Preparation and electrochemical properties of nanosized tin dioxide electrode material by sol-gel process

1　INTRODUCTIONTinoxideisawideenergy gapsemiconductorandhasfoundmanytechnologicalapplicationssuchascatalystsforoxidationoforganics,solid stategassen sorsandopticalelectronicdevices[1,2 ] .Recently ,sev eraltin oxide basedcompoundswerereportedtobegoodcandidatesasanodesforlithiumionbatteriesin steadofcarbonaceouselectrodes[36 ] ,theelectro chemicalreactionoccurringinthesecompoundsisnottheintercalationoflithiumintoahoststructure .Forbulksamplesofamorphousandcrystallinetinoxide ,adecomposition…     

柠檬酸盐凝胶法制备纳米晶SnO2的络合过程及其相结构研究

以SnCl2和柠檬酸为前驱物，无水乙醇为溶剂制备了纳米级SnO2。采用红外光谱（FTr—IR）、XRD和TEM测试技术研究了产物的络合过程和组织结构。结果表明，制备过程中形成了柠檬酸锡，其结构特征主要为双齿配位，部分为桥式配位，热处理后的粉体为10nm左右的分散性良好、尺寸分布均匀、具有优良热稳定性的金红石SnO2，形貌为等轴晶。     

Preparation of silver tin oxide powders by hydrothermal reduction and crystallization

Silver tin oxide composite powders were synthesized by the hydrothermal method with a silver ammine solution and a Na2SnO3 solution as raw materials. H2C2O4 was used as the co-precipitator of silver ions and tin ions. The co-precipitation conditions were investigated. The results show that the co-precipitate of Ag2C2O4 and Sn（OH）4 is available when the pH value of the solution is 4.27-8.36. Using the obtained precipitate as precursor,the reduction of Ag＋ and the crystallization of tin oxide were carried out simultaneously by the hydrothermal method and silver tin oxide composite powders were obtained. The composite powders were characterized by X-ray diffraction （XRD） analysis,scanning electron microscope （SEM）,and energy spectrum analysis. The results show that the silver tin oxide composite powders are small with a diameter of about 2 μm and with homogeneous distribution of tin.     

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.     

反应合成银氧化锡电接触材料导电性能研究

采用反应合成技术和传统粉末冶金技术制备银氧化锡(AgSnO2)电接触材料。对AgSnO2块体材料进行导电率测试和X射线衍射分析，对块体材料及冷拉拔的AgSnO2线材进行显微组织分析(扫描电镜、透射电镜)。研究结果表明：采用反应合成技术可以在银基体中合成尺寸细小、界面新鲜的SnO2颗粒，制备AgSnO2电接触材料；反应合成法制备的AgSnO2材料中，微米级的SnO2颗粒系由纳米级的SnO2颗粒聚集而成；反应合成法制备的AgSnO2电接触材料较传统粉末冶金法制备的AgSnO2电接触材料具有更高的导电性；采用反应合成法制备的AgSnO2电接触材料由于改变了Ag和SnO2的结合状态使材料的加工性能和导电性能同时得到改善和提高。     

Effect of Convection Gas on the Synthesis of Nanophase Tin Oxides During a Gas Condensation Method

Tin oxide powders of nanometer size have been synthesized by a gas condensation method using helium or a mixture of oxygen and helium as the convection gas. Changes in the average size, morphology, and crystal phases were investigated during heat treatment at temperatures between 350°C and 720°C in the air. Spherical tin oxide powders of 15 nm in average diameter were synthesized in a helium atmosphere, which was composed of Sn, SnO, and Sn₂O₃ phases. After annealing at 720°C, these multiphase particles transformed to a single SnO₂ phase and became an irregular shape of about 50 nm in diameter. This rapid coarsening was attributed to fast mass transfer among particles. The spherical SnO₂ powder of 7 nm in average diameter was directly synthesized using a gas mixture of oxygen and helium. Upon annealing up to 720°C, morphological changes were barely observed in the powder synthesized using a convection atmosphere containing oxygen.     

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.     

A Novel Method for the Preparation of Ag/SnO2 Electrical Contact Materials

描述了一种制备Ag/Sn O2电接触材料(Sn O2的质量分数为12%)的新方法。首先采用共沉淀法制备Ag-Sn O2纳米复合粉体(Sn O2的质量分数为42%)并对该Ag-Sn O2纳米复合粉体进行了表征。XRD结果表明制备的复合粉体由纯立方相的Ag和四方金红石相的Sn O2组成;SEM及TEM结果表明,纳米Sn O2与纳米Ag颗粒均匀弥散分布在复合粉体中;并借助于TG-DTA热分析对纳米复合粉体前驱体的制备过程进行了分析。然后,将Ag-Sn O2纳米复合粉体与Ag粉混合,采用粉末冶金法制备成Ag/Sn O2电接触材料,并对制备的Ag/Sn O2电接触材料进行了表征。结果表明,由于纳米Sn O2在Ag基体中弥散分布,制备的材料的物理性能如密度、硬度及电导率比普通工艺制备的材料好。     

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.     

