Solubility Of Deuterium Research Articles

Deuterium accumulation in deposited tungsten films

The accumulation and retention of hydrogen isotopes in the deposited films that are formed as a result of ion sputtering of the plasma-facing materials of tokamaks is a topical problem in fusion. In the research described here, the accumulation of deuterium in tungsten films under deuterium plasma irradiation was studied. Tungsten films 50 nm in thickness were deposited on substrates with different deuterium solubilities (W, Ni, Cu). The profiles of deuterium concentration in near-surface layers were determined by means of secondary ion mass spectrometry and residual gas analysis. It is shown here that deuterium concentrations in tungsten films deposited on different substrates are the same, and are higher than those in polycrystalline tungsten by a factor of ∼2. The total amount of retained deuterium depends on the substrate material. In the W–W system it is higher than that in W–Ni and W–Cu systems. The effect of oxide films on deuterium accumulation is also discussed.

Interaction between Water and Ceria-Zirconia-Yttria Solid Solutions

We have investigated the water solubility, oxygen isotope diffusivity, and oxygen surface exchange coefficient in a humid atmosphere of the system {(CeO2) x (ZrO2)1−x}0.8(YO1.5)0.2 (x = 0–1) by using isotope exchange and secondary ion mass spectrometry (SIMS). The deuterium ion (2D−) was detected from the {(CeO2) x (ZrO2)1−x}0.8(YO1.5)0.2 polycrystals which were annealed in D2O containing atmosphere. The solubility of deuterium in the polycrystals increased with the cerium content (x). The oxygen exchange rate constant (α) in air at T = 973 K shows a maximum at x = 0.2–0.3, which can be correlated to the compositional dependence of electronic conductivity of {(CeO2) x (ZrO2)1−x}0.8(YO1.5)0.2. The effect of water on the surface exchange rate constant was more significantly observed for the samples with higher content of cerium x > 0.6.

Strain Gradient Influence on Diffusion Coefficients of Deuterium in Absorption and Desorption of Deuterium in Pd81Pt19 Membrane

The diffusion of deuterium through a Pd81Pt19 membrane was investigated. At six temperatures in the range 278.2-328.2 K the diffusion coefficients were determined by breakthrough method for the membrane with no initial content of deuterium. The determined activation energy of diffusion of deuterium equals E = 26.4 kJ/mol. The solubility of deuterium in Pd81Pt19 alloy at 278.2 K was measured by volumetric method. The influence of self-stresses on diffusion of deuterium was investigated by determination of diffusion coefficients for the Pd81Pt19 membrane with different initial contents of deuterium at 278.2 K.

Equilibrium state of hydrogen in gallium nitride: Theory and experiment

Formation energies and vibration frequencies for H in wurtzite GaN were calculated from density-functional theory and used to predict equilibrium state occupancies and solid solubilities at elevated temperatures for p-type, intrinsic, and n-type material. The solubility of deuterium (D) was measured in p-type, Mg-doped GaN at 600, 700, and 800 °C as a function of D2 pressure and compared with theory. Agreement was obtained by reducing the H formation energies 0.22 eV from ab initio theoretical values. The predicted stretch-mode frequency for H bound to the Mg acceptor lies 5% above an observed infrared absorption attributed to this complex. More limited solubility measurements were carried out for nominally undoped material rendered n-type by donors provisionally identified as O impurities, and results agree well with theory after the aforementioned adjustment of formation energies. It is concluded that currently recognized H states and physical processes can account for the equilibrium, elevated-temperature behavior of H examined in this work.

Deuterium solubility and electrical resistance of palladium-rhodium alloys

The deuterium solubility and the corresponding change in electrical resistance of Pd-5.0 and -10.0 at.% Rh alloys have been investigated at different temperatures by a gas phase method. In these studies, a decrease in low pressure deuterium solubilities and increase in plateau pressures with increasing Rh content have been observed. The decrease in lattice size with increasing Rh content seemed responsible for it. The miscibility gap decreased with increasing Rh content. Higher deuterium solubility was attained for lower Rh content alloy. The studied systems showed remarkable p-c hysteresis. The loss in energy due to hysteresis for the Pd-10.0 at.% Rh–D system showed lower values than that of the Pd-5.0 at.% Rh–D system. The α max resistance values are gradually decreased with increasing Rh content and increased with increasing temperature. The initiation of β deuteride creates pronounced lattice deformation and R/ R 0 values increased sharply. For a higher Rh content alloy, the increase in R/ R 0 values during β hydride initiation is higher, probably for its smaller lattice size. At higher temperatures, a lowering of resistance occurred when the system entered from a coherent state to an incoherent state. In the main plateau region, the change in R/ R 0 showed small values. From D/M content of about 0.55, a pronounced lowering of resistance, was observed, probably due to approaching of the β phase structure to a NaCl type lattice. Remarkable resistance hysteresis was observed at the studied temperatures. For the Pd-5.0 at.% Rh–D system a larger resistance hysteresis appeared than that of the Pd-10.0 at.% Rh–D system. Larger lattice expansion and the creation of higher lattice deformation in the β phase region due to a higher amount of deuterium absorption seemed responsible for it. The R/ R 0-c behavior showed a good similarity with that of their hydrogen system found by the same method, but dissimilar to that reported by the electrochemical method.

