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Surface corrosion product formation is one of the important factors affecting the corrosion rate and hydrogen uptake in a H2S environment. However, it is still unclear how the base material composition will affect the corrosion products that are generated, and consequently their impact on the corrosion rate. In this paper, corrosion product formation and the impact of the Mo content of the base material on the composition of the corrosion products and hydrogen absorption in a sour environment was investigated. The corrosion layer was composed of a double layered mackinawite (FeS1−x) structure, which was enriched with molybdenum and chromium. The layers were formed via two different mechanisms, i.e., the inner layer was created via a general oxide film formation corrosion mechanism, whereas the upper layer was formed by a precipitation mechanism. The presence of this double corrosion layer had a large influence on the amount of diffusible hydrogen in the materials. This amount decreased as a function of contact time with the H2S saturated solution, while the corrosion rate of the materials shows no significant reduction. Therefore, the corrosion products are assumed to act as a physical barrier against hydrogen uptake. Mo addition caused a decrease in the maximal amount of diffusible hydrogen.

Hidrida logam berbasis MgH2 dengan sisipan 1 wt% katalis Fe telah berhasil disintesis dengan teknik ball milling. Hasil proses miling selama 80 jam menunjukkan bahwa ukuran butir material telah membentuk struktur nanokristal. Hal ini ditunjukkan oleh profil difraksi sinar-X dimana terjadi pelebaran puncakpuncak difraksinya dengan meningkatnya waktu miling. Hasil uji absorpsi secara gravimetrik diketahui bahwa MgH2 berkatalis 1 wt% Fe mampu menyerap hydrogen sebesar 5,5 wt% dalam waktu ~20 menit pada temperatur 300 oC. Hasil ini sekaligus memperlihatkan bahwa sejumlah kecil katalis Fe bekerja secara baik dalam memperbaiki sifat absorpsi material penyimpan hydrogen berbasis Mg. (Metal hydrides are of great interest as hydrogen storage media especially for automotive application. Hydrides of magnesium and magnesium alloys are particularly attractive as they combine potentially high hydrogen storage capacities, 7.6 wt%. But, unfortunately, the sorption properties are poor. For example, conventional hydrogenation of magnesium requires prolonged treatment at temperatures of 300 oC and above. Here, we report the absorption properties of MgH2 catalyzed with a small amount of Fe element (1wt%) under argon atmosphere prepared by ball milling in 80 hours. As the results, it showed the influence of milling time on the absortion kinetics of material which could absorp hydrogen in amount 5.5 within 20 minutes at 300 oC. It is obvious that longer milling time and small amount of catalyst could improve the sorption properties of Mg-based hydrides). © 2009 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Copper coated Bi 0.5 Sb 1.5 Te 3 powders were prepared through electroless plating with simplified pretreatment method. After hydrogen reduction, the powders are consolidated into bulk by spark plasma sintering. The lowest lattice thermal conductivity in Bi 0.5 Sb 1.5 Te 3 /Cu reduces to 0.25 W/m·K at 371.5 K after annealing. The figure of merit ( ZT ) of Bi 0.5 Sb 1.5 Te 3 /Cu ascends in a large scale and reaches 1.08 at 373 K and 423 K before and after annealing respectively. The average ZT values of Bi 0.5 Sb 1.5 Te 3 /Cu samples both rise from 0.36 to 0.82, which makes this material suitable for application in a wide temperature range. [ABSTRACT FROM AUTHOR]

Due to hydrogen possessing a relatively large neutron scattering length, hydrogen absorption and desorption behaviors in metal thin films can straightforwardly be investigated by neutron reflectometry. However, to further elucidate the chemical structure of the hydrogen absorbing materials, complementary techniques such as high resolution X-ray reflectometry and diffraction remain important too. Examples of work on such systems include Nb- and Pd-based multilayers, where Nb and Pd both have strong affinity to hydrogen. W/Nb and Fe/Nb multilayers were measured in situ with unpolarized and polarized neutron reflectometry under hydrogen gas charging conditions. The gas-pressure/hydrogen-concentration dependence, the hydrogen-induced macroscopic film swelling as well as the increase in crystal lattice plane distances of the films were determined. Ferromagnetic-Co/Pd multilayers were studied with polarized neutron reflectometry and in situ ferromagnetic resonance measurements to understand the effect of hydrogen absorption on the magnetic properties of the system. This electronic effect enables a novel approach for hydrogen sensing using a magnetic readout scheme. [ABSTRACT FROM AUTHOR]

