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• Mg film hydrogenation process was analyzed by ion beam and optical measurements. • IBA reveals a hydrogenation described by a MgH 2 front growing towards the substrate. • Ion beam measurements are supported by XRD, SEM and profilometry measurements. • H diffusion coefficient on the MgH 2 phase has been obtained. • Optical tracing of the hydrogenation is influenced by the Mg initial thickness. [Display omitted] Pd-capped nanocrystalline Mg films were prepared by electron beam evaporation and hydrogenated under isothermal conditions to investigate the hydrogen absorption process via ion beam techniques and in situ optical methods. Films were characterized by different techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA) provided a detailed compositional depth profile of the films during hydrogenation. Gas-solid reaction kinetics theory applied to ERDA data revealed a H absorption mechanism controlled by H diffusion. This rate-limiting step was also confirmed by XRD measurements. The diffusion coefficient (D) was also determined via RBS and ERDA, with a value of (1.1 ± 0.1) · 10 − 13 cm 2 /s at 140 ∘ C. Results confirm the validity of IBA to monitor the hydrogenation process and to extract the control mechanism of the process. The H kinetic information given by optical methods is strongly influenced by the optical absorption of the magnesium layer, revealing that thinner films are needed to extract further and reliable information from that technique. [ABSTRACT FROM AUTHOR]

In the present study, the hydrogen-absorption properties of the LaNi5 and the La0.7Ce0.1Ga0.3Ni5 compounds were determined and compared. This work is therefore divided into two parts: an experimental part that presents and discusses the kinetics and isotherms of hydrogen absorption in the two compounds at two different temperatures (298 K and 318 K). In addition, the temperature variations inside the hydride bed were determined. In the second section, the experimental isotherms were compared to a numerical model processed using statistical physics. Following that, thanks to the perfect agreement between the experimental data and the proposed model, the stereographic and energetic parameters associated with the hydrogen absorption reaction, such as the number of hydrogen atoms per receptor site (n1, n2), the densities of the sites (Nm1, Nm2), the half-saturation pressures (P1, P2) and the absorption energies (ΔE1, ΔE2) for each receptor site, were calculated. All of these parameters are acquired by making numerical adjustments to the experimental data. Thermodynamic functions, such as internal energy and Gibbs energy, which regulate the absorption process, were then identified using these parameters. For both compounds, all of the aforementioned were compared and discussed in relation to initial temperature and pressure. The results demonstrated that the hydrogen-storage properties in LaNi5 are enhanced by more than 30% of stored mass and kinetics when Ce and Ga are substituted at the La sites. [ABSTRACT FROM AUTHOR]

Pd-capped nanocrystalline Mg films were prepared by electron beam evaporation and hydrogenated under isothermal conditions to investigate the hydrogen absorption process via ion beam techniques and in situ optical methods. Films were characterized by different techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA) provided a detailed compositional depth profile of the films during hydrogenation. Gas-solid reaction kinetics theory applied to ERDA data revealed a H absorption mechanism controlled by H diffusion. This rate-limiting step was also confirmed by XRD measurements. The diffusion coefficient (D) was also determined via RBS and ERDA, with a value of (1.1±0.1)·10−13 cm2/s at 140 ∘C. Results confirm the validity of IBA to monitor the hydrogenation process and to extract the control mechanism of the process. The H kinetic information given by optical methods is strongly influenced by the optical absorption of the magnesium layer, revealing that thinner films are needed to extract further and reliable information from that technique.

Hydrogen absorption in transition metals has received enormous attention for applications such as the hydrogen storage, sensing and corrosion. In particular, the Pd‐H system is a simple and classical metal hydride system that serves as a platform for a deeper understanding of hydrogen behavior. In the past few years, Pd‐H has been reported as electrocatalyst in multiple reactions, whereas the impact of hydrogen absorption/desorption in electrocatalytic applications remains unclear. Therefore, in this concept, factors influencing the hydrogen adsorption/desorption of palladium in the gas phase, such as facet engineering, ligand effects, and alloying effects, are summarized. Subsequently, in the context of electrocatalysis, factors affecting electrochemical hydrogen adsorption/desorption are outlined. Particularly, prospects for the further investigation of electrochemical hydrogen adsorption/desorption in catalysis are discussed. [ABSTRACT FROM AUTHOR]

In this study, we investigate the effect of small amounts of zirconium alloying the medium-entropy alloy (TiVNb)85Cr15, a promising material for hydrogen storage. Alloys with 1, 4, and 7 at.% of Zr were prepared by arc melting and found to be multiphase, comprising at least three phases, indicating that Zr addition does not stabilize a single-phase solid solution. The dominant BCC phase (HEA1) is the primary hydrogen absorber, while the minor phases HEA2 and HEA3 play a crucial role in hydrogen absorption/desorption. Among the studied alloys, Zr4 (TiVNb)81Cr15Zr4 shows the highest hydrogen storage capacity, ease of activation, and reversibly retrievable hydrogen. This alloy can absorb hydrogen at room temperature without additional processing, with a reversible capacity of up to 0.74 wt.%, corresponding to hydrogen-to-metal ratio H/M = 0.46. The study emphasizes the significant role of minor elemental additions in alloy properties, stressing the importance of tailored compositions for hydrogen storage applications. It suggests a direction for further research in metal hydride alloys for effective and safe hydrogen storage. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen absorption in transition metals has received enormous attention for applications such as the hydrogen storage, sensing and corrosion. In particular, the Pd‐H system is a simple and classical metal hydride system that serves as a platform for a deeper understanding of hydrogen behavior. In the past few years, Pd‐H has been reported as electrocatalyst in multiple reactions, whereas the impact of hydrogen absorption/desorption in electrocatalytic applications remains unclear. Therefore, in this concept, factors influencing the hydrogen adsorption/desorption of palladium in the gas phase, such as facet engineering, ligand effects, and alloying effects, are summarized. Subsequently, in the context of electrocatalysis, factors affecting electrochemical hydrogen adsorption/desorption are outlined. Particularly, prospects for the further investigation of electrochemical hydrogen adsorption/desorption in catalysis are discussed.