The effect of a nitrogen-rich surface layer on the sub-surface deuterium (hydrogen) concentration distribution in titanium

Deuterium and nitrogen depth profiles in Ti with modified surfaces have been measured with Auger electron spectroscopy, secondary ion mass spectroscopy, and D( 3He,p) 4He nuclear reaction analysis. Nitrogen-rich surfaces layers of varying thicknesses were created on Ti by exposure to N 2 gas at 650°C. Deuterium loading was performed by exposure to 1 Torr of D 2 gas at 500°C. The deuterium distribution was influenced by nitrogen in the near-surface regions of all samples. Specifically, deuterium solubility was suppressed in surface regions of high (greater than 1%) nitrogen concentration. The deuterium solubility also remained low within the first few microns, well beyond the region of high nitrogen concentration. This effect is attributed to internal elastic stresses imposed by the non-deuterium absorbing nitrogen-rich layer on the Ti. These stresses prohibit the volume expansion associated with deuterium absorption. We estimate stresses on the order of 3–4 GPa are required to suppress the deuterium solubility to the values observed. The deuterium absorption kinetics were observed to depend systematically on the thickness of the nitrogen-rich layer. This is consistent with limited solubility near the surface or a surface poisoning effect influencing the overall deuterium diffusion from the gas phase into the Ti bulk.

Dipole moments ofH2,D2,and HD molecules in Czochralski silicon

Measurements show that the effective charge $\ensuremath{\eta}({\ensuremath{\nu}}_{3\mathrm{D}\mathrm{D}})$ (dipole moment per unit displacement) of the infrared (IR) active stretch mode of isolated interstitial ${\mathrm{D}}_{2}$ molecules is smaller than $\ensuremath{\eta}({\ensuremath{\nu}}_{3\mathrm{H}\mathrm{H}})$ for ${\mathrm{H}}_{2}$ molecules in Si crystals. This may relate to differences in the orientations of the molecular axes that are not in general parallel to the direction of the dipole moments. For molecules paired with an interstitial oxygen atom in Czochralski Si, i.e., $({\mathrm{D}}_{2}({\mathrm{H}}_{2})\ensuremath{-}{\mathrm{O}}_{i})$ (two configurations of each), the effective charges $\ensuremath{\eta}({\ensuremath{\nu}}_{1\mathrm{D}\mathrm{D}})$ and $\ensuremath{\eta}({\ensuremath{\nu}}_{2\mathrm{D}\mathrm{D}})$ are essentially equal to $\ensuremath{\eta}({\ensuremath{\nu}}_{1\mathrm{H}\mathrm{H}})$ and $\ensuremath{\eta}({\ensuremath{\nu}}_{2\mathrm{H}\mathrm{H}}),$ respectively. No information has been obtained for the effective charges of the three ${\ensuremath{\nu}}_{\mathrm{HD}}$ modes. For samples heated in a mixture of $[{\mathrm{H}}_{2}]=[{\mathrm{D}}_{2}],$ the ratios of the concentrations of $[{\mathrm{H}}_{2}]:[\mathrm{HD}]:[{\mathrm{D}}_{2}]$ are expected to be 1:2:1 but the derived concentrations of [HD] are always too small, although $[{\mathrm{H}}_{2}]$ is essentially equal to $[{\mathrm{D}}_{2}].$ Measurements show that the solubilities of hydrogen and deuterium at 1300 \ifmmode^\circ\else\textdegree\fi{}C are equal and both vary as ${p}^{0.56},$ where p is the partial pressure of the gas that is mixed with argon. It is inferred either (a) that the dipole moments of HD molecules in the three locations are all anomalously small or (b) that the concentrations of [HD] are significantly smaller than expected from random pairing of H and D atoms during cooling following the heat treatment. A proposal that \ensuremath{\sim}70% of the hydrogen and deuterium is introduced into the Si in the form of correlated H-H and D-D pairs at 1300 \ifmmode^\circ\else\textdegree\fi{}C removes the discrepancy (b) but is unlikely as there is then conflict with the measured pressure dependencies of the hydrogen and deuterium solubilities.