Improvement of surface finish on SKD steel using electro-discharge machining with aluminum and surfactant added dielectric

Electrical discharge machining (EDM) process is widely used to process hard materials in the industry. Electrical discharge distribution effects can be achieved by the addition of Al powder in the dielectric. A fine surface roughness value of the workpiece is thus obtained. However, the electrostatic force among fine Al particles is found to agglomerate the Al powders in the dielectric. A surfactant can be adopted to separate the Al powder in the dielectric homogenously. A better surface even the mirror-like quality of the EDMed workpiece is thus desired. In the study, the effect of surfactant and Al powders added in the dielectric on the surface status of the workpiece after EDM is investigated.It is observed the best distribution effect is found when the concentrations of the Al powder and surfactant in the dielectric are 0.1 and 0.25 g/L, respectively. An optimal surface roughness (Ra) value of 0.172 μm is achieved under the following parameter—positive polarity, discharge current 0.3 A, pulse duration time 1.5 μs, open circuit potential 140 V, gap voltage 90 V and surfactant concentration 0.25 g/L.The surface roughness status of the workpiece has been improved up to 60% as compared to that EDMed under pure dielectric with high surface roughness Ra of 0.434 μm.     

报废银钨触头回收银和钨的工艺研究

银钨合金触点是重要的电接触材料,报废银钨触点中银钨的分离和资源化问题引起了越来越多的重视.以报废银钨触头为原料,提出了“一次分银-焙烧-二次分银”的回收工艺,考察了银钨分离的工艺条件,通过实践验证了其可靠性,银、钨的回收率达到99％以上.回收得到的银和钨可分别深加工成粒度为0.3～0.6 μm的超细银粉和纯净的WO3产...     

Effect of Sn~(4+) content on properties of indium tin oxide nanopowders

Indium tin oxide(ITO)nanopowders were prepared by a modified chemical co-precipitation process.The influence of different SnO2 contents on the decomposition behavior of ITO precursors,and on the phase and morphology of ITO precursors and ITO nanopowders were studied by X-ray diffractometry,transmission electron microscopy and differential thermal and thermogravimetry analysis methods.The TG-DSC curves show that the decomposition process of precursor precipitation is completed when the temperature is close to 600 ℃and the end temperature of decompositionis somewhat lower when the doping amount of SnO2 is increased.The XRD patterns indicate that the solubility limit of Sn4+ relates directly to the calcining temperature. When being calcined at 700℃,a single phase ITO powder with 15%SnO2(mass fraction)can be obtained.But,when the calcining temperature is higher than 800℃,the phase of SnO2 will appear in ITO nanopowders which contain more than 10%SnO2.The particle size of the ITO nanopowders is 15-25 nm.The ITO nanoparticles without Sn have a spherical shape,but their morphology moves towards an irregular shape when being doped with Sn4+.     

SnO2纳米颗粒的水热法和溶胶-凝胶法制备及其气敏特性

通过不同条件的水热法和溶胶-凝胶技术分别制备了单分散SnO2纳米粉体。利用X射线衍射、透射电子显微镜和比表面积分析仪对产物进行了检测,采用静态配气法测试了样品的气敏性能。结果表明,水热时间越长,颗粒尺寸越大,以反应时间为6 h制备的粉体比表面积最大;溶胶-凝胶产物中,以SnCl2的乙醇溶液为原料制得的颗粒克服了热处理过程中产物易团聚的问题,颗粒尺寸均匀,具有良好的分散性和较高的比表面积。两种方法制备的粉体均对酒精具有良好的灵敏度,SnCl2的乙醇溶液为原料、溶胶-凝胶技术获得的材料对酒精的灵敏度更高,并认为热处理过程中Cl-的去除是导致材料气敏性能不同的主要因素。     

Internal Oxidation Thermodynamics and Isothermal Oxidation Behavior of AgSnO2 Electrical Contact Materials

