Range Of Hydrogen Concentrations Research Articles

Fast prediction of the melting of FeH[formula omitted] in planetary interiors

FeHx is a crucial mineral in geophysics, but its melting properties remain poorly understood at high pressures. In this Short Communication, we introduce a simple analytical model to access the solid–liquid boundary of FeHx with minimal time and cost. Inspired by the work-heat equivalence principle, our model allows geophysicists to effectively exploit available ab initio resources to directly deduce the melting temperature of FeHx from its equation of state. The obtained results agree quantitatively with cutting-edge atomistic simulations throughout a wide range of hydrogen content and hydrostatic pressure. Therefore, our analyses would have implications for elucidating the internal dynamics of rocky worlds within and beyond our Solar System.

Wheatstone Bridge MEMS Hydrogen Sensor with ppb-Level Detection Limit Based on the Palladium-Gold Alloy.

On some occasions, such as new energy clinics, monitoring the trace hydrogen at the ppb level is necessary. The traditional resistive hydrogen sensors based on the Pd alloys are very difficult to realize such an extremely low detection limit. To achieve a detection limit at the ppb level and also ensure good stability, a MEMS hydrogen sensor was designed in a suspended Wheatstone bridge structure, with all four resistive arms defined on a sputtered Pd-Au alloy thin film. For the Wheatstone bridge sensor, absolute response (Ra) and relative response (Rs) are defined to describe the sensitivity of the sensor, and the effect of annealing temperature on baseline drift is investigated using the baseline zero drift parameter (DBZD). By testing the sensors across a hydrogen concentration range of 20 ppb to 3 v/v%, the optimal annealing temperature (250 °C) and operating temperature (60 °C) were identified. Under these conditions, the sensor exhibited a detection limit as low as 20 ppb with a power consumption of only 4.6 mW. At the same time, the response and recovery times of the sensor were 6 and 19 s, respectively, toward 3 v/v% hydrogen. After testing over a 100-day period, Ra fluctuated only 0.0026%, indicating that the hydrogen sensor had good long-term stability for low-concentration detection. More results also showed that the sensor has good repeatability, selectivity, and humidity resistance. With the wide measurement range (20 ppb to 3 v/v%), the sensor has the potential to meet hydrogen detection requirements in multiple scenarios.

Bioenergetic characterization of hyperthermophilic archaean Methanocaldococcus sp. FS406-22.

Hyperthermophilic archaean Methanocaldococcus sp. FS406-22 (hereafter FS406) is a hydrogenotrophic methanogen isolated from a deep-sea hydrothermal vent. To better understand the energetic requirements of hydrogen oxidation under extreme conditions, the thermodynamic characterization of FS406 incubations is necessary and notably underexplored. In this work, we quantified the bioenergetics of FS406 incubations at a range of temperatures (65, 76, and 85℃) and hydrogen concentrations (1.1, 1.4, and 2.1mm). The biomass yields (C-mol of biomass per mol of H2 consumed) ranged from 0.02 to 0.19. Growth rates ranged from 0.4 to 1.5h-1. Gibbs energies of incubation based on macrochemical equations of cell growth ranged from kJ/C-mol to kJ/C-mol. Enthalpies of incubation determined from calorimetric measurements ranged from kJ/C-mol to kJ/C-mol. FS406 growth rates were most comparable to hyperthermophilic methanogen Methanocaldococcus jannaschii. Maintenance energy calculations from the thermodynamic parameters of FS406 and previously determined heterotrophic methanogen data revealed that temperature is a primary determinant rather than an electron donor. This work provides new insights into the thermodynamic underpinnings of a hyperthermophilic hydrothermal vent methanogen and helps to better constrain the energetic requirements of life in extreme environments.

