Search

Si3N4/SiBCN composite ceramics were prepared by infiltrating and pyrolyzing liquid polyborosilazane in porous Si3N4 ceramics. To increase their wave-absorbing ability, SiC nanoparticles and SiC film obtained by chemical vapor infiltration were separately introduced into the composite ceramics. The surface morphology, element and phase composition of ceramics were analyzed by means of scanning electron microscopy, energy dispersive spectrometer and X-ray diffraction. Dielectric and electromagnetic wave absorbing property researches show that the permittivity and dielectric loss of the ceramics were effectively improved and the electromagnetic reflection coefficient was visibly decreased when SiC was loaded. It is indicated that SiC is an effective dielectric lossy absorbent, and the Si3N4/SiBCN composite ceramics containing SiC possess the great potential in the application of wave-absorbing material.

ZrC coatings were prepared by CVD using ZrCl4, C3H6, and H2 as the precursors. The mechanisms responsible for the effects of deposition temperature, H2 flow rate and inlet C/Zr ratio on the ZrC coatings were studied based on the deposition mechanism of ZrC. The results indicate that the ZrC morphologies change from a loose spherical structure to a cauliflower structure, then to a glassy structure as the deposition temperature increases from 1050oC to 1150oC, then to 1250oC. The carbon content in the ZrC coatings increases with increasing the deposition temperature. Higher inlet C/Zr ratio can lead to rough surfaces and higher carbon content. Reasonable H2 concentration can inhibit carbon deposition, and lead to a cauliflower structure.