Hydrogen Charging Time Research Articles

Thermodynamic performance study of hydrogen–oxygen combined cycle with high-pressure proton exchange membrane electrolysis cell for hydrogen energy storage

As a competitive energy storage method, hydrogen storage plays a vital role in improving the utilization of renewable energy and reducing carbon emissions. This paper proposes a novel hydrogen energy storage (HES) system with the goal of clean, efficient and simple structure. The system consists of high-pressure proton exchange membrane electrolytic cell (PEMEC) and hydrogen–oxygen combined cycle (HOCC). No hydrogen compressor is used in this system, and water is recycled. Aspen Plus and embedded Fortran are used for system simulation. Based on the simulation results, the system was evaluated by energy, exergy, and sensitivity analysis. The research results show that under the design conditions, the system’s round-trip thermal, exergy, and electrical efficiency are 86.25%, 40.87%, and 38.25%, respectively. The energy storage density can reach 20.35 kWh·m−3. Besides, the variation law of system performance with parameters is also obtained. PEMEC operating pressure, current density, turbine inlet pressure, and combustion chamber water injection flow rate were considered as the main influencing parameters. Increasing the operating pressure of PEMEC can effectively increase the energy storage density. Current density mainly affects hydrogen production rate and charging time. Increasing turbine inlet pressure can improve system efficiency. The water injection flow rate mainly affects the turbine inlet temperature, and the increase in water injection flow will lead to a decrease of discharge efficiency. In summary, this study of a new hydrogen energy storage system provides theoretical guidance and a new idea for the application of hydrogen energy storage systems.

Hydrogen Embrittlement of CoCrFeMnNi High-Entropy Alloy Compared with 304 and IN718 Alloys

The hydrogen embrittlement (HE) behaviors of a CoCrFeMnNi high-entropy alloy (HEA), 304 stainless steel (304SS) and IN718 alloys were studied and compared via electrochemical hydrogen pre-charging, slow strain rate tensile tests, and fracture surface analysis. The results demonstrate that the HEA exhibited the greatest HE-resistance, followed by 304SS and then IN718 alloy, when the alloys were charged at 1.79 mA cm−2 for 24 h and 48 h, and 179 mA cm−2 for 2 h. Hydrogen-induced reduction in ductility was observed for 304SS and IN718 alloys, whereas the hydrogen-affected fracture strain of the HEA was dependent on the hydrogen charging time. The resistance to HE was improved at a short hydrogen charging time (24 h), but reduced at a long charging time (48 h). This is attributed to the competing mechanisms between hydrogen-enhanced twin formation and HEDE (hydrogen-enhanced decohesion).

Effect of hydrogen on super-elastic behavior of NiTi shape memory alloy wires: Experimental observation and diffusional-mechanically coupled constitutive model

NiTi shape memory alloys (SMAs) are inevitably in contact with hydrogen in specific service environments, which can degrade their mechanical behaviors. In this work, the effect of hydrogen on the super-elasticity of NiTi SMA orthodontic wires is investigated experimentally and theoretically. Firstly, cathodic hydrogen charging was performed for the wires at a current density of 10A/m2 with various charging times (2.5min, 5min, 7.5min and 10min) and charging lengths (20 mm, 40 mm, 60 mm and 80 mm) in 0.5 mol/L H2SO4+2 g/L CH4N2S electrolyte solution at room temperature. Then, ex-situ tension-unloading tests were carried out shortly after the hydrogen charging. The stress-strain responses showed a two-step martensite transformation (MT), i.e., the start stress of MT for the region with hydrogen charging is much larger than that without hydrogen charging. Based on the experimental observations, a diffusional-mechanically coupled constitutive model is constructed. Elastic strain, transformation strain, transformation-induced plasticity (TRIP) and hydrogen swelling deformation are considered. The effect of hydrogen on the thermo-mechanical behavior of NiTi SMA is taken into account by introducing the hydrogen concentration (HC)-dependent critical temperatures of MT and slip resistance of TRIP. The thermodynamic driving forces of MT and TRIP are derived from the constructed Helmholtz free energy and dissipation inequality. The balance equation of hydrogen diffusion is obtained by the chemical potential and Fick's diffusion law. To obtain the overall response of the wire with a heterogeneous HC field, a scale transition rule is proposed. The capability of the proposed model to describe the super-elasticity of NiTi SMA with various hydrogen charging times and charging lengths is validated by comparing the predicted results with the experimental ones.

