This kind of mullite brick containing ZrO2, commonly known as zirconium mullite brick, is generally made by electric melting method, and can also be produced by sintering method.
Sintered zirconia mullite brick is a kind of special refractory material which uses industrial alumina and zircon concentrate as raw materials and introduces zirconia into Mullite Matrix through reaction sintering process.
The high-temperature mechanical properties of mullite can be greatly improved by introducing zirconia into mullite brick and toughening it by phase transformation. Zirconia can promote the sintering of mullite materials. The addition of ZrO2 can accelerate the densification process of ZTM materials due to the formation of low melting point materials and vacancies. When the mass fraction of ZrO2 is 30%, the relative theoretical density, strength and toughness of the green body sintered at 1530 ℃ are 98%, 378 MPa and 4.3 MPa·m1/2, respectively.
It is difficult to control the process of zirconia mullite brick made by reaction sintering with industrial alumina and zircon as raw materials. In general, when sintering, it is densified at 1450 ℃ and then heated to 1600 ℃ for reaction. ZrSiO4 decomposes into ZrO2 and SiO2 at 1535 ℃, in which SiO2 reacts with AI203 to form mullite. Because part of the liquid phase appears during the decomposition of ZrSiO4, and the decomposition of ZrSiO4 can refine the particles, increase the specific surface area and promote sintering.
The results show that with the increase of zircon, the microstructure of sintered samples is gradually transferred from the network of columnar corundum to that of columnar mullite. The flexural strength of the sample increases with the increase of zirconia content at high temperature (1400 ℃), and a larger value appears when the zirconia content is 23.7%, and then the strength decreases. The addition of zircon can improve the thermal shock resistance.
