High Temperature Performance of Micro-plasma Sprayed CNTs/Al_2O_3-TiO_2 Composite Coating

5wt% CNTs/Al2O3-TiO2 coatings were prepared by micro-plasma spraying.Microstructure and high temperature properties of CNTs/Al2O3-TiO2 composite coatings were studied.Its microstructure was dense and the porosity was low.CNTs were dispersed uniformly in CNTs/Al2O3-TiO2 composite coating.In the thermal oxidation process from 20℃ to 700℃,the initial weight loss temperature of CNTs was 471.29℃.The initial weight loss temperature of CNTs/Al2O3-TiO2 composite coating was raised to 507.8℃.The plasma heating process improved the graphite phase transformation of CNTs,which was helpful for the improvement of initial weight loss temperature of CNTs/Al2O3-TiO2 composite coating.When CNTs/Al2O3-TiO2 composite coating was heated to 300℃,and the high temperature reflectivity was measured at 2 18 GHz,the minimum reflection loss was 7.86 dB at 25 ℃.With increasing temperature,the reflectivity peak continuously decreased and the resonant frequency moved to the low frequency.The experimental reflectivity peak was 12.88dB,and the frequency bandwidth for less than 5dB was 4.48 GHz at 300℃.The results suggests that CNTs/Al2O3-TiO2 coating is a good candidate for high-temperature microwave-absorbing material.