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

Near zero thermal expansion porous ceramics were fabricated by using SiC and LiAlSiO4 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 LiAlSiO4 was decomposed to LiAlSi2O6 and LiAlO2, some of LiAlSiO4 reacted with SiO2 to form LiAlSi2O6 during sintering. With increasing the content of glassy materials, the reaction between LiAlSiO4 and SiO2 was accelerated. The Young's modulus increased due to the neck growth between the SiC grains. The 52.5 vol% LiAlSiO4 (LAS)/SiC ceramics with ∼36% porosity had a combination of near zero coefficient of thermal expansion ∼0.39×10−6K−1 at room temperature and relatively high Young's modulus ∼59GPa.