The influence of hydrogen absorption reaction (HAR) proceeding through H ads with kinetic or with diffusion control on the dependence of the elements R 1 , R 2 , C 2 of the equivalent electrical circuit for hydrogen evolution reaction (HER) on the electrode potential E has been considered. It has been shown that if HER proceeds through the Volmer–Heyrovsky mechanism, then the presence of HAR reduces the slope d log R 2 / dE at all Е and the slope d log С 2 / dE at sufficiently high cathodic polarisations. In the case of the Volmer–Tafel mechanism the presence of HAR mainly affects the resistance R 2 . The character of the dependences of R 1 , R 2 , C 2 on Е is the same for both kinetic and diffusion control of HAR. An interpretation of the experimental impedance data for HER on CoSi 2 in 0.5 M H 2 SO 4 has been presented. [ABSTRACT FROM AUTHOR]

We investigated the effect of hydrogen absorption conditions on the hydrogen desorption behavior of the Ni-Ti superelastic alloy with cathodic hydrogen charging in 0.9% NaCl aqueous solution. The amount of desorbed hydrogen at low temperature (200°C) increased with increasing cathodic current density. It is likely that the increment of desorbed hydrogen at low temperature was due to the increment of hydride formation. The Vickers hardness in the vicinity of the alloy surface also increased with increasing cathodic current density. This is probably due to hydride formation in the vicinity of the alloy surface. These results suggest that the hydrogen concentration in the vicinity of the alloy surface increased with increasing cathodic current density, i.e., increasing the amount of generated hydrogen per unit time, thereby causing the acceleration of hydride formation. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) and autoclave corrosion tests in 360 °C water were used to investigate the influence of Sb, Sc, Nb and Sn on the corrosion and hydrogen pick-up (HPU) of Zr-alloys. Sc was shown to have a strongly detrimental effect on alloy corrosion resistance. The Nb–Sb–Zr ternary alloy exhibited significantly improved corrosion resistance over Zr–Nb and ZIRLO, and had little measurable HPU after 195 days. The ratio of Sb ′ Zr / Sb Zr • was shown to transition smoothly with applied space charge, implying Sb can act as a buffer to charge imbalance in the oxide layer. [ABSTRACT FROM AUTHOR]

The hydrogen-induced phase separation of Cu–Zr binary amorphous alloys during hydrogen gas charging at elevated temperature was demonstrated; the homogeneous binary alloy was decomposed into pure Cu and Zr-hydride by absorbing hydrogen into the structure. The decomposition, which is attributed to the opposed affinity to hydrogen of Cu and Zr, took place in nanometer scale. The hydrogen absorption kinetics was compared for the alloys with different compositions. The structure after hydrogen absorption was analyzed using x-ray diffraction, ultra-small and small angle neutron scattering, and electron microscopy. [ABSTRACT FROM AUTHOR]

A gradient three-layer Al-Mo coating was deposited on steel using magnetron sputtering method. The corrosion properties of the coating were studied in 3.5 wt.% NaCl solution using electrochemical techniques, whereas the hydrogen-induced cracking (HIC) resistance was examined by constant-load tests using notched tensile specimens. These results were compared with conventional electroplated cadmium-coated steel. The results show that the gradient Al-Mo coating exhibits better corrosion and HIC resistance when compared to electroplated cadmium. This was due to the excellent corrosion resistance of the bottom aluminum-rich layer, while the top Mo-rich layer provided good lubrication properties. [ABSTRACT FROM AUTHOR]

