Effect Of Hydrogen Absorption Research Articles

The effects of hydrogen absorption in U3Si5 and its thermodynamic properties

The hydrogen absorption behavior of ▪ was examined using a Sieverts apparatus. Experimental results revealed the formation of a hydride phase with a stoichiometry reaching ▪ at pressures up to 250 kPa and temperatures below 300°C. By employing Van 't Hoff analysis, the enthalpy and entropy of formation for the newly formed hydride phase were measured as -19.73 kJ⋅mol−1 and -251.18 J⋅mol−1⋅T−1, respectively. Rietveld refinement showcased an expansion in lattice parameters a and c, resulting in an overall increase in unit cell volume of up to 8%; volume expansion can induce structural failures within the material.

Irradiation growth behavior and effect of hydrogen absorption of Zr-based cladding alloys for PWR

In order to understand the dimensional stability of the fuel rod during long-term use in commercial LWRs, irradiation growth testing on various Zr-based fuel cladding materials including improved Zr-based alloys was conducted in the Halden reactor in Norway under prototypic irradiation and corrosion environment. The effect of hydrogen absorbed in the cladding tube due to corrosion on the irradiation growth behavior was investigated in this paper. The comparison of specimens with or without pre-charged hydrogen (about 200 and 400 ppm) revealed that the effect of hydrogen absorption, i.e. the acceleration of irradiation growth, became significant when the hydrogen content exceeded the hydrogen solubility limit in the corresponding irradiation temperature. Based on this understanding, the growth acceleration effect was evaluated to be (0.06 ± 0.01)%/100 ppm, with the denominator defined as the amount of absorbed hydrogen involved in hydride precipitation under irradiation as a relevant parameter. Discrimination of hydrogen effect confirmed lower irradiation growth of the improved Zr-based alloys than the conventional Zry-4, which may be attributed to the effect of lower hydrogen absorption property for Nb addition specimens.

Hydrogen absorption in solution/mill annealed Alloy 600 at room temperature H2SO4 and high-temperature pressurized water

Solution/mill annealed Alloy 600 samples were cathodically polarized in a H2SO4 solution and 300 °C water. The effect of hydrogen absorption on the microstructure and oxides of the alloys was investigated. Carbon crystallization in the polarized mill annealed alloy reduced the solubility of hydrogen in this alloy and increased its mechanical strength. Hydrogen charging on the solution/mill annealed alloys at 300 °C pure water increased the oxide thickness. Compared to the uncharged alloys, in the 300 °C hydrogenated primary coolant hydrogen modified the oxides of the solution/mill annealed alloys to a Cr-rich inner/Ni-rich outer layer and a Cr-rich outer/Ni-rich inner layer oxide, respectively.

Effects of hydrogen absorption on magnetism in Ni80Fe20/Y/Pd trilayers

The effects of hydrogen absorption on the effective magnetization $(4\ensuremath{\pi}{M}_{\mathrm{eff}})$, gyromagnetic ratio $(\ensuremath{\gamma})$, Gilbert damping constant $({\ensuremath{\alpha}}_{\mathrm{G}})$, and the inhomogeneous linewidth broadening $(\mathrm{\ensuremath{\Delta}}{H}_{0})$ in $\mathrm{Py}(x)/\mathrm{Y}$(16 nm)/Pd(15 nm) trilayer films ($x=2$, 3, 5, 8, 10, 20, 40 nm) were investigated with ferromagnetic resonance (FMR), transmission electron microscopy, and vibrating sample magnetometry. In the presence of a hydrogen atmosphere, the samples show a reduction of their FMR linewidth which is found to stem purely from a reduction of the inhomogeneous linewidth broadening. This is attributed to a rearrangement of atoms at the Py/Y interface in the presence of hydrogen, making the Py/Y interface more homogeneous. In addition, a reduction of $4\ensuremath{\pi}{M}_{\mathrm{eff}}$ was seen for all samples in the hydrogen atmosphere which is typical for an increase of the interfacial perpendicular magnetic anisotropy at the Py/Y interface.

