Effect of temperature and CH4/ZrCl4 molar ratio on ZrC layers deposited in a vertical-wall CVD system

Abstract

The synthesis of ZrC layers was performed in an in-house developed, vertical-wall chemical vapour deposition (CVD) system operating at atmospheric pressure. Zirconium tetrachloride and methane were used as zirconium and carbon sources respectively, with an excess of hydrogen as reducing agent. Argon was used to carry the vaporised ZrCl4 at 300 °C to the reaction chamber. The deposition of ZrC was carried out on graphite substrates at temperatures in the range of 1200 °C –1600 °C. The molar ratio of CH4/ZrCl4 was varied from 6.04 to 24.44. Response surface methodology was applied to optimise the process parameters for the deposition of ZrC. A central composite design was used to investigate the effects of temperature and molar ratio of CH4/ZrCl4 on the average crystallite size. Quadratic statistical models for crystallite size was established. Scanning electron microscopy (SEM) images show that the coatings became more uniform with increased particle agglomeration as temperature increased.