Superconductivity in zirconium-nickel glasses

The superconducting transition temperatures (T_c) and magnetic susceptibilities of amorphous Zr_100?xNi_x alloys have been measured. T_c decreases linearly with increasing x. The results are compared to those for amorphous ZrPd and ZrCu alloys and discussed in terms of changes in the electron to atom ratio on alloying.     

Preferred sputtering on binary alloy surfaces of the AlPdSi system

Auger spectroscopy has been used to investigate the behavior of preferred sputtering on surfaces of homogeneous AlPd, SiPd and AlSi alloy films. These combinations of alloys were chosen for studying the effects of mass and bonding differences on preferred sputtering. Experiments have been carried out using a 1 keV Ar ion beam over a range of alloy compositions. Our results can be summarized as follows: (a) The preferred sputtering of these binary alloys cannot be predicted according to the sputter yields of individual elements, e.g. both Al and Si have been observed to be removed preferentially relative to Pd although pure Pd has a higher sputter yield, (b) In the alloys studied, mass difference appears to dominate over bonding difference in controlling the preferred sputtering behavior since the extent of preferred sputtering of Al and Si relative to Pd is about the same. This observation is interpreted on the basis of the binary alloy sputtering theory formulated by Andersen and Sigmund. (c) Judging from the composition change of the sputtered surface, there is no evidence for formation of compounds with specific compositions as a result of preferred sputtering in the AlPd and SiPd alloys investigated.     

Magnetic properties of CrPd alloys

Magnetic susceptibility, resistivity, and neutron diffraction measurements have been obtained for a series of CrPd alloys containing up to 3 at.% Pd. The Néel temperature variation is irregular for a solute which is to the right of Cr in the periodic table.     

Thermal effects of transformations B2 ⇄ Al in CuPd alloy

We used high-temperature x-ray diffraction and thermography to investigate phase transitions B2 ⇄ Al in alloys Cu-Pd around 40 at. % Pd concentration. In phase transition region B2 → Al in alloy Cu-39.5 at. % Pd, we observed the maxima in the heat capacity curve. Based on structural data, we show that the first maximum is due to structural transition bcc-fcc (B2-Al) and the second is due to a decrease in the atomic long-range order in superlattice B2 and to a continuing bcc-fcc transition. Using structural information, we analyzed the thermograph of the quenched alloy Cu-36 at. % Pd. Structural Engineering Institute, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 35–38, February, 1993.     

Cu掺杂对TiNi合金马氏体相变路径影响的第一性原理研究

不同浓度的Cu元素掺杂会极大地影响TiNi二元合金的物理性质和相变行为.为了解释其中的物理机制,本文通过第一性原理计算,对TiNi和Ti_(50)Ni_(25)Cu_(25)的相变机制和相稳定性进行了计算和讨论.通过计算Cu掺杂前后立方相到正交相、再到单斜相过程中的相变路径和相变势垒,解释了Cu掺杂对二元合金TiNi相变过程的影响.计算结果表明:TiNi合金的正交相和单斜相之间存在一个大小为1.6meV的相变势垒;而对于Ti_(50)Ni_(25)Cu_(25),这两个相之间的相变势垒大小至少为10.3meV,如此大的一个相变势垒意味着Ti_(50)Ni_(25)Cu_(25)合金的正交相很难跨过势垒相变到单斜相.     

Superconducting transition of amorphous TiFe,ZrFe and HfFe produced by Fe implantation

Amorphous TiFe, ZrFe and HfFe alloys prepared by low temperature implantation of about 10 at% Fe were found to have superconducting transition temperatures, T_c, enhanced above the values of the pure crystalline elements. In addition, T_c = 2.6 K for TiFe is about 1 K higher than T_c of the equivalent amorphous TiCu alloy. A correlation between the recently observed dband behavior of similar binary transition metal alloys and the forming ability is extended to (Ti,Zr,Hf)-Fe alloys to explain their superconducting properties.     

Direct experimental confirmation of the critical behaviour of antiphase domain boundaries at the second order phase transition of Al-Fe binary alloys

The present work reports, for the first time, a direct experimental observation of the critical phenomenon associated with the B2-A2 order-disorder transition of Al-Fe binary alloys. Transmission electron microscopy and energy dispersion spectroscopy are employed to span the morphological changes through the transition line from the ordered B2 phase to the disordered A2 phase. Dark field images of the microstructure around the transition line for samples aged at 973 and 1073 K for various times show an interface roughening for the {100} antiphase domain boundaries in body-centered cubic binary alloys having the B2 structure. This observation confirms theory about the instability of the second-order transition in such alloys. This behaviour occurs for compositions with Al-content slightly higher (by ∼4 at.% Al) than that of the critical point of the equilibrium order-disorder transition. In addition, roughness-induced wetting transition is also observed for alloys having compositions ranging from 1.3 to 1.5 at.% Al above the transition line. The interface roughening transition is thought to be unstable second-order while the wetting transition is suggested to be a stable first-order one.     

