boron nitride is a crystal composed of nitrogen atoms and boron atoms. The chemical composition is 43.6% boron and 56.4% nitrogen, and it has four different varieties: hexagonal boron nitride (HBN), rhombohedral boron nitride (RBN), cubic boron nitride (CBN) and wurtzite boron nitride (WBN).
Chinese name
Boronnitride
mbth
boron nitride
regulated information
unregulated
chemical formula
BN
molecular weight
24.818
numbering system
CAS number: 143-11-5. 8
PubChemNo.: 24855457[1]
Development history
Boron nitride came out more than 1 years ago. Its earliest application was hexagonal boron nitride as a high-temperature lubricant. Its structure and properties are very similar to graphite, and it is white, so it is commonly known as white graphite.
boron nitride (BN) ceramics were discovered as early as 1842. Foreign countries have done a lot of research work on BN materials since the Second World War, and it was not developed until the BN hot pressing method was solved in 1955. American Diamond Company and United Carbon Company first put into production, and produced more than 1 tons in 196.
in p>1957, R. H. wentrof was the first to successfully trial-produce CBN. in 1969, the American general electric company sold it as Borazon, and in 1973, the United States announced that it had made CBN tools. [2]
In 1975, Japan imported technology from the United States and also prepared CBN tools.
In p>1979, the collapsed C-BN thin films were successfully prepared by pulsed plasma technology at low temperature and low pressure for the first time.
in the late 199s, people have been able to prepare c-BN thin films by various physical vapor deposition (PVD) and chemical vapor deposition (CVD) methods.
in China, the development has advanced by leaps and bounds. In 1963, the research on BN powder was started, and it was successfully developed in 1966. In 1967, it was put into production and applied to China's industry and cutting-edge technology.
physical and chemical properties
material properties
CBN is usually black, brown or dark red crystal with sphalerite structure and good thermal conductivity. Hardness is second only to that of diamond, and it is a superhard material, which is often used as tool material and abrasive. [3]
boron nitride has chemical erosion resistance, and is not corroded by inorganic acids and water. The boron-nitrogen bond was broken in hot concentrated alkali. Oxidation begins in air above 12℃. Decomposition begins at about 27℃ in vacuum. Slightly soluble in hot acid, insoluble in cold water, relative density 2.29. The compressive strength is 17MPa. The maximum service temperature is 9℃ in oxidizing atmosphere, but it can reach 28℃ in inactive reducing atmosphere, but the lubrication performance is poor at room temperature. Most properties of boron nitride are better than those of carbon materials. For hexagonal boron nitride: low friction coefficient, good high-temperature stability, good thermal shock resistance, high strength, high thermal conductivity, low expansion coefficient, high resistivity, corrosion resistance, microwave or infrared permeability.
material structure
boron nitride is a hexagonal crystal system, most commonly graphite crystal lattice, and there are also amorphous variants. Besides hexagonal crystal form, boron nitride has other crystal forms, including rhombohedral boron nitride (r-BN), cubic boron nitride (c-BN) and wurtzite boron nitride (w-BN). People even found two-dimensional boron nitride crystals like graphite. [4]
Ecological data
are usually slightly harmful to water bodies. Do not expose undiluted or large quantities of products to groundwater, waterways or sewage systems, and do not discharge materials into the surrounding environment without government permission. [1]
calculated chemical data
1. calculated reference value of hydrophobic parameters (XlogP): none
2. number of hydrogen bond donors:
3. number of hydrogen bond acceptors: 1
4. number of rotatable chemical bonds:
5. number of tautomers: none
. Number of isotope atoms:
11, number of confirmed atomic stereocenters:
12, number of uncertain atomic stereocenters:
13, number of confirmed chemical bond stereocenters:
14, number of uncertain chemical bond stereocenters:
15, number of * * valence bond units: 1 [ The other is diamond type, which is similar to the principle of graphite transforming into diamond. Graphite type boron nitride can be transformed into diamond type boron nitride at high temperature (18℃) and high pressure (8Mpa)[5~18GPa]. It is a new type of superhard material with high temperature resistance, which is used to make drills, abrasives and cutting tools.
