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The effect of substituting Co for Ni in GdNi3 on the hydrogenation properties and phase transformation during the hydrogen absorption–desorption process of GdNi3-xCox (x = 0, 0.2, 1.0) was investigated using P–C isotherms and X-ray diffraction analysis (XRD). GdNi3 showed a residual hydrogen content of 0.6 H/M after the first desorption process. The maximum hydrogen capacity of GdNi3 was 1.0 H/M, while the reversible hydrogen capacity decreased to 0.4 H/M because of the residual hydrogen. The reversible hydrogen capacity was improved to 1.0 H/M in GdNi2.0Co1.0, and two plateaus were observed in the absorption–desorption process. The crystal structures of the full hydride phases GdNi3H3.8 and GdNi2.8Co0.2H3.8 could not be determined because of the heavy peak broadening in the XRD pattern, while the PuNi3-type structure of the original alloy was retained in the full hydride phase GdNi2.0Co1.0H3.6. The retention rates of GdNi3 and GdNi2.0Co1.0 at 100 cycles were 75% and 92%, respectively. The cyclic properties of GdNi2.0Co1.0, up to 100 cycles, favorably compared with those of LaNi5, which was found to be related to the small lattice strain formed during the first hydrogen absorption process.

Pipeline welds are subjected to pre-straining based on designs for the installations. So, the present work deals with the effects of hydrogen and pre-straining on the mechanical properties of weld metal. According to the results, the weld metal microstructure was mainly comprised of acicular ferrite. Expectedly, the highest diffusible hydrogen belonged to the 33.6% pre-strained specimen which was equal to 5.1E-06 mol cm−3. Due to increase in hydrogen traps, the diffusible hydrogen content elevated at higher pre-straining. The largest variations in hydrogen blistering were observed in the 33.6% pre-strained specimen. The number of hydrogen cracks was increased by 18–23 percent with the most variations in the 33.6% pre-strained specimen. The hardness of weld metal specimen was increased by 5–10 percent at higher pre-straining in the presence of hydrogen. Hence, it could be concluded that the concurrent presence of hydrogen and pre-straining led to increase in the hardness and hydrogen defects into the weld metal.

The influences of moisture corruption and drying considerations on diffusible hydrogen were examined in this study. Two trials were carried out on an arc welding procedure, with the first being an assessment of the results of moisture contamination and the second being a test of the impact of welding constraints on diffusible hydrogen content. For example, the dispersible hydrogen found in welds was likened to the hydrogen levels of different unused electrodes. To calculate the proper drying constraints (Time and Temperature) for an applicable moisture contamination level in the weld electrode, an empirical equation was devised. For electrodes with a small diameter and welding parameter limits typically used for out-of-position welding, the equation is appropriate.

Accidents involving hydrogen explosions occur frequently, yet systematic methods of explosion suppression have not been investigated and applied. Therefore, this paper studied the deflagration characteristics in hydrogen with the addition of propane in the tube filled with mesh aluminium alloys (MAAs). The effects of different propane contents and different filling densities (the mass of MAAs per unit volume in a vessel) on the explosion suppression of the premixed gas are examined. The results show that propane and MAAs can effectively suppress the hydrogen-air explosion. However, MAAs have multiple suppression/promotion effects on the propane-hydrogen explosion. Based on the mathematical model, the dominant effect of MAAs changes abruptly toward the promoting effect when the hydrogen content exceeds 72.26% of the premixed gas stoichiometric concentration. It is also found that an increase in filling density would have a beneficial effect on explosion suppression. The study results provide references for preventing hydrogen and hydrogenated hydrocarbon fuels explosions and optimizing the performance of MAAs.

Purpose The purpose of this study is to develop the existence and mechanism of stress corrosion cracking (SCC) for A517 steel in marine environments. Design/methodology/approach Slow strain rate test (SSRT) and constant load tests were used to investigate the SCC susceptibility of A517 steel. In addition, the additive stresses caused by the corrosion film and hydrogen entering into steel were applied to reveal the fundamental mechanism of the SCC. Findings The SCC susceptibility increased due to anodic dissolution and additive stress caused by the corrosion-produced film under anode polarization. Furthermore, the SCC susceptibility increased with increasing cathodic polarization, which is due to the increased additional stress caused by hydrogen entering into the steel. However, when the cathode polarization further increased, the additional stress remained due to the constant hydrogen content, thus the SCC susceptibility did not vary. Moreover, the SCC susceptibility of A517 steel under an alternate immersion environment (AIE) was lower than that under a full immersion environment and the steel under the AIE with 0.5 W/D had the lowest SCC susceptibility. Originality/value The stress corrosion behaviors of A517 in marine environments under various conditions were systematically analyzed.

