Hydrogen Diffusion Behavior Research Articles

Influence of Cold Working on Hydrogen Diffusion Behaviour in an Austenitic Steel with Transformation-Induced Plasticity

The main objective of this work was to obtain information about the hydrogen diffusion behaviour in a cold-worked austenitic stainless steel (X3CrMnNiMoN17-8-4) in which deformation-induced martensite formation occurs during mechanical deformation. Three different states of pre-deformation (31 %, 39 % and 49 %) that showed induced phase transformation from austenite to α’martensite as well as the solution-annealed material were part of this study. All samples were charged with hydrogen in a 0.1 M NaOH solution. This charging took place electrolytic with 10 mA cm-2 at three different temperatures (50 °C; 65 °C and 80 °C) in the double cell according to Devanathan and Stachurski. Due to the very slow diffusion of hydrogen through austenite, the samples were not charged until the equilibrium state was reached. To find out the necessary diffusion parameters, the data were fitted with numerical optimisation. Using this method, the effective diffusion coefficients of charging could be determined for all material states. The study also contains microscopic analyses to visualize the effect of cold working on the microstructure of the material. The appearance of α’-martensite significantly contributes to the susceptibility to hydrogen uptake leading to increasing diffusion coefficients in relation to higher pre-deformation.

Unraveling the substitution and strain-induced hydrogen diffusion performance of ZrCo-based intermetallics

The intermetallic compound zirconium-cobalt (ZrCo) is one of promising alternative materials used in the industry of hydrogen isotope storage. Nevertheless, the deterioration of absorption/desorption kinetics induced by hydrogen-induced disproportionation severely impedes its large-scale promotion. This work concentrates on studying the hydrogen diffusion behavior of ZrCo hydrides due to element substitution combined with triaxial strain (−3% ∼ 3 %) under the framework of the first-principles study. The results indicate that the formation of small-volume hydrogen vacancies is facilitated by Ti substitution as well as compressive strain. Moreover, hydrogen diffusion barrier is reduced after the Ti substitution, leading to a significant increase in diffusion rate. When the Ti content reaches 15 %, it is more conductive to improving the dehydrogenation kinetics of hydride. As the compressive strain increases, the diffusion barrier is reduced to a minimum at −3%. In addition, the Ti substitution and strain play a synergistic effect for enhancing hydrogen diffusion rate. Also, it is found that the performance of hydrogen diffusion and dehydrogenation kinetics is attributed to lattice stability associated with the density of states at the Fermi level. This work provides a new insight to improve dehydrogenation kinetics of ZrCoH3 by taking into account element substitution and external strain.

Influence of microstructure on the hydrogen diffusion behavior in dual-phase steels: an electrochemical permeation study

Influence of microstructure on the hydrogen diffusion behavior in dual-phase steels: an electrochemical permeation study

In Situ Investigation of Hydrogen-Induced Cracking Behavior in Linepipe Steel Under Different Environments

NACE MR0175/ISO 15156 provides the severity of a sour environment defined as a function of pH and H2S partial pressure for sulfide stress cracking. Although hydrogen-induced cracking (HIC) is also a major issue of linepipes exposed to a sour environment, the severity diagram does not necessarily correspond to the HIC susceptibility. Recently, from the viewpoint of fitness-of-purpose, the severity diagrams for HIC have been proposed based on the concept of equal hydrogen concentration. From this concept, HIC susceptibility corresponds well to the steady-state hydrogen permeability obtained from the hydrogen permeation test method. In this study, in order to clarify the relationship between HIC susceptibility and hydrogen diffusion behavior, in situ crack inspection during the HIC test and finite element method analysis of hydrogen diffusion were performed. The in situ inspection technique using phased-array ultrasonic testing which can capture the time dependence of crack distribution, and HIC initiation and propagation behaviors were clearly visualized and investigated. It was found that crack initiation and propagation stabilize as hydrogen concentration reaches a steady-state value throughout the specimen and the result was considered evidence that the HIC susceptibility corresponded with the steady value of hydrogen permeability.

