A certain type of ceramic tiles are fixed on the outer layer of a space shuttle. They are made from alumina (Al2O3), zirconia (ZrO2), silica (SiO2) and a few oxides like (SiC), (B4C). These tiles require a temperature of 1600 °C to 1800 °C and an oxygen free atmosphere for firing. These tiles are heat resistant, water resistant and are electrical insulators. Some types of ceramics are also used as superconductors.