Hexagonal boron nitride (HBN) is one of the best thermal conductivity materials among ceramic materials. Its structure is similar to graphite – hexagonal, showing loose, lubricating, light, and soft properties, so it is also called “white graphite” because of its white color.
HBN is not only a good thermal conductor, but also a typical electrical insulator, so it is an ideal high frequency insulation, high voltage insulation, high temperature insulation material. With such good properties, h-BN plays an irreplaceable role in some fields. The following are some applications of HBN ceramic materials.
1. High temperature resistant coating
The apparent chemical inertness of boron nitride at high temperatures allows boron nitride ceramic coatings to be used to protect aluminum, magnesium, zinc alloys and other materials from high temperature oxidation. When refractory or ceramic utensils are coated with boron nitride coating, even when the temperature is as high as 1273K, they can effectively keep their anti-oxidation properties.
2. Thermally conductive filler
BN as a filler has been widely used in thermally conductive composites. It solves the problem of avoiding short circuits with high resistivity materials required for thermally conductive materials to contact electrical components in operation. The composite material prepared by blending ultrasonically exfoliated two-dimensional boron nitride nanosheets and one-dimensional cellulose nanofibers is the nanocomposite with the highest thermal conductivity so far—the thermal conductivity is as high as 180W/(m•K). Adding boron nitride powder into the thermally conductive silicone sheet can make it show lower thermal resistance and higher electronic insulation properties under compressive force.
3. High temperature lubricant
HBN has excellent high temperature lubricity. When used as a lubricant, HBN can be dispersed in heat-resistant grease, water or solvent. When HBN is sprayed on the friction surface, it will form a dry mold, and because h-BN neither wets nor interacts with steel, stainless steel, aluminum, etc., it is often used in anti-corrosion of molten metal occasions, such as smelting evaporation financial Crucibles, boats, liquid financial pipes, etc.
4. Release agent
Ordinary lubricating oil, resin, graphite, etc., will lose their lubricating function in a certain high-temperature environment. In contrast, the ultra-high temperature resistant mold release agent made of boron nitride, a solid lubricant, can still maintain excellent lubricity and mold release properties at extremely high temperatures. Therefore, it is suitable for the molding of diamond tools, high-temperature hardening resin, glass and sintered metal.
5. High insulation & high thermal conductivity ceramic products
Boron nitride ceramics have good heat resistance, thermal stability, thermal conductivity, high temperature dielectric strength, and are ideal heat dissipation materials and high temperature insulating materials. Due to its good chemical stability, it can resist the erosion of most molten metals; the product has low hardness (Mohs strength 2), so it can be machined with an accuracy of 1/100mm. BN ceramics are often used in the manufacture of crucibles for smelting semiconductors and high-temperature containers for metallurgy, semiconductor heat-dissipating insulation parts, high-temperature bearings, thermowells and glass forming molds.
6. For the synthesis of cubic boron nitride
C-BN is another common form of boron nitride. Its hardness is second only to diamond and much higher than other materials, and it is also the theoretical low temperature stable phase. Using h-BN with the participation of a catalyst to transform into c-BN boron nitride as hard as diamond at high temperature (1800 °C) and high pressure (800 Mpa) is one of the main methods for synthesizing boron nitride.
7. Cosmetics
With the lubricity and light weight brought by the layered crystal structure, h-BN powder can also be used as an extender pigment in cosmetics. HBN powder has excellent coating and adhesion, and the color is white, which can effectively adjust the spreadability, skin adhesion, gloss, skin texture, moldability and usability of products.
Conclusion
Today, the rise of nanotechnology has also led to the rise of nano-boron nitride. Nanostructures such as boron nitride nanosheets and nanotubes (BNNTs) and boron nitride nanoribbons have also attracted great interest of researchers due to their advantages in optoelectronics, environmental protection, and daily chemicals.
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