Behavior Of Hydrogen In Metals Research Articles

Dynamics of Atomic Hydrogen in Palladium Probed by Neutron Spectroscopy

The behavior of hydrogen in metals has attracted considerable attention in fundamental and applied research areas for many decades. Among metals, palladium is remarkable because it can absorb large...

Behavioral Analysis of Hydrogen in Metals under the Effect of H2S Corrosion Using a Layer-stripping Micro-hardness Technique

In order to study the distribution behavior of hydrogen in metals under the condition of H2S corrosion, a layer-stripping micro-hardness test was designed to analyze the hydrogen distribution along the depth of hydrogen-charged 45 high-quality structural carbon steel at three different hydrogen sulfide concentrations and four corrosion periods in this study. The results show that there is a terminal solid solubility of hydrogen in the metal for hydrogen sulfide solutions over various concentrations and corrosion periods. A hydrogen-saturated layer is produced by hydrogen diffusing through the metal from an unsaturated state to a fully saturated state. The hydrogen-saturated layer is not affected by the concentration of the corrosion, but its thickness increases as the corrosion period increases. In this way, we established a new hydrogen diffusion model in metals.

Simulation of Thermal Desorption of Hydrogen from Titanium Hydride under the Influence of an Ion Beam

The behavior of hydrogen in metals and their alloys is of great interest, since hydrogen–metal systems are used in practice for absorption of nuclear radiation, in neutron sources, and for hydrogen storage. This study is focused on simulation of the behavior of hydrogen in titanium hydrides at ultrahigh concentrations of H in TiH2 + x. Numerical methods of continuum mechanics are used. The structure of the hydrogen sublattice of titanium hydride is taken into account in the model of diffusion and thermal desorption of H. This makes it possible to model the thermal desorption of hydrogen under irradiation with a beam of hydrogen ions.

A method to calculate hydrogen trap binding energy in austenitic stainless steel using local equilibrium model

The trap binding energy is an important parameter to understand the behavior of hydrogen in metals. Unfortunately, a reliable and practical method to calculate the hydrogen trap binding energy of austenitic stainless steels (γ-SS) is still lacking. In this work, the validity of local equilibrium model (LEM) for simulating the hydrogen desorption spectrum of γ-SS is studied first. Results show that LEM can be used to calculate the hydrogen thermal desorption spectrum of γ-SS reliably when the specimen thickness and heating rate are small enough. Then, an effective hydrogen pre-discharging method is used to simplify the numerical fitting of hydrogen desorption spectrum, and a method to calculate the hydrogen trap binding energy in γ-SS is developed using LEM. Finally, the hydrogen trap binding energy of dislocation in S30408 is calculated to be 26.3 kJ/mol on the basis of experimental hydrogen thermal desorption spectrum using the developed method.

First-principles calculation of H vibrational excitations at a dislocation core of Pd

Palladium is an ideal system for understanding the behavior of hydrogen in metals. In Pd, H is located both in octahedral sites and in dislocation cores, which act as nanoscale H traps and form Cottrell atmospheres. Adjacent to a dislocation core, H experiences the largest possible distortion in alpha-Pd. Ab initio density-functional theory computes the potential energy for a hydrogen in an octahedral site in alpha-Pd and in a trap site at the core of a partial of an edge dislocation. The Pd partial dislocation core changes the environment for H, distorting the H-Pd bonding which changes the local potential, vibrational spectra, and inelastic form factor for an isolated H atom. The decrease in excitation energy is consistent with experiments, and the calculations predict distortions to the H wavefunction.

Formation of nickel hydrides in reactive plasmas

The behaviour of hydrogen in metals has attracted scientific attention for many decades and is interesting from both basic research and technological points of view. Metal hydrides find a wide range of applications of which the most prominent is the reversible hydrogen storage. This is of great importance in view of possible future hydrogen economy. Moreover the high diffusivity of hydrogen also makes nanoscaled Me-H systems interesting possibilities for sensor applications, and surface reactions with hydrogen on Pt, Pd, Ni, and other metals are applied in catalysis, particularly in fuel cells.

Analysis of hydrogen behaviour in crack growth tests of γ-TiAl by means of the hydrogen microprint technique

To elucidate the mechanism of hydrogen embrittlement, the behaviour of hydrogen in metals is investigated by the hydrogen microprint method. This is an attractive method in that it enables the hydrogen released from the metal surface during plastic deformation to be observed. The hydrogen behaviour in fatigue and sustained-load crack growth of γ-TiAl intermetallic compounds has been studied by means of the hydrogen microprint technique. Both fatigue crack growth and sustained-load crack growth were accelerated by the hydrogen. The region of hydrogen accumulation could easily be observed by the hydrogen microprint technique. In the case of sustained-load crack growth, it is found that hydrogen is released from the surface in the high hydrostatic stress field around the crack tip. The hydrogen microprint technique revealed that the effect of the hydrostatic stress is very large in the hydrogen accumulation around the crack tip. In fatigue crack growth, the amount of silver precipitation is discussed, which is correlated with the amount of hydrogen accumulation.