Phase Change Cooling of a Metal Hydride Reactor for Rapid Hydrogen Absorption

As the world is keen on cleaner and sustainable energy, hydrogen energy has the potential to be part of the green energy transition to replace fossil fuels and mitigate climate change. However, hydrogen energy storage is a difficult task since physical storage in the form of compressed gas under high pressure is associated with safety issues. Another form of hydrogen storage is material-based storage, which is the safest way to store hydrogen energy in a particulate matter, known as metal hydrides. Metal hydrides can store hydrogen at room temperature and use less volume to store the same amount of hydrogen compared to classical gas tanks. The challenges with the metal hydrides reactor are their slow charging process and the requirement of proper thermal management during the charging process. In this study, a metal hydride reactor model is developed in COMSOL Multiphysics, and the associated heat transfer simulations are performed. The main objective of this research is to optimize the cooling channel design in the metal hydride reactor, where the R-134a coolant rejects heat through both latent and sensible heat transfer. The study showed that the phase-changing coolant and varying convection coefficient along the length of tubes significantly reduce the hydrogen charging time and the peak temperature of the reactor during hydrogen absorption. The pumping power analysis for the R-134a flow was also conducted. The computation results reveal that coolant channel configurations with nine or more tube-passes require significantly large pumping power.

Effect of hydrogen charging time on hydrogen embrittlement of CoCrFeMnNi high-entropy alloy

The effect of hydrogen on mechanical properties and failure mechanism of a CoCrFeMnNi high-entropy alloy was evaluated by in/ex-situ tensile tests and electron backscatter diffraction. The results indicate that yield strength first decreases and then increases as hydrogen charging time increases, which is attributed to the competition between the hydrogen-induced softening effect and the hydrogen-enhanced twinning formation effect. The hydrogen-uncharged sample shows the micro-void coalescence failure mechanism, whereas hydrogen-assisted cracking of the alloy initiates from grain boundaries and slip bands caused by plasticity-mediated decohesion mechanism. Crystallographic analysis demonstrates that {110}//ND grains and {001}//ND-{111}//ND grain boundaries are vulnerable to hydrogen embrittlement.

Effect of cyclic plastic deformation on hydrogen diffusion behavior and embrittlement susceptibility of reeling-pipeline steel weldments

The hydrogen embrittlement (HE) susceptibility and hydrogen permeation behavior of reeling-pipeline welded joint with/without cyclic plastic deformation (CPD) were studied using the electrochemical hydrogen charging technique. Results indicated that the surface of welded joint emerged hydrogen-induced damage containing cracks and blisters. The degree of hydrogen-induced damage increased with the increase of hydrogen charging time and current density. When the hydrogen charging current density and time was 50 mA/cm2 and 4 h, respectively, the area ratio of hydrogen-induced damage of overall welded joint with CPD process was reduced from 6.61% to 2.28%, and the damage ratio of different sub-zones in welded joint was also decreased. The oxidized inclusions enriching Al–Mg–Ca elements acted as the initiation sites for hydrogen-induced damages. The effective diffusion coefficient of as-welded joint was 2.63 × 10−6 cm2/s, while that of welded joint with CPD showed a smaller value of 1.36 × 10−6 cm2/s. The welded joint with CPD process presented better resistance to HE, which was attributed to the increased density of hydrogen traps and the formation of dislocation cells to disperse hydrogen uniformly and reduce the possibility of local accumulation and recombination of diffusible hydrogen. Sub-zones in welded joint without CPD process were considerably more sensitive to hydrogen-induced damage, which indicated the important role of microstructure and dislocation density in HE mechanisms. The order of HE susceptibility from low to high was weld metal, base metal and heat affected zone.

Effect of hydrogen charging time on hydrogen blister and hydrogen-induced cracking of pure iron

Hydrogen blister (HB) and hydrogen-induced cracking (HIC) of pure iron at various charging times were investigated. The results show that an increase in charging time leads to the increased HB height/width and HIC length/depth, and a change in hydrogen damage morphology. Subsurface HIC initiates and propagates along the grain boundaries, which makes the surface bend outwards to form blister on blister features, suggesting grain boundary cracking-induced blister-blister interaction mechanism. Crystallographic analysis demonstrates that adjacent grain boundary oriented-{100}//ND and {110}//ND exhibits the highest susceptibility to HIC, which offers a pathway to design hydrogen-resistant structural steels through the control of grain boundary.

