Preparation For AIN Powder In Thermal Plasma

Preparation for aluminum nitride in thermal plasma is studied. The contents include that the calculation of plasma character in different operating parameters, the time scale of aluminum powder's heating in plasma, the experimental apparatus and the results of experiments. Compared to other methods,thermal plasma method(TPM) has many advantages such as the simpler apparatus, higher purity ,finer powder size and better dispersion. Because of the higher quality of the product prepared by this means, it can meet the requirement of electrical industry.This article is divided into five parts.In the first part, the methods and their developments of preparation for aluminum nitride are introduced, and TPM is compared to the main way such as carthermal reduction and direct nitridation synthesis process.In the second part, saha- equation and energy balance equation are used to calculate the dissociation and temperature of nitrogen and hydrogen in plasma, and the calculation results are shown for two kinds of typical conditions:(l)the nitrogen as discharge working gas and aluminum powder carrying gas ,their total volume is 2.1m3/h;(2)the hydrogen as discharge working gas, its volume is InrVh, and nitrogen as aluminum powder carrying gas, its volume is 0.6m3/h.In the third part, Fourier thermal conduction theory is used to calculate the time for the heating and evaporating aluminum powder. A model of four phase of heating of aluminum powder is set. The four time scales :ti,t2,t3,t4 are given. Here, t1 is the time spent on aluminum power's temperature rising from room temperature to the aluminum melting point,t2 is spent on aluminum power melting, t3 is spent onaluminum power's temperature rising from melting point to the boiling pointy is spent on evaporating. The results are given under the condition in different plasma gas such as nitrogen, hydrogen, argon and mixture gas(argon :hydrogen=l:4). The results show that the time scale of evaporation of aluminum in different plasma gas has a relation of hydrogen