The article is devoted to the optimization of the degassing parameters of the AlSi9Cu3(Fe) alloy. The alloy was degassed with a solid degasser (Ecosal) and nitrogen or argon. The variable parameters were time and type of degasser. The test castings were made in permanent molds with an internal diameter of 25 mm and a length of 150 mm. The effect of the degassing time and the amount of degasser on the mechanical properties, as well as the hydrogen content and density index were investigated. The ALU SPEED TESTER developed by FMA was used to test the hydrogen content and the density index. Magmasoft software was used to design the geometry of the test castings. A significant effect of the solid degasser and degassing time on both the density index and the hydrogen content was demonstrated. Replacing nitrogen with argon did not bring any significant improvement in the above-mentioned parameters. The effect of degassing parameters on the mechanical properties of the EN AC-46000 alloy was much less significant, but was still visible. The optimal degassing parameters needed to obtain the highest strength parameters of the EN AC-46000 gravity die castings were determined.

Atomic hydrogen is a fundamental constituent of galaxies, and is the primary fuel for star formation. Understanding how the atomic hydrogen content of galaxies evolves with time is thus critical to understanding galaxy evolution. In this article, we discuss how one measures the atomic hydrogen content of distant galaxies, and what these measurements tell us about the evolution of our Universe.

(Sm1–xErx)2Fe17 (x = 0.1, 0.4) solid solutions have been prepared by induction melting and then hydrided to give high hydrogen content materials: Sm1.8Er0.2Fe17H4.4 and Sm1.2Er0.8Fe17H4.6. The main phase, 2 : 17, in the parent samples and products of hydrogenation has been shown to crystallize in the Th2Zn17 structure. The introduction of hydrogen into the crystal lattice of (Sm1–xErx)2Fe17 (x = 0.1, 0.4) leads to an increase in both the unit-cell volume and Curie temperature. As a consequence, the saturation magnetization of the hydrides near room temperature is considerably higher than that of the parent compounds.

In this study, the effect of hydrogenation on the magnetocaloric properties of extra-pure nanocrystalline terbium was investigated. The investigated compositions were TbH $${}_{x}$$ , where $$x=0{-}1.2$$ at H/arb.u. In addition to the major phase $$\alpha$$ -TbH $${}_{x}$$ , all the specimens contained a certain amount of a second phase, terbium dihydride ( $$\beta$$ -TbH $${}_{2}$$ ). For TbH $${}_{x}$$ specimens, the effect of hydrogenation on magnetocaloric properties was studied by both direct and indirect methods. The magnetocaloric effect was shown to decrease in a nearly linear fashion with increasing hydrogen content in the specimens.

Currently, one of the critical issues in the world is finding an appropriate green alternative to fossil fuels due to the concerns about global warming. As a hydrogen source, formic acid has been given particular attention owing to the attractive features such as high-energy density, no toxicity, high stability at ambient temperature and high hydrogen content. Introducing an affordable and highly efficient catalyst with easy recovery from the reaction mixture for selective dehydrogenation of formic acid is still demanding. In this report, we used a simple one-step process to synthesize Ni@Pd core shell nanoparticles on 3-aminopropyltriethoxysilane modified Fe3O4 nanoparticles. The existence of Ni and Pd results in a synergic effect on the catalytic activity. The NH2 groups play an important role for obtaining well-dispersed ultrafine particles with high surface area and active sites. In addition, Fe3O4 lead to convenient magnetic recovery of the catalyst from reaction mixture. Our results indicate that the as-prepared catalyst give the superb turnover frequency of 5367.8 h−1 with no additive, which is higher than most of the previously reported catalysts.

The only product of hydrogen combustion is water, so it is very clean. In this paper, the effects of low hydrogen content and FKR on the performance of the GDI engine are mainly studied. The simulation results show that adding less than 3% hydrogen in the GDI engine can improve the BP and BT of the engine under typical urban conditions such as 1500 rpm and 2000 rpm. As the hydrogen volume fraction and the FKR increase, the LFS of the mixture increases, resulting in a shorter ignition delay, combustion delay, and 10–90 % MFB. However, an increase in FKR results in a decrease in the BP and BT. In terms of fuel economy, the BSFC decreases as the hydrogen content increases, but as FKR increases, the BSFC increases. In terms of emissions, the proportion of hydrogen increases, HC and NOx emissions increase, and CO and CO2 emissions decrease. Therefore, adding hydrogen to the GDI engine while adjusting the FKR can improve the dynamic performance of the engine and reduce CO and CO2 exhaust emissions.

