Improvement dielectric and microwave properties of SiCf/SiC-AlPO4 composites prepared by precursor infiltration and pyrolysis process

SiCf/SiC-AlPO4 composites were prepared with dual matrix precursor of polycarbosilane and aluminum dihydrogen phosphate during the PIP process to optimize the dielectric and microwave absorption properties at 8.2-12.4 GHz. Both complex permittivity and tanδ of the composites with simplex SiC and dual SiC-AlPO4 matrix show obvious sensitive behavior with the test frequency. The SiCf/SiC composites exhibit poor reflection loss values owing to the deviation of impedance matching caused by the high complex permittivity. With introduction of AlPO4 into SiCf/SiC composites, the complex permittivity decreased to proper levels and the microwave absorption properties are significantly improved over the whole test frequency ranges. The results indicates that the minimum RL values and bandwidth below −10 dB for the SiCf/SiC-AlPO4 composites reach-22.8 dB and 4.2 GHz, respectively.