Studies On The Preparation And Microwave Absorbing Properties Of Vitrified Bonded SiC Composites

Electromagnetic wave attenuating materials have attracted enormous attention for their extensive applications in military and civli fields.The vitrified bonded SiC composites were prepared from SiC powders and vitrified bond.The microstructure,phase structure,mechanical properties,dielectric properties and microwave absorbing property of the composites were investigated.In the vitrified bond SiC composites,SiC particles are well wetted and coated by the glass,and few exposed SiC can be observed through the scanning electron microscope.The main crystal structure of the composites is SiC.As a result of the devitrification of the bonding glass,SiO₂ phases exist.The vitrified bonded SiC composites present high strength.When the SiC is ?-SiC of 5?m and the content of SiC is 70wt%,the flexural strength reached up to 71.06 MPa.The vitrified bonded SiC composites show tailored dielectric properties in X-band.The real part of the complex permittivity of the composites is high,and keeps increasing with increasing SiC content.The imaginary part of the complex permittivity of the composites is much lower and the content of SiC shows little tailor ability on it.The dielectric loss of the composites is under 0.2.Thecomposites present limited microwave absorbing property.When the SiC is ?-SiC of 10?m and the content of SiC is 90wt%,the reflect loss is-5.178 d B with 2mm thickness.The particle size and crystal form of SiC have no significant influence on mechanical and dielectric properties of the composites.When the SiC is ?-SiC of 5?m and the content of SiC is 70wt%,the flexural strength of samples sintered at 840°C is 71.06 MPa,much higher than samples sintered at800°C,760°C and 720°C.The sintering temperature has a significant tailor ability on the dielectric properties of the composites.The real part of the complex permittivity of the composites decreases as the sintering temperature rising.For the good mechanical property and characteristic dielectric properties,vitrified bonded SiC is appropriate for electromagnetic shielding applications and can find its position in multilayer electromagnetic absorption materials.