Effects of Hydrogen Diffusion on the Mechanical Properties of 2.25Cr1Mo0.25V Steel

With the rapid development of hydrogen related equipment, how to ensure the reliable operation of these equipment has been an important research topic. 2.25Cr1Mo0.25V steel has high strength, good resistance to hydrogen corrosion and low cost. So it becomes one of most used material for high temperature and high pressure hydrogen systems. In this paper, the glycerine gas gathering experiment, micro hardness test and dynamic tensile experiment were conducted to study the changes of the mechanical properties of 2.25Cr1Mo0.25V steel under varying hydrogen charging time. The relationship between the hydrogen content and material properties were also discussed in detail.

Hydrogen-assisted cracking in 2205 duplex stainless steel: Initiation, propagation and interaction with deformation-induced martensite

The present work evaluates hydrogen-assisted cracking in 2205 duplex stainless steel by performing electron backscatter diffraction (EBSD) on in-situ hydrogen charged tensile tested specimens. The hydrogen embrittlement sensitivity increases with the electrochemical hydrogen charging time. The hydrogen presence results in deformation-induced martensite formation in the austenite during in-situ tensile straining, which starts immediately after yielding. Hydrogen-assisted cracking starts at a later stage in the tensile test and the cracks mainly initiate in austenite. The deformation-induced martensite is not vulnerable for crack initiation, neither is its interface with the austenite matrix. The presence of hydrogen-assisted cracks depends on the strain level reached in the specimen and is therefore most pronounced in the necked region. Crack propagation occurs through austenite, ferrite and their interface and is mainly governed by strain fields. Finally, propagation also occurs by coalescence of several smaller cracks.

Effect of Surface Roughness on Hydrogen-Induced Blister Behavior in Pure Iron

The effect of surface roughness on hydrogen-induced blister behavior in pure iron was explored using optical microscopy and microcomputerized tomography. Hydrogen was introduced into the samples by electrochemical precharging methods with various hydrogen charging times. It is found that grinded surface exhibits higher roughness and compressive residual stress compared to those of polished surface. With increasing hydrogen charging time, hydrogen-induced blister height, blister width and blister area fraction increase, regardless of the grinded surface and polished surface. Further, hydrogen blister height and width of grinded surface are comparative to polished surface under the same hydrogen charging time. However, the blister area fraction and the number of blister on polished surface are considerably higher than the grinded surface, indicating that polished surface is more susceptible to the formation of blisters than that of grinded surface, both of surface and interior of the samples. This is dominantly rationalized in terms of the suppression effect of hydrogen invasion in grinded surfaces due to their higher residual compressive stress and higher dislocation density.

Hydrogen Concentration Distribution in 2.25Cr-1Mo-0.25V Steel under the Electrochemical Hydrogen Charging and Its Influence on the Mechanical Properties.

The deterioration of the mechanical properties of metal induced by hydrogen absorption threatens the safety of the equipment serviced in hydrogen environments. In this study, the hydrogen concentration distribution in 2.25Cr-1Mo-0.25V steel after hydrogen charging was analyzed following the hydrogen permeation and diffusion model. The diffusible hydrogen content in the 1-mm-thick specimen and its influence on the mechanical properties of the material were investigated by glycerol gas collecting test, static hydrogen charging tensile test, scanning electron microscopy (SEM) test, and microhardness test. The results indicate that the content of diffusible hydrogen tends to be the saturation state when the hydrogen charging time reaches 48 h. The simulation results suggest that the hydrogen concentration distribution can be effectively simulated by ABAQUS and the method can be used to analyze the hydrogen concentration in the material with complex structures or containing multiple microstructures. The influence of hydrogen on the mechanical properties is that the elongation of this material is reduced and the diffusible hydrogen will cause a decrease in the fracture toughness of the material, and thus hydrogen embrittlement (HE) will occur. Moreover, the Young’s modulus E and microhardness are increased due to hydrogen absorption, and the variation value is related to the hydrogen concentration introduced into the specimen.

