Direct Measurement of Hydrogen Dislocation Pipe Diffusion in Deformed Polycrystalline Pd using Quasielastic Neutron Scattering

Published

July 10, 2014

Author(s)

Brent J. Heuser, Dallas R. Trinkle, Niina Jalarvo, Joseph Serio, Eugene Mamontov, Madhu Sudan Tyagi

Abstract

The temperature-dependent diffusivity D(T) of hydorgen solute atoms trapped at dislocations - dislocation pipe diffusion of hydorgen - in deformed polycrystalline PdH_x(x'0^-3[H]/[Pd] has been quantified with quasi-elastic neutron scattering (QENS) between 150 and 400 K. QENS provides a direct measurement of residence time and jump distance of the diffusing species. The large incoherent neutron scattering cross section of hydrogen allows QENS measurements at the low solute concentrations necessary to separate the migration of trapped soolute atoms from regular bulk diffusion. We observe diffusion coefficients for trapped hydrogen elevated by one to two orders of magnitude above vulk diffusion. Arrhenius diffusion behavior has been observed for dislocation pipe diffusion and regular bulk diffusion, the latter in well-annealed polycrystalline Pd. For regular bulk diffusion of hydrogen in Pd we find D(T)=D_oexp(-E_{z/kT)=0.006xp(-0.23 eV/kT) cm}u2^/s, in agreement with the known diffusivity of hydrogen in Pd. For hydrogen dislocation pipe diffusion we find D(T)≅10^-5 exp(-E_z/kT) cm²/s, where E_a=0.042 and 0.083 eV for concentrations of 520 and 1130x10^-6 [H]/[Pd}, respectively.

Citation

Physical Review Letters

Volume

113

Issue

2

Pub Type

Journals

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Keywords

quasi-elastic neutron scattering, hydrogen, diffusion

Citation

Heuser, B. , Trinkle, D. , Jalarvo, N. , Serio, J. , Mamontov, E. and Tyagi, M. (2014), Direct Measurement of Hydrogen Dislocation Pipe Diffusion in Deformed Polycrystalline Pd using Quasielastic Neutron Scattering, Physical Review Letters, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915867 (Accessed October 3, 2024)