Aluminum oxide (alumina, Al2O3), a metal oxide, is a common raw material for manufacturing ceramics. It is a good electrical insulator that shows stability at high temperature and resistance to chemicals. Alumina is an important source for aluminum and has been prepared from high-alumina ladle furnace refining slag. It can enhance the reaction rate of aldose to ketose conversion by Lobry de Bruyn-Alberda van Ekenstein transformation. It is a key constituent of NOx storage catalysts (NSC), which are employed to get rid of nitrogen oxides from the exhaust gas of lean burn engines. Its surface passivation characteristics on crystalline silicon makes it a vaiable candidate in silicon solar cell production.