Hydrogen embrittlement of X80 pipeline steel in H2S environment: Effect of hydrogen charging time, hydrogen-trapped state and hydrogen charging–releasing–recharging cycles

This study investigated the susceptibility of X80 pipeline steel to hydrogen embrittlement given different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles in H2S environment. The fracture strain of the steel samples decreased with increasing hydrogen pre-charging time; this steel degradation could almost be recovered after diffusible hydrogen was removed when the hydrogen pre-charging time was <8 d. However, unrecoverable degeneration occurred when the hydrogen pre-charging time extended to 16–30 d. Moreover, nanovoid formation meant that the hydrogen damage to the steel under intermittent hydrogen pre-charging–releasing–recharging conditions was more serious than that under continuous hydrogen pre-charging conditions. This study illustrated that the mechanical degradation of steel is inevitable in an H2S environment even if diffusible hydrogen is removed or visible hydrogen-induced cracking is neglected. Furthermore, the steel samples showed premature fractures and exhibited a hydrogen fatigue effect because the repeated entry and release of diffusible hydrogen promoted the formation of vacancies that aggregated into nanovoids. Our results provide valuable information on the mechanical degradation of steel in an H2S environment, regarding the change rules of steel mechanical properties under different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles.

Hydrogen embrittlement sensitivity of X100 pipeline steel under different pre-strain

In the present study, the influences of hydrogen on the mechanical properties as well as the pre-strain on the HE susceptibility of X100 pipeline steel were investigated by combining electrochemical hydrogen charging and tensile experiments. Both the yield and tensile strength decrease with the increasing hydrogen charging time no matter the values of pre-strain. When the charging time is 12 h, the yield strength and tensile strength was reduced by 3% and 9%, respectively. The longer the charging time, the stronger the HE damage of the steel. Besides, when the hydrogen charging time is same, HE sensitivity increases with the pre-strain values. When the charging time is 6 h, the HE sensitivity coefficient is 40.24% without pre-strain, and it increases to 49.26% with the pre-strain value increases to the 2%. The hydrogen effective diffusion coefficient reduces gradually with the increasing pre-strain values. The coefficient is 5.45 × 10−7 cm2/s without pre-strain and it reduces to 1.21 × 10−7 cm2/s with the pre-strain value increases to the 3%. When the hydrogen charging time is same, HE sensitivity increases with the pre-strain values.

Charpy Impact Properties of Hydrogen-Exposed 316L Stainless Steel at Ambient and Cryogenic Temperatures

316L stainless steel is a promising material candidate for a hydrogen containment system. However, when in contact with hydrogen, the material could be degraded by hydrogen embrittlement (HE). Moreover, the mechanism and the effect of HE on 316L stainless steel have not been clearly studied. This study investigated the effect of hydrogen exposure on the impact toughness of 316L stainless steel to understand the relation between hydrogen charging time and fracture toughness at ambient and cryogenic temperatures. In this study, 316L stainless steel specimens were exposed to hydrogen in different durations. Charpy V-notch (CVN) impact tests were conducted at ambient and low temperatures to study the effect of HE on the impact properties and fracture toughness of 316L stainless steel under the tested temperatures. Hydrogen analysis and scanning electron microscopy (SEM) were conducted to find the effect of charging time on the hydrogen concentration and surface morphology, respectively. The result indicated that exposure to hydrogen decreased the absorbed energy and ductility of 316L stainless steel at all tested temperatures but not much difference was found among the pre-charging times. Another academic insight is that low temperatures diminished the absorbed energy by lowering the ductility of 316L stainless steel.

Effect of static hydrogen charging on corrosion and hydrogen embrittlement of High strength steel

The corrosion and hydrogen embrittlement properties of 1000MPa grade high strength steel in sea water are studied by weightlessness test under the condition of cathode polarization and slow strain tensile test (SSRT) after static hydrogen filling . The fracture characteristics of the specimen are observed with SEM. The results show that the most positive cathodic protection potential of high strength steel in sea water is -780 mV. The tensile test shows that with the negative shift of the polarization potential and the increase of hydrogen charging time, the elongation and the shrinkage of the high strength steel decrease gradually. The fracture mode transforms from ductile to cleavage and intergranular fracture. It can be seen that the toughness of the material decreases and the hydrogen embrittlement sensitivity increases gradually. Especially, the effect of polarization potential on hydrogen embrittlement of materials is more obvious.

Fatigue properties by “self-heating” method: Application to orthodontic Ni-Ti wires after hydrogen charging

Ni-Ti superelastic alloys have been successfully used in orthodontic clinics thanks to their good biomechanical and biochemical behavior. However, during treatment, some orthodontic wires may break in the oral cavity. The susceptibility of these alloys to cyclic loadings and to hydrogen embrittlement is supposed to be main causes of these unexpected failures. This study presents a contribution to studying the effect of hydrogen, obtained after cathodically charging in 0.9% NaCl solution, on the fatigue behavior of Ni-Ti commercial orthodontic wires subjected to high-cycle fatigue. Fatigue tests were analyzed using self-heating method based on observing thermal effects under mechanical cyclic loading. The results obtained with self-heating approach imply that the increase in hydrogen charging time is connected with an increase in the mean stabilized temperature and a decrease in the fatigue life. Self-heating method allows a rapid prediction of the endurance limit with a good reproducibility of fatigue tests at high number of cycles. Furthermore, cyclic stress–induced transformations and conventional fatigue tests under strain control are considered in this work to investigate the effect of hydrogen on cyclic loading type and to acquire for a better understanding of the interaction between hydrogen and thermo-mechanical mechanisms in Ni-Ti alloys.

