Aluminum oxide ceramic
Aluminum oxide and alumina ceramics have excellent wear characteristics, chemical resistance, compressive strength, high-temperature properties, and dielectric strength. They are used widely because of their versatility and low cost. Their main drawback is its relatively poor thermal-shock resistance due to higher coefficients of thermal expansion and lower thermal conductivity (compared to other pure ceramic materials).
What is Aluminum Oxide?
Aluminum oxide (Al2O3) is a compound of aluminum metal and oxygen used in the alpha alumina structural form. It is commonly referred to as alumina, a white high-hardness ceramic. Fully-dense alumina can be translucent.
Types of Aluminum Oxide Ceramics
The GlobalSpec SpecSearch database contains information about different types of aluminum oxide ceramics. Examples include calcium aluminate, sapphire, and alumina-zirconia.
- Calcium aluminate (CaAlO3) is an aluminate ceramic used in refractory cements and shapes, as well as synthetic slag additions for metallurgical operations.
- Sapphire is a high-purity and high-density, single-crystalline form of aluminum oxide that may contain chromia, titania, yttria, or other dopants. Sapphire is usually transparent or translucent.
- Zirconia-toughened alumina (ZTA) and other zirconia-alumina ceramics are often used in wear applications as an intermediate solution between alumina and zirconia. ZTA offers increased fracture toughness over alumina at a lower cost compared to pure or high zirconia ceramics.
Commercial Grades of Alumina
There are many different commercial grades of alumina. Examples include smelter-grade, calcined, low soda, reactive, tabular, fused, and high-purity.
- Smelter alumina is used in the manufacture of aluminum metal, typically in fluid bed or fluid flash calciners.
- Calcined alumina may use mineralizing catalysts and contain sodium oxide as the main impurity. They improve the performance of both shaped and monolithic refractories.
- Low soda alumina is used mainly in electrical and electronic components.
- Reactive alumina has a relatively high purity and small crystal size. It is used in the production of high-performance refractories that require defined particle packing and consistent placement characteristics.
- Tabular alumina is re-crystallized or sintered alpha alumina. It is used in shaped and unshaped refractories for steel, cement, foundry, glass, petrochemical, and waste incineration applications. Non-refractory applications for tabular alumina include its use in kiln furniture and for metal filtration.
- Fused alumina is made in electric arc furnaces. The fused mass is then crushed and sized to meet application requirements.
- High-purity alumina is used in the manufacture of synthetic gem stones, laser components, and instrument windows.
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