Vanadium Foil Research Articles

Excimer laser reactive deposition of vanadium nitride thin films

We report on the deposition of thin vanadium nitride films by ablating vanadium targets in low-pressure N 2 atmosphere, and on their characterization. The targets were vanadium foils (purity 99.8%). 3 in. Si(1 1 1) wafers were used as substrates. Film characteristics (composition and crystalline structure) were studied as a function of N 2 pressure (0.5–200 Pa), KrF laser fluence (4.5–19 J/cm 2), substrate temperature (20–750 °C) and target-to-substrate distance (30–70 mm). Vanadium nitride is already formed at low N 2 ambient pressures (1 Pa) and laser fluences (6 J/cm 2) on substrates at room temperature. At the N 2 pressures of 1–10 Pa, the prevalent phase is VN. At higher pressures (100 Pa) and at relatively high laser fluences (16–19 J/cm 2), the dominant phase is V 2N. The crystallinity of the films improves by increasing the substrate temperature. Well-crystallized films are obtained on substrates heated at 500 °C.

Spatially resolved diffraction using a Soller Collimator–Imaging plate assembly

A series of multiple foil collimators have been constructed to perform spatially resolved diffraction using a synchrotron radiation X-ray source and a two-dimensional X-ray detector. Slit gap sizes of 0.75, 0.25 and 0.125 mm were evaluated. A thin vanadium foil (BCC) on bulk titanium (HCP) was studied as a test system. This system simulates an α-Ti (HCP)→β-Ti (BCC) transformation in the heat affected zone of Ti fusion welds. Diffraction lines from both V(2 0 0) and Ti(1 0 2) were measured in the gap aligned with the V/Ti boundary. With improvements in the mounting of the slits, a spatial resolution of at least 0.12 mm will be possible.

Joint of silicon nitride and molybdenum with vanadium foil, and its high-temperature strength

Joints of silicon nitride and molybdenum with a vanadium interlayer were fabricated using a vacuum hot-pressing facility. The optimum joining conditions for producing a joint with the highest shear strength were found to be as follows: a temperature of 1328 K, a mechanical pressure of 20 MPa and a bonding time of 5.4 ks. The effect of test temperature on shear strength was also examined. The strength level was initially 118 MPa at room temperature and this level gradually decreased as the test temperature rose. At 973 K, the strength level was still 70 MPa. Observations of the interface by scanning electron microscopy (SEM) and electron probe X-ray microanalysis (EPMA) revealed that a layer of reaction product V3Si formed at the silicon-nitride-vanadium interface.

The electric field gradient at111Cd in vanadium oxides

The electric field gradient (efg) of111Cd in polycrystalline V2O5 was studied using perturbed angular correlation (PAC) spectroscopy, with the111In activity ion-implanted at 400 keV. Between the individual steps of an isochronal annealing program, a distinct efg (vQ1=88.1(3) MHz, ν1=0.62(2)) was recorded the contribution of which increased with annealing temperature up to 74% at 870 K. Corresponding X-ray analysis of inactive V2O5 samples, which underwent the same annealing treatment, proved that the sample always stayed as V2O5. Since V2O5 has only one equivalent cation site, it is concluded that this efg belongs to111Cd at this site. Oxidation of a vanadium foil atT=675 and 800 K at\(p_{{\text{O}}_{\text{2}} } \)=200 mbar also yielded this efg. From PAC measurements in VO2, two well-defined efg's were found above and below the metal-semiconductor transition at 340 K, which are tentatively attributed to the monoclinic and the tetragonal phase.

Joining of Silicon Carbide and Molybdenum with Vanadium Foil

A joining pair of silicon carbide and molybdenum was fabricated using vanadium foil as an insert material. The optimum fabricating conditions are bonding temperature of 1198 K, bonding pressure of 30 MPa and bonding time of 10.8 ks. The joint had high shear strength levels of 150 MPa at room temperature and of 52 MPa at 973 K. At the interface of silicon carbide and vanadium, a layer of vanadium silicide V3Si was formed.

Helium desorption from Fe and V by atomic diffusion and bubble migration.

Thermal helium desorption from homogeneously implanted iron and vanadium foils was investigated during linear heating and isothermal annealing, respectively. The isothermal experiments showed an initial period with a square-root dependence of the desorbed helium on time, characteristic of atomic helium diffusion, followed by a reduction of desorption due to clustering. The substitutional helium atoms migrate by a dissociative mechanism, with dissociation energies of 1.4\ifmmode\pm\else\textpm\fi{}0.3 eV for both metals. Up to temperatures of 600 K (Fe) and 700 K (V), retrapping was dominated by irradiation-induced vacancies. At higher temperatures diffusion times became unmeasurably small. Retention of helium in the specimens indicated that di-helium clusters are stable up to 673 K in Fe and up to 773 K in V. Desorption after clustering was analyzed by comparison with models of bubble coarsening. The vanadium results were best described by bubble migration via surface diffusion at all temperatures investigated (573--1173 K), while the iron data from 900 to 1184 K indicated bubble migration by volume diffusion as the prevalent coarsening mechanism.