A hydrogen permeable Nb43W5Ti27Co20Fe5 alloy membrane was designed and its microstructure and hydrogen transportation performances were systematically studied. W mainly dissolves into primary body-centered cubic (bcc)-(Nb) phases, while Fe is captured in eutectic structures. Substituting Nb with W leads to a substantial reduction in hydrogen solubility and substituting Co with Fe negligibly affects hydrogen solubility. The W and Fe substitutions contribute to an enhanced intrinsic hydrogen diffusion coefficient D∗. The designed Nb43W5Ti27Co20Fe5 alloy membrane exhibits lower hydrogen solubility and higher hydrogen permeability at temperatures below 623 K than that of the original Nb48Ti27Co25 alloy membrane. No hydrogen-induced failures were found for the designed Nb43W5Ti27Co20Fe5 alloy membrane during cooling to room temperature and under long-term hydrogen permeation at 673 K for 72 h, whereas the original alloy membrane failed at 444 K during cooling to room temperature and after 19 h during hydrogen permeation at 673 K. The designed Nb43W5Ti27Co20Fe5 alloy membrane exhibits high hydrogen permeability and strong resistance to hydrogen embrittlement.

In the present study, the hydrogen-absorption properties of the LaNi5 and the La0.7Ce0.1Ga0.3Ni5 compounds were determined and compared. This work is therefore divided into two parts: an experimental part that presents and discusses the kinetics and isotherms of hydrogen absorption in the two compounds at two different temperatures (298 K and 318 K). In addition, the temperature variations inside the hydride bed were determined. In the second section, the experimental isotherms were compared to a numerical model processed using statistical physics. Following that, thanks to the perfect agreement between the experimental data and the proposed model, the stereographic and energetic parameters associated with the hydrogen absorption reaction, such as the number of hydrogen atoms per receptor site (n1, n2), the densities of the sites (Nm1, Nm2), the half-saturation pressures (P1, P2) and the absorption energies (ΔE1, ΔE2) for each receptor site, were calculated. All of these parameters are acquired by making numerical adjustments to the experimental data. Thermodynamic functions, such as internal energy and Gibbs energy, which regulate the absorption process, were then identified using these parameters. For both compounds, all of the aforementioned were compared and discussed in relation to initial temperature and pressure. The results demonstrated that the hydrogen-storage properties in LaNi5 are enhanced by more than 30% of stored mass and kinetics when Ce and Ga are substituted at the La sites.

A hydride of Yb2Pd2Sn could be synthesized with approximately 2 H atoms per f.u. The hydrogenation leads to a volume expansion while preserving the tetragonal symmetry (P4/mbm). The lattice reaction is strongly anisotropic, and the 5% expansion in c is partly compensated by the 0.5% compression in a. The hydride is paramagnetic at least down to 0.5 K. Yb remains at or very close to the 3+ (4f13) state, as in Yb2Pd2Sn. Specific heat C/T vs. T shows an upturn existing already in Yb2Pd2Sn, but it is much more pronounced in the hydride (1.8 J/mol f.u. K2 for T → 0, i.e., more than twice higher than in its precursor). This is interpreted as lowering the Kondo temperature due to H bonding. [ABSTRACT FROM AUTHOR]

Considering the clean, renewable, and ecologically friendly characteristics of hydrogen gas, as well as its high energy density, hydrogen energy is thought to be the most potent contender to locally replace fossil fuels. The creation of a sustainable energy system is currently one of the critical industrial challenges, and electrocatalytic hydrogen evolution associated with appropriate safe storage techniques are key strategies to implement systems based on hydrogen technologies. The recent progress made possible through nanotechnology incorporation, either in terms of innovative methods of hydrogen storage or production methods, is a guarantee of future breakthroughs in energy sustainability. This manuscript addresses concisely and originally the importance of including nanotechnology in both green electroproduction of hydrogen and hydrogen storage in solid media. This work is mainly focused on these issues and eventually intends to change beliefs that hydrogen technologies are being imposed only for reasons of sustainability and not for the intrinsic value of the technology itself. Moreover, nanophysics and nano-engineering have the potential to significantly change the paradigm of conventional hydrogen technologies. [ABSTRACT FROM AUTHOR]

Substitution of Nb by W in Nb48Ti27Co25 dual phase hydrogen permeable alloy was carried out. The elemental W replacing Nb mainly dissolved into the primary body-centered cubic (bcc)-(Nb) phase to modify its composition and crystal lattice. The W alloying effect on hydrogen transportation was systematically discussed based on hydrogen chemical potentials and first principle calculations. The substitution of Nb by W reduced the hydrogen solubility, and led to an improved intrinsic hydrogen diffusion coefficient, especially at temperature below 573 K, which promoted the hydrogen permeation flux of Nb48Ti27Co25 alloy membrane at 523 K. According to the theoretical study based on density function theory of the Nb–W system, the reduced hydrogen solubility can be attributed to the weakened binding strength between hydrogen atoms and the bcc-(Nb) lattice and the reduced charge gained by hydrogen atoms after W substitution for Nb. In addition, the W occupying the Nb sublattice can change the diffusion path of hydrogen atoms in the bcc-(Nb) lattice, thereby reducing the diffusion energy barrier for high hydrogen diffusivity.

The hot forming process allows to produce safety-relevant structural components in the automotive industry with strengths of 1500 MPa and higher. Generally, high strengths make material sensitive to hydrogen embrittlement. The heat treatment in the hot forming process chain is a potential source of diffusible hydrogen for hot-dipped aluminum-silicon coated boron-manganese steels. In the present work, the influence of different process gases and furnace dwell times during the heat treatment was investigated. Humidified process gases such as synthetic air, nitrogen, oxygen and carbon dioxide were used. The results of the thermal desorption mass spectrometry (TDMS) revealed a more pronounced hydrogen uptake for nitrogen and carbon dioxide gas atmosphere than for synthetic air and oxygen. Furthermore, different material conditions were investigated regarding their sensitivity to hydrogen absorption. The flat-rolled material tends to suffer a higher hydrogen absorption compared to the reference material when using humidified process gases. Materials being pretreated with dry synthetic air point at a relation between the duration time of the pretreatment and the content of absorbed hydrogen.

