The physical and chemical properties, application and chemical stability of boron carbide

Overview of Boron Carbide B4C Powder

Boron carbide, also known as black diamond, is an inorganic substance with a chemical formula of B4C, usually gray-black micropowder. It is one of the three hardest materials known (second only to diamond and cubic boron nitride) and is used in tank armor, bulletproof vests and many industrial applications. Its Mohs hardness is about 9.5.

Boron Carbide B4C Powder was discovered in the 19th century as a by-product of metal boride research and was not scientifically studied until the 1930s. Boron carbide can be obtained by reducing diboron trioxide with carbon in an electric furnace.

Boron carbide can absorb a large number of neutrons without forming any radioisotopes, so it is an ideal neutron absorber in nuclear power plants, and the neutron absorber mainly controls the rate of nuclear fission. Boron carbide is mainly made into a controllable rod shape in the nuclear reactor field, but sometimes it is made into a powder because of the increase in surface area.

Because of its low density, high strength, high temperature stability and good chemical stability. It is used in wear-resistant materials, ceramic reinforcing phases, especially in lightweight armor, reactor neutron absorbers, etc. In addition, compared with diamond and cubic boron nitride, boron carbide is easy to manufacture and low in cost, so it is more widely used. It can replace expensive diamond in some places and is commonly used in grinding, grinding, drilling, etc.

Basic properties and applications of boron carbide

1) Low density

The density of B4C is relatively small, 2.52g/cm3. In the homogeneous zone, the relationship between density and carbon content can be expressed by the empirical formula (9) as:

ρ=2.4224+0.00489C(9)

Due to the low density of boron carbide, when a higher density is obtained, its performance can reach the standard of boron carbide, high strength, high hardness and other excellent properties, so it can be used as a lightweight armor to reduce the weight of tanks and other vehicles. Save energy.

2) Hardness and wear resistance

B4C has super hardness and extremely high wear resistance. In the homogeneous zone, the Vickers hardness of B4C increases with the increase of C content. When the carbon content is 0.106, the hardness is 29.1 GPa; when the carbon content is 20%, the hardness 21 can reach 37.7 GPa. Its hardness is still high at high temperature (>30GPa). The change of hardness with temperature can be expressed by empirical formula (10):

H=H0-exp(-aT)(10)

In the formula: H0—the hardness at room temperature;

T— is the temperature;

a—is a constant related to carbon.

This formula is suitable for 20~1700℃. It should be pointed out that B4C is one of the hardest materials in the world, second only to diamond and cubic BN.

The wear resistance of B4C increases with the increase of temperature. In the range of 20 to 1400 ℃, the friction coefficient decreases with the increase of temperature, and it drops to 0.05 at about 1400 ℃, and the friction rate also continues to decrease. B4C has been used as a sandblasting nozzle due to its super hardness and friction characteristics. Diamond nozzles and nozzles of water jet cutters, such as wear-resistant materials; are widely used in armor materials for tanks and aircrafts in the military [39,40]; With the advancement of technology, the demand for high-precision grinding increases, B4C Increasingly show its superiority. In recent years, its dosage has been increasing. At the same time, B4C can also be used to grind hard alloys, ceramics and gem hard materials, free abrasives for friction or abrasives for ultrasonic processing of these superhard materials. However, compared with Europe and the United States, my country's consumption in this area is still very small.

3) Thermal expansion coefficient and specific heat capacity

The melting point of boron carbide is 2450°C, the boiling point is 3000°C, the coefficient of thermal expansion is 5.73×10-6/°C (28~1770°C), and the specific heat capacity calculation formula (11):

C=22.99+5.40×10-3T-10.72×105T-2(11)

Chemical stability of boron carbide

Boron carbide is one of the most stable compounds, and it is not easy to oxidize below 600°C. When the temperature is above 600°C, the surface is oxidized into a B2O3 film, which prevents further oxidation of B4C. So B4C is now used as an antioxidant in refractories. B4C generally does not react with chemical reagents at room temperature; B4C and Br form tribromide compounds above 800℃; B4C reacts with metal oxides at high temperatures to form metal borides and carbon monoxide, and the resulting FeB film has high microhardness ( HV=24GPa) and abrasion resistance. Therefore, B4C can be used for boronization of steel and alloys.

Application of Boron Carbide B4C Powder

Control nuclear fission: It can absorb a large number of neutrons without forming any radioactive isotopes. It is an ideal neutron absorber for nuclear power plants. Neutron absorbers mainly control the rate of nuclear fission. Boron is mainly made into controllable rods in the field of nuclear reactors, but sometimes it is made into powder due to the increase in surface area.

Abrasive: Because boron carbide B4C powde has been used as a coarse abrasive for a long time. Because of its high melting point, it is not easy to cast into artificial products, but the powder can be smelted into simple shapes. high temperature. Used for grinding, grinding, drilling and polishing hard materials such as cemented carbide and gems.

Coating paint: Boron carbide B4C powde can also be used as a ceramic coating for warships and helicopters. It is light in weight and can resist the penetration of armor-piercing projectiles through the hot-press coating, forming an overall defense layer.

Nozzle: Boron carbide B4C powde can be used as a spray gun nozzle in the ordnance industry. Boron carbide is extremely hard and wear-resistant, does not react with acid and alkali, is resistant to high temperature/low temperature, and is resistant to high pressure. Boron carbide is also used to make metal borides and smelt sodium-boron, boron alloys and special welding.

Boron carbide B4C powder price

The price of boron carbide B4C powde varies randomly with factors such as production costs, transportation costs, international conditions, exchange rates, and market supply and demand. Tanki New Materials Co., Ltd. aims to help various industries and chemical wholesalers find high-quality, low-cost nanomaterials and chemicals by providing a full set of customized services. If you are looking for boron carbide B4C powde, please feel free to contact us for the latest boron carbide B4C powde prices.

Boron carbide B4C powder supplier

As a global boron carbide B4C powde supplier, Tanki New Materials Co., Ltd. has extensive experience in the performance, application and cost-effective manufacturing of advanced engineering materials. The company has successfully developed a series of powder materials (including chromium carbide, aluminum carbide, titanium carbide, etc.), high-purity targets, functional ceramics and structural devices, and provides OEM services.