Effect of holding time on microstructure, mechanical, water resistance and dielectric properties of alpha-cordierite glass-ceramic coating on porous BN/Si2N2O ceramic

摘要

alpha-cordierite glass-ceramic coating was prepared on the porous BN/Si2N2O ceramic by the glass-ceramic method at 1050 degrees C for 1-4 h. The effect of the holding time on the phase composition, microstructure, mechanical, water resistance and dielectric properties of the glass-ceramic coating was investigated. The resulting coating was mainly composed of alpha-cordierite and glass, and the a-cordierite content increased with increasing holding time. The coating/substrate interface was continuous without defects, and the glass liquid of the coating can infiltrated into the surface pores of the substrate. Additionally, the density and mechanical properties of coatings increased as the holding time increased. The obtained coated samples fabricated at 1050 degrees C for 2-4 h possessed a low water absorption (2.1-5%) and little open porosity (2.7-3.2%), demonstrating good water resistance. Furthermore, the coated samples prepared at 1050 degrees C for 3 or 4 h exhibited both low dielectric constant (4.1-4.3) and loss tangent (0.005-0.009) in the frequency range of 20-36 GHz.