GdCuMg with ZrNiAl-type structure. An 82.2 K ferromagnet

Energy Technology Data Exchange (ETDEWEB)

Stein, Sebastian; Heletta, Lukas; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

2017-08-01

GdCuMg has been synthesized by induction-melting of the elements in a sealed niobium ampoule followed by annealing in a muffle furnace. The sample was studied by powder and single crystal X-ray diffraction: ZrNiAl type, P anti 62m (a=749.2(4), c=403.3(1) pm), wR2=0.0242, 315 F{sup 2} values and 15 variables. Temperature dependent magnetic susceptibility measurements have revealed an experimental magnetic moment of 8.54(1) μ{sub B} per Gd atom. GdCuMg orders ferromagnetically below T{sub C}=82.2(5) K and based on the magnetization isotherms it can be classified as a soft ferromagnet.

Structural stability of ternary C22–Zr6X2Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and C22–Zr6Sn2T′ (T′=Fe, Co, Ni, Cu) compounds

International Nuclear Information System (INIS)

Colinet, Catherine; Crivello, Jean-Claude; Tedenac, Jean-Claude

2013-01-01

The crystal and electronic structures, and the thermodynamic properties of Zr 6 X 2 Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr 6 Sn 2 T′ (T′=Fe, Co, Ni, Cu) ternary compounds in the Fe 2 P-type structure have been investigated by means of first principle calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the ternary Zr 6 X 2 Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr 6 Sn 2 T′ (T′=Fe, Co, Ni, Cu) compounds. - Graphical abstract: Valence charge electronic localization function (ELF) calculated for Zr 6 Sb 2 Co compound. Display Omitted - Highlights: • Structural stability of Zr 6 X 2 T′ compounds (X: p element, T′: late transition metal) in the Fe 2 P-type structure. • First principles calculation of lattice parameters and enthalpies of formation. • Electronic densities of state in the series Zr 6 Sn 2 T′ (T′=Fe, Co, Ni, Cu). • Electronic densities of state in the series Zr 6 X 2 Co (X=Al, Ga, Sn, As, Sb, Bi, Te)

Laser-joined Al{sub 2}O{sub 3} and ZrO{sub 2} ceramics for high-temperature applications

Energy Technology Data Exchange (ETDEWEB)

Boerner, Floriana-Dana, E-mail: floriana.boerner@tu-dresden.d [Dresden University of Technology (TU Dresden), Institute of Power Engineering, Chair of Hydrogen Technology and Nuclear Power Engineering, George-Baehr-Str. 3, D-01062 Dresden (Germany); Lippmann, Wolfgang, E-mail: wolfgang.lippmann@tu-dresden.d [Dresden University of Technology (TU Dresden), Institute of Power Engineering, Chair of Hydrogen Technology and Nuclear Power Engineering, George-Baehr-Str. 3, D-01062 Dresden (Germany); Hurtado, Antonio, E-mail: antonio.hurtado@tu-dresden.d [Dresden University of Technology (TU Dresden), Institute of Power Engineering, Chair of Hydrogen Technology and Nuclear Power Engineering, George-Baehr-Str. 3, D-01062 Dresden (Germany)

2010-10-01

A laser process is presented that has been specially developed for joining oxide ceramics such as zirconium oxide (ZrO{sub 2}) and aluminium oxide (Al{sub 2}O{sub 3}). It details, by way of example, the design of the laser process applied for to producing both Al{sub 2}O{sub 3}-Al{sub 2}O{sub 3} and ZrO{sub 2}-ZrO{sub 2} joints using siliceous glasses as fillers. The heat source used was a continuous wave diode laser with a wavelength range of 808-1010 nm. Glasses of the SiO{sub 2}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}-MeO system were developed as high-temperature resistant brazing fillers whose expansion coefficients, in particular, were optimally adapted to those of the ceramics to be joined. Specially designed measuring devices help to determine both the temperature-dependent emission coefficients and the synchronously determined proportions of reflection and transmission. The glass-ceramic joints produced are free from gas inclusions and macroscopic defects and exhibit a homogenous structure. The average strength values achieved were 158 MPa for the Al{sub 2}O{sub 3} system and 190 MPa for the ZrO{sub 2} system, respectively.

Structural and catalytic characterization of mechanical mixtures of Pt/WOx-ZrO2 and Al2O3

International Nuclear Information System (INIS)

Contreras, J.L.; Fuentes, G.A.; Navarrete, J.; Vazquez, A.; Zeifert, B.; Salmones, J.; Nuno, L.

2010-01-01

The effect of the Bronsted/Lewis acid ratio on isomerization of n-heptane using Al 2 O 3 as a source of Lewis acidity and WOx/ZrO 2 as a source of Bronsted and Lewis acidity was studied and controlled using mechanical mixtures of these solids. These mixtures were characterized by surface area, infrared spectroscopy of pyridine, X-ray diffraction and Raman spectroscopy. It was found that the presence of W=O stretching mode which was consistent with the presence of oxotungstate species which were the precursors of the acid sites. It was found out that as the oxotungstate structures increased, the selectivity to n-heptane isomers increased while the hydrocracking and dehydrocyclization selectivity decreased. The presence of Bronsted acidity of the WOx/ZrO 2 domains, the increase of Knudsen diffusivity and the loss of Pt metallic area by strong interaction of the Pt with the WOx/ZrO 2 explain this catalytic behavior.

Properties of slip-cast transformation-toughened β''-Al2O3/ZrO2 composites

International Nuclear Information System (INIS)

Green, D.J.; Metcalf, M.G.

1984-01-01

The aim of this study was to fabricate β''-Al 2 O 3 /ZrO 2 composites by an alternative procedure than the dry-pressing route chosen by Lange et al. or Viswanathan et al. and to determine the amount of ZrO 2 that can be used to maximize the fracture toughness without significantly affecting the ionic resistivity. The fabrication technique chosen was that of slip casting, as this approach should allow the ZrO 2 phase to be well dispersed without the detrimental presence of agglomerates, which can act as failure origins in ceramics. Slip casting is a well-established ceramic fabrication technique and is versatile in being able to produce rather complex shapes. It has been used previously to fabricate β-Al 2 O 3 . In the present study, it was decided to perform the slip casting using organic media as water reacts with β''-Al 2 O 3 and leaches out the sodium by ion exchange and can significantly influence the ionic conductivity. It was important, therefore, to identify suitable organic media that could be used to control the dispersion of the β''-Al 2 O 3 and ZrO 2 powders and identify the important processing parameters that would give rise to a fine-grained microstructure in which the ZrO 2 was well dispersed and retained in its tetragonal form

Compressive strain-dependent bending strength property of Al2O3-ZrO2 (1.5 mol% Y2O3) composites performance by HIP

International Nuclear Information System (INIS)

Reyes-Rojas, A.; Esparza-Ponce, H.; De la Torre, S.D.; Torres-Moye, E.

2009-01-01

Nanometric powders and sintered ceramics of Al 2 O 3 -ZrO 2 (1.5 mol% Y 2 O 3 ) prepared by hot isostatic pressing HIP have been studied. A detailed crystallographic study has been performed through X-ray diffraction, Williamson-Hall method, Rietveld method and high-resolution electron microscopy HREM analysis. The crystallographic structure data, such as domain size, lattice parameters, wt% phase, and micro-strain direction have been obtained using Rietveld refinement and Williamson-Hall methods. The results revealed that the compressive strain (ε) increased from 0.56 to 1.18 (10 -3 ) as the t-ZrO 2 content increased too. The HREM interface study conducted along the [0 0 0 1]Al 2 O 3 ||[0 0 1]ZrO 2 zone axis revealed a micro-strain lattice distortion accumulated at the grain boundary due to the ZrO 2 martensitic phase transformation on cooling, t-ZrO 2 grains coalescence and to the grain growth of α-Al 2 O 3 which cause elongated tetragonal crystals. Micro-strain lattice distortion is adjusted by the shear displacements of the planes (1 1 0) and (11-bar0) along [1-bar10] and [1-bar1-bar0] crystallographic directions, respectively; these planes are arrested by the (101-bar0) alumina plane. In this case, semi-coherent interfaces were observed along the grain boundary. It is verified that the bending strength increased in connection with the strain accumulation and amount of tetragonal structure

Hydrogenation of FeCoZr-Al2O3 nanocomposites studied by Moessbauer spectroscopy and magnetometry

International Nuclear Information System (INIS)

Saad, A.; Kasiuk, J.; Fedotova, J.; Szilagyi, E.; Przewoznik, J.; Kapusta, Cz.; Marszalek, M.

2009-01-01

Hydrogenation effects on crystalline and magnetic structure of nanocomposites (FeCoZr) x (Al 2 O 3 ) 100-x , 38 ≤ x ≤ 63 at.% are studied by 57 Fe Moessbauer spectroscopy and magnetometry. Variations of local structure, blocking temperature and mean FeCoZr nanoparticles' volume are discussed with respect to (i) composition and (ii) two competing processes-H 2 incorporation and annealing-occurred during treatment in H 2 plasma.

Design of high-temperature high-strength Al-Ti-V-Zr alloys

International Nuclear Information System (INIS)

Lee, H.M.

1990-01-01

This paper reports that it seems plausible to develop high-strength Al-base alloys useful up to 698K in view of the behavior of nickel base superalloys which resist degradation of mechanical properties to 75 pct of their absolute melting temperature. For high temperature Al alloys, the dispersed hardening phase must not undergo phase transformation to an undesirable phase during long time exposure at the temperature of interest. An additional factor to be considered is the stability of the hardening phase with respect to Ostwald ripening. This coarsening resistance is necessary so that the required strength level can be maintained after the long-time service at high temperatures. The equilibrium crystal structures of Al 3 Ti, Al 3 V and Al 3 Zr are tetragonal D0 22 , D0 22 and D0 23 , respectively. At the temperatures of interest, around 698K, vanadium and titanium are mutually substitutable in the form of Al 3 (Ti, V). Much of titanium and vanadium can be substituted for zirconium in the D0 23 - type Al 3 Zr compound, creating Al 3 (Ti, Zr) and Al 3 (V, Zr), respectively. In particular, it has been reported that fcc L1 2 -structured Al 3 M dispersoids form in the rapidly solidified Al-V-Zr and Al-Ti-Zr systems and both L1 2 and D0 23 -structured Al 3 M phases showed slow coarsening kinetics

X-ray study of rapidly cooled ribbons of Al-Cr-Zr and Al-Ni-Y-Cr-Zr alloys

International Nuclear Information System (INIS)

Betsofen, S.Ya.; Osintsev, O.E.; Lutsenko, A.N.; Konkevich, V.Yu.

2002-01-01

One investigated into phase composition, lattice spacing and structure of rapidly cooled 25-200 μm gauge strips made of Al-4,1Cr-3,2Zr and Al-1,5Cr-1,5Zr-4Ni-3Y alloys, wt. %, produced by melt spinning to a water-cooled copper disk. In Al-4,1Cr-3,2Zr alloy one detected intermetallic phases: Al 3 Zr and two Al 86 Cr 14 composition icosahedral phases apart from aluminium solid solution with 4.040-4.043 A lattice spacing. In Al-1,5Cr-1,5Zr-4Ni-3Y alloy one identified two Al 86 Cr 14 icosahedral phases and two AlNiY and Al 3 Y yttrium-containing ones, lattice spacing of aluminium solid solution was equal to 4.052-4.053 A [ru

Novel Ni-Ce-Zr/Al2O3 Cellular Structure for the Oxidative Dehydrogenation of Ethane

Directory of Open Access Journals (Sweden)

Juan Pablo Bortolozzi

2017-11-01

Full Text Available A novel γ-alumina-supported Ni-Ce-Zr catalyst with cellular structure was developed for oxidative dehydrogenation of ethane (ODHE. First, powdered samples were synthesized to study the effect of both the total metal content and the Ce/Zr ratio on the physicochemical properties and performance of these catalysts. All synthesized powdered samples were highly active and selective for ODHE with a maximum ethylene productivity of 6.94 µmolethylene gact cat−1 s−1. According to the results, cerium addition increased the most reducible nickel species population, which would benefit ethane conversion, whereas zirconium incorporation would enhance ethylene selectivity through the generation of higher amounts of the least reducible nickel species. Therefore, the modification of active site properties by addition of both promoters synergistically increases the productivity of the Ni-based catalysts. The most efficient formulation, in terms of ethylene productivity per active phase amount, contained 15 wt% of the mixed oxide with Ni0.85Ce0.075Zr0.075 composition. This formulation was selected to synthesize a Ni-Ce-Zr/Al2O3 structured body by deposition of the active phase onto a homemade γ-alumina monolith. The structured support was manufactured by extrusion of boehmite-containing dough. The main properties of the Ni0.85Ce0.075Zr0.075 powder were successfully preserved after the shaping procedure. In addition, the catalytic performance of the monolithic sample was comparable in terms of ethylene productivity to that of the powdered counterpart.

Precipitation structures and mechanical properties of Al-Li-Zr alloy containing V

International Nuclear Information System (INIS)

Ying, J.K.; Ohashi, T.

1999-01-01

It is known that Al-Li alloys possess high elastic modulus and low density, and the metastable δ' (Al 3 Li) precipitate in these alloys affords considerable strengthening effect. However, with the strengthening resulting from the precipitation of δ' which is coherent with the matrix, these alloys suffer from low ductility and fracture toughness. It seems that the loss of ductility is the slip localization which occurs as a result of slip planes during deformation in connection with the specific hardening mechanism. As a result it indicates typical intergranular fracture. On the one hand, zirconium is used in many aluminum alloys to inhibit recrystallization during alloy processing. When zirconium is present in the alloy grain refinement occurs, which consequently, is considered as a factor that reduces the slip distance, and lowers the stress concentration across grain boundaries and at grain boundary triple points. Nevertheless, if only zirconium is added in Al-Li alloy it still shows intergranular fracture. By Zedaris et al., equilibrium phase Al 3 (Zr,V) in Al-Zr alloy containing V reduces the lattice mismatch along the c-axis with Al and, the L1 2 -structure metastable precipitates Al 3 (Zr,V) in Al-Zr-V alloys are stable at elevated temperature. Therefore, it is interesting to elucidate the effect of V in Al-Li-Zr alloy at the precipitation structures and mechanical properties of these alloys

Field ion microscopy and 3-D atom probe analysis of Al3Zr particles in 7050 Al alloy

International Nuclear Information System (INIS)

Sha, G.; Cerezo, A.

2004-01-01

Full text: For high strength 7xxx series Al alloys, Zr is an important trace alloy element which is often added to optimise properties, having effects such as refining grain size, inhibiting recrystallization, and improving stress corrosion cracking resistance and quench sensitivity. In addition, it has been reported recently that Zr addition also has a significant influence on early stage ageing behaviour of a 7xxx series Al alloy. Zr equilibrium solubility in solid Al is extremely low. After solution or ageing treatment, most Zr is present as small spherical Ai 3 Zr dispersoids approximately 20 nm in diameter, distributed at grain boundaries as well as within the Al matrix. The crystallographic nature of intermetallic phase Al 3 Zr has been well studied in the literatures. So far, no direct measurement of the chemistry of the Al 3 Zr particles in 7xxx series Al alloys has been published. It is unclear if there is significant Zn, Mg or Cu included in the particles. In this research, 3DAP has been employed for the first time to investigate ionisation behaviour of Al 3 Zr particles and determine the chemistry of the particles in 7050 Al alloy. Using field ion microscopy, the local evaporation radius of the Al 3 Zr particle has been measured to be equivalent to 36 nm for a 10 kV tip, less than the equivalent tip radius for the Al matrix of ∼68 nm. Using the matrix Al evaporation field (19 V/nm) as a reference, this allows the evaporation field of Al 3 Zr to be calculated as 35 V/nm, the same as the field calculated for evaporation of Al as Al 2+ (35 V/nm), and that of Zr as Zr 3+ (35 V/nm). This result is consistent with Al 2+ and Zr 3+ being the main species observed in the mass spectrum during analysis of Al 3 Zr particles. Using 3DAP, the chemical compositions of Al 3 Zr particles are determined to be 64.8∼67.7 at% Al, 23.6∼24.8 at% Zr, 6.9∼9.1 at% Zn, 0.4∼0.7 at% Cu, 0.5∼1.2 at% Mg, with a (Al+Zn)/Zr ratio close to 3. Choice of specimen temperature of

Epitaxial thin-film growth of Ruddlesden-Popper-type Ba3Zr2O7 from a BaZrO3 target by pulsed laser deposition

International Nuclear Information System (INIS)

Butt, Shariqa Hassan; Rafique, M.S.; Siraj, K.; Latif, A.; Afzal, Amina; Awan, M.S.; Bashir, Shazia; Iqbal, Nida

2016-01-01

Ruddlesden-Popper Ba 3 Zr 2 O 7 thin films have been synthesized via pulsed laser deposition (PLD) technique. The optimization of deposition parameters in PLD enables the formation of thin film of metastable Ba 3 Zr 2 O 7 phase from BaZrO 3 target. In order to see the post-annealing effects on the structural and optical properties, the deposited Ba 3 Zr 2 O 7 thin films were annealed at 500, 600 and 800 C. X-ray diffraction (XRD) reveals the formation of Ba 3 Zr 2 O 7 phase with tetragonal structure. The changes in the surface of the deposited films were analysed by FE-SEM and AFM. The thin film post-annealed at 500 C exhibited the best structural, optical and surface properties. Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. The XPS results show that Ba, Zr and O exist mainly in the form of Ba 3 Zr 2 O 7 Ruddlesden-Popper-type perovskite structure. (orig.)

Structural stability of ternary C22–Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and C22–Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) compounds

Energy Technology Data Exchange (ETDEWEB)

Colinet, Catherine, E-mail: ccolinet@simap.grenoble-inp.fr [Science et Ingénierie des Matériaux et Procédés, Grenoble INP, UJF, CNRS, 38402 Saint Martin d’Hères, Cedex (France); Crivello, Jean-Claude [ICMPE-CMTR, CNRS UMR-7182, 2-8 rue Henri Dunant, 94320 Thiais (France); Tedenac, Jean-Claude [Institut de Chimie Moléculaire et des Matériaux I.C.G., UMR-CNRS 5253, Université Montpellier II, Place E. Bataillon, 34095 Montpellier Cedex 5 (France)

2013-09-15

The crystal and electronic structures, and the thermodynamic properties of Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) ternary compounds in the Fe{sub 2}P-type structure have been investigated by means of first principle calculations. The calculated structural parameters are in good agreement with the experimental data. The total electronic densities of states as well as the Bader charges of the atoms have been computed. Both electronic and size effects allow to explain the stability of the ternary Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te) and Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu) compounds. - Graphical abstract: Valence charge electronic localization function (ELF) calculated for Zr{sub 6}Sb{sub 2}Co compound. Display Omitted - Highlights: • Structural stability of Zr{sub 6}X{sub 2}T′ compounds (X: p element, T′: late transition metal) in the Fe{sub 2}P-type structure. • First principles calculation of lattice parameters and enthalpies of formation. • Electronic densities of state in the series Zr{sub 6}Sn{sub 2}T′ (T′=Fe, Co, Ni, Cu). • Electronic densities of state in the series Zr{sub 6}X{sub 2}Co (X=Al, Ga, Sn, As, Sb, Bi, Te)

Preparation of Cu/La{sub 2}O{sub 3}-ZrO{sub 2}-Al{sub 2}O{sub 3} catalyst and its catalytic properties for selective reduction of NO

Energy Technology Data Exchange (ETDEWEB)

Xi-kun Guo; Ping-ping Xie; Shu-dong Lin [Shantou University, Shantou (China). Department of Chemistry

2008-12-15

An La{sub 2}O{sub 3}-ZrO{sub 2}-Al{sub 2}O{sub 3} composite support was prepared by co-precipitation with the mixed aqueous solution of La(NO{sub 3}{sub 3}, Al(NO{sub 3){sub 3}, and ZrOCl{sub 2} dropping into the precipitant of (NH{sub 4})2CO{sub 3} aqueous solution. The Cu/La{sub 2}O{sub 3}-ZrO{sub 2}-Al{sub 2}O{sub 3} catalyst was prepared by the impregnation of La{sub 2}O{sub 3}-ZrO{sub 2}-Al{sub 2}O{sub 3} with active component Cu{sup 2+} aqueous solution. The effects of the catalyst on the selective catalytic reduction of NO with propylene in excess oxygen were investigated. The relationships between the preparation method, structure and properties of the Cu/La{sub 2}O{sub 3}-ZrO{sub 2}-Al{sub 2}O{sub 3} catalyst were also explored by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), surface area measurements (BET), pyridine absorption infrared spectrum (Py-IR), thermal gravimetry (TG), and temperature-programmed reduction (TPR). The results indicate that the support {gamma}-Al{sub 2}O{sub 3} prepared by Al(NO{sub 3})3 dropping into (NH{sub 4}{sub 2} CO{sub 3} can remarkably enlarge the surface area; the addition of La{sub 2}O{sub 3} contributes mainly to the enhancement of the thermal stability; and the introduction of ZrO{sub 2} can increase the amount of Lewis and Broenstead acid. Consequently, the catalyst Cu/La{sub 2}O{sub 3}-ZrO{sub 2}-Al{sub 2}O{sub 3} has excellent activity for the selective reduction of NO with propylene in excess oxygen. NO conversion is up to 88.9% at 300{sup o}C and 81.9% even at the presence of 10% volume fraction of water vapor. 15 refs., 8 figs., 1 tab.

Phase equilibria of Al3(Ti,V,Zr) intermetallic system

International Nuclear Information System (INIS)

Park, S.I.; Han, S.Z.; Choi, S.K.; Lee, H.M.

1996-01-01

Trialuminides such as DO 22 -structured Al 3 Ti are promising candidates as potential materials for elevated temperature applications because of their attractive high temperature strength and excellent oxidation resistance along with their low density. However, in the tetragonal structure, slip systems are restricted due to low symmetry and the primary deformation mode is twinning. And, therefore, monolithic trialuminide compounds have been very impractical to be used as structural materials. When transition elements such as Ti, V and Zr which constitute trialuminides are alloyed in aluminum, they have low solubilities and low diffusion coefficients in the Al matrix. If precipitated as trialuminide intermetallics, they maintain a small lattice mismatch with the Al matrix, which reduces the interfacial energy between matrix and precipitates. As a result, these precipitates would have a large coarsening resistance in the matrix. As most of the previous works have been concentrated on the microstructural stability and mechanical properties, thermochemical properties will be treated in this work. In this study, phase equilibria and diagrams of Al 3 (Ti,V,Zr) systems will be experimentally determined and then thermodynamically analyzed with a hope to extend to the Al-Al 3 (Ti,V,Zr) composite system. This approach will then be used as a guide for alloy design of Al-Al 3 (Ti,V,Zr) composite system

Low silicon U(Al,Si)3 stabilization by Zr addition

International Nuclear Information System (INIS)

Pizarro, L.M.; Alonso, P.R.; Rubiolo, G.H.

2009-01-01

Previous knowledge states that (U,Zr)Al 3 and U(Al,Si) 3 phases with Zr and Si content higher than 6 at.% (7.7 wt%) and 4 at.% (1.4 wt%), respectively, does not partially transform to UAl 4 at 600 o C. In this work, four alloys within the quaternary system U-Al-Si-Zr were made with a fixed nominal 0.18 at.% (0.1 wt%) Si content in order to assess the synergetic effect of both Zr and Si alloying elements to the thermodynamic stability of the (U,Zr)(Al,Si) 3 phase. Heat treatments at 600 deg. C were undertaken and samples were analyzed by means of XRD, EPMA and EDS techniques. A remarkable conclusion is that addition of 0.3 at.% Si in the (U,Zr)(Al,Si) 3 phase reduces in 2.7 at.% the necessary Zr content to inhibit its transformation to U(Al,Si) 4 .

Disordering and amorphization of Zr3Al by 3.8 MeV Zr3+ ion bombardment

International Nuclear Information System (INIS)

Chen, F.C.; Ardell, A.J.

1991-01-01

The ordered intermetallic compound Zr 3 Al was irradiated with 3. 8 MeV Zr 3+ ions at various fluences up to 5 x 10 12 tons/mm 2 at a temperature of 250 degrees C and the irradiation- induced microstructures were investigated by transmission electron microscopy. Disordering began at the lowest dose, 0.0033 dpa, and complete loss of chemical long-range order occurred at a dose of 0.33 dpa. The onset of amorphization was also observed at this dose. Electron diffraction patterns from irradiated samples showed satellite reflections along in thin foils in [100] orientation and streaking along in foils oriented [011]. These diffraction effects are attributed to the presence of irradiation-induced microstructural defects that, when imaged in dark field, resemble rows of dislocation loops. A model of these arrays of loops, which are suggested to have Burgers vectors of the Frank type, is proposed. The model accounts for the contrast effects observed in the images and the streaking and satellites seen in the diffraction patterns. At the highest dose, 1.6 dpa, a new phase, Zr 5 Al 3 , appeared unexpectedly, most likely as a consequence of irradiation-induced solute segregation

Structural and catalytic characterization of mechanical mixtures of Pt/WOx-ZrO{sub 2} and Al{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Contreras, J.L., E-mail: jlcl@correo.azc.uam.m [Universidad Autonoma Metropolitana-Azcapotzalco, CBI, Dpto. Energia, Av. Sn. Pablo 180, Col. Reynosa, C.P. 02200, Mexico, DF (Mexico); Fuentes, G.A. [Universidad Autonoma Metropolitana-Iztapalapa, CBI, Depto. de IPH C.P. 09340, Mexico, DF (Mexico); Navarrete, J.; Vazquez, A. [Instituto Mexicano del Petroleo, IBP, Ger. de Catalizadores, Eje Central Lazaro Cardenas No. 152, C.P. 07300, Mexico, DF (Mexico); Zeifert, B.; Salmones, J. [Instituto Politecnico Nacional Mexico, ESIQIE, Laboratorio de Catalisis y Materiales, C.P. 07738, Mexico, DF (Mexico); Nuno, L. [Universidad Autonoma Metropolitana-Azcapotzalco, CBI, Dpto. Energia, Av. Sn. Pablo 180, Col. Reynosa, C.P. 02200, Mexico, DF (Mexico)

2010-04-16

The effect of the Bronsted/Lewis acid ratio on isomerization of n-heptane using Al{sub 2}O{sub 3} as a source of Lewis acidity and WOx/ZrO{sub 2} as a source of Bronsted and Lewis acidity was studied and controlled using mechanical mixtures of these solids. These mixtures were characterized by surface area, infrared spectroscopy of pyridine, X-ray diffraction and Raman spectroscopy. It was found that the presence of W=O stretching mode which was consistent with the presence of oxotungstate species which were the precursors of the acid sites. It was found out that as the oxotungstate structures increased, the selectivity to n-heptane isomers increased while the hydrocracking and dehydrocyclization selectivity decreased. The presence of Bronsted acidity of the WOx/ZrO{sub 2} domains, the increase of Knudsen diffusivity and the loss of Pt metallic area by strong interaction of the Pt with the WOx/ZrO{sub 2} explain this catalytic behavior.

Development of an elevated temperature aluminum alloy containing Al3X-type dispersed phases

International Nuclear Information System (INIS)

Zedalis, M.S.

1985-01-01

The extents of solid solubility in the equilibrium, tetragonal Al 3 X-type dispersed phases (X represents binary and ternary combinations of Hf, Ti, V, and Zr) were examined using powder x-ray diffraction methods. Minimum lattice disregistry (delta) with the Al(ss) matrix was achieved by maximizing the amount of Ti or V added to the Al 3 Hf and/or Al 3 Zr phases without forming a co-intermetallic compound exhibiting a DO 22 crystal structure. In comparison to Al 3 Zr, with a (delta) equal to 2.88%, the addition of V to Al 3 Zr in the ratio 7:1, i.e., Al 3 (v/sub 0.875/Zr/sub 0.125/), results in a decrease in (delta) by approximately 17%. Electron diffraction revealed that the addition of V to the metastable cubic (L1 2 ) Al 3 Zr phase also resulted in a reduction in the lattice disregistry across the precipitate/matrix boundary. In comparison with the cubic Al 3 Zr phase, with a (delta) of approximately 1.0%, the Al 3 (V/sub 0.875/Zr/sub 0.125/) phase exhibits a mismatch of approximately -0.14%. The cubic Al 3 (V/sub 0.875/Zr/sub 0.125/) phase was observed by TEM to be substantially more stable, i.e., resist transformation to the equilibrium tetragonal phase, when compared to the cubic Al 3 Zr phase. It is proposed that a reduction in lattice disregistry results in a decrease in the strain energy component of the system's total free energy. A systematic decrease in the coarsening rate with a reduction in the lattice disregistry for the cubic Al 3 Zr, Al 3 (V/sub 0.725/Zr/sub 0.275/) and Al 3 (V/sub 0.875/Zr/sub 0.125/) and tetragonal Al 3 Zr and Al 3 (V/sub 0.875/Zr/sub 0.125/) phases is proposed to be representative of a decrease in the interfacial energy across the precipitate/matrix boundary

ZrCu2P2 and HfCu2P2 phosphides and their crystal structure

International Nuclear Information System (INIS)

Lomnitskaya, Ya.F.

1986-01-01

Isostructural ZrCu 2 P 2 and HfCu 2 P 2 compounds are prepared for the first time. X-ray diffraction analysis (of powder, DRON-2.0 diffractometer, FeKsub(α) radiation) was used to study crystal structure of HfCu 2 P 2 phosphide belonging to the CaAl 2 Si 2 structural type (sp. group P anti 3 m 1, R=0.095). Lattice parameters the compounds are as follows: for ZrCu 2 P 2 a=0.3810(1), c=0.6184(5); for HfCu 2 P 2 a=0.3799(1), c=0.6160(2) (nm). Atomic parameters in the HfCu 2 P 2 structure and interatomic distances are determined

Communication: a relationship between hardness and flow stress of ordered Zr3Al polycrystals

International Nuclear Information System (INIS)

Schulson, E.M.; Roy, J.A.

