Aluminum nitride ceramicsIt is a covalent bond compound. It belongs to the hexagonal crystal system and has a wurtzite crystal structure. It is white or off-white. Aluminum nitride has good thermal conductivity and small coefficient of thermal expansion. Has excellent thermal shock resistance. The thermal conductivity of AlN is 2 to 3 times that of Al2O3, and the strength is higher than that of Al2O3 during hot pressing. Aluminum nitride has good corrosion resistance to Al and other molten metals, gallium arsenide, etc., especially has excellent corrosion resistance to molten Al liquid, and also has excellent electrical insulation and dielectric properties. However, aluminum nitride has poor oxidation resistance at high temperatures, is easy to absorb moisture and hydrolyze in the atmosphere, and produces heat and nitrogen when it comes into contact with wet air, water, or aqueous liquids, and decomposes quickly. Decomposed at 2516 ℃, the thermal hardness is very high, and it will not soften and deform even before the decomposition temperature. Aluminum nitride and water can also slowly react at room temperature, but are hydrolyzed. React with dry oxygen at 800 ° C or higher.

Physical properties

Density: 3.26

Melting point:> 2200 ℃ (lit.)

Properties: powder

Solubility: MAY DECOMPOSE

production method

1. Ammonia and aluminum are directly subjected to a nitriding reaction, and pulverized and classified to obtain aluminum nitride powder. Alternatively, alumina and carbon are thoroughly mixed and reduced in an electric furnace at 1700 ° C to obtain aluminum nitride.

2. After degreasing the high-purity aluminum powder (extracted with ether or heated to 150 ° C in a nitrogen stream), place it in a nickel pan, place the pan in a quartz or porcelain reaction tube, and slowly in the purified nitrogen stream Ground heating. Nitriding reaction proceeds rapidly at about 820 ° C. At this time, a large amount of nitrogen must be passed to prevent decompression in the reaction tube. After this intense reaction was completed, it was cooled in a nitrogen stream. Because the product contains metallic aluminum, it can be crushed and heated in a nitrogen stream at a temperature of 1100 to 1200 ° C for another 1 to 2 hours to obtain an off-white aluminum nitride.

In addition, aluminum is evaporated and gasified at 1200 to 1400 ° C, and reacted with nitrogen to obtain aluminum nitride whiskers (metal whiskers). In addition, there are also methods for thermal decomposition of AlCl3 · NH3 adducts.

3. Direct nitriding method Nitrogen and aluminum are directly subjected to a nitriding reaction, which is obtained by pulverization and classification. The quality of aluminum nitride products is affected by the conditions of the reaction furnace temperature, the premixing of raw materials, the mixing ratio of the circulating aluminum nitride powder, and the specific surface area of aluminum nitride. Therefore, it is necessary to strictly control the process to obtain aluminum nitride powder with stable characteristics (such as specific surface area, primary particle diameter, agglomerated particle diameter, bulk density, and surface characteristics, etc.).

Storage and transportation conditions

Dispose under dry protective gas, keep the container sealed, put it in a tight container, and store in a cool, dry place.

Product Usage

Aluminum nitride ceramic is a high-tech new ceramic. Aluminum nitride substrate has extremely high thermal conductivity, non-toxic, corrosion resistance, high temperature resistance, good thermochemical stability, etc. It is an ideal packaging material, heat dissipation material for large-scale integrated circuits, semiconductor module circuits and high power devices Circuit element and interconnection line carrier. It is also the best additive to improve the thermal conductivity and mechanical properties of polymer materials. Aluminum nitride ceramics can also be used as crucibles for melting nonferrous metals and semiconductor materials, gallium arsenide, protective tubes for thermocouples, high-temperature insulation parts, and microwave dielectrics. Materials, high temperature and corrosion resistant structural ceramics and transparent aluminum nitride microwave ceramic products, used as raw materials for high thermal conductivity ceramics and resin fillers. Aluminum nitride is an electrical insulator with good dielectric properties. The aluminum nitride coating on the surface of gallium arsenide can protect it from ion implantation during annealing.