Hydrogen Accumulation Research Articles

The application of Monte Carlo modelling to quantify in situ hydrogen and associated element production in the deep subsurface

The subsurface production, accumulation, and cycling of hydrogen (H2), and cogenetic elements such as sulfate (SO42-) and the noble gases (e.g., 4He, 40Ar) remains a critical area of research in the 21st century. Understanding how these elements generate, migrate, and accumulate is essential in terms of developing hydrogen as an alternative low-carbon energy source and as a basis for helium exploration which is urgently needed to meet global demand of this gas used in medical, industrial, and research fields. Beyond this, understanding the subsurface cycles of these compounds is key for investigating chemosynthetically-driven habitability models with relevance to the subsurface biosphere and the search for life beyond Earth. The challenge is that to evaluate each of these critical element cycles requires quantification and accurate estimates of production rates. The natural variability and intersectional nature of the critical parameters controlling production for different settings (local estimates), and for the planet as a whole (global estimates) are complex. To address this, we propose for the first time a Monte Carlo based approach which is capable of simultaneously incorporating both random and normally distributed ranges for all input parameters. This approach is capable of combining these through deterministic calculations to determine both the most probable production rates for these elements for any given system as well as defining upper and lowermost production rates as a function of probability and the most critical variables. This approach, which is applied to the Kidd Creek Observatory to demonstrate its efficacy, represents the next-generation of models which are needed to effectively incorporate the variability inherent to natural systems and to accurately model H2, 4He, 40Ar, SO42- production on Earth and beyond.

Reduction of Residual Stresses in Cold Drawn Pearlitic Steel by a Soft Secondary Wire Diameter Reduction

In this paper, the effects of the skin pass technique on the residual stress and plastic strain fields generated in cold drawn pearlitic steel wires are analyzed. The aim is to find out the optimal conditions to be used in the design of a manufacturing process for obtaining more reliable structural components in terms of the main cause of failure: the hydrogen embrittlement (HE). To achieve this goal, diverse numerical simulations were performed by using finite elements (FE) and considering, on one hand, the first step of a real cold drawing chain, using (i) a conventional drawing die and (ii) modified drawing dies with different soft diameter reductions, and, on the other hand, numerical simulations by FE of the hydrogen diffusion assisted by stress and strain states to estimate the hydrogen distributions. Obtained results revealed the secondary reduction degree as a key parameter in the die design for reducing the drawing-induced residual stress. According to the results, low values of the reduction ratio cause radial distributions of residual stress with significant reductions at both the wire core and at the wire surface. In addition, the hydrogen accumulation at the prospective damage zone (near the wire surface) given by FE simulations is lower in the wires drawn with modified drawing dies including a skin pass zone.

Reactive oxygen species affect the potential for mineralization processes in permeable intertidal flats

Intertidal permeable sediments are crucial sites of organic matter remineralization. These sediments likely have a large capacity to produce reactive oxygen species (ROS) because of shifting oxic-anoxic interfaces and intense iron-sulfur cycling. Here, we show that high concentrations of the ROS hydrogen peroxide are present in intertidal sediments using microsensors, and chemiluminescent analysis on extracted porewater. We furthermore investigate the effect of ROS on potential rates of microbial degradation processes in intertidal surface sediments after transient oxygenation, using slurries that transitioned from oxic to anoxic conditions. Enzymatic removal of ROS strongly increases rates of aerobic respiration, sulfate reduction and hydrogen accumulation. We conclude that ROS are formed in sediments, and subsequently moderate microbial mineralization process rates. Although sulfate reduction is completely inhibited in the oxic period, it resumes immediately upon anoxia. This study demonstrates the strong effects of ROS and transient oxygenation on the biogeochemistry of intertidal sediments.

