Cordierite is a kind of aluminomagnesium silicate mineral, generally blue, because of its dichroism, it is also called dichroite.
1. Name of cordierite
Cordierite, also known as dichroic stone, is also known as "sapphire".
2. Cordierite composition
The molecular formula of natural cordierite is 2MgO · 2A l 2O 3 · 5 SiO 2, theoretical composition MgO 13.5%, Al 2O 3 34.9%,
51.3% SiO2. In fact, the chemical composition of Dong Qingshi is often different from that of the theory, and cordierite has higher iron content
It is called iron cordierite when the manganese content is high and manganese cordierite when the manganese content is high.
3. Properties of cordierite
Cordierite has three crystal types: (1)-cordierite, hexagonal symmetrical structure; (2) cordierite, orthorhombic system; (3)-cordierite, rhombohedral phase. The color is generally blue, light blue, gray blue, smoke blue, dark blue and other blue, from a certain direction, often like wood cordierite dark blue (cordierite), and from the orthogonal direction, it appears gray or yellow, because of this dichroism, it is also called dichroic stone, cordierite crystals are mostly short columns, glass luster, density: 2.60 g/cm3; Mohr hardness 7 ~ 7.5; Transparent ~ translucent. Cordierite is characterized by low thermal expansion coefficient, low thermal conductivity, good thermal shock resistance, low dielectric constant, low dielectric loss and good chemical stability.
4. Use of cordierite
Cordierite is a kind of non-metallic mineral raw material with many uses. It is widely used in metallurgy, electronics, automobile, chemical industry, environmental protection and other fields. It can be used as high-quality refractory materials, electronic packaging materials, catalyst carriers, foam ceramics,
Printed circuit boards and low-temperature radiant materials. Cordierite can not only be used as a material alone, but also be compounded with other materials to prepare composites.
4.1 Cordierite composite ceramics
Alumina-cordierite composite ceramics
Alumina ceramics have high strength, high hardness and good oxidation resistance and chemical stability, so alumina ceramics are widely used as engineering ceramics. The thermal shock resistance of alumina ceramics can be improved by introducing cordierite with low thermal expansion coefficient into alumina ceramics.
4.2 Mullite-cordierite composite refractories
Mullite-cordierite shed slab
Mullite is a common raw material in the field of refractory. The mullite-cordierite composites prepared by introducing cordierite into mullite materials can not only improve the thermal shock resistance of mullite materials, but also increase the heat resistance temperature of mullite materials by using the thermal mismatch mechanism of multiphase ceramics.
4.3 Cordierite composite refractory
Magnesia-alumina spinel-cordierite refractory brick
Magnesium-aluminum spinel is a kind of mineral with high melting point, large coefficient of thermal expansion, stable chemical properties and strong resistance to weak basic slag, but its thermal shock resistance is poor. Adding cordierite with low thermal expansion coefficient to magnesia-alumina spinel can reduce the thermal expansion coefficient of the composites and improve the thermal shock resistance of the composites.
4.4 Cordierite castable
Cordierite castable
The castable with excellent abrasion resistance and thermal shock resistance can be prepared by using coke gemstones and cordierite as raw materials.
4.5 Cordierite refractory coating material
Cordierite refractory coating
Lost foam cordierite refractory coating materials were synthesized in situ from kaolin, alumina, talc and magnesium oxide. Its good thermal shock resistance ensures that the coating is not easy to crack, the structure is loose and conducive to exhaust gas, and then can ensure the dimensional accuracy of castings, can produce high-quality castings. The main crystal phase of the material is cordierite, the coating is easy to remove from the casting surface, and the casting surface is smooth and bright.
4.6 Cordierite porous material
Cordierite porous material
Cordierite can be used to prepare porous materials, such as honeycomb ceramics and foam ceramics, as an ideal catalyst carrier and filter device for purifying exhaust gas. Cordierite can be used in automobile exhaust gas purification, metal melt filtration, high-temperature flue gas filtration, ultrafine particle filtration, catalytic combustion, heat exchange and other chemical processing processes.
4.7 Infrared Materials
Cordierite infrared material
Cordierite-based materials have high infrared emissivity, cordierite also has high temperature resistance, high dielectric constant, stable physical and chemical properties, good thermal shock resistance and other characteristics, so cordierite-based materials are an important infrared material.
4.8 Dielectric Materials, Electronic Packaging Materials
Cordierite Radome Transmitter
Cordierite has low dielectric constant and good electrical insulation properties. The radar radome transparent material prepared by cordierite as main crystal phase has low dielectric constant and high thermal shock resistance. The glass-ceramics prepared by cordierite as main crystal phase has excellent dielectric properties, mechanical properties, electrical properties and low temperature sintering properties.
4.9 Cordierite Gems
Cordierite gem
Cordierite is similar to sapphire in color, so it is also called hydrosapphire. Because it has the color and luster of sapphire and the price is much cheaper than sapphire, so it is more jokingly called the poor sapphire, cordierite energy is quite stable and can not change its color by heating is a real gem.
5. Reserves and distribution of cordierite
Natural large cordierite deposits have not been found so far. Most of the cordierite used in industry is artificially synthesized.
6. Synthetic method of cordierite
Because natural cordierite is dispersed and large deposits have not been found so far, synthetic cordierite is needed from different ways. The main synthetic methods of cordierite are as follows: ① synthesis of cordierite by high temperature solid state reaction of natural minerals; 2. Synthesis of cordierite by high-temperature solid-state reaction of high-purity oxide; (3) synthesizing cordierite from industrial and agricultural wastes; ④ Wet chemical synthesis of cordierite; ⑤ low temperature combustion synthesis. At present, cordierite is mainly synthesized by solid state reaction.