A stacked high-voltage (900 V) Al electrolytic capacitor made with ZrO2 coated anode foils, which has not been studied so far, is realized and the effects of Zr-Al-O composite layer on the electric properties are discussed. Etched Al foils coated with ZrO2 sol are anodized in 2-methyl-1,3-propanediol (MPD)-boric acid electrolyte. The anodized Al foils are assembled with stacked structure to prepare the capacitor. The capacitance and dissipation factor of the capacitor with ZrO2 coated anode foils increase by 41 % and decrease by 50 %, respectively, in comparison with those of Al anode foils. Zr-Al- O composite dielectric layer is formed between separate crystalline ZrO2 with high dielectric constant and amorphous Al2O3 with high ionic resistivity. This work suggests that the formation of a composite layer by coating valve metal oxide on etched Al foil surface

Oxide-dispersion-strengthened (ODS) alloy has been developed to increase the mechanical strength of metallic materials; such an improvement can be realized by distributing fine oxide particles within the material matrix. In this study, the ODS layer was formed in the surface region of Zr-based alloy tubes by laser beam treatment. Two kinds of Zr-based alloys with different alloying elements and microstructures were used: KNF-M (recrystallized) and HANA-6 (partial recrystallized). To form the ODS layer, Y2O3-coated tubes were scanned by a laser beam, which induced penetration of Y2O3 particles into the substrates. The thickness of the ODS layer varied from 20 to 55 μm depending on the laser beam conditions. A heat affected zone developed below the ODS layer; its thickness was larger in the KNF-M alloy than in the HANA-6 alloy. The ring tensile strengths of the KNF-M and HANA-6 alloy samples increased more than two times and 20–50%, respectively. This procedure was effective to increase the strength while maintaining the ductility in the case of the HANA-6 alloy samples; however, an abrupt brittle facture was observed in the KNF-M alloy samples. It is considered that the initial microstructure of the materials affects the formation of ODS and the mechanical behavior.

Oxide effects experiments on massive hydriding reactions of Zr alloy with hydrogen gas were carried out at 400˚C under 1 atm in a H2 environment with a thermo-gravimetric apparatus (TGA). Experimental results for oxide effects on massive hydriding kinetics show that incubation time is not proportional to oxide thickness. The results also show that the massive hydriding kinetics of pre-filmed Zr alloys follows linear kinetic law and that the hydriding rates are similar to that of oxide-free Zr alloys once massive hydriding is initiated. Unlikely microstructure of the oxide during incubation time, physical defects such as micro-cracks and pores were observed in the oxide after incubation time. Therefore, it seems that the massive hydriding of Zr alloys can be ascribed to short circuit paths and mechanical or physical defects, such as micro-cracks and pores in the oxide, rather than to hydrogen diffusion through the oxide resulting from the increase of oxygen vacancies in the hypo-stoichiometric oxide.