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Crystalline Sb doped tin oxide (ATO) , cassiterite structure , is a wide band gap n2type semiconductor. Because of its optical property (transparent for visible light and reflective for IR) and electroconductibility , good chemical and mechanical stability , it has many applications , such as transparent conductive electrodes , photovoltaic devices , photosensors , catalyst , antistatic coatings and electrochromic materials[1- 4 ] . A variety of techniques have been used to prepare ATO superfine powders , some involve dry processes , others are based on wet chemical processes , including chemical coprecipitation[5] , sol-gelrelated process[6] , emulsion method[7 ] . Compared with dry process , wet chemical process is a low-cost method to fabricate superfine powders. However , the process suffers the disadvantage of producing hard agglomerate during drying and calcining procedures due to the high surface tension stress , physically adsorbed and / or chemically coordinated H2O molecule , and hydroxyl group on hydrate particles surface. The key issue to decrease the agglomeration has been considered to decrease the tension stress and to remove the residual H2O molecule with maximum limit by proper dehydrating process[7 , 8 ] . The dehydrating methods adopted currently include refrigeration drying[9 ] , supercritical drying[10 ] , organic solvent washing and heterogeneous azeotropic distillating[11 ] . The former two kinds of methods which needs specialized equipments , are not used as widespread as the latter two , which are simple and easy to operate. The method of organic solvent washing mainly uses ethanol , isopropanol and acetone to substitute for H2O molecules remained in the gels , but this substitution is limited and the agglomeration can not be completely eliminated. Compared with organic solvent washing method , heterogeneous azeotropic distillation is a more effective anti-agglomeration method. But , up to now , the solvent used in heterogeneous azeotropic distillation mainly is n2butanol . No any other solvents are found to be utilized in the process , and also the report on the preparation of free agglomerate nanometer2sized powder with organic dehydrating agent are not found.. In the present study , nanometer-sized ATO powders are prepared through hydrolysis of metal alkoxides. In order to eliminate the agglomerate , an improved heterogeneous azeotropic distillation process , n-butanol/ xylene mixed solvent heterogeneous azeotropic distillation , and a kind of organic dehydrating agent are used in dehydrating procedure. This paper discusses the effect of the two dehydrating process , compared with other processes , on theproperties of ATO superfine powders. It is found that the n2butanol/ xylene mixed solvent heterogeneous azeotropic distillation process and organic dehydrating agent can effectively dehydrate , and obtain high performance nanoscaled ATO powders. |
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wang_xin
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上将王
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wypward(金币+1):谢谢参与，辛苦啦 2010-06-06 15:23:27
wypward(金币+1):谢谢参与，辛苦啦 2010-06-06 15:23:27
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向水晶体Sb中掺杂二氧化锡（ATO），锡石的结构，是一个宽频带的半导体。因为它的光学性能（对可见光透明并且反射红外线），导电性，很好的化学稳定性，有很多应用。例如透明的导电极，光电设备，感光器，触媒，抗静电涂层和电致变色的材料。有很多方法用来制备这种ATO超细粉体，一些涉及干法，其他的是湿化学过程法，包括化学共同沉淀，溶胶凝胶，乳浊液法。与干法相比，湿化学过程是低廉的方法制备这种超细粉体。然而，这个过程也遭受着不利因素，如在干燥和烧结易产生硬的结块，是由于表面高张应力，物理吸附和化学配合的水分子，水合粒子表面的羟基。关键问题在于减少团聚已经被认为是最大限度地降低张应力，去除残留的水分子通过合理的脱水过程。脱水方法采用一般包括冷冻干燥，超临界干燥，有机溶剂洗涤和不同的共沸物蒸馏。前两种需要特殊的器械，没有后两者使用广泛，后者则简单易于操作。有机溶剂洗涤主要用乙醇，异丙醇和丙酮，用于替代残留在凝胶中的水分子。但是这种替代是有限度的，所以结块仍然不能完全消除。与有机溶剂洗涤相比，不同的共沸物蒸馏是一个高效的抗结块方法。但直至今日，在不同的共沸物蒸馏使用的溶剂主要是丁醇。没有发现使用其他的溶剂，报道在制备无结块的纳米颗粒粉体所用的有机脱水试剂中也没有发现。目前的研究，纳米粒径的ATO粉体的制备是通过金属醇盐的水解。为了减小结块，一个改进的不同的共沸物蒸馏方法，丁醇混合溶剂的不同的共沸物蒸馏，一种有机脱水剂被用在脱水中。这篇文章讨论在超细ATO粉体中，两种脱水过程的效果，与其它的过程相比。发现丁醇/二甲苯混合溶剂的不同的共沸物蒸馏方法和有机脱水剂是有效的脱水，并获得高性能的纳米级ATO粉体。 累死我了，一句一句翻译的啊  |
2楼2010-06-06 13:43:37
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