In this study, we investigate the effect of small amounts of zirconium alloying the medium-entropy alloy (TiVNb)85Cr15, a promising material for hydrogen storage. Alloys with 1, 4, and 7 at.% of Zr were prepared by arc melting and found to be multiphase, comprising at least three phases, indicating that Zr addition does not stabilize a single-phase solid solution. The dominant BCC phase (HEA1) is the primary hydrogen absorber, while the minor phases HEA2 and HEA3 play a crucial role in hydrogen absorption/desorption. Among the studied alloys, Zr4 (TiVNb)81Cr15Zr4 shows the highest hydrogen storage capacity, ease of activation, and reversibly retrievable hydrogen. This alloy can absorb hydrogen at room temperature without additional processing, with a reversible capacity of up to 0.74 wt.%, corresponding to hydrogen-to-metal ratio H/M = 0.46. The study emphasizes the significant role of minor elemental additions in alloy properties, stressing the importance of tailored compositions for hydrogen storage applications. It suggests a direction for further research in metal hydride alloys for effective and safe hydrogen storage.

Thin layers (up to 1 µm) of Pd-Ir alloys were electrodeposited from aqueous, galvanic baths of PdCl2 and IrCl3 mixtures. The morphology of the electrodeposits was examined by means of scanning electron microscopy. The composition of alloys was determined with the use of energy-dispersive spectroscopy, atomic absorption spectrometry, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. For the studies of the electrochemical properties of alloys, cyclic voltammetry, chronoamperometry, and chronopotentiometry were used. It was found that Pd-Ir alloy electrodes were surface-enriched with Pd. Pd-Ir alloys subjected to different electrochemical treatment involving hydrogen sorption changed their surface state. The continuous hydrogen sorption enhanced the Ir ions' dissolution. The values of thermodynamic functions of hydrogen sorption in strong alkaline electrolytes were comparable with those in acidic electrolytes, whereas the kinetics of the process in alkaline medium was hindered. The miscibility gap in the Pd-Ir-H system vanished for the electrode containing ca. 93.7 at.% Pd. [ABSTRACT FROM AUTHOR]

The kinetic mechanism of hydrogen absorption of the AA6111 alloy melt in different melting environments, and the in-situ real-time observation of the oxide film structure during the hydrogen absorption process were studied. The results show that the hydrogen absorption process of the aluminum alloy melt is related to the melting environment and the oxide film on the melt surface. The hydrogen content in the melt increases with the extension of time when the melting environment humidity and temperature are constant. The initial hydrogen content is also higher and the hydrogen absorption capacity of the melt is larger when the melting temperature is constant with an increasing melting environment humidity. The oxide film will fold over on itself and become porous, due to the change in the structure of the melt surface during heating. The surface of the melt is similar to the double-oxide-film defect hydrogen absorption carrier, which leads to the aggravation of hydrogen absorption. Hydrogen absorption kinetic equations for the aluminum alloy melt under different melting environments are obtained based on the experimental results. [ABSTRACT FROM AUTHOR]

Coatings of metal specimens are known to have an impact on hydrogen gettering (hydrogen absorption). The coating can have one or more functions, such as enhancing gettering, preventing gettering and/or preventing oxidation of the metal substrate. It is known that contaminants and surface texture can impact hydrogen gettering/absorption performance, but has not previously been thoroughly explored. This study evaluated the role of different post-plating heat treatments of nickel-plated zircaloy-4 getters (NPGs) and the role of the heat treatments on gettering rates, surface composition and texture. Nickel plating is applied to prevent oxidation of the Zircaloy-4 surface and also enhances gettering. The nickel plating must be heat treated before desirable gettering can occur. Our NPG getters with historically known satisfying performance were pre-heat treated in air followed by activation heat treatment in a vacuum at a higher temperature. In this study, we were interested in finding out if both heat treatment steps were necessary to obtain a desirable gettering performance, or if one step could be omitted. XPS analysis showed that if the nickel surface is not heat treated before bonding the nickel to the zirconium in the activation step, there will be carbon contaminants on the surface, which significantly reduces gettering. We studied the texture of Zircaloy-4 using SEM/EBSD to compare NPGs with both heat treatment steps with NPGs that had no post-plating heat treatment to learn if the degree of cold work could be impacted by the heat treatment steps. We did not observe any differences in texture between them. We measured gettering rates of both pretreated and activated NPGs and NPGs that had been activated without first being pre-heat treated. We found that the NPGs without the first post-plating heating step had up to a seven times slower gettering rate and obtained higher plateau pressures due to the contaminated surface. Thus, the pre-heat treatment in air before activation is necessary to avoid slower gettering rates and higher plateau pressures. [ABSTRACT FROM AUTHOR]

Considerable fluctuations in the cathodic protection potential under the impact of stray currents lead to the occurrence of local corrosion on steel structures operated in soils and seawater. The potential fluctuations induced by both alternating and direct current sources can be simulated by cycling a square potential step. This paper covers the impact of sign-alternating cyclic polarization (SACP) on the general and local corrosion of carbon steel in 3.5% NaCl solution containing a borate buffer (pH 6.7) and without it. A decrease in the cathodic half-period potential (Ec) of SACP inhibited the general corrosion and accelerates the local corrosion of steel in both solutions, which was associated with an increase in the amount of hydrogen in the metal. Increasing the duration of the SACP cathodic half-period increased the pit density and total area at less negative Ec values. At more negative Ec values, an increase in the duration of cathodic polarization reduced the intensity of steel local corrosion in the unbuffered chloride solution. This effect is explained by blocking of the pit nucleation centers on the metal surface by a layer of steel dissolution products formed in the near-electrode electrolyte layer with a high pH. The combined body of data shows that hydrogen absorption by the metal determines the corrosion behavior of carbon steel under the impact of SACP in chloride solutions, which should be taken into account in the development of models of the corrosion of steel structures under the action of stray currents. [ABSTRACT FROM AUTHOR]

