Effects of internal oxidation on the hydrogen permeation in Pd0.97Al0.03 and (Pd0.9Pt0.1)0.97Al0.03 alloys

• Published in: Journal of alloys and compounds 2002-11, Vol.346 (1-2), p.142-146
• Main Authors: Azambuja, V.M, dos Santos, D.S, Pontonnier, L, Miraglia, S, Fruchart, D
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Gas–solid reaction; Hydrogen diffusivity; Metal hydrides; Microstructure; Other topics in nonelectronic transport properties of condensed matter; Other topics in nonelectronictransport properties of condensed matter; Physics; Solubility, segregation, and mixing; phase separation; Transport properties of condensed matter (nonelectronic); X-ray diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(02)00483-8

Samples of the Pd0.97Al0.03 and (Pd0.9Pt0.1)0.97Al0.03 alloys, internally oxidized at 1073 K for 72 h, were submitted to three sorption–desorption cycle at 313 K by an electrochemical hydrogen permeation technique. The effects of internal oxidation were investigated by X-ray diffraction (XRD) and transmission electronic microscopy (TEM). We observed by XRD the formation of PdO2 only in the case of the Pd0.97Al0.03 alloy, while for the (Pd0.9Pt0.1)0.97Al0.03 alloy, there was no indication of internal oxidation of the alloying elements after annealing at 1073 K for 72 h. TEM analysis in the heat treated Pd0.97Al0.03 alloy showed dispersed nanoprecipitates of Al2O3, markedly in coherent interface with the Pd matrix. However, in the heat treated (Pd0.9Pt0.1)0.97Al0.03 alloy, areas rich in Pt and Al were observed only, suggesting the formation of PtAl clusters. In the Pd0.97Al0.03 alloy due to the presence of Al2O3 and PdO2 the hydrogen diffusivity (Dapp=2.3×10−12 m2 s−1) is very low in comparison to that of the (Pd0.9Pt0.1)0.97Al0.03 alloy (Dapp=1.0×10−11 m2 s−1) and a heat treated pure Pd sample (Dapp=5.5×10−11 m2 s−1). The hydrogen solubility in the heat treated Pd0.97Al0.03 is quite high (1075 molH m−3) due to the appearance of new interfaces to trap hydrogen. The low value of hydrogen solubility presented by (Pd0.9Pt0.1)0.97Al0.03 (136 molH m−3) is attributed to the non oxidation of the constituting elements.