Studies on metal-hydrogen systems (VD X, NbD X, LaNi 5H X) using secondary ion mass spectrometry

Secondary ion mass spectrometry (SIMS) measurements on deuterium-containing vanadium and niobium foils and hydrogen-containing LaNi 5 slices were carried out in order to investigate the secondary ion emission behaviour as a function of the hydrogen (deuterium) content and the primary ion current density. In the case of VD X and NbD X the secondary ion Me 2D + exhibits maximum intensity among all cluster ions containing deuterium and is therefore the most significant one for deuterium detection. This behaviour is obviously due to the high stability of Me 2D + deuteride phase of these metals. Regarding the system LaNi 5H X , the situation is more complicated because of the different sites that can be occupied by hydrogen in this host lattice. Besides a small LaH + signal the SIMS spectra shows NiH 2 − and Ni 2H − to be the most significant secondary ions. This observation points to a high association of hydrogen with nickel in ion-bombarded LaNi 5 and to an obvious pre-formation of a nickel dihydride in the LaNi 5 matrix. Furthermore, the emission of Ni X − signals is enhanced owing to the presence of hydrogen.

Studies on metal-hydrogen systems (VDx, NbDx, LaNi5Hx) using secondary ion mass, spectrometry

Secondary ion mass spectrometry (SIMS) measurements on deuterium-containing vanadium and niobium foils and hydrogen-containing LaNi5 slices were carried out in order to investigate the secondary ion emission behaviour as a function of the hydrogen (deuterium) content and the primary ion current density. In the case of VDX and NbDX the secondary ion Me2D+ exhibits maximum intensity among all cluster ions containing deuterium and is therefore the most significant one for deuterium detection. This behaviour is obviously due to the high stability of Me2D+ deuteride phase of these metals. Regarding the system LaNi5HX, the situation is more complicated because of the different sites that can be occupied by hydrogen in this host lattice. Besides a small LaH+ signal the SIMS spectra shows NiH2− and Ni2H− to be the most significant secondary ions. This observation points to a high association of hydrogen with nickel in ion-bombarded LaNi5 and to an obvious pre-formation of a nickel dihydride in the LaNi5 matrix. Furthermore, the emission of NiX− signals is enhanced owing to the presence of hydrogen.

Inelastic scattering of 120 keV electrons from carbon, aluminum, vanadium and silver foils

The inelastic scattering of 120 keV electrons from thin-film targets of carbon, aluminum, vanadium, and silver has been measured at 120° and 135°. The number of inelastically scattered electrons at each angle has been normalized to the elastically scattered electrons and the difference of the spectra at the two angles has been computed to correct for backscattering in the Si detector. The results are compared with a double scattering process of ionization followed by elastic scattering in the target. Significantly more backscattering is observed than can be explained by either the single scattering processes of ionization or bremsstrahlung or by the double process considered. Additional double processes need to be considered to resolve the discrepancy.

Inelastic scattering of 120 keV electrons from carbon, aluminum, vanadium and silver foils

Data are presented for absolute inelastic electron scattering cross sections from thin targets of carbon, aluminum, vanadium and silver at 45° and 60° for an incident electron energy of 120 keV. The data are compared with the theory of Cooper and Kolbenstvedt and with previous experimental data.

Magnetic properties of superconducting oxygen-doped vanadium foils

A systematic study is made of the superconducting magnetic properties of homogeneously oxygen doped vanadium foils. Starting from a high-purity sample, magnetization measurements are used to evaluate the superconducting parameters and their impurity dependence up to an oxygen concentration c = 1.5 at%. Nous presentons une etude systematique de I'influence de l'oxygene sur les proprietes magnetiques supraconductrices de feuille de vanadium. Les mesures d'aimantation sont utilisees pour evaluer les parametres supraconducteurs et leur dependance en fonction de la concentration c d'oxygene jusqu a c = 1,5 at%.

Strength and microstructure in vanadium irradiated with T(d, n) neutrons at 300 to 675 K

Tensile tests and microstructural examinations have been conducted on vanadium wires and foils following T(d, n) neutron irradiation at 300 K, 475 K and 675 K. Similar increases in yield strength were measured for samples irradiated at 300 K and 475 K but less strengthening occurred during irradiation at 675 K. Examination of the fracture surfaces showed that all samples failed by ductile rupture after attaining more than 95% reduction in area. A reasonable correlation between microstructures and strengthening was obtained using a simple dispersed barrier strengthening model. A high density of small defect clusters was responsible for strengthening after irradiation at 300 K. Following irradiation at 475 K, interstitial loops with a 〈100〉〈100〉 Burgers vectors were the predominant strengthening defect with a smaller contribution from ( a/2)〈111〉〈111〉 type loops. A heterogeneous distribution of dislocation loops and planar precipitates prevented definite correlations between strength and microstructure in samples irradiated at 675 K.

Influence of interstitial oxygen on the superconducting transition temperature of vanadium

The critical temperatureT c and residual resistivity ρ0 were measured in homogeneously oxidized thin vanadium foils. The per at % oxygen induced variations are respectively ΔT c =−1.2K and Δρ0=53 nΩ-m. TheT c data are used to calculate the electron-phonon coupling constant, which decreases 5% per at % of oxygen.

