Study On Synthesis And Microwave Absorptivity Of SiC_p-SiO₂ Composites

SiC shows superior performance, e.g., low density, high strength, anti-corrosive,etc. It is an important high temperature ceramic material and has been widely used in many fields. Nowadays, SiC composites have received considerable interests by many researchers for their advanced applications in microelectronics due to their excellent semi-conductive features. SiC fibers are always used as microwave absorbing materials. In this paper, dielectric properties of particulate SiC are investigated. Microwave absorbing behavior of SiC_p-SiO₂ composite is detected.SiO₂ was coated on SiC_p by sol-gel method. The deterrent factors such as the amount of H2O, pH value and reaction temperature on hydrolyzation rate were analyzed. DSC-TG technique was used to detect physical and chemical changes of the composite particles during the heating process. SiC_p-SiO₂ composites were prepared by conventional sintering. Some physical properties of SiC_p-SiO₂ compacts were analyzed. XRD and SEM were carried out to characterize the samples. The sintering mechanism and influence factors of SiC_p-SiO₂ composites were analyzed. Vector network analyzer was used to measure the electromagnetic parameter and reflectivity. The absorbing mechanism of SiC_p-SiO₂ composites was discussed.It was found that the heterogeneous-deposition and sol-gel method was the desired way to achieve the coated SiC_p-SiO₂ composite particles. SiC_p and SiO₂ dispersed homogeneously within the composite powders. Spherical SiC particles facilitated the coating process. Excess water is shown to accelerate the hydrolyzing rate of tetraethyl orthosilicate (TEOS). Two step sol-gel method with acid catalyzer first and then alkali, is an effective way to reduce the reaction time. Maximum density of 2.03g/cm³ appears at 1400℃ for 70SiC_p-30SiO₂ (in volume percentage) composites. The absorbing property of SiC_p-SiO₂ compacts is superior than that of SiC_p-SiO₂ composites with resin bonding.. Reflection attenuation reached to higher than -5dB within 12.4¹8GHz, the maximum was-10.3dB at 14.5GHzc...