Hydrogen Charging Research Articles

Investigations of temperature effects on hydrogen diffusion and hydrogen embrittlement of X80 pipeline steel under electrochemical hydrogen charging environment

The influence of temperature on hydrogen diffusion and hydrogen embrittlement of X80 steel was studied using electrochemical hydrogen charging. The hydrogen diffusion and subsurface hydrogen concentration in the steel increased with increasing the temperature. Macro slow strain rate tensile tests and microstructural analysis were performed to unveil the dependence of hydrogen-induced embrittlement susceptibility on temperature, which suggested a temperature threshold THE, max of 315 K. The demonstration of THE, max would be crucial for determining test temperatures of hydrogen-related engineering material applications.

Effect of Tempering Temperature on Hydrogen Embrittlement of SCM440 Tempered Martensitic Steel.

The effect of tempering temperature on the hydrogen embrittlement characteristics of SCM440 tempered martensitic steels was investigated in terms of their microstructure and hydrogen desorption behavior. The microstructures were characterized using scanning and transmission electron microscopy, as well as X-ray diffraction and electron backscattered diffraction analysis. Thermal desorption analysis (TDA) was performed to examine the amount and trapping behavior of hydrogen. The cementite morphology of the SCM440 tempered martensitic steels gradually changed from a long lamellar shape to a segmented short-rod shape with an increasing tempering temperature. A slow strain rate tensile test was conducted after electrochemical hydrogen charging to evaluate the hydrogen embrittlement resistance. The hydrogen embrittlement resistance of the SCM440 tempered martensitic steels increased with an increasing tempering temperature because of the decrease in the fraction of the low-angle grain boundaries and dislocation density. The low-angle grain boundaries and dislocations, which acted as reversible hydrogen trap sites, were critical factors in determining the hydrogen embrittlement resistance, and this was supported by the decreased diffusible hydrogen content as measured by TDA. Fine carbides formed in the steel tempered at a relatively higher temperature acted as irreversible hydrogen trap sites and contributed to improving the hydrogen embrittlement resistance. Our findings can suggest that the tempering temperature of SCM440 tempered martensitic steel plays an important role in determining its hydrogen embrittlement resistance.

Design and performance analysis of a PV-assisted alkaline electrolysis for hydrogen production: An experimental and theoretical study

The PV assisted alkaline electrolysis cell was established for hydrogen generation. Lab-made AgNiCu modified nickel foam cathodes were used in this system. The characterization was achieved using field emission scanning electron microscopy, energy-dispersive X-ray and X-Ray diffraction analysis. The electrochemical performance was investigated via linear sweep voltammetry, cyclic voltammetry, Tafel polarization measurements and electrochemical impedance spectroscopy. The electrolysis potential and time depended efficiency was monitored. The structural theoretical analysis of the electrode surface and hydrogen evolution characteristics were also determined applying Density Functional Theory and Ab-initio Molecular Dynamics simulations which identified the role of Ag decoration and Cu incorporation on the surface against water and proton adsorptions. The modified cathode (AgNiCuF) improved the hydrogen production performance owing to lower hydrogen onset potential (−1.1 V) and charge transfer resistance (0.362 ohm at −1.5 V).

The Effects of Electrochemical Hydrogen Charging on Charpy Impact Toughness and Dry Sliding Tribological Behavior of AISI 316H Stainless Steel

In this work, solution-annealed AISI 316H grade austenitic stainless steel was studied in terms of investigating the electrolytic hydrogen charging effects on the resulting Charpy impact toughness and dry sliding tribological behavior. Conventional Charpy impact bending tests were employed to study the mechanical response of the investigated material to dynamic loading conditions, whereas dry linear sliding tribological tests were used to study material friction and wear behavior. The obtained mechanical and tribological properties were correlated with corresponding fracture and tribological mechanisms, which were determined from morphological observations of fracture surfaces and tribological tracks. The applied testing procedures were individually carried out for the non-hydrogenated, hydrogen-charged, and dehydrogenated material conditions. The observed changes in individual properties due to applied hydrogen charging were rather small, which indicated the good resistance of solution-annealed AISI 316H steel against material degradation in currently used electrolytic hydrogenation conditions.

