Low expansion ceramic-Introduction and application of cordierite ceramics

1. Overview of cordierite

Cordierite (2MgO·2Al2O3·5SiO2) was discovered in 1925, and only a small amount as a natural mineral.The earth exists in nature. The thermal expansion coefficient of cordierite is 2.9X10^-6/℃. The melting point is about 1460℃, and it has good thermal stability. Cordierite has two homogeneous and multi-phase variants, namely low-temperature cordierite and high-temperature cordierite. High-temperature cordierite, also known as Indialite, belongs to the hexagonal crystal system; low-temperature cordierite is commonly referred to as cordierite. It belongs to the orthorhombic crystal system.

2. Manufacturing technology of cordierite ceramics

Cordierite ceramics are usually made by two methods: one is melting glass crystallization; the other is the sintering combination method.

(1) Molten glass crystallization method

The melting glass crystallization method is to make cordierite ceramics by melting homogeneous mixture of materials into glass at high temperature, after forming, and then heat treatment to precipitate crystals. This method requires uniform glass melting, no bubbles, melting temperature should be high, up to 1600℃ above. The other method is to melt at a relatively low temperature, quench and grind to a fine powder, and then sintered to produce cordierite ceramics. The melting temperature can be below 1450℃. The forming method can be dry pressing or grouting, so it is suitable for the preparation of products with complex shapes and the size can be controlled more accurately

(2) Synthesis of cordierite ceramics by sintering method

Cordierite ceramics are made of talc, kaolin and alumina, which are mixed evenly and sintered at a certain temperature after forming.

Cordierite ceramics can be made into honeycomb structure and used as automobile exhaust purification device. It’s forming method can be extruded by vacuum mud purifier and sintered at 1400℃ for 6 hours after forming and drying.

3. Performance and application of Cordierite Ceramics

(1) The performance of cordierite ceramics

Cordierite has a low expansion and a low dielectric constant (5.3MHz).

(2) The application of Cordierite Ceramics

Catalyst carrier for automotive exhaust purification system. Cordierite ceramics are generally processed to have a cellular structure, which is conducive to the filling of granular catalysts with a diameter of a few millimeters in a cellular carrier.

Cordierite ceramics can be used not only as automobile exhaust purifier, but also as deodorization and smoke exhaust deoxidation devices in general industries.

In addition add 30% calcined material to cordierite (60% MnO2, composed of 20% Fe2O3 and 10% Cu0), the ceramics obtained are highly efficient infrared radiators.

Cordierite ceramics are not very acid resistant and should not be used in acid etching sites.

Cordierite honeycomb ceramic catalyst carrier