manufacturing method
high temperature and high pressure synthesis method
in p>1957, Wentorf synthesized cubic BN for the first time. When the temperature is close to or higher than 17℃ and the lowest pressure is 11 ~ 12 GPA, pure hexagonal boron nitride (HBN) is directly transformed into cubic boron nitride (CBN). Subsequently, it was found that the transition temperature and pressure could be greatly reduced by using catalysts. Commonly used catalysts are alkali and alkaline earth metals, alkali and alkaline earth nitrides, alkaline earth fluorinated nitrides, ammonium borates and inorganic fluorides. Among them, ammonium borate as catalyst needs the lowest temperature and pressure, and the required pressure is 5GPa at 15℃, while the temperature range is 6 ~ 7℃ at 6GPa. It can be seen that although the transition temperature and pressure can be greatly reduced by adding catalyst, the required temperature and pressure are still high. Therefore, its equipment is complicated and its cost is high, so its industrial application is limited.
chemical vapor synthesis method
In p>1979, Sokolowski successfully prepared cubic boron nitride (CBN) films by pulsed plasma technology at low temperature and low pressure. The equipment used is simple and the process is easy to realize, so it has developed rapidly. A variety of vapor deposition methods have emerged. Traditionally, it mainly refers to thermochemical vapor deposition. The experimental device is generally composed of a heat-resistant quartz tube and a heating device. The substrate can be heated by a heating furnace (hot wall CVD) or by high-frequency induction heating (cold wall CVD). The reaction gas decomposes on the surface of the high-temperature substrate, and at the same time, a chemical reaction occurs to deposit a film. The reaction gas includes BCl3 or the mixed gas of B2H4 and NH3.
hydrothermal synthesis method
This method uses water as the reaction medium in a high-temperature and high-pressure reaction environment in an autoclave, so that usually insoluble or insoluble substances are dissolved, and the reaction can also be recrystallized. Hydrothermal technology has two characteristics, one is its relatively low temperature, and the other is that it is carried out in a closed container, which avoids the volatilization of components. As a low-temperature and low-pressure synthesis method, it is used to synthesize cubic boron nitride at low temperature.
thermal synthesis of benzene
as a new synthesis method of low-temperature nano-materials in recent years, thermal synthesis of benzene has attracted wide attention. Benzene is an excellent solvent for solvothermal synthesis because of its stable * * * yoke structure. Recently, it has been successfully developed into a benzene thermal synthesis technology, such as the reaction formula:
BCl3+Li3N→BN+3LiCl
or BBr3+Li3N→BN+3LiBr
. The benzene thermal synthesis technology can be prepared at relatively low temperature and pressure. This method realizes the preparation of cubic boron nitride at low temperature and low pressure. However, this method is still in the experimental research stage, and it is a synthesis method with great application potential.
self-propagating technology
uses the necessary energy provided by the outside to induce a highly exothermic chemical reaction, and the system reacts locally to form a chemical reaction front (combustion wave), and the chemical reaction proceeds rapidly with the support of its own heat release, and the combustion wave spreads throughout the system. Although this method is a traditional inorganic synthesis method, it has only been reported in recent years for the synthesis of boron nitride.
carbothermal synthesis technology
This method is a method of nitriding boron nitride on the surface of silicon carbide with boric acid as raw material and carbon as reducing agent. The product obtained is of high purity and has great application value for the preparation of composite materials.
ion beam sputtering technology
The mixed product of cubic boron nitride and hexagonal boron nitride is obtained by particle beam sputtering deposition technology. Although there are few impurities in this method, it is difficult to control the reaction conditions, so the morphology of the product is difficult to control, and the research on this method has great development potential.
Laser-induced reduction method
Laser is used as an external energy source to induce redox reaction between reaction precursors and combine B and N to generate boron nitride, but this method also obtains mixed phase. [5]
storage method
boron nitride storage method: it should be stored in a well-ventilated dry warehouse to prevent moisture.
storage method of boron nitride fiber: store in a well-ventilated and dry warehouse. The maximum allowable concentration of boron nitride in air is 6mg/m3. [1]
technical parameters
product classification
average particle size (nm)
specific surface area (m2/g)
bulk density (g/cm3)
crystal form
color
nanometer
5
43.6
.
2. Special electrolytic and resistive materials at high temperature.
3. High-temperature solid lubricants, extrusion antiwear additives, additives for producing ceramic composite materials, refractories and antioxidant additives, especially in the case of corrosion resistance of molten metal, thermal enhancement additives and high-temperature resistant insulating materials.
4. Heat sealing desiccant for transistors and additives for polymers such as plastic resin.
5. boron nitride products pressed into various shapes can be used as high temperature, high pressure, insulation and heat dissipation parts.
6. Thermal shielding materials in aerospace.
7. With the participation of catalyst, it can be transformed into cubic boron nitride as hard as diamond after high temperature and high pressure treatment.
