Deposition Kinetics of the Cristobalite Aluminum Phosphate Coating on SiC Coated Carbon/Carbon Composites Prepared by Hydrothermal Electrophoretic Technique

摘要

Cristobalite aluminum phosphate (C-AlPO_4) coatings were prepared by hydrothermal electrophoretic process on SiC coated C/C composites at different temperatures. The as-prepared C-AlPO_4 coatings was characterized by SEM analyses. The influence of hydrothermal deposition temperature on the microstructures of the as-prepared coatings and the deposition kinetics mechanism were investigated. Results show that dense and homogeneous C-AlPO_4 coatings on SiC coated C/C composites can be achieved at 373K and 220V deposition voltage; Kinetics investigations show that the deposition process of the C-AlPO_4 coatings on SiC coated C/C composite is controlled by the diffusion rate of the charged C-AlPO_4 particles to the cathode; the deposition rate increases with the increase of hydrothermal temperature. The diffusion equation and the kinetic expression of coating process follow the Fiek's second law and Ahrennius relationship. The deposition activation energy of the C-AlPO_4 coatings fabricated by the hydrothermal electrophoretic process is calculated to be 21.88kJ/mol.