Hydrogen In Solid Solution Research Articles

The effect of hydrogen in solid solution on the magnetic transitions in thulium

The influence of hydrogen on the magnetic structures in thulium was determined by measuring the temperature dependence of the electrical resistivity up to 75 K. The H acts by lowering the Neel temperature and the spin-disorder resistivity, by smearing out the manifestation of the Curie temperature, and by revealing additional magnetic transitions below T C . This behaviour and the observation of an energy gap in the spin-wave spectrum are commented within the framework of the RKKY-model.

Electronic structure of the bcc transition metals: Thermoreflectance studies of bulk V, Nb, Ta, andαTaHx

Thermoreflectance studies of bulk samples of V, Nb, Ta, and $\ensuremath{\alpha}$-phase $\mathrm{Ta}{\mathrm{H}}_{x}$ are reported and the results interpreted in terms of recent band calculations. The first interband transition is identified as a transition involving the $\ensuremath{\Sigma}$ band at ${E}_{F}$. An ${M}_{3}$ critical-point transition is attributed to states at $N$. Significant changes induced by interstitial hydrogen in solid solution $\ensuremath{\alpha}\ensuremath{-}\mathrm{Ta}{\mathrm{H}}_{x}$ are observed and interpreted as due to hybridization and lowering of the ${N}_{1}$ eigenenergy.

タンタル単結晶の水素ぜい性

The effect of hydrogen on the ductility of tantalum single crystal was investigated in the temperature range of 77-396K using a variety of techniques including observation by the S.E.M., tensile testing, X-ray radiography, and electric resistivity methods. The solid solution of hydrogen in tantalum was shown to be highly ductile at temperatures above 300K. The ductility of the solid solutions decreased rapidly at temperatures below 300K, and was minimum at about 200K. The fracture mode was cleavage at the temperatures in the region of ductility minimum, while it was ductile at temperatures near 77K. The factors affecting the above embrittlement are considered to be inhomogeneous distribution of hydrogen in the specimen and formation of stress induced hydrides. The ductility near 77K may be caused by very slow diffusion of hydrogen at that temperature.

Constant-volume thermodynamic functions for b.c.c. niobium-hydrogen solid solutions

Recent measurements of the composition and temperature variation of the elastic properties of niobium single crystals containing hydrogen in solid solution in the b.c.c. α-phase have been used to calculate the rigid-lattice thermodynamic functions of the solution from the measured constant-pressure thermodynamic functions. The results show large differences between the two sets of functions. The utility of rigid-lattice models is discussed. Nous avons utilisé des mesures récentes de la variation en fonction de la composition et de la température des propriétés élastiques de monocristaux de niobium contenant de l'hydrogène en solution solide dans la phase α c.c., pour calculer les fonctions thermodynamiques à réseau rigide de la solution à partir des fonctions thermodynamiques de la solution mesurées à pression constante. Les résultats mettent en évidence de grandes différences entre les deux ensembles de fonctions. Nous discutons alors l'utilité des modèles de réseau rigide. Aufbauend auf neueren Messungen von Zusammensetzung und Temperaturabhängigkeit der elastischen Eigenschaften von Niobeinkristallen, die Wasserstoff in fester Lösung in der krz. α-Phase enthalten, wurden die thermodynamischen Funktionen der Lösung in der Näherung des starren Gitters aus den gemessenen thermodynamischen Funktionen bei konstantem Druck berechnet. Die Ergebnisse weisen groβe Unterschiede zwischen den beiden Funktionssätzen auf. Der Nutzen von Modellen starrer Gitter wird diskutiert.