Effects in air-exposed corn silage of medium chain fatty acids on select spoilage microbes, zoonotic pathogens, and in vitro rumen fermentation

Medium chain fatty acid (MCFA) treatment (0.75% C6, hexanoic; C8, octanoic; C10, decanoic; or equal proportion mixtures of C6:C8:C10:C12 or C8:C10/g; C12 = dodecanoic acid) of aerobically-exposed corn silage on spoilage and pathogenic microbes and rumen fermentation were evaluated in vitro. After 24 h aerobic incubation (37 °C), microbial enumeration revealed 3 log10 colony-forming units (CFU)/g fewer (P = 0.03) wild-type yeast and molds in C8:C10-treated silage than controls. Compared with controls, wild-type enterococci decreased (P < 0.01) in all treatments except the C6:C8:C10:C12 mixture; lactic acid bacteria were decreased (P < 0.01) in all treatments except C6 and the C6:C8:C10:C12 mixture. Total aerobes and inoculated Staphylococcus aureus or Listeria monocytogenes were unaffected by treatment (P > 0.05). Anaerobic incubation (24 h at 39 °C) of ruminal fluid (10 mL) with 0.02 g overnight air-exposed MCFA-treated corn silage revealed higher hydrogen accumulations (P = 0.03) with the C8:C10 mixture than controls. Methane, acetate, propionate, butyrate, or estimates of fermented hexose were unaffected. Acetate:propionate ratios were higher (P < 0.01) and fermentation efficiencies were marginally lower (P < 0.01) with C8- or C8:C10-treated silage than controls. Further research is warranted to optimize treatments to target unwanted microbes without adversely affecting beneficial microbes.

Structural, optical and electrical characterizations of Mg/Ti/Ni multilayer thin films deposited by DC magnetron sputtering for hydrogen storage

Magnesium (Mg) based alloys are the most promising hydrogen storage and fuel cell alloys due to their high hydrogen content. In the present work, multilayer thin films (Mg/Ti/Ni) were prepared using direct current (DC) magnetron sputtering method. Multilayered Mg/Ti/Ni thin films were investigated by analyzing the data of different characterizations such as surface, structural, optical and electrical. Uniformity of the deposited thin films was analyzed by Field Emission Scanning Electron Microscope (FE-SEM) and Energy Dispersive Spectrometry (EDS) confirmed the presence of elemental composition. X-ray Diffractometer (XRD) was used to analyze structural characteristics of annealed thin films before and after hydrogenation. The variation in optical absorption and band gap has been observed, with the hydrogenation of thin film and having a larger band gap (3.27 eV) as compared to annealed thin films (2.81 eV). The semiconducting behavior of films is revealed by current voltage (I–V) characteristics of the films, and conductivity reduces after annealing and hydrogenation i.e. from 6.36 to 1.41 kΩ−1cm−1. Furthermore, Hall mobility of annealed without hydrogenated and annealed with hydrogenated thin film was improved (in the order of 103) as compared with as-deposited film. Improvement certainly helps the movement of hydrogen particularly after hydrogenation, the accumulation of hydrogen, particularly at the thin film's interface, obstructs the flow of electrons, resulting in a decrease in thin film conductivity. As a result, multilayer Mg/Ti/NI thin films are the good choice in the consideration for solid state hydrogen storage purpose.

Theoretical and experimental research of hydrogen storage properties of Mg and Mg-Al hydrides

In this work, we studied the effect of aluminum atoms addition on the properties of hydrogen accumulation and desorption in magnesium hydride. Using ab initio calculations and experimental methods, the role of alloying magnesium with aluminum was determined. The hydrogen content in the Mg and Mg–10 at%Al coatings was 1.8 wt% and 4.5 wt%, respectively. For the Mg–10 at%Al coating, the peak temperature of hydrogen desorption was about 425 °C, 17 °C lower than that for the Mg coating. The desorption rate for the Mg coating and Mg–10 at%Al coating was 3 × 10−14 mol(H2)/cm2 s and 31 × 10−14 mol(H2)/cm2 s, respectively. Compared with the Mg coating, the higher hydrogen content in the Mg–10 at%Al coating with the faster hydrogen desorption is related to the energetically more favorable Al-doped Mg system than the pure Mg system with H at the distance from Al at low hydrogen concentrations. The lower hydrogen desorption temperature of the Mg–10 at%Al coating is confirmed to be the consequence of the weakened MgH bond by the doped Al atom due to the higher electronegativity of the Al atom than that of the Mg atom. In addition, the aluminum binding energy decreases more significantly with the hydrogen concentration increase for hydrogen near Al atom than for hydrogen at a distance.