Among the applications of phosphate glasses, one of the most promising is their potential as catalysts for water dissociation into hydrogen and oxygen and to absorb hydrogen in its structure, making them good candidates to be used as electrolytes in intermediate temperature fuel cells (200–500 °C). Phosphate based glasses with molar composition 30PO 5/2 –25NbO 5/2 –10WO 3 –25Na 2 O–10[(1-x)BaO–xSrO], with x = 0, 20, 50, 60, 80 and 100 mol% were prepared by the melt quenching technique. The as-prepared samples revealed to be transparent, mechanical and thermally stable at room temperature. Differential thermal analysis (DTA) measurements showed Tg values around 500 °C, and high thermal stability. The structure of the samples was studied by X-Ray powder Diffraction (XRD) Raman spectroscopy, and the morphology by Scanning Electron Microscopy (SEM). Dc (σ dc ) and ac (σ ac ) conductivities and dielectric spectroscopy measurements were performed as function of temperature (100–370 K) presenting a conductivity predominantly ionic (σ electronic /σ ionic of about 10 − 4 ). The dielectric spectroscopy was measured in the frequency range 100 Hz–1 MHz. [ABSTRACT FROM AUTHOR]

Hydrogen absorption (HA) capacity of Sm(CobalFexCu0.053Zr0.02)7.84 ( $x=0.2$ , 0.3, 0.4, 0.5) as-cast alloys was improved through increasing Fe content and its mechanism was symmetrically analyzed. X-ray diffraction analysis indicates that the main phase of all as-cast alloys was 1:7 phase. Due to lower electronegativity of Fe than that of Co, activation energy of chemical adsorption for 1:7 phase was reduced with increasing Fe content. Due to larger atomic radius of Fe than that of Co, lattice parameters and lattice gaps of 1:7 phases were enlarged with increasing Fe content, and diffusion barrier of H atoms was lowered resulting from increasing lattice parameters and sizes of lattice gaps. These all strengthened the HA capacity of 1:7 phase. Two principles are mentioned to provide theoretical guidance for strengthening HA capacity by adding other elements. [ABSTRACT FROM AUTHOR]

An ammonium thiocyanate (NH4SCN) solution is widely used in hydrogen embrittlement evaluations of high-strength steel materials. It is known that an increase in the specific solution volume to the specimen surface area results in a severe evaluation in hydrogen embrittlement testing. This paper explains the reason for this based on the change in the solution pH induced by the cathodic reaction that accompanies thiocyanate ion decomposition and governs hydrogen absorption. In addition, the pH dependence of the cathodic reaction governing hydrogen absorption is clarified using a sodium thiocyanate solution containing a buffer solution to control the solution pH. It is shown that immersing steel specimens in the pH-controlled sodium thiocyanate solution achieves a higher hydrogen content compared with the level attained with the NH4SCN solution. [ABSTRACT FROM AUTHOR]

Theoretical studies on the total energy, electronic structure and bond of Zr(Cr 0.5 Ni 0.5 ) 2 intermetallic compound and its hydrides were performed using density functional calculations. The optimized c/a ratio was found in good agreement with experimental data of the C14 Laves phase. When hydrogen is introduced in the AB 2 matrix (A = Zr; B = Ni, Cr) the A 2 B 2 sites are preferentially occupied in the structure, followed by the AB 3 while B 4 remains empty. The volume of the intermetallic increases up to 52.19% when 28H are absorbed in the unit cell, whereas the binding energy remains practically the same up to −6.76 eV/H, indicating little interaction. Among hydrogenations the main contribution to density of states is due to d electrons of all components of the structure. H-metal bonding is detected in the range −8 to −6 eV. Above 8H the magnetic moment increases with respect to the pure Laves phase. [ABSTRACT FROM AUTHOR]