On the electrochemical hydrogenation of Nb: An insight into the effect of hydrogen absorption on the kinetics of the hydrogen evolution reaction

The electrochemical hydrogenation (galvanostatic charging) and desorption (potentiostatic discharging) of Nb in an alkaline solution was investigated, using Pd as a reference model system. The phases formed during hydrogenation and those present after desorption were investigated by X-ray diffraction (XRD). The cathodic charging induced the formation of NbH0.89 and NbH2 for Nb and PdH0.6 for Pd. Nb hydrides appeared to be irreversibly formed, unlikely to the PdH0.6 that spontaneously decomposed back into Pd. The irreversible character of absorption process in Nb is likely to be related to oxide/hydroxides formation on the electrode surface in the alkaline media, which might hinder the dehydrogenation reaction. The electrochemical behavior was evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results were analyzed according to both thermodynamic and kinetic approaches. EIS results indicated that Pd and Nb have very similar hydrogen evolution reaction (HER) kinetic parameters. A theoretical development based on the different kinetic contributions to the overall charge-transfer resistance, including the absorption step's indirect contribution, is presented.

Measurement and analysis of effective thermal conductivity of LaNi5 and its hydride under different gas atmospheres

In this work, an ETC measurement cell based on the steady-state radial heat flow method was fabricated, and its reliability was validated by a commercial instrument. The ETCs of unactuated and activated LaNi5 powder beds were measured under various filling gases in the pressure range from 0.1 to 1.5 MPa. The experimental results show that the ETC of activated LaNi5 powder is much lower than that of the unactuated material due to the pulverization effect. The ETCs of unactuated and activated LaNi5 powder in helium atmosphere lie in the ranges of 1.04–1.63 W m−1 K−1 and 0.49–0.85 W m−1 K−1, respectively. Furthermore, the ETC increases with the increasing pressure and thermal conductivity of filling gas. The effects of hydrogen absorption and desorption on the ETC were investigated by step-by-step reaction, which depend mainly on the hydrogen concentration and expansion/constriction of MH particles.

Effect of hydrogen embrittlement towards thermal and mechanical behavior of NiTi shape memory alloy

NiTi arch wires are susceptible to hydrogen embrittlement upon contact with dental brackets in oral cavity during orthodontic treatment. This study investigated the effect of hydrogen absorption and diffusion over time towards the thermal and mechanical properties of NiTi shape memory wire. The hydrogen absorption process was carried out via electrolytic charging at constant current density for 16 hours in 1.0 weight percent (wt.%) sodium sulphate solution. The hydrogen charged wires were aged at room temperature in air for different durations to allow further inward diffusion of the hydrogen into the specimens. The results show that after hydrogen charging, the latent heat of forward and reverse martensitic phase transformation of the NiTi wire changed from 19.96 to 11.98 J/g, and 19.21 to 13.42 J/g, respectively. Further suppression and disappearance of thermal transformation peaks were observed as the charged specimen aged for 7 days. The transformation stress level on tensile deformation increased by almost 90 MPa after hydrogen charging, and exhibited non-flat stress plateau after further aging.

Effect of Hydrogen Absorption on the Composition of the Amorphous Alloys Surface Layers

Hydrogen absorption leads to redistribution of the components of the surface layer of the amorphous alloy Fe73.8Si12.7B9.4Nb3.2Cu noncontact side, while the amorphous structure of this layer is preserved. The type of the micro-groups Fey Six changes in such a way that the ratio y: x decreases (to less than 1) and the chemical bond polarity decreases, as well. After degassing, the surface layer composition becomes similar to those before hydrogenation. The loss of the mechanical stability of the amorphous ribbon is accompanied by the formation of the micro-groups Fey Six with a decreased ratio of y: x.

Influence of Hydrogen Absorbtion on the Emission Properties of Carbon Nanotubes

We present the results of experimental studies of the effect of hydrogen absorption on the emission properties of a charge source based on carbon nanotubes. It is determined that the emission properties of the source improve considerably after exposure in hydrogen atmosphere at pressure of 100 atm and temperature of 300°С for 2 hours: at voltage of 300 V the current of negative charges increases by 104 times.

