In Situ Synthesis And Properties Of Low Density O'-Sialon Multiphase Ceramics

Low density O'-Sailon multiphase ceramic was prepared successfully by using in situ synthesis technology. The effects of raw material composition, combinational sintering additives and sintering temperature on phase composition and microstructure were investigated by XRD and SEM. The nucleation and growth mechanism of O'-Sialon grains was discussed. The performance of sintering and the properties of mechanics and dielectric were studied.The ceramics that were made of clay or Al(OH)₃ as the Al source of raw material had little different effect on phase composition, but using clay was in favor of decreasing the pore ratio; Increasing the dosage of Al source in the raw material could improve sintering performance and the content of O'-Sialon. The true x value of O'-Sialon (Si_2-xAl_xO_1+xN_2-x) was refined by calculating the cell parameters and unit volume, the results shown that the x value could be enhanced by increasing the dosage of Al source.In order to improve mechanical property and decrease the pore ratio, combinational sintering additives of MgO+Y₂O₃ were investigated. Results indicated that combinational sintering additives could obviously enhance the content of O'-Sialon, promote mechanical property and decrease the pore ratio of the samples. A lot of column-like grains appeared in the samples from the microstructure analysis.The column-like grains were proved to be O'-Sialon grains, by the phase quantitative analysis and EDS, indicating that combinational sintering additives obviously promoted the nucleation and growth of O'-Sialon.The phase composite and the microstructure of the samples which were sintered at different temperature were studied, the results shown that increasing the sintering temperature had little different effect on the length of O'-Sialon grains, but was obvious on the size in radial. The effect mechanism of combinational sintering additives and sintering temperature were discussed by discussing the nucleation and growth mechanism of O'-Sialon grains.The performance of sintering and the properties of mechanics and dielectric of different samples were studied. The results indicated that the pore ratio had obviously effect on the properties of mechanics, bend strength decreasing exponentially with the increase of pore ratio, and the dielectric constant decreased with the increase of pore ratio. The dielectric constant of the main crystalline phase was studied, and the results shown that the O'-Sialon phase was in favor of decreasing the dielectric contant, moreover, the sintering properties and spinel phase also had some effect on it.