SANS measurements of deuteride (hydride) formation in single crystal Pd

Abstract In situ small-angle neutron scattering (SANS) measurements of deuteride precipitation in well-annealed, undeformed single crystal Pd have been performed at room temperature to observe the morphology of the precipitate as the deuterium fraction was increased over a range of 0.005 to 0.097 [D]/[Pd]. Supporting measurements were made of the room temperature deuterium solubility isotherm in the single crystal material and of the progressive lattice mosaic broadening by gamma-ray diffraction analysis. The use of single crystal material eliminated the effect of grain boundaries on the precipitation process and allowed the orientation of the deuteride precipitates relative to the host Pd lattice to be established. The SANS data for deuterium loading beyond the solid solution phase are dominated by a d Σ /d Ω ∼ Q −2 scattering response well fit by a model cross section of small plate-like precipitates with a thickness of 25–30 A. This response showed little indication of a preferred habit plane and the plate thickness was independent of the total deuterium loading. The volume fraction of these small plates grew uniformly with increased deuterium loading, but was surprisingly small, reaching only 8×10 −5 at 0.060 [D]/[Pd]. This means that almost all of the deuterium resides in some other precipitate structure. The SANS data in the lowest Q region showed a second, anisotropic scattering component that can be interpreted as the Porod tail from plate-like particles of grossly larger dimensions. These plates favor a (001) α habit plane, normal to the elastically soft [001] α direction. Post-measurement visual inspection of the sample surfaces showed the presence of an oriented, quasi-periodic one-dimensional array of plates with thicknesses of approximately 0.1 to 0.2 mm and with an orientation in agreement with the anisotropy of the SANS data. We conclude that most of the deuteride phase precipitates in these large structures.

Deuterium phase behavior in thin-film Pd

The absorption of deuterium from the gas phase into two Pd thin films 668 \AA{} and 1207 \AA{} thick was measured at room temperature with in situ neutron reflectometry. Room-temperature solubility isothermal curves, out-of-plane film expansion, and deuterium depth profiles were determined from fits to the neutron reflectivity data. The measurements demonstrate that the deuterium solubility behavior, both in solid solution and within the two-phase region, is strongly perturbed by the thin-film geometry, consistent with previous solubility measurements in the published literature. The phase behavior investigated here was observed to depend on film thickness and on deuterium cycling through the two-phase region. The 668-\AA{} film exhibited the greatest initial phase perturbation and most significant changes upon cycling. Upon repeated cycling, both films approach nearly identical deuterium isothermal solubility and out-of-plane expansion behaviors. The observed equilibrium out-of-plane expansion behavior was consistent with the films expanding under an in-plane clamping constraint imposed by the substrate. The effect of this substrate constraining force is to amplify the out-of-plane expansion beyond that expected in bulk Pd. Taken together, these measurements implicate the film/substrate interfacial clamping interaction as the origin of the perturbed hydrogen phase behavior in thin-film geometry.

Applicability of palladium membrane for the separation of protium and deuterium

Separation of protium and deuterium using a palladium membrane was investigated under temperature and pressure conditions involving a phase transformation of the metal. The H D flux ratio for single-component systems showed a maximum of 7–8, when the membrane surfaces on the supply and permeate sides were in the β- and α-phases, respectively, for protium, and when both surfaces were in the α-phase for deuterium. The large difference in solubility of protium and deuterium in palladium was responsible for the high selectivity. For a mixture of H 2 and D 2, the H D ratio in palladium was expressed by an equation similar to Raoult's law. The H and D fluxes were lower than those for single component systems, and the H D separation coefficient was 1.2–1.3.

On the behavior of deuterium in ultrathin SiO2 films upon thermal annealing

Following the observation of the large isotopic effect in D2 passivated gate dielectrics [J. Lyding, K. Hess, and I. C. Kizilyalli, Appl. Phys. Lett. 68, 2526 (1996)], we studied the behavior of deuterium in ultrathin SiO2 films by nuclear reaction analysis techniques. Accurate concentrations of deuterium in the films, deuterium depth distributions, and deuterium removal from the film upon thermal annealing in vacuum have been examined. For D2 passivated films, we found rather high concentrations of deuterium near the SiO2/Si interface, well above both the solubility of deuterium in silica and the maximum concentration of electrically active defects at the interface. Our results suggest a complex multistep mechanism of thermally activated deuterium removal from the film, which probably consists of D detrapping, diffusion, and desorption steps.

