In the vast expanse of inorganic non-metallic materials, hexagonal boron nitride (h-BN) powder shines like a unique star. Due to its snow-white appearance and graphite-like layered structure, it is vividly referred to in the industry as “white graphite.” This hexagonal crystal system material, formed by alternating rows of boron and nitrogen atoms, plays a “hardcore” role in the extreme environments of modern industry thanks to its irreplaceable properties.
Unique Physicochemical Properties
The crystal structure of h-BN endows it with outstanding properties that are both contradictory and harmonious. Atoms within each layer are tightly bound by strong covalent bonds, while layers are stacked together by weak van der Waals forces. This structure allows it to possess multiple characteristics:
First, it offers excellent thermal management capabilities. Although it is an electrical insulator (with a resistivity as high as 10¹⁴ Ω·cm), it is an excellent thermal conductor, with a theoretical in-plane thermal conductivity of up to 6000 W/(m·K)—far exceeding that of traditional materials such as quartz. At the same time, it possesses an extremely low coefficient of thermal expansion and exceptional thermal shock resistance, remaining completely stable even during repeated rapid cooling and heating cycles between 1200°C and 20°C.
Furthermore, it possesses exceptional high-temperature stability and chemical inertness. In nitrogen, its sublimation temperature reaches 3000°C, and even at 1800°C, its strength remains twice that at room temperature. Most notably, it is chemically inert toward nearly all molten metals (such as aluminum, steel, and copper), neither wetting nor reacting with them. It is also resistant to acid and alkali corrosion, oxidizing only in high-temperature oxygen.
Finally, it possesses inherent lubricating and machinability properties. With a Mohs hardness of just 2 and a coefficient of friction as low as 0.16, its soft texture makes it easy to machine, making it an ideal solid lubricant.
Widespread Industrial Applications
Thanks to the properties described above, h-BN powder has found its way into many key sectors of the national economy:
In the metallurgy and foundry industries, it serves as a “shield” against high-temperature molten metals. Used as a raw material for evaporation boats, crucibles, and continuous casting separation rings, it effectively resists corrosion from molten aluminum and steel, extending service life by 3 to 5 times compared to graphite materials. In metal casting, boron nitride coatings applied to mold surfaces significantly reduce melt flow resistance, prevent sticking, and improve casting precision.
In the electronics and semiconductor sectors, it serves as the “heat dissipation guardian” for chips. Due to its high thermal conductivity and insulating properties, it is widely used in chip electrostatic clamping fixtures, plasma etching components, and electronic packaging materials. When added to resins, it enables the production of highly thermally conductive insulating composites, resolving heat dissipation bottlenecks in electronic devices.
In the cutting-edge aerospace sector, it serves as a “stabilizer” in extreme cold and heat. From the thermal insulation layers of rocket nozzles to the transparent windows of aircraft and the lubricants for high-temperature bearings, h-BN ensures the safe operation of aircraft under extreme conditions thanks to its lightweight, high-temperature resistance, and resistance to ion sputtering.
Furthermore, it shines equally brightly in the fields of new energy and consumer goods. It serves both as a neutron absorber in nuclear reactors and as a body pigment in cosmetics, utilizing its smooth texture to enhance the product’s skin feel.
H-BN powder, with its pristine white form withstanding intense heat and its insulating properties conducting thermal energy, is becoming an indispensable cornerstone material underpinning modern high-end manufacturing.
