We fabricated nanostructured Ge and GeSn films using He radio-frequency magnetron plasma sputtering deposition. Monodisperse amorphous Ge and GeSn nanoparticles of 30–40 nm size were arranged without aggregation by off-axis sputtering deposition in the high He-gas-pressure range of 0.1 Torr. The Ge film porosity was over 30%. We tested the charge/discharge cycle performance of Li-ion batteries with nanostructured Ge and GeSn anodes. The Ge anode with a dispersed arrangement of nanoparticles showed a Li-storage capacity of 565 mAh/g after the 60th cycle. The capacity retention was markedly improved by the addition of 3 at% Sn in Ge anode. The GeSn anode (3 at% Sn) achieved a higher capacity of 1128 mAh/g after 60 cycles with 92% capacity retention. Precise control of the nano-morphology and electrical characteristics by a single step procedure using low temperature plasma is effective for stable cycling of high-capacity Ge anodes.
We present a study on morphological control of nanostructured Ge films by the Ar gas pressure in plasma sputtering deposition. In the low Ar-gas-pressure range, aggregated islands of amorphous grains are formed on the film surface, while in the high-pressure range of 500 mTorr monodisperse nano-grains of about 30 nm in size are orderly arranged without aggregation. The film porosity shows a high value of over 10%. We tested the charge/discharge cycle performance of Li-ion batteries with nanostructured Ge films as anodes. The battery cell with an ordered arrangement structure maintained a high capacity of 434 mAh g−1 after 40 charge/discharge cycles, while that with an aggregated structure exhibited a rapid degradation of capacity to 5.08–183 mAh g−1. An ordered arrangement of Ge nano-grains with a high porosity, which is realized in a simple one-step procedure using high Ar-gas-pressure plasma sputtering, is effective for the stable cycling of high-capacity metal anodes.
In order to improve the rheological properties of the zirconia/polypropylene system for ceramic injection moulding, the zirconia powder was surface-treated with aluminate (A), silane (S) and titanate (T) coupling agents dissolved in toluene. 2% additions of these coupling agents decreased the torque, T h, for compounding the zirconia filled-polypropylene after 1 h at 180 ~ The surface treatment also reduced the viscosity, qa, of the compound, the effectiveness of the coupling agents on viscosity reduction being T > S > A. On the contrary, the apparent activation energy, E a, for flow of the compound increased when fluidity was promoted by surface treatment. Rheological measurements in systems with different titanate concentrations showed that the three parameters, T h, Tla, and E a, remained nearly constant for coupling agent additions of over 2%. This critical concentration of 2% showed good correspondence to the optimum concentration evaluated from thermogravimetric analysis of the powders.
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