Austenitic stainless steels are used extensively in harsh environments, including for high-pressure gaseous hydrogen service. However, the tensile ductility of this class of materials is very sensitive to materials and environmental variables. While tensile ductility is generally insufficient to qualify a material for hydrogen service, ductility is an effective tool to explore microstructural and environmental variables and their effects on hydrogen susceptibility, to inform understanding of the mechanisms of hydrogen effects in metals, and to provide insight to microstructural variables that may improve relative performance. In this study, hydrogen precharging was used to simulate high-pressure hydrogen environments to evaluate hydrogen effects on tensile properties. Several austenitic stainless steels were considered, including both metastable and stable alloys. Room temperature and subambient temperature tensile properties were evaluated with three different internal hydrogen contents for type 304L and 316L austenitic stainless steels and one hydrogen content for XM-11. Significant ductility loss was observed for both metastable and stable alloys, suggesting the stability of the austenitic phase is not sufficient to characterize the effects of hydrogen. Internal hydrogen does influence the character of deformation, which drives local damage accumulation and ultimately fracture for both metastable and stable alloys. While a quantitative description of hydrogen-assisted fracture in austenitic stainless steels remains elusive, these observations underscore the importance of the hydrogen-defect interactions and the accumulation of damage at deformation length scales.

Examination of fractures of rolling bearings from steel 8Kh4V9F2-Sh (EI347-Sh) is used to assess the effect of production factors on the operating capacity of bearings under elevated loads. The microstructure and fractures of the steel are analyzed. The compressive stresses and the contents of the general and diffusion-mobile hydrogen are determined. It is shown that a fatigue crack appears in the material of the bearing in service in the case of an elevated hydrogen content and an unfavorable fiber structure.

In an electrochemical charging process applied before measuring the level of hydrogen in ferritic steels, two different side effects, a decrease in diffusible hydrogen content from steel and the detachment of 2nd phase particles from the steel surface, can occur, even during cathodic charging with a high charging current. Neglecting these side effects-associated with the surface chemistry during the electrochemical charging process can result in a false interpretation of the hydrogen diffusion and trapping behaviors in steel, producing conflicting data. A mechanistic reason for the side effects is provided based on the experimental results.

The solubility of Agcr has been measured in a 0.1m (mol·(kg H2O)−1) solution of HCl at a fixed hydrogen content (∼0.5m) as a function of NaCl concentration from 0.1 to 18m at temperatures ranging f...

Cyclodehydration of available N-alkylethanolamines with aldehydes and simultaneous or subsequent quaternization afford functionalized quaternary ammonium salts of N-nitroimidazolidine, oxazolidine and annulated bismorpholine type. Further replacement of their anions with residues of explosive acids provides a series of energyintensive quaternary salts with a rich hydrogen content possessing satisfactory energy characteristics and sufficiently high thermal stability.

Ammonia (NH3) is considered a promising carbon-neutral fuel, with a high hydrogen content, that can diversify the global energy system. Blending ammonia with a highly reactive fuel is one possible ...

This paper is a brief summary of the results of long-term experimental studies of C60Hx hydrofullerites with a hydrogen content of up to x ~ 60 or more, obtained by loading C60 fullerites with hydrogen at pressures up to 9 GPa and temperatures up to 500°C. Basically, this is an overview of already published data. Some results for hydrofullerites with compositions of x ~ 60 and x ~ 90 are presented for the first time.