1977-01-01

The purpose of this note is to describe a relationship between hardness and flow stress for the ordered L1$sub 2$ phase Zr$sub 3$Al, a possible structural material for use in nuclear power reactors. Experimental data obtained with the Zr-8.9% Al alloy lead to the conclusion that the hardness of polycrystalline Zr$sub 3$Al obeys an expression of the Hall-Petch form. When combined with a similar expression for flow stress, established previously, a simple relationship is obtained for flow stress in terms of hardness of well annealed material. Hardness measurements thus provide a rapid and inexpensive assessment of the strength of Zr$sub 3$Al. 8 refs

Atomic structure and formation of CuZrAl bulk metallic glasses and composites

International Nuclear Information System (INIS)

Kaban, I.; Jóvári, P.; Escher, B.; Tran, D.T.; Svensson, G.; Webb, M.A.; Regier, T.Z.; Kokotin, V.; Beuneu, B.; Gemming, T.; Eckert, J.

2015-01-01

Graphical abstract: Partial radial distribution functions for Cu 47.5 Zr 47.5 Al 5 metallic glass and relevant crystal structures. - Abstract: Cu 47.5 Zr 47.5 Al 5 metallic glass is studied experimentally by high-energy X-ray diffraction, neutron diffraction with isotopic substitution, electron diffraction and X-ray absorption spectroscopy. The atomic structure of the glass is modeled by reverse Monte-Carlo and molecular dynamics simulations. RMC modeling of seven experimental datasets enabled reliable separation of all partial pair distribution functions for Cu 47.5 Zr 47.5 Al 5 metallic glass. A peculiar structural feature of the ternary alloy is formation of the strong Al–Zr bonds, which are supposed to determine its high viscosity and enhanced bulk glass formation. Analysis of the local atomic order in Cu 47.5 Zr 47.5 Al 5 glass and Cu 10 Zr 7 , CuZr 2 and CuZr B2 crystalline structures elucidates their similarities and differences explaining the phase formation sequence by devitrification of the glass.

Forming of composites Al2O3-ZrO2 by direct coagulation casting method

International Nuclear Information System (INIS)

Tomaszewska-Grzeda, A.; Szafran, M.

2003-01-01

The role of enzymes in the DCC process in the decomposition of an appropriately selected substance which results in slow liberation over the whole volume of molecules changing the pH or also in the synthesis of salts modifying the double electric layer. The results of using the urease-urea system and the properties of ceramic casting slips, green samples and after sintering with aluminium oxide and Al 2 O 3 -nZrO 2 composites are presented in the paper. The obtained results of studies show a considerable probability of obtaining in the future of Al 2 O 3 -nZrO 2 composites of good strength parameters resulting from their high degree of thickening, providing that a deagglomeration method of nZrO 2 in the above presented processes will be elaborated. (author)

Local atomic structure of Zr-Cu and Zr-Cu-Al amorphous alloys investigated by EXAFS method

International Nuclear Information System (INIS)

Antonowicz, J.; Pietnoczka, A.; Zalewski, W.; Bacewicz, R.; Stoica, M.; Georgarakis, K.; Yavari, A.R.

2011-01-01

Research highlights: → Coordination number, interatomic distances and mean square atomic displacement in Zr-Cu and Zr-Cu-Al glasses. → Icosahedral symmetry in local atomic structure. → Deviation from random mixing behavior resulting from Al addition. - Abstract: We report on extended X-ray absorption fine structure (EXAFS) study of rapidly quenched Zr-Cu and Zr-Cu-Al glassy alloys. The local atomic order around Zr and Cu atoms was investigated. From the EXAFS data fitting the values of coordination number, interatomic distances and mean square atomic displacement were obtained for wide range of compositions. It was found that icosahedral symmetry rather than that of corresponding crystalline analogs dominates in the local atomic structure of Zr-Cu and Zr-Cu-Al amorphous alloys. Judging from bonding preferences we conclude that addition of Al as an alloying element results in considerable deviation from random mixing behavior observed in binary Zr-Cu alloys.

Microwave combustion synthesis of in situ Al{sub 2}O{sub 3} and Al{sub 3}Zr reinforced aluminum matrix composites

Energy Technology Data Exchange (ETDEWEB)

Zhu, Heguo, E-mail: zhg1200@sina.com [College of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Key Laboratory of Advanced Micro-Nano Materials and Technology, Jiangsu Province Higher Education Institutions, 210094 (China); Synergetic Center for Advanced Materials Research, Jiangsu Province Higher Education Institutions, 210094 (China); Hua, Bo; Cui, Tao; Huang, Jiewen; Li, Jianliang [College of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Xie, Zonghan, E-mail: zonghan.xie@adelaide.edu.au [School of Mechanical & Electrical Engineering, Wuhan Institute of Technology, Wuhan 430073 (China); School of Mechanical Engineering, University of Adelaide, SA 5005 (Australia)

2015-08-15

Al{sub 2}O{sub 3} and Al{sub 3}Zr reinforced aluminum matrix composites were fabricated from Al and ZrO{sub 2} powders by SiC assisted microwave combustion synthesis. The microstructure and reaction pathways were analyzed by using differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The results showed that the heating rate during microwave synthesis was very high and the entire process took several minutes and that the ignition temperature of the reaction was much lower than that of conventional methods. In addition, the resulting microstructure was found to be finer than that prepared by the conventional methods and no cracks can be seen in the Al{sub 3}Zr reinforcements. As such, the newly developed composites have potential for safety-critical applications where catastrophic failure is not tolerated.

Hydrogenation of FeCoZr-Al{sub 2}O{sub 3} nanocomposites studied by Moessbauer spectroscopy and magnetometry

Energy Technology Data Exchange (ETDEWEB)

Saad, A. [Al-Balqa Applied University, Appl. Science Department (Jordan); Kasiuk, J.; Fedotova, J., E-mail: Julia@hep.by [NC PHEP BSU (Belarus); Szilagyi, E. [KFKI Research Institute for Particle and Nuclear Physics (Hungary); Przewoznik, J.; Kapusta, Cz. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science (Poland); Marszalek, M. [Niewodniczanski Institute of Nuclear Physics PAN (Poland)

2009-02-15

Hydrogenation effects on crystalline and magnetic structure of nanocomposites (FeCoZr){sub x}(Al{sub 2}O{sub 3}){sub 100-x}, 38 {<=} x {<=} 63 at.% are studied by {sup 57}Fe Moessbauer spectroscopy and magnetometry. Variations of local structure, blocking temperature and mean FeCoZr nanoparticles' volume are discussed with respect to (i) composition and (ii) two competing processes-H{sub 2} incorporation and annealing-occurred during treatment in H{sub 2} plasma.

Band gap tuning of amorphous Al oxides by Zr alloying

DEFF Research Database (Denmark)

Canulescu, Stela; Jones, N. C.; Borca, C. N.

2016-01-01

minimum changes non-linearly as well.Fitting of the energy band gap values resulted in a bowing parameter of 2 eV. The band gap bowing of themixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction bandminimum of anodized Al2O3.......The optical band gap and electronic structure of amorphous Al-Zr mixed oxides, with Zr content ranging from4.8 to 21.9% were determined using vacuum ultraviolet (VUV) and X-ray absorption spectroscopy (XAS). Thelight scattering by the nano-porous structure of alumina at low wavelengths...... was estimated based on the Miescattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on Zr content deviatesfrom linearity and decreases from 7.3 eV for pure anodized Al2O3 to 6.45 eV for Al-Zr mixed oxide with Zrcontent of 21.9%. With increasing Zr content, the conduction band...

Study of dielectric property on ZrO2 and Al doped ZrO2 nanoparticles

International Nuclear Information System (INIS)

Catherine Siriya Pushpa, K.; Mangayarkarasi, K.; Ravichandran, A.T.; Xavier, A. Robert; Nagabushana, B.M.

2014-01-01

A solution combustion process was used to synthesize ZrO 2 and Al doped ZrO 2 nanoparticles by using Zirconium nitrate and aluminium nitrate as the oxidizer and glycine as fuel. The prepared samples were characterized by several techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-visible spectroscopy (UV-vis). The dielectric values of the pelletized samples were examined at room temperature as the function of frequency. XRD shows the structure of the prepared and doped samples. The SEM shows the surface morphology of the pure and doped ZrO 2 nanoparticles. The dielectric property enhances with increase of Al concentration, which is useful in dielectric gates. (author)

Synthesizing (ZrAl3 + AlN)/Mg-Al composites by a 'matrix exchange' method

Science.gov (United States)

Gao, Tong; Li, Zengqiang; Hu, Kaiqi; Han, Mengxia; Liu, Xiangfa

2018-06-01

A method named 'matrix exchange' to synthesize ZrAl3 and AlN reinforced Mg-Al composite was developed in this paper. By inserting Al-10ZrN master alloy into Mg matrix and reheating the cooled ingot to 550 °C, Al and Mg atoms diffuse to the opposite side. As a result, liquid melt occurs once the interface areas reach to proper compositions. Then dissolved Al atoms react with ZrN, leading to the in-situ formation of ZrAl3 and AlN particles, while the Al matrix is finally replaced by Mg. This study provides a new insight for preparing Mg composites.

Zr3NiSb7: a new antimony-enriched ZrSb2 derivative

Directory of Open Access Journals (Sweden)

V. Romaka

2008-08-01

Full Text Available Single crystals of trizirconium nickel heptaantimonide were synthesized from the constituent elements by arc-melting. The compound crystallizes in a unique structure type and belongs to the family of two-layer structures. All crystallographically unique atoms (3 × Zr, 1 × Ni and 7 × Sb are located at sites with m symmetry. The structure contains `Zr2Ni2Sb5' and `Zr4Sb9' fragments and might be described as a new ZrSb2 derivative with a high Sb content.

Band gap tuning of amorphous Al oxides by Zr alloying

Energy Technology Data Exchange (ETDEWEB)

Canulescu, S., E-mail: stec@fotonik.dtu.dk; Schou, J. [Department of Photonics Engineering, Technical University of Denmark, 4000 Roskilde (Denmark); Jones, N. C.; Hoffmann, S. V. [ISA, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus (Denmark); Borca, C. N.; Piamonteze, C. [Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Rechendorff, K.; Nielsen, L. P.; Almtoft, K. P. [Danish Technological Institute, Kongsvang Alle 29, 8000 Aarhus (Denmark); Gudla, V. C.; Bordo, K.; Ambat, R. [Department of Mechanical Engineering, Technical University of Denmark, 2800 Kgs-Lyngby (Denmark)

2016-08-29

The optical band gap and electronic structure of amorphous Al-Zr mixed oxides with Zr content ranging from 4.8 to 21.9% were determined using vacuum ultraviolet and X-ray absorption spectroscopy. The light scattering by the nano-porous structure of alumina at low wavelengths was estimated based on the Mie scattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on the Zr content deviates from linearity and decreases from 7.3 eV for pure anodized Al{sub 2}O{sub 3} to 6.45 eV for Al-Zr mixed oxides with a Zr content of 21.9%. With increasing Zr content, the conduction band minimum changes non-linearly as well. Fitting of the energy band gap values resulted in a bowing parameter of ∼2 eV. The band gap bowing of the mixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction band minimum of anodized Al{sub 2}O{sub 3}.

Refractories in the Al2O3-ZrO2-SiO2 system

International Nuclear Information System (INIS)

Banerjee, S.P.; Bhadra, A.K.; Sircar, N.R.

1978-01-01

The effect of addition of ZrO 2 in different proportions in the refractories of the Al 2 O 3 -SiO 2 system was studied. The investigation was confined to two broad ranges of compositions incorporating zirconia (15-30 percent and 80-85 percent) in the Al 2 O 3 -ZrO 2 -SiO 2 system. The overall attainment of properties is dependent upon the mode of fabrication and firing, and bears a relationship with the phase assemblages and the relative proportion thereof. Of the different characteristics, the trend of dissociation of zircon has been found to be specially significant vis-a-vis the temperature of firing and thermal shock resistance. Reassociation of the dissociated products has been ascribed to bring forth improved resistance to thermal spalling. The different products developed during this investigation are considered to be very promising which find useful applications in view of the properties attained by them. (auth.)

Development and characterization of nickel catalysts supported in CeO2-ZrO2-Al2O3, CeO2-La2O3-Al2O3 e ZrO2-La2O3-Al2O3 matrixes evaluated for methane reforming reactions

International Nuclear Information System (INIS)

Abreu, Amanda Jordão de

2012-01-01

Nowadays, the methane reforming is large interest industrial for the take advantage of these gas in production the hydrogen and synthesis gas (syngas). Among in the reactions of methane stand of the reactions steam reforming and carbon dioxide reforming of methane. The main catalysts uses in the methane reforming is Ni/Al 2 O 3 . However, the supported-nickel catalyst is susceptible to the deactivation or the destruction by coke deposition. The carbon dissolves in the nickel crystallite and its diffuses through the nickel, leading for formation of the carbon whiskers, which results in fragmentation of the catalyst. Modification of such catalysts, like incorporation of suitable promoters, is desirable to achieve reduction of the methane hydrogenolysis and/or promotion of the carbon gasification. Catalysts 5%Ni/Al 2 O 3 supported on solid solutions formed by ZrO 2 -CeO 2 , La 2 O 3 and CeO 2 -ZrO 2 -La 2 O 3 were prepared, characterized and evaluated in reactions steam and carbon dioxide reforming and partial oxidation of methane with objective the value effect loading solution solid in support. The supports were prepared by co-precipitation method and catalysts were prepared by impregnation method and calcined at 500 deg C. The supports and catalysts were characterized by Nitrogen Adsorption, method -rays diffraction (XRD), X-rays dispersive spectroscopy (XDS), spectroscopy in the region of the ultraviolet and the visible (UV-vis NIR) to and temperature programmed reduction (TPR), Raman Spectroscopy, X-ray absorption spectroscopy and Thermogravimetric Analysis. After all the catalytic reactions check which the addition of solid solution is beneficial for Ni/Al 2 O 3 catalysts and the best catalysts are Ni/CeO 2 -La 2 O 3 -Al 2 O 3 . (author)

Compressive strain-dependent bending strength property of Al{sub 2}O{sub 3}-ZrO{sub 2} (1.5 mol% Y{sub 2}O{sub 3}) composites performance by HIP

Energy Technology Data Exchange (ETDEWEB)

Reyes-Rojas, A. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Miguel de Cervantes 120, Complejo Industrial Chihuahua, Cd. de Chihuahua, Chihuahua (Mexico)], E-mail: armando_reyesmx@yahoo.com.mx; Esparza-Ponce, H. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Miguel de Cervantes 120, Complejo Industrial Chihuahua, Cd. de Chihuahua, Chihuahua (Mexico); De la Torre, S.D. [Centro de Investigacion e Innovacion Tecnologica (CIITEC)-IPN, D.F. Mexico (Mexico); Torres-Moye, E. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Miguel de Cervantes 120, Complejo Industrial Chihuahua, Cd. de Chihuahua, Chihuahua (Mexico)

2009-04-15

Nanometric powders and sintered ceramics of Al{sub 2}O{sub 3}-ZrO{sub 2} (1.5 mol% Y{sub 2}O{sub 3}) prepared by hot isostatic pressing HIP have been studied. A detailed crystallographic study has been performed through X-ray diffraction, Williamson-Hall method, Rietveld method and high-resolution electron microscopy HREM analysis. The crystallographic structure data, such as domain size, lattice parameters, wt% phase, and micro-strain direction have been obtained using Rietveld refinement and Williamson-Hall methods. The results revealed that the compressive strain ({epsilon}) increased from 0.56 to 1.18 (10{sup -3}) as the t-ZrO{sub 2} content increased too. The HREM interface study conducted along the [0 0 0 1]Al{sub 2}O{sub 3}||[0 0 1]ZrO{sub 2} zone axis revealed a micro-strain lattice distortion accumulated at the grain boundary due to the ZrO{sub 2} martensitic phase transformation on cooling, t-ZrO{sub 2} grains coalescence and to the grain growth of {alpha}-Al{sub 2}O{sub 3} which cause elongated tetragonal crystals. Micro-strain lattice distortion is adjusted by the shear displacements of the planes (1 1 0) and (11-bar0) along [1-bar10] and [1-bar1-bar0] crystallographic directions, respectively; these planes are arrested by the (101-bar0) alumina plane. In this case, semi-coherent interfaces were observed along the grain boundary. It is verified that the bending strength increased in connection with the strain accumulation and amount of tetragonal structure.

In situ formation of CA6 platelets in Al2O3 and Al2O3/ZrO2 matrices

OpenAIRE

Belmonte , M.; SÁnchez-Herencia , A.; Moreno , R.; Miranzo , P.; Moya , J.; Tomsia , A.

1993-01-01

Al2O3 and Al2O3/ZrO2 compacts containing CaO as a dopant have been sintered under different conditions and atmospheres: air, high vacuum (> 10-6torr). SEM observations have been made on the polished surfaces of sintered and also of annealed samples. Only after the annealing treatment in air at temperatures ranging from 1400° to 1 500°C, a massive formation of CA6 platelets was detected in samples sintered in low oxygen partial pressure atmospheres.ln order to clarify the mechanism of formatio...

First-principles characterization of a heteroceramic interface: ZrO2(001) deposited on an alpha-Al2O3(1(1)over-bar02) substrate

DEFF Research Database (Denmark)

Christensen, Asbjørn; Carter, Emily A.

2000-01-01

We have studied an alumina/zirconia interface using the all-electron projector augmented wave formalism within density functional theory. We present the electronic, structural, and energetic properties of the ZrO2(001)/(alpha -Al2O3(1 (1) over bar 02) interface as well as of the free alpha -Al2O3......(1 (1) over bar 02) and ZrO2(001) surfaces. We find that the generalized gradient correction significantly lowers the oxide surface energies, compared to values obtained by the local density approximation. The monoclinic-tetragonal transition in ZrO2(001) thin films is discussed as well as strain...... effects involved in the interface formation. The stoichiometric alumina/zirconia interface is found to be weakly bonded, regardless of the film thickness, and the ZrO2(001)/alpha -Al2O3(1 (1) over bar 02) interface has a rather epitaxial character, due to a low lattice mismatch of similar to4%. The impact...

Epitaxial thin-film growth of Ruddlesden-Popper-type Ba{sub 3}Zr{sub 2}O{sub 7} from a BaZrO{sub 3} target by pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Butt, Shariqa Hassan; Rafique, M.S.; Siraj, K.; Latif, A.; Afzal, Amina [University of Engineering and Technology, Laser and Optronics Centre, Department of Physics, Lahore (Pakistan); Awan, M.S. [Ibn-e-Sina Institute of Science and Technology (ISIT), Islamabad (Pakistan); Bashir, Shazia [Government College University, Centre for Advanced Studies in Physics, Lahore (Pakistan); Iqbal, Nida [Universiti Teknologi Malaysia, Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Johor Bahru, Johor (Malaysia)

2016-07-15

Ruddlesden-Popper Ba{sub 3}Zr{sub 2}O{sub 7} thin films have been synthesized via pulsed laser deposition (PLD) technique. The optimization of deposition parameters in PLD enables the formation of thin film of metastable Ba{sub 3}Zr{sub 2}O{sub 7} phase from BaZrO{sub 3} target. In order to see the post-annealing effects on the structural and optical properties, the deposited Ba{sub 3}Zr{sub 2}O{sub 7} thin films were annealed at 500, 600 and 800 C. X-ray diffraction (XRD) reveals the formation of Ba{sub 3}Zr{sub 2}O{sub 7} phase with tetragonal structure. The changes in the surface of the deposited films were analysed by FE-SEM and AFM. The thin film post-annealed at 500 C exhibited the best structural, optical and surface properties. Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. The XPS results show that Ba, Zr and O exist mainly in the form of Ba{sub 3}Zr{sub 2}O{sub 7} Ruddlesden-Popper-type perovskite structure. (orig.)

Electronic structure and phase stability during martensitic transformation in Al-doped ZrCu intermetallics

International Nuclear Information System (INIS)

Qiu Feng; Shen Ping; Liu Tao; Lin Qiaoli; Jiang Qichuan

2010-01-01

Martensitic transformation, phase stability and electronic structure of Al-doped ZrCu intermetallics were investigated by experiments and first-principles calculations using the pseudopotentials plane wave method. The formation energy calculations indicate that the stability of the ZrCu phase increases with the increasing Al content. Al plays a decisive role in controlling the formation and microstructures of the martensite phases in Zr-Cu-Al alloys. The total energy difference between ZrCu (B2) austenite and ZrCu martensite plays an important role in the martensitic transformation. The phase stability is dependent on its electronic structure. The densities of states (DOS) of the intermetallics were discussed in detail.

The corrosion behaviour of Zr3Al-based alloys

International Nuclear Information System (INIS)

Murphy, E.V.; Wieler, R.

1977-07-01

The corrosion resistance of several zirconium-aluminum alloys with aluminum contents ranging from 7.6 to 9.6 wt% was examined in 300 deg C and 325 deg C water, 350 deg C and 400 deg C steam and in air and wet CO 2 at 325 deg C and 400 deg C. In the transformed alloys there are three phases present, αZr, Zr 2 Al and Zr 3 Al of which the αZr phase is the least corrosion resistant. The most important factor controlling the corrosion behaviour of these alloys was found to be the size, distribution and amount of the αZr phase in the transformed alloys, which in turn was dependent upon the microstructural scale of the untransformed alloys

Effect of the Size of Al3(Sc,Zr) Precipitates on the Structure of Multi-Directionally Isothermally Forged Al-Mg-Sc-Zr Alloy

Science.gov (United States)

Sitdikov, O. Sh.; Avtokratova, E. V.; Mukhametdinova, O. E.; Garipova, R. N.; Markushev, M. V.

2017-12-01

The effect of Al3(Sc,Zr) dispersoids on the evolution of the cast Al-Mg-Sc-Zr alloy structure under multi-directional isothermal forging (MIF) has been investigated. The alloy, which has an equiaxed grain structure with a grain size of 25 μm and contains dispersoids 5-10 and 20-50 nm in size after onestage (at 360°C for 6 h) and two-stage (360°C for 6 h + 520°C for 1 h) annealing, respectively, was deformed at 325°C ( 0.65 T m) up to cumulative strains of e = 8.4. In the initial stages of MIF, new fine (sub)grains surrounded by low-angle and high-angle boundaries (HABs) were formed near the initial grain boundaries. With increasing strain, the volume fraction and misorientation of these crystallites increased, which led to the replacement of a coarse-grained structure with a fine-grained one with a grain size of 1.5-2.0 μm. Dynamic recrystallization occurred in accordance to a continuous mechanism and was controlled by the interaction of lattice dislocations and/or (sub)grain boundaries with dispersoids that effectively inhibited the migration of boundaries, as well as the rearrangement of lattice dislocations and their annihilation. The particle size and the density of their distribution significantly affected the parameters of the evolved structure; in an alloy with smaller particles, a structure with a smaller grain size and a larger HAB fraction developed.

Effects of Al addition on atomic structure of Cu-Zr metallic glass

Science.gov (United States)

Li, Feng; Zhang, Huajian; Liu, Xiongjun; Dong, Yuecheng; Yu, Chunyan; Lu, Zhaoping

2018-02-01

The atomic structures of Cu52Zr48 and Cu45Zr48Al7 metallic glasses (MGs) have been studied by molecular dynamic simulations. The results reveal that the molar volume of the Cu45Zr48Al7 MG is smaller than that of the Cu52Zr48 MG, although the size of the Al atom is larger than that of the Cu atom, implying an enhanced atomic packing density achieved by introducing Al into the ternary MG. Bond shortening in unlike atomic pairs Zr-Al and Cu-Al is observed in the Cu45Zr48Al7 MG, which is attributed to strong interactions between Al and (Zr, Cu) atoms. Meanwhile, the atomic packing efficiency is enhanced by the minor addition of Al. Compared with the Cu52Zr48 binary MG, the potential energy of the ternary MG decreases and the glass transition temperature increases. Structural analyses indicate that more Cu- and Al-centered full icosahedral clusters emerge in the Cu45Zr48Al7 MG as some Cu atoms are substituted by Al. Furthermore, the addition of Al leads to more icosahedral medium-range orders in the ternary MG. The increase of full icosahedral clusters and the enhancement of the packing density are responsible for the improved glass-forming ability of Cu45Zr48Al7.

Calculation of Gibbs energy of Zr-Al-Ni, Zr-Al-Cu, Al-Ni-Cu and Zr-Al-Ni-Cu liquid alloys based on quasiregular solution model

International Nuclear Information System (INIS)

Li, H.Q.; Yang, Y.S.; Tong, W.H.; Wang, Z.Y.

2007-01-01

With the effects of electronic structure and atomic size being introduced, the mixing enthalpy as well as the Gibbs energy of the ternary Zr-Al-Cu, Ni-Al-Cu, Zr-Ni-Al and quaternary Zr-Al-Ni-Cu systems are calculated based on quasiregular solution model. The computed results agree well with the experimental data. The sequence of Gibbs energies of different systems is: G Zr-Al-Ni-Cu Zr-Al-Ni Zr-Al-Cu Cu-Al-Ni . To Zr-Al-Cu, Ni-Al-Cu and Zr-Ni-Al, the lowest Gibbs energy locates in the composition range of X Zr 0.39-0.61, X Al = 0.38-0.61; X Ni = 0.39-0.61, X Al = 0.38-0.60 and X Zr = 0.32-0.67, X Al = 0.32-0.66, respectively. And to the Zr-Ni-Al-Cu system with 66.67% Zr, the lowest Gibbs energy is obtained in the region of X Al = 0.63-0.80, X Ni = 0.14-0.24

Influence of small additions of Sc and Zr on structure and mechanical properties of Al-Zn-Mg-Cu alloy

International Nuclear Information System (INIS)

Kajgorodova, L.I.; Sel'nikhina, E.I.; Tkachenko, E.A.; Senatorova, O.G.

1996-01-01

A study was made into Sc and Zr addition effects on grain structure formation, supersaturated solid solution decomposition and mechanical properties of Al-7%Zn-2%Mg-1.2%Cu alloy. It is shown that grain structure is determined by volume fraction and distribution character of disperse particles of Al 3 Sc and Al 3 (Sc 1-x Zr x ). The reason for additives influence on decomposition kinetics during natural and artificial ageing are revealed. The structural factors responsible for the enhancement of mechanical properties on alloying are discussed. 17 refs.; 5 figs.; 2 tabs

Hydrothermal-precipitation preparation of CdS@(Er3+:Y3Al5O12/ZrO2) coated composite and sonocatalytic degradation of caffeine.

Science.gov (United States)

Huang, Yingying; Wang, Guowei; Zhang, Hongbo; Li, Guanshu; Fang, Dawei; Wang, Jun; Song, Youtao

2017-07-01

Here, we reported a novel method to dispose caffeine by means of ultrasound irradiation combinated with CdS@(Er 3+ :Y 3 Al 5 O 12 /ZrO 2 ) coated composite as sonocatalyst. The CdS@(Er 3+ :Y 3 Al 5 O 12 /ZrO 2 ) was synthesized via hydrothermal-precipitation method and then characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and UV-vis diffuse reflectance spectra (DRS). After that, the sonocatalytic degradation of caffeine in aqueous solution was conducted adopting CdS@(Er 3+ :Y 3 Al 5 O 12 /ZrO 2 ) and CdS@ZrO 2 coated composites as sonocatalysts. In addition, some influencing factors such as CdS and ZrO 2 molar proportion, caffeine concentration, ultrasonic irradiation time, sonocatalyst dosage and addition of several inorganic oxidants on sonocatalytic degradation of caffeine were investigated by using UV-vis spectra and gas chromatograph. The experimental results showed that the presence of Er 3+ :Y 3 Al 5 O 12 could effectively improve the sonocatalytic degradation activity of CdS@ZrO 2 . To a certain extent some inorganic oxidants can also enhance sonocatalytic degradation of caffeine in the presence of CdS@(Er 3+ :Y 3 Al 5 O 12 /ZrO 2 ). The best sonocatalytic degradation ratio (94.00%) of caffeine could be obtained when the conditions of 5.00mg/L caffeine, 1.00g/L prepared CdS@(Er 3+ :Y 3 Al 5 O 12 /ZrO 2 ), 10.00mmol/LK 2 S 2 O 8 , 180min ultrasonic irradiation (40kHz frequency and 50W output power), 100mL total volume and 25-28°C temperature were adopted. It seems that the method of sonocatalytic degradation caused by CdS@(Er 3+ :Y 3 Al 5 O 12 /ZrO 2 ) displayspotentialadvantages in disposing caffeine. Copyright © 2017 Elsevier B.V. All rights reserved.

Structural study of Zr-based metallic glasses

International Nuclear Information System (INIS)

Matsubara, E.; Ichitsubo, T.; Saida, J.; Kohara, S.; Ohsumi, H.

2007-01-01

Structures of Zr 70 Ni 20 Al 10 , Zr 70 Cu 20 Al 10 , Zr 70 Cu 30 and Zr 70 Ni 30 amorphous alloys were analyzed by high-energy X-ray diffraction. The relatively stable Zr 2 Cu amorphous alloy shows a local atom arrangement different from the Zr 2 Cu crystalline phase. By contrast, the less stable Zr 70 Ni 30 amorphous alloy has a structure similar to Zr 2 Ni. In the Zr 70 Cu 20 Al 10 metallic glass, Zr-Al nearest neighbor pairs are introduced in the amorphous structure. In the Zr 70 Ni 20 Al 10 metallic glass, the strong correlation between Zr-Ni pairs is drastically modified by the formation of Zr-Al pairs. The presence of Zr-Al pairs in the ternary alloys suppresses the crystallization and stabilizes the glassy state

Microstructure and mechanical properties investigation of in situ TiB2 and ZrB2 reinforced Al-4Cu composites

Science.gov (United States)

Lutfi Anis, Ahmad; Ramli, Rosmamuhammadani; Darham, Widyani; Zakaria, Azlan; Talari, Mahesh Kumar

2016-02-01

Conventional Al-Cu alloys exhibit coarse grain structure leading to inferior mechanical properties in as-cast condition. Expensive thermo-mechanical treatments are needed to improve microstructure and corresponding mechanical properties. In situ Al-based composites were developed to improve mechanical properties by dispersion strengthening and grain refinement obtained by the presence of particulates in the melt during solidification. In this work Al-4Cu - 3TiB2 and Al-4Cu-3ZrB2 in situ composites were prepared by liquid casting method. XRD, electron microscopy and mechanical tests were performed on suitably sectioned and metallographically prepared surfaces to investigate the phase distribution, hardness and tensile properties. It was found that the reinforcement particles were segregated along the grain boundaries of Al dendrites. Tensile fracture morphology for both Al-4Cu - 3TiB2 and Al-4Cu-3ZrB2 were analyzed and compared to determine the fracture propagation mechanism in the composites. Al-4Cu-3ZrB2 in situ composites displayed higher strength and hardness compared to Al-4Cu-3TiB2 which could be ascribed to the stronger interfacial bonding between the Al dendrites and ZrB2 particulates as evidenced from fractographs.

