Author:Site Editor Publish Time: 27-07-2017 Origin:Site
Mullite ceramics are mainly ordinary mullite porcelain and high purity mullite porcelain.
Ordinary mullite porcelain to aluminosilicate natural minerals as the main raw material, the use of sintering in the process of mullite reaction sintering method or the first synthesis of mullite and then forming, sintering method made. Due to the low purity of raw materials and high impurity content, the components contain TiO2, Fe2O3, CaO, MgO, Na2O, K2O and other impurities in addition to A12O3 and SiO2, and thus have a considerable amount of glass phase in the products, resulting in mechanical and thermal properties Poor, so that the excellent performance of mullite ceramics at high temperatures can not be fully exploited. Therefore, industrial mullite ceramics can only be used in the temperature, high temperature strength requirements are not high occasions as a general use of refractories.
If the high purity Al2O3 powder and high purity SiO2 powder reaction sintering or by the synthesis of ultra-fine high-purity mullite powder prepared by the glass phase of mullite porcelain, is known as high-purity mullite ceramics. High purity mullite is a kind of high quality refractory material, it has the characteristics of uniform expansion, excellent thermal shock stability, high softening point, high creep temperature, high hardness, good chemical resistance and so on. Especially high-performance high-purity mullite ceramics, bending strength at 1300 ℃ at 570MPa, fracture toughness KIC up to 5.7MPa, 1.6 times higher than normal temperature, this with the temperature, strength and toughness not only Not fading but a substantial increase, is high purity mullite ceramic as a high temperature material excellent characteristics.
The main application areas of high purity mullite ceramics
Mullite ceramic with high melting point, creep resistance, low coefficient of expansion, thermal shock resistance and excellent corrosion resistance Mullite refractory bricks can be used as a variety of high temperature furnace lining, including furnace kiln, blast furnace , Hot iron pouring and continuous casting furnace lining materials. The mouth has been used in the control of molten steel flow of the rotary valve outlet of the lower part of the lining. It is said that silicon-rich mullite contains 10-40% of aluminum-rich mullite, greatly improving the thermal shock resistance. In addition, it is also widely used in cement high temperature calcined area lining.
High temperature engineering materials
The United States in the early nineties the development of low thermal expansion, low heat loss of advanced ceramic engine, the mullite was listed as the main candidate material. China developed the mullite ceramic cylinder head in the desert car on the successful trial, the initial display of the material better application prospects. Germany's use of aluminosilicate long fiber toughened mullite composite materials in the propeller aircraft exhaust device on the use of test success; Japan had made mullite ceramic material conveyor belt to replace the tunnel kiln stainless steel conveyor belt. Mullite ceramics are also widely used in metal melting crucible, high temperature protection tube and thermocouple protection tube and other heat-resistant materials to prove that its high temperature gas corrosion resistance is better than alumina ceramics, and good air tightness, as high temperature engineering materials, Particularly suitable for the production of high temperature protection tube.