A hydride of Yb2Pd2Sn could be synthesized with approximately 2 H atoms per f.u. The hydrogenation leads to a volume expansion while preserving the tetragonal symmetry (P4/mbm). The lattice reaction is strongly anisotropic, and the 5% expansion in c is partly compensated by the 0.5% compression in a. The hydride is paramagnetic at least down to 0.5 K. Yb remains at or very close to the 3+ (4f13) state, as in Yb2Pd2Sn. Specific heat C/T vs. T shows an upturn existing already in Yb2Pd2Sn, but it is much more pronounced in the hydride (1.8 J/mol f.u. K2 for T → 0, i.e., more than twice higher than in its precursor). This is interpreted as lowering the Kondo temperature due to H bonding.

The hydrogen infrastructure involves hydrogen production, storage and delivery for utilization with clean energy applications. Hydrogen ingress into structural materials can be detrimental due to corrosion and embrittlement. To enable safe operation in applications that need protection from hydrogen isotopes, this review article summarizes most recent advances in materials design and performance characterization of barrier coatings to prevent hydrogen isotopes' absorption ingress and permeation. Barriers are crucial to prevent hydride formation and unwanted hydrogen effects to increase safety, materials' lifetime and reduce cost for applications within nuclear and renewable energy. The coating may be applied on a material that requires protection from hydrogen pick-up, transport and hydride formation in hydrogen storage containers, in pipelines, spent nuclear fuel storage or in nuclear reactors. While existing, commercial coatings that have been much in use may be satisfactory for various applications, it is desirable to evaluate whether alternative coating concepts can provide a greater resistance to hydrogen isotope permeation along with other improved properties, such as mechanical strength and thermal resistance. The information presented here is focusing on recent findings within the past 5–7 years of promising hydrogen barriers including oxides, nitrides, carbon, carbide, MAX-phases and metals and their mechanical strength, hydrogen pick-up, radiation resistance and coating manufacturing techniques. A brief introduction to hydrogen permeation is provided. Knowledge gaps were identified to provide guidance for material's research prospects. [ABSTRACT FROM AUTHOR]

Thin layers (up to 1 µm) of Pd-Ir alloys were electrodeposited from aqueous, galvanic baths of PdCl2 and IrCl3 mixtures. The morphology of the electrodeposits was examined by means of scanning electron microscopy. The composition of alloys was determined with the use of energy-dispersive spectroscopy, atomic absorption spectrometry, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. For the studies of the electrochemical properties of alloys, cyclic voltammetry, chronoamperometry, and chronopotentiometry were used. It was found that Pd-Ir alloy electrodes were surface-enriched with Pd. Pd-Ir alloys subjected to different electrochemical treatment involving hydrogen sorption changed their surface state. The continuous hydrogen sorption enhanced the Ir ions’ dissolution. The values of thermodynamic functions of hydrogen sorption in strong alkaline electrolytes were comparable with those in acidic electrolytes, whereas the kinetics of the process in alkaline medium was hindered. The miscibility gap in the Pd-Ir-H system vanished for the electrode containing ca. 93.7 at.% Pd.

The H contents and H embrittlement (HE) of Zn- and ZnNi-electrodeposited SCM435 bolts were quantitatively evaluated before and after baking. The Zn-coated bolt possessed higher H contents than the ZnNi-coated bolt in as-electrodeposited and baked states. H atoms were strongly trapped inside the coating layers. The Zn-coated bolt underwent flaking of coating layer during baking at temperatures above 200 °C due to H effusion through the brittle δ phase. The Zn-coated bolt exhibited no HE regardless of baking despite of its high H content due to no permeation of H into the steel substrate during electrodeposition and tensile deformation.

This paper focuses on nanoindentation and TOF-SIMS (time-of-flight secondary ion mass spectrometry) small-scale test methods in the study of hydrogen absorption and oxygenation behavior analysis of Zr-Sn-Nb oxidized at 650°C −1200 °C. The CSM (Continuous Stiffness Method) test demonstrates the hardness fluctuations caused by element proliferation in post-high temperature oxidation microstructures. The deformation resistance ability of typical microstructures is as follows: β-Zr layer > α-Zr(O) layer > ZrO 2 layer. In addition, hydrogen-induced softening occurred in steam-containing hydrogen conditions (H IT =2～3Gpa), compared to steam (H IT =5～16Gpa). The 1200℃ load-displacement curve demonstrates that the pop-in (or pop-out) effect exists in the Zr-Sn-Nb alloy, related to the influence of hydrogen charge, essentially to dislocation nucleation, winding, and movement. TOF-SIMS provides an effective method for small molecular chemical elements, such as H and O, while ZrO, ZrO 2 , ZrO 2 H, ZrO 3 H, OH, and O 2 ions also be found. Based on these results, this study also hypothesizes the OH- dominated oxidation reaction equation. • The nanoindentation and TOF-SIMS were used in the study of hydrogen absorption and oxygenation behavior analysis of Zr-Sn-Nb oxidized at 650℃-1200℃. • The oxidation atmosphere research focuses on steam and steam-containing hydrogen, the latter in verifying the effect of hydrogen molecules on the oxidation behavior of zirconium alloys. • The pop-in (or pop-out) effects of oxidized Zr-Sn-Nb alloys were speculatively discussed. • TOF-SIMS provides an effective method for small molecular chemical elements, such as H and O. • The mechanism of the oxidation reaction process led by OH roots is discussed. [ABSTRACT FROM AUTHOR]

