摘要
采用凝胶 超临界流体干燥技术制备无团聚ZrO2 (CaO)纳米粉体 ,考察主要工艺参数 初始水凝胶pH值对粉体化学组成、相结构、形貌、颗粒大小及分布等性能的影响。研究表明 ,超临界流体干燥技术可以有效地防止湿凝胶干燥过程中粒子间硬团聚现象的发生。该法合成的ZrO2 (CaO)粉体纯度高、成分准确 ;颗粒近似呈球形 ;粒径小 (5～ 2 0nm)、单分散性能好 ;粒子的比表面积大 ,活性高。
A major challenge in the processing of ceramic materials is to control powder synthesis and subsequent sintering to produce sintered compacts with both high density and ultrafine grain size. It has been demonstrated that utilizing nanocrystalline ceramic powders, coupled with attention to forming methods, has brought about enhanced sintering rates and low sintering temperatures, higher reliability, and improved mechanical and physical properties. A number of techniques, such as gas phase synthesis, spray pyrolysis, hydrothermal synthesis, and sol gel, have been used to make nanocrystalline ceramic powders. Aqueous chemical processes are the leading contenders among the low cost processes because it delivers monodisperse spherical powders for a wide variety of oxike ceramics, including pure and stabilized ZrO 2. Disadvantages of this method lie in the hard agglomeration of grains during drying and heat treatment processes. Supercritical fluid drying has been advocated as one of the effective chemical processing to produce ultrafine powders. Powders prepared by this method are soft agglomerates with large surface area and high pore volume, therefore, they have been widely used in the catalytic field. In the present work, Gel supercritical fluid drying technology has been employed to synthesize ZrO 2(CaO) nanometer sized powders with the low cost inorganic salts as starting materials. The influence of major parameter the pH value of the original hydrogel on the properties of ZrO 2(CaO) ultrafine powders was also investigated, including chemical composition, phase construction, morphology, particle size distribution etc. The experiments showed that supercritical fluid drying technology could effectively alleviate the hard agglomeration of grains during the gel drying process, with the result that the morphology of the ultrafine powder retained the network texture of the original gel. The ultrafine powder was characterized by its high purity, accurate composition, small particle size, better monodispersibility and high surface area. Moreover, our investigation suggested that the properties of ZrO 2(CaO) nanometer sized powders were sensitive to the pH value of the original hydrogel. With the increase of pH value from 5.5 to 10.5, the concentration of CaO in ZrO 2(CaO) solid solution increased from 1.3 to 15.2 mol.%, the mean particle size decreased from 14.6nm to 6.7nm, and the amount of metastable phases tetragonal and cubic zirconia increased gradually.
出处
《电子显微学报》
CAS
CSCD
北大核心
2003年第1期46-49,共4页
Journal of Chinese Electron Microscopy Society