Behavior of hydrogen in fracture and friction of metals and alloys

The negative effect of hydrogen on the properties of metals and alloys is demonstrated by the results of many studies. However, the mechanism of the behavior of hydrogen in metals still remains unclear. The present work is devoted to the effect of magnetic and electric fields on the diffusion of active hydrogen and to its interaction with impurity elements in metals and alloys in fracture and friction.

Modelling of hydrogen behavior in metals by muons

Positive muons substituting for protons in metals can be used to study various aspects of the behavior of hydrogen in metals and associated changes in the properties of the host material: this concerns e.g. the hydrogen (muon) lattice site, lattice relaxation, charge screening, diffusion as well as hydrogen induced changes in magnetic properties etc. Relevant examples are presented.

Channelling study on the lattice location of hydrogen in metals utilizing a nuclear reaction

The behaviour of hydrogen in metals has been investigated by a channelling method utilizing a nuclear reaction1H(11B, α)αα. The results are briefly summarized.

The quantum simulation of metal-hydrogen systems and the analysis of diffraction experiments

Abstract The path-integral simulation technique is used to study an empirical model for hydrogen and deuterium in niobium. This simulation method fully incorporates quantum effects, which are known to play an important role in the behaviour of hydrogen in metals, especially at low temperatures. It is argued that the density distribution of hydrogen is a key quantity in understanding metal-hydrogen systems since it depends sensitively on the metal–hydrogen interaction and since it is directly related to structure factors measured by diffraction experiments. We present simulation results for the density distribution of the niobium–hydrogen and niobium–deuterium systems in real space at 300,423, 500 and 700 K. We calculate the relevant structure factors and compare with existing diffraction data. We conclude firstly that the simulation results can be directly compared against diffraction data and such comparisons provide an important test of the interaction model on which the simulation is based and secondly...

Theory of the phase-change behavior of hydrogen in metals containing metallic impurities: The hydrogen–niobium–molybdenum system

A theory of the phase-change behavior of hydrogen in metals containing substitutional impurities is described. A lattice-gas model is developed which includes both direct electronic and indirect elastic interactions between hydrogen atoms. The interactions between hydrogen atoms and the randomly distributed impurity atoms are treated as a random field in analogy with the random field Ising model. The model is applied to the hydrogen–niobium–molybdenum system. Monte Carlo simulation is used to calculate the free energy and incoherent phase diagrams. The calculation predicts that even small amounts (5%–15%) of molybdenum cause the disappearance of the α–α′ coexistence region found in Nb–H. In addition the α–β transition, which is first order in Nb–H, becomes second order above a certain temperature (the tricritical point). These results are in qualitative agreement with experiment.

Two-state random walk model of lattice diffusion. 1. Self-correlation function

Diffusion with interruptions (arising from localized oscillations, or traps, or mixing between jump diffusion and fluid-like diffusion, etc.) is a very general phenomenon. Its manifestations range from superionic conductance to the behaviour of hydrogen in metals. Based on a continuous-time random walk approach, we present a comprehensive two-state random walk model for the diffusion of a particle on a lattice, incorporating arbitrary holding-time distributions for both localized residence at the sites and inter-site flights, and also the correct first-waiting-time distributions. A synthesis is thus achieved of the two extremes of jump diffusion (zero flight time) and fluid-like diffusion (zero residence time). Various earlier models emerge as special cases of our theory. Among the noteworthy results obtained are: closed-form solutions (ind dimensions, and with arbitrary directional bias) for temporally uncorrelated jump diffusion and for the ‘fluid diffusion’ counterpart; a compact, general formula for the mean square displacement; the effects of a continuous spectrum of time scales in the holding-time distributions, etc. The dynamic mobility and the structure factor for ‘oscillatory diffusion’ are taken up in part 2.

Structural Behaviour of Hydrogen in Metals and Intermetallic Compounds

Structural Behaviour of Hydrogen in Metals and Intermetallic Compounds

On the non‐ideal solution behavior of hydrogen in metals

AbstractHydrogen solubility in Pd and in Pd‐Rh, Pd‐Ag, and Ag‐Cd alloys is related to the position of the Fermi level and to clustering, brought about by lattice strain. The clustering model also requires the existence of specific heat anomalies observed in Pd‐H and Ta‐H.