Tabular alumina is pure, fully sintered alumina without any additives. Refractory materials or castables made from tabular corundum alumina exhibit good thermal shock resistance and flexural strength after high-temperature treatment. Fused alumina, commonly used in refractory materials, is typically white or brown alumina. It is mainly produced by melting alumina or bauxite. The differences between sintered tabular corundum and fused alumina are:
1. Sintered tabular alumina has a low and uniformly distributed impurity content, while fused alumina has a high and unevenly distributed impurity content. Sintered tabular corundum alumina uses high-purity industrial alumina as raw material, and no additives are added during the production process. Except for a small amount of mechanical iron entering during crushing (which can be removed by magnetic separation), other impurities such as iron, silicon, and sodium are present in trace amounts. Fused alumina requires the addition of iron and carbon as additives during production, resulting in a much higher content of impurities such as iron, carbon, silicon, and sodium compared to sintered tabular corundum alumina. Meanwhile, due to the uneven cooling rate of different parts of the molten alumina during fusion, the impurity content varies in different areas. Therefore, fused alumina requires strict selection, while sintered tabular alumina does not.
Second, sintered tabular corundum alumina exhibits superior thermal shock and spalling resistance compared to fused alumina. Sintered tabular alumina's better thermal shock and spalling resistance stems from its numerous closed pores. These spherical closed pores effectively resist thermal shock and prevent crack propagation. In contrast, fused alumina has more open pores and fewer closed pores, and its slower cooling process results in larger single crystals. These single crystals generate microcracks during fragmentation, thus reducing its thermal shock and spalling resistance.
Third, the production process of sintered tabular corundum alumina is far more energy-efficient and environmentally friendly than that of fused alumina. Fused alumina is a well-known high-energy-consuming industry, requiring 2300-3300 kWh of electricity per ton, while sintered tabular corundum alumina consumes only one-seventh to one-tenth of the total energy. The production process of fused alumina generates large amounts of waste gas and slag, whereas sintered tabular alumina uses natural gas as a heat source, producing no waste gas or slag emissions other than carbon dioxide from the natural gas.
