Plating on engineering plastics is necessary as an alternative to metallic materials for weight reduction and design improvement. However, harmful chemical substances are involved in plastic plating processes. For this study, we specifically assessed polybutylene terephthalate（PBT）as a metal substitute material and examined low-vacuum Cu sputtering. Along with fatigue resistance, heat resistance, and electrical characteristics, PBT has particularly good water absorption resistance and therefore excellent dimensional stability. Because of these characteristics, PBT has attracted attention as a metal substitute material. Low-vacuum Cu sputter is excellent for metal deposition on a three-dimensional object because particles from the target are scattered in a low vacuum. For this study, we examined improvement of the adhesion of Cu sputter to PBT by applying oxygen plasma treatment as a sputter pretreatment.

The stability of polymer electrolyte fuel cells（PEFCs）during power generation is one of the most important issues, especially at high current densities. A new oscillation phenomenon was observed in a PEFC with 10-straight channels operated at the temperature of 60 ℃ and the relative humidity of 60% using a gas diffusion layer（GDL）without a micro porous layer at the cathode. The cell voltage oscillated periodically under a constant-current operation. The period and amplitude were approximately 2 s and 20 mV, respectively, but changed at different gas flow rates and current densities. An operando system was developed for detecting the oxygen partial pressure（p（O₂））using optical probes. p（O₂）during the oscillation synchronized with the cell voltage. During the oscillation, the generated water was proposed to increase and accumulate in the catalyst layer（CL）, accordingly lowering the transport and thus reduction reaction of oxygen. The larger overvoltage resulted in the heat in the CL, by which the liquid water having accumulated in the CL was removed as water vapor to the GDL. This oscillation could be more pronounced at higher current density.