Superhard materials (review). Part I. Crystal structure, synthesis, properties. Application of materials obtained at high temperature and pressure

An overview of superhard crystalline materials (microhardness or Vickers hardness of which is more than 40 GPa) obtained at high temperature and pressure is presented. Superhard materials, first of all, include the hardest ― diamond, characterized by a hardness of 70‒110 GPa (natural diamond). The hardness of polycrystalline and nanocrystalline diamonds is 10 and 25 % higher. Cubic boron nitride (as well as diamond) is obtained in high-pressure installations, its hardness reaches 62 GPa. Based on phase of fullerene C60 (hardness 140‒170 GPa), phase boron: α-B 12 , β-B 106 и γ-B 28 (42‒50 GPa), rombo eticheskie subnitride вora В 13 N 2 (40 GPa), the boron carbonitrides: β-BC 2 N, c -BC 2 N и z -BC 2 N (70,8‒76 GPa), a cubic boron carbide with ВС 5 (49 GPa), carbon nitrides: α-С 3 N 4 , β-С3N 4 , c -С 3 N 4 , p -С 3 N 4 и cs -С 3 N 4 (62,3‒92,0 GPa) they are metastable and it is not yet possible to obtain bulk materials based on them. Ill. 3. Ref. 122. Tab. 5.