LASER SYNTHESIS OF ULTRAFINE SI3N4-SIC POWDERS FROM HEXAMETHYLDISILAZANE

Ultrafine Si3Ni4-SiC powders have been successfully prepared from hexamethyldisilazane ((Me(3)Si)(2)NH) (Me drop- CH3) and NH3 by a laser-induced gas phase reaction. An optimization experiment aimed at increasing the Si3N4 content of the powders has been done with an orthogonal design of the main processing parameters, including the laser power and the gas flow rates of (Me(3)Si)(2)NH and NH3. The Si3N4 content of the powders has been raised to 70 wt.% and the corresponding processing parameters determined. The powders produced have been characterized by chemical analysis, transmission electron microscopy, IR spectroscopy and X-ray diffraction. They are white-grey in colour, free of hard agglomerates, of average particle size 20 nm and their chemical composition changed with the processing parameters.