Dependence of the thermophysical properties of alloys of the Fe - Cr - Al - Si system on the composition and temperature

Pressurized water reactors (PWR, VVER, EPR, CAP) are currently the backbone of the world's nuclear power industry. The fuel in this type of power plants is uranium dioxide pellets enclosed in a sealed zirconium shell. Loss Of Coolant Accident (LOCA) emergencies can cause partial or complete destruction of zirconium claddings and accumulation of hydrogen in the reactor pressure vessel and reactor building. This is due to the so-called steam-zirconium reaction: an exothermic process of zirconium oxidation in an atmosphere of saturated water vapor at temperatures above 900 &deg;C. The products of this reaction are hydrogen and brittle zirconium oxide, which collapses under the action of its own weight and the weight of the fuel column. Fuel for pressurized water nuclear power reactors that is resistant to a loss of coolant accident is the subject of research around the world. One of the ways of implementation is the use of alloys of the Fe &ndash; Cr &ndash; Al system as a fuel element cladding material, since they have high corrosion resistance in water. The work is devoted to the determination of the coefficient of linear thermal expansion (CLTE), specific heat capacity, thermal conductivity and the influence of composition on them for Fe &ndash; Cr &ndash; Al &ndash; Si alloys in the temperature range of 200&ndash;1000 &deg;C. New data on the dependence of the thermophysical characteristics of alloys of the Fe &ndash; Cr &ndash; Al &ndash; Si system on temperature and chromium concentration have been obtained. It is shown that the CLTE, specific heat capacity and thermal conductivity weakly depend on the chromium content in the studied concentration range, the main contribution of alloying elements is made by the position of the Curie.

Innovative Design of Residual Stress and Strain Distributions for Analyzing the Hydrogen Embrittlement Phenomenon in Metallic Materials.

Round-notched samples are commonly used for testing the susceptibility to hydrogen embrittlement (HE) of metallic materials. Hydrogen diffusion is influenced by the stress and strain states generated during testing. This state causes hydrogen-assisted micro-damage leading to failure that is due to HE. In this study, it is assumed that hydrogen diffusion can be controlled by modifying such residual stress and strain fields. Thus, the selection of the notch geometry to be used in the experiments becomes a key task. In this paper, different HE behaviors are analyzed in terms of the stress and strain fields obtained under diverse loading conditions (un-preloaded and preloaded causing residual stress and strains) in different notch geometries (shallow notches and deep notches). To achieve this goal, two uncoupled finite element (FE) simulations were carried out: (i) a simulation by FE of the loading sequences applied in the notched geometries for revealing the stress and strain states and (ii) a simulation of hydrogen diffusion assisted by stress and strain, for estimating the hydrogen distributions. According to results, hydrogen accumulation in shallow notches is heavily localized close to the wire surface, whereas for deep notches, hydrogen is more uniformly distributed. The residual stress and plastic strains generated by the applied preload localize maximum hydrogen concentration at deeper points than un-preloaded cases. As results, four different scenarios are established for estimating "a la carte" the HE susceptibility of pearlitic steels just combining two notch depths and the residual stress and strain caused by a preload.

On the Use of Multi-Step Dies for Improving the Performance against Hydrogen Embrittlement of Cold Drawn Prestressing Steel Wires.