Effects of the solid-solid interface on the thermal behavior of deuterium in zircaloy cladding tubes

Using nuclear reaction analysis (NRA), experimental studies on diffusion and absorption of hydrogen isotopes in zircaloy were conducted. These thermal behaviors would be influenced by solid-solid interfaces such as zirconium-zircaloy in liner tubes of nuclear fuel elements and impurity-zircaloy on the cladding surfaces. A specimen of Zr-liner Zircaloy-2 cladding was thermally charged with deuterium gas and slowly cooled in the gas. NRA showed that deuterium highly accumulated in the side of zirconium near the interface, and the deuterium concentration in Zircaloy-2 became lower. This indicated that the deuterium redistribution occurred due to the deuterium migration toward the Zr-liner during slow cooling. This redistribution may be explained by a slight difference of temperature dependence of the terminal solubility of deuterium between zirconium and Zircaloy-2. The observed profile of deuterium may suggest the distribution of tritium in stored spent fuel claddings. Another experiment was to observe the deuterium concentration in Zircaloy-4 tubes, of which impurity elements were present on the surface. Before sample specimens were charged with deuterium gas, nickel or iron was deposited in vacuum, mechanically rubbed, or implanted to them. It was found that effects of the impurity-zircaloy interface much depended on the way of impurity charging.

Influence of traps on the deuterium behaviour in the low activation martensitic steels F82H and Batman

A time dependent permeation method is used to measure the permeability, diffusivity and solubility of deuterium in the low activation martensitic steels F82H and Batman. The measurements cover the temperature range from 373 to 743 K which includes the onset of deuterium trapping effects on diffusivity and solubility. The results are interpreted using a trapping model. The number of trap sites and their average energies for deuterium in F82H and Batman steels are determined.

Solubility of hydrogen and deuterium in bcc uranium–titanium alloys

For the body-centered-cubic uranium–titanium alloy system, hydrogen and deuterium solubility measurements have been made on 12 alloy specimens ranging in composition from pure uranium to pure titanium and over a temperature range of 900–1473 K. The results are described in closed form by an analytical model within a standard error of 3%. The Einstein temperature (1680 K), and thus the isotope effect, was independent of alloy composition. The solubility and the enthalpy of solution were strongly dependent on alloy composition, more so at low titanium concentrations.

The diffusivity and solubility of deuterium in a high chromium martensitic steel

The permeability, diffusivity and solubility of deuterium in the martensitic stainless steel MANET II have been studied in the temperature range 194–465°C by applying a time dependent gas-phase permeation technique. It was found that the temperature dependence of diffusivity and solubility could not be described by a simple Arrhenius expression over the entire temperature range investigated. At lower temperatures (below about 330°C) the diffusivity was found to be greatly reduced by the effects of trapping. Oriani's model has been applied to obtain the trapping energy and number density of the traps as well as the relative amounts of deuterium dissolved at lattice and trap sites. It is suggested that the most likely sites for trapping are at interfaces between the martensitic laths and between second phase particles and the surrounding metal matrix.

Deuterium radial redistribution in Zr-liner cladding tubes

Hydrogen isotopes in fuel cladding of nuclear power reactor are of much interest in relation to the secondary hydriding of claddings, tritium content in spent fuels, and other issues. Using nuclear reaction analysis (NRA), we performed out-of-reactor analysis on the radial distribution of deuterium in Zr-liner zircaloy-2 claddings. Three specimens of the cladding were thermally charged with deuterium gas at 673 K in advance. One was quenched in water (sample 1) and the others were gradually cooled to 433 K (samples 2 and 3). The NRA showed that the radial distribution of deuterium was flat from the inside to the outside in the sample 1 tube. As diffusion of deuterium is much restricted after quenching, the distribution observed is considered to be the same as that before quenching. In samples 2 and 3, on the other hand, a sharp peak was formed in the zirconium liner near the Zr-zircaloy-2 interface. The peak concentration in the liner was several times as large as that in zircaloy-2. This indicated that the migration towards Zr-liner in the gradual cooling resulted in the redistribution of deuterium. The redistribution can be explained by a slight difference in the terminal solubility of deuterium in the two materials, Zr and zircaloy-2. The large effect of this slight difference on the redistribution of hydrogen isotopes is also discussed.