Quality Of Restored Steel Gas Pipes For Re-Application In Construction

The structure and mechanical properties of eight steel gas pipeline single-seam and double-seam pipes that were in operation were studied. It is shown that the degree of corrosion damage to pipe surfaces depends on the chemical composition of the steels. In the studied steels, a significant variation in the hydrogen content between neighboring volumes and the studied pipes was revealed. According to electron-fractographic analysis , there is no significant difference in the degree of embrittlement of the base metal, the weld and the zone of thermal influence. A noticeable effect of hydrogen absorption of steels on the coefficient of anisotropy of the impact toughness has been established, which causes a decrease in the impact toughness on transverse samples to a greater extent than on longitudinal ones. According to the results of mechanical tests for tensile and impact bending, it was found that the restored welded pipes are suitable for use in structures from the first to the fourth groups for the construction, repair and reconstruction of industrial and civil facilities. Naturally, this implies the need for their restoration repair.

The Effect of Hydrogen Absorption on the Passivity of Oxides on Carbon Steels

Pipelines are designed for a wide variety of applications. Their use in the energy sector for the transportation of crude oil, natural gas, and other petrochemical commodities is still regarded as the safest, fastest and most economical mode of product transmission and delivery. The degradation of the structural integrity of pipelines caused by corrosion has been an on-going problem. Depending on in-service use, different forms of corrosion can occur, with the deleterious effects depending on which type of corrosion is occurring, such as stress corrosion cracking (SCC) and hydrogen induced cracking (HIC) due to hydrogen embrittlement (HE). Further, the hydrogen may affect the protectiveness of any FeIII oxide present on the steel surface. This study investigates the effects of H absorption by X60, X65, X70 steels. A range of electrochemical techniques, such as monitoring the corrosion potential (Ecorr), polarization resistance (Rp) measurements, cyclic voltammetry (CV), and H permeation experiments (using the Devanathan-Stachurski (D-S) approach) have been used to investigate the effect of H on the steel and the oxides present on the steel surface. Surface analytical techniques such as X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used to determine the effect of H on the composition of the oxide and to identify the distribution of H trapping sites. The apparent diffusivity of H in X65 was found to depend on the composition of the solution on the reduction side of the D-S cell. The steady-state current measured in the oxidation cell was dependent on the solution composition in the reduction cell. The presence of calcium caused a sharp decrease of oxidation current, likely due to the quick formation of calcium carbonate deposits, whereas magnesium caused a gradual decrease in the observed oxidation current, which is likely due to the thickening of the magnesium hydroxide on the surface. The presence of both calcium and magnesium in the solution affects the amount of H that diffuses through the steel, likely by blocking adsorption sites on the steel surface. Blocked adsorption sites reduce the concentration of atomic hydrogen on the surface and lead to a decrease in the observed steady-state current. Thermal desorption data show that, in the X65 steel, a majority of the H trapped within the steel requires activation energy (Ea) of < 50 kJ/mol for its release, indicating that it is located in reversible trapping sites. SIMS data suggest that trapping occurs predominantly along grain boundaries, with the extent of H trapping at these sites possibly affecting the resistance of the surface FeIII oxides present. The RP values measured after cathodic charging for the pearlite-containing steel (X65) were lower than those obtained on the bainite-containing steel (X70). The presence of FeO on the steel surface after cathodic charging suggests partial oxide reduction, with this reduced oxide being more prominent on the X65 than on the X70 steel. Polarization resistance measurements were used to study the role of hydrogen on the passivity of the steel covered by iron oxides. It has been shown that at open circuit conditions the increase in RP value is slower when the steel has been charged with H. The phase of X70 being investigated was predominantly bainite, which is more resistive to hydrogen absorption. X70, after hydrogen charging, was found to have a lesser change in steady-state RP than did the X65. Further, the retardation of the resistance increase at open circuit was more prominent on the X65 than on the X70. XPS confirmed that more FeO was present on the X65 sample after charging than on the X65 after charging followed by potentiodynamic polarization experiments. All this suggests that, at open circuit conditions after the steel was charged with H, hydrogen being released from reversible trapping sites reduces the FeIII oxide to FeO. The reduction of FeIII to FeO, due to either the charging or release of atomic hydrogen trapped within the lattice, is likely causing a decrease in the resistance of the passive oxide.