Hydrogen adsorption and diffusion on doped Zr(0001) surfaces: A first-principles study

The hydrogen adsorption and diffusion behaviors on the clean and a series of element doped Zr(0001) surfaces are studied through first-principles calculations. Among the studied doping elements, Cu, Co, Y, and Mg prefer to substitute Zr on the topmost surface layer, Al, Pd, Ir, and Si are favored from topmost layer to several surface layers down, while Mo is not favored. Independent of the substitution energies, Mo, Co, and Ir induce a symmetry-breaking local distortion surface structure. Based on the obtained geometries, it is found that most dopants promote the hydrogen adsorption on their next nearest neighbor sites but hinder it on the nearest neighbor sites. Most of the dopants also promote both the hydrogen diffusion on the surface plane and the hydrogen penetration into the subsurface layers. The results indicate that element doping may facilitate the hydride nucleation in Zr alloys.

The d band center as an indicator for the hydrogen solution and diffusion behaviors in transition metals

Understanding the hydrogen solution and diffusion behaviors are crucial to design the hydrogen embrittlement resistant structural materials in industry applications. Whether there exists an indicator for prediction of the hydrogen solution and diffusion behaviors is an important but unclarified question. In this study, the hydrogen solution and diffusion behaviors in transition metals and alloys were investigated by density functional theory (DFT) and nudged elastic band (NEB) method calculations. The calculation results reveal that the d band center is directly correlated with hydrogen solution ability in structural materials. The strain and alloying effects on the variations of hydrogen solution energy and d band center have also been considered and the well variation consistency between them is established. With respect to the hydrogen diffusion in transition metals, the transition state has a lower d band center than the initial state. Especially, the hydrogen diffusion energy barrier is proportional to the d band center difference between the initial state and transition state in alloying Fe. Thus the d band center can be regarded as an indicator for hydrogen solution and diffusion in structural materials, which can enlighten us to design the structural materials with high hydrogen embrittlement resistance.

Effect of cold deformation on the hydrogen permeation in a dual-phase advanced high-strength steel

The diffusion behaviour of hydrogen in a 1180 MPa ferrite/martensite dual-phase (DP) advanced high-strength steel was investigated using electrochemical permeation tests in the following conditions: as manufactured, cold deformed and annealed. The effective hydrogen diffusion coefficient (0.46 × 10−6 cm2 s−1) for the cold-deformed DP1180 was considerably lower than for the steel as-received (0.74 × 10−6 cm2 s−1) and annealed (2.2 × 10−6 cm2 s−1). The increased diffusible hydrogen concentration by cold deformation was attributed to increased reversibly trapped hydrogen. This work provides an experimental underpinning for the increased hydrogen embrittlement sensitivity caused by plastic deformation of the steel.

Evaluation of hydrogen diffusion and trapping in nickel Alloy 625 by thermal desorption spectroscopy

This study presents hydrogen diffusion and trapping in the nickel Alloy 625 by employing the hot extraction test and the thermal desorption spectroscopy (TDS) analysis. Combined with electrochemical permeation test, the impact of grain size and grain boundary carbide on hydrogen diffusion are investigated. The results manifeste that the effective hydrogen diffusivity can be expressed as D=1.03×10−7exp(−46.44kJmolRT)m2/s for the sample with a grain size of ∼8 μm. The diffusion activation energy ED for hydrogen is determined as 42.05–48.10 kJ/mol. The activation energy E associated with interstitial sites/elastic field of dislocations and reversible traps is 17.92–20.73 kJ/mol and 24.87–27.13 kJ/mol, respectively. Moreover, the reduction in grain size and the presence of grain boundary carbide can lower hydrogen diffusivity by locally changing the diffusion and trapping behavior of hydrogen.

Role of vanadium content in hydrogen diffusion behavior in X80 pipeline steel

ABSTRACT The role of vanadium content in hydrogen diffusion behaviour in X80 pipeline steel has been investigated. The results show that the hydrogen diffusion coefficient decreases from 1.54 × 10−6 cm2 s−1 in 1# steel with 0.03 wt-% vanadium to 9.97 × 10−7 cm2 s−1 in 3# steel with 0.14 wt-% vanadium due to the increase in irreversible and reversible traps. With the increase in vanadium content, more vanadium carbides precipitate in tested steels. The length (or number) of the low angle grain boundaries and special grain boundaries increase because of grain refinement, making the number of reversible traps increase. The dynamic condition of diffusible hydrogen in 3# tested steel with the largest number of hydrogen traps is the weakest. To weaken hydrogen-induced cracking dynamic condition, it is recommended to add 0.14 wt-% vanadium to X80 pipeline steel.

