采用等离子喷涂技术制备了5wt% CNTs/Al2O3-TiO2复合涂层, 借助SEM、热红联仪和RAM反射率测试系统对CNTs/ Al2O3-TiO2复合涂层的组织结构、高温氧化性能、电磁特性进行了分析. 结果表明:CNTs/Al2O3-TiO2复合涂层的组织结构致密、孔隙率低, CNTs分散均匀, 碳纳米管与Al2O3-TiO2陶瓷粘结剂之间具有良好的界面相容性. 在20~700℃高温氧化过程中, CNTs起始失重温度为471.29℃, CNTs/Al2O3-TiO2复合涂层的高温氧化性能有一定提高, 起始失重温度从471.29℃提高到507.8℃, 而碳纳米管的失重率从100%下降到33.68%. CNTs/Al2O3-TiO2复合涂层具有较好的高温吸波性能, 25℃时复合涂层的反射率峰值为-7.86dB. 随温度的升高, CNTs/Al2O3-TiO2复合涂层的反射率峰值不断减小, 谐振频率向低频移动, 300℃时复合涂层的反射率峰值为-12.88dB, 小于-5dB频带宽为4.48GHz.
5wt% CNTs/Al2O3-TiO2 coatings were prepared by micro-plasmaspraying. 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 processfrom 20℃ to 700℃, the initial weight loss temperature of CNTs was 471.29℃. Theinitial 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 losswas -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 band width for less than -5dB was 4.48 GHz at 300℃. There sults suggests that CNTs/Al2O3-TiO2 coating is agood candidate for high-temperature microwave-absorbing material.
参考文献
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