Characterization of mechanical properties of chemical vapor deposited SiC by instrumented indentation technique

Abstract

The growth and characterization of silicon carbide has become of importance due to its wide applicability to nuclear fuel particles and MEMS structures. In particular, chemical vapor deposited cubic silicon carbide films seem to be most suitable materials for these purposes, owing to its high mechanical stability. In this study, silicon carbide films fro TRISO coated fuel particles and MEMS structures were fabricated by various chemical vapor deposition routes and those mechanical properties were investigated by the instrumented indentation technique. For TRISO coated fuel particles, low pressure CVD technique was used to fabricate the SiC films. The hardness, Young’s modulus, and strength of SiC films were successfully characterized with instrumented indentation technique. Furthermore, considering the operation temperature of TRISO coated fuel particles over $1000^\dcirc C$, high temperature hardness, modulus and creep properties were estimated with high temperature nanoindentation technique and impression creep analysis. For MEMS structures, high vacuum metal-organic chemical vapor deposition was used to produce silicon carbide films on silicon substrate. The contact damage of SiC/Si systems was investigated with the generation of controlled contact damages by instrumented indentation using various indenter tips. The indentation induced impression and cracks were analyzed with brittle fracture mechanics theory and the contact damage resistance of SiC/Si was evaluated. In order to simulate the contact damage mode, the finite element analysis method was used to reveal the stress field distribution and plastic deformation of materials at the surface and subsurface. The finite element analysis of the contact damages gives the useful information of damage evolution inside the coating and substrate. The subsurface damage of indented SiC/Si was observed with focused ion beam milling and cross sectional TEM observation. The fracture mode of contact damaged SiC/Si is ...