Basic Properties, Synthesis and Typical Properties of Boron Carbide

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What is Boron Carbide?

Boron Carbide Powder belongs to the trigonal system. The unit cell contains 12 B and 3 C. The unit cell’s stereo diagonally connected C atoms are in an active configuration. They can be substituted by B atoms, forming a replacement solution.

B4C’s molecular weight is 52.25 with C21.74% (and B78.25%), is usually gray or black and has a density of 2.51g/cm3, the Mohs Hardness is 9.35 and the microhardness is 49GPa. This powder is very efficient in grinding and can achieve 60%-70% the grinding efficiency of diamond. This is greater than 50% SiC, but is also 1-2x that of corundum.

B4C Powder has a melting temperature of 2450°C (decomposition). The coefficient for expansion at 1000degC (4.5×10-6degC-1) is 4.5×10-6degC-1. Thermal conductivity is 121.4W/m*k for 100degC, and 62.79W/m*k for 700degC. Hot-pressed products of B4C are used for wear-resistant and temperature-resistant parts. B4C is mostly used in the refractory industries as an anti-oxidant additive. Unshaped materials enhance the strength and resistance to corrosion of the body.

The properties of Boron Carbide and their Synthesis

B4C is commonly synthesized by reducing boron anhydride and excess carbon.


The synthesis reaction may be carried out either in an electric arc or a muffle oven. In a resistance-type furnace, the best way to synthesize B4C is by heating a mixture of boron hydride B2O3 with carbon C. This mixture should be heated at a lower temperature than B4C’s decomposition temperatures. B4C is broken down into boron and carbon rich phase in the electric-arc furnace because of the high temperature. The reaction product may contain a lot of free C (20%-30%). As a result, the B4C obtained is of slightly inferior quality.

In order to synthesize B4C using an electric arc, boric acids (with a content greater than 92%), artificial graphite with a fixed carbon of greater than 95%, and petroleum coke with 85% fixed carbon are used. The theoretical dosage is calculated based on the reaction formula. The theoretical amount is approximately 2% higher. Each of artificial graphite and petroleum coke accounts for 50% of total carbon addition, which is then 3%-4% more than the theoretical amount. Add the three prepared raw materials to the arc and mix them in a ball-mill. B4C can then be obtained by carbonizing the furnace and reducing it between 1700-2300. Finaly, the frit will be sorted and cleaned, then crushed, ground, picked, sedimented, classified, etc. to produce B4C in various particle sizes.

(aka. Technology Co. Ltd., a trusted global chemical materials supplier and manufacturer has over 12 years experience in providing high-quality nanomaterials and chemicals. Our company’s B4C powder is of high purity with a fine particle size. If you need lower, please call us.

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