Magnetic properties of hydrogen solid solutions in Fe–Ni–Mn alloys

The magnetization behaviour is investigated in a pulsed magnetic field up to 50 kOe at 80 ≦ T ≦ ≦ 220 K for hydrogen solid solutions in Fe65(Ni1–xMnx)35 invars containing 0, 4.5, 10, 17, 24, 29, and 35 wt% Mn. The alloys are enriched in hydrogen to hydrogen/metal atomic ratio n ⪅ 1 using exposures to PH2 ≦ 70 kbar. The Neel point behaviour is studied at PH2 ≦ 15 kbar for the 35% Mn alloy. The dependence of the parameter of the f.c.c. metal sublattiee on the hydrogen content is measured for the 29% Mn alloy at T = 83 K. The hydrogenation is shown to suppress the antiferromagnetic ordering in manganese-rich alloys. Above a certain hydrogen concentration nf, each of the studied Me–H solutions becomes ferromagnetic. The Curie points in the ferromagnetic state rise with n increase. At n ≈ 1, the spontaneous magnetization and Curie points of hydrogen solutions in Fe–Ni–Mn alloys reach magnitudes characteristic of Fe–Ni invars. [Russian Text Ignored].

An investigation of some palladium-titanium and some palladium-titanium-hydrogen alloys

The room temperature lattice spacings (of both powdered and solid samples), microhardness values and magnetic susceptibilities of some Pd-Ti alloys in the composition range 0−-30% Ti∗ have been determined in the present investigation. The lattice spacings of the solid samples indicate a small progressive contraction of the palladium lattice on adding titanium, apart from the composition range 7− -14.5% Ti where the spacing is invariant with composition. It is proposed that this plateau region in the spacing-composition variation is due to the compensatory effects of ordering and of progressive titanium additions. The variation of microhardness with titanium content can be correlated with the corresponding variation in the lattice spacings and both can be interpreted in terms of the appearance of short range order (SRO) and eventually long range order (LRO) in these alloys. The magnetic susceptibility measurements for the alloys up to about 9% Ti indicate an effective valency of 4.0 for the titanium atoms in solution in palladium. Alloys in the composition range 0−-8.7% Ti were gaseously charged with hydrogen and the results indicate that the equilibrium pressures for the hydrogen solid solutions increase rapidly with Ti content and are considerably higher than those for the equivalent Pd-Ce solid solution alloys. On hydrogenation the alloys become harder; this can be attributed to the influence of hydrogen on the atomic mismatch factor and, at certain compositions, to the additional effect of transformation hardening due to the α/β miscibility gap.

Hydriding behaviour of zircaloy-4/stainless steel type 304 diffusion couples

The behaviour of diffusion-bonded Zircaloy-4/ stainless steel junctions under thermal and electrolytic hydriding conditions was studied. The results showed that these junctions have the ability to absorb large amounts of hydrogen. The diffusion zone and most of the Zircaloy side, which was enriched with Ni, were transformed to complex hydrides. In the diffusion zone, the α-Zr phase and an intermetallic compound (phase X) formed hydrides after relatively short electrolytic hydriding times. Cr 2Zr, found in the diffusion zone, showed a large hydrogen solid solution behaviour with an increase of 18.4% in the lattice volume. A martensitic transformation in austenitic stainless steel was also observed. The detrimental effect of Ni in Zircaloy was interpreted in terms of the role played by Zr-Ni intermetallic compounds.

Study of the hydrogen solid solution in thulium

Solid solutions of hydrogen in thulium are investigated, mainly by X-ray determinations in the temperature range 20–500°C. Several observations lead us to distinguish between two variaties α and α ∗. In the range of existence of the α ∗ phase, below the transition temperature of 120°C, the hydrogen interstitials induce in the metal lattice a behaviour different from that of the α phase, as concerns the phase equilibrium, the additional resistivity, and the lattice anisotropy. Several simple models are proposed for the explanation of this anomaly, encountered also in other heavy rate earth-hydrogen systems.

