Tribochemistry involves chemical reactions occurring at sliding contact interfaces in the presence of gaseous and/or liquid media. It often leads to the formation of a solid reaction film (also termed boundary film) which controls friction and wear and hence the efficiency and reliability of moving mechanical systems (such as engines). Here we demonstrate tribochemical conversion of methane to graphene, nano-onion, and disordered carbons on the sliding surfaces of Ni-, Cu-, and CuNi-containing VN coatings at atmospheric pressure and room temperature, providing 2–3 orders of magnitude reduction in wear and ∼50% reduction in friction compared to those of the uncoated steels. Transmission electron microscopy confirms that graphene forms preferably on metal rich nanoclusters of the composite coatings, while the carbon nano-onions are scattered throughout the carbon tribofilm. Ab initio molecular dynamics simulations elucidate underlying mechanisms involved in the tribochemical conversion of methane to carbon-based nanostructures in support of microscopic observations. These scientific findings may lead to new materials technologies that can use methane as a source for continuous and in situ lubrication. For example, there is an urgent need to curtail the uses of lubricating oils in natural gas compressors and engines as they contaminate the natural gas being compressed or burnt.

The reversible cyclability of Si based composite anodes is greatly improved by optimizing the atomic ratio of Cu/Si in the films fabricated via magnetron sputtering. The galvanostatic test results show that the thin film anode made of 20%at. Cu delivers 1950 mAhg-1 as the initial discharge capacity with 80% Coulombic efficiency. Then, after the 50th cycles 80% of the initial discharge capacity is retained, with 99.5 % Coulombic efficiency. This remarkable performance can be explained by small crystalline sizes, amorphous structures of the thin film and its enhanced physical and mechanical properties due to the 20 %at. Cu content. High specific capacities achieved in this study prove that magnetron sputtering deposition might be a good alternative production technique to fabricate high performance anode materials. Furthermore, this one step, environmentally friendly process enables one to control the film composition, structure as well as adhesion which minimizes delamination and pulverization.

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In the present work we deposit Si film with 20%at. Ag, to improve the capacity retention and the cycleability of Si anode. The physical properties of the as-synthesized sample are investigated by thin film XRD and SEM. Charge-discharge properties, cyclic voltammetry, electrochemical impedance spectroscopy and cycle performance of the AgSi electrode are examined in detail when used as negative electrode versus lithium. The galvanostatic test result shows that the electrode delivers 1825 mAh g-1 initially with 95% Coulombic efficiency and retains 96% of its initial discharge capacity after 40 cycles. This outstanding coulombic efficiency of the electrode can be related to the presence of Ag, which decreases the polarization of anode.