Preparation of AlN powders from precipitated precursor

A homogenous mixture precursor of Al_2O_3+C was prepared by the chemical precipitation method and AlN powders were fabricated by carbon thermal reduction nitridation of the precipitated precursor.The effect factors on the nitridation conditions and the properties of AlN powders,including nitridation temperature,pH value,surface active agent,solution concentration,N_2 flow rate and molar ratio of carbon to aluminum,were investigated.An optimal process was obtained through synthesizing fine and pure AlN powders.Firstly,a homogenous and good dispersion precursor was prepared by the precipitation process using 0.4mol/L Al(NO_3)_3 solution and 156m~2/g carbon black as materials at pH=9,the molar ratio of carbon to aluminum was controlled to 3∶1 and a certain(amount)of stearic acid and ethylene glycol was added as surface active agents.Then,the precursor was heated at(1550℃) for 4h under common pressure at N_2 flow rate of 5L/min.Finally,AlN powders with nitrogen content of(33.20%,) oxygen content of 0.98%,specific surface area of 4.26m~2/g were produced after decarbonization of the nitridation products in air for 4h at 650℃.