High-Temperature Tensile and Tribological Behavior of Hybrid (ZrB2+Al3Zr)/AA5052 In Situ Composite

Science.gov (United States)

Gautam, G.; Kumar, N.; Mohan, A.; Gautam, R. K.; Mohan, S.

2016-09-01

During service life, components such as piston, cylinder blocks, brakes, and discs/drums, have to work under high-temperature conditions. In order to have appropriate material for such applications high-temperature studies are important. Hybrid (ZrB2+Al3Zr)/AA5052 in situ composite has been investigated from ambient to 523 K (250 °C) at an interval of 50 deg. (ZrB2+Al3Zr)/AA5052 in situ composite has been fabricated by the direct melt reaction of AA5052 alloy with zirconium and boron salts. Microstructure studies show refinement in the grain size of base alloy on in situ formation of reinforcement particles. Al3Zr particles are observed in rectangular and polyhedron shapes. It is observed from the tensile studies that ultimate tensile strength, yield strength, and percentage elongation decrease with increase in test temperature. Similar kind of behavior is also observed for flow curve properties. The tensile results have also been correlated with fractography. Wear and friction results indicate that the wear rate increases with increase in normal load, whereas coefficient of friction shows decreasing trend. With increasing test temperature, wear rate exhibits a typical phenomenon. After an initial increase, wear rate follows a decreasing trend up to 423 K (150 °C), and finally a rapid increase is observed, whereas coefficient of friction increases continuously with increase in test temperature. The mechanisms responsible for the variation of wear and friction with different temperatures have been discussed in detail with the help of worn surfaces studies under scanning electron microscope (SEM) & 3D-profilometer and debris analysis by XRD.

Mechanical properties and bio-tribological behaviors of novel beta-Zr-type Zr-Al-Fe-Nb alloys for biomedical applications.

Science.gov (United States)

Hua, Nengbin; Chen, Wenzhe; Zhang, Lei; Li, Guanghui; Liao, Zhenlong; Lin, Yan

2017-07-01

The present study prepares novel Zr 70+x Al 5 Fe 15-x Nb 10 (x=0, 5) alloys by arc-melting for potential biomedical application. The mechanical properties and bio-tribological behaviors of the Zr-based alloys are evaluated and compared with biomedical pure Zr. The as-prepared alloys exhibit a microstructure containing a micrometer-sized dendritic beta-Zr phase dispersed in a Zr 2 Fe-typed matrix. It is found that increasing the content of Zr is favorable for the mechanical compatibility with a combination of low Young's modulus, large plasticity, and high compressive strength. The wear resistance of the Zr-Al-Fe-Nb alloys in air and phosphate buffer saline (PBS) solution is superior to that of pure Zr. The wear mechanism of Zr-based alloys sliding in air is controlled by oxidation and abrasive wear whereas that sliding in PBS is controlled by synergistic effects of the abrasive and corrosive wear. Electrochemical measurements demonstrate that the Zr-based alloys are corrosion resistant in PBS. Their bio-corrosion resistance is improved with the increase in Zr content, which is attributed to the enrichment in Zr and decrease in Al concentration in the surface passive film of alloys. The Zr 75 Al 5 Fe 10 Nb 10 exhibits the best corrosion resistance in PBS, which contributes to its superior wear resistance in a simulated body environment. The combination of good mechanical properties, corrosion resistance, and biotribological behaviors of the Zr-Al-Fe-Nb alloys offers them potential advantages in biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Structural study of Zr-based metallic glasses

Energy Technology Data Exchange (ETDEWEB)

Matsubara, E. [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan)]. E-mail: e.matsubara@materials.mbox.media.kyoto-u.ac.jp; Ichitsubo, T. [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Saida, J. [Center of Interdisciplinary Research, Tohoku University, Sendai 980-8578 (Japan); Kohara, S. [JASRI, SPring-8, Sayo-gun, Hyogo 679-5198 (Japan); Ohsumi, H. [JASRI, SPring-8, Sayo-gun, Hyogo 679-5198 (Japan)

2007-05-31

Structures of Zr{sub 70}Ni{sub 20}Al{sub 10}, Zr{sub 70}Cu{sub 20}Al{sub 10}, Zr{sub 70}Cu{sub 30} and Zr{sub 70}Ni{sub 30} amorphous alloys were analyzed by high-energy X-ray diffraction. The relatively stable Zr{sub 2}Cu amorphous alloy shows a local atom arrangement different from the Zr{sub 2}Cu crystalline phase. By contrast, the less stable Zr{sub 70}Ni{sub 30} amorphous alloy has a structure similar to Zr{sub 2}Ni. In the Zr{sub 70}Cu{sub 20}Al{sub 10} metallic glass, Zr-Al nearest neighbor pairs are introduced in the amorphous structure. In the Zr{sub 70}Ni{sub 20}Al{sub 10} metallic glass, the strong correlation between Zr-Ni pairs is drastically modified by the formation of Zr-Al pairs. The presence of Zr-Al pairs in the ternary alloys suppresses the crystallization and stabilizes the glassy state.

Superplastic forming of rapid solidification processed Al-4Li-0.2Zr

International Nuclear Information System (INIS)

Meschter, P.J.; Lederich, R.J.; Sastry, S.M.L.

1987-01-01

Aluminum-4 wt pct lithium alloys are attractive as structural materials because they are 13 to 14 pct less dense and have 25 pct larger elastic moduli than high-strength 2XXX-and 7XXX-series aluminum alloys. These low-density alloys can be produced only by rapid solidification processing (RSP). Successful RSP of Al-4Li-0.2Zr, Al-4Li-1Mg-0.2Zr, and Al-4Li-1Cu-0.2Zr alloys with strengths similar to that of 7075-T76 has recently been demonstrated. Net-shaped processing techniques such as superplastic forming are capable of producing complex structural elements while minimizing usage of expensive material; thus, these techniques are particularly applicable to Al-Li alloys. The purpose of this study was to determine the conditions of strain rate and temperature under which RSP Al-4Li alloys could be superplastically formed

Influence of boron vacancies on phase stability, bonding and structure of MB2 (M  =  Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) with AlB2 type structure

International Nuclear Information System (INIS)

Dahlqvist, Martin; Rosen, Johanna; Jansson, Ulf

2015-01-01

Transition metal diborides in hexagonal AlB 2 type structure typically form stable MB 2 phases for group IV elements (M  =  Ti, Zr, Hf). For group V (M  =  V, Nb, Ta) and group VI (M  =  Cr, Mo, W) the stability is reduced and an alternative hexagonal rhombohedral MB 2 structure becomes more stable. In this work we investigate the effect of vacancies on the B-site in hexagonal MB 2 and its influence on the phase stability and the structure for TiB 2 , ZrB 2 , HfB 2 , VB 2 , NbB 2 , TaB 2 , CrB 2 , MoB 2 , and WB 2 using first-principles calculations. Selected phases are also analyzed with respect to electronic and bonding properties. We identify trends showing that MB 2 with M from group V and IV are stabilized when introducing B-vacancies, consistent with a decrease in the number of states at the Fermi level and by strengthening of the B–M interaction. The stabilization upon vacancy formation also increases when going from M in period 4 to period 6. For TiB 2 , ZrB 2 , and HfB 2 , introduction of B-vacancies have a destabilizing effect due to occupation of B–B antibonding orbitals close to the Fermi level and an increase in states at the Fermi level. (paper)

Correlative characterization of primary Al{sub 3}(Sc,Zr) phase in an Al–Zn–Mg based alloy

Energy Technology Data Exchange (ETDEWEB)

Li, J.H., E-mail: jie-hua.li@hotmail.com [Institute of Casting Research, Montanuniversität Leoben, A-8700 Leoben (Austria); Wiessner, M. [Materials Center Leoben Forschung GmbH, A-8700 Leoben (Austria); Albu, M. [Institute for Electron Microscopy and Nanoanalysis, Graz University of Technology, Center for Electron Microscopy (Austria); Wurster, S. [Department of Materials Physics, Montanuniversität Leoben, Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, A-8700 Leoben (Austria); Sartory, B. [Materials Center Leoben Forschung GmbH, A-8700 Leoben (Austria); Hofer, F. [Institute for Electron Microscopy and Nanoanalysis, Graz University of Technology, Center for Electron Microscopy (Austria); Schumacher, P. [Institute of Casting Research, Montanuniversität Leoben, A-8700 Leoben (Austria); Austrian Foundry Research Institute, A-8700 Leoben (Austria)

2015-04-15

Three-dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural information of primary Al{sub 3}(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (i) most primary Al{sub 3}(Sc,Zr) phases have a cubic three-dimensional morphology, with a size of about 6–10 μm, (ii) most primary Al{sub 3}(Sc,Zr) phases are located within the α-Al matrix, and exhibit a cube to cube orientation relationship with the α-Al matrix, and (iii) a layer by layer growth was observed within primary Al{sub 3}(Sc,Zr) phases. Al, Cu, Si and Fe are enriched in the α-Al matrix between the layers of cellular eutectic Al{sub 3}(Sc,Zr) phase, while Sc, Ti and Zr are enriched in small Al{sub 3}(Sc,Zr) phases. A peritectic reaction and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed to interpret the observed layer by layer growth. This paper demonstrates that the presence of impurities (Fe, Si, Cu, Ti) in the diffusion field surrounding the growing Al{sub 3}(Sc,Zr) particle enhances the heterogeneous nucleation of Al{sub 3}(Sc,Zr) phases. - Highlights: • Most fine cubic primary Al{sub 3}(Sc,Zr) phases were observed within the α-Al matrix. • A layer by layer growth within primary Al{sub 3}(Sc,Zr) phase was observed. • A peritectic and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed. • Impurities in diffusion fields enhance heterogeneous nucleation of Al{sub 3}(Sc,Zr)

Sequential evolution of different phases in metastable Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 (0.0 ≤ x ≤ 2.0) system: crucial role of reaction conditions.

Science.gov (United States)

Shukla, Rakesh; Sayed, Farheen N; Phapale, Suhas; Mishra, Ratikant; Tyagi, Avesh K

2013-07-15

The Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 (0.0 ≤ x ≤ 2.0) series was synthesized by the gel combustion method. This system exhibited the presence of a fluorite-type phase, along with a narrow biphasic region, depending upon the Ce/Gd content in the sample. Thermal stability of these new compounds under oxidizing and reducing conditions has been investigated. The products obtained on decomposition of Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 in oxidizing and reducing conditions were found to be entirely different. It was observed that in air the fluorite-type solid solutions of Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 composition undergo phase separation into perovskite GdAlO3 and fluorite-type solid solutions of Gd-Ce-Zr-O or Ce-Zr-Al-O depending upon the extent of Ce and Al substitution. On the other hand, Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 samples on heating under reducing conditions show a phase separation to CeAlO3 perovskite and a defect-fluorite of Gd2Zr2O7. The extent of metastability for a typical composition of Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O7 (nano), Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O(6.6) (heated under reduced conditions), Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O7 (heated in air at 1200 °C) has been experimentally determined employing a high temperature Calvet calorimeter. On the basis of thermodynamic stability data, it could be inferred that the formation of a more stable compound in the presence of two competing cations (i.e., Gd(3+) and Ce(3+)) is guided by the crystallographic stability.

Structural and Electrochemical Consequences of Al and Ga Cosubstitution in Li7La3Zr2O12 Solid Electrolytes.

Science.gov (United States)

Rettenwander, Daniel; Redhammer, Günther; Preishuber-Pflügl, Florian; Cheng, Lei; Miara, Lincoln; Wagner, Reinhard; Welzl, Andreas; Suard, Emmanuelle; Doeff, Marca M; Wilkening, Martin; Fleig, Jürgen; Amthauer, Georg

2016-04-12

Several "Beyond Li-Ion Battery" concepts such as all solid-state batteries and hybrid liquid/solid systems envision the use of a solid electrolyte to protect Li-metal anodes. These configurations are very attractive due to the possibility of exceptionally high energy densities and high (dis)charge rates, but they are far from being realized practically due to a number of issues including high interfacial resistance and difficulties associated with fabrication. One of the most promising solid electrolyte systems for these applications is Al or Ga stabilized Li 7 La 3 Zr 2 O 12 (LLZO) based on high ionic conductivities and apparent stability against reduction by Li metal. Nevertheless, the fabrication of dense LLZO membranes with high ionic conductivity and low interfacial resistances remains challenging; it definitely requires a better understanding of the structural and electrochemical properties. In this study, the phase transition from garnet ( Ia 3̅ d , No. 230) to "non-garnet" ( I 4̅3 d , No. 220) space group as a function of composition and the different sintering behavior of Ga and Al stabilized LLZO are identified as important factors in determining the electrochemical properties. The phase transition was located at an Al:Ga substitution ratio of 0.05:0.15 and is accompanied by a significant lowering of the activation energy for Li-ion transport to 0.26 eV. The phase transition combined with microstructural changes concomitant with an increase of the Ga/Al ratio continuously improves the Li-ion conductivity from 2.6 × 10 -4 S cm -1 to 1.2 × 10 -3 S cm -1 , which is close to the calculated maximum for garnet-type materials. The increase in Ga content is also associated with better densification and smaller grains and is accompanied by a change in the area specific resistance (ASR) from 78 to 24 Ω cm 2 , the lowest reported value for LLZO so far. These results illustrate that understanding the structure-properties relationships in this class of materials

Óxidos Mistos de Al2O3/ZrO2 como Inibidores de Corrosão do Aço SAE 1020

Directory of Open Access Journals (Sweden)

Marcelo Rodrigues da Silva

2014-01-01

Full Text Available This paper describes the use of Al2O3/ZrO2 mixed oxides synthesized by sol-gel process with different amounts of ZrO2 (5%, 10%, 15% and 20% by mass in the Al2O3 matrix and different temperatures of calcination, such as interesting inhibitor materials of corrosive processes of SAE 1020 steel. The materials were characterized by Infrared Spectroscopy Fourier Transform (FTIR and X-Ray Diffraction (XRD techniques. FTIR spectra show the typical Al-O and Zr-O bonds vibrations in the mixed oxides. The XRD patterns of the samples calcined at 800 °C and 1000 °C shows the ZrO2 tetragonal and γ-Al2O3 face-centered cubic (FCC phases. The corrosion tests showed that the SAE 1020 steel covered with mixed oxides have an anodic passive region, thereby inhibiting the corrosive processes on the metal surface. Furthermore, the found values for steel coated with mixed oxide synthesized indicate a decrease in corrosion potentials (Ecor and corrosion current (icor. With respect to different samples of mixed oxides, the sample with 20 % of ZrO2 in the Al2O3 matrix proved to be the best inhibitor of steel corrosion, with the lowest values of corrosion potential and corrosion current, - 1.32 V and 0.31 μA cm-2, respectively.

Microstructure and thermal stability of Cu/Zr0.3Al0.7N/Zr0.2Al0.8N/Al34O60N6 cermet-based solar selective absorbing coatings

Science.gov (United States)

Meng, Jian-ping; Guo, Rui-rui; Li, Hu; Zhao, Lu-ming; Liu, Xiao-peng; Li, Zhou

2018-05-01

Solar selective absorbing coatings play a valuable role in photo-thermal conversion for high efficiency concentrating solar power systems (CSP). In this paper, a novel Cu/Zr0.3Al0.7N/Zr0.2Al0.8N/Al34O60N6 cermet-based solar selective absorbing coating was successfully deposited by ion beam assisted deposition. The optical properties, microstructure and element distribution in depth were investigated by spectroscopic ellipsometry, UV-vis-NIR spectrophotometer, transmission electron microscope (TEM) and Auger electron spectroscopy (AES), respectively. A high absorptance of 0.953 and a low thermal emittance of 0.079 at 400 °C are obtained by the integral computation according to the whole reflectance from 300 nm to 28,800 nm. After annealing treatment at 400 °C (in vacuum) for 192 h, the deposited coating exhibits the high thermal stability. Whereas, the photothermal conversion efficiency decreases from 12.10 to 6.86 due to the emittance increase after annealing at 600 °C for 192 h. Meanwhile, the nitrogen atom in the Zr0.3Al0.7N sub-layer diffuses toward the adjacent sub-layer due to the spinodal decomposition of metastable c-ZrAlN and the phase transition from c-AlN to h-AlN, which leads to the composition of the Zr0.3Al0.7N sub-layer deviates the initial design. This phenomenon has a guide effect for the thermal-stability improvement of cermet coatings. Additionally, a serious diffusion between copper and silicon substrate also contributes to the emittance increase.

Tuning of the acid–base properties of primary Me{sub 2}O{sub 3} (Me = Al, Ga, In) and binary (ZrO{sub 2}–Me{sub 2}O{sub 3}) (Me = B, Al, Ga, In) oxides by adding WO{sub 3}: A calorimetric study

Energy Technology Data Exchange (ETDEWEB)

Kourieh, Reem; Bennici, Simona; Auroux, Aline, E-mail: aline.auroux@ircelyon.univ-lyon1.fr

2013-09-10

Highlights: • Preparation of WO{sub 3}/Me{sub 2}O{sub 3} and WO{sub 3}/(ZrO{sub 2}–Me{sub 2}O{sub 3}) catalysts (Me{sub 2}O{sub 3} = group III oxides). • Acid–base properties were estimated by adsorption microcalorimetry of NH{sub 3} and SO{sub 2}. • The tuning of acid–base properties of amphoteric oxides was achieved by adding WO{sub 3}. • Pyridine adsorption showed that acidity is due to the presence of Lewis acid sites. - Abstract: In this work two series of samples were prepared by impregnation of Me (Me = Al, Ga, In) hydroxides and Zr–Me (Me = B, Al, Ga, In) mixed hydroxides with an ammonium metatungstate hydrate solution followed by calcination at 400 °C. The obtained WO{sub 3}/Me{sub 2}O{sub 3} and WO{sub 3}/(ZrO{sub 2}–Me{sub 2}O{sub 3}) samples have been characterized in terms of their structural, textural, and surface properties, including the acid features, by a variety of techniques (BET, XRD, TG) and microcalorimetry. The acid–base properties were estimated by the adsorption of NH{sub 3} and SO{sub 2} as probe molecules, respectively. The prepared mixed oxide samples showed very different properties in terms of surface area and X-ray diffractograms. All obtained samples showed a specific acidic–basic character influenced by the relative amounts of each oxide, the most acidic samples being WO{sub 3}/ZrO{sub 2} and WO{sub 3}/Al{sub 2}O{sub 3} and WO{sub 3}/(Al{sub 2}O{sub 3}–ZrO{sub 2})

The effect of ZrO2 grinding media on the attrition milling of FeAl with Y2O3

International Nuclear Information System (INIS)

Gedevanishvili, S.; Deevi, S.C.

2004-01-01

Attrition milling of water and gas atomized FeAl was carried out with Y 2 O 3 , where ZrO 2 was used as a grinding media in place of stainless steel balls to avoid contamination with Cr and C. Consolidation of the milled powders produced complex FeAl phases containing Zr which doubled the hardness and significantly improved the creep resistance as compared to that of unmilled and consolidated FeAl

Amorphization of Zr3Al by hydrogenation and subsequent electron irradiation

International Nuclear Information System (INIS)

Meng, W.J.; Koike, J.; Okamoto, P.R.; Rehn, L.E.

1988-12-01

1-MeV electron irradiation of hydrogenated Zr 3 Al (Zr 3 AlH/sub 0.96/) at 10K is studied. A more than 20 fold reduction in the critical dose required for complete amorphization is observed for the hydrogenated specimen as compared to the un-hydrogenated Zr 3 Al under identical irradiation conditions. 11 refs., 4 figs

(Nbx, Zr1-x)4AlC3 MAX Phase Solid Solutions: Processing, Mechanical Properties, and Density Functional Theory Calculations.

Science.gov (United States)

Lapauw, Thomas; Tytko, Darius; Vanmeensel, Kim; Huang, Shuigen; Choi, Pyuck-Pa; Raabe, Dierk; Caspi, El'ad N; Ozeri, Offir; To Baben, Moritz; Schneider, Jochen M; Lambrinou, Konstantina; Vleugels, Jozef

2016-06-06

The solubility of zirconium (Zr) in the Nb4AlC3 host lattice was investigated by combining the experimental synthesis of (Nbx, Zr1-x)4AlC3 solid solutions with density functional theory calculations. High-purity solid solutions were prepared by reactive hot pressing of NbH0.89, ZrH2, Al, and C starting powder mixtures. The crystal structure of the produced solid solutions was determined using X-ray and neutron diffraction. The limited Zr solubility (maximum of 18.5% of the Nb content in the host lattice) in Nb4AlC3 observed experimentally is consistent with the calculated minimum in the energy of mixing. The lattice parameters and microstructure were evaluated over the entire solubility range, while the chemical composition of (Nb0.85, Zr0.15)4AlC3 was mapped using atom probe tomography. The hardness, Young's modulus, and fracture toughness at room temperature as well as the high-temperature flexural strength and E-modulus of (Nb0.85, Zr0.15)4AlC3 were investigated and compared to those of pure Nb4AlC3. Quite remarkably, an appreciable increase in fracture toughness was observed from 6.6 ± 0.1 MPa/m(1/2) for pure Nb4AlC3 to 10.1 ± 0.3 MPa/m(1/2) for the (Nb0.85, Zr0.15)4AlC3 solid solution.

Fractography of STIR casted Al-ZrO2 composites

International Nuclear Information System (INIS)

Baghchesara, M. A.; Abdizadeh, H.; Baharvandi, H. R.

2009-01-01

In this study, Al-ZrO 2 composites were produced by Vortex method using ZrO 2 powder with 1 micron average diameter as reinforce particles and Al-356 as the matrix metal. The melt composites were stirred for 13 minutes, then casted into a metallic mold. Different samples of 5, 10 and 15 volume percent of ZrO 2 , in different casting temperatures of 750, 850 and 950 d eg C were produced. The latter 2 casting temperatures are not a common practice but were chosen to enhance fluidity. Effects of volume percent of ZrO 2 particles and casting temperature on tensile strength, microstructure, and fracture surfaces of Al-ZrO 2 composites have been investigated. The highest tensile strength was achieved in the specimen containing 15 vol. % ZrO 2 produced at 750 d eg C which shows an increase of 60% in comparison to the Al-356 non-reinforced alloy. Microscopic investigations of fracture surfaces revealed that fracture in a brittle manner with little or no necking happening. By increasing ZrO 2 content and casting temperature, the composites fracture goes in a more severely brittle manner.

A high performance transparent resistive switching memory made from ZrO_2/AlON bilayer structure

International Nuclear Information System (INIS)

Tsai, Tsung-Ling; Chang, Hsiang-Yu; Tseng, Tseung-Yuen; Lou, Jesse Jen-Chung

2016-01-01

In this study, the switching properties of an indium tin oxide (ITO)/zirconium oxide (ZrO_2)/ITO single layer device and those of a device with an aluminum oxynitride (AlON) layer were investigated. The devices with highly transparent characteristics were fabricated. Compared with the ITO/ZrO_2/ITO single layer device, the ITO/ZrO_2/AlON/ITO bilayer device exhibited a larger ON/OFF ratio, higher endurance performance, and superior retention properties by using a simple two-step forming process. These substantial improvements in the resistive switching properties were attributed to the minimized influence of oxygen migration through the ITO top electrode (TE), which can be realized by forming an asymmetrical conductive filament with the weakest part at the ZrO_2/AlON interface. Therefore, in the ITO/ZrO_2/AlON/ITO bilayer device, the regions where conductive filament formation and rupture occur can be effectively moved from the TE interface to the interior of the device.

Phase equilibria of the Al-Pr-Zr ternary system at 773 K

International Nuclear Information System (INIS)

She, Jia; Zhan, Yongzhong; Li, Chunliu; Du, Yong; Xu, Honghui; He, Yuehui

2010-01-01

The phase equilibria of the Al-Pr-Zr ternary system at 773 K have been investigated mainly by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA). The 14 binary compounds, i.e. AlZr 3 , AlZr 2 , Al 2 Zr 3 , Al 3 Zr 4 , AlZr, Al 3 Zr 2 , Al 2 Zr, Al 3 Zr, α-Al 11 Pr 3 , Al 3 Pr, Al 2 Pr, β-AlPr, AlPr 2 and β-AlPr 3 were confirmed. No binary compound was found in the Pr-Zr binary system. The result shows that the isothermal section of the Al-Pr-Zr ternary system at 773 K consists of 17 single-phase regions, 31 two-phase regions and 15 three-phase regions. All the intermediate compounds phases in this system have not a remarkable solid solution at 773 K. No ternary compound is found in this work.

The first-principles calculations for the elastic properties of Zr2Al under compression

International Nuclear Information System (INIS)

Yuan Xiaoli; Wei Dongqing; Chen Xiangrong; Zhang Qingming; Gong Zizheng

2011-01-01

Graphical abstract: The calculated elastic constants C ij as a function of pressure P. Display Omitted Research highlights: → It is found that the five independent elastic constants increase monotonically with pressure. C 11 and C 33 vary rapidly as pressure increases, C 13 and C 12 becomes moderate. However, C 44 increases comparatively slowly with pressure. Figure shows excellent satisfaction of the calculated elastic constants of Zr 2 Al to these equations and hence in our calculation, the Zr 2 Al is mechanically stable at pressure up to 100 GPa. - Abstract: The first-principles calculations were applied to investigate the structural, elastic constants of Zr 2 Al alloy with increasing pressure. These properties are based on the plane wave pseudopotential density functional theory (DFT) method within the generalized gradient approximation (GGA) for exchange and correlation. The result of the heat of formation of Zr 2 Al crystal investigated is in excellent consistent with results from other study. The anisotropy, the shear modulus, and Young's modulus for the ideal polycrystalline Zr 2 Al are also studied. It is found that (higher) pressure can significantly improve the ductility of Zr 2 Al. Moreover, the elastic constants of Zr 2 Al increase monotonically and the anisotropies decrease with the increasing pressure. Finally, it is observed that Zr d electrons are mainly contributed to the density of states at the Fermi level.

Effect of Nb aggregates on Zr2Fe

International Nuclear Information System (INIS)

Ramos, Cinthia P.

2001-01-01

The binary Zr-Fe phase diagram revision, performed by Arias et al., accepted the intermetallic Zr 2 Fe crystalline structure as tetragonal and determined that the presence of a third element like oxygen, nitrogen or carbon, stabilizes a cubic phase. Nevitt et al. studying Ti, Zr and Hf alloys with transition metals as second or third element and ternary systems with oxygen as third element, systematized the occurrence of phases with a cubic Ti 2 Ni type crystalline structure. From previous studies in the Zr-Nb-Fe system, it is an agreed fact that Nb presence in the Zr 2 Fe intermetallic stabilizes a cubic Ti 2 Ni type phase. The purpose of the present work is to determine the stability range of the Zr 2 Fe intermetallic with Nb contents, the existence range of the ternary cubic Ti 2 Ni type phase (designated Λ) and the corresponding two-phase region. We analyze as cast and heat treated (800 C degrees) Zr-Nb-Fe alloys with 35 atomic % Fe and Nb contents between 0.5 and 15 atomic %. The determination and characterization of the phases is made by optical and scanning electron microscopy, X-ray diffraction microprobe analysis and Moessbauer Spectroscopy. Joining these techniques together it is found, among many other things, that the Zr 2 Fe phase would accept up to around 0.5 atomic % Nb in solution and that the two-phase region Zr 2 Fe+Λ would be stable in the (0.5 - 3.5) Nb atomic % range. It is proposed as well a 800 C degrees section of the ternary (Zr-Nb-Fe) in the studied region. (author) [es

Tuning of magnetic properties and structure of granular FeCoZr-Al{sub 2}O{sub 3} nanocomposites by oxygen incorporation

Energy Technology Data Exchange (ETDEWEB)

Saad, A. [Al-Balqa Applied University, Applied Science Department, Salt (Jordan); Fedotova, J. [NC PHEP Belarusian State University, 153 M.Bogdanovich str., 220040 Minsk (Belarus)], E-mail: Julia@hep.by; Nechaj, J. [NC PHEP Belarusian State University, 153 M.Bogdanovich str., 220040 Minsk (Belarus); Szilagyi, E. [KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, P.O. Box 49 (Hungary); Marszalek, M. [Niewodniczanski Institute of Nuclear Physics PAN, 31-342 Cracow (Poland)

2009-03-05

Effect of oxygen incorporation on the magnetic properties and structure of (FeCoZr){sub x}(Al{sub 2}O{sub 3}){sub 1-x} (17% < x < 65%) nanocomposites sputtered in pure Ar and mixed Ar + O ambient was investigated using Backscattering spectrometry, SQUID-magnetometry, atomic force microscopy/magnetic force microscopy (AFM/MFM) and Moessbauer spectroscopy. The basic differences in the magnetic state of both series were extracted by comparing their coercivity fields, magnetization, MFM magnetic contrast and discussed with regard to the formation of complex FeCo-oxides.

Strength-toughness relations in sintered and isostatically hot-pressed ZrO2-toughened Al2O3

International Nuclear Information System (INIS)

Hori, S.; Yoshimura, M.; Somiya, S.