Study of the hydrogen solid solution in thulium

Study of the hydrogen solid solution in thulium

Experimental studies of the crystallography of the precipitation of β vanadium hydride

The structure of the interface between β vanadium hydride plates and the parent b.c.c. solid solution of hydrogen in vanadium has been studied by transmission electron microscopy, and measurements have been made of the shape strain and orientation relationship. The results are generally in good agreement with the predictions of the phenomenological theory of martensitic transformations. The prediction that the interface dislocations generating the lattice invariant shear should be resolvable has been confirmed, and direct confirmation obtained of the hypothesis that the complementary shear system is {112} 〈 11 1〉. For the identity correspondence and specific shear system (112) B [ 11 1] R the predictions of the theory that the habit plane is near (2̄27) B and the displacement direction near [22̄7] B have been confirmed by the electron microscopy and the shape strain measurements. The measured magnitudes of both shape and complementary strains agree well with predicted values. Orientation determinations from Laue and Kossel patterns indicate that the [001] direction of the hydride is inclined to the (001) plane and are compatible with monoclinic hydride structures in which either χ or β is greater than 90°. However, measurements of the orientation relationship are generally in better agreement with predictions of the theory for structures with β 〉 90°.

The effect of low-temperature electron irradiation on lutetium and its hydrogen solid solutions

Lutetium metal and several Lu(H) solid solutions are irradiated with electrons in the energy range 0·4 to 1·7 MeV at liquid-helium temperatures. The threshold energy for the displacement of a Lu atom is determined to Td = (17 ± 1) eV, corresponding to an incident electron energy of Ed = (780 ± 30) keV. Displacement cross sections are fitted to the experimental data, with ϱ ≈︁ (60 to 90) μΩ cm/at% F.P. as Frenkel-pair resistivity. The defect production rates at 0·4 MeV of Lu(H) depend on the H-concentration in the α-phase. From their fluence dependence, the concentration dependent defect formation cross sections, σH = (2.35 to 4.18) × 106 barns, are deduced and the defect resistivities, ΔϱH = (36 to 41) μΩ cm/atom H. A comparison with calculated electron-hydrogen scattering cross sections permits to determine a threshold energy for the H-defect formation, TH = (0.06 to 0·09) eV, which, consequently, also varies with the H-concentration. A possible model assuming a paired hydrogen configuration as the stable low-resistivity form at low temperatures is suggested. Le lutetium métal et plusiers solutions solides Lu(H) ont été irradiés par des électrons d'énergie comprise entre 0,4 et 1,7 MeV à la température de l'hélium liquide. L'énergie seuil de déplacement d'un atome Lu est déterminée, cette valeur Td = (17 ± 1) eV correspondant à l'énergie d'électrons incidents Ed = (780 ± 30) keV. Les sections efficaces de déplacement calculées ont été comparées aux données expérimentales en prenant ϱF ≈︁ (60 à 90) × 10−4 Ω cm/F.P. pour la résistivité d'une paire de Frenkel. A 0,4 MeV, les taux de production de défauts dans Lu(H) varient avec la concentration de H dans la phase α. De leur diminution en fonction du flux électronique on déduit des sections efficaces de formation de défauts, σH = (2,35 à 4,18) × 106 barns, et des résistivités de défauts, δϱH = (36 à 41) μΩ cm/atome H, variant avec la concentration. La comparaison avec les sections efficaces d'intéraction électron-hydrogène calculées permet de déterminer l'énergie seuil pour la création de défaut H, TH = (0,06 à 0,09) eV, qui varie done aussi avec la concentration de H. On envisage un modèle où la configuration des atomes H en paires est supposée la forme stable et peu résistante à basse température.

Dependence on solution composition and temperature of the diffusion and permeability coefficients of hydrogen in solid solutions of germanium in iron

Dependence on solution composition and temperature of the diffusion and permeability coefficients of hydrogen in solid solutions of germanium in iron

Thermodynamics of solid solution of hydrogen in M2C type carbides of vanadium and niobium

Equilibrium hydrogen pressures in the systems V 2CH 2 and Nb 2CH 2 have been determined at several temperatures in the range 400–650°C. Hydrogen pressure data were treated to obtain various thermodynamic quantities for the solutions of hydrogen in V 2C and Nb 2C. It has been found that the enthalpies of the reaction H(S.S.) = 1 2 H 2( g) are similar but slightly less endothermic compared to the respective metal hydrogen solid solutions. Entropies of dissolved hydrogen in V 2C and Nb 2C are also found to be similar to those of hydrogen in the respective metals.

