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.
