 ,结果表明通过本方法制备的 Zr O2 纳米粉末尺寸可控制在小于 4 0 nm的范围内 ,并具有良好的分散性。共沸蒸馏能充分地脱去凝胶中残余的水分 ,防止因含水胶体干燥过程引起的粉末硬团聚 ,从而显著地提高了粉末的性能     

纳米γ-Al2O3的溶胶-凝胶法制备及表征

异丙醇铝为先驱体,异丙醇为溶剂,乙酰乙酸乙酯为螯合剂,聚乙二醇(PEG1000)为分散剂,硝酸为胶溶剂,采用溶胶-凝胶法制备了纳米γ-Al2O3.并采用DTA/TG,XRD,TEM等测试技术对纳米γ-Al2O3粉体进行表征.结果表明,通过溶剂、螯合剂、分散剂和胶溶剂的协同效应,在750℃煅烧条件下,γ-Al2O3粒子形貌为针状结构,长度为20～30 nm;在900℃煅烧条件下,γ-Al2O3粒子形貌为颗粒状,平均晶粒尺寸为10 nm左右;纳米γ-Al2O3粒子尺寸均一、分散性良好.     

纳米氧化铝粉体的绿色合成

以廉价的铝锭和异丙醇为起始原料,采用独特的分离提纯、回收再利用技术和溶胶凝胶工艺,合成高性能纳米氧化铝粉体,并利用TEM,XRD和石墨炉原子吸收法等对粉体的相组成、形貌和杂质含量进行分析研究.得出原料对粉体的形貌和组成没有影响,两种不同的Al源均制备出了粒径为10～20nm,球形γ-Al2O3粉体;而原料和蒸馏工艺对纳米氧化铝粉体的纯度有影响,随铝锭纯度的增加,所制备的纳米氧化铝所含的微量杂质含量明显下降.和一次蒸馏相比,二次蒸馏所得产物的主要微量杂质明显下降.利用重熔铝锭为原料,采用二次蒸馏工艺,制得了纯度高达99.99%的纳米氧化铝,且在制备过程中没有废液,废气排出,实现了高纯纳米氧化铝粉体的低成本、环保型生产.     

Hydro/solvo-thermal synthesis of ZnO crystallite with particular morphology

ZnO with controllable morphologies of hexangular pillars, tubes, tablets and tube-structured needles was hydro/ solvo-thermally synthesized by simply changing solvents among H2O, H2O2, alcohol and olefin, using Zn(NO3)2-6H2O and NaOH as the starting materials. The products were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence (PL) measurement. The growth mechanism of differently structured ZnO was discussed. The results reveal that the synthesized ZnO crystals possess a wurtzite structure, the solvent kind has very different influence on the morphology of ZnO, and the hexangular pillars, tablets, short pillars and needles of ZnO are easily obtained in solvent of H2O, C2H5OH+H2O, wet olefin, and H2O2.     

正交设计法优化高分散超细银粉的制备工艺

以AgNO3为银源,抗坏血酸为还原剂,通过液相还原法制备了超细银粉。运用L25(56)的正交试验设计,考察了AgNO3浓度、抗坏血酸浓度、分散剂种类、分散剂用量、溶液pH值及反应温度对超细银粉的分散性及粒度的影响。分析得出制备超细银粉的优化条件:AgNO3浓度为0.15mol.L-1,抗坏血酸浓度为0.40mol.L-1,油酸为分散剂,分散剂用量为8%(相对AgNO3质量),pH值为4,反应温度为50℃。在优化的实验条件下,制备出高分散近球形的超细银粉,其平均粒度为0.89μm。并运用SEM、XRD对其进行了表征。     

Hydridation and oxidation behaviors of tantalum hydride during milling process

The effect of ethanol addition during milling on the milling performances of Ta-hydride powders was investigated for hydride and dehydride processes during Ta recycling process. As the Ta-hydride was milled in a conventional dry atmosphere, Ta₂O was dominantly formed due to the increased temperature of the Ta-hydride pieces because they were rubbed against each other and crushed by the ring mill system. However, with the addition of ethanol solvent, the ratio of the Ta₂H phase increased compared to the Ta₂O phase, and the size of the powders reduced and became more uniform. These were attributed to the enhanced hydride formation and reduced contact between the Ta-hydride powders and air by wetting them. Therefore, an optimum amount of ethanol addition and milling time can enhance the formation of additional Ta-hydrides, while preventing oxidation during milling.     

