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Spherical alumina is basically alumina “shaped” in a high temperature fusion process. Spherical alumina therefore has the same intrinsic properties as any other alumina. Its chemical formula is Al2O3.
At Sibelco high purity aluminas are being used to make spherical alumina.
Aluminium Oxide is a white powdery material, Al2O3 has good electrical insulating properties while having relatively high thermal conductive properties (36 Wm−1K−1), furthermore characterised by:
- High thermal conductivity
- High inertness in various media
- High density and, as a result, low oil absorption
- High Mohs hardness of 9
- High Refractive Index of 1.76
Spherical Alumina is mostly used in applications where control of heat is a critical issue. Adding spherical alumina to a formulation will greatly increase the thermal conductivity of the formulation. This is a result of alumina having high thermal conductivity, but also because the sphericity of the particles allowing for a dense packing/high loading.
These formulations have become more and more important in thermal management in electronics where the desire for ever faster accelerating processing and miniaturisation has resulted in an increase in energy and an increase of risk of local overheating. Thermal management also is an important factor in the Li-ion battery systems for electric vehicles.
Materials containing spherical alumina are applied in contact with the outside of the batteries to help “drain” the heat away from the batteries. This way the batteries stay at a temperature at which they show optimal performance and at which they will last longer.