Hydrogen In Alloys Research Articles

The factors affecting the diffusion properties of hydrogen in palladium copper alloys: Ab initio study

The experiments showed that the addition of copper (Cu) in palladium (Pd) membrane reduces the permeability of hydrogen (H) in Pd, and the permeability of H in body-centered cubic (BCC) PdCu alloy is larger than that in face-centered cubic (FCC) PdCu alloy. The underlying reasons are still not well understood. In the present work, systematical ab initio calculations are carried out to investigate the factors affecting the diffusion properties of H in PdCu alloys. It is found that the lowest diffusion barrier of H with zero-point energy correction in BCC PdCu alloy (0.016 eV) is relatively low than that in FCC PdCu alloy (0.346 eV). The interactions among interstitial H atoms are significantly repulsive in BCC PdCu alloy, while it is attractive in FCC PdCu alloy. The results suggest that it is energetically favorable to form interstitial H cluster in FCC PdCu alloy rather than that in BCC PdCu alloy. The formation of interstitial H clusters impedes the fast movement of H in FCC PdCu alloy. The presence of intrinsic vacancy in FCC PdCu alloy further hinders the migration of H. It is found that the binding strength of vacancy with H in FCC PdCu alloy is much larger than that in BCC PdCu. The stronger the combination of H and vacancy, the greater the obstacle to the movement of H in PdCu alloy. All these results elucidate the experimental phenomena why H penetration ability in FCC PdCu alloy is weaker than that in BCC PdCu alloy.

Peculiarities of conventional HDDR process in (Nd,Pr)-Fe-B alloy powders under low hydrogen pressure

The relationship between the temperature of the start, peak and finish of conventional disproportionation and recombination, in hydrogen, reactions and the low starting hydrogen pressure of 10, 20, 30, 40, 50, 60, 70 and 80 kPa and maximum processing temperature of 950–1015 °C was studied by DTA and X-ray diffraction measurements for 10 g of (Nd,Pr)-Fe-B ferromagnetic powder batches. It was shown that the starting temperature of the disproportionation reaction increases when hydrogen pressure decreases. A similar dependence took place for finishing temperature of the disproportionation when pressure was in the range of 40–80 kPa. At a hydrogen pressure of 10–30 kPa, finishing temperature of the disproportionation decreased with decreasing of pressure. The temperature of the recombination reaction in hydrogen increased with increasing of the hydrogen pressure. The non-equilibrium pressure–composition–temperature schema with four zones for the (Nd,Pr)-Fe-B alloy–hydrogen system was built. The remnants of the (Nd,Pr)2Fe14B phase and disproportionation products – (Nd,Pr)H2±x, α-Fe and Fe2B were in zone I – zone of the disproportionation reaction and in zone II – interstitial zone. The recombined (Nd,Pr)2Fe14B phase, (Nd,Pr)H0–2±x, α-Fe and Fe2B phases were in the zone III – zone of the recombination reaction. And the (Nd,Pr)2Fe14B phase, recombined in hydrogen, existed in the zone IV – zone of the existence of (Nd,Pr)2Fe14B phase.

Modeling the thermodynamics of the FeTi hydrogenation under para-equilibrium: An ab-initio and experimental study

FeTi-based hydrides have recently re-attracted attention as stationary hydrogen storage materials due to favorable reversibility, good sorption kinetics and relatively low costs compared to alternative intermetallic hydrides. Employing the OpenCalphad software, the thermodynamics of the (FeTi)1−xHx (0 ≤x≤ 1) system were assessed as a key basis for modeling hydrogenation of FeTi-based alloys. New thermodynamic data were acquired from our experimental pressure-composition-isotherm (PCI) curves, as well as first-principles calculations utilizing density functional theory (DFT). The thermodynamic phase models were carefully selected based on critical analysis of literature information and ab-initio investigations. Key thermodynamic properties such as dissociation pressure, formation enthalpies and phase diagrams were calculated in good agreement to our performed experiments and literature-reported data. This work provides an initial perspective, which can be extended to account for higher-order thermodynamic assessments and subsequently enables the design of novel FeTi-based hydrides. In addition, the assessed thermodynamic data can serve as key inputs for kinetic models and hydride microstructure simulations.

Metal Hydrides with In Situ Built Electron/Ion Dual-Conductive Framework for Stable All-Solid-State Li-Ion Batteries.

