Thermal conductivity of bulk electrodeposited nanocrystalline nickel

Room temperature thermoelectrical transport was investigated on a series of thick (300 gm), fully-dense electrodeposited nanocrystalline Ni materials with grain sizes below 50 nm. Strong grain size effects were observed on both electrical resistivity and thermal conductivity. As grain size decreased from 47 to 28 nm, the nanocrystalline Ni exhibited an increase in electrical resistivity from 9.42 to 10.2 mu Omega cm, and a reduction of thermal conductivity from 74.7 to 67.3 W/m-K, respectively. Analysis shows that for the nanocrystalline Ni, the change in the values of thermal conductivity and electrical resistivity is mainly due to grain boundary contributions with limited impurity effects. Furthermore, the thermoelectrical transport behavior agrees well with the Wiedemann-Franz law. The corresponding Lorenz numbers varied only in a narrow range from 2.30 x 10(-8) to 2.37 x 10(-8) W Omega/K-2 for the nanocrystalline Ni and were well within the experimentally measured value range of 2.12-2.44 x 10(-8) W Omega/K-2(2 for coarse grained Ni reported in the literature. (C) 2016 Elsevier Ltd. All rights reserved.