Assertion: boron | /r/HasProperty | 4 c
Facets:
Source sentences:
text: Boron carbide, (B 4 C), crystalline compound of boron and carbon.
text: Boron combines with carbon to form boron carbide (B 4 C), an extremely hard substance that is used as an abrasive and as a reinforcing agent in composite materials.
text: Boron Carbide (B 4 C) is one of the hardest materials known, ranking third behind diamond and cubic boron nitride.