The hydrogen absorption energy and the density of states (DOS) are calculated based on the density functional theory to study the effect of alloying elements on the properties of Pd-M solid solution alloys (M = Rh, Pd, Ag, Ir, Pt, Au). The calculated H absorption energy shows a dependence on the identity of the alloying elements and the trend indicates a correlation with experimental result. The calculation results suggest that the local environment surrounding the H atoms strongly affects the H absorption energy. That is, the first nearest-neighbors of the H atom determine the stability of the system and this implies that H absorption capacity of the entire alloys attributes to the atomic-scale configurations. The DOS provides a good explanation of these observations. Hybridization between the nearest-neighbor metals and H shows evidence of the contribution of the local environment. Furthermore, the elemental dependence of the H absorption energy for each alloy is explained by the DOS near the Fermi energy, which is found to influence the stability of H absorption. [ABSTRACT FROM AUTHOR]

In this work, new phosphate glasses with the molar composition 20.7P2O5-17.2Nb2O5-13.8WO3-34.5A2O-13.8B2O3 where A = Li, Na and K were prepared using the melt quenching technique. These types of glasses have potential to absorb hydrogen in its structure, which makes them promising materials to be used as electrolytes in intermediate temperature fuel cells. Additionally, niobium phosphate glasses can also have applications such as glass fibers, optical lenses, hermetic sealing and electrodes. The structure of the obtained samples was analyzed using Differential Thermal Analysis (DTA), X-ray powder diffraction (XRD), and Raman spectroscopy and the morphology by Scanning Electron Microscopy (SEM). The DTA measurements revealed values of glass transition temperature around 415 °C, and the Raman analysis showed that the amount of alkali and niobium oxides included on the studied compositions, successfully disrupted the P-O-P chains characteristic of the phosphate glasses. Dc (σdc) and ac (σac) conductivities and dielectric spectroscopy measurements were performed as function of the temperature (200-370 K) which presented conductivity predominantly ionic (selectronic/sionic of about 10-4). The dielectric spectroscopy was measured in the frequency range 100-1 MHz. [ABSTRACT FROM AUTHOR]

20 nm thick Pd coatings deposited on Si substrates with 800 nm SiO 2 and 1 nm Cr buffer layers were treated in a 2.45 GHz microwave plasma source at 700 W plasma power and 40 Pa working pressure without substrate heating. For obtaining information on the effect of energy influx due to ion energy on the palladium films the substrate potential was varied from U sub = 0 V to − 150 V at constant gas flow corresponding to mean ion energies E i from 0.22 eV ∙ cm − 2 ∙ s − 1 to 1.28 eV ∙ cm − 2 ∙ s − 1 . In contrast to high pressure reactions with metallic Pd, under plasma exposure we do not observe solid solutions over a wide range of hydrogen concentration. The hydrogen incorporation in Pd films takes place discontinuously. At 0 V substrate voltage palladium hydride is formed in two steps to PdH 0.14 and PdH 0.57 . At − 50 V substrate voltage PdH 0.57 is formed directly. However, substrate voltages of − 100 V and − 150 V cause shrinking of the unit cell. We postulate the formation of two fcc vacancy palladium hydride clusters PdH Vac (I) and PdH Vac (II). Under longtime plasma exposure the fcc PdH Vac (II) phase forms cubic PdH 1.33 . The fcc PdH 0.57 phase decomposes at temperatures > 300 °C to form metallic fcc Pd. The hydrogen removal causes a decrease of lattice defects. In situ high temperature diffractometry measurements also confirm the existence of PdH Vac (II) as a palladium hydride phase. Stoichiometric relationship between cubic PdH 1.33 and fcc PdH Vac (II) becomes evident from XR measurements and structure considerations. We assume both phases have the chemical composition Pd 3 H 4 . Up to 700 °C we observe phase transformation between both the fcc PdH Vac (II) and cubic PdH 1.33 phases. These phase transformations could be explained analog to a Bain distortion by displacive solid state structural changes. [ABSTRACT FROM AUTHOR]

