Nitride fibre-mA
Brief introduction of Boron Nitride (BN) manufacturing process
Boron Nitride (BN) is usually made of graphite structure, commonly known as white graphite. BN can be also made of diamond structure which has the similar principle of converting graphite into diamond. BN with graphite structure can be transformed into NB with diamond structure at high temperature (1800 ℃) and high pressure (800MPa).
The B-N bond length of BN with graphite structure is 156pm, which is similar with that of C-C bond length (154pm). Their density is also similar to that of diamond. BN material has comparable hardness to diamond and superior resistance than diamond. It can be a new type of high-temperature resistant super-hard material, which is used to make drill bits, abrasives and cutting tools.
Applications of Boron Nitride (BN) ceramics
Boron Nitride (BN) can be used to produce crucibles for melting semiconductors and high-temperature vessels for metallurgy, amorphous belt throwing nozzles, semiconductor heat dissipation insulating parts, high-temperature bearings, thermowells, glass forming molds and so on.
Material Properties of Boron Nitride (BN) Ceramics
Boron Nitride (BN) has chemical corrosion resistance which is not eroded by inorganic acid and water.
In hot concentrated alkali, the boron nitrogen bond is broken.
Above 1200 ℃, BN begins to oxidize in air.
The melting point of NB is 3000℃.
Its sublimation begins when the temperature is slightly lower than 3000 ℃.
Under vacuum, the decomposition begins at about 2700 ℃.
BN is slightly soluble in hot acid and insoluble in cold water. Its density is greater than 2.0 and its bending strength is 30MPa.
The service temperature of BN is not higher than 900 ℃ in oxidizing atmosphere, while it can reach 2800 ℃ in inactive reducing atmosphere. However, the lubricating performance of BN is poor at normal temperature.
Most properties of BN are better than that of carbon materials.
As for hexagonal boron nitride (BN), it has low friction coefficient, good high-temperature stability, good heat shock resistance, high strength, high thermal conductivity, low expansion coefficient, high resistivity, corrosion resistance, microwave or infrared transmission.
Characteristics of Boron Nitride (BN) ceramics
•Excellent machinability: it can be easily processed into any geometry.
•Good lubricity: BN can improve the friction coefficient of lubricating oil and reduce the possibility of wear.
•High resistivity: it is not included the aerosol, paint and zsbn.
•Low density: Its density range is from 2.1 g/cm3 to 3.5 g/cm3.
•High thermal conductivity: It has excellent thermal conductivity. However, the thermal cycling behavior is very low in application.
•Anisotropy: the thermal conductivity of different planes is different with respect to the pressing direction.
•Good corrosion resistance and chemical inertness: BN is insoluble in common acid.
•High temperature resistance: the melting point of BN is 2973 °C.
•Nonwetting: BN material can be used as a ceramic crucible for melting glass and metal.
•High dielectric breakdown strength (>40 KV/mm)
•Low dielectric constant（k=4）
Application
•Socket plate for high temperature furnace
•Molten glass and metal crucibles
•Electrical insulators for high temperature and high pressure
•Plasma chamber lining and accessories
•Nozzles for non-ferrous metals and alloys
•Thermocouple protection tube and sheath
•Laser support
•Plasma arc welding equipment, diffusion source wafer, semiconductor crystal growth equipment and processing equipment
•Heat sink in high-power electronic application
Processing of Boron Nitride (BN) ceramic products
Boron Nitride (BN) ceramic material has excellent processing performance, which can be easily processed into desired geometry. When processing BN ceramics, we should pay attention to:
1) Standard taps and screw dies can be used to process threads during grinding.
2) Machining tools include standard high-speed steel cutting tools. For composite materials, cemented carbide tools or diamond tools are recommended.
3) The processing of BN material must be kept dry.
4) Cutting tools of BN material must be kept sharp.
5) Please avoid applying excessive pressure when processing materials.
