Effect of glassy bonding materials on the properties of LAS/SiC porous ceramics with near zero thermal expansion

摘要

Near zero thermal expansion porous ceramics were fabricated by using SiC and LiAlSiO_4 as positive and negative thermal expansion materials, respectively, bonded by glassy material. The coefficient of thermal expansion value of a desired porous composite can be easily controlled by choosing the appropriate ratios of the different phases. It was shown that some of LiAlSiO_4 was decomposed to LiAlSi_2O_6 and LiAlO_2 some of LiAlSiO_4 reacted with SiO_2 to form LiAlSi_2O_6 during sintering. With increasing the content of glassy materials, the reaction between LiAlSiO_4 and SiO_2 was accelerated. The Young's modulus increased due to the neck growth between the SiC grains. The 52.5 vol% LiAlSiO_4 (LAS)/SiC ceramics with ~36% porosity had a combination of near zero coefficient of thermal expansion ~0.39 ×10~(-6) K~(-1) at room temperature and relatively high Young's modulus ~59 GPa.