Advancing Hydrogen Sensing for Sustainable Aviation: A Metal Hydride Coated TFBG Optical Fibre Hydrogen Sensor

The aviation industry is undergoing a significant shift toward sustainability, with hydrogen emerging as a promising green fuel to reduce carbon emissions due to its high gravimetric energy density and clean combustion exhaust compared to traditional aviation fuels. However, realizing hydrogen's aviation potential requires advanced sensors to ensure safety and efficiency in challenging environments, particularly for monitoring hydrogen near high-temperature engines and cryogenic storage tanks. Fibre optic sensors offer an exceptional advantage in these demanding conditions due to their capacity to operate in harsh environments, their small size, immunity to electromagnetic interference, spark-free operation, and remote sensing capabilities. Metal hydrides are prominent sensing materials studied for hydrogen sensing, especially palladium (Pd). Nonetheless, existing literature pertaining to Pd-coated fiber optic sensors for hydrogen detection has brought to light concerns regarding response hysteresis, stability, and linearity of Pd hydrogen sensors, calling for innovative solutions. In response to these challenges, our research introduces an innovative fibre optic hydrogen sensor, introducing tantalum (Ta) based metal hydrides as the sensing material. The sensor's construction involved the deposition of a nanometer-thick Ta thin film onto the surface of a tilted fibre Bragg grating (TFBG) using a magnetron sputtering technique. The sensing mechanism relies on the modulation of optical constants of the Ta thin film in response to even minute hydrogen concentrations, culminating in spectral changes in the transmission spectrum of the TFBG. In this proof of concept work, changes in both amplitude and the centre wavelength of cladding resonances of the TFBG transmission spectrum were observed in the hydrogen concentration range from 0.01% to 4% at room temperature. These initial findings underscore the substantial potential of our approach in developing highly sensitive and robust fibre-optic hydrogen sensors tailored specifically for hydrogen-powered aviation.

Hydride-Induced Responses in the Mechanical Behavior of Zircaloy-4 Sheets

This study aimed to investigate the impact of hydrogen content, up to 1217 ppm, on the mechanical properties of Zircaloy-4, with a particular focus on the formation and impact of hydrides. Tensile specimens were tested across a range of temperatures and hydrogen concentrations. The results revealed a pronounced ductile-to-brittle transition associated with hydride formation. When the hydrogen content in the specimens ranged between 700 and 850 ppm, a ductile-to-brittle transition was observed at temperatures of 25 °C, 50 °C, and 75 °C. At 25 °C, the ultimate tensile strength (UTS) of Zircaloy-4 linearly increased as the hydrogen concentration rose from 0 to 1217 ppm H. However, at higher temperatures, the behavior of UTS became more complex, especially in the hydrogen concentration ranges of 500–850 ppm H. Elongation (EL) in the hydrided specimens was affected by both temperature and hydrogen concentration. As hydrogen concentration increased, there was a noticeable decline in uniform EL, while non-uniform EL showed even more significant reductions. Scanning electron microscopy (SEM) analysis of the fracture surfaces revealed that quasi-cleavage features became evident when the hydrogen content reached 850 ppm H, across all tested temperatures. These findings not only provide a quantitative assessment of the safety implications of Zircaloy-4 in nuclear reactor applications but also highlight the importance of the hydrogen charging process and mechanical testing in understanding its mechanical behavior.

Ab initio study of the structure and properties of amorphous silicon hydride from accelerated molecular dynamics simulations

This paper presents a large-scale ab initio simulation study of amorphous silicon hydride (a-Si1-xHx) with an emphasis on the structure and properties of the material across a range of hydrogen concentration by combining accelerated molecular dynamics (MD) simulations with first-principles density-functional calculations. The accelerated MD scheme relied on classical metadynamics, which enabled the development of 2500+ high-quality structural models of a-Si1-xHx, with system sizes ranging from 150 to 6000 atoms and hydrogen concentrations vary from 6 to 20 at.%. The resulting amorphous networks were found to be completely free from any coordination defects and that they all exhibited a pristine band-gap in their electronic spectrum. The microstructural properties of hydrogen distributions were examined with an emphasis on the presence of isolated and clustered environments of hydrogen atoms. The results were compared with experimental data obtained from X-ray diffraction, infrared spectroscopy and nuclear magnetic resonance studies.

