Synthesis and Properties of Alumina-Mullite based refractories used in steel industry: The effect of ZrO2

Ceramics owning to functional limitations must be exposed to the reinforcing phases. It’s possible to reduce the limitations and make a profit of the advantages of ceramic phases such as high abrasion resistance, hot strength, high creep resistance and low thermal expansion. Fabrication of composite refractories with advanced properties is usually complicated. In-situ formation of the expected phases by using inorganic materials is an economical process. Mullite and specially alumina have been used in high temperature application because of their low thermal expansion coefficient, good thermal shock resistance, high creep and refractoriness under load. Evolution of SiC and ZrO2 in the matrix of alumina and mullite improves erosion resistance, thermal shock resistance, toughness and strength. In this project mullite and alumina matrix composites with in-situ SiC whiskers as reinforcing phases is fabricated by carbothermic reduction of Zircon and Alumina and followed by powder metallurgy. The results showed that C/SiO2 ratio and initial volume of Zircon affect the phase evolution. By increasing the C/SiO2 ratio up to 5.5, SiC whiskers have been increased and hinders grain growth. When C/SiO2=3.5, more ZrO2 is formed due to the higher volume of initial Zircon and affect the grain growth of alumina and mullite.