The main cause of in-service failure of cold drawn wires in aggressive environments is hydrogen embrittlement (HE). The non-uniform plastic strains and residual stresses generated after cold drawing play a significant role in the matter of HE susceptibility of prestressing steels. In this paper, a new and innovative design of the drawing scheme is developed, geared towards the reduction in both manufacturing-induced residual stresses and plastic strains. To achieve this goal, three innovative cold drawing chains (consisting in diverse multi-step dies where multiple diameter reductions are progressively carried out in a single die) are numerically simulated by the finite element (FE) method. From the residual stress and plastic strain fields revealed from FE numerical simulations, hydrogen accumulation for diverse times of exposure is obtained by means of FE simulations of the hydrogen diffusion assisted by stress and strains. Thus, an estimation of the HE susceptibility of the cold drawn wires after each process was obtained. Results reveal that cold drawn wire using multi-step dies exhibits lower stress and strain states nearby the wire surface. This reduction causes a decrease in the hydrogen concentration at the prospective damage zones, thereby improving the performance of the prestressing steel wires in hydrogenating environments promoting HE. Thus, the optimal wire drawing process design is carried out using special dies with several reductions per die.

Effect of the loading mode and temperature on hydrogen embrittlement behavior of 15Cr for steam turbine last stage blade steel

The hydrogen embrittlement of 15Cr martensitic stainless steel, for steam turbine last stage blades, was systematically studied by using slow strain rate tensile (SSRT) test and constant loading tensile (CLT) test at room temperature and 80 °C to simulate the service conditions. It was shown that, despite the lower hydrogen concentration absorbed during SSRT, the hydrogen-induced fracture strength of 15Cr steel for SSRT was lower than the threshold fracture strength for CLT. This was due to the remarkable enhancement in local hydrogen concentration due to the transportation of hydrogen by mobile dislocation during SSRT. In addition, although the higher hydrogen concentration was absorbed during SSRT at 80 °C, the hydrogen embrittlement susceptibility of 15Cr steel for SSRT at 80 °C was lower than that at room temperature, because the degree of local hydrogen accumulation decreased at a higher temperature.

Critical verification of the effective diffusion concept

Knowing the hydrogen distribution c(x,t) and local hydrogen concentration gradients grad(c) in ferritic steel components is crucial with respect to hydrogen embrittlement. Basically, hydrogen is absorbed from corrosive or gaseous environments via the surface and diffuses through interstitial lattice sites into bulk. Although, the lattice diffusion coefficient DL∼0.01mm2/s is in the order of magnitude of those for well-annealed pure iron, trapping sites in the microstructure retard the long-range chemical diffusion jL=−Dchem(c)grad(c), causing local hydrogen accumulation in near surface regions in limited time. Considering pure ferritic crystals without trapping sites in the microstructure, the limited characteristic diffusion depth xc∼Defft is proportional to the square root of the effective diffusion coefficient Deff and of time t. Effective diffusion coefficients are measured independently for hydrogen using the electrochemical permeation technique. For pure crystals, the effective diffusion coefficient is constant at given temperature and allows accurate calculations of the diffusion depths. However, with trapping sites in the microstructure the effective diffusion coefficient is not a material property anymore and becomes dependent on the hydrogen charging conditions. In the present work, the theory of hydrogen bulk diffusion is used to verify the concept of effective diffusion. For that purpose, the generalized bulk diffusion equation was solved numerically by using the finite difference method (FDM). The implementation was checked using analytical solutions and a comprehensive convergence study was done to avoid mesh and time dependency of the results. It is shown that effective diffusion coefficients can vary by magnitudes depending on the sub-surface lattice concentration. This limits the application of the effective diffusion concept and also the calculation of the characteristic diffusion depth.

Structure Effect on the Diffusion and Accumulation of Hydrogen in the Zr–1Nb Alloy

Structure Effect on the Diffusion and Accumulation of Hydrogen in the Zr–1Nb Alloy

Insights into the role of chitosan in hydrogen production by dark fermentation of waste activated sludge

