EFFECT OF SOURCE GAS-COMPOSITION ON THE SYNTHESIS OF SIC C FUNCTIONALLY GRADIENT MATERIALS BY CVD/

SiC/C composite layers with various compositions were deposited on gra phite substrates by chemical vapor deposition. The effects of the C/[C + Si] and H-2/[C + Si] ratios in the source gas on the composition, g rowth rate, preferred orientation and morphology of the deposited laye rs were studied. It was revealed that the C/[C + Si] as well as H-2/[C + Si] ratios in the input gas affected the carbon content of the depo sited film. SiC/C functionally gradient materials (FGMs) were prepared on the basis of conditions established by the deposition of the SiC/C mixed phase. It turned out that the CH4-SiCl4-H-2, C3H8-SiCl4-Ar and C3H8-SiCl4-Ar-H-2 systems were suitable for the deposition of SiC-rich layers, C-rich layers and layers in between, respectively.