Using metal hydride for hydrogen storage in stationary applications and for transportation is a promising technology due to its advantages of large hydrogen storage capacity, low pressure and low energy consumption. Combining the metal hydride reactor with PCM is expected to recover the heat generated during the hydrogen absorption and use it for hydrogen desorption, thus improving the energy efficiency of the system. This paper proposes a metal hydride reactor integrated with honeycomb fins and PCM to enhance heat transfer. Based on simulations, the results show that the achieved hydrogen storage capacity is 1.326 wt%, the gravimetric and volumetric storage densities are 0.411% and 14.76 kg of H 2 per m3, respectively, and the mean saturated rates are 1.222 × 10−3 g s−1 and 0.773 × 10−3 g s−1 for absorption and desorption processes. Compared with the reactor without fins, the mass and volume of the reactor using honeycomb fins are increased, resulting in a decrease in gravimetric and volumetric storage density, but a increase in reaction rate during hydrogen absorption and desorption processes. Based on this structure, we also propose a honeycomb fin reactor filled with sandwich PCM to further accelerate the heat transfer in the reaction process. Compare to the reactor with PCM only filled on the periphery of the honeycomb fins, the hydrogen absorption and desorption times are shortened by about 86.4% and 81.1%, respectively. In addition, different reactor structures are compared using multiple KPIs to provide relevant suggestions for the reactor optimization. The obtained research results can provide a reference for effective thermal management methods in MH storage systems. • A metal hydride reactor integrated with honeycomb fins and PCM was proposed. • The comparison of reactor without fins and the effects of fin size were studied. • The placement of PCM and MH was optimized. • Multiple KPIs were used to evaluate the hydrogen absorption and desorption processes. • The optimized reactor performed better than other forms of reactors. [ABSTRACT FROM AUTHOR]

Atmospheric corrosion is one of the major sources of hydrogen in a high-strength-steel product in service. Even low concentrations of absorbed hydrogen can cause a hydrogen embrittlement-related material degradation. The extent of atmospheric corrosion and thus the related hydrogen entry is highly dependent on the environmental parameters, such as the relative humidity. The present work focused on the hydrogen entry at low relative humidity, where atmospheric corrosion rates are expected to be low. Hydrogen insertion and distribution in CP1000 steel induced by corrosion under dried and rewetted single droplets of aqueous NaCl and MgCl2 solution were studied using the Scanning Kelvin Probe (SKP) and the resulting amounts of diffusible hydrogen were analyzed using thermal desorption mass spectrometry (TDMS). Corrosion product analyses were carried out with SEM/EDX, XRD, and Mössbauer spectroscopy. The results revealed the strong impact of salt type and concentration on the hydrogen entry into steel. The hygroscopic effect of MgCl2 and the formed corrosion products were responsible for the prolonged insertion of hydrogen into the steel even at very low levels of relative humidity. [ABSTRACT FROM AUTHOR]

The kinetic mechanism of hydrogen absorption of the AA6111 alloy melt in different melting environments, and the in-situ real-time observation of the oxide film structure during the hydrogen absorption process were studied. The results show that the hydrogen absorption process of the aluminum alloy melt is related to the melting environment and the oxide film on the melt surface. The hydrogen content in the melt increases with the extension of time when the melting environment humidity and temperature are constant. The initial hydrogen content is also higher and the hydrogen absorption capacity of the melt is larger when the melting temperature is constant with an increasing melting environment humidity. The oxide film will fold over on itself and become porous, due to the change in the structure of the melt surface during heating. The surface of the melt is similar to the double-oxide-film defect hydrogen absorption carrier, which leads to the aggravation of hydrogen absorption. Hydrogen absorption kinetic equations for the aluminum alloy melt under different melting environments are obtained based on the experimental results.

Coatings of metal specimens are known to have an impact on hydrogen gettering (hydrogen absorption). The coating can have one or more functions, such as enhancing gettering, preventing gettering and/or preventing oxidation of the metal substrate. It is known that contaminants and surface texture can impact hydrogen gettering/absorption performance, but has not previously been thoroughly explored. This study evaluated the role of different post-plating heat treatments of nickel-plated zircaloy-4 getters (NPGs) and the role of the heat treatments on gettering rates, surface composition and texture. Nickel plating is applied to prevent oxidation of the Zircaloy-4 surface and also enhances gettering. The nickel plating must be heat treated before desirable gettering can occur. Our NPG getters with historically known satisfying performance were pre-heat treated in air followed by activation heat treatment in a vacuum at a higher temperature. In this study, we were interested in finding out if both heat treatment steps were necessary to obtain a desirable gettering performance, or if one step could be omitted. XPS analysis showed that if the nickel surface is not heat treated before bonding the nickel to the zirconium in the activation step, there will be carbon contaminants on the surface, which significantly reduces gettering. We studied the texture of Zircaloy-4 using SEM/EBSD to compare NPGs with both heat treatment steps with NPGs that had no post-plating heat treatment to learn if the degree of cold work could be impacted by the heat treatment steps. We did not observe any differences in texture between them. We measured gettering rates of both pretreated and activated NPGs and NPGs that had been activated without first being pre-heat treated. We found that the NPGs without the first post-plating heating step had up to a seven times slower gettering rate and obtained higher plateau pressures due to the contaminated surface. Thus, the pre-heat treatment in air before activation is necessary to avoid slower gettering rates and higher plateau pressures.

Considerable fluctuations in the cathodic protection potential under the impact of stray currents lead to the occurrence of local corrosion on steel structures operated in soils and seawater. The potential fluctuations induced by both alternating and direct current sources can be simulated by cycling a square potential step. This paper covers the impact of sign-alternating cyclic polarization (SACP) on the general and local corrosion of carbon steel in 3.5% NaCl solution containing a borate buffer (pH 6.7) and without it. A decrease in the cathodic half-period potential (Ec) of SACP inhibited the general corrosion and accelerates the local corrosion of steel in both solutions, which was associated with an increase in the amount of hydrogen in the metal. Increasing the duration of the SACP cathodic half-period increased the pit density and total area at less negative Ec values. At more negative Ec values, an increase in the duration of cathodic polarization reduced the intensity of steel local corrosion in the unbuffered chloride solution. This effect is explained by blocking of the pit nucleation centers on the metal surface by a layer of steel dissolution products formed in the near-electrode electrolyte layer with a high pH. The combined body of data shows that hydrogen absorption by the metal determines the corrosion behavior of carbon steel under the impact of SACP in chloride solutions, which should be taken into account in the development of models of the corrosion of steel structures under the action of stray currents.