Study on leakage and explosion consequence for hydrogen blended natural gas in urban distribution networks

It appears to be the most economical means of transporting large quantities of hydrogen over great distances by the existing natural gas pipeline network. However, the leakage and diffusion behavior of urban hydrogen blended natural gas and the evolution law of explosion characteristics are still unclear. In this work, a Computational Fluid Dynamics three-dimensional simulation model of semi-confined space in urban streets is developed to study the diffusion process and explosion characteristics of hydrogen-blended natural gas. The influence mechanism of hydrogen blending ratio and ambient wind speed on the consequences of explosion accident is analyzed. And the dangerous area with different environmental wind effects is determined through comparative analysis based on the most dangerous scenarios. Results indicate that the traffic flow changes the diffusion path of the jet, the flammable gas cloud forms a complex profile in many obstacles, high congestion level lead to more serious explosion accidents. Wind effect keeps the flammable gas cloud near the vehicle flow, the narrow gaps between the vehicles aggravate the expansion of the flammable gas cloud. When the wind direction is consistent with the leakage direction, hydrogen blended natural gas is gathered in the recirculation zone due to the vortex effect, which results in more serious accident consequences. With the increase in hydrogen blending ratio, the higher content of H and OH in the gas mixture significantly increases the premixed burning rate, the maximum overpressure rises rapidly when the hydrogen blend level increases beyond 40%. The results can provide a basis for construction safety design, risk assessment of leakage and explosion hazards, and emergency response in hydrogen blended natural gas distribution systems.

Hydrogen diffusion and trapping in nickel-based alloy 625: An electrochemical permeation study

This work studied the effect of cathodic charging conditions on hydrogen diffusion and trapping behavior in a nickel-based Alloy 625 using the electrochemical permeation approach. Results showed that the effective diffusion coefficient of hydrogen can be expressed as Deff=1.82×10−7exp(−44.46kJmolRT)m2/s. A sinusoidal trend in Deff with charging current density was observed showing a deflection point at -40 mA/cm2, which contributes to the most efficient hydrogen permeation. In addition, the thermodynamic relationship between hydrogen activity and electrochemical potential was investigated. Furthermore, the energy associated with the solubility energy of interstitial hydrogen and reversible trapping site was determined as 9.90 kJ/mol and 26.04 kJ/mol, respectively.

Effect of Mo and Nb on mechanical properties and hydrogen embrittlement of hot-rolled medium-Mn steels

The effects of Mo and Nb on the mechanical properties and hydrogen embrittlement (HE) of hot-rolled medium-Mn steel were investigated. The diffusion behavior of hydrogen was examined using an electrochemical hydrogen permeation test. The mechanical properties and HE were studied using a slow strain rate test. The results show that most Mo and Nb served as solid-solution atoms in the hot-rolled steels, and little carbide content was observed. Both Mo and Nb increased the volume fraction of retained austenite (VA), decreased the starting temperature of martensitic transformation (MS), and retarded the martensite transformation. The effect of Nb was more pronounced. Simultaneous addition of Mo and Nb had a synergistic effect on increasing VA, decreasing MS, and retarding martensite transformation. The elongation of the samples increased with an increase in VA. The strength exhibited the opposite trend. A small amount of Nb (0.04 wt%) significantly improved the HE resistance of steels to a much greater extent than Mo (1 wt%). Filmy retained austenite formed along the primary austenite grain boundaries because of the Nb addition; it inhibited hydrogen-induced cracks, leading to better HE resistance. Blocky retained austenite, formed by the simultaneous addition of Mo and Nb, deteriorated the HE resistance.