The relationship between empty d-state density and XPS satellite intensities in nickel alloys

It is shown with the example of ThNi and ThPd alloys that the d-bands of Ni and Pd tend to fill when Ni and Pd are alloyed with electropositive metals. The satellites on the higher binding energy side of both core and valence band XPS spectra decrease in intensity on alloying and the core level peaks become less asymmetric. These satellites arise in the elements because the d-bands are not full and their decrease in the alloys is related to the d-band filling. The results thus indicate how alloying modifies the Ni and Pd d-bands and how information on valence band properties can be derived from the core level peak shapes.     

Shubnikov-de Haas effect and semimetal-semiconductor transition in bismuth-antimony alloys in high magnetic fields

Shubnikov-de Haas effect is observed in Bi and BiSb alloys (containing 0.1?4.4 at.% Sb) in pulsed high magnetic fields up to 420 kG. It is found that the amplitude of the quantum oscillation remarkably increases by mixing a small amount of Sb in Bi, and that the magnitude of the Hall electric field in BiSb alloy (0.1 at.% Sb) is much larger than that in pure Bi. These observations demonstrate the difference in the scattering mechanism of carriers between Bi and BiSb alloys. The magnetic field induced semimetal to semiconductor transition is observed in BiSb alloy with 4.4 at.% Sb. From the analysis of the Shubnikov-de Haas oscillation in BiSb, the field at which the semimetal to semiconductor transition will occur in Bi is estimated as about 1 MG for the field direction parallel to the binary axis.     

An acoustic anomaly at the phase transition in GeTeSnTe alloy single crystals

The ultrasonic wave velocities and attenuation have been measured in single crystals of 20 mole.% GeTeSnTe alloys between 90 and 373°K. The ultrasound velocities and thus the elastic constants show a step-like behaviour, which is accompanied by a peak in the attenuation, at the cubic to rhombohedral transformation temperature (240°K). In the vicinity of the transition a strong interaction occurs between the acoustic phonon modes and the soft TO mode.     

Electrochemical and surface behavior of hydyroxyapatite/Ti film on nanotubular Ti-35Nb-xZr alloys

In this paper, we investigated the electrochemical and surface behavior of hydroxyapatite (HA)/Ti films on the nanotubular Ti-35Nb-xZr alloy. The Ti-35Nb-xZr ternary alloys with 3-10 wt.% Zr content were made by an arc melting method. The nanotubular oxide layers were developed on the Ti-35Nb-xZr alloys by an anodic oxidation method in 1 M H₃PO₄ electrolyte containing 0.8 wt% NaF at room temperature. The HA/Ti composite films on the nanotubular oxide surfaces were deposited by a magnetron sputtering method. Their surface characteristics were analyzed by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) and an X-ray diffractometer (XRD). The corrosion behavior of the specimens was examined through potentiodynamic and AC impedance tests in 0.9% NaCl solution. From the results, the Ti-35Nb-xZr alloys showed a solely β phase microstructure that resulted from the addition of Zr. The nanotubular structure formed with a diameter of about 200 nm, and the HA/Ti thin film was deposited on the nanotubular structure. The HA/Ti thin film-coated nanotubular Ti-35Nb-xZr alloys showed good corrosion resistance in 0.9% NaCl solution.     

Surface composition of PdAu and PdAg catalysts by auger electron spectroscopy

Auger electron spectroscopy (AES) has been employed to examine the metal surface composition of PdAu and PdAg alloys as microspheres and as alumina-supported crystallites. For the PdAu system the observed PdAu ratios at the surface correspond closely to those of the bulk both for the microspheres and crystallites. However in the case of supported PdAg, the surface exhibits silver-enrichment relative to the bulk. By means of the regular solution monolayer model the results are interpreted theoretically and the binding energies between the dissimilar metal atoms are computed.     

Radiographic analysis of the structures of films obtained by vacuum sputtering of some copper-based low alloys

Diffractometric phase analysis of the structures of alloys on copper base, containing small concentrations of Mn, Pd, Al, Ti, Zr, Ce, and Ni, and of films on their base, was carried out. The differences in the structure of initial bulk samples of the alloys, and of condensates obtained by sputtering in vacuum, are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 101–105, November, 1973.     

Role of phonon dynamics in the thermopower of niobium hydrides

The thermopower of NbH_x alloys for x varying from 0.607 to 0.883 has been examined at temperatures ranging from 100 to 430 K. It was found that the transition from orthorhombic β to cubic α' phase is accompanied by a strong change of thermopower. It is concluded that differences in phonon spectra of these two phases are responsible for the observed differences in the transport properties. The sensitivity of the thermopower to any other phase transitions in this system has been observed as well.     