1986-01-01

The fracture toughness of fine-grained undoped ZrO 2 -toughened Al 2 O 3 (ZTA) was essentially unchanged by post-sintering hot isostatic pressing and increased monotonically with ZrO 2 additions up to 25 wt%. The strength of ZTA with 5 to 15 wt% tetragonal ZrO 2 , which depended monotonically on the amount of ZrO 2 present before hot isostatic pressing, was increased by pressing but became almost constant between 5 and 15 wt% ZrO 2 addition. The strength appeared to be controlled by pores before pressing and by surface flaws after pressing; the size of flaws after pressing increased with ZrO 2 content. The strength of ZTA containing mostly monoclinic ZrO 2 (20 to 25 wt%) remained almost constant despite the noticeable density increase upon hot isostatic pressing because the strength was controlled by preexisting microcracks whose extent did not change on postsintering pressing. These strength-toughness relations in sintered and isostatically hot-pressed ZTA are explained on the basis of R-curve behavior. The importance of the contribution of microcracks to the toughness of ZTA is emphasized

Study of directionally solidified eutectic Al2O3-ZrO2(3%Y2O3 doped with TiO2

Directory of Open Access Journals (Sweden)

Peña, J. I.

2007-06-01

Full Text Available An study of directionally grown samples of the eutectic composition in the Al2O3-ZrO2 (3 mol% Y2O3 system, with small TiO2 additions (1 wt%, is presented. The microstructural changes induced by this addition are analysed using SEM (EDX techniques. The mechanical changes, when TiO2 is added, are studied by measuring the flexural strength by three point bending. Also, the toughness is determined by Vickers indentation method. When slow growth rates (10 mm/h are used, interpenetratred and homogeneous microstructure is obtained, independently of the TiO2 doping. When growth rates are higher (300 and 1000 mm/h the structure changes and the phases are organized in form of colonies or cells, which have smaller size when TiO2 is present. This size reduction is accompanied with an increase of the toughness.Este trabajo presenta un estudio de muestras crecidas direccionalmente del sistema Al2O3-ZrO2 (3 mol% Y2O3 en su composición eutéctica con pequeñas adiciones de óxido de titanio (1% de TiO2 en peso. Se analizan los cambios microestructurales inducidos por esta adición mediante SEM (EDX y se estudian los cambios en su comportamiento mecánico medido por flexión en tres puntos, así como la tenacidad de fractura mediante indentación Vickers. Con velocidades lentas de solidificación (10 mm/h se obtiene en ambos casos una microestructura homogénea e interpenetrada, mientras que a velocidades mayores, 300 y 1000 mm/h, se forma una estructura en las que las fases se organizan en forma de colonias o células, siendo éstas de menor tamaño en las muestras dopadas. Esta disminución en el tamaño viene acompañada de un aumento de la tenacidad de fractura medida por indentación.

Structure-property relationships of mullite-SiC-Al{sub 2}O{sub 3}–ZrO{sub 2} composites developed during carbothermal reduction of aluminosilicate minerals

Energy Technology Data Exchange (ETDEWEB)

Seifollahzadeh, P., E-mail: Pseifollahzadeh.mat@stu.yazd.ac.ir; Kalantar, M.; Ghasemi, S.S.

2015-10-25

Evolution of SiC and ZrO{sub 2} in the matrix of Al{sub 2}O{sub 3} or mullite have been reported to enhance a higher toughness, good thermal shock resistance (lowering thermal expansion and improving thermal conductivity) and improved creep resistance of composite materials. In this study, the structure-property relationships of mullite-Al{sub 2}O{sub 3} matrix composites have been investigated in conjunction with the evolution of reinforcing phases such as SiC–ZrO{sub 2} by an economical heat treatment process called carbothermal reduction of inorganic minerals (Kaolinite, Andalusite, Zircon). The influence of starting materials in relation with the variation in molar ratio of C/SiO{sub 2} on the phase composition, microstructures, physical and mechanical properties have been studied. Light microscopy has been supplemented with scanning electron microscopy, XRD analysis, differential thermal and thermal gravity analysis to follow the structure-property relationships. The experimental results show that with increasing of C/SiO{sub 2} ratio in starting materials, very fine SiC whiskers have been formed in the microstructures. Moreover, the densification and strength are considerable higher for ZrO{sub 2} + SiC containing composites in comparison to that of only SiC added ones. Furthermore, it has been found that the appropriate ratio of C/SiO{sub 2} with the associated firing temperature to develop a higher densification and SiC crystallization have been related to the 3.5, 1550 °C for kaolinite, 3.5, 1450 °C for zircon and 5.5, 1600 °C for andalusite containing composite samples, respectively. - Highlights: • In-situ formation of SiC whiskers in matrix of alumina + mullite composites. • Advantage of availability, abundance and economical for starting materials. • Lack of environmental problems in comparable of utilization of whiskers directly. • A mixture of coke and alumina as a protective layer instead of inert atmosphere. • Fabrication of advanced

Development of the Ni/Al{sub 2}O{sub 3}/ZrO{sub 2} catalyst to steam reforming of the natural gas process; Desenvolvimento do catalisador Ni/Al2O3/ZrO2 para o processo de reforma do gas natural

Energy Technology Data Exchange (ETDEWEB)

Neiva, Laedna Souto; Ramalho, Melanea A.F.; Costa, Ana Cristina Figueiredo de Melo; Gama, Lucianna [Universidade Federal de Campina Grande (UFCG), PB (Brazil); Andrade, Heloysa M.C. [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil); Kiminami, Ruth Herta G.A. [Universidade Federal de Sao Carlos (UFSCAR), SP (Brazil)

2008-07-01

The aim of this work is to develop catalyst of the type Ni/{alpha}-Al{sub 2}O{sub 3} modified with 0.005 mol of ZrO{sub 2} and structural, morphologic and catalytic characterizations, aiming employ in the reforming process of the natural gas. The catalytic supports were obtained by synthesis method for combustion reaction according to the concepts of the propellants chemistry. The active species of the catalyst (nickel) was deposited over the support by humid impregnation method. The catalytic supports were characterized by XRD, morphologic analysis by SEM and TEM, textural analysis by BET method before and after of the impregnation with nickel and were done catalytic tests in laboratory. The catalytic supports shows structure without any secondary phase with crystallinity elevated degree and crystal size varying between 5.7 and 7.0 nm. The catalytic test shows that these catalysts promoted a conversion percentile considerable of the natural gas in syngas. (author)

Phase equilibria of the Al-Pr-Zr ternary system at 773 K

Energy Technology Data Exchange (ETDEWEB)

She, Jia [Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004 (China); Zhan, Yongzhong, E-mail: zyzmatres@yahoo.com.c [Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004 (China); Li, Chunliu [Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004 (China); Du, Yong; Xu, Honghui; He, Yuehui [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China)

2010-07-30

The phase equilibria of the Al-Pr-Zr ternary system at 773 K have been investigated mainly by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA). The 14 binary compounds, i.e. AlZr{sub 3}, AlZr{sub 2}, Al{sub 2}Zr{sub 3}, Al{sub 3}Zr{sub 4}, AlZr, Al{sub 3}Zr{sub 2}, Al{sub 2}Zr, Al{sub 3}Zr, {alpha}-Al{sub 11}Pr{sub 3}, Al{sub 3}Pr, Al{sub 2}Pr, {beta}-AlPr, AlPr{sub 2} and {beta}-AlPr{sub 3} were confirmed. No binary compound was found in the Pr-Zr binary system. The result shows that the isothermal section of the Al-Pr-Zr ternary system at 773 K consists of 17 single-phase regions, 31 two-phase regions and 15 three-phase regions. All the intermediate compounds phases in this system have not a remarkable solid solution at 773 K. No ternary compound is found in this work.

In situ formation of CA6 platelets in Al2O3 and Al2O3/ZrO2 matrices

International Nuclear Information System (INIS)

Belmonte, M.; Sanchez-Herencia, A.J.; Moreno, R.; Miranzo, P.; Moya, J.S.; Tomsia, A.P.

1993-01-01

Al 2 O 3 and Al 2 O 3 /ZrO 2 compacts containing CaO as a dopant have been sintered under different conditions and atmospheres: air, high vacuum (> 10 -6 torr). SEM observations have been made on the polished surfaces of sintered and also of annealed samples. Only after the annealing treatment in air at temperatures ranging from 1400 to 1500 C, a massive formation of CA 6 platelets was detected in samples sintered in low oxygen partial pressure atmospheres. In order to clarify the mechanism of formation of this secondary phase at the grain boundaries, CaO has been introduced in the form of either plaster of Paris (to reproduce a possible contamination provided by the molds in slip casting) or CaCO 3 . The obtained results indicate the important role of the firing atmosphere on the precipitation of secondary phases at grain boundary. (orig.)

Physical properties of core-concrete systems: Al{sub 2}O{sub 3}-ZrO{sub 2} molten materials measured by aerodynamic levitation

Energy Technology Data Exchange (ETDEWEB)

Ohishi, Yuji, E-mail: ohishi@see.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University (Japan); Kargl, F. [Institute of Materials Physics in Space, German Aerospace Center (Germany); Nakamori, F.; Muta, Hiroaki; Kurosaki, Ken [Graduate School of Engineering, Osaka University (Japan); Yamanaka, Shinsuke [Graduate School of Engineering, Osaka University (Japan); Research Institute of Nuclear Engineering, University of Fukui (Japan)

2017-04-15

During a molten core–concrete interaction, molten oxides consisting of molten core materials (UO{sub 2} and ZrO{sub 2}) and concrete (Al{sub 2}O{sub 3}, SiO{sub 2}, CaO) are formed. Reliable data on the physical properties of the molten oxides will allow us to accurately predict the progression of a nuclear reactor core meltdown accident. In this study, the viscosities and densities of molten (ZrO{sub 2}){sub x}(Al{sub 2}O{sub 3}){sub 1-x} (x = 0.356 and 0.172) were measured using an aerodynamic levitation technique. The densities of two small samples were estimated from their masses and their volumes (calculated from recorded images of the molten samples). The droplets were forced to oscillate using speakers, and their viscosities were evaluated from the damping behaviors of their oscillations. The results showed that the viscosity of molten (ZrO{sub 2}){sub x}(Al{sub 2}O{sub 3}){sub 1-x} compared to that of pure molten Al{sub 2}O{sub 3} is 25% lower for x = 0.172, while it is unexpectedly 20% higher for x = 0.356. - Highlights: •The physical properties of molten (ZrO{sub 2}){sub x}(Al{sub 2}O{sub 3}){sub 1-x} (x = 0.356 and 0.172) have been evaluated. •The measurement was conducted using an aerodynamic levitation technique. •The density and viscosity were measured.

Potentiodynamic polarization studies of bulk amorphous alloy Zr57Cu15.4Ni12.6Al10Nb5 and Zr59Cu20Ni8Al10Ti3 in aqueous HNO3 media

International Nuclear Information System (INIS)

Sharma, Poonam; Dhawan, Anil; Jayraj, J.; Kamachi Mudali, U.

2013-01-01

The potentiodynamic polarization studies were carried out on Zr based bulk amorphous alloy Zr 57 Cu 15.4 Ni 12.6 Al 10 Nb 5 and Zr 59 Cu 20 Ni 8 Al 10 Ti 3 in solutions of 1 M, 6 M and 11.5 M HNO 3 aqueous media at room temperature. As received specimens of Zr 57 Cu 15.4 Ni 12.6 Al 10 Nb 5 (5 mm diameter rod) and Zr 59 Cu 20 Ni 8 Al 10 Ti 3 (3 mm diameter rod) were polished with SiC paper before testing them for potentiodynamic polarization studies. The amorphous nature of the specimens was checked by X-ray diffraction. The bulk amorphous alloy Zr 59 Cu 20 Ni 8 Al 10 Ti 3 shows the better corrosion resistance than Zr 57 Cu 15.4 Ni 12.6 Al 10 Nb 5 alloy in the aqueous HNO 3 media as the value of the corrosion current density (I corr ) for Zr 57 Cu 15.4 Ni 12.6 Al 10 Nb 5 alloy were found to be more than Zr 59 Cu 20 Ni 8 Al 10 Ti 3 alloy in aqueous HNO 3 media. The improved corrosion resistance of Zr 59 Cu 20 Ni 8 Al 10 Ti 3 alloy is possibly due to the presence of Ti and formation of TiO 2 during anodic oxidation. Both Zr based bulk amorphous alloys shows wider passive range at lower concentration of nitric acid and the passive region gets narrowed down with the increase in concentration. A comparison of data obtained from both the Zr-based bulk amorphous alloys is made and results are discussed in the paper. (author)

Highly active sulfided CoMo catalysts supported on (ZrO{sub 2}–TiO{sub 2})/Al{sub 2}O{sub 3} ternary oxides

Energy Technology Data Exchange (ETDEWEB)

Escobar, José, E-mail: jeaguila@imp.mx [Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, Col. San Bartolo Atepehuacan, Gustavo A. Madero, México, D.F. 07730 (Mexico); De Los Reyes, José A., E-mail: jarh@xanum.uam.mx [Area de Ing. Química, UAM – Iztapalapa, San Rafael Atlixco 186, Col. Vicentina, Iztapalapa, México, D.F. 09340 (Mexico); Ulín, Carlos A. [Area de Ing. Química, UAM – Iztapalapa, San Rafael Atlixco 186, Col. Vicentina, Iztapalapa, México, D.F. 09340 (Mexico); Barrera, María C., E-mail: mcbdgavilan@gmail.com [Facultad de Ciencias Químicas, Universidad Veracruzana, Av. Universidad km. 7.5, Col. Santa Isabel, Coatzacoalcos, Veracruz, México, D.F. 96538 (Mexico)

2013-12-16

(ZrO{sub 2}–TiO{sub 2})/Al{sub 2}O{sub 3} ternary oxide at 20 mol% Al{sub 2}O{sub 3} (80% ZrO{sub 2}–TiO{sub 2}, in turn at 40–60 mol ratio) prepared by controlled co-precipitation (by urea thermal decomposition) of zirconium (ZrOCl{sub 2}·8H{sub 2}O) and titanium (TiCl{sub 4}) chlorides over a ground alumina substrate constitutes a promising material to be used as carrier of sulfided hydrodesulfurization (HDS) catalysts. After calcining (at 500 °C), the ternary oxide presented textural properties (S{sub g} = 387 m{sup 2} g{sup −1}, V{sub p} = 0.74 ml g{sup −1}, mean pore diameter = 7.6 nm) suitable to its utilization as carrier of catalysts applied in the oil-derived middle distillates HDS. As determined by temperature programmed-reduction and Raman and UV–vis spectroscopies ZrO{sub 2}–TiO{sub 2} deposition over alumina substrate resulted in decreased proportion of Mo{sup 6+} species in tetrahedral coordination on the oxidic impregnated material. As those species constitute hardly reducible precursors, their diminished concentration could be reflected in enhanced amount of Mo species susceptible of activation by sulfiding (H{sub 2}S/H{sub 2} at 400 °C) over our ternary carrier. Limiting the concentration of zirconia-titania (at 40–60 mol ratio) to 20 mol% in the mixed oxides support allowed the preparation of highly active promoted (by cobalt, at Co/(Co + Mo) = 0.3) MoS{sub 2} phase (at 2.8 atoms/nm{sup 2}), that formulation showing excellent properties in hydrodesulfurization (HDS) of both dibenzothiophene and highly-refractory 4,6-dimethyl-dibenzothiophene. Due to alike yields to various HDS products over CoMo/(ZrO{sub 2}–TiO{sub 2})/Al{sub 2}O{sub 3} and the corresponding Al{sub 2}O{sub 3}-supported formulation, presence of similar actives sites over those catalysts was strongly suggested. It seemed that enhanced concentration of octahedral Mo{sup 6+} over the oxidic impregnated precursor with (ZrO{sub 2}–TiO{sub 2})/Al{sub 2}O{sub 3

Resistive switching in ZrO2 based metal-oxide-metal structures

International Nuclear Information System (INIS)

Kaerkkaenen, Irina

2014-01-01

The goal of this work is a deeper understanding of the influence of the (i) metal-oxide-metal (MOM) layer stacks configuration, (ii) the oxide films microstructure, (iii) and their defect structure on the appearance of different switching modes, i.e. unipolar (UP) and bipolar (BP). The first part deals with the fabrication of ZrO 2 thin films by an industrial compatible atomic layer deposition (ALD) process, the chemical, structural and morphological characterization of the films, the growth of ZrO 2 /TiO 2 bilayers, the integration of the layers into metal-oxide-metal (MOM) devices and the electrical characterization with focus on the RS behavior. In the second part the effect of the device structure, in particular the thickness of the electrochemical active electrode (EAE) and the ZrO 2 film morphology, on the RS switching polarity of Pt/ZrO 2 /(EAE) cells is discussed. ZrO 2 films and ZrO 2 /TiO 2 bilayers were grown by ALD and were carefully structurally and electrically characterized. The ZrO 2 films grown from Zr[N(CH 3 )C 2 H 5 ] 4 (TEMA-Zr) at 240 C were polycrystalline with a mixture of cubic/tetragonal phases. ALD/H 2 O-ZrO 2 films exhibited a random oriented polycrystalline structure, whereas the ALD/O 3 -ZrO 2 films consisted of preferably oriented cubic shaped grains. Pt/ZrO 2 /Ti/Pt structures with a Ti top electrode (TE) thickness of 5 to 20 nm showed unipolar type RS behavior, while by increasing the Ti TE thickness a gradual change of switching polarity from unipolar to bipolar with a completely bipolar type RS behavior for a Ti TE thickness of 40 nm is found. The switching in Pt/ZrO 2 /TiO 2 /Ti/Pt devices was unipolar, comparable to Pt/ZrO 2 /Ti/Pt cells. In contrast, bilayers with the reverse structure, Pt/TiO 2 /ZrO 2 /Ti/Pt, showed non-switching behavior. The effect of the cells stack structure on the polarity of the RS behavior was studied in detail for 20 nm thick ZrO 2 films grown by an ozone based ALD process and integrated into Pt/ZrO 2

Interfacial phenomena in the reactions of Al-B, Al-Ti-B, and Al-Zr-B alloys with KF-AlF3 and NaF-AlF3 melts

International Nuclear Information System (INIS)

Lee, M.S.; Terry, B.S.; Grieveson, P.

1993-01-01

The interfacial phenomena occurring during the contacting of liquid Al-B, Al-Ti-B, and Al-Zr-B melts with KF-AlF 3 liquid fluxes have been investigated by optical examination of quenched metal drops previously immersed in the liquid fluxes. Reactions in the Al-B/KF-AlF 3 system involve the formation of metastable AlB 12 at the metal/flux interface. At high KBF 4 levels in the flux, the AlB 12 is dispersed in the flux and also at low KBF 4 levels in the metal. Reactions in the Al-Ti-B/KF-AlF 3 system involve the formation of TiB 2 , which may be dispersed in either the metal or the flux depending upon the composition of the flux. The results obtained for the Al-Ti-B/NaF-AlF 3 and Al-Zr-B/KF-AlF 3 systems were similar to those observed for the Al-Ti-B/KF-AlF 3 system

Al2TiO5-ZrTiO4-ZrO2 composites

International Nuclear Information System (INIS)

Parker, F.J.

1990-01-01

The characterization and properties of ceramic composites containing the phases Al 2 TiO 5 , ZrTiO 4 , and ZrO 2 are described. The low thermal expansions are apparently due to a combination of microcracking by the titanate phases and a contractive phase transformation by the ZrO 2 . The crystal chemistry and microstructure of the product are processing dependent. Although the composites represent a complex microcracking system, the low thermal expansions and high-temperature stability make them potential candidates for commercial application requiring thermal shock resistance

Development of AL_2O_3 - ZrO_2 ceramic composite reinforced with rare earth oxides (Y_2O)3) for inert coating of storage and transport systems of crude petroleum

International Nuclear Information System (INIS)

Silva, J.C.; Yadava, Y.P.; Sanguinetti Ferreira, R.A.; Albuquerque, L.T.

2014-01-01

The advancement of the oil sector has generated the need for the use of materials resistant to aggressive environments to oil. Although ceramics have high melting point and high hardness is, on the other hand, more fragile and less tough, which can cause damage to the metal structure. The Al_2O_3 based ceramics reinforced with rare earth oxide can improve tenaciousness and makes the ceramic material more resistant. This article aims to present the production of composite Al_2O_3 - Y_2O_3 stabilized ZrO_2 by uniaxial pressing, following sintering (1200-1350 deg C). Structural and microstructural characterizations as XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscopy) and mechanical tests as Vickers hardness, % absorption and % linear shrinkage were conducted to evaluate the feasibility of using the composite and ceramic coating for storage and transportation of oil tanks. The results indicate that the proportions of 5%, 10% and 30% ZrO_2 make it suitable as a good composite suitable coating. (author)

Structure and properties of Al-Mg-Li-Zr system alloys

International Nuclear Information System (INIS)

Fridlyander, I.N.; Dolzhanskij, Yu.M.; Sandler, V.S.; Tyurin, .V.; Nikol'skaya, T.I.

1977-01-01

Studied were the structure and mechanical properties of the Al-Mg-Li-Zr alloy system (including 01420 alloy) containing 1.6-5.3%Li and 1.0-8.8%Mg). Electron microscopic studies of 01420 alloy conducted after heating at 450 deg C for 4 hours revealed non-uniformly distributed precipitations of a metastable phase ZrAl 3 , having spherical and needle-like configurations. These precipitations, together with zirconium contained in the solid solution, retard recrystallization. The introduction of 0.1-0.2% Zr decreases the limiting solubility of magnesium and lithium in the aluminium solid solution and leads to the formation of disperse equilibrium (S and, possibly, γ) phases with the size of 0.1-0.5 mcm. These phases were observed in the alloys containing (>=) 4% Mg and 1.9-3.5% Li. The method of planned experiment was used to study the principles governing the variation of the mechanical properties of the alloys subjected to water hardening and after aging at 170 deg C for 16 hours. It was established that the strength properties of the hardened alloys become higher, and the relative elongation decreases with the content of lithium and especially magnesium. It would be more proper to assess strengthening in the course of aging according to variation in the yield point and hardness. The effect of aging determined by the yield point depends on the content of lithium and is practically independent of the concentration of magnesium

Precipitation in cold-rolled Al-Sc-Zr and Al-Mn-Sc-Zr alloys prepared by powder metallurgy

KAUST Repository

Vlach, Martin

2013-12-01

The effects of cold-rolling on thermal, mechanical and electrical properties, microstructure and recrystallization behaviour of the AlScZr and AlMnScZr alloys prepared by powder metallurgy were studied. The powder was produced by atomising in argon with 1% oxygen and then consolidated by hot extrusion at 350 C. The electrical resistometry and microhardness together with differential scanning calorimetry measurements were compared with microstructure development observed by transmission and scanning electron microscopy, X-ray diffraction and electron backscatter diffraction. Fine (sub)grain structure developed and fine coherent Al3Sc and/or Al3(Sc,Zr) particles precipitated during extrusion at 350 C in the alloys studied. Additional precipitation of the Al3Sc and/or Al3(Sc,Zr) particles and/or their coarsening was slightly facilitated by the previous cold rolling. The presence of Sc,Zr-containing particles has a significant antirecrystallization effect that prevents recrystallization at temperatures minimally up to 420 C. The precipitation of the Al6Mn- and/or Al 6(Mn,Fe) particles of a size ~ 1.0 μm at subgrain boundaries has also an essential antirecrystallization effect and totally suppresses recrystallization during 32 h long annealing at 550 C. The texture development of the alloys seems to be affected by high solid solution strengthening by Mn. The precipitation of the Mn-containing alloy is highly enhanced by a cold rolling. The apparent activation energy of the Al3Sc particles formation and/or coarsening and that of the Al6Mn and/or Al 6(Mn,Fe) particle precipitation in the powder and in the compacted alloys were determined. The cold deformation has no effect on the apparent activation energy values of the Al3Sc-phase and the Al 6Mn-phase precipitation. © 2013 Elsevier Inc.

Precipitation in cold-rolled Al-Sc-Zr and Al-Mn-Sc-Zr alloys prepared by powder metallurgy

KAUST Repository

Vlach, Martin; Stulí ková , Ivana; Smola, Bohumil; Kekule, Tomá š; Kudrnová , Hana; Daniš, Stanislav; Gemma, Ryota; Očená šek, Vladivoj; Má lek, Jaroslav; Tanprayoon, Dhritti; Neubert, Volkmar

2013-01-01

The effects of cold-rolling on thermal, mechanical and electrical properties, microstructure and recrystallization behaviour of the AlScZr and AlMnScZr alloys prepared by powder metallurgy were studied. The powder was produced by atomising in argon with 1% oxygen and then consolidated by hot extrusion at 350 C. The electrical resistometry and microhardness together with differential scanning calorimetry measurements were compared with microstructure development observed by transmission and scanning electron microscopy, X-ray diffraction and electron backscatter diffraction. Fine (sub)grain structure developed and fine coherent Al3Sc and/or Al3(Sc,Zr) particles precipitated during extrusion at 350 C in the alloys studied. Additional precipitation of the Al3Sc and/or Al3(Sc,Zr) particles and/or their coarsening was slightly facilitated by the previous cold rolling. The presence of Sc,Zr-containing particles has a significant antirecrystallization effect that prevents recrystallization at temperatures minimally up to 420 C. The precipitation of the Al6Mn- and/or Al 6(Mn,Fe) particles of a size ~ 1.0 μm at subgrain boundaries has also an essential antirecrystallization effect and totally suppresses recrystallization during 32 h long annealing at 550 C. The texture development of the alloys seems to be affected by high solid solution strengthening by Mn. The precipitation of the Mn-containing alloy is highly enhanced by a cold rolling. The apparent activation energy of the Al3Sc particles formation and/or coarsening and that of the Al6Mn and/or Al 6(Mn,Fe) particle precipitation in the powder and in the compacted alloys were determined. The cold deformation has no effect on the apparent activation energy values of the Al3Sc-phase and the Al 6Mn-phase precipitation. © 2013 Elsevier Inc.

A high performance transparent resistive switching memory made from ZrO{sub 2}/AlON bilayer structure

Energy Technology Data Exchange (ETDEWEB)

Tsai, Tsung-Ling; Chang, Hsiang-Yu; Tseng, Tseung-Yuen, E-mail: tseng@cc.nctu.edu.tw [Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Lou, Jesse Jen-Chung [Department of Energy Information Engineering, School of Software and Microelectronics, Peking University, Wuxi 214125 (China)

2016-04-11

In this study, the switching properties of an indium tin oxide (ITO)/zirconium oxide (ZrO{sub 2})/ITO single layer device and those of a device with an aluminum oxynitride (AlON) layer were investigated. The devices with highly transparent characteristics were fabricated. Compared with the ITO/ZrO{sub 2}/ITO single layer device, the ITO/ZrO{sub 2}/AlON/ITO bilayer device exhibited a larger ON/OFF ratio, higher endurance performance, and superior retention properties by using a simple two-step forming process. These substantial improvements in the resistive switching properties were attributed to the minimized influence of oxygen migration through the ITO top electrode (TE), which can be realized by forming an asymmetrical conductive filament with the weakest part at the ZrO{sub 2}/AlON interface. Therefore, in the ITO/ZrO{sub 2}/AlON/ITO bilayer device, the regions where conductive filament formation and rupture occur can be effectively moved from the TE interface to the interior of the device.

Structural and magnetic properties of UCo1/3T2/3Al solid solutions (T = Ru, Pt, Rh)

International Nuclear Information System (INIS)

Andreev, A. V.; Bordallo, H. N.; Chang, S.; Nakotte, H.; Schultz, A. J.; Sechovsky, V.; Torikachvili, M. S.

1999-01-01

We report on neutron diffraction studies of UCo 1/3 T 2/3 Al (T = Ru, Pt, Rh). All three solid solutions form in the hexagonal ZrNiAl structure. The Ru-containing compound is found to be chemically ordered, while the Pt-containing compound is nearly disordered and the Rh-containing compound is purely disordered. All three compounds exhibit long-range magnetic order with rather small U moments

Can reduced size of metals induce hydrogen absorption: ZrAl2 case

International Nuclear Information System (INIS)

Jacob, I.; Deledda, S.; Bereznitsky, M.; Yeheskel, O.; Filipek, S.M.; Mogilyanski, D.; Kimmel, G.; Hauback, B.C.

2011-01-01

Research highlights: → 15 nm particles of ZrAl 2 and Zr(Al 0.5 Co 0.5 ) 2 are obtained by attrition and cryomilling. → ZrAl 2 nanoparticles remain inert to hydrogen absorption up to pressure of ∼2 GPa. → Zr(Al 0.5 Co 0.5 ) 2 nanoparticles exhibit reduced hydrogen absorption as compared to the corresponding bulk compounds. - Abstract: The hydrogen absorption ability of the non-absorbing Al-rich ZrAl 2 compound was examined after reducing its particles-size to the nanometer regime. The hydrogen abstinence of bulk ZrAl 2 has been previously related to its excessive elastic shear stiffening. The particle size of ZrAl 2 was reduced by attrition milling and cryomilling. The minimal average particle size was estimated from powder X-ray diffraction analysis to be in the range of 10-20 nm. The hydrogen absorption of the milled compounds was measured in different hydrogenation systems at hydrogen pressures between ∼6 MPa and ∼2 GPa. In all the cases the hydrogen absorption was negligible. In addition, there was a reduction of the hydrogen absorption capacity of nanosized Zr(Al 0.5 Co 0.5 ) 2 as compared to the corresponding bulk compound at the same conditions. We suggest, in view of our and other results, that no significant improvement of the thermodynamics (unlike the kinetics) of the hydrogen absorption can be achieved via the nanoparticle avenue.

Spark plasma sintering and mechanical properties of $ZrO_{2} (Y_{2}O_{3})-Al_{2}O_{3}$ composites

CERN Document Server

Jin Sheng H; Dalla Torre, S; Miyamoto, H; Miyamoto, K

2000-01-01

Spark plasma sintering (SPS) was conducted on nanocrystalline ZrO/sub 2/(Y/sub 2/O/sub 3/)-20 mol% Al/sub 2/O/sub 3/ powder at a heat rate of 600 degrees C/min with a short holding time. Full density was obtained at sintering temperatures >1300 degrees C. Considerable grain growth occurred relative to the initial powder particles, but smaller grain size and higher density can be obtained as compared to hot-pressing. High flexural strength and fracture toughness were also achieved for the SPS-resulted composite. (8 refs).