The terminal solid solubility of hydrogen and deuterium in Zr-2.5Nb alloys

The terminal solid solubility (TSS) of hydrogen or deuterium is an important parameter in Zr alloys that are used in the nuclear industry. If this solubility is exceeded, it can make the alloys susceptible to delayed hydride cracking. Accurate expressions for the TSS are necessary for modelling delayed hydride cracking as well as deuterium ingress into pressure tubes and blister formation in pressure tubes in contact with their calandria tubes. Measurements of the changes in the dynamic elastic modulus have been used to establish expressions for the TSS as a function of temperature and to study the hysteresis between hydride dissolution and precipitation. It is shown that the hysteresis is particularly sensitive to the thermal history of the sample (such as the prior maximum temperature, hold time at maximum temperature and cooling rate). As a result, the precipitation TSS (TSSP) has a range of values bounded by the solubility equations designated TSSP1 and TSSP2. These are obtained, respectively, by cooling from an upper- and a lower-bound maximum temperature. The TSSD equation obtained in this study is very close to previously determined expressions, but the TSSP equations differ significantly from earlier results.

Dissolution of hydrogen and deuterium in titanium, Ti94Al6 and Ti3Al

The solubility of hydrogen and deuterium in α-, α,β- and β-titanium, Ti94Al6 and in α2-Ti3Al has been volumetrically measured in the ranges of temperature 623–1323 K and hydrogen concentration (atomic ratio) 0.001–0.25. The equilibrium hydrogen pressure at a given temperature and hydrogen concentration has been found to increase greatly as the aluminium content increases. This is explicable on the assumption that aluminium atoms block some of the sites available to hydrogen atoms. In contrast, the heat of solution of hydrogen only slightly increases with the aluminium content and in α-titanium, α-Ti94Al6 and α2-Ti3Al, the ratio of the deuterium pressure to the hydrogen pressure at identical hydrogen and deuterium concentrations is almost independent of the aluminium content. A possible cause of the small dependence of the measured heat and ratio on the aluminium content is discussed and occupation of the tetrahedral site by hydrogen atoms is suggested for α-titanium, α-T94Al6 and α2-Ti3Al. The origin of the sloping plateaus observed in the pressure–composition isotherms for α, β-Ti94Al6 is also briefly discussed.

The effects of surface contamination on absorption and desorption of deuterium in beryllium and beryllium oxide

Deuterium thermal absorption and desorption experiments were conducted in high-purity Be, BeO and Be 2C samples. Ion-beam analysis was used to measure the surface contamination and near-surface deuterium concentration (up to depths of 500 nm). For bulk BeO the deuterium solubility is small, with S ≈ 10 18 exp(−0.8 eV/ kT) at/m 3(Pa) 1 2 , possibly indicative of the formation of hydroxide bonds; the diffusivity is ≥ 7 × 10 −5 exp(−2.1 eV/ kT) m 2/s. In deliberately corroded Be samples the deuterium surface concentration was about 0.02 at% where there was little or no carbon contamination, and up to 1.6 at% when the carbon and oxygen contents were similar. This implies the presence of large concentrations of trapped deuterium at or near the surface. The approximate solubility of bulk Be 2C samples was estimated as 3.4 × 10 27 exp(−0.58 eV/ kT) at /m 3(Pa) 1 2 . The solubility for deuterium in bulk Be was found to be 7 × 10 27 exp(−1.0 eV/ kT) at /m 3(Pa) 1 2 , and the bulk diffusivity is 8 × 10 −9 exp(−0.36 eV/ kT) m 2/s.

Crystal structure and superconductivity of high pressure hydrides and deuterides of HfRu and ZrRu compounds

The solubility of hydrogen and deuterium in HfRu and ZrRu was measured at 600 K and pressures up to 7 GPa. HfRuH(D) ≈3.6 and ZrRuH(D) 1.6–2.2 were synthesized. At ambient pressure these were shown to be superconductors with T c ∼ 4.5 and 3 K respectively. No difference between the T c values of the hydrides and deuterides of the same compound was detected. X-ray diffraction at 100 K has shown the metal sublattices of HfRuH x (D x ) and ZrRuH x (D x ) to be base-centred orthorhombic with very similar unit cell parameters. The crystal structures of HfRuH 3.6 and HfRuD 3.6 determined by neutron diffraction at 120 K were of the ZrNiH 3 type. The observed superconducting and structural properties of HfRuH x (D x ) and ZrRuH x (D x ) agree with the predictions of the rigid d-band model. The applicability of this model to other high pressure hydrides is discussed.