Aluminum oxide (Al₂O₃) – known in its crystalline form as corundum – is the most widely used material in technical ceramics . This compound of aluminum and oxygen is characterized by an outstanding combination of high hardness , excellent wear resistance, and very good electrical insulation. At the same time, aluminum oxide ceramics offer an attractive price-performance ratio that few other ceramic materials in industry can match.
Aluminum oxide (Al₂O₃) is predominantly produced synthetically from bauxite using the Bayer process. The resulting high-purity powder forms the basis for the manufacture of ceramic components.
During sintering of the aluminum oxide powder at temperatures of approximately 1,600–1,700 °C, the microstructure densifies into a dense, fine-grained structure.
The properties of the finished material can be specifically influenced via purity level, grain size and sintering parameters.
This targeted microstructure design results in aluminum oxide ceramic grades with different property profiles – tailored to the respective application area.
The unique properties of aluminum oxide ceramics make it the material of choice for numerous demanding applications – from electronics to grinding technology. A closer look reveals why:
Aluminum oxide is largely inert to most acids, alkalis, and organic solvents at normal temperatures. Even in contact with molten metals, high-purity Al₂O₃ exhibits good corrosion resistance. Only concentrated hydrofluoric acid, hydrochloric acid, and strong alkalis at high temperatures can attack the surface. For demanding chemical environments, we always recommend individual material consultation.
In practice, aluminum oxide has proven its worth in an impressive range of industrial applications . Depending on the degree of purity and component geometry, the material can be precisely tailored to a wide range of requirements.
Choosing the right material always depends on the specific application. The following classification provides guidance:
| Characteristic | Aluminum oxide (Al₂O₃) | Silicon carbide (SiC) | Tungsten carbide (WC-Co) |
|---|---|---|---|
| Hardness (HV10) | 15–19 GPa | ~24 GPa | 12–18 GPa |
| Density | 3,75–3,95 g/cm³ | ca. 3,10 g/cm³ | 14–15 g/cm³ |
| Flexural strength | 360–600 MPa | 300–550 MPa | 1’500–3’500 MPa |
| Thermal conductivity | 25–32 W/(m·K) | 100–140 W/(m·K) | 60–80 W/(m·K) |
| Max. operating temperature | 1’200–1’700 °C | up to 1’600 °C | 500–800 °C |
| Electrical insulation | Excellent | Semiconducting | Conductive |
| Toughness/Fracture strength | Low (brittle) | Low (brittle) | High |
Aluminum oxide is the preferred choice when electrical insulation, chemical resistance, and a good price-performance ratio are paramount. Where maximum toughness and impact resistance are required, tungsten carbide -based hard metals offer clear advantages. For extreme temperatures or abrasion under thermal stress, silicon carbide may be the better alternative.