Internal Friction of Li7La3Zr2O12 Based Lithium Ionic Conductors

Directory of Open Access Journals (Sweden)

Wang X.P.

2016-03-01

Full Text Available The diffusion mechanisms of lithium ions in tetragonal phase as well as in Al and Nb stabilized cubic Li7La3Zr2O12 compounds were investigated by low-frequency internal friction technique. In the cubic Li7La3Zr2O12 phase, a remarkable relaxation-type internal friction peak PC with a peak height up to 0.12 was observed in the temperature range from 15°C to 60°C. In the tetragonal phase however, the height of the PT peak dropped to 0.01. The obvious difference of the relaxation strength between the cubic and tetragonal phases is due to the different distribution of lithium ions in lattice, ordered in the tetragonal phase and disordered in the cubic phase. Based on the crystalline structure of the cubic garnet-type Li7La3Zr2O12 compound, it is suggested that the high internal friction peak in the cubic phase may be attributed to two diffusion processes of lithium ions: 96h↔96h and 96h↔24d.

Development of AL{sub 2}O{sub 3} - ZrO{sub 2} ceramic composite reinforced with rare earth oxides (Y{sub 2}O)3) for inert coating of storage and transport systems of crude petroleum; Desenvolvimento de composito ceramico Al{sub 2}O{sub 3} - ZrO{sub 2} reforcada com oxido de terra rara para sistema de armazenamento e transporte de petroleo cru

Energy Technology Data Exchange (ETDEWEB)

Silva, J.C.; Yadava, Y.P.; Sanguinetti Ferreira, R.A.; Albuquerque, L.T., E-mail: juliana.carvalhosilva@ufpe.br [Universidade Federal de Pernambuco (UFPE), Jaboatao de Guararapes, PE (Brazil). Centro de Tecnologia. Departamento de Engenharia Mecanica

2014-07-01

The advancement of the oil sector has generated the need for the use of materials resistant to aggressive environments to oil. Although ceramics have high melting point and high hardness is, on the other hand, more fragile and less tough, which can cause damage to the metal structure. The Al{sub 2}O{sub 3} based ceramics reinforced with rare earth oxide can improve tenaciousness and makes the ceramic material more resistant. This article aims to present the production of composite Al{sub 2}O{sub 3} - Y{sub 2}O{sub 3} stabilized ZrO{sub 2} by uniaxial pressing, following sintering (1200-1350 deg C). Structural and microstructural characterizations as XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscopy) and mechanical tests as Vickers hardness, % absorption and % linear shrinkage were conducted to evaluate the feasibility of using the composite and ceramic coating for storage and transportation of oil tanks. The results indicate that the proportions of 5%, 10% and 30% ZrO{sub 2} make it suitable as a good composite suitable coating. (author)

Phase transitions in complex oxide systems based on Al2O3 and ZrO2

International Nuclear Information System (INIS)

Gorski, L.

1999-01-01

Different compositions of materials based on Al 2 O 3 and ZrO 2 and protective coatings sprayed from them working in the high temperature region are studied. There are especially thermal barrier coatings of increasing resistance to thermal shocks and conditions of corrosion and erosion caused by the hot gases and liquids. Such conditions are encountered in many technical branches among others in jet and Diesel engines. These coatings are deposited by the plasma spraying process and their resistance to thermal shocks is studied on special experimental arrangement in the conditions near to coatings applications. Both above processes are characterized by a short time temperature action with subsequent high cooling rate, which may cause phase transitions other than in the conditions of thermodynamical equilibrium. These transitions are studied by X-ray diffraction analysis methods. The microstructure changes accompanied to phase transitions are determined by light microscopy and scanning electron microscopy methods. The cases of coating degradation caused by thermal shocks have been observed. The highest resistance to thermal fatigue conditions (up to thermal shocks) show coatings based on Al 2 O 3 containing aluminium titanate and coatings based on ZrO 2 stabilised by 7-8% of Y 2 O 3 . (author)

Air Plasma-Sprayed La2Zr2O7-SrZrO3 Composite Thermal Barrier Coating Subjected to CaO-MgO-Al2O3-SiO2 (CMAS)

Science.gov (United States)

Cai, Lili; Ma, Wen; Ma, Bole; Guo, Feng; Chen, Weidong; Dong, Hongying; Shuang, Yingchai

2017-08-01

La2Zr2O7-SrZrO3 composite thermal barrier coatings (TBCs) were prepared by air plasma spray (APS). The La2Zr2O7-SrZrO3 composite TBCs covered with calcium-magnesium-aluminum-silicate (CMAS) powder, as well as the powder mixture of CMAS and spray-dried La2Zr2O7-SrZrO3 composite powder, were heat-treated at 1250 °C in air for 1, 4, 8, and 12 h. The phase constituents and microstructures of the reaction products were characterized by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. Experimental results showed that the La2Zr2O7-SrZrO3 composite TBCs had higher CMAS resistance than 8YSZ coating. A dense new layer developed between CMAS and La2Zr2O7-SrZrO3 composite TBCs during interaction, and this new layer consisted mostly of apatite (Ca2La8(SiO4)6O2) and c-ZrO2. The newly developed layer effectively protected the La2Zr2O7-SrZrO3 composite TBCs from further CMAS attack.

Development and characterization of nickel catalysts supported in CeO{sub 2}-ZrO{sub 2}-Al{sub 2}O{sub 3}, CeO{sub 2}-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3} e ZrO{sub 2}-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3} matrixes evaluated for methane reforming reactions; Desenvolvimento e caracterização de catalisadores de níquel suportados em matrizes CeO{sub 2}-ZrO{sub 2}-Al{sub 2}O{sub 3}, CeO{sub 2}-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3} e ZrO{sub 2}-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3} avaliados para as reações de reforma do metano

Energy Technology Data Exchange (ETDEWEB)

Abreu, Amanda Jordão de

2012-07-01

Nowadays, the methane reforming is large interest industrial for the take advantage of these gas in production the hydrogen and synthesis gas (syngas). Among in the reactions of methane stand of the reactions steam reforming and carbon dioxide reforming of methane. The main catalysts uses in the methane reforming is Ni/Al{sub 2}O{sub 3}. However, the supported-nickel catalyst is susceptible to the deactivation or the destruction by coke deposition. The carbon dissolves in the nickel crystallite and its diffuses through the nickel, leading for formation of the carbon whiskers, which results in fragmentation of the catalyst. Modification of such catalysts, like incorporation of suitable promoters, is desirable to achieve reduction of the methane hydrogenolysis and/or promotion of the carbon gasification. Catalysts 5%Ni/Al{sub 2}O{sub 3} supported on solid solutions formed by ZrO{sub 2}-CeO{sub 2}, La{sub 2}O{sub 3} and CeO{sub 2}-ZrO{sub 2}-La{sub 2}O{sub 3} were prepared, characterized and evaluated in reactions steam and carbon dioxide reforming and partial oxidation of methane with objective the value effect loading solution solid in support. The supports were prepared by co-precipitation method and catalysts were prepared by impregnation method and calcined at 500 deg C. The supports and catalysts were characterized by Nitrogen Adsorption, method -rays diffraction (XRD), X-rays dispersive spectroscopy (XDS), spectroscopy in the region of the ultraviolet and the visible (UV-vis NIR) to and temperature programmed reduction (TPR), Raman Spectroscopy, X-ray absorption spectroscopy and Thermogravimetric Analysis. After all the catalytic reactions check which the addition of solid solution is beneficial for Ni/Al{sub 2}O{sub 3} catalysts and the best catalysts are Ni/CeO{sub 2}-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3}. (author)

Dual-Layer Oxidation-Protective Plasma-Sprayed SiC-ZrB2/Al2O3-Carbon Nanotube Coating on Graphite

Science.gov (United States)

Ariharan, S.; Sengupta, Pradyut; Nisar, Ambreen; Agnihotri, Ankur; Balaji, N.; Aruna, S. T.; Balani, Kantesh

2017-02-01

Graphite is used in high-temperature gas-cooled reactors because of its outstanding irradiation performance and corrosion resistance. To restrict its high-temperature (>873 K) oxidation, atmospheric-plasma-sprayed SiC-ZrB2-Al2O3-carbon nanotube (CNT) dual-layer coating was deposited on graphite substrate in this work. The effect of each layer was isolated by processing each component of the coating via spark plasma sintering followed by isothermal kinetic studies. Based on isothermal analysis and the presence of high residual thermal stress in the oxide scale, degradation appeared to be more severe in composites reinforced with CNTs. To avoid the complexity of analysis of composites, the high-temperature activation energy for oxidation was calculated for the single-phase materials only, yielding values of 11.8, 20.5, 43.5, and 4.5 kJ/mol for graphite, SiC, ZrB2, and CNT, respectively, with increased thermal stability for ZrB2 and SiC. These results were then used to evaluate the oxidation rate for the composites analytically. This study has broad implications for wider use of dual-layer (SiC-ZrB2/Al2O3) coatings for protecting graphite crucibles even at temperatures above 1073 K.

Indides RE{sub 3}T{sub 2}In{sub 4} (RE = Y, Gd-Tm, Lu; T = Ni, Ru, Rh) with a ZrNiAl superstructure

Energy Technology Data Exchange (ETDEWEB)

Heying, Birgit; Niehaus, Oliver; Rodewald, Ute C.; Poettgen, Rainer [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie

2016-07-01

Three series of rare earth-transition metal-indides RE{sub 3}T{sub 2}In{sub 4} (RE=Y, Gd-Tm, Lu; T=Ni, Ru, Rh) were synthesized from arc-melted RE{sub 3}T{sub 2} precursor compounds and indium tear shot in sealed niobium ampoules using different annealing sequences. The new indides crystallize with the hexagonal Lu{sub 3}Co{sub 2}In{sub 4}-type structure, space group P anti 6. All samples were characterized on the basis of Guinier powder patterns and six structures were refined from single crystal X-ray diffractometer data. The RE{sub 3}T{sub 2}In{sub 4} structures are derived from the ZrNiAl type through RE/In ordering, paralleled by a symmetry reduction from P anti 62m to P anti 6. This induces twinning for some of the investigated crystals. The main crystal chemical motifs of the RE{sub 3}T{sub 2}In{sub 4} structures are trigonal prisms of rare earth, respectively indium atoms that are filled by the transition metals.

Electronic structure of ZrX2 (X = Se, Te)

Science.gov (United States)

Shkvarin, A. S.; Merentsov, A. I.; Shkvarina, E. G.; Yarmoshenko, Yu. M.; Píš, I.; Nappini, S.; Titov, A. N.

2018-03-01

The electronic structure of the ZrX2 (X = Se, Te) compounds has been studied using photoelectron, resonant photoelectron and X-ray absorption spectroscopy, theoretical calculations of the X-ray absorption spectra, and density of electronic states. It was found that the absorption spectra and valence band spectra are influenced by the chalcogen type. The results of the multiplet calculation of the Zr4+ atom show that the change in the splitting in the crystal field, which is described by the 10Dq parameter, is due to the change in the ratio of covalent and ionic contributions to the chemical bond. The resonance band near the Fermi level in the valence band spectra is observed for ZrTe2 in the Zr 3p-4d resonant excitation mode. The extent of photon energy indicates the charge localization on the Zr atom. Similar resonance band for ZrSe2 is absent; it indicates the presence of a gap at the Fermi level.

Resistive switching in ZrO{sub 2} based metal-oxide-metal structures

Energy Technology Data Exchange (ETDEWEB)

Kaerkkaenen, Irina

2014-07-01

The goal of this work is a deeper understanding of the influence of the (i) metal-oxide-metal (MOM) layer stacks configuration, (ii) the oxide films microstructure, (iii) and their defect structure on the appearance of different switching modes, i.e. unipolar (UP) and bipolar (BP). The first part deals with the fabrication of ZrO{sub 2} thin films by an industrial compatible atomic layer deposition (ALD) process, the chemical, structural and morphological characterization of the films, the growth of ZrO{sub 2}/TiO{sub 2} bilayers, the integration of the layers into metal-oxide-metal (MOM) devices and the electrical characterization with focus on the RS behavior. In the second part the effect of the device structure, in particular the thickness of the electrochemical active electrode (EAE) and the ZrO{sub 2} film morphology, on the RS switching polarity of Pt/ZrO{sub 2}/(EAE) cells is discussed. ZrO{sub 2} films and ZrO{sub 2}/TiO{sub 2} bilayers were grown by ALD and were carefully structurally and electrically characterized. The ZrO{sub 2} films grown from Zr[N(CH{sub 3})C{sub 2}H{sub 5}]{sub 4} (TEMA-Zr) at 240 C were polycrystalline with a mixture of cubic/tetragonal phases. ALD/H{sub 2}O-ZrO{sub 2} films exhibited a random oriented polycrystalline structure, whereas the ALD/O{sub 3}-ZrO{sub 2} films consisted of preferably oriented cubic shaped grains. Pt/ZrO{sub 2}/Ti/Pt structures with a Ti top electrode (TE) thickness of 5 to 20 nm showed unipolar type RS behavior, while by increasing the Ti TE thickness a gradual change of switching polarity from unipolar to bipolar with a completely bipolar type RS behavior for a Ti TE thickness of 40 nm is found. The switching in Pt/ZrO{sub 2}/TiO{sub 2}/Ti/Pt devices was unipolar, comparable to Pt/ZrO{sub 2}/Ti/Pt cells. In contrast, bilayers with the reverse structure, Pt/TiO{sub 2}/ZrO{sub 2}/Ti/Pt, showed non-switching behavior. The effect of the cells stack structure on the polarity of the RS behavior was studied in

Influence of Al{sub 2}O{sub 3} addition on microstructure and mechanical properties of 3YSZ-Al{sub 2}O{sub 3} composites

Energy Technology Data Exchange (ETDEWEB)

Abden, Md. Jaynul [International Islamic Univ., Chittagong (Bangladesh). Dept. of Electrical and Electronic Engineering; Afroze, Jannatul Dil [Noakhali Science and Technology Univ. (Bangladesh). Faculty of Science and Engineering; Gafur, Md. Abdul [Bangladesh Council of Scientific and Industrial Research, Dhaka (Bangladesh). Pilot Plant and Process Development Centre; Chowdhury, Faruque-Uz-Zaman [Chittagong University of Engineering and Technology (Bangladesh). Dept. of Physics

2015-07-01

The effect of the amount of Al{sub 2}O{sub 3} content on microstructure, tetragonal phase stability and mechanical properties of 3YSZ-Al{sub 2}O{sub 3} composites are investigated in this study. The ceramic composites are obtained by means of uniaxial compacting at 210 MPa and green compacts are sintered at 1550 C for 3 h in air. The monoclinic zirconia (m-ZrO{sub 2}) phase has completely been transformed into tetragonal zirconia (t-ZrO{sub 2}) phase with corresponding higher Al{sub 2}O{sub 3} content. The t-ZrO{sub 2} grains induce transgranular fracture mode that has contribution in improvement of fracture toughness. The maximum flexural strength of 340 MPa, Vickers hardness value of 14.31 GPa and fracture toughness of 5.1 MPa x m{sup 1/2} in the composition containing 40 wt.-% Al{sub 2}O{sub 3} is attributed to the microstructure with t-ZrO{sub 2} grains as inter- and intragranular particles in the Al{sub 2}O{sub 3} grains, which makes it suitable for dental applications.

Electronic structures, elastic properties, and minimum thermal conductivities of cermet M{sub 3}AlN

Energy Technology Data Exchange (ETDEWEB)

Wang, Jin [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China); Key Laboratory of Liquid–Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Chen, ZhiQian, E-mail: chen_zq@swu.edu.cn [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China); Li, ChunMei; Li, Feng; Nie, ChaoYin [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China)

2014-08-15

The electronic structures and elastic anisotropies of cubic Ti{sub 3}AlN, Zr{sub 3}AlN, and Hf{sub 3}AlN are investigated by pseudopotential plane-wave method based on density functional theory. At the Fermi level, the electronic structures of these compounds are successive with no energy gap between conduct and valence bands, and exhibit metallicity in ground states. In valence band of each partial density of states, the different orbital electrons indicate interaction of corresponding atoms. In addition, the anisotropy of Hf{sub 3}AlN is found to be significantly different from that of Ti{sub 3}AlN and Zr{sub 3}AlN, which involve the differences in the bonding strength. It is notable that Hf{sub 3}AlN is a desired thermal barrier material with the lowest thermal conductivity at high temperature among the three compounds. - Graphical abstract: 1.Young's moduli of anti-perovskite Ti{sub 3}AlN, Zr{sub 3}AlN, and Hf{sub 3}AlN in full space. 2.Electron density differences on crystal planes (1 0 0), (2 0 0), and (1 1 0) of anti-perovskite Zr{sub 3}AlN. - Highlights: • We calculated three anti-perovskite cermets with first-principles theory. • We illustrated 3D Young modulus and found the anomalous anisotropy. • We explained the anomaly and calculated the minimum thermal conductivities.

Structure and defect studies of In2O3:Zn,Zr for higher stability TCO

Science.gov (United States)

Herwadkar, Aditi; Kim, Kwiseon

2010-03-01

The defects structures among the transparent conducting oxides (TCO) plays a major role in determining stability of the oxide over a temperature range and in tuning electrical and optical properties for the different TCO applications In2O3 crystallizes in the cubic bixbyite structure. The structure can be derived from the related fluorite structure by removing one fourth of the anions and allowing for small shifts of the ionic positions. In2O3 has two non-equivalent six-fold coordinated cation sites. For one of the sites, the cation is bounded by two structural vacancy along the body diagonal and for the other non-equivalent site the vacancies lie along the face diagonal. These vacancies are actually empty oxygen vacancy positions. Indium is in +3 charge state. ZnO on the other hand crystallizes to form wurtzite structure with four-fold coordination for Zn and is in +2 charge state where as the crystal structure of ZrO is rulite with Zr in +4 charge state and is four fold coordinated. Co-doping of Zn and Zr with each substituting the In atom satisfies the octet rule and is lower in energy then the individual substitutions with overall neutrality. The formation enthalpy as a function of pair (Zn, Zr) shows a minimum at experimental composition of In2(Zn,Zr)3O24. We in this work present the electronic structure optimization and study the defect states in this material.

Quaternary chalcogenides of the IVa metals with layered structures: preparation and crystal structures of TlCuTIVQ3 (T=Zr, Hf; Q=S, Se) and their relation to the Re3B structure type

International Nuclear Information System (INIS)

Klepp, K.O.; Gurtner, D.

1996-01-01

The new compounds TlCuT IV Q 3 (T = Zr, Hf; Q = S, Se) were prepared by reacting intimate mixtures of Tl 2 S or TlSe with stoichiometric amounts of the corresponding Group IV metal, Cu and the corresponding chalcogen at 870 . The four compounds are isostructural and crystallize in Cmcm, Z = 4 with a 3.726(4) A, b = 13.987(9) A, c = 9.783(4) A for TlCuZrS 3 ; a = 3.847(1) A, b 14.381(6) A, c = 10.150(1) A for TlCuZrSe 3 ; a = 3.694(1) A, b = 14.030(3) A, c = 9.750(3) A for TlCuHfS 3 ; and a = 3.831(1) A, b = 14.409(9) A, c = 10.124(2) A for TlCuHfSe 3 . Their crystal structures were determined from single crystal diffractometer data (Mo Kα radiation, ambient temperature) and refined to conventional R values of 0.016, 0.040, 0.019 and 0.031 respectively. An outstanding feature of their crystal structures is the formation of infinite anionic layers, 2 ∞ -[CuT IV Q 3 ] - parallel to (010), which are separated by Tl + cations. These layers are built up by edge sharing TQ 6 octahedra and distorted CuQ 4 tetrahedra. Average T-Q distances are anti d(Zr-S) = 2.586(1) A, anti d(Zr-Se) = 2.707(1) A, anti d(Hf-S) = 2.569(2) A and anti d(Hf-Se) = 2.694(1) A. Cu-chalcogen distances are anti d(Cu-S) = 2.318(2) A and anti d(Cu-Se) = 2.432(3) A respectively. The thallium ions are in bicapped trigonal prismatic chalcogen coordinations. The atomic arrangement corresponds to that of KCuZrS 3 ; based on the thallium-chalcogen partial structure it can be regarded as a filled variant of an anti-Re 3 B structure type. (orig.)

Effect of the theta-alpha-Al2O3 transformation on the oxidation behavior of beta-NiAl+Zr

Science.gov (United States)

Rybicki, George C.; Smialek, James L.

1989-01-01

Isothermal oxidation of NiAl+Zr has been performed over the temperature range of 800-1200 C and studied by TGA, XRD, and SEM. A discontinuous decrease in growth rate of two orders of magnitude was observed at 1000 C due to the formation of alpha-Al2O3 from theta-Al2O3. This transformation also resulted in a dramatic change in the surface morphology of the scales, as a whisker topography was changed into a weblike network of oxide ridges and radial transformation cracks. It is believed that the ridges are evidence for a short-circuit outward aluminum diffusion growth mechanism that has been documented in a number of O-18 tracer studies.

Investigation into the use of CaZrO3 as a facecoat material in the investment casting of TiAl alloys

International Nuclear Information System (INIS)

Yuan, C.; Cheng, X.; Withey, P.A.

2015-01-01

Research was carried out to determine the interactions between the filler and stucco materials in CaZrO 3 based facecoats during shell firing as well as between the facecoat and a TiAl alloy during the casting process. A ‘flash re-melting’ technique, which gives a similar heating profile to the actual investment casting process, was used to study the phase transformations in the shell moulds. The chemical inertness of the facecoat was then investigated using a sessile drop test using a Ti–45Al–2Nb–2Mn–0.2TiB alloy. In this study, the facecoat compositions and the interaction products between metal and shells were characterized using x-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A severe interaction was found between CaZrO 3 filler and Al 2 O 3 stucco, which rapidly damaged the shell surface. As well as oxygen, zirconium and silicon ions from the shell moulds were also observed to penetrate into the TiAl metal to form (Ti, Zr) 5 (Al, Si) 3 phases in the metal/shell interfacial areas. - Highlights: • To determine the interactions between CaZrO 3 filler and stucco materials during shell firing. • To study the reaction between the CaZrO 3 facecoat and TiAl alloy during casting. • The Al 2 O 3 stucco can react with CaZrO 3 filler to form (Zr, Ca)O 2 and CaAl x O y at 1650 °C. • O, Zr and Si ions from the ceramic moulds were observed to penetrate into the TiAl metal. • The reaction products include (Ti, Zr) 5 (Al, Si) 3 and ZrAl 2 phase with high Ti ions solid solution

Effect of Si and Zr on the Microstructure and Properties of Al-Fe-Si-Zr Alloys

Directory of Open Access Journals (Sweden)

Anna Morozova

2017-11-01

Full Text Available The effects of Si and Zr on the microstructure, microhardness and electrical conductivity of Al-Fe-Si-Zr alloys were studied. An increase in the Zr content over 0.3 wt. % leads to the formation of primary Al3Zr inclusions and also decreases mechanical properties. Therefore, the Zr content should not be more than 0.3 wt. %, although the smaller content is insufficient for the strengthening by the secondary Al3Zr precipitates. The present results indicate that high content of Si significantly affects the hardness and electrical conductivity of the investigated alloys. However, the absence of Si led to the formation of harmful needle-shaped Al3Fe particles in the microstructure of the investigated alloys after annealing. Therefore, the optimum amount of Si was 0.25–0.50 wt. % due to the formation of the Al8Fe2Si phase with the preferable platelet morphology. The maximum microhardness and strengthening effects in Al-1% Fe-0.25% Si-0.3% Zr were observed after annealing at 400–450 °C due to the formation of nanosized coherent Al3Zr (L12 dispersoids. The effect of the increasing of the electrical conductivity can be explained by the decomposition of the solid solution. Thus, Al-1% Fe-0.25% Si-0.3% Zr alloy annealed at 450 °C has been studied in detail as the most attractive with respect to the special focus on transmission line applications.

27Al nuclear magnetic resonance of glassy and crystalline Zr(1-x)AlxO(2-x/2) materials prepared from solution precursors

International Nuclear Information System (INIS)

Balmer, M.L.; Eckert, H.; Das, N.; Lange, F.F.

1996-01-01

The local environment of the aluminum atoms in a series of metastable Zr (1-x) Al x O (2-x/2) crystalline materials (0.08 ≤ x ≤ 0.57), prepared by diffusion-limited crystallization of amorphous precursors, has been determined by 27 Al magic angle spinning nuclear magnetic resonance (MAS NMR). Results show the existence of aluminum in 4-, 5-, and 6-fold coordination in both the amorphous and crystalline states. Although the relative amounts of each type of coordination show no compositional dependence in the amorphous state, the results for the crystalline materials show a systematic decrease in the average aluminum coordination number with increasing aluminum content. Comparisons of MAS NMR results between pure Al 2 O 3 precursors and Zr (1-x) Al x O (2-x/2) crystalline materials processed under similar conditions show a profound effect of ZrO 2 on the coordination environment of the aluminum atom. Both a random distribution model and a model that assumes small-scale clustering of aluminum ions are considered to explain the trends in the type of aluminum coordination as a function of composition

Can reduced size of metals induce hydrogen absorption: ZrAl{sub 2} case

Energy Technology Data Exchange (ETDEWEB)

Jacob, I., E-mail: izi@bgu.ac.il [Department of Nuclear Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel); Deledda, S. [Physics Department, Institute for Energy Technology, P.O. Box 40, NO-2027 Kjeller (Norway); Bereznitsky, M. [Department of Nuclear Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel); Yeheskel, O. [Nuclear Research Center - Negev, P.O. Box 9001, Beer Sheva 84190 (Israel); Filipek, S.M. [Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw (Poland); Mogilyanski, D.; Kimmel, G. [Institute for Applied Research, P.O. Box 653, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel); Hauback, B.C. [Physics Department, Institute for Energy Technology, P.O. Box 40, NO-2027 Kjeller (Norway)

2011-09-15

Research highlights: > 15 nm particles of ZrAl{sub 2} and Zr(Al{sub 0.5}Co{sub 0.5}){sub 2} are obtained by attrition and cryomilling. > ZrAl{sub 2} nanoparticles remain inert to hydrogen absorption up to pressure of {approx}2 GPa. > Zr(Al{sub 0.5}Co{sub 0.5}){sub 2} nanoparticles exhibit reduced hydrogen absorption as compared to the corresponding bulk compounds. - Abstract: The hydrogen absorption ability of the non-absorbing Al-rich ZrAl{sub 2} compound was examined after reducing its particles-size to the nanometer regime. The hydrogen abstinence of bulk ZrAl{sub 2} has been previously related to its excessive elastic shear stiffening. The particle size of ZrAl{sub 2} was reduced by attrition milling and cryomilling. The minimal average particle size was estimated from powder X-ray diffraction analysis to be in the range of 10-20 nm. The hydrogen absorption of the milled compounds was measured in different hydrogenation systems at hydrogen pressures between {approx}6 MPa and {approx}2 GPa. In all the cases the hydrogen absorption was negligible. In addition, there was a reduction of the hydrogen absorption capacity of nanosized Zr(Al{sub 0.5}Co{sub 0.5}){sub 2} as compared to the corresponding bulk compound at the same conditions. We suggest, in view of our and other results, that no significant improvement of the thermodynamics (unlike the kinetics) of the hydrogen absorption can be achieved via the nanoparticle avenue.

Tracking the path of dislocations across ordered Al3Zr nano-precipitates in three dimensions

International Nuclear Information System (INIS)

Lefebvre, W.; Masquelier, N.; Houard, J.; Patte, R.; Zapolsky, H.

2014-01-01

Graphical abstract: -- We report on the shear–bypassing transition of chemically ordered Al 3 Zr nanoprecipitates. Observation of complex combinations of lattice translations, revealed by scanning transmission electron microscopy, is used as the signature of precipitate shearing during cold deformation. A method is proposed to build a three-dimensional atomic model of sheared particles from a set of three atomic scale projections. An estimation of the antiphase boundary energy of the Al 3 Zr structure is achieved via the comparison of experimental findings to a model of precipitation hardening

High temperature steam oxidation of Al3Ti-based alloys for the oxidation-resistant surface layer on Zr fuel claddings

International Nuclear Information System (INIS)

Park, Jeong-Yong; Kim, Il-Hyun; Jung, Yang-Il; Kim, Hyun-Gil; Park, Dong-Jun; Choi, Byung-Kwon

2013-01-01

We investigated the feasibility to apply Al 3 Ti-based alloys as the surface layer for improving the oxidation resistance of Zr fuel claddings under accident conditions. Two types of Al 3 Ti-based alloys with the compositions of Al–25Ti–10Cr and Al–21Ti–23Cr in atomic percent were prepared by arc-melting followed by homogenization annealing at 1423 K for 48 h. Al–25Ti–10Cr alloy showed an L1 2 quasi-single phase microstructure with a lot of needle-shaped minor phase and pores. Al–21Ti–23Cr alloy consisted of an L1 2 matrix and Cr 2 Al as the second phase. Al 3 Ti-based alloys showed an extremely low oxidation rate in a 1473 K steam for up to 7200 s when compared to Zircaloy-4. Both alloys exhibited almost the same oxidation rate in the early stage of oxidation, but Al–25Ti–10Cr showed a little lower oxidation rate after 4000 s than Al–21Ti–23Cr. The difference in the oxidation rate between two types of Al 3 Ti-based alloys was too marginal to distinguish the oxidation behavior of each alloy. The resultant oxide exhibited almost the same characteristics in both alloys even though the microstructure was explicitly distinguished from each other. The crystal structure of the oxide formed up to 2000 s was identified as Al 2 O 3 in both alloys. The oxide morphology consisted of columnar grains whose length was almost identical to the average oxide thickness. On the basis of the results obtained, it is considered that Al 3 Ti-based alloy is one of the promising candidates for the oxidation-resistant surface layer on Zr fuel claddings

The behavior of ZrO_2/20%Y_2O_3 and Al_2O_3 coatings deposited on aluminum alloys at high temperature regime

International Nuclear Information System (INIS)

Pintilei, G.L.; Crismaru, V.I.; Abrudeanu, M.; Munteanu, C.; Baciu, E.R.; Istrate, B.; Basescu, N.