Hydrogen concentrations in minerals of peridotite xenoliths in alkali basaltic rocks from Quaternary volcanoes in northwest Spitsbergen were measured using polarized Fourier transform infrared spectroscopy (FTIR) to trace the effects of geologic processes on hydrogen distribution in the continental lithospheric mantle. The mineral grains show hydrogen profiles with lower concentrations at rims suggesting diffusive hydrogen loss during the entrapment and transport of the xenoliths in magma. However, hydrogen concentrations in the centers of the grains are uniform and appear to represent hydrogen abundances in the Spitsbergen upper mantle. The olivine, orthopyroxene, and clinopyroxene contain 1–10, 130–290, and 350–560 ppm H2O, respectively. Hydrogen abundances away from metasomatic melt conduits recorded by Type 1 xenoliths are correlated with the concentrations of incompatible trace elements, indicating that hydrogen distribution is related to mantle metasomatism. By contrast, hydrogen near the melt conduits, recorded by Type 2 xenoliths, shows no regular correlations with incompatible trace elements (except Nb in clinopyroxene) and may be affected by fractional crystallization of amphibole in the conduits. Hydrogen contents decrease away from the melt conduits and are controlled by the interaction between the depleted host mantle and percolating metasomatic melts. Therefore, the metasomatic melt could have variably hydrated the Spitsbergen upper mantle via different processes. The H2O/Ce ratios of the melt in equilibrium with clinopyroxene near the metasomatic melt conduits range from 93 to 218, i.e., within the oceanic island basalt (OIB) range. This is consistent with that the metasomatic melt could have been derived from OIB-type sources evidenced by the Sr-Nd isotope compositions of the xenoliths.

The hydrogen assisted cracking susceptibility of Modified 9Cr–1Mo steel weld is evaluated by implant test by determining lower critical stress for different preheating and combination of pre, post ...

The effects of welding speed on the molten pool dynamics, the weld forming and the diffusible hydrogen content in deposited metal during underwater wet flux cored arc welding (FCAW) were studied. The molten pool was elongated with a higher solidification speed, as the welding speed was increased. The faster solidification improved the stability of the molten pool by reducing the bubbles and gas disturbance during FCAW, whereas it caused more hydrogen remaining in the deposited metal and increased the diffusible hydrogen content of the weld. According to the variation coefficient of weld reinforcement, the weld formation was improved at first and then deteriorated with the increasing welding speed. More bulges appeared in the weld at a low welding speed and pits were formed more easily with a high welding speed. The occurrence of the defects was closely related to the molten pool behaviors, which were determined by the pool angles during FACW.

The prior studies have investigated the influence of internal hydrogen on dwell-fatigue behavior of near-α titanium alloys primarily in the lamellar microstructural condition. In the current study, the effects of internal hydrogen, in the range 10–230 ppm (by weight), on the dwell-fatigue behavior of Ti-6242Si alloy were investigated. The examined alloy had a bimodal microstructure comprising approximately 70 vol% primary α grains and 30 vol% transformed β regions. The dwell-fatigue life generally increased with increasing hydrogen content. The dwell-fatigue lives were longer by a factor of as high as 6 for high (≥150 ppm) hydrogen contents than for the low ( 150 ppm) hydrogen contents. Specifically, these facets were inclined at ∼8 – 17° from the basal plane. Therefore, the longer dwell-fatigue lives observed for the alloys with hydrogen contents ≥150 ppm could not be explained on the basis of any differences in crystallography of the facets at crack-initiation sites. The longer dwell-fatigue lives for higher hydrogen contents can be explained within the framework of time-dependent load shedding from the soft microtextured regions (MTRs) to the hard MTRs if the local stress redistribution at the soft MTR/hard MTR boundary due to the hold at maximum load is reduced with increasing hydrogen content.

The relative proportions of different chemical components in wood tissues is one of the underlying factors that control wood properties. These proportions vary within and between woody tissues, and an accurate description of these variations is critical for parameterizing forest biogeochemical budgets and models. White spruce (Picea glauca (Moench) Voss) spacing intensities trials in the Petawawa Research Forest, Ontario, Canada, were sampled to evaluate variations in carbon (C), nitrogen (N), and hydrogen (H) concentrations between different tissue types, i.e., bark, cambium, knots, earlywood, latewood, and wood. Samples were freeze-dried and oven-dried to test the impact of the drying methods on these chemical elements. Freeze-dried C (51.14) and H (6.18) concentrations were significantly higher than those of oven-dried C (50.55) and H (6.06). Freeze-dried N (0.18) did not differ from oven-dried N (0.17). The spacing intensities impacted C, H, and N, with C content being higher in wider square spacings (4.3 m and 6.1 m), while the reverse was true for N and H, which exhibited higher content in smaller square spacings (1.2 m and 1.8 m). The results of this study also suggested that when it comes to the content of chemical elements, bark and knots should be treated as separate fuel types, whereas other woody tissues can be aggregated.

