ACM - Model B4C - Boron Carbide

With a Mohs hardness between 9 and 10, boron carbide is one of the hardest synthetic substances known, being exceeded only by cubic boron nitride and diamond. As an abrasive, it is used in powdered form in the lapping (fine abrading) of metal and ceramic products, though its low oxidation temperature of 400–500° C (750–930° F) makes it unable to withstand the heat of grinding hardened tool steels. Because of its hardness, together with its very low density, it has found application as a reinforcing agent for aluminum in military armour and high-performance bicycles, and its wear resistance has caused it to be employed in sandblasting nozzles and pump seals. A neutron absorber, boron carbide is used in powdered or solidified form to control the rate of fission in nuclear reactors.

Boron Carbide Properties

• Low thermal conductivity
• Susceptible to thermal shock failure
• Outstanding hardness
• Extremely brittle
• Semiconductor
• Good thermal-neutron capture

The ability of boron carbide to absorb neutrons without forming long-lived radionuclides makes it attractive as an absorbent for neutron radiation arising in nuclear power plants and from anti-personnel neutron bombs. Nuclear applications of boron carbide include shielding, control rod and shut down pellets. Within control rods, boron carbide is often powdered, to increase its surface area.

Other applications:

• Abrasives for lapping and ultrasonic cutting
• Anti-oxidant in carbon-bonded refractory mixes
• Armor
• Nuclear applications such as reactor control rods and neutron absorbing shielding
• Wear parts such as blasting nozzles, wire-drawing dies, powdered metal and ceramic forming dies, thread guides