Effect of hydrogen charging on the mechanical characteristics and coating layer of CrN-coated aluminum alloy for light-weight FCEVs

Abstract To commercialize fuel cell electric vehicles, it is essential to reduce the weight of the components and lower the manufacturing cost. In this study, the effect of hydrogen charging on the mechanical characteristics of aluminum alloys and CrN coating was also investigated through cathodic hydrogen charging, indentation and scratch experiments. The delamination of the CrN coating by hydrogen charging was observed through the experiments. In addition, as the hydrogen charging time increased, the hardness of the aluminum alloy increased by about 29.7%, whereas the hardness of the CrN coating decreased by about 42.8%. In particular, in the scratch experiments, it was found that hydrogen embrittlement and hydrogen blistering occurred at the interface between the CrN coating layer and the aluminum alloy due to hydrogen permeation and diffusion. Therefore, the adhesion strength of the CrN coating decreased significantly. However, the CrN coating was shown to suppress hydrogen permeation into the aluminum alloy.

Formation and characterization of hydride rim structures in Zircaloy-4 nuclear fuel cladding tubes

Zirconium alloy tubes used as nuclear fuel cladding are subject to oxidation and subsequent hydrogen pickup during their long service in commercial light water reactors. The hydrogen picked up in the cladding can precipitate as a brittle hydride rim feature on the cladding outer surface. To better understand the effect of hydride rims on the fracture behavior of stress-relieved zirconium alloy cladding tubes, a procedure to produce these rim-like structures has been developed and is described herein. Extensive characterization of the ‘as hydrided’ tubes is performed.The hydrogen charging apparatus consists of a tube furnace with a quartz chamber that is connected to a vacuum pump as well as a bottle of pure hydrogen gas. The charging station uses a static charge of hydrogen as opposed to a flowing gas. The chief advantage of this approach is the ability to monitor the pressure drop in the hydriding chamber and correlate this pressure drop to a known rate of hydrogen pickup in the cladding tube. It was found that the hydrogen partial pressure, metal temperature, and surface treatment all clearly played a role in whether a hydride rim was formed. Extensive characterization of the hydride rims shows they consist of needle like platelets of δ phase hydrides (ZrH1.66) oriented in the circumferential direction with a radial spacing of several microns in a sandwich-like structure.

Phase Transformation and Electrochemical Feature of an AB4-Type La0.60Sm0.20Mg0.20Ni3.50Al0.20 Hydrogen Storage Alloy for Ni/MH Batteries

La–Mg–Ni-based alloys with a novel AB4-type superlattice structure is supposed as potential anode materials for nickel metal hydride (Ni/MH) batteries due to the excellent discharge ability at high rates and long cycling life. However, it is still challenging to achieve high phase content of the AB4-type structure during annealing due to the complex peritectic reaction of virous superlattice structures. Herein, we study the phase transformation of the AB4-type structure upon annealing and elucidate its effect on electrochemical characteristics based on a La0.60Sm0.20Mg0.20Ni3.50Al0.20 alloy. It is found that the AB4-type phase forms between 970 °C–1000 °C by a peritectic reaction of A5B19- and CaCu5-type phases. The existence of AB4-type phase drives the alloy a higher discharge capacity of 366 mAh g–1 at 60 mA g–1, and 135 mAh g–1 at 1800 mA g–1 owing to the advantages of charge transfer and hydrogen diffusion. Moreover, high capacity retentions of 88.7% and 79.3% at the 100th and 200th cycles are respectively achieved. Besides, the alloy with the AB4-type phase shows improved tolerance at a low temperature of –40 °C. We expect that our finding can provide guidance for developing AB4-type hydrogen storage alloy for Ni/MH.

Hydrogen-induced failure in a partially-recrystallized Al-Zn-Mg-Cu alloy with different aging conditions: Influence of deformation behavior dominated by microstructures

Hydrogen-induced failure in a partially-recrystallized Al-Zn-Mg-Cu alloy with different aging conditions was studied by in-situ electrochemical hydrogen charging method, and the hydrogen-induced cracking mechanism was elucidated by investigating the microstructure-dominated deformation behavior. It was found that in naturally-aged and peak-aged samples, cracks initiate at sample surfaces, and deformation dominated by shearing facilitates hydrogen diffusion, resulting in a high hydrogen embrittlement susceptibility. However, in the over-aged sample, deformation dominated by bypassing cannot transport hydrogen efficiently, which exerts no effect on crack initiation at the sample center. In addition, the same cracking pattern exists on all samples in silicone oil and in-situ hydrogen charging environments. The grain boundary of recrystallized grains is prone to strain localization, leading to intergranular cracking. In unrecrystallized grains, transgranular cracks propagate along intersections of slip lines and subgrain boundaries. This study improves the understanding of hydrogen embrittlement in new generation Al-Zn-Mg-Cu alloy by linking the existing hydrogen embrittlement mechanism to the deformation behavior dominated by microstructures.

