Tabular alumina has been used as a refractory aggregate since the mid-1950s. At that time, high-purity calcium aluminate cement and phosphate binders were developed. The application of these binders improved the erosion resistance of tabular alumina refractories. and abrasion resistance.
Properties of Tabular Alumina
Unlike ordinary sintered corundum which is fired in a rotary kiln or tunnel, tabular corundum is rapidly fired at a high temperature above 1900°C and then crystallized α-Al2O3. Unlike ordinary corundum, accelerators such as MgO and CaO are added. It does not contain any additives, so tabular alumina has the following characteristics.
① The composition is well-developed α-Al2O3 crystal;
② The crystals of α-Al2O3 are coarse, the median diameter range is 40-200μm, and the two-dimensional morphology of the crystals is flat and interspersed with each other;
③ In the α-Al2O3 crystal, we can see many round closed pores of 5-15μm, and the content of open pores is only 2%-3%, which is relatively small;
④ There is β-Al2O3 at the grain boundary of α-Al2O3 crystal.
Due to the above structural characteristics of tabular alumina, it also has the following physical properties:
① Have a high melting point of about 2040°C;
② Has a large grain hardness, Mohs hardness 9, Knoop hardness (Knoop) 2000;
③ In addition to hydrofluoric acid and phosphoric acid, tabular alumina does not work with most alkalis and mineral acids, and has good chemical corrosion resistance;
④ It has strong strength, because it does not have microcracks and large internal pores; it has good thermal shock stability, and its strength will not drop much when it is subjected to thermal shock;
⑤ High thermal conductivity and resistivity, good electrical performance under high frequency and high temperature.