Flow hydrogen absorption of LaFe10.9Co0.8Si1.3 compound under constant low hydrogen gas pressure

The hydrogen absorption of the LaFe10.9Co0.8Si1.3 compound under constant 1.01 × 105 Pa H2 gas in a flow hydrogen atmosphere was studied. The effects of hydrogen absorption on structure, Curie temperature, phase transition and magnetic property were investigated by X-ray diffraction (XRD), differential scanning calorimeter (DSC) and superconducting quantum interference device, respectively. The hydrides of LaFe10.9Co0.8Si1.3 crystallize into NaZn13-type structural phase after hydrogen absorption at temperature from 548 to 623 K. Lower hydrogen absorption temperature is of no advantage for pure 1:13 phase formation in a flow H2 atmosphere. The Curie temperature (TC) of LaFe10.9Co0.8Si1.3 compound increases by 70 K or more after hydrogen absorption. For LaFe10.9Co0.8Si1.3H1.8 compound, the maximum magnetic entropy change and the relative cooling power under a magnetic field change of 0–2 T are 6.1 J·kg−1·K−1 and 170 J·kg−1, respectively. Large refrigerant capacity, low hysteresis loss and wide temperature span of magnetic entropy change peak make it a competitive practical candidate for magnetic refrigerant.

Hydrogen Absorption of LaFe10.9Co0.8Si1.3 Compound under Low Hydrogen Gas Pressure

The effects of hydrogen absorption on structure, Curie temperature and phase transition property for the LaFe10.9Co0.8Si1.3 compound are investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC) in a 1-atm H2 gas. The original compound and hydride present cubic NaZn13-type structure. The Curie temperature of LaFe10.9Co0.8Si1.3 shifts from 277K to 346K and temperature range of the phase transition becomes wider significantly after hydrogen absorption.

Thermal stability and hydrogen-induced softening in Zr57Al10Cu15.4Ni12.6Nb5 metallic glass

The effects of hydrogen absorption on the structure, mechanical and thermal properties of Zr57Al10Cu15.4Ni12.6Nb5 amorphous metal were investigated. Structural analysis, using X-ray diffraction, showed that prominent peak shift towards lower angles (from 37.55° to 37.47°) after 1h of hydrogen charging in 0.1M NaOH solution which indicates a volume expansion of the amorphous structure. By means of nanoindentation tests, we found that hydrogen-induced glass plasticity could occur in Zr-based metallic glass even for high Zr content (>50at.%). The thermal stability against crystallization, evaluated by differential scanning calorimetry (DSC), has been improved by hydrogen absorption. The onset crystallization temperature was increased by 6°C to 10°C due to slight hydrogen addition. The resistance to hydrogen embrittlement combined with high thermal stability gives rise to the possibility of the practical use of Zr57Al10Cu15.4Ni12.6Nb5 amorphous alloy as a good metal membrane operating at temperatures below 400°C.

Hydrogen Absorption in Metal Thin Films and Heterostructures Investigated in Situ with Neutron and X-ray Scattering

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.

Hydrogen embrittlement behavior of Ni-Ti shape memory alloy with different microstructures in acidic fluoride solution

It is important to investigate the mechanism for the hydrogen embrittlement of Ni-Ti alloys in acidic fluoride solutions to improve the reliability and safety of these alloys as dental devices. Therefore, the hydrogen embrittlement behavior of Ni-Ti shape memory alloy immersed in acidic fluoride solution was investigated with a focus on the constituent phase in the microstructure of the alloy in this study. Three microstructures with different phases (parent single phase, mixture of parent and martensite phases, and martensite single phase) were prepared by tensile loading and unloading. The specimens were immersed separately in 50 mL of 0.2 % acidulated phosphate fluoride (APF) solution with pH 5.0 at room temperature (25 °C) for various periods. After immersion for 2 h, the tensile strengths of all the specimens were not significantly changed with respect to those of the non-immersed specimens. After immersion for 4 h, the tensile strengths of all the specimens immersed were decreased with respect to those of the non-immersed specimens, and the tensile strength of the martensite single phase specimen (C) was higher than that of parent single phase specimen (A) and the parent/martensite mixed phase specimen (B). After immersion for 6 h, the tensile strengths of all the specimens were decreased with respect to those of the specimens immersed for 4 h, and the tensile strength of specimen B was lower than that of specimens A and C. The susceptibility to hydrogen embrittlement of the Ni-Ti shape memory alloy with a microstructure including the parent phase tends to be high when the degree of corrosion is not significantly different for the alloy microstructure. Moreover, the effect of corrosion on the tensile strength of Ni-Ti shape memory alloy is significant when the microstructure includes the martensite phase. Hence, the significant degradation of tensile strength observed for specimen B was probably caused by a synergistic effect of hydrogen absorption and corrosion.