Probing the water mediated proton transfer in histidine tautomerization

Histidine tautomerism plays a key role in the aggregation of amyloid peptides, which is important for understanding the origin of Alzheimer’s disease as well as its diagnosis and treatment. Herein, density functional theory calculations were performed using explicit water molecules and joint implicit/explicit water cluster models to explore the catalytic mechanism and the key role of water assistance effect in the histidine tautomerization reaction. To clarify the proton transfer mechanism involved in histidine tautomerization, three to five water molecules were used to catalyze the proton transfer process governing the transition between the histidine tautomers. Potential energy calculations showed that hiε·(H2O)n tautomerism proceeds via a single proton transfer pathway. Systematic analyses of the hydrogen bonds and charge distribution of the key components indicated that tautomerism can be promoted by reducing the number of assistant water molecules or involving the joint implicit/explicit water solvent effect. This study provides theoretical insights into the mechanism of water-assisted histidine isomerization as it relates to the Aβ aggregation hypothesis of Alzheimer’s disease.

Hardening effect of diffusible hydrogen on BCC Fe-based model alloys by in situ backside hydrogen charging

Hydrogen embrittlement is common in metallic materials and a critical issue in industries involving hydrogen-related processes. Here we investigate the mechanical response upon hydrogen loading of ferritic Fe-16Cr, Fe-21Cr and Fe-4Al alloys. We use a novel in situ setup for electrochemical backside hydrogen charging during nanoindentation. Single-phase ferritic Fe-Cr binary alloys with high hydrogen diffusivity and low solubility, are ideal for in situ studies during hydrogen charging, particularly the effect of diffusible and lightly trapped hydrogen is targeted. The hardness increases linearly with increasing hydrogen content until a quasi-equilibrium state between hydrogen absorption and desorption is reached while Young's modulus remains unaffected. Above this transient region, the slope of the absolute hardness experiences a drastic decrease. The hardness variation in Fe-21Cr is anisotropic as determined for (100), (110) and (111) oriented grains. Increasing the Cr content enhances the hardening effect in (100) orientation: a 16.7 % hardness increase is observed in Fe-21Cr, while Fe-16Cr, shows an increment of 10.8 %. A Fe-4Al alloy increases slightly in hardness by only 4.3 % at the applied current density of 3 mA/cm2. The hardening effect is caused by enhancing dislocation density, as revealed by studying the cross-section underneath the nanoindentation imprints.

Hydrogen charging of carbon and low alloy steel by electrochemical methods

Atomic hydrogen can be the result of different processes like electroplating, chemical and electrochemical pickling treatments, in welding or by cathodic processes in corrosive fluids. Moreover, adsorption of atomic hydrogen can affect materials in contact with high pressure gaseous hydrogen. Once entered the material, atomic hydrogen interacts with the metal structure and may produce a “damage” of various forms, such as Hydrogen Induced Cracking (HIC), delayed fracture, blistering and hydrogen embrittlement. In particular, when H2S is present (“sour service”), metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. Sour service materials must be used in compliance with international accepted standards, used worldwide in oil and gas activities, when fluids are classified as sour. The present study has been carried out in order to set up an electrochemical method to charge with hydrogen two typical pipeline materials, carbon and low alloy steels. The reason of the use of an electrochemical method is to avoid any critical conditions from the point of view of preparation, safety and disposal. Hydrogen content in the specimens was measured by two different methods: hot glycerol bath and Inert Gas Fusion (IGF) analysis. Hydrogen content in the specimens is about 0.6–2 ppm; mechanical performances were assessed by means of J integral tests: a pronounced decrease of fracture toughness was observed for H charged specimens.Graphical

Effects of hydrogen on the dynamic mechanical properties and microstructure of 7055 and 7A52 aluminum alloys

