Influence of dip-coated MgO interphase on the mechanical and dielectric properties of 2D-SiCf/SiC composites

摘要

This work focused on the use of the dip-coating process to prepare magnesium oxide (MgO) coatings on silicon carbide fibers (SiCf) as an interfacial system for SiCf/SiC composites. The MgO coatings were prepared on KD-I SiCf using thermal decomposition of magnesium acetate tetrahydrate (C4H6MgO4 center dot 4H(2)O) in a vacuum furnace. The effect of the amount of C4H6MgO4 center dot 4H(2)O on the coating's microstructure and morphology, mechanical and dielectric properties of SiCf/SiC composites were investigated. The Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction results show that the coating's surface is relatively smooth and uniform as the content of C4H6MgO4 center dot 4H(2)O reaches 3 wt%. The SiCf/SiC composites containing an 0.18 mu m thick MgO interphase show improved mechanical properties in terms of flexural strength and failure displacement. Also the complex permittivity for composites with an MgO interphase is a little lower than the as-received composites because of the low electric conductivity of MgO. The effective microwave absorbing bandwidth (below -10 dB) for composites is in the range 8.8-11.5 GHz, and the minimal reflection loss reached -12.56 dB.