The hydrogen infrastructure involves hydrogen production, storage and delivery for utilization with clean energy applications. Hydrogen ingress into structural materials can be detrimental due to corrosion and embrittlement. To enable safe operation in applications that need protection from hydrogen isotopes, this review article summarizes most recent advances in materials design and performance characterization of barrier coatings to prevent hydrogen isotopes’ absorption ingress and permeation. Barriers are crucial to prevent hydride formation and unwanted hydrogen effects to increase safety, materials’ lifetime and reduce cost for applications within nuclear and renewable energy. The coating may be applied on a material that requires protection from hydrogen pick-up, transport and hydride formation in hydrogen storage containers, in pipelines, spent nuclear fuel storage or in nuclear reactors. While existing, commercial coatings that have been much in use may be satisfactory for various applications, it is desirable to evaluate whether alternative coating concepts can provide a greater resistance to hydrogen isotope permeation along with other improved properties, such as mechanical strength and thermal resistance. The information presented here is focusing on recent findings within the past 5–7 years of promising hydrogen barriers including oxides, nitrides, carbon, carbide, MAX-phases and metals and their mechanical strength, hydrogen pick-up, radiation resistance and coating manufacturing techniques. A brief introduction to hydrogen permeation is provided. Knowledge gaps were identified to provide guidance for material’s research prospects.

Hydrogen embrittlement is a common phenomenon in high-strength steels and presents a significant challenge in the research and development process. This study aims to analyze the mechanism of hydrogen embrittlement, investigate the causes of crack growth in steel, and conduct experiments at mesoscopic and microscopic scales to gain a deep understanding of the relationship between hydrogen embrittlement and defects in high-strength steels. The research includes a slow tensile test to study the shrinkage and ductility of X42 steel and 20# carburizing steel under air and hydrogen environments. Furthermore, fatigue testing is conducted to comparatively investigate the crack growth of CT specimens in nitrogen and hydrogen environments at different pressures. Additionally, impact testing is performed to examine the fracture of V-notched specimens in air and hydrogen at different pressures. The findings reveal that 20# carburizing steel exhibits better fracture toughness than X42 steel during the slow tensile process, and its hydrogen embrittlement sensitivity is lower. Moreover, the fatigue crack growth process of 20# carburizing steel is less affected by hydrogen embrittlement, resulting in better fatigue rupture resistance compared to X42 steel. Furthermore, the impact toughness value of 20# carburizing steel is higher than that of X42 steel in the impact toughness test. Both steels show varying effects on crack growth under different hydrogenation pressures. Importantly, the impact toughness of both steels is less affected by different hydrogenation pressures. • Hydrogen embrittlement mechanism of high-strength steels is investigated. • Steel deformation under different hydrogen environments is tested. • The relationship between hydrogen embrittlement and defects in steels is analyzed. • The effects of hydrogen pressure on two types of steels are compared. [ABSTRACT FROM AUTHOR]

Atmospheric corrosion is one of the major sources of hydrogen in a high-strength-steel product in service. Even low concentrations of absorbed hydrogen can cause a hydrogen embrittlement-related material degradation. The extent of atmospheric corrosion and thus the related hydrogen entry is highly dependent on the environmental parameters, such as the relative humidity. The present work focused on the hydrogen entry at low relative humidity, where atmospheric corrosion rates are expected to be low. Hydrogen insertion and distribution in CP1000 steel induced by corrosion under dried and rewetted single droplets of aqueous NaCl and MgCl2 solution were studied using the Scanning Kelvin Probe (SKP) and the resulting amounts of diffusible hydrogen were analyzed using thermal desorption mass spectrometry (TDMS). Corrosion product analyses were carried out with SEM/EDX, XRD, and Mössbauer spectroscopy. The results revealed the strong impact of salt type and concentration on the hydrogen entry into steel. The hygroscopic effect of MgCl2 and the formed corrosion products were responsible for the prolonged insertion of hydrogen into the steel even at very low levels of relative humidity.

We investigate proximity effects on hydrogen absorption in ultra-thin vanadium layers through combing light transmission and electron scattering. We compare the thermodynamic properties of the vanadium layers, which are based on the superlattice structure of Cr/V (001) and Fe/V (001). We find an influence of the proximity effects on the finite-size scaling of the critical temperatures, which can be explained by a variation of dead layers in the vanadium. In addition to this, the proximity effects on hydrogen absorption are also verified from the changes of excess resistivity.

Titanium is reactive toward hydrogen forming metal hydride which has a potential application in energy storage and conversion. Titanium hydride has been widely studied for hydrogen storage, thermal storage, and battery electrodes applications. A special interest is using titanium for hydrogen production in a hydrogen sorption-enhanced steam reforming of natural gas. In the present work, non-isothermal dehydrogenation kinetics of titanium hydride and kinetics of hydrogenation in gaseous flow at isothermal conditions were investigated. The hydrogen desorption was studied using temperature desorption spectroscopy (TDS) while the hydrogen absorption and desorption in gaseous flow were studied by temperature programmed desorption (TPD). The present work showed that the path of dehydrogenation of the TiH2 is d®b®a hydride phase with possible overlapping steps occurred. The fast hydrogen desorption rate observed at the TDS main peak temperature were correlated with the fast transformation of the d-TiH1.41 to b-TiH0.59. In the gaseous flow, hydrogen absorption and desorption were related to the transformation of b-TiH0.59 Û d-TiH1.41 with 2 wt.% hydrogen reversible content.