The thermodynamic functions of hydrogen in solid solutions of the group V metals Nb, Ta and V

The large volume of available data for the isotherms characterizing the dissolution of H from H 2-gas into the Group V metals Nb, Ta and V has been reviewed. Both the temperature and composition variation of the partial molar and relative partial molar enthalpies and entropies have been discussed in terms of theoretical models in which the H-atoms in solution can possess degrees of translational freedom. The relative invariance of the relative partial enthalpy Δ H u to temperature and the change in H u with temperature are in accord with this concept. The variation of H u with solute composition has been used in conjunction with recent elastic data for HNb, HTa and HV solid solutions to discuss the form of the HH interaction in these systems.

The 55 K specific heat anomaly in palladium hydride

A specific heat anomaly in PdH and PdD has been observed by Aston et al. (1957) close to 55 K. Its position was found to be independent of hydrogen concentration and its magnitude to be linear in hydrogen concentration. Ferguson's (1965) and Brodowsky's (1972) explanations of the anomaly are shown to be unsatisfactory. This is true also for the detailed mechanical statistical model proposed by Staford and McLellan (1974) for interstitial solid solutions of hydrogen in transition metals. It is shown that Gopal's (1966) simple Schottky model of specific heat anomaly, which considers a system of several levels with Boltzmann statistics, provides much better agreement with experiment than the more elaborate models, both in magnitude and in predicting a linear dependence on hydrogen concentration.

Spin fluctuations and superconductivity (properties of PdH solutions)

Using a self-consistent treatment of deformation, Coulomb, and exchange effects within the isotropic approximation, a criterion for superconductivity of metals is obtained ps2<N2vFx0x, where ρs2 = c11 is the lattice elastic coefficient, N is the electron concentration, νf is the electron density of states at the Fermi surface, χ is the spin paramagnetic susceptibility of the metal, and χ0=μB2vF is the Pauli paramagnetism. This criterion applies not only to nontransition, but also to transition metals with strong exchange interactions (though not including interband transitions). This is demonstrated on the example of the appearance of superconductivity in solid solutions of hydrogen in palladium PdHx when the hydrogen concentration x is varied.

A statistical mechanical model for solid solutions of hydrogen in the metals niobium, vanadium and tantalum

Abstract A model for hydrogen-metal solid solutions has been discussed in which the H-atoms are bound to interstitial sites in the solvent metal lattice in a loose manner. Only at low temperatures do they act as bound oscillators. At a higher temperature the solution undergoes a transformation in which the H-atoms gain translational degrees of freedom. This is akin to the formation of a mobile adsorbed layer except that three dimensions are involved. This model has been used to calculate the partial thermodynamic functions of the H-atoms in the solution. The calculated quantities have been compared with measured experimental data for H-Nb, H-Ta, and H-V solid solutions. Despite simple assumptions made in regard to the form of the H-H interactions in the solution, the agreement between the calculated and measured quantities is good.

Thermal stability of a solid solution of hydrogen in certain transition metals

Thermal stability of a solid solution of hydrogen in certain transition metals

Statistical mechanical models for interstitial solid solutions of hydrogen in Nb, V and Ta

Statistical mechanical models for interstitial solid solutions of hydrogen in Nb, V and Ta

The solubility and trapping of hydrogen in vanadium

Solid solutions of hydrogen in vanadium are affected greatly by the presence of other interstitials carbon, nitrogen and oxygen. The solutions depart drastically from randomness at low temperatures and the solvus line is pushed to higher equilibrium hydrogen concentration as the concentration of these interstitials is increased. Utilization of internal friction and resistivity measurements permits this effect to be measured quantitatively. Two explanations are examined to interpret the results: (1) an effect of mechanical constraint of the matrix on the precipitate which acts to retard its growth. (2) an effect of clusters of hydrogen with C, N or O to alter the equilibrium concentration of hydrogen in the free lattice, thereby altering the effective supersaturation of hydrogen. The first is considered to be inadequate to explain the full magnitude of the effect. The second can explain the effect in detail if the multi-atom clusters are assumed to exist in relatively high concentration, that is, if the binding energy per hydrogen atom is very much greater than kT.