Chitosan is widely used as a dewatering flocculant, but whether it affects hydrogen production from sludge anaerobic fermentation is unclear. This study aimed to elucidate the role of chitosan in the dark fermentation of waste activated sludge for hydrogen production. The results showed that chitosan had a negative effect on hydrogen production from sludge. Chitosan at 30 g/kg total suspended solids reduced hydrogen accumulation by 56.70 ± 1.22 % from 3.94 ± 0.12 to 1.71 ± 0.10 mL/g volatile suspended solids. Chitosan hindered the solubilization of sludge by flocculation, which reduced the available substrate for anaerobic fermentation. In addition, chitosan interfered with the electron transport system by reducing cytochrome C and caused lipid peroxidation by inducing reactive oxygen species, thereby inhibiting the activity of enzymes involved in anaerobic fermentation. Hydrogen production was reduced because hydrogen-producing processes (i.e., hydrolysis, acidification, and acetification) were inhibited more strongly than hydrogen-consuming processes (i.e., methanogenesis, sulfate reduction, and homoacetogenesis). Furthermore, chitosan enriched the abundance of Spirochaetaceae sp. and Holophagaceae sp., which occupied the survival space of hydrogen-producing microorganisms. This study reveals the potential impact of chitosan on hydrogen production in dark fermentation of sludge and provide direct evidence that chitosan triggers oxidative stress in anaerobic fermentation.

Characterization of the flow rate on lab-on-a-disc by a low-powered electrolysis pump for wireless-controlled automation of bioanalytical assays

Pumping mechanism in centrifugal microfluidic platforms enable liquid delivery against the unidirectional centrifugal force. Electrolysis pumping is a method that relies on pneumatic pressure generated by the accumulation of oxygen and hydrogen to propel liquids towards the CD center. Previously, we presented a wirelessly controlled electrolysis (EL) pump with 3D structure to optimize CD space for multiple pump integration. However, the performance of EL pump for low power ranges, and its usage in a real-life application have not been yet demonstrated. In this study, we present the analysis of the EL pump performance over a rotational speed range from 600 to 1500 RPM at low electrical power rates of up to 45 mW. The liquid pumping rate was studied theoretically and compared with the experimental data. The EL pump presented a consistent flow rate of 70–410 nL/s, showing a robust and predictable actuation for small volume delivery. As a first real-life application, we presented the isolation of a specific volume of supernatant liquid after sedimentation of yeast. A theoretical model predicted a period time of 135 s needed to pump 40 µL of supernatant. In our experimental set-up we observed a volume of 43 µL moved in the same amount of time which makes a very good match with the predicted value. As a second real-time application, we presented a centrifugal microfluidic design with multiple wirelessly controlled EL pumps to automate a peptide microarray-based immunoassay for the detection of influenza hemagglutinin antibody.

New insights into mechanism of emerging pollutant polybrominated diphenyl ether inhibiting sludge dark fermentation

Polybrominated diphenyl ethers (PBDEs), derived from electronics, furniture, etc., are detected with high level in excess sludge (ES). In this work, the influence of PBDEs on ES dark fermentation (ESDF) hydrogen production and the related key mechanisms were explored. The result shows PBDEs exposure reduced hydrogen production, and hydrogen accumulation decreased from 17.6 mL/g in blank to 12.3 mL/g with 12.0 mg/Kg PBDEs. PBDEs induced the reactive oxygen species production, which directly led to cell inactivation and reduced hydrogen production. Furthermore, PBDEs decreased ES disintegration, hydrolysis, acidification and homoacetogenic processes and inhibited the activities of enzymes related to hydrogen production. PBDEs also affected the diversity and richness of microbial communities in dark fermentation systems, especially high doses of PBDEs reduced the relative abundance of microorganisms associated with hydrogen production. In conclusion, PBDEs reduce hydrogen generation from ES.

