Superhard material comparable in hardness to diamond

Superhard boron suboxides, with hardness close to that of diamond, were synthesized from boron/boron oxide mixtures. Such hardness is expected when a material’s molar volume approaches the value characteristic for diamond. These materials consist of boron-rich phases belonging to the boron-oxygen system. The phase which contains 4 at. % oxygen and a crystal structure related to β-rhombohedral boron can scratch diamond faces. During scratching of diamond the suboxide is worn also, and the wear debris is amorphized. Wear on the {100} diamond faces results from a cleavage mechanism which leaves a rough surface covered with cleaved {111} microfaces. The {100} faces are more easily abraded than the {111} diamond faces. Wear on {111} faces consumes much more energy and leaves grooves of plastically deformed diamond.