In order to obtain the diffusion coefficient of hydrogen in iron free from trapping by dislocations and impurities, electrochemical permeation measurements have been done using high purity iron (99.99 mass% Fe), pure iron (99.99 mass% Fe, high substitutional and low interstitial impurity contents), pure iron (99.94 mass% Fe), and commercially pure iron (99.83 mass% Fe) between 278 and 318 K.
Drift, diffusion, and trapping of hydrogen in p-type GaN Nov 27, 2002 · Using capacitancevoltage measurements we have measured both the diffusion and the field-induced drift of H in GaN p/n + diodes grown by metalorganic vapor phase epitaxy. Our data are well described by a computational model which simulates all of the important electronic processes as well as the drift, diffusion, and trapping of hydrogen in the GaN lattice.
The primary features of these models are stress-assisted diffusion and an elasto-plastic constitutive law (J2 plasticity) for material response; additional constitutive assumptions need to be made to capture hydrogen-induced dilatation, trap generation with plastic strain, and changes in local elastic moduli with hydrogen concentration.
HYDROGEN DIFFUSION AND TRAPPING IN hydrogen trap sites in the material. The effective diffusion coefficient measured with fully annealed specimens was in agreement with previously-reported values of the lattice diffusion coefficient (7.8 x 10-14 m2/s at 30 *C). This suggests that trapping has a negligible effect on diffusion in this material.
Hydrogen Diffusion through Palladium Alloys Johnson Diffusion through palladiumsilver membranes is now a well established commercial route for the production of ultra high purity hydrogen. Continuing attempts to find better membrane materials have shown that palladium alloyed withthe rare earth elements cerium or yttrium has certain appreciable advantages, although poisoning of the membrane surfacecan make evaluation of the materials
The effective diffusivity of hydrogen in as-annealed (550°C for 5 h) 99.999% purity polycrystalline aluminum was determined using Al/Pd bilayer membranes following the procedure of K.R. Hebert. Bulk diffusion control was verified by the foil thickness variation method.
Hydrogen Purification Methods - Technology The Hydrogen that is produced using PEM technology then flows through a stainless steel desiccant cartridge for moisture removal. The desiccant column is most commonly made up of silica gel beads which act as a drying agent in hydrogen to produce high purity hydrogen, meeting industry purity requirements. PEM / Silica Desiccant Process
Hydrogen Solubility, Diffusion and Trapping in High Purity Hydrogen Solubility, Diffusion and Trapping in High Purity Aluminum and Selected Al-Base Alloys p.1583 Intergranular Hydrogen Trapping in Al-Mg:A Monte Carlo Simulation
Jun 12, 2017 · In this paper, the effect of local hydrogen concentration and distribution in magnesium (Mg) alloys is studied in regard to hydrogen embrittlement. Quantitative studies of hydrogen trapping sites and release behavior in AZ91 and AZ31 magnesium alloys are being studied by thermal desorption analysis (TDS). The trapping energy levels are used to discuss the embrittlement mechanisms due to
Hydrogen trapping in some advanced high strength steelsPermeability experiments were used to study hydrogen diffusion and trapping in dual phase (DP), quenched and partitioned (Q&P), advanced high strength steels. The measured reversible hydrogen trap densities indicated that (i) trapping was less significant at a more negative potential, and (ii) the lattice diffusion coefficient of hydrogen could be measured from the partial transients at the
Hydrogen trapping models in steel SpringerLinkThis article describes the role of hydrogen trapping in steel. Trapping increases the solubility of hydrogen and decreases the diffusivity. Traps are characterized by their nature, i.e., reversible or irreversible, saturable or unsaturable. A dislocation core is a saturable, reversible trap, while voids and crack are unsaturable, reversible traps. A trap model based on saturable, reversible
Baseline hydrogen diffusion and permeation measurement in high purity iron was completed. Initial results on hydrogen diffusion and permeation in steels and their welds under high hydrogen pressure (up to 2,000 psi) have been obtained for A106 steel and X52 pipeline steels. The effects of weld microstructure on hydrogen trapping, diffusion
Influence of dislocations on hydrogen diffusion and Oger, Loïc and Malard, Benoît and Odemer, Grégory and Peguet, Lionel and Blanc, Christine Influence of dislocations on hydrogen diffusion and trapping in an Al-Zn-Mg aluminium alloy. (2019) Materials & Design, 180. 1-11. ISSN 0264-1275
MODELING OF TRAPPING/DETRAPPING OF Sep 09, 2015 · DFT:H TRAPPING IN VACANCIES DFT results presented here are deeply detailed in:Hydrogen diffusion and vacancies formation in W:Density Functional Theory calculations and statistical models, N Fernandez, Y Ferro, D Kato, Acta Materialia, 94 (2015) 307 Small number of atoms (54 atoms) Pure Single Crystal (where vacancies can be introduced)
Nov 01, 2013 · As the diffusion coefficient D is dependent of c, see Fig. 4, diffusion occurs in the region of a high diffusivity, which significantly accelerates the charging process. During discharging the hydrogen is, however, collected nearly uniformly in the whole specimen (see Fig. 8 ) and transported, predominantly in late stages, in the region of
The diffusion and trapping of hydrogen in steel The mobility of dissolved hydrogen in an iron lattice having a population of extraordinary, or trapping, sites for hydrogen is analyzed under the assumption of local equilibrium between the mobile and the trapped populations.
Tritium Diffusion in A12O3 and BeO - FOWLER - 1977 Alumina containing 0.2% MgO gave tritium diffusion coefficients 4 to 5 orders of magnitude higher than those for undoped A1 2 O 3, implying a significant impurity effect on tritium diffusion. Measured diffusion coefficients were many orders of magnitude lower than hydrogen diffusion coefficients in