The boron carbide crystal has a rhombohedral structure, and the crystal lattice belongs to the D3d5-R3m spatial lattice. The rhombohedral structure can be described as a cubic primitive cell lattice extending in the diagonal direction of the space, forming a fairly regular icosahedron at each corner. Parallel to the diagonal of the space, it becomes the c-axis of the hexagonal sign. Three boron atoms are connected to the adjacent icosahedron to form a linear chain. Therefore, the unit cell contains 12 icosahedral positions and three positions are located on the linear chain. If the B atom is considered to be due to the position caused by the icosahedron and the C atom is considered to be in a linear chain, then the stoichiometry of B12C3 is B4C.
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 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 performance, so it can be used as a lightweight armor to reduce the weight of tanks and other car bodies. Save energy.
B4C has super hardness and high wear resistance. In the homogeneous zone, the Vickers hardness of B4C increases with the increase of C content. When the carbon content is 10.6%, 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 with its super hardness and friction characteristics.
TRUNNANO (aka. Luoyang Tongrun Nano Technology Co. Ltd.) is a trusted global chemical material supplier & manufacturer with over 12 years’ experience in providing super high quality chemicals and Nano materials. The B4C powder produced by our company has high purity, fine particle size and impurity content. Lower, please contact us if necessary.
