Oberflächenanalytische Untersuchungen zur Wechselwirkung des Getters ZrCo mit Wasserstoff und zum Einfluss verschiedener Kontaminationsgase auf die Wasserstoffspeicherfähigkeit

Content Provider	Semantic Scholar
Author	Glasbrenner, Heike
Copyright Year	1991
Abstract	Surface Analytical Investigations of the Interaction Between the Getter Material ZrCo and Hydrogen and the Influence of Different Cantamination Gases on the Hydrogen Storage Capacity In this work the results of surface analytical investigations of the alloy ZrCo used for hydrogen storage as well as of the interaction of the alloy with hydrogen and various contamination gases present in a nuclear fusion reactor will be presented and discussed with respect to the ~pplication of ZrCo as gettermaterial for tritium. The characterization of the ZrCo alloy showed that on the surface a stable ZrOz-layer is formed, which is, however, inhomogeneous. In the surface near part of the about 10 nm thick ZrOz layer one observes nearly stoichiometric zirconiumdioxide, at the interface between ZrCo alloy and the oxide layer Co is enriched. Obviously Zr is depleted via diffusion through the oxide layer. When compared to clean Zr, the alloy has less affinity to oxygen. At a depth of about 130 nm one finds the bulk composition. On the phase boundary solid I gas of samples exposed to hydrogen up to the stoichiometrical composition ZrCoHz.s a Co enrichment was observed. In different publications many examples of Zr-poor alloys are given, where the component in excess is enriched on the surface during exposition to hydrogen. The effect becomes more pronounced with increasing concentration of hydrogen in the sample. If the alloy ZrCo is activated before hydrogen take-up in the same way as other getter materials by heating under vacuum, the hydrogenation occurs faster and nearly complete. In this case, however, no reduction of the oxide layer on the surface to the metal was noticed, which is assumed to be the reason for the activation of most of the other getter materials and also of the pure elements Zr and Co. It seems possible, that the activation process changes ZrOz on the surface of the alloy to another modification, which has a higher hydrogen permeability. The investigation of hydrided samples revealed an additional Zr 3d photopeak clearly separated from the metallic component, which could be assigned to the Zr-H interaction by means of multiplet analysis. In cantrast no interaction with hydrogen was observed in the Co 2p spectra. But it could be shown by SIMSand SNMS measurements that Co and H are emitted as a cluster and must have been, therefore, closely neighbouring in the solid. From the analysis of Zrand Co compounds built after exposition of ZrCo to different contaminant gases, conclusions could be drawn for the change of the hydrogen storage capacity of the material in dependence on the gaseaus species. It was noticed that at least at higher temperatures a remarkable decrease of the storage capacity occurs for specific contaminant gases. Zirconium is the alloy component responsible for the hydrogen storage. If a gas reacts nearly exclusively with the alloy component Co, a smaller decrease in the hydrogen storage capacitywill be noticed. By exposition to CO and COz mainly compounds with cobalt are formed. However, if the gas produces compounds with Zr like carbide, nitride, or oxide, the result is a strong decrease of the hydrogen storage capacity of the getter. The reason is assumed to be either the formation of a closed, diffusion inhibiting overlayer or the decrease of the number of free Zr atoms required for the hydride formation. Among the gases, which react strongly with Zr, are CH4, CzH4, Oz and Nz.
Starting Page	1
Ending Page	115
Page Count	115
File Format	PDF HTM / HTML
Alternate Webpage(s)	https://publikationen.bibliothek.kit.edu/33691/7706253
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article