This study is based on the need to consolidate environmentally friendly technology to overcome pollution problems caused by conventional refrigerators. Compounds based on La(Fe,Si) 13 have attracted much attention in many fields of industry as low cost materials as well as bright prospects for practical applications. The alloys obtained in this study are based on the LaFe 11.57 Si 1.43 and LaFe 11.57 Si 1.43 H systems. These alloys were produced by melt-spinning of samples initially melted in an electric arc furnace and homogenized by heat treatment at 1050 °C for 2 h. LaFe 11.57 Si 1.43 alloys to be hydrogenated with very little amount of 0.9 MPa of 5% H2/Ar gas and heat-treated at 723 K for one hour. An analysis of the crystal structure using X-ray diffraction measurements revealed that all alloys showed La-Fe-Si (1:13 phase) as the majority one with 85.8 wt% and 83.1 wt% for LaFe 11.57 Si 1.43 and LaFe 11.57 Si 1.43 H respectively. The hyperfine and magnetic behavior of the alloys were studied by means of Mössbauer spectroscopy, and it was observed that the LaFe 11.57 Si 1.43 alloy was fitted with a singlet and a doublet corresponding to 1:13 phase with a total spectral area of 72.5%, and in the LaFe 11.57 Si 1.43 H alloy exhibited a ferromagnetic behavior at room temperature with a hyperfine field of 19.4 T. Using vibrating sample magnetometry, it was demonstrated that the essential magnetic parameters to optimize the magnetocaloric effect, Curie temperature, and saturation magnetization at room temperature, significantly improved from 228.23 K to 308.1 K and 37.03 A m2kg−1 to 120 A m2kg−1, respectively, with the addition of hydrogen. Endothermic peaks possibly associated with first-order magnetic phase transition were found in each of the La-Fe-Si alloys using differential scanning calorimetry, coinciding with its T C value of 315.1 K. These results demonstrate that hydrogenation under a poor hydrogen gas atmosphere is an effective and safer method for improve the magnetocaloric properties of the LaFe 11.57 Si 1.43 system. • A high concentration of the 1:13 phase was successfully synthesized. • The LaFe11.57Si 1.43 H alloy exhibited ferromagnetic behaviors at room temperature. • Hydrogenation under a poor hydrogen gas atmosphere is an effective method. • Lattice expansion had a positive influence on the magnetic and thermal properties of La-Fe-Si-H. [ABSTRACT FROM AUTHOR]

The kinetics of the hydrogen evolution reaction on nickel silicide NiSi (fabricated by Czochralski method) in solutions of 0.5 M H2SO4 and 1 М КОН has been studied by polarization measurements and electrochemical impedance spectroscopy. In an acid solution two Tafel slopes have been observed on the polarization curve for NiSi: the slope b is equal to 0.105 V/decade at E > –0.33 V (SHE) and b = 0.18 V/decade at E < –0.33 V. In an alkaline solution one linear region of the Tafel line has been observed, b = 0.13 V/decade. The exchange current density i0 is 4.45·10–6 A cm–2 and 4.2·10–6 A cm–2 in acidic and alkaline solution respectively. In an acidic solution the Nyquist plots consist of a single semicircle at not high cathodic polarizations and of two well-resolved capacitive arcs at higher cathodic polarizations. An equivalent circuit considering the hydrogen absorption reaction was used at high cathodic polarizations. In an alkaline solution the Nyquist plots consist of a single capacitive semicircle. The potential dependences of equivalent circuit elements R1, R2, C2 and time constant R2C2 have been discussed. The conclusion was made that hydrogen evolution on NiSi in a sulfuric acid solution proceeds via a two-route Volmer–Heyrovsky–Tafel mechanism (with hydrogen absorption reaction in parallel) and in an alkaline solution via the Volmer–Heyrovsky mechanism with unequal transfer coeffi cients for the steps. The obtained results show that the adsorbed atomic hydrogen on an NiSi electrode obeys the Langmuir isotherm in both solutions.

• Increasing the degree of deformation in steel can increase the amount of trapped hydrogen (H) in the steel; which can be measured in the regions with higher local strain. • A clear relation between the deformation degree and the local H-content is established for a dual phase steel. • Microstructural characterizations and micro-hardness measurements in punched steel revealed that the shear affected zone is located nearby the punched hole. • Local hydrogen measurements confirmed the presence of a locally very high amount of hydrogen within the shear affected zone. The microcapillary cell electrochemical method is capable of evaluating hydrogen (H) uptake in steel with respect to deformation, which is induced by various mechanical methods (cold rolling, bending and punching). A clear relation between the deformation degree and the local H-content is established for dual phase (DP600) steel. The magnitude of the deformation nearby a punched edge is quantitatively determined using electron backscatter diffraction technique. A shear-affected zone is identified at the edge of the punched hole. The dedicated local electrochemical measurements confirm the presence of high concentrations of local-H in this shear affected zone, which is likely detrimental for H-embrittlement. [ABSTRACT FROM AUTHOR]

Nanoparticles (NPs) of Pd are known for their high hydrogen storage capacity. The addition of a small amount of Pt has been found to further enhance the storage capacity, highlighting the important role of Pd–Pt interactions in the interfacial region. In this work, we investigated the element-specific local structure of core (Pd)–shell (Pt) NPs and their solid-solution alloy phase, which is formed through the process of hydrogen absorption and desorption (PHAD). To unveil the mechanism of enhanced hydrogen storage capacity in the solid-solution (SS) phase, we used extended X-ray absorption fine structure spectroscopy and investigated the local structure around the Pd and Pt. A notable stress in the Pd structure and a higher atomic pair distance than that of bulk Pd was observed in the core–shell NPs. Additionally, a Pd–Pt alloy formed in the interfacial region shows a deviation in local structure compared with both bulk Pd and Pt resulting from disorder and anharmonic distributions in both Pt–Pt and Pt–Pd atomic pair distances. In the solid-solution phase, the strained Pd NPs relaxed with a significant fraction of Pd remaining in the fcc structure. Moreover, the interfacial alloy was distributed homogeneously in the SS phase. This novel alloy phase has unique structural properties and provides active binding sites for hydrogen storage. The uniform distribution of the alloying phase, which acts as a source of active binding sites, facilitates high coverage resulting in an enhanced hydrogen storage capacity. • Hydrogen solubility of Pd-Pt core-shell (CS) and solid-solution (SS) alloy was investigated. • EXAFS reveals a significant stress in Pd lattice in CS configuration compared to SS phase. • Pt shell has formed an interfacial alloy affecting the local structure of Pd and Pt. • The alloy phase afflicts with disorder and anharmonic distribution of atomic pairs distances. • Uniform distribution of interfacial phase enhances the hydrogen solubility in SS configuration. [ABSTRACT FROM AUTHOR]

