In this paper, for the purpose of industrial application of laser method, aimed to the question of high price of raw materials used in laser method to synthesis ceramic ultrafine powders, practicability research work has been done to choose cheap silicon containing organic compound to synthesis composite ceramic powders such as Ni_3N_4/SiC. In the article, through the study of characters of laser method, we have found the conditions which the reactant should satisfy with, and through the investigation and screen of great number of organic silanes, we have selected out some cheap organic silanes. Aimed to the question of gas flow inlet of liquid reactant, we have designed an evaporation apparatus which can produce steady and controllable gas flow. On the equipment of 2kwCO_2 laser, kilogram/day powder production rate apparatus and evaporation apparatus designed, using hexamethyldisilazan ((Me_3Si)_2NH) and ammonia as reactants, we have prepared Si_3N_4/SiC composite ultrafine powders, so that we have verified the practicability to use large molecular organic silanes to prepare composite ceramic powders. By using orthogonal experiment parameters, we have prepared high quality Si_2N_4/SiC powders which have regular shape, narrow size distribution, no agglormeration, average particle size of 20nm, Si_3N_4 content of 71%, and found the optimum experiment parameters. We have also used diethoxydimethylsilane ((CH_3)_2Si (OC_2H_5)_2) as reactant, adding ethane and oxygen respectively, having prepared SiC/SiO_2 powders having two different content of main phases, so that we have verified the practicability to use organic silanes to prepare SiC/SiO_2 powders. Through the analysis of the reaction characters of large molecular organic silanes such as low reaction temperature, the sensitive dependence of powder chemical composition on laser power, we have studied the reaction mechanism and presented the view of infrared multiple photon chemical reaction.
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