Superconductivity in the metal rich Li-Pd-B ternary boride

Superconductivity at about 8 K was observed in the metal-rich Li-Pd-B ternary system. Structural, microstructural, electrical, and magnetic investigations for various compositions proved that the Li2Pd3B compound, which has an antiperovskite cubic structure composed of distorted Pd6B octahedrons, is responsible for the superconductivity. This is the first observation of superconductivity in metal-rich ternary borides containing alkaline metal and Pd as a late transition metal. The compound prepared by arc melting has a high density and is relatively stable in the air. The upper critical fields H(c2)(0) estimated by linear extrapolation and the Werthamer-Helfand-Hohenberg theory are 6.2 and 4.8 T, respectively.     

Untersuchungen zur Supraleitung des Legierungssystems Zr-Rh

The transition temperatures of Zr-Rh alloys with small amounts of Rh are essentially higher than the transition temperature of pure Zr. Rhodium is not dissolved in the Zr lattice. In the unannealed specimens Rh stabilizes the body centered cubic phase which has aT _c of 6.4°K. After annealing an intermetallic compound is formed with aT _c of about 12°K. This compound is also formed in the unannealed specimens at higher Rh content.     

Crystallographic texture and microstructure evolution during hot compression of Ti–6Al–4V–0.1B alloy in the (α + β)-regime

Microstructure and texture are known to undergo drastic modifications due to trace hypoeutectic boron addition (~0.1 wt.%) for various titanium alloys e.g. Ti–6Al–4V. The deformation behaviour of such an alloy Ti–6Al–4V–0.1B is investigated in the (α?+?β) phase field and compared against that of the base alloy Ti–6Al–4V studied under selfsame conditions. The deformation microstructures for the two alloys display bending and kinking of α lamellae in near α and softening via globularization of α lamella in near β phase regimes, respectively. The transition temperature at which pure slip based deformation changes to softening is lower for the boron added alloy. The presence of TiB particles is largely held attributable for the early softening of Ti–6Al–4V–0.1B alloy. The compression texture of both the alloys carry signature of pure α phase defamation at lower temperature and α→β→α phase transformation near the β transus temperature. Texture is influenced by a complex interplay of the deformation and transformation processes in the intermediate temperature range. The contribution from phase transformation is prominent for Ti–6Al–4V–0.1B alloy at comparatively lower temperature.     

The atomic parameter model for the fifth and sixth transition metal quasicrystal alloys(Mc=0.5)

The forming ability of quasicrystal phase has a relationship with the atomic bond factors based on differences in atom size and electron factors.Usually,those factors or their combination are used to describe the forming ability,stability of alloys,etc.In this paper,the quasicrystal alloy forming abilities for the fifth and sixth transition metals(Y,Zr,Nb,Mo,Ru,Rh,Pd and La,Hf,Ta,W,Re,Os,Ir,Pt) based alloys have been studied by the size factor and the atomic parametric function.It has been found that an ell...     

The surface composition of the gold-palladium binary alloy system

The surface composition of the AuPd alloy system has been determined by Auger electron spectroscopy. Measurements were performed on polished polycrystalline alloy foils. After cleaning, the intensities of the 71 eV and 2024 eV gold Auger transitions, and the intensity of the 330 eV palladium transition were measured, and then converted to atom concentrations in the surface layer. The surfaces of the annealed samples were found to be significantly enriched in gold with respect to the bulk. This result disagrees with the regular solution theory prediction. After extensive sputtering of the AuPd alloys with 1.5 keV Ar⁺ ions, a slight surface enrichment with palladium was found, as predicted by the simple theoretical model for sputtering.     

91Zr NMR characterisation of phases in transformation toughened zirconia.

A detailed 91Zr NMR investigation is presented of the five component (cubic, monoclinic, tetragonal, orthorhombic and delta) phase mixture in the transformation toughened engineering ceramic, magnesia-partially-stabilised zirconia (MgPSZ). The phases are distinguished on the basis of the quadrupole interaction displayed in the powder pattern of the 91Zr(1/2, -1/2) transition. This paper reports: (i) the first characterisation of the magnesia-fully-stabilised cubic phase at the eutectic composition (13.5 mol% MgO); (ii) the observation of a poorly ordered tetragonal phase on fast cooling ZrO2 (9.3 mol% MgO) from the cubic phase field at 1720 degrees C, and the subsequent growth and ordering of the tetragonal phase precipitates due to further annealing; (iii) the observation of the (partial) transformation of the cubic phase to the ordered delta-phase (Mg2Zr5O12) on annealing MgPSZ at 1100 degrees C for 8 h; and (iv) the observation of the transformation of the tetragonal phase into the orthorhombic phase after cooling in liquid nitrogen, and the reverse transformation after heating to 600 degrees C.