HIGH DEPOSITION RATE COATING WITH NANODISPERSE SIC POWDER BY PLASMA-ASSISTED PULSE PYROLYSIS

With regard to the development of a high deposition rate coating proce ss at low substrate temperatures, we investigated whether this can be realized by the formation of nanodisperse SiC particles and their depo sition in a one-step process. The SiC powders were obtained by plasma- assisted pyrolysis of tetramethylsilane (TMS) as particle precursor. O wing to a reduction in the amount of particles and the prevention of s ubstrate heating, the particles were formed by pulse pyrolysis at temp eratures of 1200-2000 K and at pulse times of 0.1-4 ms. The investigat ions were performed by means of a shock tube. The powders obtained are nanodisperse with particle sizes in the range below 40 nm consisting of variable contents of both amorphous SiC and crystalline beta-SiC Th e powders form very thin layers; a single pulse generates a layer with a thickness in the range 40-80 nm, determined by ellipsometric measur ements. The layers adhere on the substrate but because of a lack of de position energy their solidity and adherence on the substrate are not sufficient. Investigations were performed to increase the solidity of the layers by subsequent energy transfer to the layer.