摘要
提出了一种新颖的快速制备高比表面氧化铈纳米粉体的方法——盐助溶液燃烧法，通过XRD、TEM和比表面积分析，研究了燃料，氧化剂的比率、不同盐的种类和用量对产物性质的影响。研究发现，在传统的溶液燃烧法中简单的引入KCl导致产物比表面积由14．10m^2·g^-1剧增到156．74m^2·g^-1，得到了4-6nm高分散性的纳米氧化铈粒子。通过示意图初步讨论了盐助溶液燃烧合成过程高分散纳米氧化铈粒子形成的可能机制，认为由于自蔓延溶液燃烧反应快速释放出大量的热量，使反应体系产生瞬间高温，盐会迅速在新形成的纳米晶的表面原位析出形成薄盐层，当快速冷却后，氧化铈纳米晶就被镶嵌在凝固的盐基质中，阻止了新生成纳米粒子的重新团聚和烧结，从而得到氧化铈单分散粒子。
A novel salt-assisted combustion process with ethylene glycol as a fuel and nitrate as an oxidant to synthesize high surface area ceria nanopowders was presented. The effects of various tunable conditions such as fuel-to-oxidant ratio, type of salts, and amount of added salts on the characteristics of the asprepared powders were investigated by X-ray diffractionmetry, transmission electron microscopy and BET surface area measurement. It was verified that the simple introduction of leachable inert inorganic salts as an excellent agglomeration inhibitor into the redox mixture precusor leaded to the formation of well-dispersed ceria particles with particle size in the range of 4 - 6 nm and a drastic increase of surface area. The presence of KCl was found to result in an over ten-fold increase in specific surface area from 14.10 m^2·g^-1 for the ceria powders via the conventional combustion synthesis process to 156.74 m^2·g^-1 for product by the salt-assisted combustion synthesis process at the same molar ratio of ethylene glycol-nitrate. Finally, a mechanism scheme was proposed to illustrate the possible formation processes of well-dispersed ceria nanoparticles in the saltassisted combustion synthesis. We suggest that since the self-propagating solution combustion reaction releases large amount of heat in a very short time, resuiting in an instant high temperature of the reaction system, the salt precipitation in situ is completed in an instant to form a thin layer of salt crust on the surface of the newly formed ceria nanoparticles. After the rapid cooling, the salt-coated ceria nanoparticles are trapped into the frozen sah matrix, which prevents the re-agglomeration and sintering of the newly formed crystallites and results in yielding the well-dispersed ceria nanoparticles.
出处
《中国稀土学报》
CAS
CSCD
北大核心
2006年第4期408-413,共6页
Journal of the Chinese Society of Rare Earths
基金
国家自然科学基金青年基金资助项目(50306008)
总装备部预研项目(41328030507)资助
关键词
盐助
溶液燃烧法
纳米氧化铈
乙二醇
高比表面积
稀土
salt-assisted
combustion synthesis
ceria nanopowders
ethylene glycol
high specific surface area
rare earths