The crystal structures of $\mathrm{CaB}\text{\ensuremath{-}}{\mathrm{H}}_{n}$ compounds with $n=1--12$ in a pressure range of 50--300 GPa were studied using the genetic algorithm method and first-principles density-function theory calculations. Stable structures with stoichiometry of $\mathrm{CaB}{\mathrm{H}}_{6}$ and $\mathrm{CaB}{\mathrm{H}}_{7}$ were predicted in different pressure range. $\mathrm{B}{\mathrm{H}}_{4}$, $\mathrm{B}{\mathrm{H}}_{5}$, and $\mathrm{B}{\mathrm{H}}_{6}$ units were found to be the main motifs in these compounds. Moreover, metastable $Imm2$ $\mathrm{CaB}{\mathrm{H}}_{7}$ is dynamically stable above 180 GPa, with the formation of tetrahedral $\mathrm{B}{\mathrm{H}}_{4}$ unit surrounded by Ca atom and ${\mathrm{H}}_{3}$ unit. Electron-phonon coupling (EPC) calculations reveal that the superconducting properties are closely related to the strong hydrogen-boron bonding of the $\mathrm{B}{\mathrm{H}}_{4}$ unit in $Imm2$, and ${T}_{c}$ can reach \ensuremath{\sim}200 K at 200 GPa. As the major units, $\mathrm{B}{\mathrm{H}}_{4}$, $\mathrm{B}{\mathrm{H}}_{5}$, and $\mathrm{B}{\mathrm{H}}_{6}$ units exist in the $Imm2$, ${P}_{2}$, and $P{2}_{1}/m$ phases of $\mathrm{CaB}{\mathrm{H}}_{7}$ at 300 GPa, respectively; the corresponding EPC parameter \ensuremath{\lambda} decreases with the increase of hydrogen content in $\mathrm{CaB}{\mathrm{H}}_{7}$.

Altogether five platinum group metal (PGM) and PGM-free cathode catalysts were investigated in full PEM water electrolysis cells regarding their polarisation behaviour and their hydrogen and oxygen recombination properties. It was shown that the recombination activity of permeated oxygen and evolved hydrogen within the cathodic catalyst layer correlates with the activity of the oxygen reduction reaction (ORR) which was determined ex situ with linear sweep voltammetry. We found that the investigated PGM-free cathode catalysts had a low activity for the ORR resulting in higher measurable oxygen in hydrogen volume fractions compared to the PGM catalysts, which are more active for the ORR. Out of the three investigated PGM-free catalysts, only one commercially available material based on a Ti suboxide showed a similar good polarisation behaviour as the state of the art cathode catalyst platinum, while its recombination activity was the lowest of all catalysts. In addition to the recombination of hydrogen and oxygen on the electrocatalysts, we found that the prevalent carbon-based cathodic porous transport layers (PTL) also offer catalytically active recombination sites. In comparison to an inactive PTL, the measurable oxygen flux using carbon-based PTLs was lower and the recombination was enhanced by microporous coatings with high surface areas.

The effects of different pretreatment methods, including hydrothermal, acid, alkali, acid-heat and alkali-heat on lignin removal, reducing sugar (RS) yield and photo-fermentative biohydrogen production (PFHP) capability of corn stover (CS) were studied. NaOH-heat pretreatment was the most effective for lignin removal from CS, and the lignin removal rate reached 77%. All the studied pretreatment methods improved the total RS yield of CS, and the highest total RS yield (46.1 g/100 g raw material (RM)) was obtained from 2% NaOH-heat pretreated CS. 2% NaOH pretreatment realized the best PFHP of CS, which increased the hydrogen yield (HY), maximal hydrogen production rate (HPR) and highest hydrogen content (HC) by 31.9%, 50.9% and 20.1% respectively, and shortened hydrogen production lag time (HPLT) by 58.8% over that of untreated CS. However, NaOH-heat and 4% NaOH pretreatment weakened the PFHP capability of CS.

