First-principles study of thermal conductivity of welded interface elements based on Mo interlayer SPS

An Mo interlayer can effectively enhance the thermal conductivity of diamond-copper composite SPS diffusion welding interface. But the detailed microscopic mechanism underlying this enhancement remains unexplored. This study establishes potential interface models based on the elemental composition at the SPS diffusion welding interface and investigates the impact of the Mo interlayer on thermal conductivity. The analysis, grounded in first-principles calculations, examines interfacial spacing, work of adhesion, electronic state density, and phonon state density. Findings indicate that the formation of Mo2C at the interface improves bonding, ameliorates the mismatch in phonon vibration frequencies between diamond and Cu, and thereby increases the interface's thermal conductivity. At the weld interface, the 2s and 2p orbitals of C in Mo2 C exhibit new hybridization peaks distinct from those of C in diamond, while the 4p orbitals of Mo resonate with these new peaks. This results in strong bonding cooperation between Mo and the carbon in diamond, enhancing interfacial bonding strength. This enhanced bonding provides theoretical guidance for achieving high thermal conductivity in SPS diffusion welded interfaces.