Abstract
A first-principles study was performed to assess the potential of MAB2 (M = Nb, Ta; A = Co, Ni) ternary borides as friction-resistance cermet. The formation energy, decomposition energy, phonon dispersion curves and elastic constants were calculated to evaluate stabilities. The bulk modulus, shear modulus, Pugh's ratio, Poisson's ratio and elastic anisotropy were adopted to analyze elastic properties. The Debye temperature was used to reflect thermal conductivity. The density of states, charge density and Mulliken population were performed to reveal physical mechanisms. Through calculational results, MAB2 possesses structure and mechanical stabilities, and then MAB2 has excellent elastic properties. Both NbNiB2 and TaCoB2 are ductile materials; in addition, the thermal conductivity of NbNiB2 and NbCoB2 are satisfying. The calculations imply MAB2 is a mixture of covalent, ionic and metallic bonds, indicating covalent bonds are vital. Especially, the theory hardness of NbCoB2, NbNiB2, TaCoB2 and TaNiB2 are 25.30, 27.71, 30.78 and 31.91 respectively, indicating MAB2 has high-hardness potential. The comprehensive properties are more outstanding in MAB2 than in MAB. The method from atomic scale to macroscale can accelerate optimization of novel friction-resistance cermet.
Published Version
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