The discoveries of high-temperature superconductivity in ${\mathrm{H}}_{3}\mathrm{S}$ and ${\mathrm{LaH}}_{10}$ have excited the search for superconductivity in compressed hydrides, finally leading to the first discovery of a room-temperature superconductor in a carbonaceous sulfur hydride. In contrast to rapidly expanding theoretical studies, high-pressure experiments on hydride superconductors are expensive and technically challenging. Here, we experimentally discovered superconductivity in two new phases, $Fm\overline{3}m\text{\ensuremath{-}}{\mathrm{CeH}}_{10}$ (SC-I phase) and $P{6}_{3}/mmc\text{\ensuremath{-}}{\mathrm{CeH}}_{9}$ (SC-II phase) at pressures that are much lower ($l100\text{ }\text{ }\mathrm{GPa}$) than those needed to stabilize other polyhydride superconductors. Superconductivity was evidenced by a sharp drop of the electrical resistance to zero and decreased critical temperature in deuterated samples and in external magnetic field. SC-I has ${T}_{c}=115\text{ }\text{ }\mathrm{K}$ at 95 GPa, showing an expected decrease in further compression due to the decrease of the electron-phonon coupling (EPC) coefficient $\ensuremath{\lambda}$ (from 2.0 at 100 GPa to 0.8 at 200 GPa). SC-II has ${T}_{c}=57\text{ }\text{ }\mathrm{K}$ at 88 GPa, rapidly increasing to a maximum ${T}_{c}\ensuremath{\sim}100\text{ }\text{ }\mathrm{K}$ at 130 GPa, and then decreasing in further compression. According to the theoretical calculation, this is due to a maximum of $\ensuremath{\lambda}$ at the phase transition from $P{6}_{3}/mmc\text{\ensuremath{-}}{\mathrm{CeH}}_{9}$ into a symmetry-broken modification $C2/c\text{\ensuremath{-}}{\mathrm{CeH}}_{9}$. The pressure-temperature conditions of synthesis affect the actual hydrogen content and the actual value of ${T}_{c}$. Anomalously low pressures of stability of cerium superhydrides make them appealing for studies of superhydrides and for designing new superhydrides with stability at even lower pressures.

Pores in the AlSi10Mg products fabricated by laser powder bed fusion (LPBF) decrease the density of components. To study the mechanism of the formation and evolution of hydrogen pores, a model based on molecular dynamics (MD) is built. The influence of initial hydrogen content, heating time, and cooling time on the porosity is analyzed. Low initial hydrogen content, long cooling time, and appropriate heating time are beneficial to decrease the porosity of LPBF-fabricated products. When the heating time is 40 ps, the cooling time is 200 ps and initial hydrogen content is 0.081%; porosity can be reduced to 3.01%.

The vapor conversion of methane on Ni-containing catalysts on structured metal supports made from a Fe–Cr–Al alloy (fechral) is studied. A very high hydrogen content is observed in the products of the reaction for low percent 1% Ni/fechral catalysts (around 75% at 870°C).

This study is dedicated to present a reliable numerical methodology using Aspen Plus process simulator capable of performing a sensibility analysis of the downdraft gasification of Portuguese forest residues. Effects of critical parameters, including gasification temperature and steam-to-biomass ratio (SBR) on composition of the produced gas are discussed. The sensibility analysis is conducted using Aspen Plus simulator incorporating Fortran subroutines. The model is validated by experimental data and found to be in good agreement. The results of the sensibility analysis performed using air as gasification agent indicate that higher temperatures are favourable for a produced gas with higher hydrogen content and heating value. The simulation results also demonstrate that the use of steam as gasification agent allows increasing the hydrogen content and heating value of the produced gas in comparison to the use of air as gasifying agent. The knowledge of this data is decisive to the development of projects concerning the use of Portuguese forest residues as energy source.

Titanium alloys are widely used in aerospace structural parts. However, they have the characteristics of poor thermal conductivity, high temperature strength and high cutting temperature, which is easy to stick the tools when cutting. Thermohydrogen treatment (THT) is a way that utilizes the reversibility of hydrogen in the titanium alloys to improve the cutting performance. In this article THT process were carried out on TA15 alloy in a vacuum tube furnace. The results shows that the hydrogen content increases with the increase of hydrogen permeation temperature and pressure. As the hydrogen content increases, β phase increases and converts to the hydride δ phase. With the increase of hydrogen content, the cutting force decreases first and then increases. The cutting force is the lowest when the hydrogen content is about 0.3%.

This work demonstrates precision control of hydrogen content in La(Fe,Co,Si)13Hδ for the development of environmentally friendly magnetocaloric-based cooling technologies, using an electrolytic hydriding technique. We show the Curie temperature, a critical parameter which directly governs the temperature window of effective cooling, can be varied easily and reproducibly in 1 K steps within the range 274 K to 402 K. Importantly, both partially (up to 10%) and fully hydrided compositions retain favorable entropy change values comparable to that of the base composition. Crucially, we show in these second-order phase transition compounds, partial hydriding is stable and not susceptible against phase separation.

