Raman Spectroscopy and Microwave Absorbing Properties of CNTs/Al₂O₃-TiO₂ Composite Absorbing Coatings with Different Diameters

CNTs/AT13 composites were prepared by mixing Al2O3-TiO2 ceramics(AT13) and carbon nanotubes with different diameters in an ultrasonic bath.CNTs/AT13 coatings were prepared by micro-plasma spraying.Raman spectra of CNTs/AT13 composite powders and sprayed coatings with different CNTs diameters were studied. The values of D peak to G peak of the composite coatings increased compared with CNTs/AT13 composite powders. With increasing the diameter of CNTs,the ratio of D peak to G peak of the composite coatings is smaller and the graphitization degree of CNTs was higher.The microwave absorbing properties of the sprayed CNTs/AT13 coatings with different thicknesses were investigated in the frequency range of 2–18 GHz.when the coating thickness is 1.0 mm,the microwave absorbing ability is poor.With thicker coating,the microwave absorbing ability of the CNTs/AT13 coatings are enhanced.When the coating thickness increases to 1.5 mm,with increasing of the CNTs diameters,the experimental reflectivity peak first decrease and then increase while the resonant frequency moves to the high frequency.The reflection peak of 30–50 nm CNTs/AT13 composite coating is –23.98 dB,and the fre quency bandwidth for less than –5 dB and –10 dB is 6.40 GHz and 3.36 GHz,respectively.With increasing diameters of CNTs,the frequency bandwidth for less than –5 dB decrease,the frequency bandwidth for less than –10 dB increase.When the coating thickness increases to 2.0 mm,the resonant frequency of the CNTs/AT13 composite coating moves to low frequency.