Electrocatalytic Reduction of Nitrate on Tin-modified Palladium Electrodes

The electrocatalytic reduction of nitrate was investigated in acidic media on Sn-modified polycrystalline palladium and Sn-modified palladium film electrodes (deposited on gold) by means of voltammetry in combination with on-line electrochemical mass spectrometry and on-line ion chromatography. The catalytic activity for this reaction is strongly enhanced by modification with Sn as pure Pd is not found to have a measurable activity for the nitrate reduction. Dominant volatile products are found to be N2O and in a smaller amount N2, while NH2OH is found to be the dominant non-volatile product. Furthermore, the influence of hydrogen absorption in Pd is investigated by using a multilayer Pd film and a submonolayer Pd film on a polycrystalline Au electrode. By comparing the product distribution of these electrodes with the bulk Pd electrode the effect of hydrogen absorption is found to be of negligible importance for the nitrate reduction as the product distribution and formation as a function of potential are similar compared to the bulk Pd electrode.

Hydrogen Insertion Effects on the Electronic Structure of Equiatomic MgNi Traced by ab initio Calculations

Abstract For equiatomic MgNi which can be hydrogenated up to the composition MgNiH1.6 at an absorption/ desorption temperature of 200 °C, the effects of hydrogen absorption are approached with the model structures MgNiH, MgNiH2 and MgNiH3. From full geometry optimization and calculated cohesive energies obtained within DFT, the MgNiH2 composition close to the experimental limit is identified as most stable. Charge density analysis shows an increasingly covalent character of hydrogen: MgNiH (H-0.67) → MgNiH2 (H-0.63) ! MgNiH3 (H-0.55). While Mg-Ni bonding prevails in MgNi and hydrogenated model phases, extra itinerant low-energy Ni states appear when hydrogen is introduced signaling Ni-H bonding which prevails over Mg-H as evidenced from total energy calculations and chemical bonding analyses.

Pb nanowire formation on Al/lead zirconate titanate surfaces in high-pressure hydrogen

Piezoelectric systems are well known to degrade in hydrogen because of various mechanisms including loss of polarization, Pb migration into the electrode, and surface blistering. Understanding damage mechanisms is crucial for potential high-pressure applications such as injectors for hydrogen-fueled vehicles. In this paper, we report on a previously unreported form of high-pressure hydrogen damage resulting from growth of surface Pb nanowires from an Al electrode on lead zirconate titanate. Wires were observed with roughly 80 nm diameter and with length that varied between 5 and 100 μm. Microscopy to characterize the nanowires and ion-scattering measurements to quantify concurrent Pb surface migration and hydrogen absorption effects are described.

Mössbauer Study of the SmFe2Hydride through149Sm and57Fe

We have applied the nuclear resonant forward scattering of synchrotron radiation by 149 Sm and 57 Fe Mossbauer spectroscopy to SmFe 2 and c -SmFe 2 H x (\(x\lesssim 3\)), to study the effect of hydrogen absorption on local electronic states. The averages of the parameters of the hyperfine structure of SmFe 2 and c -SmFe 2 H x at 20 K are as follows: the electric quadrupole splitting parameters of 149 Sm are -10.3±0.3 and -8.3±0.3 mm/s, the magnetic hyperfine fields of 149 Sm are 299±8 and 326±8 T, the isomer shifts of 57 Fe are 0.07±0.03 and 0.41±0.03 mm/s, the electric quadrupole splitting parameters of 57 Fe are 0 and 0.15±0.03 mm/s, and the magnetic hyperfine fields of 57 Fe are 20.4±0.1 and 19.3±0.1 T, respectively. The differences in these parameters between SmFe 2 and c -SmFe 2 H x are discussed in connection with the modulation of local electronic states induced by lattice expansion and chemical effect of hydrogenation. The differences also imply the screening of interactions between Sm and Fe by i...