Effect of the variation of oxygen concentration on the laminar burning velocities of hydrogen-enriched methane flames

The combustion properties of hydrogen-containing fuel mixtures and the effect of the variation of the oxygen content of the oxidizer are at the center of recent research interest. Laminar burning velocity measurements with varied oxygen content can help in the validation of reaction mechanisms for better simulations of combustion systems using exhaust gas recirculation (EGR) or oxygen-enriched atmosphere. Such measurements were carried out in hydrogen-enriched methane−air flames using the heat flux method with higher accuracy and a wider range of initial oxygen and hydrogen concentrations compared to the similar studies in the literature. The mole fractions of the hydrogen and oxygen contents of the initial fuel and oxidizer mixtures were varied between xH2 = 0 and 0.20, and xO2 = 0.14 and 0.23, respectively. The initial gas temperature and pressure were 298 K and 1 bar, respectively. It is demonstrated that the increase of combustion rate by the hydrogen enrichment can be compensated with the decrease of the oxygen content. This compensating effect was investigated in detail in a wide range of equivalence ratio (φ). The experimental data were simulated with 11 widely used methane combustion reaction mechanisms. The prediction accuracies of the mechanisms at lean and rich equivalence ratios were significantly different and the important reaction steps were identified using sensitivity analysis for three mechanisms. Mechanisms POLIMI-2014 and Caltech-2015 gave the best overall predictions.

Hydrogen-induced microstructure optimization and mechanical properties enhancement of forged (TiB + TiC)/Ti6Al4V

This study investigates the impact of hydrogen on the mechanical properties and microstructure of forged titanium matrix composites (TMCs) reinforced with 2.5 vol% TiB and 2.5 vol% TiC. Melt hydrogenation technology was used to fabricate the TMCs with different hydrogen contents, which were then forged at 880 °C. Microstructural analysis revealed that hydrogen accelerated atomic diffusion, resulting in an approximate network microstructure. Hydrogen also promoted dynamic recrystallization during forging, leading to grain refinement and reduced dislocation density. Room temperature tensile tests showed that hydrogen significantly improved the strength and ductility of the forged TMCs within a certain range of hydrogen content. The greatest improvement was observed in the forged TMCs with a hydrogen content of 7.87 × 10−2 wt%, which exhibited a 10.48% increase in yield strength and a 31.36% increase in ductility relative to those without hydrogen. The effects of hydrogenation on crack propagation mechanisms are also discussed in detail. Overall, these findings provide valuable insights into the strengthening and toughening of forged titanium matrix composites through hydrogenation.

Preparation and Hydrogen-Sensitive Property of WO3/Graphene/Pd Ternary Composite

Hydrogen (H2) is a renewable energy source that has the potential to reduce greenhouse gas emissions. However, H2 is also highly flammable and explosive, requiring sensitive and safe sensors for its detection. This work presents the synthesis and characterization of WO3/graphene binary and WO3/graphene/Pd (WG-Pd) ternary nanocomposites with varying graphene and Pd contents using the microwave-assisted hydrothermal method. The excellent catalytic efficacy of Pd nanoparticles facilitated the disintegration of hydrogen molecules into hydrogen atoms with heightened activity, consequently improving the gas-sensing properties of the material. Furthermore, the incorporation of graphene, possessing high conductivity, serves to augment the mobility of charge carriers within the ternary materials, thereby expediting the response/recovery rates of gas sensors. Both graphene and Pd nanoparticles, with work functions distinct from WO3, engender the formation of a heterojunction at the interface of these diverse materials. This enhances the efficacy of electron–hole pair separation and further amplifies the gas-sensing performance of the ternary materials. Consequently, the WG-Pd based sensors exhibited the best gas-sensing performance when compared to anther materials, such as a wide range of hydrogen concentrations (0.05–4 vol.%), a short response time and a good selectivity below 100 °C, even at room temperature. This result indicates that WG-Pd ternary materials are a promising room-temperature hydrogen-sensing materials for H2 detection.

