THERMOMECHANICAL BEHAVIOR OF TWO POROUS MULLITE CERAMICS

Elaboration of porous silica-alumina refractory insulating firebricks from mixtures of silica-sand and recycled alumina are investigated. Expanded perlite and sawdust were added to create the pores. Adding of expanded perlite gives more mechanically stronger refractory (FS: 36.7 MPa) but less porosity (p: 35.8%) compared to the refractory containing sawdust (FS: 29.7 MPa; p: 45.8%). The latters are characterized by their lower thermal conductivities (0.53 W/mK). The formation of cracks decreases the velocity of ultrasonic pulses travelling in the refractory because it depends on the density and elastic properties of the material. The thermal shock resistance shows the ability of the samples to withstand rapid changes in temperature. Various properties, such as toughness analysis, nitrogen adsorption and surface area were also examined.