For years, there has been a desire for a material to possess the same properties as graphite and a white luster. This material is boron nitride, known as "white graphite." As a high-performance new ceramic material, its applications and novel synthesis methods have become hot topics and cutting-edge issues in the field of materials research. Below, we explore the main properties and characteristics of boron nitride.

I. Main Properties of Boron Nitride

Boron nitride boasts excellent lubricity and high-temperature stability. Even at high temperatures (up to 2800℃), it maintains its lubricating properties and inertia.

2. Used for high-temperature solid lubricants, such as various optical glass film removers, metal molding release agents, metal wire drawing lubricants, and continuous casting steel separators for metallurgy.

Processed ultra-hard materials can be made into high-speed cutting tools and drill bits for geological exploration and oil drilling.

4. With excellent lubricating properties, as boron nitride is a hexagonal crystal, it is a very thin and fine material with similar properties to graphite, thus offering superior lubrication effects.

5. Boron nitride coatings, made of boron nitride, feature high-temperature resistance, non-stickiness, corrosion resistance, heat dissipation, and thermal conductivity. They remain unwetted by aluminum melt, providing protection for materials that come into direct contact with aluminum melt, magnesium, zinc alloys, and their slag.

Section II: Boron Nitride Performance

Boron nitride boasts chemical resistance, remaining unattacked by inorganic acids and water in hot concentrated alkalis without breaking the boron-nitrogen bonds. It starts to oxidize in air above 1200°C, melting at 3000°C, begins sublimation slightly below 3000°C, and starts to decompose at around 2700°C under vacuum. It is slightly soluble in hot acid but not in cold water, with a relative density of 2.25 and compressive strength of 170 MPa. Its high-temperature use in oxidizing atmospheres reaches up to 900°C, while in non-reactive reducing atmospheres, it can withstand temperatures up to 2800°C. However, its lubricity is poor at room temperature. For hexagonal boron nitride, most of its properties are superior to carbon materials: low friction coefficient, good high-temperature stability, excellent thermal shock resistance, high strength, high thermal conductivity, low expansion coefficient, high resistivity, corrosion resistance, and microwave or infrared transmission capabilities.

What are the applications of boron nitride?

1. Based on stability

Boron nitride does not wet or react with most metal melts, such as steel, stainless steel, aluminum, iron, germanium, bismuth, silicon, copper, and others. Therefore, it can be used as crucibles, boat dishes, liquid metal transfer pipes, rocket nozzles, high-power device bases, high-temperature thermocouple protection, metal melting pipes, pump components, cast steel molds, and high-temperature electrical insulating materials.

2. Based on heat resistance and corrosion resistance

Manufacturing high-temperature thermal insulating components for spacecraft and rockets.

3. Based on the insulation conditions

Boron nitride is widely used in high-voltage, high-frequency electrical insulation, plasma arc insulators, various heater insulators, heating tube sleeves, high-temperature, high-frequency, high-voltage insulating heat sinks, and high-frequency furnace materials.

4. Based on the thermal conductivity coefficient

Boron nitride is used as crucibles for preparing gallium arsenide, gallium phosphide, and indium phosphide; heat spreaders for semiconductor packaging; cooling rods for phase shifters; cooling tubes for traveling wave tube collectors; P-type diffusion sources; microwave windows for semiconductors and integrated electrodes.

5. Based on the shielding performance

Boron nitride is used as a neutron absorber and shielding material in atomic reactors. It is also employed as infrared and microwave polarizers, infrared filters, optical channels for laser instruments, and high-voltage transmission materials.