[en] A novel Co–WC composite coating was fabricated on the surface of high-speed steel (HSS) substrate by direct current (DC) electrodeposition. The co-electrodeposition mechanism of Co–WC composite coating was explored. Furthermore, the effects of process parameters on the microstructure and micro-hardness of the coating were studied. The microstructure and composition of Co–WC composite coating were investigated by scanning electron microscopy equipped with an energy dispersive x-ray spectroscope. The adhesion strength of Co–WC composite coating was evaluated by WS-2005 automatic scratch tester. Results revealed that WC particles were homogeneously embedded in the Co matrix with few defects, and the Co–WC composite coating was firmly bonded to the HSS substrate. The optimized parameters are as follows: WC concentration of 35 g l⁻¹, current density of 6.5 Adm⁻², stirring rate of 300 rpm, and pH of 7.5 and temperature of 50 °C. X-ray diffraction analysis indicated that the Co matrix combined physically with the WC particles. Also, the microindentation hardness of Co–WC composite coating was tested by micro-hardness tester. It was found that the microindentation hardness of Co–WC composite coating reached the maximum value of 542 HV under the optimal process conditions. (paper)

[en] Ni-Co alloy and SiC micro-particles were co-deposited on 45 steel by electrodeposition for high temperature performance. The high temperature tribological characteristics were studied by use of a ball-on-disk method. The micrographs and phase structure of the Ni-Co-SiC composite coatings after high-temperature friction were observed by using a field emission scanning electron microscope(FESEM). The results reveal that the Ni-Co-SiC composite coating presents better wear resistance and lower friction coefficient at high temperature in comparison with that of Ni-Co coating and 45 steel substrate. The embedded SiC particles could strengthen the alloy coating by dispersion strengthening effect and changing the friction mechanism from adhesive wear to abrasive wear. (paper)

[en] The effects of Fe–C/N co-doping on the electronic and optical properties of NaTaO${}_3$ are studied with density functional theory. Our calculations indicate that mono-doped and co-doped sodium tantalate are both thermodynamically stable. The co-doping sodium tantalate can reduce the energy band gap to a greater degree due to the synergistic effects of Fe and C(N) atoms than mono-doping sodium tantalate, and has a larger optical absorption of the whole visible spectrum. The band alignments for the doped NaTaO${}_3$ are well positioned for the feasibility of hydrogen production by water splitting. The Fe–C co-doping can enhance the absorption of the visible light and its photocatalytic activity more than Fe–N co-doping due to the different locations of impurity energy levels originating from their p–d hybridization effect. (paper)