Effect of processing parameters on the microstructure and thermal conductivity of diamond/Ag composites fabricated by spark plasma sintering

Diamond/metal composites with 50 vol.% diamond have been produced by spark plasma sintering (SPS) using pure Ag as a matrix and diamond particles as reinforcement. Three kinds of powder mixing processes were used to prepare the mixture of diamond/Ag powders: dry mixing without milling medium, wet mixing and magnetic blending. Subsequently, they were all consolidated by SPS at various processing parameters to produce bulk diamond/Ag composites. Then samples were heat treated in order to obtain a higher thermal conductivity. The effect of processing parameters on the morphologies of the mixed powders, the microstructure and the thermal conductivity of the composites were investigated by comparing the experimental data. It reveals that particles were easy to agglomerate and the distribution of mixed powders was inhomogeneous by dry mixing method, and wet mixing method is too complex. The most favorable mixing process is magnetic blending by which the powders can be homogenously mixed and the composites prepared by optimized SPS processing parameters can obtain the highest relative density and the best thermal conductivity among the composites prepared by different processes. The magnetic blending diamond/Ag composites even have a 23% increase in thermal conductivity compared with pure silver sintered by SPS.     

CNTs/SiC/Cu复合材料制备及性能

以碳纳米管(CNTs)、碳化硅(SiC)粉体、锌(Zn)粉和CuSO_4·5H_2O为主要原料,用化学镀的方法制备CNTs /Cu复合粉体,再采用非均相沉淀法制备CNTs/SiC/Cu复合粉体.在750 ℃、100 MPa的制度下进行真空热压烧结后制得CNTs/SiC/Cu复合材料,其中Cu的含量(体积分数,下同)为70%,CNTs的含量(体积分数, 下同)分别为0,3%,5%,8%,12%.利用XRD、SEM分析样品的物相组成和显微结构;利用阿基米德排水法、显微硬度计、三点弯曲法测试了复合材料的密度、显微硬度和抗弯强度.结果表明,随着碳纳米管含量的增加,CNTs/SiC/Cu复合材料的密度、显微硬度和抗弯强度等性能发生相应变化,其中,抗弯强度呈现逐渐升高趋势.与未添加碳纳米管的30SiC/70Cu复合材料相比,添加12%CNTs的12CNTs/18SiC/70Cu 样品,抗弯强度提高了21.45 MPa.     

SnO2表面改性对Ag/SnO2复合粉末烧结组织及性能的影响

采用沉积法和蒸发法分别对SnO2粉末进行WO3、Bi2O3 CuO表面改性处理,并用化学镀方法制备Ag/SnO2复合粉末.通过粉末冶金的方法对Ag/SnO2复合粉末进行烧结实验,并通过光学显微镜、扫描电镜观察烧结体的金相组织及复合粉末的形貌,对SnO2表面改性方法及添加剂种类对Ag/SnO2烧结性能和组织的影响进行了研究.结果表明:沉积法改性使烧结体组织中的SnO2分布更均匀,且能明显提高烧结体Ag/SnO2的致密度.Bi2O3 -CuO改性可消除SnO2的网络状分布,而WO3改性则显著改善电弧侵蚀后的表面组织.     

水合肼还原铜氨废液制取纳米铜粉

以铜氨废液为原料,水合肼为还原剂制备纳米铜粉。在水合肼浓度为3mol／L、pH值为10．0、温度为75℃的条件下,铜离子沉淀率可达98．66％。采用X射线衍射仪对铜粉进行了表征,并讨论了制备条件对纳米铜粉的影响。     

非均相沉淀-煅烧法制备La2O3包覆ZrC纳米复合粉末

以La(NO3)3.6H2O、氨水和ZrC为原料,采用非均相沉淀-煅烧法制备La2O3包覆ZrC复合粉末。采用XRD、SEM、EDS等检测方法,对包覆前驱体粉末和La2O3/ZrC复合粉末的成分、结构和组织均匀性进行表征。结果表明:前驱体粉末在750℃下煅烧2 h后,全部转化为La2O3,粉末为近球形,未发生长大;La2O3/ZrC复合粉末的粒径为60～80 nm;包覆后粉末的Zeta电位由48.28 mV变为5.376 mV,ZrC被连续且均匀的La2O3纳米级壳体层包覆。     

饰用钨基合金粉末的高速压制成形规律试验

以WC-Ni-Cr_3C_2-P系合金粉末为研究对象,通过密度测试、SEM断口形貌分析等手段研究了粉末粒度配比、预热处理、压制能量、高径比、质量能量密度等工艺参数对生坯密度、烧结密度、弹性后效、烧结径向收缩率等成形性能指标的影响规律。研究结果表明:粗WC颗粒(2μm)与细WC颗粒(0.4μm)相互搭配的WC-Ni-Cr_3C_2-P系合金粉末具有更好的成形性能;预热处理不能改善该系合金粉末的成形性能;未添加石蜡作为有机成形剂会出现生坯开裂的情况,能保证成形的压制能量范围较窄,但在生坯密度和烧结密度两方面均比添加有机成形剂时更高,实测压制能量为1425 J时,未添加有机成形剂的生坯密度和烧结密度分别达到10.67和13.48 g·cm~(-3),而添加有机成形剂的生坯密度和烧结密度分别只达到9.99和13.39 g·cm~(-3);生坯密度随质量能量密度的提高而提高,添加和未添加有机成形剂粉末的质量能量密度的临界点分别为101.79和118.75 J·g~(-1),质量能量密度超过临界点,并不能进一步提高生坯密度。     