Cold cracking sensibility is a severe problem in the welding fabrication of large-scale steel structures. It is well known that diffusible hydrogen content in the weld metal strongly influences thi...

The formation of the structure and the phase composition of a heat-resistant titanium VTI-4 orthorhombic-intermetallic-based alloy is studied in the course of its alloying with hydrogen to different hydrogen contents. The laws of the changes in the phase composition of the hydrogen-containing alloy upon heating to different temperatures are determined. A portion of the VTI-4 alloy–hydrogen phase diagram under the conditions under study is constructed; it demonstrates the location of phase regions as a function of temperature and hydrogen content.

The hydrogen-assisted cracking susceptibility of modified 9Cr-1Mo steel weld is evaluated by Y-groove and gapped bead-on-plate test. It is found that a combination of pre + post heat is able to prevent cracking. However, the pre + post heat temperature combination determined from G-BOP test to prevent cracking (200 °C) is found to be higher than that in Y-groove test (100 °C). This is attributed to the higher weld restraint experienced in G-BOP than Y-groove test. For both the tests, the weld metal is found to be more susceptible to cracking than the heat affected zone. In addition to the diffusible hydrogen content of the welding consumables, diffusible hydrogen present in the G-BOP specimens prepared with different preheating and combinations of pre + post heat is also estimated by maintaining identical cooling conditions. The diffusible hydrogen in the weld for which no cracking is reported for G-BOP test (200 °C pre + post heat) is less than 1 ml/100 g. Considering the high restraint conditions present in the G-BOP test, it can be concluded that to prevent HAC in P91 steel, the choice of welding parameters (hydrogen content in welding consumable, heat input, pre/post-heating) should be such that diffusible hydrogen in the weld is brought down to below 1 ml/100 g.

Transition metals, including Ni, show good catalytic activity in the hydrogen storage reaction of Mg. In the present paper, first-principles calculation is performed to predict and analyze the hydriding reaction of Ni-incorporated Mg and experimental study is used to verify the accuracy of the forecast. Theoretical studies show that the hydriding reaction of Ni-incorporated Mg is a diffusion-controlled process. With Ni incorporation, the energy barrier of H2 dissociation is significantly decreased and the diffusion becomes the limiting step. Experimental studies confirm the results of theoretical studies. Besides, the material with Ni incorporation shows excellent activation performance and rapid absorption rates, leading to a high hydrogen content of 4.1 wt% in 60 s under 240 °C 3.0 MPa H2 and a low activation energy of 56.1 kJ mol−1 versus 0.4 wt% and 73.5 kJ mol−1 for the material without Ni incorporation. Atomic Ni only plays a role of catalyst.

International audience; This study analyzed a crack in a scrapped 18MnNiMo5 80-tonne shell. The root cause of crack formation was the low fracture toughness caused by a combination of a high hydrogen content and phosphorous segregation, caused by an inappropriate heat treatment. Cracking initiated on MnS inclusion clusters enabled by hydrogen desorption at the MnS/matrix interfaces. Crack propagation was due to the internal hydrogen pressure causing the crack tip stress intensity factor to exceed the locally-reduced fracture toughness. This new hydrogen induced cracking (HIC) mechanism can be designated as Hydrogen Induced Localised Damage (HILD). Appropriate process controls can eliminate such defects.

JSW Steel Ltd. supplies hydrogen-sensitive rail steels blooms for the manufacture of steel rails for Euro-rail application through AFERPI, Lucchini. The hydrogen distribution in the production of two high-carbon near-eutectoid rail steel grades VAR89S (typically, 0.70%C–0.3%Si–1.1%Mn–0.015%S) and VAR101 (typically, 0.80%C–0.42%Si–1.01%Mn–0.65%Cr–0.005%S) has been examined from the steel making stage to the as-cast blooms. In the steel grade VAR89S, the hydrogen distribution has been examined in the hot-rolled steel rails at different locations. The steel making involves primary steel making using energy optimizing furnace, ladle furnace followed by vacuum degassing. The hydrogen content before secondary steel making varies between 3 and 5.5 ppm H, which decreases to less than 1.5 ppm H after vacuum degassing. The steel picks up hydrogen, when transferred to tundish to a value, less than 2.5 ppm, associated with moisture in spray mass and tundish compound. On solidification in continuous casting, the hydrogen level decreases to less than 1.6 ppm H, which is associated with lowering of hydrogen solubility associated phase transformation of molten steel to solid. When the bloom is converted to steel rails, the hydrogen level further decreases due to the increased surface area-to-volume ratio. The final hydrogen levels in steel rails are