2015-01-01

Highlights: • In both the ZrO_2/20%Y_2O_3 and Al_2O_3 coatings the high temperature caused a decrease of pores volume and a lower thickness of the interface between successive splats. • The NiCr bond layer in the sample with a ZrO_2/20%Y_2O_3 suffered a fragmentation due to high temperature exposure and thermal expansion which can lead to coating exfoliation. • The NiCr bond layer in the sample with an Al_2O_3 coating showed an increase of pore volume due to high temperature. - Abstract: Aluminum alloy present numerous advantages like lightness, high specific strength and diversity which recommend them to a high number of applications from different fields. In extreme environments the protection of aluminum alloys is difficult and requires a high number of requirements like high temperature resistance, thermal fatigue resistance, corrosion fatigue resistance and galvanic corrosion resistance. To obtain these characteristics coatings can be applied to the surfaces so they can enhance the mechanical and chemical properties of the parts. In this paper two coatings were considered for deposition on an AA2024 aluminum alloy, ZrO_2/20%Y_2O_3 and Al_2O_3. To obtain a better adherence of the coating to the base material an additional bond layer of NiCr is used. Both the coatings and bond layer were deposited by atmospheric plasma spraying on the samples. The samples were subjected to a temperature of 500 °C and after that slowly cooled to room temperature. The samples were analyzed by electron microscopy and X-ray diffraction to determine the morphological and phase changes that occurred during the temperature exposure. To determine the stress level in the parts due to thermal expansion a finite element analysis was performed in the same conditions as the tests.

New Intermetallic Ternary Phosphide Chalcogenide AP2-xXx (A = Zr, Hf; X = S, Se) Superconductors with PbFCl-Type Crystal Structure

Science.gov (United States)

Kitô, Hijiri; Yanagi, Yousuke; Ishida, Shigeyuki; Oka, Kunihiko; Gotoh, Yoshito; Fujihisa, Hiroshi; Yoshida, Yoshiyuki; Iyo, Akira; Eisaki, Hiroshi

2014-07-01

We have synthesized a series of intermetallic ternary phosphide chalcogenide superconductors, AP2-xXx (A = Zr, Hf; X = S, Se), using the high-pressure synthesis technique. These materials have a PbFCl-type crystal structure (space group P4/nmm) when x is greater than 0.3. The superconducting transition temperature Tc changes systematically with x, yielding dome-like phase diagrams. The maximum Tc is achieved at approximately x = 0.7, at which point the Tc is 6.3 K for ZrP2-xSex (x = 0.75), 5.5 K for HfP2-xSex (x = 0.7), 5.0 K for ZrP2-xSx (x = 0.675), and 4.6 K for Hfp2-xSx (x = 0.5). They are typical type-II superconductors and the upper and lower critical fields are estimated to be 2.92 T at 0 K and 0.021 T at 2 K for ZrP2-xSex (x = 0.75), respectively.

Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr)

Science.gov (United States)

Lee, Jonathan A.

2009-01-01

In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low cost, chemical stability and low diffusions rates in aluminum at high temperatures. The strengthening mechanism at high temperature for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. For Al2O3 nanoparticles, the test samples were prepared from special Al2O3 preforms, which were produced using ceramic injection molding process and then pressure infiltrated by molten aluminum. In another method, Al2O3 nanoparticles can also be homogeneously mixed with fine aluminum powder and consolidated into test samples through hot pressing and sintering. With the Al3-X nanoparticles, the test samples are produced as precipitates from in-situ reactions with molten aluminum using conventional permanent mold or die casting techniques. It is found that cast aluminum alloy using nanoparticles Al3-X is the most cost effective method to produce high strength aluminum alloys for high temperature applications in comparison to nanoparticles Al2O3. Furthermore, significant mechanical properties retention in high temperature environment could be achieved with Al3-X nanoparticles, resulting in tensile strength of nearly 3 times higher than most 300- series conventional cast aluminum alloys tested at 600 F.

Comparison of structural and electric properties of PbZr0.2Ti0.8O3 and CoFe2O4/PbZr0.2Ti0.8O3 films on (100)LaAlO3

Science.gov (United States)

Zhang, X. D.; Dho, Joonghoe; Park, Sungmin; Kwon, Hyosang; Hwang, Jihwan; Park, Gwangseo; Kwon, Daeyoung; Kim, Bongju; Jin, Yeryeong; Kim, Bog. G.; Karpinsky, D.; Kholkin, A. L.

2011-09-01

In this work, we investigated structural, electrical, and magnetic properties of ferroelectric PbZr0.2Ti0.8O3 (PZT) and ferrimagnetic/ferroelectric [CoFe2O4(CFO)/PZT] bilayers grown on (100)LaAlO3 (LAO) substrates supplied with bottom 50 nm thick LaNiO3 electrodes. Interestingly, structural and electrical properties of the PZT layer exhibited remarkable changes after the top-layer CFO deposition. X-ray diffraction data suggested that both the c- and a-domains exist in the PZT layer and the tetragonality of the PZT decreases upon the top-layer deposition. A variation in the electrical properties of the PZT layer upon the CFO deposition was investigated by polarization versus voltage (P-V), capacitance versus voltage (C-V), and capacitance versus frequency (C-f) measurements. The CFO deposition induced a slight decrease of the remnant polarization and more symmetric behavior of P-V loops as well as led to the improvement of fatigue behavior. The tentative origin of enhanced fatigue endurance is discussed based on the measurement results. These results were corroborated by local piezoelectric measurements. Ferrimagnetic property of the CFO/PZT bilayer was confirmed by magnetic measurement at room temperature.

Investigation of electronic, magnetic and thermoelectric properties of Zr{sub 2}NiZ (Z = Al,Ga) ferromagnets

Energy Technology Data Exchange (ETDEWEB)

Yousuf, Saleem, E-mail: nengroosaleem17@gmail.com; Gupta, Dinesh C., E-mail: sosfizix@gmail.com

2017-05-01

Systematic investigation of impact of electronic structure and magnetism, on the thermoelectric properties of new Zr{sub 2}NiZ (Z = Al, Ga) Heusler alloys are determined using density functional theory calculations. Half-metallicity with ferromagnetic character is supported by their 100% spin polarizations at the Fermi level. Magnetic moment of ∼3 μ{sub B} is according to the Slater-Puling rule, enables their practical applications. Electron density plots are used to analyse the nature of bonding and chemical composition. Boltzmann's theory is conveniently employed to investigate the thermoelectric properties of these compounds. The analysis of the thermal transport properties specifies the Seebeck coefficient as 25.6 μV/K and 18.6 μV/K at room temperature for Zr{sub 2}NiAl and Zr{sub 2}NiGa, respectively. The half-metallic nature with efficient thermoelectric coefficients suggests the likelihood of these materials to have application in designing spintronic devices and imminent thermoelectric materials. - Highlights: • The compounds are half-metallic ferromagnets. • 100% spin-polarized compounds for spintronics. • Increasing Seebeck coefficient over a wide temperature range. • Zr{sub 2}NiAl is efficient thermoelectric material than Zr{sub 2}NiGa.

Defect structure of TiS{sub 3} single crystals of the A-ZrSe{sub 3} type

Energy Technology Data Exchange (ETDEWEB)

Bolotina, N. B., E-mail: nb-bolotina@mail.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” (Russian Federation); Gorlova, I. G. [Russian Academy of Sciences, Kotel’nikov Institute of Radioengineering and Electronics (Russian Federation); Verin, I. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” (Russian Federation); Titov, A. N. [Russian Academy of Sciences, Mikheev Institute of Metal Physics, Ural Branch (Russian Federation); Arakcheeva, A. V. [Phase Solutions, Co Ltd. (Switzerland)

2016-11-15

The defect structure of TiS{sub 3} single crystals of the A-ZrSe{sub 3} type has been determined based on X-ray diffraction data. Shear defects manifest themselves as displacements of ab layers (which can imitate a twin) by ∼0.5a. Regular shears facilitate the formation of a superstructure along the c axis. A model of defect in the layer structure is proposed to explain the atomic displacements at an angle to the layer plane.

Frictional properties of CeO$_{2}$-Al$_{2}$O$_{3}$-ZrO$_{2}$ plasma-sprayed film under mixed and boundary lubricating conditions

CERN Document Server

Kita, H; Osumi, K; 10.2109/jcersj.112.615

2004-01-01

In order to find a counterpart for reducing the frictional coefficient of Al/sub 2/O/sub 3/-ZrO/sub 2/-CeO/sub 2/ plasma-sprayed film, the sliding properties in mixed and boundary lubricating conditions was investigated. It was found that combination of a CrN- coated cast iron pin and an Al/sub 2/O/sub 3/-ZrO/sub 2/-CeO/sub 2/ plasma sprayed plate provided the lowest frictional coefficient among several combinations chosen from practical materials. The coefficient of friction was much lower than that of the materials combination widely used for piston ring and cylinder liner. It was inferred that the combination of a pin made of hard materials with high density, a smooth surface such as CrN-coated cast iron and a porous plate can reduce the frictional coefficient because less sliding resistance is implemented and porosity retains oil.

Atom probe tomographic studies of precipitation in Al-0.1Zr-0.1Ti (at.%) alloys.

Science.gov (United States)

Knipling, Keith E; Dunand, David C; Seidman, David N

2007-12-01

Atom probe tomography was utilized to measure directly the chemical compositions of Al(3)(Zr(1)-(x)Ti(x)) precipitates with a metastable L1(2) structure formed in Al-0.1Zr-0.1Ti (at.%) alloys upon aging at 375 degrees C or 425 degrees C. The alloys exhibit an inhomogeneous distribution of Al(3)(Zr(1)-(x)Ti(x)) precipitates, as a result of a nonuniform dendritic distribution of solute atoms after casting. At these aging temperatures, the Zr:Ti atomic ratio in the precipitates is about 10 and 5, respectively, indicating that Ti remains mainly in solid solution rather than partitioning to the Al(3)(Zr(1)-(x)Ti(x)) precipitates. This is interpreted as being due to the very small diffusivity of Ti in alpha-Al, consistent with prior studies on Al-Sc-Ti and Al-Sc-Zr alloys, where the slower diffusing Zr and Ti atoms make up a small fraction of the Al(3)(Zr(1)-(x)Ti(x)) precipitates. Unlike those alloys, however, the present Al-Zr-Ti alloys exhibit no interfacial segregation of Ti at the matrix/precipitate heterophase interface, a result that may be affected by a significant disparity in the evaporation fields of the alpha-Al matrix and Al(3)(Zr(1)-(x)Ti(x)) precipitates and/or a lack of local thermodynamic equilibrium at the interface.

Epitaxial growth and properties of YBa2Cu3O(x)-Pb(Zr(0.6)Ti(0.4))O3-YBa2Cu3O(x) trilayer structure by laser ablation

Science.gov (United States)

Boikov, Iu. A.; Esaian, S. K.; Ivanov, Z. G.; Brorsson, G.; Claeson, T.; Lee, J.; Safari, A.

1992-08-01

YBa2Cu3O(x)Pb(Zr(0.6)Ti(0.4))O3-YBa2Cu3O(x) multilayer structure has been grown on SrTiO3 and Al2O3 substrates using laser ablation. The deposition conditions for the growth of trilayers and their properties are studied in this investigation. Scanning electron microscope images and X-ray diffraction analyses indicate that all the constituent films in the trilayer grow epitaxially on SrTiO3 and were highly oriented on Al2O3. Transport measurements on these multilayers show that top YBa2Cu3O(x) films have good superconducting properties.

Preparation of Ca0.5Zr2(PO4)3 and Ca0.45Eu0.05Zr2(PO4)3 nanopowders: structural characterization and luminescence emission study

International Nuclear Information System (INIS)

Alcaraz, L; Isasi, J; Díaz-Guerra, C; Peiteado, M; Caballero, A C

2016-01-01

Ca 0.5 Zr 2 (PO 4 ) 3 and Ca 0.45 Eu 0.05 Zr 2 (PO 4 ) 3 nanophosphors have been synthesized by a sol–gel process under acid and basic conditions. In order to achieve the reduction of Eu 3+ to Eu 2+ , europium-doped samples were treated in a reducing atmosphere flow. The effects of the different synthesis conditions and the partial substitution of calcium by europium ions on the structure of the samples were analyzed by x-ray diffraction (XRD) transmission electron microscopy (TEM) and micro-Raman spectroscopy. Luminescence and magnetic properties were investigated by photoluminescence (PL) spectroscopy and magnetic susceptibility measurements. XRD patterns can be indexed to a rhombohedral symmetry of space group R-3 with Z  =  6, consistent with a NASICON-type structure. A higher crystallinity was found in the samples prepared under basic conditions. TEM images of all the synthesized samples show spherically shaped particles. A broadening of the Raman bands as a result of non-equivalent vibrations of the orthophosphate groups is observed for samples prepared under acid conditions. The same effect was found when calcium is substituted by europium into the Ca 0.5 Zr 2 (PO 4 ) 3 host. PL spectra exhibit strong emission in the blue-green spectral range due to Eu 2+ 4f 6 5d 1 -4f 7 transitions and no evidence of Eu 3+ emission. Magnetic measurements confirm the 2+  oxidation state of europium ions in all samples. (paper)

Investigation into the use of CaZrO{sub 3} as a facecoat material in the investment casting of TiAl alloys

Energy Technology Data Exchange (ETDEWEB)

Yuan, C., E-mail: c.yuan@bham.ac.uk [School of Metallurgy and Materials, The University of Birmingham, B152TT (United Kingdom); Cheng, X. [School of Metallurgy and Materials, The University of Birmingham, B152TT (United Kingdom); School of Material Science and Engineering, Beihang University, No, 37 Xueyuan Street, Haidian District, Beijing 100191 (China); Withey, P.A. [School of Metallurgy and Materials, The University of Birmingham, B152TT (United Kingdom); Rolls-Royce plc. (United Kingdom)

2015-04-01

Research was carried out to determine the interactions between the filler and stucco materials in CaZrO{sub 3} based facecoats during shell firing as well as between the facecoat and a TiAl alloy during the casting process. A ‘flash re-melting’ technique, which gives a similar heating profile to the actual investment casting process, was used to study the phase transformations in the shell moulds. The chemical inertness of the facecoat was then investigated using a sessile drop test using a Ti–45Al–2Nb–2Mn–0.2TiB alloy. In this study, the facecoat compositions and the interaction products between metal and shells were characterized using x-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A severe interaction was found between CaZrO{sub 3} filler and Al{sub 2}O{sub 3} stucco, which rapidly damaged the shell surface. As well as oxygen, zirconium and silicon ions from the shell moulds were also observed to penetrate into the TiAl metal to form (Ti, Zr){sub 5}(Al, Si){sub 3} phases in the metal/shell interfacial areas. - Highlights: • To determine the interactions between CaZrO{sub 3} filler and stucco materials during shell firing. • To study the reaction between the CaZrO{sub 3} facecoat and TiAl alloy during casting. • The Al{sub 2}O{sub 3} stucco can react with CaZrO{sub 3} filler to form (Zr, Ca)O{sub 2} and CaAl{sub x}O{sub y} at 1650 °C. • O, Zr and Si ions from the ceramic moulds were observed to penetrate into the TiAl metal. • The reaction products include (Ti, Zr){sub 5}(Al, Si){sub 3} and ZrAl{sub 2} phase with high Ti ions solid solution.

Microstructure and Phase Analysis in Mn-Al and Zr-Co Permanent Magnets

Science.gov (United States)

Lucis, Michael J.

In America's search for energy independence, the development of rare-earth free permanent magnets is one hurdle that still stands in the way. Permanent magnet motors provide a higher efficiency than induction motors in applications such as hybrid vehicles and wind turbines. This thesis investigates the ability of two materials, Mn-Al and Zr-Co, to fill this need for a permanent magnet material whose components are readily available within the U.S. and whose supply chain is more stable than that of the rare-earth materials. This thesis focuses on the creation and optimization of these two materials to later be used as the hard phase in nanocomposites with high energy products (greater than 10 MGOe). Mn-Al is capable of forming the pure L10 structure at a composition of Mn54Al43C3. When Mn is replaced by Fe or Cu using the formula Mn48Al43C3T6 the anisotropy constant is lowered from 1.3·107 ergs/cm3 to 1.0·107 ergs/cm3 and 0.8·10 7 ergs/cm3 respectively. Previous studies have reported a loss in magnetization in Mn-Al alloys during mechanical milling. The reason for this loss in magnetization was investigated and found to be due to the formation of the equilibrium beta-Mn phase of the composition Mn3Al2 and not due to oxidation or site disorder. It was also shown that fully dense Mn-Al permanent magnets can be created at hot pressing temperatures at or above 700°C and that the epsilon-phase to tau-phase transition and consolidation can be combined into a single processing step. The addition of small amounts of Cu to the alloy, 3% atomic, can increase the compaction density allowing high densities to be achieved at lower pressing temperatures. While the structure is still under debate, alloys at the composition Zr2Co11 in the Zr-Co system have been shown to have hard magnetic properties. This thesis shows that multiple structures exist at this Zr2Co11 composition and that altering the cooling rate during solidification of the alloy affects the ratio of the phase

Analytical electron microscopy investigation of the AlN-ZrO2 system

International Nuclear Information System (INIS)

Stoto, T.; Doukhan, J.C.; Mocellin, A.

1989-01-01

A combination of electron microscopy, diffraction, and spectroscopic techniques were used to identify and characterize the quaternary Zr-Al-O-N phase, which forms during reaction sintering of AIN + ZrO 2 mixtures. In this paper it is proposed that this phase has a space group Fd 3 m; several compositions are suggested

Kinetic studies of oxidation of MgAlON and a comparison of the oxidation behaviour of AlON, MgAlON, O'SiAlON-ZrO{sub 2}, and BN-ZCM ceramics

Energy Technology Data Exchange (ETDEWEB)

Wang Xidong; Seetharaman, S. [Div. of Metallurgy, Royal Inst. of Tech., Stockholm (Sweden); Li Wenchao [Dept. of Physical Chemistry, Univ. of Science and Technology Beijing (USTB), Beijing, BJ (China)

2002-06-01

The kinetics and morphology of the oxidation process of magnesium-aluminium oxynitride (MgAlON), aluminium oxynitride (AlON), O'SiAlON-ZrO{sub 2}, and BN-ZCM have been studied in the temperature range 1373-1773 K (ZCM=30 wt% ZrO{sub 2}, 52 wt% Al{sub 2}O{sub 3} and 18 wt% 3 Al{sub 2}O{sub 3}.2 SiO{sub 2}). Oxidation experiments with powder and plate samples of the above materials have been carried out in air. MgAlON shows the best resistance to oxidation at lower temperatures (< 1473 K), whereas at higher temperatures ({proportional_to} 773 K), AlON shows the best resistance. O'SiAlON-ZrO{sub 2} shows very good oxidation resistance up to 1673 K. But its oxidation rate increases strongly above 1673 K, presumably due to the formation of liquid phase. BN-ZCM has the poorest oxidation resistance due to the evaporation of B{sub 2}O{sub 3}. The activation energies for the chemical oxidation reaction of AlON, MgAlON, and O'SiAlON-ZrO{sub 2} are 214, 330 and 260 kJ/mol, respectively. The overall diffusion activation energies for AlON, MgAlON, O'SiAlON-ZrO{sub 2} and BN-ZCM are 227, 573, 367 and 289 kJ/mol, respectively. (orig.)

Vacancy-type defects in Al2O3/GaN structure probed by monoenergetic positron beams

Science.gov (United States)

Uedono, Akira; Nabatame, Toshihide; Egger, Werner; Koschine, Tönjes; Hugenschmidt, Christoph; Dickmann, Marcel; Sumiya, Masatomo; Ishibashi, Shoji

2018-04-01

Defects in the Al2O3(25 nm)/GaN structure were probed by using monoenergetic positron beams. Al2O3 films were deposited on GaN by atomic layer deposition at 300 °C. Temperature treatment above 800 °C leads to the introduction of vacancy-type defects in GaN due to outdiffusion of atoms from GaN into Al2O3. The width of the damaged region was determined to be 40-50 nm from the Al2O3/GaN interface, and some of the vacancies were identified to act as electron trapping centers. In the Al2O3 film before and after annealing treatment at 300-900 °C, open spaces with three different sizes were found to coexist. The density of medium-sized open spaces started to decrease above 800 °C, which was associated with the interaction between GaN and Al2O3. Effects of the electron trapping/detrapping processes of interface states on the flat band voltage and the defects in GaN were also discussed.

Ferromagnetic resonance spectroscopy of CoFeZr-Al{sub 2}O{sub 3} granular films containing “FeCo core – oxide shell” nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Kołtunowicz, Tomasz N., E-mail: t.koltunowicz@pollub.pl [Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, Nadbystrzycka 38a, 20-618 Lublin (Poland); Zukowski, Pawel [Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, Nadbystrzycka 38a, 20-618 Lublin (Poland); Sidorenko, Julia [Department of Semiconductors Physics and Nanoelectronics, Belarusian State University, Independence Av. 4, 220030 Minsk (Belarus); Bayev, Vadim; Fedotova, Julia A. [Institute for Nuclear Problems, Belarusian State University, Bobrujskaya Str. 11, 220030 Minsk (Belarus); Opielak, Marek [Institute of Transport, Combustion Engines and Ecology, Lublin University of Technology, Nadbystrzycka 36, 20-618 Lublin (Poland); Marczuk, Andrzej [Department of Transporting and Agricultural Machinery, University of Life Sciences in Lublin, Głeboka 28, 20-612 Lublin (Poland)

2017-01-01

Ferromagnetic resonance (FMR) spectroscopy is applied for comparative analysis of granular (CoFeZ){sub x}(Al{sub 2}O{sub 3}){sub 100−x}, (31 at%≤x≤47 at%) films containing pure FeCo-based nanoparticles (NPs) or “FeCo-based core – oxide shell” NPs inside Al{sub 2}O{sub 3} matrix when deposited in oxygen-free or oxygen-containing atmosphere, correspondingly. It is established that g-factor extracted from the FMR spectra of films with core–shell NPs decreases with x below the value g =2.0023 for free electron that is untypical for metallic NPs. This effect is associated with the formation of the interface between ferromagnetic core and antiferromagnetic (ferrimagnetic) oxide shell of NPs. - Highlights: • CoFeZr-Al{sub 2}O{sub 3} granular films containing “FeCo core – oxide shell” nanoparticles. • magnetic anisotropy of (CoFeZr){sub x}(Al{sub 2}O{sub 3}){sub 100−x} films is of an easy plane type. • essential difference in dependence of g-factor on metal content in non- and oxidized film. • non-oxidized samples indicates the reduction of the value of films magnetization.

Electrical and mechanical properties of 0.5Ba (Zr0.2Ti0.8)O3-0.5 (Ba0.7Ca0.3)TiO3 (BZT-BCT) lead free ferroelectric ceramics reinforced with Al2O3 nano-oxide

International Nuclear Information System (INIS)

Adhikari, Prativa; Mazumder, R.

2014-01-01

Piezoelectric ceramics are widely used as actuator, resonator, and spark igniter. Recently, much attention has been paid to prepare 0.5Ba (Zr 0.2 Ti 0.8 )O 3 -0.5 (Ba 0.7 Ca 0.3 )TiO 3 (BZT-BCT) piezoelectric ceramics because of its good dielectric, piezoelectric properties and environment friendly nature. However, piezoelectric ceramics based on BaTiO 3 suffer from low reliability and poor mechanical properties such as strength and toughness. For practical application improvement of the mechanical properties of BaTiO 3 -based ceramics is strongly required. A novel method has been used to improve the mechanical properties of structural ceramics by reinforcement of oxide (Al 2 O 3 , MgO, ZrO 2 and Stabilized-ZrO 2 ) or non-oxide (SiC) particles. It is well known that electrical properties of ferroelectric ceramics generally degrade with non-ferroelectric additives and decrease in sinterability usually encountered with refractory oxide additives. Use of nano-oxide additives may drastically reduce the amount of additive and electrical property may not degrade much. In this report we would show the electrical and mechanical properties of BZT-BCT with Al 2 O 3 nano oxide additive. Modified BZT-BCT nanocomposites were prepared by mixing and sintering of solid state synthesized Zr, Ca modified barium titanate powder and small amount (0.1-2.0 vol %) of nano-oxides, i.e. Al 2 O 3 . Effect of sintering temperature, time, particle size of the nano-oxide additives on electrical (dielectric constant, loss factor, Curie temperature, d 33 ) and mechanical (flexural strength, fracture toughness, hardness) properties were studied. We obtained ∼ 94% dense BZT-BCT reinforced with Al 2 O 3 nano-oxide at 1300℃ without degrading electrical properties (dielectric constant (4850), low dissipation factor (0.0242)) and superior mechanical properties (flexural strength - 60.3 MPa, Vickers hardness-750-800 MPa). (author)

Hydrogenation/Deoxygenation (H/D Reaction of Furfural-Acetone Condensation Product using Ni/Al2O3-ZrO2 Catalyst

Directory of Open Access Journals (Sweden)

Adam Mahfud

2016-08-01

Full Text Available The catalytic hydrogenation/deoxygenation (H/D reaction was carried out using Ni/Al2O3-ZrO2 catalyst. The 10% (wt/wt of Ni were impregnated on Al2O3-ZrO2 (10NiAZ by wet impregnation method followed by calcination and reduction. X-Ray diffraction analysis showed that Nideposited on the surface, with specific surface areas (SBET was 48.616 m2/g. Catalyst performance were evaluated for H/D reaction over furfural-acetone condensation products, mixture of 2-(4-furyl-3-buten-2-on and 1,5-bis-(furan-2-yl-pentan-3-one. The reaction was carried out in a batch, performed at 150°C for 8 hours. The H/D reaction gave alkane derivatives C8 and C10 by hydrogenation process followed by ring opening of furan in 15.2% yield. While, oxygenated product C10-C13 were also detected in 17.2% yield. The increasing of pore volume of 10NiAZ might enhance catalyst activity over H/D reaction. The alkene C=C bond was easy to hydrogenated under this condition by the lower bond energy gap.

Interdiffusion between U(Mo,Pt) or U(Mo,Zr) and Al or Al A356 alloy

International Nuclear Information System (INIS)

Komar Varela, C.; Mirandou, M.; Arico, S.; Balart, S.; Gribaudo, L.

2009-01-01

Solid state reactions in chemical diffusion couples U-7 wt.%Mo-0.9 wt.%Pt/Al at 580 deg. C and U-7 wt.%Mo-0.9 wt.%Pt/Al A356 alloy, U-7 wt.%Mo-1 wt.%Zr/Al and U-7 wt.%Mo-1 wt.%Zr/Al A356 alloy at 550 deg. C were characterized. Results were obtained from optical and scanning electron microscopy, electron probe microanalysis and X-ray diffraction. The UAl 3, UAl 4 and Al 20 Mo 2 U phases were identified in the interaction layers of γU(Mo,Pt)/Al and γU(Mo,Zr)/Al diffusion couples. Al 43 Mo 4 U 6 ternary compound was also identified in γU(Mo,Zr)/Al due to the decomposition of γU(Mo,Zr) phase. The U(Al,Si) 3 and U 3 Si 5 phases were identified in the interaction layers of γU(Mo,Pt)/Al A356 and γU(Mo,Zr)/Al A356 diffusion couples. These phases are formed due to the migration of Si to the interaction layer. In the diffusion couple U(Mo,Zr)/Al A356, Zr 5 Al 3 phase was also identified in the interaction layer. The use of synchrotron radiation at Brazilian Synchrotron Light Laboratory (LNLS, CNPq, Campinas, Brazil) was necessary to achieve a complete crystallographic characterization.

Stability and electronic structure of Zr-based ternary metallic glasses and relevant compounds

International Nuclear Information System (INIS)

Hasegawa, M.; Soda, K.; Sato, H.; Suzuki, T.; Taketomi, T.; Takeuchi, T.; Kato, H.; Mizutani, U.

2007-01-01

The electronic structure of the Zr-based metallic glasses has been investigated by theoretical and experimental approaches. One approach is band calculations of the Zr 2 Ni (Zr 66.7 Ni 33.3 ) compound to investigate the electronic structure of the Zr 66.7 Ni 33.3 metallic glass (ΔT x = 0 K) of which the local atomic structure is similar to that of the Zr 2 Ni compound. The other is photoemission spectroscopy of the Zr 50 Cu 35 Al 15 bulk metallic glass (BMG) (ΔT x = 69 K). Here ΔT x = T x - T g where T x and T g are crystallization and glass transition temperature, respectively. Both results and previous ones on the Zr 55 Cu 30 Ni 5 Al 10 BMG indicate that there is a pseudogap at the Fermi level in the electronic structure of these Zr-based metallic glasses, independent of the value of the ΔT x . This implies that the pseudogap at the Fermi level is one of the factors that stabilize the glass phase of Zr-based metallic glasses

Espumas vítreas do sistema Li2O-ZrO2-SiO2-Al2O 3 produzidas pelo processo gelcasting Li2O-ZrO2-SiO2 -Al2O3 glass-ceramic foams produced by the gelcasting process

Directory of Open Access Journals (Sweden)

E. de Sousa

2009-06-01

Full Text Available Espumas vítreas do sistema Li2O-ZrO2-SiO2-Al2O 3 (LZSA foram produzidas pelo processo gelcasting, associado à aeração de suspensões cerâmicas, sem controle atmosférico. Por meio da adição de diferentes concentrações de agente espumante (Fongraminox foi possível obter espumas vítreas com densidade relativa variando entre uma estreita faixa (0,10-0,15. As espumas vítreas apresentaram resistência à compressão de 2,5-3,7 MPa, que correspondem a porosidade entre 85 e 89% e macroestrutra com poros aproximadamente esféricos e interconectados. Tais características tornam esses materiais atraentes para as seguintes aplicações tecnológicas: filtros para metais fundidos e gases quentes e, suportes catalíticos.Vitreous foams in the Li2O-ZrO2-SiO2-Al2O 3 (LZSA system were produced by the gelcasting process with aeration of ceramic suspensions and without atmospheric control. By the addition of different concentrations of foaming agent (Fongraminox it was possible to attain glass-ceramic foams in a narrow range of relative density (0.10-0.15. The glass-ceramic foams showed compressive strength of 2.5-3.7 MPa, which corresponds to porosity between 85-89%, and macrostructure with pores nearly spherical and interconnected, these characteristics make these materials attractive for the following applications technology: filters of molten metals and hot gas, and catalytic support.

