Co-Mo Films Research Articles

In Situ Formation of Efficient Cobalt-Based Water Oxidation Catalysts from Co(2+)-Containing Tungstate and Molybdate Solutions.

Replacing rare and expensive noble-metal catalysts with inexpensive and earth-abundant ones is of great importance to split water either electrochemically or photoelectrochemically. In this study, two amorphous cobalt oxide catalysts (Co-W film and Co-Mo film) with high activity for electrocatalytic water oxidation were prepared by fast, simple electrodeposition from aqueous solutions of Na2WO4 and Na2MoO4 containing Co(2+). In solutions of Na2WO4 and Na2MoO4, sustained anodic current densities up to 1.45 and 0.95 mA cm(-2) were obtained for Co-W film at 1.87 V versus a reversible hydrogen electrode (RHE) and Co-Mo film on fluorine-doped tin oxide (FTO) substrates at 1.85 V versus RHE. For the Co-W film, a much higher current density of 4.5 mA cm(-2) was acquired by using a stainless-steel mesh as the electrode substrate. Significantly, in long-term electrolysis for 13 h, the Co-W film exhibited improved stability in cobalt-free buffer solution in comparison with the previously reported Co-Pi film.

Ｃｏ−Ｍｏ，Ｃｏ−Ｗ膜の磁気異方性と二相分離

Seeking new materials for high-density magnetic recording media, we investigated the magnetic anisotropy and phase separation of Co-Mo and Co-W binary alloy thin films. Both alloys exhibit much larger magnetic anisotropy than does Co-Cr. Thermodynamic calculations on phase equilibria of Co-X (X = Cr, Mo, W) binary systems predict that magnetically induced two-phase separation can occur in these binary alloys as has been experimentally observed in Co-Cr. In fact, their saturation magnetization and Curie temperature are obviously enhanced by annealing or depositing them at high temperatures, suggesting the promotion of two- (ferro/para) phase separation. Microscopic compositional modulation due to the phase separation was confirmed in a Co-Mo film by micro EDX analysis. However, the amplitude of the compositional modulation is much weaker than the thermodynamic calculations, indicating that the miscibility gap is considerably narrowed probably due to large misfit energy at the ferro/para interface or due to very limited diffusion constants of Mo and W.

Magnetic properties of crystalline and amorphous Co-Zr, Nb, Mo thin film alloys

This paper reports the results of measurements of some magnetic properties of Co-Zr, Co-Nb and Co-Mo thin film alloys prepared at cobalt concentrations between 100 and 65 at.%. The films were produced by sputter deposition in a DC triode system. The alloys are found to be amorphous above critical concentrations of the non-magnetic transition metal. The room temperature saturation magnetisation decreases monotonically from a value near to that of bulk cobalt to zero at a cobalt concentration of about 70 at.%. Films of the first two alloy series are characterised by in-plane magnetisation in both the crystalline and amorphous phases, whereas crystalline Co-Mo films can exhibit perpendicular magnetisation as observed in Co-Cr alloy films.

The domain structure and magnetic properties of Co-Cr, Mo films

The magnetic properties of Co-Cr and Co-Mo films prepared by d.c. triode sputtering are discussed. The films are found to have perpendicular magnetisation in certain composition ranges. The magnetic domain structure of the films as observed by Lorentz electron microscopy is interpreted in terms of the deposition parameters and the properties of the films. In particular the microstructure of the films is seen to have an overwhelming influence on the domain structure.