Due to their high theoretical specific capacity, metal hydrides are considered to be one of the most promising anode material for all-solid-state Li-ion batteries. Their practical application suffers, however, from the poor cycling stability and sluggish kinetics. Herein, we report the in situ fabrication of MgH2 and Mg2NiH4 that are uniformly space-confined by inactive Nd2H5 frameworks with high Li-ion and electron conductivity through facile hydrogenation of single-phase Nd4Mg80Ni8 alloys. The formation of MgH2 and Mg2NiH4 nanocrystals could not only shorten Li-ion and electron diffusion pathways of the whole electrode but also relieve the induced stress upon volume changes. Additionally, the robust frameworks constructed by homogeneous distribution of inactive Nd2H5 based on a molecular level could effectively alleviate the volume expansion and phase separation of thus-confined MgH2 and Mg2NiH4. More importantly, it is theoretically and experimentally verified that the uniform distribution of Nd2H5, which is an electronic conductor with a Li-ion diffusion barrier that is much lower than that of MgH2 and Mg2NiH4, could further facilitate the electron and Li-ion transfer of MgH2 and Mg2NiH4. Consequently, the space-confined MgH2 and Mg2NiH4 deliver a reversible capacity of 997 mAh g-1 at 2038 mA g-1 after 100 cycles.

Hydrogen production from Al–Cu alloy using electric vehicle's waste DC motor coils

Electric vehicles are a viable alternative for internal combustion engine cars to overcome transportation problems due to high fossil fuel consumption and greenhouse gas emissions. Due to their direct current motor and battery technologies' technological development, they have become an efficient transportation option in the last decades. However, the rapid spread of electric vehicles will bring huge dump problems for the environment. Thus, policies related to the recycling of their components must be carried out. In this study, an Al–Cu alloy is developed from the waste direct current motor's Cu rotor coils and pure Al for hydrolysis reactions. Then, 2 wt%, 4 wt% and 6 wt% Cu are added to pure Al to observe different Cu addition to Al–Cu alloy's hydrogen production performance to varying temperatures like 40, 60, and 80 °C. In 40 °C, 6 wt% Cu added Al alloy has around two-fold higher hydrogen production than pure Al. Moreover, the hydrolysis reaction's activation energy is decreased from 81.56 to 35.5 kJ mol −1 in 6 wt% Cu added Al alloy. • Al–Cu alloy is developed from waste DC motor's Cu rotor coils and pure Al. • Activation energy is decreased from 81.56 to 35.5 kJ mol −1 in AlCu6 alloy. • In AlCu6 alloy, 0.17 ml s − 1 hydrogen generation rate is obtained at 40 °C. • Corr rate of the pure Al is changed from 28.78 to 86.56 ml g −1 min −1 by 6 wt% Cu addition.

Is hydrogen diffusion in amorphous metals non-Arrhenian?

Hydrogen diffusion is critical to the performance of metals for hydrogen storage as well as other important applications. As compared to its crystalline counterpart which follows the Arrhenius relation, hydrogen diffusion in amorphous metals sometimes are experimentally found to be non-Arrhenian. In this work we studied the diffusion of hydrogen in amorphous Pd-H and Zr-Cu-H alloys based on molecular dynamics simulations. Our simulations confirm Arrhenian diffusion behaviour for hydrogen in amorphous alloys, in contrast to previous computational studies which predict non-Arrhenian behaviour. We show that the simulated non-Arrhenian diffusion based on molecular dynamics could result from a systematic error related to too short simulation time. We also discussed the experimental non-Arrhenian behaviour of hydrogen diffusion within the framework of quantum tunneling and amorphous-amorphous phase transformations.

Optimisation of the hydrogen bake-out treatment in steels via Gaussian processes

The presence of hydrogen in structural alloys reduces their ductility, a phenomenon called hydrogen embrittlement. Bake-out heat treatments are employed during processing to allow hydrogen trapped in microstructural features to effuse from the samples, but the optimal times and temperatures depend on the kinetics of hydrogen diffusion in the material. In this work, Gaussian process surrogate models are employed to emulate the outputs of microstructure-sensitive diffusion differential equations in steel. Training the models by sequentially increasing the number of dimensions results in better performances and shorter training times. Two main approaches are developed: single output models with experimental design for the prediction of optimal bake-out times, and multi-output principal component analysis models for the prediction of hydrogen concentration evolution. A novel approach is implemented to shorten the training times of multi-trap models by exploiting the symmetry of the equations with respect to different kinds of traps. The resulting models pave the way for the implementation of Gaussian processes on more computationally expensive diffusion simulations for the optimisation of heat treatments and other applications.