In the present work, the effect of hydrogen on the impact resistance of the 7055 and 7A52 aluminum alloys have been experimentally investigated by using split Hopkinson pressure bar (SHPB) and electrochemical hydrogen charging technique. It was first found that hydrogen induced stress chase after yield deformation in 7055 and 7A52 alloys. Meanwhile, hydrogen reduced the yield strengths of the two alloys. Besides, the evolution of microstructures including cracks, particles and dislocations has been quantitatively analyzed by polarizing microscope (PM), scanning electron microscope (SEM) and transmission electron microscopy (TEM). It has been found that both two aluminum alloys are sensitive to hydrogen embrittlement under high-speed deformation conditions. The hydrogen causes hydrogen compression cracks at grain boundaries, pores, and Al2Cu particles in the material, and the hydrogen cracking of both aluminum alloys after impact appeared to be layered, and the lower layer cracking was flat, which indicated that the hydrogen made the alloy embrittle to some extent. Besides, hydrogen reduces the hindering effect of copper-containing phase and large η phase on dislocation movement, which makes the dislocations distribution inside the 7055 alloy grains more uniform. The results show that 7000-series aluminum alloys are sensitive to hydrogen embrittlement under high-speed deformation conditions.

An experimental fracture mechanics study of the combined effect of hydrogen embrittlement and loss of constraint

This work presents a systematic investigation of the combined effect of hydrogen embrittlement and loss of constraint. The fracture mechanics experiments are performed on an advanced martensitic high strength steel using a single-edge-notch bend specimen, with different crack over height ratio, subjected to electrochemical in-situ hydrogen charging at various loading rates. It is found that the environmentally driven ductile-to-brittle transition region in fracture toughness is obtained for both the high and low constraint specimen configurations. This region is characterized by a change from transgranular dimple rupture to an intergranular mode of fracture. The transition region for the low constraint specimen is shifted towards longer hydrogen exposure times, which is an effect of the reduced hydrostatic stress ahead of the crack front compared to the high constraint specimen. The low constraint specimen exhibits significant plastic straining, which is reflected in a significant decrease in the fracture toughness due to hydrogen assisted transgranular dimple rupture.

Multi-objective optimization of a metal hydride reactor coupled with phase change materials for fast hydrogen sorption time

Recently, the utilization of phase change materials (PCM) for the heat storage/recovery of the metal hydride's reaction heat has received increasing attention. However, the poor heat management process makes hydrogen sorption very slow during heat recycling. In this work, the H2 charging/discharging performance of a metal hydride tank (MHT) filled with LaNi5 and equipped with a paraffin-based (RT35) PCM finned jacket as a passive heat management medium is numerically investigated. Using a two-dimensional mathematical model validated with our in-house experiments, the effects of design parameters such as PCM thermophysical properties and the fin size on hydrogen charging/discharging times of the MHT are investigated systematically. The results showed that the PCM's melting point and apparent heat capacity have a conflicting impact on the hydrogen sorption times, i.e., the low melting point and high specific heat capacity reduce the H2 charging time. In contrast, the hydrogen discharging time follows the opposite trend. As a result, a multi-objective optimization was conducted to simultaneously minimize the H2 charging/discharging times using the thermal properties and size of the PCM. The optimum solutions selected from the Pareto front show that the PCM melting point should be around 42–43 °C for fixed hydrogen ab/desorption pressures of 10/1.5 bar. Moreover, the comparison between the MHT-PCM using the optimized PCM and reference PCM showed that the former reduced the hydrogen charging/discharging times by 48.6 % and 4 %, respectively. At the same time, the hydrogen storage efficiency of the optimal design is 100 % as compared to 96 % for the reference design. Besides, among the practical PCMs, inorganic PCMs (salt hydrates and eutectics) display favorable hydrogen charging time below 3000 s at the expense of hydrogen discharging time (above 7000 s) in our case study.

2D-axisymmetrical modeling and experimental study of hydrogen absorption in copper coated metal hydride

The storage of hydrogen in metal hydride reactors is examined experimentally and numerically in this paper. In this respect, as-received LaNi5 powders are coated with different amounts of copper by using copper sulphate solution to accelerate the hydrogen charging processes. The thermal conductivity of the copper-coated storage material is found to reach up to 8 times of the uncoated powders. A two-dimensional axisymmetric model regarding complex heat and mass transfer occurring during hydrogen charging process in metal hydride reactors is numerically solved at macro level. The developed model is validated by using experimental data related to the amount of hydrogen stored and the reactor temperatures. In accordance with the experimental results, the simulation results show that more homogenous temperature distribution in the reactor can be obtained with the copper coating due to improved thermal properties. Moreover, charging time is also improved by the copper coating. However, since the reactor is loaded with coated/uncoated LaNi5 powders at the same weight of 65 g, the total amount of hydrogen stored decreases with the copper coating due to reduced amount of LaNi5.