Magnetic properties of pure superconducting vanadium foils

We report on the magnetic properties of very pure superconducting vanadium foils (a resistivity ratio of 1500 in the starting single-crystal rod and of 300 in the cold-rolled foils). The magnetization curves are analyzed to obtain, as a function of temperature, the critical magnetic fields, the Ginzburg-Landau parameters, and the characteristic superconducting lengths. The experimental data are compared with the theoretical calculations of Eilenberger and with other measurements reported in the literature.

Some observations on the influence of oxygen on the resistive behavior of superconducting vanadium foils

Some observations on the influence of oxygen on the resistive behavior of superconducting vanadium foils

Particle release from vanadium metal surface by neutrons.

Sputtering yields from vanadium metal surface due to neutron irradiation were studied. A carefully prepared Pyrex glass tube, containing a vanadium foil as target and a polyethylene film pasted on a nickel plate as catcher, was sealed after evacuation, irradiated in a reactor, disassembled to take up the film, and the 52V activity on it was counted for estimating the thermal neutron sputtering yield due to the recoil by(n, γ) reaction. The reactivation of the film gave the fast neutron sputtering yield. These values were found to be 2.3×10−9 and 2.1×10−1 respectively.

Secondary ion mass spectrometry and Auger electron spectroscopy investigations of Vb metal foils prepared for hydrogen permeation measurements

Surface corrosion layers on vanadium, niobium and tantalum foils are shown to prevent almost entirely the hydrogen interphase transfer into the metal at normal temperatures. These layers have been removed by outgassing the foils in ultrahigh vacuum at high temperatures, and their rebuilding in the atmosphere has been prevented by coating the clean surfaces with a vapor-deposited thin film of Pd, permeable only to hydrogen. The techniques of secondary ion mass spectrometry and Auger electron spectroscopy have been used to obtain information on the composition and thickness of these surface layers and on the sucess of the above mentioned purification and protective technique.

Correlation studies on flux flow noise of polycrystalline niobium and vanadium foils

Using two movable contact pairs, cross-correlation functions of flux flow noise from polycrystalline niobium and vanadium foils have been measured. The results are compared with theoretical predictions derived from Clem's theory for the voltage associated with vortex motion across superconductors. Two cases are considered: (a) shot noise of randomly distributed flux entities moving with constant velocity and (b) noise due to locally generated random fluctuations of vortex velocity. There is strong evidence that the observed flux flow noise is produced by local flux flow fluctuations at pinning sites.

Preparation of manganese-53

The nuclide53Mn was produced by the following three nuclear reactions,52Cr(d, n)53Mn,51V(3He n)53Mn and50Cr(α, n), (α, p)53Mn. Enriched52Cr and50Cr metal targets were prepared on copper plate holder by electrodeposition. The commercially available natural vanadium foil was used for the51V(3He, n)53Mn reaction. Each target was bombarded in a cyclotron. Manganese was extracted and purified without using carrier from the bombarded targets by anion and cation exchanges and solvent extraction. The isotopic ratio53Mn/55Mn was measured by mass spectrometry and the amount of55Mn was determined by neutron activation analysis. The activity of53Mn obtained was 7 dpm by 750 millicoulombs in3He bombardment (E3He=20 MeV). The activity due to by-product54Mn was about several thousands times higher than that of53Mn in3He and deuteron bombardments, which were produced through51V(3He, γ)54Mn and53Cr(d, n)54Mn. In alpha bombardment (Eα=15 MeV), the activity of53Mn produced was 8 dpm by 95 millicoulombs. The activity ratio, dpm54Mn/dpm53Mn, was about 3, and this ratio was the best one among the results so far obtained.

Comparison of the V-H and V-D phase diagrams by means of NMR

The phase diagrams of vanadium-hydrogen (V-H) and vanadium-deuterium (V-D) have been investigated by measuring the nuclear magnetic resonance (NMR) spectra of vanadium and deuterium in strongly textured vanadium foils. In the cubic α- and α′-phases both the V and D lines are unsplit. From the orientation dependence of the quadrupole splitting of the two resonances in the tetragonal β-phase it is found that for both atoms the electric field gradient is axially symmetric with its largest component parallel to the c-axis. In contrast to V-H, the β-phase of V-D exists only in a small region near D/V ratios of about 0·4 at 300°K; for higher D concentrations the α′-phase remains stable down to about 200°K, below which the orthorhombic δ-phase is formed. In spite of the nearly cubic arrangement of the V atoms in the δ-phase, the intensity of the vanadium line is reduced corresponding to first-order quadrupole splitting. From the absence of any V satellites in the δ-phase, it follows that the orientation of the principal axes of the field gradient at the V sites deviate strongly from the cube edges of the V lattice. For deuterium the largest component is parallel to one cube edge, which must be the c-axis of the orthorhombic cell. Thus the field gradient at the D sites has the same symmetry in the β- and δ-phase, with quadrupole frequencies of 100 and 55 kHz, respectively. This difference can be attributed to the fact that in the two phases different sites are occupied: octahedral sites in the β-phase and tetrahedral sites in the δ-phase.