Hydrogen Diffusivity and Solubility in Internally Oxidized Pd0.97Zr0.03 and Pd0.97Nb0.03 Alloys
Internally oxidized (I.O.) Pd0.97Zr0.03 and Pd0.97Nb0.03 alloys were submitted to gas permeation tests with temperatures in the range of 473-873 K. The internal oxidation was kept in a conventional furnace at 1073 K for 24 hours in air contact. The formation of nano-oxides, ZrO2 and Nb2O5, dispersed in the Pd matrix was observed. SEM images showed a preferential segregation of these oxides in the grain boundaries. It was observed that the diffusion coefficient in the sample containing Nb oxide was smaller than that in the Pd-Zr oxide. The effect of hydrogen pressure was investigated in the Pd-Nb samples. It was observed that the hydrogen diffusion coefficient increases with increasing the pressure. The hydrogen solubility is bigger for the Pd-Zr internally oxidized. This effect is attributed to the Zr nanoxides, which are smaller than Pd-Nb precipitates and then offer more interface for trapping the hydrogen.
Andreas Öchsner, Graeme E. Murch, Ali Shokuhfar and João M.P.Q. Delgado
E.R. Lagreca et al., "Hydrogen Diffusivity and Solubility in Internally Oxidized Pd0.97Zr0.03 and Pd0.97Nb0.03 Alloys", Defect and Diffusion Forum, Vols. 297-301, pp. 715-721, 2010