Ni/Ti(C,N)包覆粉及其金属陶瓷的制备

采用非均相沉淀-热还原法制备Ni/Ti(C,N)包覆粉,并用该包覆粉经真空烧结制得金属陶瓷。利用扫描电镜、电子能谱、X-射线衍射等手段研究包覆粉的结构形貌及烧结后的微观组织与性能。结果表明:非均相沉淀过程中,非晶态的NiCO3·2Ni(OH)2·2H2O在Ti(C,N)颗粒表面成核并生长;经热还原过程后,NiCO3·2Ni(OH)2·2H2O分解并完全还原成Ni,Ni的平均晶粒尺寸约为50nm;采用包覆粉为原料制备金属陶瓷,有效改善了硬质相和粘结相的分布均匀性,但包覆粉烧结过程中存在晶粒长大现象;金属陶瓷的相成分为纯净的Ti(C,N)与Ni两相;金属陶瓷的综合性能相对于传统工艺制得的金属陶瓷有一定提高。     

Preparation of nanosized W／Cu composite powder by sol-gel technique

1 Introduction W/Cu alloys have been widely used in variousapplications, such as welding electrodes, heat sinks and spreaders due to their high thermal and electrical conductivity, high arc erosion and low thermal ex-pansion coefficient [1-2]. There are t…     

CTMAB萃取Au（CN2）2^—体系中盐析剂反常效应

研究了阳离子表面活性剂－萃取剂－惰性稀释剂－Au(CN)2^-体系萃金过程中盐析效应的规律。结果表明盐析剂的加入反而降低了金的萃取率。这说明盐析剂的作用机制与萃合物在负载有机相中的存在状态及结构密切相关。盐析剂的加入降低了水相中水分子的活度,不利于生成有机相中以水分子为桥的CTMA^ ．H2O．TBP缔合大阳离子萃合物。对传统的溶剂萃取盐析效应提出了一些亲的观点。     

Microscopic mechanism in solvent extraction of Au（CN）2^- by cationic surfactant

1　INTRODUCTIONSince Mooiman, Miller et al[1, 2] reported theirinvestigation in 1983, solvent extraction ofAu(CN)-2 from alkaline cyanide solutions has beenan attractive project. In the recent years, thesestudies have been more and more explored, and therepresentative papers are listed in Refs.[3 17].The solvent extraction of Au(CN)-2 by surfac tant CTMAB(cetyl trimithyl ammonium bromide)has been studied. It is different from the solventextraction of Au(CN…     

低温等离子体聚合对超细陶瓷粉体的表面改性

利用低温等离子体聚合的方法在超细ZrO2及SiC粉体表面聚合了聚乙烯、聚苯乙烯以及聚甲基丙烯酸甲酯等不同的聚合物层。透射电镜(TEM)、热重(TGA)及漫反射红外光谱的结果表明3nm～8nm厚的聚合物膜存在于超细陶瓷粉体的表面。经低温等离子体聚合处理过的ZrO2粉体在有机载体中的分散性显著提高。液体石蜡体系中，经低温等离子体聚合处理过的ZrO2粉体体系的粘度要远远小于未处理的ZrO2粉体体系。     

马来酸酐对二硫化钼粉体的表面改性研究

二硫化钼(MoS2)是一类常用的无机耐磨填料,将其填充到聚合物基复合材料中之前,为提高其与聚合物之间的界面相容性,并防止发生团聚而影响分散性,需要对其进行表面改性.采用马来酸酐(MA)为改性刺,对MoS2粉体进行表面改性研究.改性后的MoS2粉体在非极性溶剂中的分散性提高,其悬浮液离心分离后,上层清液的浊度从215提高到234,活化指数从0.42提高到0.8,吸油量从0.68mL/g降为0.31mL/g,透水时间明显延长,表明改性后的MoS2粉体亲油性提高.探讨了改性机理,并采用FT-IR及XRD进行了结构表征,结果表明:MA水解产物中的羧基与MoS2表面的羟基生成氢键,并定向包覆在MoS2微粒表面上,而酯基具有亲油疏水性.