Tensile property and microstructure assessment of hydrogen treated Ti-6Al-4V alloy

Temporary hydrogen alloying (THA) treatment was used to refine the coarse-grained microstructure of a Ti-6Al-4V alloy with the intention of modifying tensile strength and ductility. Microstructure evolution was characterised using X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results indicate that THA treatment does not refine the coarse network of prior beta grains, but it alters the coarse Widmanstätten microstructure by nucleating submicron beta grains within the individual lamellae. The modified microstructure increases ultimate tensile strength (UTS) in the order of 100 MPa. The dehydrogenation temperature affected tensile ductility. The lowest dehydrogenation temperature (675 °C) had the highest ductility loss, and increasing the dehydrogenation temperature recovered ductility until full ductility was recovered at 750 °C. The ductility loss was attributed to the embrittling effect of the hydrogen induced phase Ti3Al which remains in the microstructure even after hydrogen removal and only completely dissolves at 750 °C. The results demonstrate that THA treatment significantly alters the initial coarse-grained microstructure with concomitant improvement in strength, but that the promotion of Ti3Al precipitation can cause embrittlement unless the dehydrogenation treatment is controlled to optimise Ti3Al dissolution.

Hydrogen purification by Mg alloy hydrogen adsorbent

Hydrogen purification by Mg alloy hydrogen adsorbent

Quantitative probing of hydrogen environments in quasicrystals by high-resolution NMR spectroscopy

Metal-based quasicrystals with unique quasi-periodic atomic arrangements are known to store a large amount of hydrogen under reasonable pressure and temperature for practical application as energy storage materials. While details on the atomic environments around hydrogen are central to understanding their hydrogen-storage capacity, the experimental probing of hydrogen environments and direct estimation of hydrogen content in hydrogen-bearing metal compounds, including quasicrystals, remain the holy grail in metallurgy and materials science because of the lack of suitable spectroscopic probes of hydrogen in noncrystalline metal alloys. While 1H nuclear magnetic resonance (NMR) measurement under fast spinning has the potential to reveal the nature of bonding around hydrogen, applying NMR to these metallic compounds has been challenging. Here, we report the first 1H nuclear magnetic resonance (NMR) spectra of hydrogenated quasicrystals under fast sample spinning, revealing previously unknown details of the bonding environment and hydrogen content. The NMR spectra of TiZrNi quasicrystals show that the metal atoms in the first coordination shell of neutral hydrogen shift gradually from Zr to Ti to Ni with increasing hydrogen content. This trend accounts for Ni-induced increase in the hydrogen-storage capacity and the enhanced desorption kinetics observed near ambient conditions. The 1H peak maximum shifted linearly toward lower frequencies with increasing hydrogen content, highlighting the utility of fast-spinning NMR as a novel quantitative probe of hydrogenated quasicrystals. These results open a new window to access the nature of hydrogen and its content in diverse hydrogen-bearing energy materials based on metal alloys using high-resolution 1H NMR spectroscopy, providing improved prospects for the hydrogen economy.

Electron Microscope Studies of the 01Cr17Ni13Mo3 Austenitic Steel Structure after Cold Rolling Combined with Hydrogen Alloying with Varying Degrees of Deformation

In this paper, we consider the effect of cold rolling and hydrogen alloying on the formation of twin boundaries of the corrosion resistance of austenitic steel 01Cr17Ni13Mo3. Using the method of transmission electronic microscopy, microdiffraction patterns were obtained. The analysis of microdiffraction patterns indicates the formation of a developed grain-subgrain structure with small-angle and large-angle misorientation. The structure has a high dislocation density, deformation twins and localized shift bands. It was established that plastic deformation by flat rolling to ε = 90 % at room temperature does not contribute to the appearance of a noticeable amount of α' and ε-martensite. At the temperature of liquid nitrogen, the samples were found to form a small fraction of the α'-martensite phase. Such a small amount of martensite can contribute to steel strengthening, and a decrease in the rolling temperature will lead to an increase in the strength properties of steel. It was detected that the density of twin boundaries under the decrease in the rolling temperature but with the same intensity of hydrogen saturation is significantly higher. A noticeable reduction in the width of the twin lamellas was revealed.