Improvement of resistance against hydrogen embrittlement by controlling carbon segregation at prior austenite grain boundary in 3Mn-0.2C martensitic steels

This study challenged to improve the resistance against hydrogen embrittlement by increasing the concentration of carbon segregated at prior austenite grain boundary (PAGB), XPAGB, in low-carbon martensitic steels. The specimens with/without carbon segregation treatment (Non-seg and Seg specimens, respectively) had almost the same microstructure, other than higher XPAGB in the Seg specimen. While the uncharged Non-seg and Seg specimens exhibited similar mechanical properties, the maximum stress of the hydrogen-charged specimen was much higher in the Seg specimen than that in the Non-seg specimen even when diffusible hydrogen contents were almost the same. In addition, the fraction of intergranular fracture surface was much smaller in the Seg specimen. Based on these results, we conclude that the segregated carbon suppressed the accumulation of hydrogen around PAGB by site competition and increased cohesive energy of PAGB, leading to the significantly improved resistance against hydrogen-related intergranular fracture.

Effect of hydrogen accumulation on θ' precipitates on the shear strength of Al-Cu alloys

We investigate the effect of accumulation of H atoms on θ' strengthening precipitates in Al-Cu alloy. A relationship is established between the H accumulation and decrease in shear strength of alloy depending on the H content in precipitates of second phase. We use the previously proposed multiscale approach combining molecular dynamics (MD), continuum modeling and discrete dislocation dynamics (DDD). H atoms are located inside precipitate and at interphase boundaries. Energetically preferable places of H accumulation near and inside θ' phase in Al-Cu alloy are revealed. It is shown that the H accumulation on θ' leads to a decrease in precipitate shear resistance and causes the change in the dislocation-precipitate interaction mechanism from the Orowan loop formation to the cutting of the inclusion. The H accumulation on precipitates causes an increase in the threshold stress for the dislocation nucleation on the inclusion. The mechanism of softening of inclusions associated with a change from looping to cutting is transferred to the DDD level. The DDD results demonstrate that H charging of Al-Cu alloy can substantially decrease its shear strength. For high strength alloys with small precipitate size and/or inter-precipitate distance and with the yield stress above about 460 MPa, the reduction of strength can reach 10–25%.

A Promising Energy Storage System Based on High-Capacity Metal Hydrides

In this paper, based on the study of hydrogen accumulation in the electrodes of nickel–cadmium batteries, a high-capacity hydrogen storage system (HSS) is proposed. It has been experimentally proven that hydrogen accumulates in the electrodes of nickel–cadmium batteries in large quantities over the course of their operation. It has been shown that hydrogen accumulates in metal–ceramic matrices of sintered oxide–nickel electrodes in the form of metal hydrides. The gravimetric capacity of the nickel matrix is 20.3 wt% and the volumetric capacity is 406 kg m−3. The obtained gravimetric capacities for metal–ceramic matrices exceed almost four times the criteria for onboard hydrogen storage systems established by the US Department of Energy (DOE), as well as previously obtained results for any reversible hydrogen accumulation materials. In addition, in our previous papers, it was proved that if we use thermal runaway for the desorption of hydrogen from metal hydrides then the kinetic and thermodynamic criteria established by the US DOE may be significantly exceeded. Thus, within the framework of the proposed HSS, using the electrochemical method of hydrogen accumulation and the thermal runaway process, one can not only achieve all of the criteria established by the US DOE for HSS but also significantly exceed them.

Hydrogen-induced delayed fracture behaviour of V+Nb-microalloyed high-strength bolt steel with internal and environmental hydrogen

Hydrogen-induced delayed fracture (HIDF) behaviour of a V+Nb microalloyed 1300-GPa-grade high-strength bolt steel was explored by slow strain rate tensile (SSRT) tests under pre-hydrogen-charging (internal hydrogen) and dynamic hydrogen-charging (environmental hydrogen) conditions. The tested steel exhibited much lower HIDF resistance in the condition of environmental hydrogen than that of internal hydrogen, which is primarily due to the difference in hydrogen diffusion and accumulation characteristics and the hydrogen trapping effect of MC carbides. Therefore, for applications of high-strength bolt steels based primarily on the designing strategy of hydrogen trapping, it is extremely important to prevent environmental hydrogen entry in service.

Natural Hydrogen: A New Source of Carbon-Free and Renewable Energy That Can Compete With Hydrocarbons

Natural Hydrogen: A New Source of Carbon-Free and Renewable Energy That Can Compete With Hydrocarbons