研究了Ag-Sn合金内氧化热力学与恒温氧化行为。热力学计算结果表明,Ag-Sn合金内氧化在热力学上是可行的,并绘制了合金氧化热力学区位图。经氧化实验获得Ag-Sn合金恒温氧化行为曲线。Ag-Sn合金快速氧化的温度区间为550℃至800℃。随内氧化温度的升高,合金的氧化更为彻底并逐步趋于平稳。实验所得AgSnO2材料中,SnO2颗粒弥散分布于Ag基体中。在内氧化过程中,氧的扩散使合金内部发生氧化,并生成呈网状排布的氧化物。     

反应合成AgSnO_2中SnO_2颗粒形成机制分析

通过热力学等计算得出AgSnO2材料中SnO2颗粒的临界形核半径等数据,以此为依据对反应合成法制备AgSnO2材料过程中SnO2颗粒的形核以及生长机制进行分析.结果表明:SnO2颗粒在成长过程中受到基体中Sn元素扩散以及基体颗粒尺寸因素的控制.反应合成法制备的AgSnO2材料中SnO2颗粒的尺寸大多处在约50 nm直径的范围,部分区域中由于Sn的缺陷扩散影响,出现了尺度在200 nm左右的较大SnO2颗粒,由于最后一批形核的SnO2颗粒缺乏Sn的补充,所以反应合成法制备的AgSnO2材料中存在直径在10 nm左右的纳米级SnO2颗粒.     

Agglomerate control in the complexing sol-gel process

lINTR0DUCTIONClassifiedinterms0fformationmechanismsofsolandgel,thesol-gelprocessincludesthreetypes:conventionalcolloidalsol-gel,inorganicpolymericsol-gel(i.e.,hydrolysisofmetalalkoxides),andcomplexingsoLgel['J.Fortheinorganicpolymericsol-gelpr0cess,differenceofhydroIysisrateamongdifferentalkoxidesusuallyleadst0poorhomogeneity,sooneproblemwiththisprocessisthehighercostasaresultofex-pensivechemicalsandinconvenientpreparation...diti...[2].Thisproblemcanbesolvedbyus-ingthec0mplexingsol-gelpro…     

纳米AgSnO2触头材料的制备与组织分析

利用高能球磨技术制备纳米AgSnO2粉末，热压烧结后，制得纳米AgSnO2块体，与传统内氧化法制得的AgSnO2InO3比较表明，高能球磨法能够克服内氧化法氧化物的聚集及晶界处析出的缺陷，得到SnO2均匀分布于Ag基体上的组织结构。     

Cu基电触头用掺杂SnO2纳米粉体的制备

利用溶胶-凝胶工艺制备了Cu基电触头用TiO2掺杂SnO2纳米粉。实验时,首先采用TG-DSC方法对掺杂SnO2前驱体在升温过程中的转变过程进行了分析,然后采用XRD对不同温度焙烧所得掺杂SnO2粉体进行了物相分析、颗粒粒径计算,采用TEM对掺杂SnO2粉体的微观形貌进行了观察,最后通过分析掺杂SnO2粉体晶格参数d值的变化对粉体的掺杂效果进行了评估。结果表明:通过所述工艺成功实现了TiO2对纳米SnO2的掺杂,500℃焙烧所得掺杂SnO2为圆球形,粒径约为10 nm,较好地满足Cu基电触头材料使用的需求。     

半导体金属氧化物的室温固相合成及其气敏特性研究

以无机盐为原料，在遵守热力学及动力学限制的前提下，对一定摩尔比的反应物进行研磨，使其发生室温固相化学反应而合成了SnO2,In2O3,ZnO,Fe2O3等半导体金属氧化物的纳米粉体，用XRD，TEM测试手段对产物的物相和微观结构进行了表征和分析。结果表明，固相化学反应完全，所得产物为理论产物，且平均粒径小于100nm，气敏性能研究结果表明，用该法制备的SnO2,In2O3元件对酒精，LPG气体有一定的灵敏度和选择性，而ZnO,Fe2O3气敏性能却较差。     

Bulk Al/SiC nanocomposite prepared by ball milling and hot pressing method

Nano-sized Al/SiC powders were prepared by mechanical alloying method. Two sorts of SiC particle, i.e., nano-sized and popular micron-sized SiC were utilized. The particle size and microstructure of the milled powder were characterised. Effects of the particle size and agglomerate state of SiC, as well as the microstructure of Al/SiC nanocomposite were studied by SEM and TEM. The results show that nano-sized SiC particles is dispersed in aluminium uniformly after ball milled for only 2 h, whereas the similar process need about 10 h for popular micron-sized SiC particle. The bulk Al/SiC nanocomposite can be fabricated by hot pressing the nano-sized Al/SiC powders at temperature about 723 K under pressure of 100 MPa.