Hydrogen Isotopes Permeation in Clean or Unoxidized FeCrAl Alloys: A Review

The US Department of Energy is working with fuel vendors to develop accident tolerant fuels (ATF) for the current fleet of light water reactors (LWRs). The ATF should be more resilient to loss of coolant accident scenarios and help extending the life of the operating LWRs. One of the proposed ATF concepts is to use iron-chromium-aluminum (FeCrAl) alloys for the cladding of the fuel. A concern in using ferritic FeCrAl is that this type of cladding may result in an increase in the concentration of tritium in the coolant. The objective of the current critical review is to collect and assess information from the literature regarding diffusion or permeation of hydrogen (H) and its isotopes deuterium (D) and Tritium (T) across industrial alloys (including FeCrAl) used or intended for the nuclear industry. Over a hundred years of data reviewed shows that the solubility of hydrogen in ferritic alloys is lower than in austenitic alloys but hydrogen permeates faster through a ferritic material than through austenitic materials. The tritium permeation rates in FeCrAl alloys are between those in austenitic stainless steels and in ferritic FeCr steels. The activation energy for hydrogen permeation is approximately 30 pct higher in the austenitic alloys compared with the ferritic (typically ∼ 50 kJ/mol in ferritic vs. ∼ 65 kJ/mol in the austenitic). None of the major elements in FeCrAl alloys react with hydrogen to form detrimental hydride phases. The effect of surface oxides on FeCrAl delaying hydrogen entrance into FeCrAl alloy is not part of this review.

Controlling Catalyst–Semiconductor Contacts: Interfacial Charge Separation in p-InP Photocathodes

Charge-carrier-selective interfaces between electrocatalyst particles and semiconductor light absorbers are critical for solar photochemistry, but controlling their properties is challenging. Using thin films and nanoparticle arrays of Pt hydrogen-evolution catalysts on p-InP (a high-performance photocathode material), along with macroscopic and nanoscopic electrical and chemical analysis, we show how hydrogen alloying, the pinch-off effect for nanoscale contacts, and the formation of a native surface oxides all play different roles in creating charge-carrier-selective junctions. The new insights can be broadly applied to photocathodes, photoanodes, and overall water-splitting systems to control charge-carrier selectivity and improve performance.

On the behavior of hydrogen in metal alloys

On the behavior of hydrogen in metal alloys

Hot-extrusion behavior of biodegradable Zn-Mg alloys

Magnesium, zinc and iron-based alloys are the potential candidates for biodegradable implant applications and the effect of secondary processing on the biodegradability of these materials is of interest and being studied extensively. The evolution of gaseous hydrogen in magnesium-based alloys and higher corrosion rate limits the usage of these alloys, whereas, on the other hand, iron alloy's corrosion rate is too slow and leaves bulky corrosion products. The corrosion rate of Zn is in between the Mg and Fe, make it a potential alternate material. In the present study, pure Zn and Zn-Mg alloys are cast to different weight proportions and subjected to hot extrusion at different temperatures viz: 100, 150, 200, 250 and 300 °C. No surface defects were observed during extrusion of Zn at all temperatures, whereas Zn-Mg alloys were found to exhibit surface cracks at all temperatures except 200 and 250 °C. The presence of longitudinal tensile stresses at the surface due to frictional forces and inappropriate temperatures resulted in the development of cracks. The extruded samples were found to have fine microstructure as observed through an optical microscope. The XRD studies revealed the presence of the Mg2Zn11phase. The hardness of Zn was observed to increase by 26% after hot-extrusion which was due to the extensive grain refinement during extrusion.

The hydrogen storage capacity of Al–Cu alloy with permeable alumina hydrogen permeation barrier (HPB) applied by plasma electrolytic oxidation (PEO)

The synchronous hydrogen permeable and environment protective PEO alumina hydrogen permeation barrier (HPB) coating was formed on aluminum - copper alloy hydrogen storage substrate with high sustainability and resilience at low temperatures and hydrogen desorption/absorption was characterized. The effects of tetragonal θ (Al2Cu) phase precipitation; formed and significantly increased within Al(Cu) matrix during standard T3 heat-treatment, on Al2CuH compound formation (with distorted tetragonal-based structure) and hydrogenation was analyzed. The decrease in permeation rate of PEO-HPBs was neglectable. The highly permeable barrier (with permeation resistance parameter near four) of alumina phases (α, γ) barely obstructed hydrogen inter-diffusion during hydrogenation/dehydrogenation steps and a hydrogen recovery of over 99% was achieved cyclic stability and long-term reversibility.

