Absorption of N atom in Pd wire at low temperature and the influence on its physical properties

High temperature in situ resistivity measurement was carried out to monitor the resistivity change of the Pd win when annealed in the temperature range of 250-400 degrees C in flowing N-2. In the range of 250-350 degrees C, the resistivity change with time can be fitted well by a bulk-diffusion model with infinite-long cylinder geometry, the derived apparent diffusion coefficient versus temperature matches the Arrhenius plot well, and the apparent activation energy for this process was derived to be 1.3 eV. The tensile test showed that the mechanical properties of the Pd wire annealed at 300 degrees C in flowing Nz is better than those in air. The results disagree with the traditionally accepted conclusion. nitrogen is insoluble in the Pd below 1400 degrees C (Hansen (1958) Constitution of Binary Alloys, McGraw-Hill, New York). Besides, the influence of superficial oxidation on the absorption and desorption behaviors of N atoms in Pd wire at different annealing temperatures (up to 400 degrees C) was discussed in terms of the reversibility of resistivity change when the ambient atmosphere was changed between pure N-2 and air. (C) 2000 Elsevier Science S.A. All rights reserved.