Characterization of the interaction layer in diffusion couples U-Mo-Zr/Al and U-Mo-Zr/Al-A356 at 550 C degrees; Caracterizacion de la zona de interaccion en pares de difusion a 550 grados C U-Mo-Zr/Al y U-Mo-Zr/Al-A356

Energy Technology Data Exchange (ETDEWEB)

Komar Varela, Carolina; Arico, Sergio; Mirandou, Marcela; Balart, Silvia; Gribaudo, Luis [Comision Nacional de Energia Atomica, General San Martin (Argentina). Dept. de Materiales; com, carolinakomar@gmail

2007-07-01

Out-of-pile diffusion experiments were performed between U-7 wt.% Mo-1 wt.% Zr and Al or Al A356 (7,1 wt.% Si) at 550 C degrees. In this work morphological characterization and phase identification on both interaction layers are presented. They were carried out by the use of different techniques: optical and scanning electron microscopy, X-ray diffraction and WDS microanalysis. In the interaction layer U-7 wt.% Mo-1 wt.% Zr/Al, the phases UAl{sub 3}, UAl{sub 4}, Al{sub 20}Mo{sub 2}U and Al{sub 43}Mo{sub 4}U{sub 6} were identified. Similar results in the interaction layer of the U-7 % Mo/Al at 580 C degrees were previously obtained. In the interaction layer U-7 wt.% Mo-1 wt.% Zr/Al A356, the phases U(Al,Si){sub 3} with 25 at.% Si and Si{sub 5}U{sub 3} were identified. This last phase, with a higher Si concentration, was identified with X-ray diffraction synchrotron radiation performed at the National Synchrotron Light Laboratory, Campinas, Brazil. (author) [Spanish] Se realizaron experiencias fuera de reactor en pares de difusion quimica U-7 % Mo-1 % Zr/Al y U-7 % Mo-1 % Zr/Al A356. En este trabajo se presentan los resultados de la caracterizacion morfologica e identificacion de fases presentes en la zona de interaccion que se forma al ser sometidos a un tratamiento isotermico de 1,5 h a 550 grados C. Las tecnicas utilizadas fueron: microscopia optica y electronica de barrido, difraccion de rayos X y microanalisis cuantitativo por sonda electronica. En la zona de interaccion correspondiente al par U-7 % Mo-1 % Zr/Al se identificaron las fases UAl{sub 3}, UAl{sub 4}, Al{sub 20}Mo{sub 2}U y Al{sub 43}Mo{sub 4}U{sub 6}. Estas cuatro fases fueron identificadas en pares U-7 % Mo/Al a 580 grados C en trabajos anteriores. En la zona de interaccion correspondiente al par U-7 % Mo-1 % Zr/Al A356 se identificaron las fases U(Al,Si){sub 3} (con una concentracion de 25 %at.Si) y Si{sub 5}U{sub 3}. Este compuesto rico en Si solo pudo ser identificado mediante la utilizacion de

Partial oxidation of methane to syngas on Rh/Al{sub 2}O{sub 3} and Rh/Ce-ZrO{sub 2} catalysts

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Raquel L.; Bitencourt, Isabela G.; Passos, Fabio B., E-mail: fbpassos@vm.uff.br [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Dept. de Engenharia Quimica e Petroleo

2013-01-15

The partial oxidation of methane with {gamma}-Al{sub 2}O{sub 3}-, CeO{sub 2}-, ZrO{sub 2}- and Ce-ZrO{sub 2}-supported rhodium catalysts was investigated. DRIFTS (diffuse reflectance infrared spectroscopy) measurements of adsorbed CO showed the formation of different rhodium species on different supports, which influenced the dispersion of the metal. The effects of the metal dispersion, oxygen storage capacity on the activity of these catalysts for the partial oxidation of methane are discussed. (author)

Surface crystallization in a Li{sub 2}O-ZrO{sub 2}-SiO{sub 2}-Al{sub 2}O{sub 3} glass; Cristalizacao de superficie em vidro do sistema Li{sub 2}O-ZrO{sub 2}-SiO{sub 2}-Al{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Antonio Pedro Novaes de; Teixeira, Alexandre Henrique Bortolotto; Venturelli, Hugo Henrique, E-mail: bortolotto_teixeira@yahoo.com.br, E-mail: venturellihugo@gmail.com, E-mail: antonio.pedro@ufsc.br [Universidade Federal de Santa Catarina (VITROCER/PGMAT/UFSC), Florianopolis, SC (Brazil). Laboratorio de Materiais Vitroceramicos; Montedo, Oscar Rubem Klegues, E-mail: oscar.rkm@gmail.com [Universidade do Extremo Sul Catarinense (CERTEC/PPGCEM/UNESC), Criciuma, SC (Brazil). Grupo de Pesquisa em Ceramica Tecnica

2017-04-15

Growth kinetics of crystallized surface layer in a LZSA glass composition, 11.7Li{sub 2}O·12.6ZrO{sub 2}·68.6SiO{sub 2}·7.1Al{sub 2}O{sub 3} (wt%), was studied. For the production of the LZSA glass, it was used commercial raw materials (Li{sub 2}CO{sub 3}, ZrSiO{sub 4}, SiO{sub 2}, Al{sub 2}O{sub 3}) which were mixed and melted at 1550 °C for 120 min and then poured into a metallic mold. Samples of the obtained glass were cut and subjected to heat treatments at different temperatures (825 - 925 °C) and times (30 - 150 min) for formation and growth of crystalline layer. Cross-sections of the heat-treated samples were ground and polished such that images of the formed crystallized layers could be visualized and measured by microscopy. Results showed that it is possible to obtain LZSA glasses with crystallized layers formed by β-spodumene, zircon and lithium silicate, which present thicknesses between 13 and 665 μ and grow at rates varying from 0.4 to 4.8 μm/min in the studied temperature range. (author)

Zr O/sub 2/ and ZrSiO/sub 4/ addition influence in mechanical resistance and thermical shock of Al/sub 2/TiO/sub 5/

Energy Technology Data Exchange (ETDEWEB)

Marinho, P A; Longo, E; Varela, J A; Pandolfelli, V C

1985-01-01

The ZrO/sub 2/ and ZrSiO/sub 4/ addition on the Al/sub 2/O/sub 3/TiO/sub 2/ composition showed to be efficient on higher the mechanical and thermal shock resistence of the compound formed. The reactions that formed the phases and the influence of the ones on thermal and mechanical behaviour of the compound Al/sub 2/TiO/sub 5/ were discussed. (L.M.J.).

Atomic bonding and mechanical properties of Al-Mg-Zr-Sc alloy

Institute of Scientific and Technical Information of China (English)

高英俊; 班冬梅; 韩永剑; 钟夏平; 刘慧

2004-01-01

The valence electron structures of Al-Mg alloy with minor Sc and Zr were calculated according to the empirical electron theory(EET) in solid. The results show that because of the strong interaction of Al atom with Zr and Sc atom in melting during solidification, the Al3 Sc and Al3 (Sc1-xZrx) particles which act as heterogeneous nuclear are firstly crystallized in alloy to make grains refine. In progress of solidification, the Al-Sc, Al-Zr-Sc segregation regions are formed in solid solution matrix of Al-Mg alloy owing to the strong interaction of Al atom with Zr, Scatoms in bulk of alloy, so in the following homogenization treatment, the finer dispersed Al3 Sc and Al3 (Sc1-x Zrx) second-particles which are coherence with the matrix are precipitated in the segregation region. These finer second particles with the strong Al-Zr, Al-Sc covalent bonds can strengthen the covalent bonds in matrix of the alloy, and also enhance the hardness and strength of Al-Mg alloy. Those finer second-particles precipitated in interface of sub-grains can also strengthen the covalence bonds there, and effectively hinder the interface of sub-grains from migrating and restrain the sub-grains from growing, and cause better thermal stability of Al-Mg alloy.

Zr-(Cu,Ag)-Al bulk metallic glasses

International Nuclear Information System (INIS)

Jiang, Q.K.; Wang, X.D.; Nie, X.P.; Zhang, G.Q.; Ma, H.; Fecht, H.-J.; Bendnarcik, J.; Franz, H.; Liu, Y.G.; Cao, Q.P.; Jiang, J.Z.

2008-01-01

In this paper, we report the formation of a series Zr-(Cu,Ag)-Al bulk metallic glasses (BMGs) with diameters at least 20 mm and demonstrate the formation of about 25 g amorphous metallic ingots in a wide Zr-(Cu,Ag)-Al composition range using a conventional arc-melting machine. The origin of high glass-forming ability (GFA) of the Zr-(Cu,Ag)-Al alloy system has been investigated from the structural, thermodynamic and kinetic points of view. The high GFA of the Zr-(Cu,Ag)-Al system is attributed to denser local atomic packing and the smaller difference in Gibbs free energy between amorphous and crystalline phases. The thermal, mechanical and corrosion properties, as well as elastic constants for the newly developed Zr-(Cu,Ag)-Al BMGs, are also presented. These newly developed Ni-free Zr-(Cu,Ag)-Al BMGs exhibit excellent combined properties: strong GFA, high strength, high compressive plasticity, cheap and non-toxic raw materials and biocompatible property, as compared with other BMGs, leading to their potential industrial applications

EFFECT OF CUP AND BALL TYPES ON MECHANO-CHEMICAL SYNTHES IS OF Al2O3–TiC NANOCOMPOSITE POWDER

Directory of Open Access Journals (Sweden)

M. Zakeri

2012-07-01

Full Text Available Al2O3–TiC nanocomposite powder was successfully synthesized by ball milling TiO2, Al and graphite powders. Effects of cup and ball type, milling time and annealing were investigated. XRD was used to characterize milled and annealed powders. The morphological and microstructural evolutions were studied by SEM and TEM. Results showed that the formation of this composite begins after 20 h and completes after 35 h of milling with stainless steel cup and balls. In contrast, there is no reaction during milling (up to 80 h with ZrO2 cup and balls. Fe and ZrO2 were the major impurities introduced during milling with stainless steel and ZrO2 cups, respectively. The Fe impurity was removed by leaching in 3HCl·HNO3 solution for 4 days. Mean grain size less than 7 nm was achieved at the end of milling. In spite of grain growth, this composite maintained its nanocrystalline nature after annealing at 1000°C.

Structural evolution during fragile-to-strong transition in CuZr(Al) glass-forming liquids

DEFF Research Database (Denmark)

Zhou, C.; Hu, L.N.; Sun, Q.J.

2015-01-01

In the present work, we show experimental evidence for the dynamic fragile-to-strong (F-S) transition in a series of CuZr(Al) glass-forming liquids (GFLs). A detailed analysis of the dynamics of 98 glass-forming liquids indicates that the F-S transition occurs around Tf-s ≈ 1.36 Tg. Using...... the hyperquenching-annealing-x-ray scattering approach, we have observed a three-stage evolution pattern of medium-range ordering (MRO) structures during the F-S transition, indicating a dramatic change of the MRO clusters around Tf-s upon cooling. The F-S transition in CuZr(Al) GFLs is attributed to the competition...... among the MRO clusters composed of different locally ordering configurations. A phenomenological scenario has been proposed to explain the structural evolution from the fragile to the strong phase in the CuZr(Al) GFLs....

Investigation of the structure and properties of the titanium alloy of the Ti-Al-Mo-V-Fe-Cu-Zr-Sn system

International Nuclear Information System (INIS)

Moiseev, V.N.; Dolzhanskij, Yu.M.; Zakharov, Yu.I.; Znamenskaya, E.V.

1979-01-01

The alloys of martensitic type in the Ti-Al-Mo-V-Fe-Cu-Zr-Sn system after heat treatment are investigated. To determine the composition of the titanium alloy methods of mathematical planning of the experiment are applied. Results of mechanical tests of the alloys are presented, as well as coefficients of models for the properties, calculated according to these data. The investigation establishes the composition of a high-strength titanium alloy of a martensitic type, containing 4.5-60 % Al, 2.0-4.0 % Mo, 0.5-1.9 % V, 0.3-1.5 % Fe, 0.3-1.5 % Cu, 1.5-3.0 % Sn, 2.0-4.0 % Zr. The semiproducts, produced by deformation in β-field, after heat treatment have an ultimate strength >=120 kg/mm 2 , satisfactory ductility and reliability. The alloy possesses rather a high heat resistance and can be operated at 400-500 deg C

Structural Origin of the Enhanced Glass-Forming Ability Induced by Microalloying Y in the ZrCuAl Alloy

Directory of Open Access Journals (Sweden)

Gu-Qing Guo

2016-03-01

Full Text Available In this work, the structural origin of the enhanced glass-forming ability induced by microalloying Y in a ZrCuAl multicomponent system is studied by performing synchrotron radiation experiments combined with simulations. It is revealed that the addition of Y leads to the optimization of local structures, including: (1 more Zr-centered and Y-centered icosahedral-like clusters occur in the microstructure; (2 the atomic packing efficiency inside clusters and the regularity of clusters are both enhanced. These structural optimizations help to stabilize the amorphous structure in the ZrCuAlY system, and lead to a high glass-forming ability (GFA. The present work provides an understanding of GFAs in multicomponent alloys and will shed light on the development of more metallic glasses with high GFAs.

Zr-ZrO sub 2 cermet solar coatings designed by modelling calculations and deposited by dc magnetron sputtering

CERN Document Server

Zhang Qi Chu; Lee, K D; Shen, Y G

2003-01-01

High solar performance Zr-ZrO sub 2 cermet solar coatings were designed using a numerical computer model and deposited experimentally. The layer thickness and Zr metal volume fraction for the Zr-ZrO sub 2 cermet solar selective coatings on a Zr or Al reflector with a surface ZrO sub 2 or Al sub 2 O sub 3 anti-reflection layer were optimized to achieve maximum photo-thermal conversion efficiency at 80 deg. C under concentration factors of 1-20 using the downhill simplex method in multi-dimensions in the numerical calculation. The dielectric function and the complex refractive index of Zr-ZrO sub 2 cermet materials were calculated using Sheng's approximation. Optimization calculations show that Al sub 2 O sub 3 /Zr-ZrO sub 2 /Al solar coatings with two cermet layers and three cermet layers have nearly identical solar absorptance, emittance and photo-thermal conversion efficiency that are much better than those for films with one cermet layer. The optimized Al sub 2 O sub 3 /Zr-ZrO sub 2 /Al solar coating film w...

Voltage linearity modulation and polarity dependent conduction in metal-insulator-metal capacitors with atomic-layer-deposited Al{sub 2}O{sub 3}/ZrO{sub 2}/SiO{sub 2} nano-stacks

Energy Technology Data Exchange (ETDEWEB)

Zhu, Bao; Liu, Wen-Jun; Wei, Lei; Zhang, David Wei; Jiang, Anquan; Ding, Shi-Jin, E-mail: sjding@fudan.edu.cn [State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433 (China)

2015-07-07

Excellent voltage linearity of metal-insulator-metal (MIM) capacitors is highly required for next generation radio frequency integration circuits. In this work, employing atomic layer deposition technique, we demonstrated how the voltage linearity of MIM capacitors was modulated by adding different thickness of SiO{sub 2} layer to the nano-stack of Al{sub 2}O{sub 3}/ZrO{sub 2}. It was found that the quadratic voltage coefficient of capacitance (α) can be effectively reduced from 1279 to −75 ppm/V{sup 2} with increasing the thickness of SiO{sub 2} from zero to 4 nm, which is more powerful than increasing the thickness of ZrO{sub 2} in the Al{sub 2}O{sub 3}/ZrO{sub 2} stack. This is attributed to counteraction between the positive α for Al{sub 2}O{sub 3}/ZrO{sub 2} and the negative one for SiO{sub 2} in the MIM capacitors with Al{sub 2}O{sub 3}/ZrO{sub 2}/SiO{sub 2} stacks. Interestingly, voltage-polarity dependent conduction behaviors in the MIM capacitors were observed. For electron bottom-injection, the addition of SiO{sub 2} obviously suppressed the leakage current; however, it abnormally increased the leakage current for electron top-injection. These are ascribed to the co-existence of shallow and deep traps in ZrO{sub 2}, and the former is in favor of the field-assisted tunnelling conduction and the latter contributes to the trap-assisted tunnelling process. The above findings will be beneficial to device design and process optimization for high performance MIM capacitors.

Performance improvement of charge-trap memory by using a stacked Zr_0_._4_6Si_0_._5_4O_2/Al_2O_3 charge-trapping layer

International Nuclear Information System (INIS)

Tang, Zhenjie; Hu, Dan; Zhang, Xiwei; Zhao, Yage; Li, Rong

2016-01-01

The postdeposition annealing (PDA)-treated charge-trap flash memory capacitor with stacked Zr_0_._4_6Si_0_._5_4O_2/Al_2O_3 charge-trapping layer flanked by a SiO_2 tunneling oxide and an Al_2O_3 blocking oxide was fabricated and investigated. It is observed that the memory capacitor exhibits prominent memory characteristics with large memory windows 12.8 V in a ±10 V gate sweeping voltage range, faster program/erase speed, and good data-retention characteristics even at 125 C compared to a single charge-trapping layer (Zr_0_._4_6Si_0_._5_4O_2, Zr_0_._7_9Si_0_._2_1O_2, and Zr_0_._4_6Al_1_._0_8O_2_._5_4). The quantum wells and introduced interfacial traps of the stacked trapping layer regulate the storage and loss behavior of charges, and jointly contribute to the improved memory characteristics. Hence, the memory capacitor with a stacked trapping layer is a promising candidate in future nonvolatile charge-trap memory device design and application. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Optical and structural characterization of Ge clusters embedded in ZrO2

OpenAIRE

Agocs, E; Zolnai, Z.; Rossall, A. K.; Van den Berg, Jakob; Fodor, B.; Lehninger, D.; Khomenkova, L.; Ponomaryov, S.; Gudymenko, O.; Yukhymchuk, V.; Kalas, B.; Heitmann, J.; Petrik, P.

2017-01-01

The change of optical and structural properties of Ge nanoclusters in ZrO2 matrix have been investigated by spectroscopic ellipsometry versus annealing temperatures. Radio-frequency top-down magnetron sputtering approach was used to produce the samples of different types, i.e. single-layers of pure Ge, pure ZrO2 and Ge-rich-ZrO2 as well as multi-layers stacked of 40 periods of 5-nm-Ge-rich-ZrO2 layers alternated by 5-nm-ZrO2 ones. Germanium nanoclusters in ZrO2 host were formed by rapid-therm...

Espumas vítreas do sistema Li2O-ZrO2-SiO2-Al2O 3 produzidas pelo processo gelcasting Li2O-ZrO2-SiO2 -Al2O3 glass-ceramic foams produced by the gelcasting process

OpenAIRE

E. de Sousa; C. R. Rambo; F. S. Ortega; A. P. N. de Oliveira; V. C. Pandolfelli

2009-01-01

Espumas vítreas do sistema Li2O-ZrO2-SiO2-Al2O 3 (LZSA) foram produzidas pelo processo gelcasting, associado à aeração de suspensões cerâmicas, sem controle atmosférico. Por meio da adição de diferentes concentrações de agente espumante (Fongraminox) foi possível obter espumas vítreas com densidade relativa variando entre uma estreita faixa (0,10-0,15). As espumas vítreas apresentaram resistência à compressão de 2,5-3,7 MPa, que correspondem a porosidade entre 85 e 89% e macroestrutra com por...

Zr-Cu-Ni-Al bulk metallic glasses with superhigh glass-forming ability

International Nuclear Information System (INIS)

Sun, Y.J.; Qu, D.D.; Huang, Y.J.; Liss, K.-D.; Wei, X.S.; Xing, D.W.; Shen, J.

2009-01-01

Zr-Cu-Ni-Al quaternary amorphous alloy compositions with varying glass-forming ability are developed by an efficient method of proportional mixing of binary eutectics. The critical diameter of the glassy sample is improved from 6 mm for Zr 53 Cu 18.7 Ni 12 Al 16.3 to 14 mm for Zr 50.7 Cu 28 Ni 9 Al 12.3 by straightforwardly adjusting the eutectic unit's coefficients. The drastic improvement in GFA is attributed to balancing the chemical affinities of the Zr, Cu, Ni and Al components in the melt prior to solidification which makes the precipitation of competing crystalline phases more difficult. As the glass-forming ability increases, the concentration of Cu in the alloys exhibits a same trend. Based on synchrotron radiation high-energy X-ray diffraction analysis and Miracle's structural model, it is envisioned that the substitution of additional Cu atoms for Zr atoms in the investigated alloys stabilizes the efficient cluster packing structure of the amorphous alloys, leading to the pronounced increase in their glass-forming ability

Nanoparticle dispersion effect of laser-surface melting in ZrB{sub 2p}/6061Al composites

Energy Technology Data Exchange (ETDEWEB)

Zeng, Yida; Chao, Yuhjin; Luo, Zhen, E-mail: lz-tju@163.com [Tianjin University, School of Material Science and Engineering (China); Huang, Yongxian [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology (China)

2017-04-15

Zirconium diboride (ZrB{sub 2p}, 15 vol%)/6061 aluminum (Al) composites were fabricated via in situ reaction. The existence, morphologies, and dispersion degree of the in situ ZrB{sub 2} particles with size from tens to hundreds of nanometers were studied by X-ray diffractometry, energy-dispersive X-ray spectroscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. As the particle-settlement effect becomes dominant during the composite fabrication process, ZrB{sub 2} nanoparticles agglomerate to a certain extent in some areas of the as-cast composites. A laser-surface melting (LSM) strategy was applied to disperse agglomerated ZrB{sub 2} nanoparticles in as-cast composites, and the ZrB{sub 2} nanoparticle dispersion is affected visibly by LSM. After LSM, nanoparticles tend to distribute along the grain boundary. Particle clusters were dispersed in an explosive orientation and the particle diffusion distance varied in terms of its radius and melt-viscosity vicinity. High-resolution transmission electron microscopy showed the existence of a subgrain structure near the ZrB{sub 2}–Al interface after LSM. This may increase the yield strength when a dislocation tangle forms.

Effects of homogenization on microstructures and properties of a new type Al-Mg-Mn-Zr-Ti-Er alloy

International Nuclear Information System (INIS)

He, L.Z.; Li, X.H.; Liu, X.T.; Wang, X.J.; Zhang, H.T.; Cui, J.Z.

2010-01-01

Research highlights: These new type alloys are very potential for increased use in aerospace and automobile industries. However, most of published reports have focused on the effects of Cu, Sc, Zr, Ag, rare metals and Si additions, Portevin-LeChatelier effect, corrosion properties, friction stir welding and superplasticity in 5000-series aluminum alloy, few investigated on Er and stepped homogenization on the precipitation of dispersoids in Al-Mg-Mn alloy. The purpose of this work was to study the effects of Er and homogenization treatment on mechanical properties and microstructural evolution in new type Al-Mg-Mn-Er alloy. - Abstract: Microstructural evolutions and mechanical properties of Al-Mg-Mn-Zr-Ti-Er alloy after homogenization were investigated in detail by optical microscope (OM), scanning electronic microscope (SEM), transmission electronic microscope (TEM), energy dispersive spectrum (EDS) and tensile test. A maximum tensile strength is obtained when the alloy homogenized at 510 deg. C for 16 h. With increasing preheating temperature (200-400 deg. C), the strength of the alloy finial homogenized at 490 deg. C for 16 h increases. When the preheating temperature is ≥300 deg. C, the strengths of the two-step homogenized alloys are higher than those of the single homogenized alloys. The preheating stage plays an important role in the microstructures and properties of the final homogenized alloy. Many fine (Mn,Fe)Al 6 precipitates when the preheating temperature is 400 deg. C. ErAl 3 phase cannot be observed during preheating stage. Plenty of fine (Mn,Fe)Al 6 and ErAl 3 precipitate in finial homogenized alloy when the preheating temperature is ≥300 deg. C. The Al-Mg-Mn-Zr-Ti-Er alloy is effectively strengthened by substructure and dispersoids of (Mn,Fe)Al 6 and ErAl 3 .

Thermoluminescence induced by UV radiation in ZrO2-La2O3 and ZrO2-CeO2 mixed systems

International Nuclear Information System (INIS)

Estrada G, R.; Salas C, P.; Mendoza A, D.; Gonzalez, P.R.

2002-01-01

Nowadays, the development of catalytic materials by means of pure or mixed oxides mainly as TiO 2 , Al 2 O 3 , ZrO 2 , La 2 O 3 and CeO 2 used as support or active phases, are widely used in oxidation-reduction reactions in the chemical industry and in petroleum refining processes. the cerium and lanthanum oxides in zircon, have been studied recently in processes for reduction of pollutant gases (SO x , NO x , etc.). They result very interesting for resolving the problems of environmental pollution. Moreover, it has been observed that some of these materials are highly sensitive to ultraviolet radiation (UV), characteristic that can be took in advantage for detecting this type of radiation. In this work the preliminary obtained results on the thermoluminescent response (Tl) induced by the UV radiation in ZrO 2 -La 2 O 3 and ZrO 2 -CeO 2 mixed systems obtained by the sol-gel method are presented. The results show that the first system has a high sensitivity to UV radiation with a Tl curve composed by three peaks, two ones of greater intensity located in 70 and 140 Centigrade degrees. Likewise it was observed that for both materials, the peak located at low temperature is fadeout in few minutes after irradiation, while that the second one peak presented very good stability, resulting promising for dosimetric applications in UV radiation fields. (Author)

Phase transitions in complex oxide systems based on Al{sub 2}O{sub 3} and ZrO{sub 2}; Przemiany fazowe w zlozonych ukladach tlenkowych na bazie Al{sub 2}O{sub 3} i ZrO{sub 2} zachodzace w procesach z szybkozmiennym dzialaniem temperatury

Energy Technology Data Exchange (ETDEWEB)

Gorski, L [Institute of Atomic Energy, Otwock-Swierk (Poland)

1999-07-01

Different compositions of materials based on Al{sub 2}O{sub 3} and ZrO{sub 2} and protective coatings sprayed from them working in the high temperature region are studied. There are especially thermal barrier coatings of increasing resistance to thermal shocks and conditions of corrosion and erosion caused by the hot gases and liquids. Such conditions are encountered in many technical branches among others in jet and Diesel engines. These coatings are deposited by the plasma spraying process and their resistance to thermal shocks is studied on special experimental arrangement in the conditions near to coatings applications. Both above processes are characterized by a short time temperature action with subsequent high cooling rate, which may cause phase transitions other than in the conditions of thermodynamical equilibrium. These transitions are studied by X-ray diffraction analysis methods. The microstructure changes accompanied to phase transitions are determined by light microscopy and scanning electron microscopy methods. The cases of coating degradation caused by thermal shocks have been observed. The highest resistance to thermal fatigue conditions (up to thermal shocks) show coatings based on Al{sub 2}O{sub 3} containing aluminium titanate and coatings based on ZrO{sub 2} stabilised by 7-8% of Y{sub 2}O{sub 3}. (author)

The application of DTA and TG methods to investigate the non-crystalline hydration products of CaAl2O4 and Ca7ZrAl6O18 compounds

International Nuclear Information System (INIS)

Szczerba, Jacek; Madej, Dominika; Śnieżek, Edyta; Prorok, Ryszard

2013-01-01

Highlights: ► Hydrates, i.e. CAH 10 , C 2 AH 8 , C 3 AH 6 and C 4 AH 19 are formed during hydration of CaAl 2 O 4 and Ca 7 ZrAl 6 O 18 . ► Hydrated CaAl 2 O 4 and Ca 7 ZrAl 6 O 18 compounds were investigated by X-ray diffraction, SEM/EDS and thermal analysis. ► The hydration reaction proceeds as consumes the unreacted core of the CaAl 2 O 4 and Ca 7 ZrAl 6 O 18 grain. - Abstract: The hydration products and thermal decomposition mechanism of hydrated CaAl 2 O 4 and Ca 7 ZrAl 6 O 18 compounds were investigated by X-ray diffraction, SEM/EDS and thermal analysis. The processes of crystal hydrate nucleation and precipitation were preceded by the evolution of the X-ray amorphous phase during the first 24 h of hydration. DTA–TGA–EGA techniques allowed the study of the detailed decomposition and identification of intermediate and stable to be performed. The differential thermal analysis (DTA) curves of hydrated CaAl 2 O 4 and Ca 7 ZrAl 6 O 18 compounds show five similar endothermic peaks due to crystal water desorption. According to the quantitative TGA–EGA analyses performed on hydrated CaAl 2 O 4 and Ca 7 ZrAl 6 O 18 compounds, it was found that C 2 AH 8 , C 3 AH 6 and Al(OH) 3 phases are the main hydration products of CaAl 2 O 4 . Under the same laboratory conditions, the hydration of Ca 7 ZrAl 6 O 18 proceeds with the formation of mainly CAH 10 and AH 3 -gel phases. We provide the original illustrations of the hydrate crystals formation via amorphous phases

Study of spinodal decomposition and formation of nc-Al2O3/ZrO2 nanocomposites by combined ab initio density functional theory and thermodynamic modeling

International Nuclear Information System (INIS)

Sheng, S.H.; Zhang, R.F.; Veprek, S.