Just shake or stir. About the simplest solution for the activation and hydrogenation of an FeTi hydrogen storage alloy

Despite many years having passed since it was discovered, FeTi alloys remain one of the most important low-temperature hydrogen storage alloys due to its high capacity, characteristics and low price. However, the main technological issue is its initial activation, which is usually conducted at relatively high temperature and pressure. This paper is the first to show that the complicated process can be replaced by intense movement of the powder or even chunks of alloy under hydrogen pressure without any additional grinding media. The newly discovered process, named self-shearing reactive milling (SSRM), leads to the full hydrogenation of FeTi alloys. The wear of particles, which is caused by their movement, causes the exposure of a fresh active alloy surface that is active enough to absorb hydrogen without any thermal treatment or evacuation. The resultant material, despite simply being strongly stirred, evolves from large chunks to an extremally fine spongy structure containing particle with sizes of tens of nanometers that combine to form large agglomerates. This result is an enormous improvement for the potential use of FeTi alloys and all other AB-type alloys in commercial applications by extraordinarily simplifying hydrogen storage vessels, which will not have to withstand high-temperature and pressure activation.

A Binary Hyperbox Classifier Model for Hydrogen Storage in Metal Hydrides

Despite being recognized as a key component towards reducing global GHG emissions, many challenges remain throughout the hydrogen value chain. Hydrogen storage is one critical aspect, since proper storage is essential for its wide scale deployment. One storage option is the chemisorption of hydrogen in metals and intermetallic alloys (i.e., metal hydrides). This approach can potentially address issues on safety, infrastructure, and cost which currently hinder the transition toward a hydrogen economy. The only suitable method for determining appropriate hydrogen storage materials is through experimentation which is resource intensive. There are many parameters that can affect the hydrogen storage capacity of a material; databases on previously investigated materials can be used to narrow down future investigation to the most promising candidates. Machine learning (ML) techniques can be employed to determine how different properties predict for hydrogen storage capacity. ML can use previously compiled data to generate a classification model that can be utilized for determining and predicting a material's viability for hydrogen storage. This paper uses the hyperbox ML technique to generate interpretable decision rules to predict if a metal hydride is a good candidate for hydrogen storage. A case study which specifically focuses on complex and magnesium hydrides is used to demonstrate this approach. The generated decision model had a false positive rate of 22.0 % and false negative rate of 36.8 %.

Influence of hydrogen behaviors on tensile properties of equiatomic FeCrNiMnCo high-entropy alloy

This study reports the effect of hydrogen behaviors on the tensile properties of an equiatomic FeCrNiMnCo high-entropy alloy. We reveal that the hydrogen at the interfaces (including grain boundaries and twin boundaries, etc.) is the main factor affecting the mechanical properties of the materials. We found that hydrogen alloying with a proper concentration makes the alloy resistant to hydrogen embrittlement and improves the strength and ductility of the material. This beneficial effect is positively correlated with the hydrogen concentration at the interface of the alloy, with hydrogen promoting the formation of stacking faults / nanotwins, which are excessively compensatory to the surface cracks introduced by the hydrogen. The influence of hydrogen at the interface of 316NG stainless steel on the tensile behavior has also been discussed. Although hydrogen embrittlement occurred at the same hydrogen-charged conditions, the deterioration of the ductility of the deformed 316NG with a high hydrogen concentration at the interface was significantly reduced. AIMD simulation has been used to study the diffusion of interstitial hydrogen in the HEA and FeCrNi model alloy. It was found that the diffusion barrier and diffusion coefficient of hydrogen in the two alloys were very close at different temperatures.

Design and Stress Analysis of Metalhydride Pressure Vessel

The article describes the design and strength calculation of a low-pressure steel tank, which is used for storage of hydrogen in a metal alloy based on Ti and Zr. An external liquid heat exchanger is considered in the design of the metal hydride tank. Strength calculations were performed to verify the selected wall thickness of the vessel and the wall thickness of the selected bottom type according to STN EN 13322-2 standard for the implementation of a metal hydride tank in operating conditions.