High Sensitivity Hydrogen Sensors Based on Optical Micro/Nanofiber Couplers Working at the Dispersion Turning Point

The safe utilization of hydrogen as a clean fuel and industry material requires the reliable detection of gas leakage. Thus, hydrogen sensors with high sensitivity and fast response are in urgent demand. Optical hydrogen sensors are especially attractive among various hydrogen detection techniques because of their intrinsic safety. Herein, a high-sensitivity hydrogen gas sensor is proposed based on optical micro/nanofiber couplers working at the dispersion turning point. The Pd coatings used were deposited on the waist region by magnetron sputtering. Due to the phase transition of palladium in the presence of hydrogen, intensity changes in the optical transmission of the devices are produced. It is demonstrated that the proposed platform provides high sensitivity, good repeatability, and selectivity, together with a fast response time for hydrogen detection below the explosive concentration. The response and recovery times are ~20 and ~28 seconds, respectively. The detected hydrogen concentration range is 0.1-1.5% (in volume). The detection limit of this sensor is below 0.1%.

Passive electrochemical hydrogen recombiner for hydrogen safety systems: prospects

This paper presents the concept of a passive electrochemical hydrogen recombiner (PEHR). The reaction energy of the recombination of hydrogen and oxygen is used as a source of electrical energy according to the operating principle for hydrogen fuel cells to establish forced circulation of the hydrogen mixture as an alternative to natural circulation (as is not utilized in conventional passive autocatalytic hydrogen recombiners currently used in nuclear power plants (NPPs)). The proposed concept of applying the physical operation principles of a PEHR based on a fuel cell simultaneously increases both productivity in terms of recombined hydrogen and the concentration threshold of flameless operation (the ‘ignition’ limit). Thus, it is possible to reliably ensure the hydrogen explosion safety of NPPs under all conditions, including beyond-design accidents. An experimental setup was assembled to test a laboratory sample of a membrane electrode assembly (MEA) at various hydrogen concentrations near the catalytic surfaces of the electrodes, and the corresponding current–voltage characteristics were recorded. The simplest MEA based on the Advent P1100W PBI membrane demonstrated stable performance (delivery of electrical power) over a wide range of hydrogen concentrations.

Flame propagation characteristics of premixed hydrogen–air deflagration with low concentration in a pipeline

This study used a visualized explosion propagation experimental system to investigate the flame propagation and hydroxyl (OH·) spectral radiation characteristics of hydrogen deflagration at the hydrogen concentration range of 7–17 vol%. The experimental results indicated that maximum flame propagation velocity, maximum explosion pressure, maximum flame temperature, and maximum relative spectral intensity of OH· gradually increased with hydrogen concentration. When concentration increased from 13 vol% to 17 vol%, the time to reach the maximum flame propagation velocity, the formation time of tulip flame, and the duration of the spectral radiation signal of OH· decreased by 52.9%, 55.6%, and 48.2%, respectively. In addition, flame propagation velocity oscillated when the tulip flame appeared, and maximum explosion pressure appeared later than the maximum temperature. Maximum flame propagation velocity, maximum explosion pressure, and maximum flame temperature positively correlated with maximum relative spectral intensity in the reaction system. These findings may serve as an essential reference for the safe and effective use of hydrogen and the research and development of radical targeted explosion suppressants.

Chemical inhibition of hydrogen-air explosions: Literature review, simulations and experiments

This paper summarises the first results from the joint industry project (JIP) ‘Risk-reduction for hydrogen installations by partial suppression of explosions’ (HyRISE). The main objective of the project is to develop fundamental knowledge that can support the development of practical solutions for mitigating hydrogen explosions in congested and confined environments by means of active systems for chemical inhibition. The aim is not to extinguish the incipient flame, but rather to lower the reactivity of the fuel-air mixture prior to ignition, and thereby reduce the consequences of an accidental explosion to a tolerable level. The paper consists of three parts: a review of previous work on chemical inhibition of premixed hydrogen-air flames, simulations with the chemical kinetics software Cantera, and experiments conducted in a 20-litre explosion vessel. The results demonstrate that chemical inhibition can be effective for hydrogen-air mixtures. However, it remains to develop efficient inhibitors and practical systems that can be implemented in industrial facilities, with satisfactory performance over a wide range of hydrogen concentrations.

