预处理对共沉淀Si_3N_4-Al_2O_3-Y_2O_3复合粉体的影响

Influence of Pretreatment on Silicon Nitride Composites from Coprecipitation Coated Powders

利用FTIR、SEM,TEM等手段,研究了预处理对Si_3N_4粉体表面基团、Zeta电位以及共沉淀法制备Si_3N_4-Al_2O_3-Y_2O_3复合粉体形貌的影响。结果表明:Si_3N_4粉体通过酸洗+950℃预氧化处理后,可以在粉体表面形成硅氧烷(Si-O-Si)基团,硅氧烷基团在强碱环境下水解为硅烷醇(Si-OH)基团,所得基团有利于吸附Al^+和Y^+离子;预处理使粉体的等电点向左偏移,当酸洗+950℃预氧化处理后,粉体的p H_(IEP)<2,粉体Zeta电位在p H=9时达到-65 m V;酸洗+950℃预氧化处理后共沉淀粉体经过950℃煅烧可以制备出S_3N_4-Al_2O_3-Y_2O_3复合粉体,其中复合粉体中Al_2O_3和Y_2O_3的颗粒尺寸在20~100 nm。

Two types of commercial silicon nitride powders with poor dispersibilities were studied, and influences of acid leaching and 950 °C thermal oxidation on the coprecipitation for the powders were investigated. The evolution of nano-oxides during the reaction causes precipitation of the product, and the calcination of this precipitation gives nanocomposites powders(Al_2 O_3-Y_2 O_3) extremely fine, uniform grains, and phase domains. Microstructure of the composites were investigated by scanning electron microscopy(SEM),(TEM) and Fourier Transform infrared spectroscopy(FTIR). The peak of the Si-O-Si groups emerge at higher frequencies after thermal oxidation, and the isoelectric point of 950 °C thermal oxidation powders is found to be less than 2. For the coprecipitation powders, the size of Al_2 O_3-Y_2 O_3 composites powders is 20~100 nm.