Thermal Conductivity of Nanocrystalline Nickel

The grain-size dependences of thermal conductivity and electrical resistivity of polycrystalline and nanocrystalline nickel were measured by the flash method and four-point probe method, respectively. Nanocrystalline nickel was made by the pulsed-current electrodeposition process, while polycrystalline nickel was commercially available Ni 200 in annealed condition. The grain sizes of the materials examined ranged from 28 nanometers to 57 micrometers. Noticeable changes in thermal conductivity and electrical resistivity with grain size were observed in particular for samples with grain sizes less than 100 nm. These results can be explained on the basis of the rapid increase in the intercrystalline grain boundary and triple junction volume fractions at very small grain sizes. The relationship between thermal conductivity and electrical resistivity of nanocrystalline nickel follows the classic Wiedemann-Franz law.MAS