Study on the role of Pd and ZrVFe hydrogen storage alloy in Pd/ ZrVFe catalyst for hydrogen elimination performance

Hydrogen energy has been considered to be one of the most potential clean energy, but its widespread availability is limited by hydrogen safety. Herein, a hydrogen-oxygen combination catalyst is designed based on a ZrVFe hydrogen storage alloy loaded with Pd, which exhibits excellent hydrogen elimination capability at low temperature, broad hydrogen concentration range and other complex working environments. The results show that the activity of the Pd/ZrVFe catalyst is dependent on the Pd loadings, and the 2 wt% Pd/ZrVFe catalyst can initiate the hydrogen-oxygen elimination reaction rapidly at ∼30 °C under above 2 vol% hydrogen concentration and 2 L min−1 inlet gas flow with a 96% hydrogen elimination efficiency. The Pd/ZrVFe catalyst has excellent hydrogen elimination performance at 2–20 vol% hydrogen concentration, especially at hydrogen concentration above 10%, the hydrogen elimination efficiency can reach more than 99%, and the highest hydrogen elimination rate is as high as 182.6 mL min−1· g−1. In addition, the Pd/ZrVFe catalyst is almost unaffected by irradiation and aerosol poisoning, and this catalyst provided better resistance to iodine vapor poisoning compared to other catalysts. This work opens a new window for addressing hydrogen safety issues.

AAO-Assisted Nanoporous Platinum Films for Hydrogen Sensor Application

The effects of the porosity and the thickness on the ability of hydrogen sensing is demonstrated through a comparison of compact and nanoporous platinum film sensors. The synthesis of anodic aluminum oxide (AAO) nanotubes with an average pore diameter of less than 100 nm served as the template for the fabrication of nanoporous Pt films using an anodization method. This was achieved by applying a voltage of 40 V in 0.4 M of a phosphoric acid solution at 20 °C. To compare the film and nanoporous Pt, layers of approximately 3 nm and 20 nm were coated on both glass substrates and AAO templates using a sputtering technique. FESEM images monitored the formation of nanoporosity by observing the Pt layers covering the upper edges of the AAO nanotubes. Despite their low thickness and the poor long-range order, the EDX and XRD measurements confirmed and uncovered the crystalline properties of the Pt films by comparing the bare and the Pt deposited AAO templates. The nanoporous Pt and Pt thin film sensors were tested in the hydrogen concentration range between 10–50,000 ppm H2 at room temperature, 50 °C, 100 °C and 150 °C. The results reveal that nanoporous Pt performed higher sensitivity than the Pt thin film and the surface scattering phenomenon can express the hydrogen sensing mechanism of the Pt sensors.

Direct hydrogen quantification in high-pressure metal hydrides

High-pressure metal hydride (MH) research evolved into a thriving field within condensed matter physics following the realization of metallic compounds showing phonon mediated near room-temperature superconductivity. However, severe limitations in determining the chemical formula of the reaction products, especially with regards to their hydrogen content, impedes a deep understanding of the synthesized phases and can lead to significantly erroneous conclusions. Here, we present a way to directly access the hydrogen content of MH solids synthesized at high pressures in (laser-heated) diamond anvil cells using nuclear magnetic resonance spectroscopy. We show that this method can be used to investigate MH compounds with a wide range of hydrogen content, from MH x with x = 0.15 (CuH0.15) to x ≲ 6.4 (H6±0.4S5).

Revealing the role of hydrogen content on the mechanical behavior and cracking mechanisms of Zircaloy-4 under strain

The mechanical property of zirconium-alloy reactor cladding materials inevitably degrades because of hydrogen absorption and hydride precipitation. In this study, mechanical behavior and delayed hydrogen cracking (DHC) mechanisms of Zircaloy-4 alloys with a broad range of hydrogen contents were investigated. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and a universal testing machine were jointly employed for this purpose. Results showed that the mechanical property of the hydrogenated specimen not only depended on the size and orientation of hydride, but also was affected by the continuity degree of the load-bearing matrix. The relevant microstructural observation indicated that the lower continuity degree of the load-bearing matrix, the less ductility of Zircaloy-4. More importantly, hydride phase transformation from δ-ZrH 1.5 to γ-ZrH occurred around the crack tip and reduced the local strain, while twinning just appeared at the crack bridging sites in the higher hydrogen-content specimens for changing the crystal orientation and mitigating the local stress concentration. Both those effects are expected to be potential mechanisms of the reappearing yield phenomenon because they are closely linked to dislocation movement. Additionally, based on the combination effect of crack blunting of γ-ZrH and the strain accommodation of twinning, the trend of crack propagation is delayed locally as expected. • The hydride phase transformation and twinning phenomenon around cracks were analyzed using EBSD. • The continuity of the load-bearing matrix profoundly influenced the mechanical properties of hydrided zircaloy-4. • The appearance and disappearance of yield-suppression phenomenon in hydrided zircaloy-4 were investigated. • Both γ-ZrH and twins are beneficial to delay the localized crack propagation.

