What is the composition of mullite in a refractory?

Mullite is a mineral compound with the chemical formula 3Al2O3·2SiO2, which is also known as aluminum silicate (Al2SiO5). It is a common constituent of many refractory materials due to its excellent thermal shock resistance and high-temperature stability.

The composition of mullite in a refractory depends on the specific material and manufacturing process used. Generally speaking, mullite-containing refractories are made by heating mixtures of alumina and silica at high temperatures, typically above 1600°C. During this process, the alumina and silica react to form mullite crystals.

The ratio of alumina to silica in the starting mixture can affect the composition of mullite in the resulting refractory, as well as the properties of the final product. In general, higher ratios of alumina to silica result in higher mullite content and better high-temperature performance.

In addition to its high-temperature stability and thermal shock resistance, mullite is also known for its low thermal expansion coefficient, good mechanical strength, and resistance to chemical attack. These properties make mullite-containing refractories suitable for use in a wide range of high-temperature applications, such as furnace linings, kiln linings, and other equipment used in the production of metals, ceramics, and glass.