Microwave absorption and mechanical properties of SiCf/SiOC composites with SiO2 fillers

Owing to the polysiloxane (PSO) characteristic of cheap, healthy, available and low free carbon content, in this research the SiCf/SiOC composites were manufactured by polymer infiltration and pyrolysis (PIP) method with various content of SiO2 fillers. It can be concluded from the DSC-TGA and XRD analysis that SiOC ceramic was formed from PSO when pyrolysis temperature exceeded 800 degrees C and after pyrolysis at 1000 degrees C the PSO mainly composed by amorphous SiO2. The effects of SiO2 fillers on morphology of SiOC matrix, flexural strength, complex permittivity, and microwave absorption property of SiCf/SiOC composites were investigated. The results indicated that the SiO2 fillers can enhance the density and reduce the microcracks of matrix. Therefore, the maximum flexural strength 201.09 MPa can be obtained by adding 5 g SiO2 filler into PSO precursor solution. The complex permittivity and flexural strength of composites first increased when content of SiO2 filler enhanced from 0 to 5 g. Nevertheless, with the content of SiO2 filler increased from 5 g to 10 g and 15 g, the complex permittivity and flexural strength of composites decreased. In summary, the SiCf/SiOC composites with 10 g SiO2 fillers not only possess the reflection loss as low as -26.02 dB and the effective absorption bandwidth (EAB) below -10dB up to 3.21 GHz at the thickness of 3.0 mm but also own the flexural strength of 171.71 MPa.