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The Knowledge That You Should Know About Boron Nitride BN Powder

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Update time : 2019-11-19 15:57:08
What is Boron Nitride?
Boron nitride was introduced more than 100 years ago. The earliest application was hexagonal boron nitride as a high-temperature lubricant. h-BN not only has its structure but also its performance is very similar to graphite, and it is white, so it is commonly called white graphite.

Boron nitride is a crystal composed of a nitrogen atom and boron atom. This chemical powder composition is 43.6% boron and 56.4% nitrogen with four different variants: hexagonal boron nitride (HBN), rhombohedral boron nitride (RBN), cubic boron nitride (CBN) and wurtzite boron nitride (WBN).

Cubic boron nitride is usually black, brown, or dark red crystal, which is a sphalerite structure with good thermal conductivity. Hardness is second only to diamond and is a superhard material commonly used as tool material and abrasive.
Hexagonal boron nitride is with very low friction coefficient, excellent high-temperature stability, good thermal shock resistance, high strength, high thermal conductivity, small expansion coefficient, high electrical resistivity, corrosion resistance, microwave penetration or penetration infrared.
 
The Preparation Methods of Boron Nitride:
The boron nitride usually produced is a graphite type structure, commonly known as white graphite. The other is a diamond type, which is similar to the principle that graphite is converted into a diamond. Graphite-type boron nitride can be converted into diamond-type boron nitride at high temperature (1800 ° C) and high pressure (8000 MPa) [5-18 GPa]. It is a new high temperature resistant superhard material for the production of drill bits, abrasive tools, and cutting tools.

There are several methods to prepare boron nitride: High temperature and high-pressure synthesis method, chemical vapor-phase synthesis method, hydrothermal synthesis method, benzene heat synthesis method, self-propagation technology, carbon thermal synthesis technology, ion beam sputtering technique, laser-induced reduction method.

Hydrothermal technology has two characteristics, one is its relatively low temperature, and the other is in a closed container to avoid component evaporation. As a low-temperature low-pressure synthesis method, it is used to synthesize cubic boron nitride at low temperatures.

In 1979, Sokolowski successfully used pulse plasma technology to prepare a boron nitride (CBN) film at low temperature and low pressure. The equipment used was simple, and the process was easy to realize, so it was rapidly developed. A variety of vapor deposition methods have emerged, traditionally referred to as thermal chemical vapor deposition.
 
The Application of Boron Nitride:
Boron nitride can be used in the following fields:
1. Metal-formed release agent and metal-drawn lubricant.
2. Special electrolysis and resistance materials in a high-temperature state.
3. High-temperature solid lubricant additive, extrusion anti-wear additives, additives for the production of ceramic composites, refractory materials, and antioxidant additives, especially used for the corrosion resistance of molten metals, heat-enhancing additives, high-temperature resistant insulation materials.
4. Additives for polymers such as heat seal desiccants and plastic resins.
5. Pressed into various shapes of BN products, which can be used for high temperature, high voltage, insulation, and heat dissipation parts.
6. Thermal shielding materials in aerospace.
7. With the participation of the catalyst, boron nitride can be converted into hard, diamond-like cubic boron nitride by high temperature and high-pressure treatment.
8. Structural materials for atomic reactors.
9. The jets of aircraft and rocket engines.
10. High-voltage high-frequency electricity and plasma arc insulators.
11. Packaging materials to prevent neutron radiation.
12. Ultra-hard materials made of BN can be made into high-speed cutting tools and geological exploration, oil drilling drill bits.
13. Metallurgical separation ring for continuous casting steel, flow notch of amorphous iron, release agent for continuous casting aluminum (various optical glass release agents)
14. Do a variety of capacitor film aluminum plating, tube aluminum plating, display aluminum plating, and other evaporation boats.
15. Various fresh-keeping aluminum-plated bags, etc.
16. Various laser anti-counterfeiting aluminum plating, trademark hot stamping materials, various cigarette labels, beer labels, packaging boxes, cigarette packaging aluminum plating, and so on.
17. Cosmetics are used for lipstick filling, non-toxic, lubricious, and shiny.
 
The Future Prospects of Boron Nitride:
Due to the high hardness of steel materials, a large amount of heat is generated during processing. Diamond tools are easily decomposed at high temperatures and efficiently react with transition metals, while c-BN materials have good thermal stability and are not easily generated with iron group metals or alloys. The reaction can be widely applied to the precision processing and grinding of steel products. 

In addition to excellent wear resistance, c-BN is also excellent in heat resistance. It can also cut heat-resistant steel, iron alloy, hardened steel, etc. at a relatively high cutting temperature, and can cut high hardness chill rolls and seepage. Carbon quenching materials and Si-A1 alloys that are very abrasive to tool wear. In fact, tools and abrasive tools made of sintered bodies of c-BN crystals (high-temperature and high-pressure synthesis) have been used in high-speed precision machining of various hard alloy materials.

In optical applications, the c-BN film is suitable for use as a surface coating for some optical components because of its high hardness and high transmittance from ultraviolet (about 200 nm) to far infrared. Coating of window materials such as zinc selenide (ZnSe) and zinc sulfide (ZnS). In addition, it has good thermal shock resistance and quotient hardness and is expected to be the ideal window material for high-power lasers and detectors.

c-BN is the third-generation semiconductor material with the best performance. It can be used not only for the production of electronic devices operating under extreme conditions such as high temperature, high frequency, and high power but also has broad application prospects in deep ultraviolet luminescence and detectors. In fact, Mishima et al. first reported that c-BN LEDs fabricated under high temperature and high-pressure conditions could work at 650 ° C. 

Under forward bias, the diode emits visible blue light, and the spectral measurement shows that it is the shortest. The wavelength is 215 nm (5.8 eV). C-BN has a thermal expansion coefficient similar to that of GaAs and Si, high thermal conductivity and low dielectric constant, good insulation performance, and good chemical stability, making it a heat sink material and an insulating coating layer for integrated circuits. Besides, C-BN has a negative electron affinity and can be used for cold cathode field emission materials, and has broad application prospects in the field of large-area flat panel display.