Abstract
The electrical resistivity of Pd-Ag (silver 21 wt.%) in hydrogen and deuterium atmosphere at 100 kPa has been investigated via electrochemical impedance spectroscopy. The electrical resistivity of Pd-Ag vs. the temperature presents the characteristic S-shaped curve with a minimum and a maximum of the resistivity in different positions for the tests in hydrogen and deuterium. The results have been related to: (1) the different isotope ratios, H/M and D/M, and (2) their position in the Pd-Ag lattice. The behavior of the electrical resistivity is discussed in details by considering the hydrogen and deuterium uploading into the alloy, its effect on the conduction electrons, and the scattering of the isotopes atoms into the metal lattice. Measurements carried out in hydrogen with slow temperature ramping between 25–250 °C evidenced a hysteresis effect that can be explained by the different energy levels of isotopes in O-sites and T-sites
Highlights
Palladium-based membranes are studied for technological processes such as the separation and purification of hydrogen [1,2]
Equation (12) is valid for non-hydrogenated material; in particular in argon, the resistivity relation vs. temperature for Pd-Ag 21 wt.% was almost linear in the range 25–450 ◦ C, and the α value was about 4.4 × 10−4 ◦ C−1
The experimental work was aimed at measuring the resistivity of Pd-Ag in hydrogen and deuterium at a pressure of 100 kPa and in a temperature range of 25–450 ◦ C
Summary
Palladium-based membranes are studied for technological processes such as the separation and purification of hydrogen [1,2]. Potential applications concern the fusion fuel cycle where hydrogen isotopes have to be separated from plasma exhausts, from breeding blankets, and from coolants (water, helium) [3]. Several methods are proposed for recovering tritium from water [4,5,6,7,8,9] and, in particular, the use of membrane processes introduces the advantages of high reliability and continuous operations, ensuring the more efficient and safe management of a fusion power plant [10]. The uploading of hydrogen into pure Pd can involve metal embrittlement. Ag alloying improves the mechanical properties and hydrogen permeability [13]; both the tensile strength and the permeability show a maximum for silver content in the range 20%–40% of weight that is the Ag content of commercial
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