The effect of temperature on the growth and properties of chemical vapor deposited ZrC films on SiC-coated graphite substrates

SiC and ZrC are critical and essential materials in TRISO coated fuel particles since they act as protective layers against the diffusion of metallic and gaseous fission products and provide mechanical strength for the fuel particles. However, SiC and ZrC have critical disadvantages in that SiC loses its chemical integrity by thermal dissociation at high temperature and the mechanical properties of ZrC are weaker than those of SiC. In order to address these problems, we made new combinations of ZrC coating layers and deposited them on SiC using a chemical vapor deposition process. We varied the growth temperature to optimize the growth conditions and analyzed the changes of the microstructure, chemical composition, and mechanical properties of the ZrC films. The deposition temperature was varied from 1200 to 1500 °C and ZrC changed from a whisker structure to a film at a temperature of 1400 °C. The preferred orientation was changed from the (111) plane to (220) and the chemical composition became stoichiometric. Also, the hardness and elastic modulus of ZrC increased when it was deposited at a higher temperature.