Synthesis of novel transition metal carbides at high pressure and temperature

The driving force in the field of high pressure research has been the search for new super-hard materials with improved chemical and thermal stability comparable to or more than that of diamond. Super hard materials are those whose hardness is above 40 GPa. Hardness of diamond is about 90 GPa. There are three generic conditions that are to be met for a material to be hard namely: it must have high bulk modulus i.e., it should resist volume deformation; it should not deform in a direction different from the applied load i.e., it should have high shear modulus and it should not undergo plastic deformation. Various approaches are adopted in the quest for super hard material and they can be broadly classified into three types: Specific covalent substances, including various crystalline and disordered carbon modifications; Covalent and ionic-covalent compounds and Partially covalent compounds of transition metals (TM) with light elements. The first two approaches have compounds made up of C or C with other low z elements like N, B and O and these are basically attempts at mimicking the sort of bonding that exists in diamond. The systems explored by these approaches are nano polycrystalline diamond, BN, CN etc. From the obtained results, it can be asserted that novel super hard material can be synthesized at a reasonably low pressure of 5 GPa. This paves way for bulk synthesis by multi-anvil apparatus which have huge industrial applications like cubic boron nitride, tungsten carbide and silicon carbide