8. Structural materials of atomic reactors.
9. Nozzles of aircraft and rocket engines.
1. Insulator of high voltage and high frequency electric and plasma arc.
11. Packaging materials to prevent neutron radiation.
12. superhard materials made of boron nitride can be made into high-speed cutting tools and drill bits for geological exploration and oil drilling.
13. Metallurgical separation ring for continuous casting steel, runner of amorphous iron, release agent for continuous casting aluminum (various optical glass release agents).
14. Make evaporation boats for aluminum plating of capacitor films, picture tubes and displays.
15. All kinds of fresh-keeping aluminized packaging bags, etc.
16. All kinds of laser anti-counterfeiting aluminizing, trademark bronzing materials, all kinds of cigarette labels, beer labels, packaging boxes, cigarette packaging boxes, and so on.
17. Cosmetics are used as fillers for lipsticks, which are non-toxic, lubricious and shiny.
Future prospects
Due to the high hardness of steel materials, a lot of heat will be generated during machining. Diamond tools are easy to decompose and react with transition metals at high temperature, while c-BN materials have good thermal stability and are not easy to react with ferrous metals or alloys, which can be widely used in precision machining and grinding of steel products. C-BN not only has excellent wear resistance, but also has excellent heat resistance. It can also cut heat-resistant steel, ferroalloy, quenched steel, etc. at a fairly high cutting temperature, and it can also cut high-hardness chilled rolls, carburizing and quenching materials and Si-Al alloys which have serious tool wear. In fact, tools and abrasives made of sintered body of c-BN crystal (synthesized at high temperature and high pressure) have been used in high-speed precision machining of various cemented carbide materials.
as a semiconductor material with a wide band gap (band gap of 6.4 eV), C-BN has high thermal conductivity, high resistivity, high mobility, low dielectric constant, high breakdown electric field, dual-type doping and good stability. Together with diamond, SiC and GaN, C-BN is called the third generation semiconductor material after Si, Ge and GaAs, and their common characteristics are wide band gap and applicability. Compared with SiC and GaN, c-BN and diamond have more excellent properties, such as wider band gap, higher mobility, higher breakdown electric field, lower dielectric constant and higher thermal conductivity. Obviously, as an extreme electronic material, c-BN is superior to diamond. However, as a semiconductor material, diamond has its fatal weakness, that is, the N-type doping of diamond is very difficult (the resistivity of N-type doping can only reach 12 Ω·cm, which is far from the device standard), while c-BN can achieve double doping. For example, in the process of high temperature and high pressure synthesis and thin film preparation, P-type semiconductor can Be obtained by adding Be; N-type semiconductor can be obtained by adding S, C, Si, etc. Therefore, c-BN is the third generation semiconductor material with the best performance, which can be used not only to prepare electronic devices working under extreme conditions such as high temperature, high frequency and high power, but also to have a wide application prospect in deep ultraviolet luminescence and detectors. In fact, it was first reported that the c-BN light-emitting diode made under high temperature and high pressure can work at 65℃. Under forward bias, the diode emits blue light visible to the naked eye. Spectral measurement shows that its shortest wavelength is 215 nm(5.8 eV). C-BN has similar thermal expansion coefficient to GaAs and Si, high thermal conductivity, low dielectric constant, good insulation performance and good chemical stability, which makes it a heat sink material and insulation coating for integrated circuits. In addition, c-BN has negative electron affinity, which can be used as cold cathode field emission materials and has a wide application prospect in the field of large-area flat panel display.
in optical applications, c-BN thin film is suitable as the surface coating of some optical elements, especially as the coating of window materials such as zinc selenide (ZnSe) and zinc sulfide (ZnS), because of its high hardness and high transmittance from ultraviolet (about 2 nm) to far infrared. In addition, it has good thermal shock resistance and quotient hardness, and is expected to become an ideal window material for high-power lasers and detectors. [6]
Generally, boron nitride ceramics have graphite structure, commonly known as white graphite. The other is diamond type, which is similar to the principle that graphite is converted into diamond. Graphite boron nitride can be transformed into diamond boron nitride at high temperature (18℃) and high pressure (8Mpa). The length of B-N bond of boron nitride (156pm) is similar to that of C-C bond of diamond (154pm), and the density is similar to that of diamond. Its hardness is equivalent to that of diamond, but its heat resistance is better than that of diamond. It is a new type of superhard material with high temperature resistance, which can be used to manufacture drills, abrasives and cutters. Excerpt from: www.sdboaoxcl.comCBN is usually black, brown or dark red crystal with sphalerite structure and good thermal conductivity. Hardness is second only to diamond, which is a kind of super-hardness.