Abstract In this study the activation behavior of hydrogen absorption in a TiZrNbTa high-entropy alloy (HEA) has been investigated. Results showed that the hydrogen absorption temperature of the TiZrNbTa HEA were significantly decreased from 715 K to room temperature, and the hydrogen absorption kinetics were also improved greatly after activation. The X-ray photoelectron tests showed that, after activation, almost all the oxides at the surface of the TiZrNbTa HEA were reduced to suboxides and sub-hydroxides after activation, but only parts of oxides at the surface of pure metals were reduced, in the form of suboxides. Based on these results, a two-step mechanism for the activation of TiZrNbTa HEA was proposed. The positron annihilation lifetime analysis showed that both the size and concentration of vacancy clusters increased significantly in the TiZrNbTa HEA after activation. It could be responsible for the improvement of hydrogen absorption kinetics in TiZrNbTa HEA. Highlights • The hydrogen absorption temperature of TiZrNbTa high entropy alloy decreased to room temperature after activation. • After activation, the transformation from oxides into suboxides and sub-hydroxides in the TiZrNbTa surface was observed. • Both the size and concentration of vacancy clusters increased significantly in the TiZrNbTa alloy after activation. • A two-step activation mechanism of TiZrNbTa alloy was proposed. [ABSTRACT FROM AUTHOR]

Abstract This study reports the investigative conclusions of parametric studies conducted to understand the effect of operating parameters on absorption and desorption characteristics of LaNi 4.7 Al 0.3 metal hydride system for thermal management applications. Reactor with improved design containing 55 embedded cooling tubes is fabricated and filled with 4 kg of metal hydride alloy. Using water as heat transfer fluid (HTF), effects of supply pressure, HTF temperature and HTF flow rate on absorption and desorption characteristics of the reactor are analyzed. Increasing supply pressure leads to prominent improvement in absorption capacity while the increase in HTF temperature enhanced desorption performance. At 20 bar and 20 °C, 46.2877 g of hydrogen (1.16 wt%) was absorbed resulting in total energy output of 707.3 kJ for 300 s. During desorption at 80 °C with water flow rate of 8 lpm, heat input of 608.1 kJ for 300 s resulted in 28.5259 g of hydrogen desorption. [ABSTRACT FROM AUTHOR]

To avoid failures due to hydrogen embrittlement, it is important to know the amount of hydrogen absorbed by certain steel grades under service conditions. When a critical hydrogen content is reached, the material properties begin to deteriorate. The hydrogen uptake and embrittlement of three different carbon steels (API 5CT L80 Type 1, P110 and 42CrMo4) was investigated in autoclave tests with hydrogen gas (H2) at elevated pressure and in ambient pressure tests with hydrogen sulfide (H2S). H2 gas with a pressure of up to 100 bar resulted in an overall low but still detectable hydrogen absorption, which did not cause any substantial hydrogen embrittlement in specimens under a constant load of 90% of the specified minimum yield strength (SMYS). The amount of hydrogen absorbed under conditions with H2S was approximately one order of magnitude larger than under conditions with H2 gas. The high hydrogen content led to failures of the 42CrMo4 and P110 specimens.

Hydrogen can penetrate reversibly a number of metals, occupy the interstitial sites and cause large expansion of the crystal lattice. The question discussed here is whether the kinetics of the structural response matches hydrogen absorption. We show that thin Pd and CoPd films exposed to a relatively rich hydrogen atmosphere (4% H2) inflate irreversibly, demonstrate the controllable shape memory, and duration of the process can be of orders of magnitude longer than hydrogen absorption. The dynamics of the out-of-equilibrium plastic creep are well described by the Avrami-type model of the nucleation and lateral domain wall expansion of the swelled sites.

New pseudobinary Zr(Pd x V 1−x ) 2 , x = 0.1, 0.15, 0.2, intermetallic compounds have been synthesized and characterized by X-ray diffraction and their shear, G, and bulk, B, moduli have been measured. Hydrogen absorption isotherms of the x = 0.1 and 0.2 alloys have been determined at temperatures between 200 °C and 500 °C in the pressure range 10 −7 -1.3 atm. An increase of the Pd content causes a decrease of both the hydrogen absorption capacity and the stability of the corresponding hydrides. The latter behavior is attributed mainly to the Pd-induced increase of the stability of the starting intermetallics (rule of reversed stability). A combined effect of the heats of alloy formation, ΔH alloy , and the crystal cell volumes, V , on the stabilities of the hydrogenated compounds is shown for Zr(Pd x V 1−x ) 2 and Zr(Al x V 1−x ) 2 in terms of correlation factor ΔH alloy + b V , where b is a fitted constant. The decrease of the hydrogen absorption capacity with x in Zr(Pd x V 1−x ) 2 correlates well with an increase of the G/B ratio, as previously suggested. We have also tried to produce and hydrogenate alloys of the systems Ti(Pd x Ni 1−x ) 3 , Zr(Pd x Fe 1−x ) 2 and Zr(Pd x Ni 1−x ) 3 but did not find significant hydrogen absorption. [ABSTRACT FROM AUTHOR]