Preparation And Compressive And Microwave Absorption Performance Of SiC Porous Materials

SiC porous materials are a kind of structural radar absorbing materials, which possess numerous merits, such as light weight,broad absorption band and efficient absorption ability. It has a great potential in microwave absorption field, especially in high temperature microwave absorption field. SiC porous materials should have excellent microwave absorption performance and mechanical properties when used as structural radar absorbing materials. In this paper, the microwave absorption properties and compressive properties of the fabricated SiC porous materials were investigated. In order to meet the requirement of practical application, the maximum compressive strength should be greater than 4MPa and the minimum reflection loss should be less than-10 dB.In our study, porous carbon materials were fabricated as a template, then the template of carbon was reacted with silicon source to obtain SiC porous materials. The best carbonizing temperature was 800 oC because the obtained carbon template had good compression resistance and reactivity ability. A well mixture powder of SiO2 and Si whose mole ratio being 1:1was used as silicon source. Afterwards, the carbon template and silicon source was sintered at the temperature of 1500 oC and maintained for 5h. If the porous carbon materials had internal silicon source, the reaction would be more complete. On account of detailed characterization on the component and microstructure of the final products by XRD, SEM, FIIR and Raman test, we found that the as-prepared SiC porous materials had similar porous structure with carbon template. The aperture could be controlled at the range of 5-150μm by changing the content of yeast and the porosity was about 70%. In addition, we found that a lot of SiC nanowires were formed in the open pores and porous channels of SiC porous materials. The SiC nanowires were beneficial to increase the compressive strength of SiC porous materials. Finally, the growth mechanism of SiC nanowires in SiC porous materials was also proposed.The compression resistance of SiC porous materials was better than the original carbon template, the maximum compression resistance could reach 9.8MPa. TG analysis demonstrated that SiC porous materials was stable when the temperature was elevated from 25 oC to 800 oC. The sample of SiC porous materials contained residual carbon was also stable at the temperature of 600 oC which demonstrated that SiC porous materials could be applied at high temperature condition. The microwave absorption of SiC porous materials was characterized in X-band at the temperature range of 25-700 oC. The microwave performance was promoted with the temperature increase and reached the best state in 700 oC. The reflection loss was under-12 d B and the minimum reflection loss was-34 dB at the frequency of 11.8GHz.