An XAFS Study on the Surface Structure After an Anomalous Heat Generation Experiment Using a Material System of Ni/Cu Multilayer on Ni Substrate

The anomalously large heat generation phenomenon using hydrogen gas and nanoscale Ni/Cu multilayer films on Ni sheets was investigated by SEM-EDX and XAFS analyses for a sample that showed significant excess heat generation during a long-term heat generation experiment. SEM observations of the sample in back scattered electron mode revealed andomly distributed dark regions of anomalously high oxygen concentration, surrounded by grey regions with only trace oxygen concentration. The dark regions corresponded to the regions of high oxygen concentration (RHOC) reported in previous studies. XAFS analyses of the sample suggested that approximately 5% of the Ni or Cu atoms in the surface layer were in a chemical state similar to oxygen-deficient NiO1 or CuO1 , and were localized in the RHOC. It was also suggested that the RHOC extended to a depth of⇠0.8 µm or more which was much deeper than the initial multilayer thickness of⇠150 nm. If the RHOC were formed as a result of cumulative events of anomalous heat generation, then a local atomic configuration, in which a significant number of both oxygen atoms and their vacancies occupy octahedral interstitial sites adjacent to Ni atoms with a face-centered cubic structure, may be an efficient nuclear active environment for anomalous heat generation.