Low-Pressure and Low-Temperature Hydriding–Pulverization–Dehydriding Method for Producing Shape Memory Alloy Powders

Shape memory alloys (SMAs) are of high interest as active, adaptive “smart” materials for applications such as sensors and actuators due to their unique properties, including the shape memory effect and pseudoelasticity. Binary NiTi SMAs have shown the most desirable properties, and consequently have generated the most commercial success. A major challenge for SMAs, in particular, is their well-known compositional sensitivity. Therefore, it is critical to control the powder composition and morphology. In this study, a low-pressure, low-temperature hydriding–pulverization–dehydriding method for preparing well-controlled compositions, size, and size distributions of SMA powders from wires is presented. Starting with three different diameters of as-drawn martensitic NiTi SMA wires, pre-alloyed NiTi powders of various well-controlled sizes are produced by hydrogen charging the wires in a heated H3PO4 solution. After hydrogen charging for different charging times, the wires are pulverized and subsequently dehydrided. The wires and the resulting powders are characterized using scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction. The relationship between the wire diameter and powder size is investigated as a function of hydrogen charging time. The rate of diameter reduction after hydrogen charging of wire is also examined. Finally, the recovery behavior due to the shape memory effect is investigated after dehydriding.

Effects of charging conditions on the hydrogen related mechanical property degradation of a 3 Cr low alloyed steel

Abstract In this work, the susceptibility of a 3 Cr low alloyed steel to hydrogen degradation of its mechanical properties was investigated to simulate the outside pipeline environment condition by a series of electrochemical hydrogen permeation measurements, surface characterization and tensile tests. Results show that the amount of hydrogen charging into the 3 Cr low alloyed steel specimen is affected by the external charging conditions, such as the hydrogen charging time and charging current density. The diffusivity of hydrogen at room temperature in 3 Cr low alloyed steel has been determined as 2.87 × 10−8 cm2 × s−1. The reduction of ductility with charging time becomes obvious in the tensile experiments.

TiNi超弾性合金細線の強度に及ぼす環境の影響

In this study, the tensile behavior of TiNi super elastic alloy under various hydrogen environments was investigated by using thin wires with various diameters. Ductility and tensile strength of TiNi super elastic alloy which absorbed hydrogen decreased. At the same charging time, tensile strength decreased with decreasing wire diameter. Compared TiNi super elastic alloy with TiNi shape memory alloy, tensile strength of TiNi super elastic alloy is higher than that of TiNi shape memory alloy in spite of hydrogen charging times. However, there is little difference in growth behavior of brittle layer formed by hydrogen charging between TiNi super elastic alloy and TiNi shape memory alloy.

스테인리스 304L강의 수소장입시간에 대한 비파괴기법 적용

Embrittlement of material by hydrogen charging should be cleared for safety of storage vessel of hydrogen and components deal with hydrogen. A stainless steel is generally used as materials for hydrogen transportation and storage, and it has a big advantage of corrosion resistance due to nickel component in material. In this study, microscopic damage behavior of stainless steel according to the hydrogen charging time using nondestructive evaluation was studied. The surface of stainless steel became more brittle as the hydrogen charging time increased. The parameters of nondestructive evaluation were also changed with the embrittlement of stainless steel surface by hydrogen charging. Ultrasonic test, which is the most generalized nondestructive technique, was applied to evaluate the relationship between the ultrasonic wave and mechanical properties of stainless steel by hydrogen charging. The attenuation coefficient of ultrasonic wave was increased with hydrogen charging time because of surface embrittlement of stainless steel. In addition, acoustic emission test was also used to study the dynamic behavior of stainless steel experienced hydrogen charging. AE event at the hydrogen charged specimen was obviously decreased at the plastic zone of stress-strain curves, while the number of event for the specimen of hydrogen free was dramatically generated when compared with the specimens underwent hydrogen charging.