A Facile Strategy to Realize Rapid and Heavily Hydrogen-Doped VO2 and Study of Hydrogen Ion Diffusion Behavior

Heavily hydrogen-doped VO2 has drawn broad interest due to the modulation of versatile electronic phase transition and structural transition, while it is still challenging for highly efficient and fast hydrogen incorporation in VO2. Herein, we provide a facile approach to achieving rapid and high-concentration hydrogen-doped VO2 preparation. The as-prepared VO2 film instantaneously converted to a partially metallic phase once it was immersed into NaBH4 solution due to the introduction of a light hydrogen dopant. Strikingly, high-concentration hydrogen incorporation into VO2 was achieved as the solution temperature increased over the phase transition temperature. Based on the first-principles calculation, we investigated the diffusion behaviors of hydrogen in M-VO2 and R-VO2 that migrated from the surface to the subsurface and in bulk. The detailed formation energy calculation suggested that the presence of R-VO2 was beneficial to realize heavily H-doped VO2, while the thermodynamic property accelerated the reaction process. The current findings not only supplied a novel strategy to realize fast and high-concentration hydrogen incorporation in VO2, shedding light on hydrogenated metal oxide materials, but also brought insight into a comprehensive understanding of hydrogen diffusion behavior in VO2.

Hydrogen absorption and diffusion behaviors in cube-shaped palladium nanoparticles revealed by ambient-pressure X-ray photoelectron spectroscopy

The hydrogen absorption and diffusion processes in cube-shaped palladium (Pd) nanoparticles (NPs) were studied by the combination of ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and density functional theory (DFT) calculations. A size dependence of the subsurface hydrogen absorption was observed. More hydrogen atoms were absorbed in the subsurface of the smaller-sized Pd NPs owing to the enhancement of the diffusivity of H atoms from the surface into the subsurface rather than the adsorption or absorption rates at the initial stages. This results from the weakened Pd-H bond caused by surface disordering of Pd NPs with the reduction of the size of the particles. Furthermore, we discuss the H absorption sites in the bulk by comparing the relative Pd 3d core-level binding energy shifts of the Pd atoms obtained from the AP-XPS results and the theoretical calculations. The octahedral (O) sites are shown to be more favorable than the tetrahedral (T) sites for hydrogen occupation by comparing the experimental results and theoretical calculations. Finally, we proposed an interaction model between hydrogen and the Pd NPs during H2 absorption and diffusion to provide new insights into the hydrogen absorption process.

過酷事故時の原子炉格納容器・原子炉建屋の安全性解析コードBAROCによる原子炉建屋内気相挙動解析

We developed the CFD analysis code BAROC for the reactor containment vessel and reactor building in a situation of severe accident. BAROC can analyze the three-dimensional thermal-hydraulics of multi-component gas and FP (fission product) aerosol in detail. By applying the implicit method and partially parallel processing, high-speed calculation is possible even for large-scale systems. The physical model and numerical solution method used in BAROC, as well as the results of analysis of the leakage and diffusion behavior of hydrogen and FP in the reactor building at the time of the accident of the Fukushima Daiichi Nuclear Power Plant are introduced.

Diffusion Behavior of Hydrogen in the Ground and Atmosphere when Leaking from Underground Pipes

Diffusion Behavior of Hydrogen in the Ground and Atmosphere when Leaking from Underground Pipes

高強度鋼板中の水素拡散挙動に及ぼす張出し加工の影響

The hydrogen diffusion behavior in a tempered martensitic steel sheet with 1-GPa grade tensile strength was investigated utilizing a newly developed hydrogen visualization technique using an Ir complex, whose color changes from yellow to orange due to its reaction with hydrogen. The hydrogen permeation through the steel sheet could be monitored from the color change of the Ir complex. Furthermore, the breakthrough time of hydrogen through the specimen could be qualitatively evaluated from the changes in the brightness of the Ir complex. This hydrogen visualization technique was also applied to a steel sheet stretch-formed using a hemisphere punch to simulate press-forming of automotive structural parts. The hydrogen breakthrough time around the top of the specimen was long and decreased with increasing the distance from the top. According to the plastic strain distribution of the specimen calculated by the finite element method, the hydrogen breakthrough time increased with increasing plastic strain. It was considered that the introduction of plastic strain decreased the hydrogen diffusion coefficient due to the introduction of dislocations acting as hydrogen trap sites, resulting in the increase of hydrogen breakthrough time.