Effects of hydrogen charge on the intergranular corrosion of high-defect-density ultrapure ferrite stainless steel

This research scrutinizes the intricate effects of hydrogen charging on crystal defects and passive film properties in high-defect-density 443 ultrapure ferritic stainless steel. It discerns that with non-saturated hydrogen at hydrogen traps, escalated hydrogen charging current density results in increased hydrogen capture. These trapped atoms fill the defects, thus mitigating the stress level and fostering the growth of chromium oxides within the passive film. Consequently, the alloy’s resistance to intergranular corrosion is enhanced.

Study on the formation mechanism of δ-titanium hydride by rotation electron diffraction

Rotation electron diffraction method was used to study the structures and crystallographic orientations of the face centered tetragonal structured γ-titanium hydride and the face centered cubic structured δ-titanium hydride by collecting the diffraction information of the hydrides and the matrix at the same time. It was found that the FCC001 δ-hydride is the result of phase transformation caused by continuing to charge hydrogen into γ-hydride. Therefore, we got the complete map of the paths in which hexagonal close-packed titanium transforms to stable δ-titanium hydrides with the increase of hydrogen atoms.

Synergistic effect of different testing environments on the hydrogen-induced mechanical degradation to establish the role of microstructural features on the failure of X70 pipeline steel

Hydrogen-induced mechanical degradation was evaluated in different environmental conditions on two X70 pipeline steels having the same composition but different thermomechanical processing parameters, and a further correlation between microstructural features and hydrogen embrittlement (HE) susceptibility was established. HE susceptibility was determined by performing the Slow Strain Rate Tensile Test (SSRT) in air, ex-situ hydrogen-charged, in corrosive media, in-situ hydrogen-charged and Charpy impact tests before and after hydrogen charging in a wide range of temperatures.The SSRT results indicated that the synergistic action of stress and hydrogen in in-situ charged sample leads to maximum HE susceptibility in both X70 steels. Charpy results demonstrated that ductile-to-brittle transition temperature (DBTT) increases after hydrogen charging. The texture analysis revealed that X70-2 with a higher volume fraction ratio of Ƴ-fiber/{100}<011> demonstrated improved HE resistance, whereas X70-1 with higher fractions of {113}<110> and {100} || ND demonstrated a higher DBTT than before and after hydrogen charged X70-2.

Thermodynamic properties of common salts in aqueous solutions

A relationship between the activity of hydrogen ions and charge activity in an aqueous solution has been developed in a previous study. That study also revealed that the potential energy of an aqueous solution can be obtained by multiplying the charge activity with electrostatic potential of the solution. In this study, negative potential energy equalling Gibbs energy of four common salt (NaCl, KCl, NaNO3 and KNO3) solutions were quantified using the charge activity. Then the entropies of those salt solutions were computed using the Gibbs energy, enthalpy, and the charge activity. Charge activities were computed using the pH of those solutions at room temperature. It was found that potential energy, Gibbs energy, enthalpy and entropy of a solution is related to the charge activity of a solution, not the ionic charge number as previously thought. When the concentrations of NaCl, KCl, NaNO3 and KNO3 increased in single solutions the entropies of those solutions tend to decrease allowing them to achieve orderly states leading the salt particles to crystalise. The findings of this study will lead to better understanding and utilization of thermodynamic properties during crystallization which is vital important in brine recovery.

Transient analysis and optimization of an off-grid hydrogen and electric vehicle charging station with temporary residences

In this research study, an off-grid zero energy refueling station for hydrogen fuel cell vehicles with the ability to charge battery-powered electric vehicles is designed and analyzed transiently. A temporary residence next to the charging station is designed to accommodate people who come to the charging station. The best energy supplier in terms of cost is determined. The insulation thickness of the temporary residence wall is optimized for five types of insulation and thickness between 0 to 0.7 m. Total cost over 20 years (system lifetime) is an objective function that should be minimized. Using Trnsys software, the charging station and temporary residence are simulated. The system's total costs for different insulation type and thickness is predicted using a machine-learning approach. The optimum insulation type and thickness are determined. According to the results, choosing a photovoltaic panel as a power source is up to 33,024 $ more cost-effective than wind energy for the mentioned system. The optimal insulation thickness is related to expanded polystyrene with a thickness of 0.24 m. Insulation thickness and type can affect the system's total cost intensively. The cheapest insulation is not the best in reducing total cost.