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Vanadium-doped magnesium nanostructures are fabricated by an oblique angle co-deposition method and hydrogenated/dehydrogenated for 21 cycles. The effective thermal conductivity and density of the MgH2 nanostructures is measured by using a photothermal system. A multilayer physical model is used to fit the experimental data. Our results show that the effective thermal conductivity of the hydrogenated V-doped Mg nanostructures is in the range of 1.16-2.40 W m(-1) K(-1) and the density falls in the range of 878-1320 kg m(-3). The measured density agrees well with the estimation from electron micrograph observation. Variation in the measurements indicates strong nonuniformity of the sample structure and thickness. Based on the measured density and effective thermal conductivity, the thermal conductivity of bulk V-doped Mg hydrides is also evaluated using Maxwell's correlation.

A unique diffusion barrier structure, consisting of layers of a Ti nanorod array and Ti film, has been fabricated on Si substrate for a subsequent 2 at.% Ti-doped Mg film deposition using a combinational technique of multilayer growth, co-deposition and dynamic shadowing growth. The hydrogenation of the Ti-doped Mg film on such a barrier structure shows that the barrier can prevent direct Mg-Si contact and suppress the formation of Mg(2)Si alloy in a high-temperature process. When this film has been hydrogenated at temperatures T≤300 °C for approximately 150 h, tetragonal single-crystal MgH(2) nanowires are formed on the surface of the Ti-doped Mg film. The hydrogenation time and temperature are the two main factors for the nanowire formation. The doping of Ti also plays a significant role. This result reveals that complicated dynamic processes could occur during the hydrogenation of Ti-doped Mg film when Mg(2)Si formation can be eliminated by an effective diffusion barrier layer.