The hydrogen-induced delayed cracking (HIDC) behaviors of two types of 1500 MPa grade hot stamping steels (HSSs) have been investigated by the method of slow strain rate tensile test and hydrogen permeation, where one is manufactured by compact strip production (CSP) process which is a revolution to the traditional HSS and the other by the traditional cold rolling process. The results show that the performance of HSS produced by CSP is superior to that of the traditional HSS, due to lower hydrogen embrittlement index, lower hydrogen diffusion coefficient and lower hydrogen content. It has been found that HIDC behavior is closely associated with inclusions. The inclusions of HSS produced by CSP are mainly spherical Al–Ca–O and CaS, while the inclusions in the traditional HSS are TiN + Al2O3 + MnS with sharp edges and corners. Based on these results, the influence of composition, shape and distribution of inclusions in HSS on HIDC and the mechanism of HIDC from the perspective of inclusions were analyzed and discussed.

Humic substances, isolated from selected soils of the Russian Arctic, were investigated in terms of molecular composition and stabilization rate. The degree of polar soil organic matter stabilization was assessed with the use of modern instrumental spectroscopy methods. The analysis of humic acid (HAs) preparations showed that aliphatic fragments prevail in the organic matter isolated in polar soils. The predominance of aliphatic fragments was revealed in HAs from soils located in the coastal zone, which could be caused by regular refreshment of organic matter during sin-lithogenic process and processes of hydrogenation in HAs. Breaking of the C-C bonds and formation of chains with a high hydrogen content, which leads to the formation of aliphatic fragments in HAs, were noted. Data on the calculated atomic ratios of the elements in HAs are given and graphs show the main regularities in the formation of HAs and their properties. The integrated indicators of the molecular composition of humic acids of soils of the Russian Arctic are presented. The paper contains 4 Tables, 4 Figures and 44 References.

We develop a mathematical model and software module for the evaluation of the accumulation of defects with regard for hydrogen diffusion. The process is modeled by using two methods: by the Kachanov– Rabotnov–Lokoshchenko equations with two parameters (damage and hydrogen content) and the energy approach. For this purpose, we use Bridgman specimens with and without regard for the influence of hydrogen. The results of calculations obtained according to these two approaches are in satisfactory agreement with the experimental data. However, the energy approach gives a twicesmaller error.

Changes to the monotectoid transition in the niobium-hydrogen system due to the substitution of modest amounts of niobium with tantalum have been assessed via differential scanning calorimetry. Specimens of the alloy-hydrogen system, of varying hydrogen content, were analyzed over the temperature range from 323 to 398 K. From differential scanning calorimetric analysis, the phase transition temperature and the energy change due to the phase transition were quantified. The results show that the presence of tantalum significantly alters both the temperature and compositional characteristics of the monotectoid equilibrium. Relative to the niobium-hydrogen system, tantalum caused a decrease to the monotectoid transition temperature and a decrease in the width of the monotectoid horizontal boundary.

Hydrogen content in the diffusible range and beyond a critical level in steel is detrimental to the formation of hydrogen flakes that show up in ultrasonic testing. It is observed that the hydrogen content in any hot-rolled steel has a gradient with lowest hydrogen at the surface and higher towards the core. This is associated with the secondary phase transformation of high hydrogen-soluble austenite phase to a low-soluble ferrite phase, occurring last towards the core. Anti-flaking heat treatment was carried out in a flake-sensitive pearlitic rail steel grade, VAR89S, with an initial hydrogen level of 1.86 ppm at the core and 1.58 ppm in the surface of a 160-mm diameter hot-rolled bar. The heat treatment involved holding at 650 °C for times varying between 8 and 36 h, which decreased the hydrogen content. The decrease in hydrogen during anti-flaking heat treatment was correlated using Fick’s law model which took into account the initial hydrogen gradient across the bar cross section. The model predicted the experimental trend for hydrogen distribution at surface, mid-radius, and core. The hydrogen distribution at surface showed higher than predicted values, which could be attributed to the carbide spheroidization at the surface.

The combined effects of ultrasonic treatment and fast cooling on the bulk hydrogen content, the refinement of α-Al grains and θ-Al2Cu precipitated phase in the 2219 Al alloy were investigated in th...