Investigation of hydrogen diffusion behavior in 12Cr2Mo1R(H) steel by electrochemical tests and first-principles calculation

PurposeThis paper aims to study the mechanism of hydrogen embrittlement in 12Cr2Mo1R(H) steel, which will help to provide valuable information for the subsequent hydrogen embrittlement research of this kind of steel, so as to optimize the processing technology and take more appropriate measures to prevent hydrogen damage.Design/methodology/approachThe hydrogen diffusion coefficient of 12Cr2Mo1R(H) steel was measured by the hydrogen permeation technique of double electrolytic cells. Moreover, the influence of hydrogen traps in the material and experimental temperature on hydrogen diffusion behavior was discussed. The first-principles calculations based on density functional theory were used to study the occupancy of H atoms in the bcc-Fe cell, the diffusion path and the interaction with vacancy defects.FindingsThe results revealed that the logarithm of the hydrogen diffusion coefficient of the material has a linear relationship with the reciprocal of temperature and the activation energy of hydrogen atom diffusion in 12Cr2Mo1R(H) steel is 23.47 kJ/mol. H atoms stably exist in the nearly octahedral interstices in the crystal cell with vacancies. In addition, the solution of Cr/Mo alloy atom does not change the lowest energy path of H atom, but increases the diffusion activation energy of hydrogen atom, thus hindering the diffusion of hydrogen atom. Cr/Mo and vacancy have a synergistic effect on inhibiting the diffusion of H atoms in α-Fe.Originality/valueThis article combines experiments with first-principles calculations to explore the diffusion behavior of hydrogen in 12Cr2Mo1R(H) steel from the macroscopic and microscopic perspectives, which will help to establish a calculation model with complex defects in the future.

Modeling and analysis of hydrogen diffusion in an enclosed fuel cell vehicle with obstacles

Hydrogen has been utilized in FCV and leakage can cause safety issues. In this study, the vehicle is simplified as a cuboid enclosure with obstacles. The influence of obstacle locations on the hydrogen diffusion behavior is investigated with the iso-surfaces of 1% and 4% volume fraction of hydrogen. The time of the iso-surface of 4% volume fraction to reach the ceiling and the sidewalls without any obstacles is 1.42 and 1.25 times of that with an obstacle, respectively. Both height and the width of the flammable zone in the enclosure with an obstacle are greater than that without obstacles. The distance between the obstacle and the leakage affects significantly the hydrogen diffusion and the influence of the obstacle on the hydrogen diffusion strengthens with the decrease of the distance. Yet as the distance keeps same, the obstacle position relative to the leakage has no significant effect on hydrogen diffusion, and it makes little effect difference whether the obstacle is located in front of leakage or side of leakage.

Safety analysis of leakage in a nuclear hydrogen production system

Due to its unique advantages, such as clean and pollution-free, hydrogen energy has gradually improved its energy transition position. Constructing nuclear hydrogen production systems is a necessary means to achieve large-scale hydrogen production, and the study of hydrogen leakage and diffusion behavior is critical to commercializing hydrogen production systems. In engineering practice, the distance between the hydrogen storage device and the nuclear power plant is an important indicator to measure the safety of nuclear hydrogen production. To study the influence of gas storage tank's own conditions and external environmental conditions on leakage diffusion, influencing factors such as wind speed, leakage direction, leakage diameter, leakage height, and leakage angle are discussed in the present study. By calculating severe working conditions combined with the above multiple factors, the longest distance of hydrogen diffusion is determined. Finally, peak overpressure impact generated by hydrogen explosion was evaluated, and the minimum separation distance required to avoid safety risks was predicted. The results demonstrate that when the wind direction is consistent with the leakage direction, and the leakage angle is 0°, the higher the wind speed, the larger the leakage diameter and the lower the leakage height, resulting in a longer diffusion distance. Under more extreme and severe working conditions, the diffusion distance of combustible hydrogen cloud can reach as far as 237 m. Once hydrogen diffusion explodes, the minimum separation distance required is about 338 m. This research provides an effective method for safety risk assessment of a nuclear hydrogen production system.