Fundamental Properties, Use and Chemical Stability of Boron Carbide

Boron carbide crystal is rhombohedral structure, the lattice belongs to the D3d5-R3m space lattice. Its rhombohedral structure is shown in Figure 7, which can be described as a cubic proto-cell lattice extending in the diagonal direction of space, forming an appropriately regular icosahedron at each corner. Parallel to the diagonal of space, it becomes the c-axis of the hexagonal symbol, which is composed of three boron atoms and adjacent icosahedron connected to each other to form a linear chain. Thus, the unit cell contains 12 icosahedral orientations, three of which lie on linear chains. If the B atom is considered to be in the orientation caused by the icosahedron and the C atom is considered to be in a linear chain, then the chemical accounting of B12C3 is B4C. 1. Basic properties of boron carbide and its use 1) Low density B4C has a small density of 2.52g/cm3. In the homogeneous phase region, the relationship between density and carbon content can be shown by the following formula (9): ρ = 2.4224 + 0.00489C%(9) Because of the low density of boron carbide, in the case of obtaining a higher density, its function can reach the standard high strength, high hardness and other excellent functions of boron carbide, so it can be used as light armor to reduce the weight of tanks and other car bodies, saving energy consumption. 2) Hardness and wear resistance B4C has super hardness and high wear resistance, in the homogeneous phase region, the Vickers hardness of B4C is added with the addition of C content. When the carbon content is 10.6, the hardness is 29.1GPa; when the carbon content is 20%, the hardness of 21 up to 37.7GPa. Its hardness is still very high (>30GPa) at high temperatures. The change of hardness with temperature can be indicated by the experience formula (10): H=H0-exp(-aT)(10) Where: H0-hardness at normal temperature; T-temperature; a-is a constant related to carbon content. This formula is suitable for 20~1700 ℃. The demand points 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 20~1400 ℃, the conflict coefficient decreases with the increase of temperature, and decreases to 0.05 at about 1400 ℃, and the conflict rate also decreases. B4C has been used as a sand spray tip for its ultra-hardness and conflict characteristics. Diamond nozzles, nozzles of water conservancy jet cutters, and other wear-resistant materials; Armor materials widely used in military affairs for tanks, airplanes, etc. [39,40]; With the progress of skills and the demand for high-precision grinding, B4C is increasingly showing its advantages. In recent years, its dosage has been continuously added. Together, B4C can also be used to grind hard alloy, ceramics and gem hard materials, conflict with free abrasive or ultrasonic processing of these super-hard materials with abrasive, but compared with Europe and the United States in this area in China is still very small. 3) Thermal expansion coefficient and specific heat capacity The melting point of boron carbide is 2450 ℃, the boiling point is 3000 ℃, the thermal expansion coefficient is 5.73 × 10-6/℃(28~1770 ℃), and the specific heat capacity calculation formula (11): C=22.99+5.40×10-3T-10.72×105T-2(11) 2. Chemical stability Boron carbide is one of the most stable compounds, below 600 degrees Celsius is not easy to produce oxidation reaction; and the temperature above 600 degrees Celsius, because the appearance of oxidation into B2O3 film, to prevent the further oxidation of B4C. So B4C is now used as an antioxidant in refractory materials. Under normal temperature B4C generally does not react with chemical reagents; above 800 DEG C B4C and Br constitute three bromine compounds; high temperature B4C and metal oxide reaction to generate metal borides and carbon monoxide, the generated FeB thin films with high microhardness (HV = 24GPa) and wear resistance. Therefore, B4C can be used for the boronization of steel and alloys.

