Neil R. Aukland

Alloys that form conductive and passivating oxides for proton exchange membrane fuel cell bipolar plates

During the operation of proton exchange membrane (PEM) fuel cells, a high-resistance oxide is often formed on the cathode surface of base metal bipolar plates. Over time, this corrosion mechanism leads to a drop in fuel cell efficiency and potentially to complete failure. To address this problem, we have developed alloys capable of forming oxides that are both conductive and chemically stable under PEM fuel cell operating conditions. Five alloys of titanium with tantalum or niobium were investigated. The oxides were formed on the alloys by cyclic voltammetry in solutions mimicking the cathode- and anode-side environment of a PEM fuel cell. The oxides of all tested alloys had lower surface resistance than the oxide of pure titanium. We also investigated the chemical durability of Ti-Nb and Ti-Ta alloys in more concentrated solutions beyond those typically found in PEM fuel cells. The oxide films formed on Ti-Nb and Ti-Ta alloys remained conductive and chemically stable in these concentrated solutions. The stability of the oxide films was evaluated; Ti alloys having 3% Ta and Nb were identified as potential candidates for bipolar plate materials.

Frictional work as a sliding wear evaluation parameter [electrical contacts]

The purpose of this research paper is to demonstrate that frictional work can be used as a new and previously unused parameter in the analysis of sliding wear data. Three different applications of frictional work as a sliding wear data evaluation parameter are presented in this paper. The first application shows that frictional work is a powerful approach in the evaluation of contact lubricants. Another application demonstrates that frictional work can be used as a measurement system evaluation parameter for sliding wear machines. Finally, upper and lower limits are calculated for a control chart based on frictional work values to insure the correct operation of a sliding wear machine. These applications were successfully used and established the frictional work parameter as a useful tool in the analysis of sliding wear data.