Neutron diffraction study of concentration phases transition in the TiC0.50Hy alloy

The study belongs to the field of hydrogen materials science. A neutron diffraction study of titanium carbohydride TiC0.50Hy was carried out in the range of hydrogen concentration у = 0.50 ÷ 0.60. It is shown that high-temperature titanium carbohydride TiC0·50H0.50 of equiatomic composition has a face-centered cubic lattice (sp. gr. Fm3¯m), where hydrogen atoms are located in tetrahedral interstices. It has been established that in this alloy in vacuum, the phenomenon of hydrogen thermal emission is observed - complete removal of hydrogen with preservation of the FCC lattice of the TiС0.50 interstitial alloy. For the first time in the Ti–C–H system, a first-order concentration phase transition FCC (sp. gr. Fm3¯m) → HCP (sp. gr. Pm3¯1) in TiC0.50Hy carbohydride at a hydrogen concentration y > 0.50 was discovered without changing the octahedral environment of carbon atoms and tetrahedral the surroundings of hydrogen atoms by Ti atoms. The HCP phase in vacuum is heat-resistant at temperatures T < 600 K. The unit cell volume of the hcp phase is two times smaller than the unit cell volume of the FCC phases TiC0.50Hy and TiH2 of equiatomic composition. The results of studying the fcc phase of the equiatomic composition of TiC0·50H0.50 can be used to prepare a high-temperature hydrogen reservoir in hydrogen energy. The HCP phase can be used as a biological protective material in transport nuclear power plants and on nuclear submarines instead of titanium dihydride TiH2.

Influence of temperature and hydrogen content on the transverse mechanical properties of Zircaloy-4 fuel cladding

This paper presents the results of the investigation on the influence of hydrogen on the transverse mechanical properties of the Zircaloy-4 fuel cladding at various temperatures ranging from room temperature to 600οC. Data pertaining to the mechanical properties of the fuel cladding in the hoop direction are required for the analysis of high burn-up fuel behaviour under loss of coolant accident (LOCA) and reactivity initiated accident (RIA) conditions. Using the ring tension test method, the mechanical properties of the Zircaloy-4 fuel cladding in the transverse direction were evaluated as functions of hydrogen concentration and test temperature. The effect of hydrogen on the mechanical properties was observed to be marginal but the effect of temperature was significant in the investigated hydrogen concentration range (47–475 ppmw).

Reflective-Type High Sensitivity Optical Fiber Hydrogen Sensor Based On Enlarged Taper Cascaded With Tilted Fiber Grating

Highly sensitive reflective-type fiber hydrogen sensor based on an enlarged taper cascaded with a tilted fiber grating (TFBG) was proposed. Hydrogen-sensitive Au-Pd nanofilm was coated on the TFBG surface by magnetron sputtering means. By cascading an enlarged taper upstream to the TFBG, cladding modes and Ghost mode of the TFBG could be coupled into the core to form a reflective-type TFBG-based hydrogen sensor. As the hydrogen was absorbed by the Au-Pd nanofilm, the effective refractive index of the cladding of the TFBG will change accordingly, so as to the reflective spectra of the TFBG. The hydrogen concentration was obtained through the intensity changing of the ghost mode in the reflective spectra of TFBG. The proposed sensor showed a high sensitivity of 4.83 dB/% with a calculated LOD of 0.07% for the hydrogen concentration range from 0% to 0.7% at room temperature with the rapid response time of 26 s and recovery time of 40 s, respectively.