Hardening Effects in Superhard Transition-Metal Borides

CONSPECTUS:Mechanical hardness is a physical property used to gauge the applications of materials in the manufacturing and machining industries.Because of their high hardness and wear resistance,superhard materials(Vickers hardness,Hv≥40 GPa)are commonly used as cutting tools and abrasives.Although diamond is the hardest known material used for industrial applications,its synthesis requires both high pressure and high temperature.Interest in the field of superhard materials research has led to the search for alternatives with high hardness and thermal stability at low cost.The discovery of novel ultraincompressible,superhard materials has largely developed through trial and error along two paths.In one approach,researchers combine light elements,such as boron,carbon,nitrogen,and oxygen,often at high pressure,to replicate the highly directional,dense,covalent bonds of diamond.In the second approach,these light elements(B,C,N,and O)are combined with highly incompressible,electron-rich transition metals to form dense covalently bonded networks at ambient pressure.