Alumina is abundant second only to silicon dioxide on the earth, is one of ceramic material. In the oxides, aluminum and oxygen have strong bond, it can make alumina become the highest hardness oxide. Alumina has high chemical stability and corrosion resistance to most of acid, alkaline, salt and molten solution. Alumina's strength would be different due to the density or its micro structure. At the normal temperature, alumina's strength would reach the highest. Along with the temperature rising to 1000˚C, the strength would significantly decrease. Alumina also has lower thermal expansion coefficient.

All of alumina's feature are related to purity. In general, the higher purity it is the finer thermal conductivity it has. Moreover, when the alumina's purity is extremely high, its density will close to theoretical density and more better mechanical property.

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