Pd–Ru–Rh electrodeposits were obtained potentiostatically from aqueous baths containing different concentrations of Pd, Ru and Rh ions. The formation of Pd–Ru–Rh alloys was confirmed electrochemically through the examination of sample properties in the acidic solution with the use of cyclic voltammetry. The alloy formation was also proved with the use of energy dispersive X-ray spectroscopy and X-ray diffraction. XRD and EDX measurements have certified the homogeneity of a single bulk alloy phase. The XRD results show that the lattice parameter of the Pd–Ru–Rh alloy is smaller than that of Pd, i.e. Pd, Ru and Rh form contracted alloys. This is also mirrored in the course of hydrogen absorption curves (H/M vs. E), with the α–β phase transition region shifted into lower potentials. Pd–Ru–Rh alloys with ca. 98.5% Pd in the bulk absorb by ca. 11% more hydrogen than pure Pd. In the process of electrochemical aging, the surface and bulk of Pd–Ru–Rh electrodes become enriched with Pd due to the preferential electrochemical dissolution of Ru and Rh. [ABSTRACT FROM AUTHOR]

In the present work, hydrogen storage properties of Ti 0.32 Cr 0.43 V 0.25 alloy and its composite with TiMn 2 have been studied. The alloy and the composites have been evaluated for their structures, pressure composition isotherms, hydrogen storage capacity, kinetics of hydrogen absorption and hydrogen desorption temperatures. Ti 0.32 Cr 0.43 V 0.25 alloy shows maximum 3.33, 1.82 and 1.30 wt. % hydrogen storage capacities at 303, 348 and 423 K, respectively. (Ti 0.32 Cr 0.43 V 0.25 ) 0.95 (TiMn 2 ) 0.05 composite absorbs maximum 2.90, 1.80 and 1.40 wt. % of hydrogen at 303, 348 and 423 K, respectively. Kinetic study shows that the hydrogen absorption rate is faster for the composites at the initial chemical reaction stage, and later in hydrogen diffusion stage the hydrogen absorption rate decreases. The saturated composite hydrides show additional hydrogen desorption peak at lower temperature, which is important for practical application. [ABSTRACT FROM AUTHOR]

We numerically studied the effects of additional components for internal heat transfer enhancement—that is, heat fins and metal foams—on the hydrogen charging performance. First, we applied a three-dimensional transient hydrogen absorption model developed in our previous works to two different experimental MHBs: one with heat fins and the other with metal foam. The simulation results were then compared with the experimental data measured during the hydrogen charging processes. The model predictions were found to be in good agreement with the experimental data in terms of the bed temperature evolution and hydrogen charging time. In addition, a parametric study was conducted on various MHBs with heat fins or metal foams that were designed to contain the same amount of ZrCo powder for the sake of comparison. The detailed analysis of the hydrogen absorption behavior with different MHB designs clearly demonstrated that superior MHB design should exhibit a higher effective conductivity in the metal powder region and lower overall thermal mass; these two advanced features can be achieved by using a metal foam with optimum porosity. [ABSTRACT FROM AUTHOR]

The hydrogenation behavior and structural change of Mg 85 Zn 6 Y 9 alloy with a long period stacking ordered (LPSO) structure are investigated. YH 2 hydride was formed in this alloy below 0.1 MPa hydrogen and the LPSO structure was destroyed. The remaining phase decomposed into MgH 2 and MgZn 2 by further hydrogenation. Finally, this alloy absorbed 1.6–1.8 (H/M) hydrogen and disproportionated into MgH 2 , YH 3 and MgZn 2 phases. Equilibrium hydrogenation at 673 and 623 K took 2 and 20 h, respectively. After dehydrogenation, 0.2–0.4 (H/M) hydrogen still remained as yttrium hydrides and hcp-based new phase was formed. However, the LPSO structure was not reformed. Hydrogen permeation was observed in this alloy under pressure differences of 0.4 and 0.1 MPa hydrogen at 623 K; however, the hydrogen permeability was 5.8 × 10 −10 (mol. H 2 m −1 s −1 Pa −0.5 ). The hydrogen diffusion coefficient of the alloy estimated from hydrogen absorption and permeability measurements was in the order of 10 −10 (m 2 s −1 ). [ABSTRACT FROM AUTHOR]