Enhanced microwave absorbance of oxidized SiCf/AlPO4 composites via the formation of a carbon layer on the SiC fibre surface

A single-layer radar-absorbing structure active in the X-band (8.2 GHz to 12.4 GHz) was demonstrated by blending SiC fibres with an AlPO4 matrix material. The as-prepared SiCf/AlPO4 composites were oxidized at 1273 K for several hours to investigate the effects of oxidation on the dielectric and wave-absorbing properties. Scanning and transmission electron microscopy were used to characterize the morphology and microstructure of the composites. The AlPO4-SiO2 solid solution during oxidation promoted the formation of a complete carbon layer on the SiC fibre surface. The real and imaginary parts of the SiCf/AlPO4 composites increased from 4.2-4.4 to 5.9-7.1 and from 0.08-0.2 to 3.9-5.2, respectively, with increasing oxidation time from 0 to 10 h, respectively. When the thickness of the composites increased from 2.9 mm to 3.3 mm, the wave-absorbing property noticeably improved due to the formation of a carbon layer on the SiC fibre surface after oxidation.