Fundamental properties, synthesis and performance of boron carbide

Boron carbide is a general term for carbon (C) and boron (B) compounds, and two compounds B4C and B6C are generated according to different cooperative conditions. Generally speaking, boron carbide is generally referred to as B4C. Fundamental properties of 1. boron carbide B4C is a trigonal crystal system. There are 12 B atoms and 3 C atoms in the unit cell. The connecting three-dimensional diagonal composed of C atoms in the unit cell is equipped. C is in an active state and can be replaced by B atoms to form a replacement solid solution. It may be separated from the crystal lattice to form a high boron compound with defects. B4C has 52.25 molecular weight, C21.74% and B78.26%, generally dark to black, density 2.519g/cm3, Mohs hardness 9.36, microhardness 50GPa, second only to diamond and cubic boron nitride. Therefore, B4C powder has very high grinding ability, and its grinding power can reach 60%-70% of diamond, higher than SiC50%, and 1-2 times of corundum grinding ability. B4C melting point 2450 degrees C (differentiation). The coefficient of expansion between 1000°C is 4.5 x 10-6°C -1. The thermal conductivity is 121.4 W/m · k at 100 ℃ and 62.79 W/m · k at 700 ℃. B4C is primarily used as an abrasive tool, and hot-pressed B4C products can be used as wear-resistant and heat-resistant components. In the refractory industry, B4C is primarily used as an additive, such as adding to carbon-bonded refractory materials for antioxidant effect, adding to amorphous materials to improve the strength and corrosion resistance of the blank. Composition and Typical Function of 2. Boron Carbide The industrially common method of composing B4C powder is to recover the boric anhydride with an excess of carbon: 2B2O3 + 7C → B4 + 6CO ↑ The composition reaction can be carried out in a resistance furnace or an electric arc furnace. When the composition is carried out in a resistance furnace, B4C containing little free C (sometimes containing 1%-2% free boron) can be obtained by heating boron anhydride B2O3 and carbon C and the mixture at a differentiation temperature lower than B4C. It is a better composition method. When the composition is carried out in an electric arc furnace, the arc temperature is appropriately high, however, B4C is differentiated into carbon-rich phase and boron at about 2200 ℃, and boron will transpiration at high temperature to form reaction products containing a large amount of free C(20%-30%), so the quality of B4C obtained is slightly poor. When B4C is composed of electric arc furnace, boric acid (content greater than 92%), artificial graphite (fixed carbon greater than 95%) and petroleum coke (fixed carbon greater than 85%) are generally selected as materials. According to the theoretical dosage of reaction calculation, the participation amount of boric acid is about 2% higher than the theoretical dosage, artificial graphite and petroleum coke each account for 50% of the total carbon participation amount, and then 3%-4% higher than the theoretical dosage, the prepared three materials are mixed in a ball mill, and B4C can be obtained by participating in an electric arc furnace for recovery and carbonization at 1700-2300 ℃. Finally, B4C of various particle sizes can be obtained by sorting and washing, crushing, grinding, pickling, sedimentation classification and other processes.

Contact letter about the name change of Mudanjiang Qianjin Boron Carbide Co., Ltd.

Dear Partners: Thank you very much for your long-term trust and support to us! "Mudanjiang Qianjin Boron Carbide Co., Ltd." due to development needs, on August 15, 2020 has been moved to Sichuan asbestos county and officially changed its name to "asbestos berson technology abrasives Co., Ltd.", since August 15, 2020 officially opened, special contact to your company, the content is as follows: 1. Due to the overall relocation, your company will have doubts about the product quality, service attitude and price of "Asbestos Bosen Technology Abrasives Co., Ltd.". We have made a commitment to this. On the basis of ensuring the product quality, there will be certain price concessions. Please discuss the specific price concessions with Huang Qian (General Manager 13069799077) in detail; 2. The relevant information of Asbestos Berson Technology Abrasive Co., Ltd. is as follows: Company Name: Asbestos Bosen Technology Abrasive Co., Ltd. Unified Social Credit Code: 915118243144104086 Company address: Zhuma Industrial Park, Huilong Township, Shimian County Legal Representative: Huang Baisen Bank: Asbestos County Sub-branch of Agricultural Bank of China Account number: 22544101040016478 Line number: 103677554411 Tel: 0835-8885118