In this study, we evaluated the microstructure, microhardness, tribological properties, and oxidation behaviors of Zr_1－XAl_XN films, considering the requirements for their use as wear-resistant coatings. Zr_1－XAl_XN films were synthesized by radio-frequency magnetron sputtering from （ZrN）_1－X-Al_X targets. X-ray diffraction analysis indicated that the Zr_1－XAl_XN film had a cubic phase when X＝0.12, being transformed into a mixture of cubic and hexagonal phases when X＝0.26. Zr_0.88Al_0.12N displayed an average frictional coefficient of 0.3-0.5 and a minimum wear depth of 0.4 μm. The microhardness of Zr_1－XAl_XN decreased from 36.5 GPa for X＝0.12 to 16.9 GPa for X＝0.43. During dynamic oxidation, the exothermic peak in a differential thermal analysis curve shifted from 730 ℃ for X＝0.12 to 835 ℃ for X＝0.43. In accord with this behavior, the mass gain measured by thermogravimetric analysis for Zr_0.57Al_0.43N exhibited minimum values at isothermal oxidation temperatures in the range of 600-700 ℃.

To estimate brightener concentrations in nickel plating liquids, we applied electrochemical measurements and numerical analyses. The polarization curves of fresh nickel plating liquids at different concentrations were measured using a conventional three-electrode configuration. Several characteristic values were selected on the polarization curves. Relations between the characteristic values and the brightener concentrations were analyzed. The polarization curve shape correlated with the concentrations of saccharin sodium salt dihydrate and 2-butyne-1,4-diol, which are commonly used brighteners for nickel plating liquids. These correlations were changed to functions when the brightener concentrations were markedly lower than the commonly used values. The brightener concentrations estimated according to the functions were compared with the prepared brightener concentrations. The estimated values showed good linearity. We concluded that this method is applicable for estimating brightener concentrations in nickel plating liquids.