Thermal conductivity prediction of a Cu circular nanowire

• A calculation model was set up to predict the thermal conductivity of a metallic circular nanowire.
• Grain-boundary scattering has a greater effect than that of surface scattering on the ETC of a metallic CNW.
• Reducing grains is a practical way to improve both of the ETC and the PTC of a Cu CNW.
• The ETC and the electrical conductivity of a Cu CNW are higher than those of a RNW.

A theoretical calculation mean-free-path (MFP) model was built for circular nanowires for the first time, taking both the surface scattering and the grain boundary scattering into account. The developed MFP model can be integrated into the kinetic theory to predict the axial electronic and lattice thermal conductivities in nanowires. Based on the model, a discussion was made of the size effects produced by both the surface scatterings and the grain boundary scatterings of the electrons. The size dependences of the phonon-produced specific heat and the phonon group velocity were also modeled and discussed. The model developed in this work gave a good prediction of the thermal conductivity. Generally, the grain boundary is more significant than the circular nanowire surface in influencing the electronic thermal conductivity. Enlarging the grain size can improve both the electronic/lattice thermal conductivity and the electrical conductivity of a Cu circular nanowire. The electronic thermal conductivity and electrical conductivity of a circular Cu nanowire were both higher than those of a rectangular one.