Scale Effect of Microparticles Constituting Powder on the Thermal Diffusion

Abstract Nanometer-sized particles possess characteristic physical and chemical properties different from those of bulk materials due to an increase in surface-to-volume ratios as well as of confinement of electrons, excitons, and photons into small volumes. Therefore it is worthwhile to discuss the thermal behaviours of powders constituted by nanometer-sized particles. The heat transfer in the powder composed of nanoparticles is experimentally investigated in this paper. The understanding for thermal properties of the powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. The powder is wrapped up in the slender tube. One end of the slender tube filled with powder is maintained at temperature 0°C and the other end is kept at room temperature. The temperature histories at different locations in the slender tube are recorded using thermal couples. Particles with the sizes 18 nm, 500 nm, and 5000 nm are employed in this experiment. The results show that the thermal diffusion in the powder increases with the decreasing size of particles constituting the powders. The scale effect of particles in the Al powders on the thermal diffusion is discussed in this paper