Mullite is rarely found in nature,is the only stable compound in the alumina-silica phase diagram and is an important constituent of refractory and engineering ceramics.For ceramic heat shield tiles as combustion chambers of gas turbines,the tubular alumina and mullite are mixed.The amount of mullite in the final tiles is 30±5wt％.In this research,sintered or fused mullite,tabular alumina and novolak resin were mixed and pressed and then were fired at 1750°C at for 10h shuttle kiln.The physical,mechanical,and thermo mechanical properties of samples such as bulk density,open porosity,bending strength at room and high temperature,elastic modulus,thermal expansion and conductivity were investigated.The results showed that the type of mullite has significant effects on the properties of samples.Modulus of rupture at ambient temperature,1200°C and 1400°C were 15.2 MPa,9.06 MPa and 5.72 MPa for fused mullite containing sample but for sintered mullite containing sample these value were 11.5,8.35 MPa and 4.31 MPa respectively.The thermal shock resistance of two samples after 30cycles from 1000°C to room temperature showed that number and size of cracks in the fused mullite containing samples were lower that from sintered mullite containing sample.These results related to the shape of acicular mullite grain of fused mullite.
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