2011-01-01

Using ab initio density functional theory, the equilibrium properties, such as the total energy, the molar volume, the bulk modulus and its first derivative, as well as the formation enthalpy of monoclinic ZrO 2 and hexagonal α-Al 2 O 3 phases, were calculated and compared with the published theoretical and experimental data. Based on the good agreement of these data, we calculated the lattice instabilities of hypothetical binary hexagonal Zr 2 O 3 and monoclinic AlO 2 , and the interaction parameters of ternary Zr 1-x Al x O y solid solutions. The binodal and spinodal diagrams were then constructed to predict the possibility of the formation of oxide-based nanocomposites which may display hardness enhancement above that of the solid solutions. It is shown that exponential dependence of the interaction parameter on temperature yields the most reliable results. The system should undergo spinodal phase segregation within the composition range that is relevant for the formation of hard or superhard nanocomposites with high thermal and oxidation stability, which are important for their applications.

X-ray photoelectron spectroscopy of nano-multilayered Zr-O/Al-O coatings deposited by cathodic vacuum arc plasma

International Nuclear Information System (INIS)

Zhitomirsky, V.N.; Kim, S.K.; Burstein, L.; Boxman, R.L.

2010-01-01

Nano-multilayered Zr-O/Al-O coatings with alternating Zr-O and Al-O layers having a bi-layer period of 6-7 nm and total coating thickness of 1.0-1.2 μm were deposited using a cathodic vacuum arc plasma process on rotating Si substrates. Plasmas generated from two cathodes, Zr and Al, were deposited simultaneously in a mixture of Ar and O 2 background gases. The Zr-O/Al-O coatings, as well as bulk ZrO 2 and Al 2 O 3 reference samples, were studied using X-ray photoelectron spectroscopy (XPS). The XPS spectra were analyzed on the surface and after sputtering with a 4 kV Ar + ion gun. High resolution angle resolved spectra were obtained at three take-off angles: 15 o , 45 o and 75 o relative to the sample surface. It was shown that preferential sputtering of oxygen took place during XPS of bulk reference ZrO 2 samples, producing ZrO and free Zr along with ZrO 2 in the XPS spectra. In contrast, no preferential sputtering was observed with Al 2 O 3 reference samples. The Zr-O/Al-O coatings contained a large amount of free metals along with their oxides. Free Zr and Al were observed in the coating spectra both before and after sputtering, and thus cannot be due solely to preferential sputtering. Transmission electron microscopy revealed that the Zr-O/Al-O coatings had a nano-multilayered structure with well distinguished alternating layers. However, both of the alternating layers of the coating contained of a mixture of aluminum and zirconium oxides and free Al and Zr metals. The concentration of Zr and Al changed periodically with distance normal to the coating surface: the Zr maximum coincided with the Al minimum and vice versa. However the concentration of Zr in both alternating layers was significantly larger than that of Al. Despite the large free metal concentration, the Knoop hardness, 21.5 GPa, was relatively high, which might be attributed to super-lattice formation or formation of a metal-oxide nanocomposite within the layers.

Optical and structural characterization of Ge clusters embedded in ZrO2

Science.gov (United States)

Agocs, E.; Zolnai, Z.; Rossall, A. K.; van den Berg, J. A.; Fodor, B.; Lehninger, D.; Khomenkova, L.; Ponomaryov, S.; Gudymenko, O.; Yukhymchuk, V.; Kalas, B.; Heitmann, J.; Petrik, P.

2017-11-01

The change of optical and structural properties of Ge nanoclusters in ZrO2 matrix have been investigated by spectroscopic ellipsometry versus annealing temperatures. Radio-frequency top-down magnetron sputtering approach was used to produce the samples of different types, i.e. single-layers of pure Ge, pure ZrO2 and Ge-rich-ZrO2 as well as multi-layers stacked of 40 periods of 5-nm-Ge-rich-ZrO2 layers alternated by 5-nm-ZrO2 ones. Germanium nanoclusters in ZrO2 host were formed by rapid-thermal annealing at 600-800 °C during 30 s in nitrogen atmosphere. Reference optical properties for pure ZrO2 and pure Ge have been extracted using single-layer samples. As-deposited multi-layer structures can be perfectly modeled using the effective medium theory. However, annealed multi-layers demonstrated a significant diffusion of elements that was confirmed by medium energy ion scattering measurements. This fact prevents fitting of such annealed structure either by homogeneous or by periodic multi-layer models.

Preparation, structural characterization, and enhanced electrical conductivity of pyrochlore-type (Sm{sub 1-x}Eu{sub x}){sub 2}Zr{sub 2}O{sub 7} ceramics

Energy Technology Data Exchange (ETDEWEB)

Xia, X.L. [Institute for Advanced Ceramics, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin (China); Institute of Oceanography Instruments, Shandong Academy of Science, Chinese National Engineering Research Center for Marine Monitoring Equipment, Qingdao (China); Liu, Z.G.; Ouyang, J.H. [Institute for Advanced Ceramics, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin (China); Zheng, Y. [Institute of Oceanography Instruments, Shandong Academy of Science, Chinese National Engineering Research Center for Marine Monitoring Equipment, Qingdao (China)

2012-08-15

(Sm{sub 1-x}Eu{sub x}){sub 2}Zr{sub 2}O{sub 7} (0 {<=} x {<=} 1.0) samples are prepared by solid state reaction method using Sm{sub 2}O{sub 3}, Eu{sub 2}O{sub 3}, and ZrO{sub 2} as starting materials. The phase composition and microstructure of (Sm{sub 1-x}Eu{sub x}){sub 2}Zr{sub 2}O{sub 7} ceramics are investigated by X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM) coupled with selected area electron diffraction and Raman spectroscopy. XRD and TEM show that all the samples exhibit a single pyrochlore-type structure. HRTEM observation indicates that the whole grain interior of Sm{sub 2}Zr{sub 2}O{sub 7} ceramic is a perfect crystal free of any dislocation. Raman spectroscopy reveals that the degree of structural disorder of (Sm{sub 1-x}Eu{sub x}){sub 2}Zr{sub 2}O{sub 7} ceramics increases gradually with increasing Eu content. The electrical conductivity of (Sm{sub 1-x}Eu{sub x}){sub 2}Zr{sub 2}O{sub 7} ceramics is investigated by impedance spectroscopy in the air and hydrogen atmospheres, respectively. The electrical conductivity of (Sm{sub 1-x}Eu{sub x}){sub 2}Zr{sub 2}O{sub 7} ceramics increases with increasing Eu content at identical temperature levels. Both the activation energy E{sub g} and the pre-exponential factor {sigma}{sub 0g} for the grain conductivity gradually increase with increasing Eu content. As the ionic conductivity shows no obvious change in both air and hydrogen atmospheres, the conduction of (Sm{sub 1-x}Eu{sub x}){sub 2}Zr{sub 2}O{sub 7} is purely ionic with negligible electronic conduction. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Ferroelectric Polarization-Modulated Interfacial Fine Structures Involving Two-Dimensional Electron Gases in Pb(Zr,Ti)O3/LaAlO3/SrTiO3 Heterostructures.

Science.gov (United States)

Wang, Shuangbao; Bai, Yuhang; Xie, Lin; Li, Chen; Key, Julian D; Wu, Di; Wang, Peng; Pan, Xiaoqing

2018-01-10

Interfacial fine structures of bare LaAlO 3 /SrTiO 3 (LAO/STO) heterostructures are compared with those of LAO/STO heterostructures capped with upward-polarized Pb(Zr 0.1 ,Ti 0.9 )O 3 (PZT up ) or downward-polarized Pb(Zr 0.5 ,Ti 0.5 )O 3 (PZT down ) overlayers by aberration-corrected scanning transmission electron microscopy experiments. By combining the acquired electron energy-loss spectroscopy mapping, we are able to directly observe electron transfer from Ti 4+ to Ti 3+ and ionic displacements at the interface of bare LAO/STO and PZT down /LAO/STO heterostructure unit cell by unit cell. No evidence of Ti 3+ is observed at the interface of the PZT up /LAO/STO samples. Furthermore, the confinement of the two-dimensional electron gas (2DEG) at the interface is determined by atomic-column spatial resolution. Compared with the bare LAO/STO interface, the 2DEG density at the LAO/STO interface is enhanced or depressed by the PZT down or PZT up overlayer, respectively. Our microscopy studies shed light on the mechanism of ferroelectric modulation of interfacial transport at polar/nonpolar oxide heterointerfaces, which may facilitate applications of these materials as nonvolatile memory.

Amorphous phase formation in the Cu_3_6Zr_5_9A_l_5 and Cu_4_8Zr_4_3A_l_9 ternary alloys studied by molecular dynamics

International Nuclear Information System (INIS)

Aliaga, L.C.R.; Schimidt, C.S.; Lima, L.V.; Domingues, G.M.B.; Bastos, I.N.

2016-01-01

Amorphous alloys presents better mechanical and physical properties than its crystalline counterparts. However, there is a scarce understanding on structure - properties relationship in this class of materials. This paper presents the results of the molecular dynamics application to obtain an atomistic description of melting, solidification and the glass forming ability in the ternary Cu_3_6Zr_5_9A_l_5 and Cu_4_8Zr_4_3A_l_9 alloys. In the study we used the EAM potential and different cooling rates, β = 0.1, 1 and 100 K/ps to form the amorphous phase in a system consisting of 32,000 atoms by using the free code LAMMPS. The solidus and liquidus temperatures, on a heating rate of the 5 K/ps, were obtained. Also, on the cooling down step, it was observed that the glass transition temperature (T_g) decreases as cooling rate increases. The structural evolution was analyzed through the radial distribution functions and Voronoi polyhedra. Furthermore, it was determined the evolution of viscosity upper T_g, as well as the fragility (m) parameter for each amorphous alloy. The thermal parameters of the simulation obtained are compared with those of the experiments. (author)

Synthesis and hydration behavior of calcium zirconium aluminate (Ca7ZrAl6O18) cement

International Nuclear Information System (INIS)

Kang, Eun-Hee; Yoo, Jun-Sang; Kim, Bo-Hye; Choi, Sung-Woo; Hong, Seong-Hyeon

2014-01-01

Calcium zirconium aluminate (Ca 7 ZrAl 6 O 18 ) cements were prepared by solid state reaction and polymeric precursor methods, and their phase evolution, morphology, and hydration behavior were investigated. In polymeric precursor method, a nearly single phase Ca 7 ZrAl 6 O 18 was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO 3 coexisted with Ca 7 ZrAl 6 O 18 even at higher temperature (1400 °C). Unexpectedly, Ca 7 ZrAl 6 O 18 synthesized by polymeric precursor process was the large-sized and rough-shaped powder. The planetary ball milling was employed to control the particle size and shape. The hydration behavior of Ca 7 ZrAl 6 O 18 was similar to that of Ca 3 Al 2 O 6 (C3A), but the hydration products were Ca 3 Al 2 O 6 ·6H 2 O (C3AH6) and several intermediate products. Thus, Zr (or ZrO 2 ) stabilized the intermediate hydration products of C3A

Influence of aluminium incorporation on the structure of ZrN films deposited at low temperatures

International Nuclear Information System (INIS)

Araiza, J J; Sanchez, O

2009-01-01

We have studied the influence of Al incorporation in the crystalline structure of ZrN thin films deposited by dc magnetron sputtering at low temperature. The amount of aluminium in the films depends directly on the power applied to the aluminium cathode during the deposition. Energy dispersive x-ray analysis and x-ray diffraction (XRD) were used to obtain the chemical composition and crystalline structure of the films, respectively. When Al atoms are incorporated into the ZrN coatings, the strong ZrN (2 0 0) orientation is modified by a combination of other ones such as ZrN (1 1 1), Zr 3 N 4 (2 1 1) and hexagonal AlN (1 0 0) as detected from the XRD spectra for high aluminium concentrations. Fourier-transform infrared spectroscopy allowed us to identify oxides and nitrides, ZrO, AlO and AlN, incorporated into the deposited films. The effect of a bias voltage applied to the substrate has also been investigated and related to the changes in the microstructure and in the nanohardness values of the ZrAlN films.

Non-stoichiometric mullites from Al2O3-SiO2-ZrO2 amorphous materials by rapid quenching

International Nuclear Information System (INIS)

Yoshimura, M.; Hanaue, Y.; Somiya, S.

1990-01-01

In order to study the formation of zirconia dispersed mullite ceramics from homogeneous starting materials hot-pressing and heat-treatments have been carried out for rapidly quenched amorphous materials with 0 to 20 wt% ZrO 2 mullite compositions. These amorphous materials crystallized directly to mullite for 0-10 wt% ZrO 2 samples or mullite + t-ZrO 2 for 20 wt% ZrO 2 at about 970 degrees C. An A1 2 O 3 - rich composition (82 wt% A1 2 O 3 ) and also a significant solid solubility of ZrO 2 (>10 wt%) were estimated for these mullites by XRD studies. Amorphous speres of 10 nm which were considered to be SiO 2 - rich phase were produced by a phase separation in mullite grains

Effects of Fabrication Parameters on Interface of Zirconia and Ti-6Al-4V Joints Using Zr55Cu30Al10Ni5 Amorphous Filler

Science.gov (United States)

Liu, Yuhua; Hu, Jiandong; Shen, Ping; Guo, Zuoxing; Liu, Huijie

2013-09-01

ZrO2 was brazed to Ti-6Al-4V using a Zr55Cu30Al10Ni5 (at.%) amorphous filler in a high vacuum at 1173-1273 K. The influences of brazing temperature, holding time, and cooling rate on the microstructure and shear strength of the joints were investigated. The interfacial microstructures can be characterized as ZrO2/ZrO2- x + TiO/(Zr,Ti)2(Cu,Ni)/(Zr,Ti)2(Cu,Ni,Al)/acicular Widmanstäten structure/Ti-6Al-4V. With the increase in the brazing temperature, both the thickness of the ZrO2- x + TiO layer and the content of the (Zr,Ti)2(Cu,Ni) phase decreased. However, the acicular Widmanstäten structure gradually increased. With the increase in the holding time, the (Zr,Ti)2(Cu,Ni) phase decreased, and the thickness of the (Zr,Ti)2(Cu,Ni) + (Zr,Ti)2(Cu,Ni,Al) layer decreased. In addition, cracks formed adjacent to the ZrO2 side under rapid cooling. The microstructures produced under various fabrication parameters directly influence the shear strength of the joints. When ZrO2 and Ti-6Al-4V couples were brazed at 1173 K for 10 min and then cooled at a rate of 5 K/min, the maximum shear strength of 95 MPa was obtained.

Thermal expansion of phosphates with the NaZr2(PO4)3 structure containing lanthanides and zirconium: R0.33Zr2(PO4)3 (R = Nd, Eu, Er) and Er0.33(1–x) Zr0.25xZr2(PO4)3

International Nuclear Information System (INIS)

Volgutov, V. Yu.; Orlova, A. I.

2015-01-01

Phosphates R 0.33 Zr 2 (PO 4 ) 3 (R = Nd, Eu, or Er) and Er 0.33(1–x) Zr 0.25 Zr 2 (PO 4 ) 3 (x = 0, 0.25, 0.5, 0.75, 1.0) of the NaZr 2 (PO 4 ) 3 family have been synthesized and investigated by high-temperature X-ray diffraction. The crystallochemical approach is used to obtain compounds with expected small and controllable thermal-expansion parameters. Phosphates with close-to-zero thermal-expansion parameters, including those with low thermal-expansion anisotropy, have been obtained: Nd 0.33 Zr 2 (PO 4 ) 3 with α a =–2.21 × 10 −6 °C −1 , α c = 0.81 × 10 −6 °C −1 , and Δα = 3.02 × 10 −6 °C –1 and Er 0.08 Zr 0.19 Zr 2 (PO 4 ) 3 with α a =–1.86 × 10 −6 °C −1 , α c = 1.73 × 10 −6 °C −1 , and Δα = 3.58 × 10 −6 °C −1

Raman spectroscopy used for structural investigations of anodically formed ZrO2

International Nuclear Information System (INIS)

Koneska, Zagorka; Arsova, Irena

2003-01-01

The structure of the oxide formed on Zr(99% + Hf) with anodic oxidation at different potentials in 1 mol/dm 3 H 3 PO 4 and 2 mol/dm 3 KOH solutions were investigated using Raman spectroscopy. Normally the anodic oxides of Zr form only crystals. Under certain circumstances, amorphous anodic ZrO 2 can be observed. Amorphous phase is observed for the anodically formed zirconium oxides in H 3 PO 4 . The oxide formed in KOH at potential of 80 V, where sparks appears on the Zr electrode showed crystalline structure. (Original)

Cation mobility in NASICON compounds Li1-xZr2-xNbx(PO4)3 and Li1+xZr2-xScx(PO4)3

International Nuclear Information System (INIS)

Stenina, I.A.; Yaroslavtsev, A.B.; Aliev, A.D.; Antipov, E.V.; Velikodnyj, Yu.A.; Rebrov, A.I.

2002-01-01

Compounds featuring NASICON structure of the composition Li 1-x Zr 2-x Nb x (PO 4 ) 3 and Li 1+x Zr 2-x Sc x (PO 4 ) 3 were studied by the method of X-ray phase analysis and 7 Li and 31 P NMR. Structure of Li 0.8 Zr 1.8 Nb 0.2 (PO 4 ) 3 was refined on the basis of X-ray powder pattern. It is shown that cationic disordering in LiZr 2 (PO 4 ) 3 is stimulated both by cationic vacancies and interstitial atoms formation. The cationic vacancies are characterized by a higher mobility. The level of intrinsic disordering was estimated and the Frenkel constant for the compound was calculated [ru

Growth kinetics of tetragonal and monoclinic ZrO2 crystallites in 3 mol% yttria partially stabilized ZrO2 (3Y-PSZ) precursor powder

International Nuclear Information System (INIS)

Kuo, Chih-Wei; Lee, Kuen-Chan; Yen, Feng-Lin; Shen, Yun-Hwei; Lee, Huey-Er; Wen, Shaw-Bing; Wang, Moo-Chin; Stack, Margaret Mary

2014-01-01

Highlights: • The crystalline structures were composed of tetragonal and monoclinic ZrO 2 . • Growth kinetics of t-ZrO 2 in the 3Y-PSZ precursor powder is described as: D te 2 =(4.57±0.55)t 0.12±0.02 exp(-((24.79±0.38)×10 3 )/(RT) ). • Growth kinetics of m-ZrO 2 in the 3Y-PSZ precursor powder is described as: D m 2 =(4.40±1.63)t 0.17±0.08 exp(-((66.47±3.97)×10 3 )/(RT) ). - Abstract: The growth kinetics of tetragonal and monoclinic ZrO 2 crystallites in 3 mol% yttria partially stabilized ZrO 2 (3Y-PSZ) precursor powder has been investigated using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) specific surface area analysis, transmission electron microscopy (TEM) and high resolution TEM (HRTEM). After calcination of the 3Y-PSZ precursor powder between 773 and 1073 K for 2 h, the crystalline structures were composed of tetragonal and monoclinic ZrO 2 as the primary and secondary phases, respectively. When the 3Y-PSZ precursor powder was calcined at 773 K for 2 h, the BET specific surface area was 97.13 m 2 /g, which is equivalent to a particle size of 10.30 nm. The crystallite sizes determined via XRD and BET agreed well, indicating that the powder was virtually non-agglomerated. The growth kinetics of tetragonal and monoclinic ZrO 2 crystallite isothermal growth in the 3Y-PSZ precursor powder are described by: D te 2 =(4.57±0.55)t 0.12±0.02 exp(-((24.79±0.38)×10 3 )/(RT) ) and D m 2 =(4.40±1.63)t 0.17±0.08 exp(-((66.47±3.97)×10 3 )/(RT) ), respectively, for 773K≤T≤1073K. D te and D m denote the crystallite size of tetragonal and monoclinic ZrO 2 at time t and temperature T, respectively

Crystal structure investigations of ZrAsxSey (x>y, x+y≤2) by single crystal neutron diffraction at 300 K, 25 K and 2.3 K

International Nuclear Information System (INIS)

Niewa, Rainer; Czulucki, Andreas; Schmidt, Marcus; Auffermann, Gudrun; Cichorek, Tomasz; Meven, Martin; Pedersen, Bjoern; Steglich, Frank; Kniep, Ruediger

2010-01-01

Large single crystals of ZrAs x Se y (x>y, x+y≤2, PbFCl type of structure, space group P4/nmm) were grown by Chemical Transport. Structural details were studied by single crystal neutron diffraction techniques at various temperatures. One single crystal specimen with chemical composition ZrAs 1.595(3) Se 0.393(1) was studied at ambient temperature (R1=5.10 %, wR2=13.18 %), and a second crystal with composition ZrAs 1.420(3) Se 0.560(1) was investigated at 25 K (R1=2.70%, wR2=5.70 %) and 2.3 K (R1=2.30 %, wR2=4.70 %), respectively. The chemical compositions of the crystals under investigation were determined by wavelength dispersive X-ray spectroscopy. The quantification of trace elements was carried out by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry. According to the crystal structure refinements the crystallographic 2a site is occupied by As, together with a significant amount of vacancies. One of the 2c sites is fully occupied by As and Se (random distribution). With respect to the fractional coordinates of the atoms, the crystal structure determinations based on the data obtained at 25.0 K and 2.3 K did not show significant deviations from ambient temperature results. The temperature dependence of the displacement parameters indicates a static displacement of As on the 2a sites (located on the (0 0 1) planes) for all temperatures. No indications for any occupation of interstitial sites or the presence of vacancies on the Zr (2a) site were found. - Graphical abstract: Large single crystals of ZrAs x Se y grown by Chemical Transport to study structural details as the As-Se order scheme by single crystal neutron diffraction.

FRACTIONAL RECRYSTALLIZATION KINETICS IN DIRECTLY COLD ROLLED Al-Mg, Al-Mg-Sc AND Al-Mg-Sc-Zr ALLOY

Directory of Open Access Journals (Sweden)

M. S. Kaiser

2014-12-01

Full Text Available The evaluation of texture as a function of recrystallization has been characterized for directly cold rolled Al-6Mg, Al-6Mg-0.4Sc and Al-6Mg-0.4Sc-0.2Zr alloys. Samples were annealed isothermally at 400 °C for 1 to 240 minutes to allow recrystallization. Recrystallization kinetics of the alloys is analyzed from the micro-hardness variation. Isothermally annealed samples of aluminum alloys were also studied using JMAK type analysis to see if there exists any correlation between the methods. Recrystallization fraction behavior between two methods the scandium added alloys show the higher variation due to precipitation hardening and higher recrystallization behavior. The scandium and zirconium as a combined shows the more variation due to formation of Al3(Sc, Zr precipitate. From the microstructure it is also observed that the base Al-Mg alloy attained almost fully re-crystallized state after annealing at 400 °C for 60 minutes

Preparation, characterization, and thermal stability of B2O3-ZrO2

Directory of Open Access Journals (Sweden)

Theresia Debora Simbolon

2017-04-01

Full Text Available Synthesis of the borate-based compound with ZrOCl2 to form B2O3-ZrO2 has been conducted. The compound was characterized by FT-IR spectrophotometer, X-ray diffraction, acidity and thermal stability test. The results showed that the FT-IR main vibration spectrum of B2O3-ZrO2 compound has appeared at wave number 401.2 cm-1 for Zr-O bonding vibration, 617.2 cm-1 for B-O-B bonding vibration and 910.4 cm-1 for B-O bonding vibration. The XRD diffraction pattern shows B2O3-ZrO2 compound has an amorphous structure. The FT-IR spectrum after saturated with ammonia and potentiometric titration indicates that the compound of B2O3-ZrO2 has acidic properties with a strong level of acidity. Thermal stability test shows that the B2O3-ZrO2 compounds have high stability on temperature with increasing crystallinity after the compound was heated at 700 °C. Keywords: B2O3-ZrO2, impregnation, thermal stability.

Order-disorder phase transition in ZrV2Dsub(3.6)

International Nuclear Information System (INIS)

Didisheim, J.-J.; Yvon, K.; Tissot, P.

1981-01-01

The deuterated C15-type Laves phase ZrV 2 Dsub(3.6) undergoes a structural phase transition near room temperature (T of the order of 325 K). In the cubic high-temperature phase the deuterium atoms are disordered over two types of tetrahedral interstices, the centres of which are 1.3 A apart. In the tetragonal low-temperature phase the D atoms are ordered and occupy only the energetically more favourable interstices. The tetragonal structure is isotypic with the low-temperature phase of HfV 2 D 4 . The shortest D-D distance is 2.1 A. (author)

Effect of the Zr elements with thermal properties changes of U-7Mo-xZr/Al dispersion fuel

International Nuclear Information System (INIS)

Supardjo; Agoeng Kadarjono; Boybul; Aslina Br Ginting

2016-01-01

Thermal properties data of nuclear fuel is required as input data to predict material properties change phenomenon during the fabrication process and irradiated in a nuclear reactor. Study the influence of Zr element in the U-7Mo-xZr/Al (x = 1%, 2% and 3%) fuel dispersion to changes in the thermal properties at various temperatures have been stiffened. Thermal analysis includes determining the melting temperature, enthalpy, and phase changes made using Differential Thermal Analysis (DTA) in the temperature range between 30 °C up to 1400 °C, while the heat capacity of U-7Mo-xZr alloy and U-7Mo-xZr/Al dispersion fuel using Differential Scanning Calorimeter (DSC) at room temperature up to 450 °C. Thermal analyst data DTA shows that Zr levels of all three compositions showed a similar phenomenon. At temperatures between 565.60 °C - 584.98 °C change becomes α + δ to α + γ phase and at 649.22 °C – 650.13 °C happen smelting Al matrix Occur followed by a reaction between Al matrix with U-7Mo-xZr on 670.38 °C - 673.38 °C form U (Al, Mo)x Zr. Furthermore a phase change α + β becomes β + γ Occurs at temperatures 762.08 °C - 776.33 °C and diffusion between the matrix by U-7Mo-xZr/Al on 853.55 °C - 875.20 °C. Every phenomenon that Occurs, enthalpy posed a relative stable. Consolidation of uranium Occur in 1052.42 °C - 1104.99 °C and decomposition reaction of U (Al, Mo)x and U (Al, Zr)_x becomes (UAl_4, UAl_3, UAl_2), U-Mo, and UZr on 1328,34 °C - 1332,06 °C , The existence of Zr in U-Mo alloy increases the heat capacity of the U-7Mo-xZr/Al, dispersion fuel and the higher heat capacity of Zr levels increased due to interactions between the atoms of Zr with Al matrix so that the heat absorbed by the fuel increase. (author)

Superconducting properties of Zr1+xNi2-xGa and Zr1-xNi2+xGa Heusler compounds

Directory of Open Access Journals (Sweden)

Saad Alzahrani

2017-05-01

Full Text Available The superconducting properties of a series of Zr1+xNi2-xGa and Zr1-xNi2+xGa compounds have been investigated by x-ray diffraction, electrical resistivity, dc magnetization, and ac susceptibility measurements. While the parent compound, ZrNi2Ga, exhibited the cubic L21 Heusler structure, multiple non-cubic structures formed in the Zr and Ni rich doped materials. For x ≤ 0.3, all Zr1-xNi2+xGa compounds demonstrated superconducting behavior, but no superconductivity was observed in the Zr1+xNi2-xGa alloys for x > 0.2. The magnetization data revealed that all materials in both Zr1+xNi2-xGa and Zr1-xNi2+xGa series exhibited type-II superconductivity. With increasing doping concentration x, the paramagnetic ordering were enhanced in both systems while the superconducting properties were found to weaken. The observations are discussed considering the structural disorders in the systems.

The corrosion Characteristics and Behaviors of the Ti-2.19Al-2.35Zr alloy

International Nuclear Information System (INIS)

Kim, Tae Hoon; Kang, Chang Sun; Baek, Jong Hyuk; Kim, Hyun Gil; Choi, Byoung Kwon; Jeong, Yong Hwan

2007-01-01

Ti-2.19Al-2.35Zr alloy is being considered as a steam generator tube material for the advanced pressurized water reactor (PWR) which is being developed by KAERI for the purpose of seawater desalination as well as a small scale electricity production. The main operational environment of SMART differs somewhat from that of a commercial PWR. That is, a heat-exchange tube is always exposed to a high temperature/pressure condition and an ammonia water chemistry is designed as a pH controlling agent without an addition of boric acid. The excellent mechanical and corrosion resistance properties are required for the steam generator tube material in SMART. Thus Ti-2.19Al-2.35Zr alloy was studied to investigate of the corrosion characteristics and behaviors of the Ti- 2.19Al-2.35Zr alloy in a simulated-SMART loop

Densification and mechanical properties of ZrO2-CaAl4O7 composites obtained by reaction sintering

International Nuclear Information System (INIS)

Bruni, Yesica; Aglietti, Esteban

2016-01-01

Composites of the ZrO 2 -CaO-Al 2 O 3 system exhibit high corrosion resistance and high chemical stability, these being suitable properties for enhanced performance as refractories. In this work composites based on ZrO 2 -CaAl 4 O 7 (CA 2 ) were developed by reaction sintering of two pure ZrO 2 powders with different particle size (d 50 = 0.44 μm and d 50 = 8 μm) mixed with high-alumina cement. The effects of CaO to ZrO 2 molar ratio, particle size of ZrO 2 and sintering temperature on densification, c-ZrO 2 formation, microstructure and mechanical properties (Vickers hardness, dynamic Young's modulus and compressive strength) were determined. Porosity and mean pore size of composites reduced with decreasing both particle size of ZrO 2 and CaO content. The highest compression strength of ∝350 MPa and hardness of 6 GPa corresponded to dense ZrO 2 -based composite with 15 vol.% CA 2 sintered at 1400 C.

Superstructure formation in PrNi_2Al_3 and ErPd_2Al_3

International Nuclear Information System (INIS)

Eustermann, Fabian; Hoffmann, Rolf-Dieter; Janka, Oliver; Oldenburg Univ.

2017-01-01

The intermetallic phase ErPd_2Al_3 was obtained by arc-melting of the elements and subsequent annealing for crystal growth. The sample was studied by X-ray diffraction on powders and single crystals. The structure of ErPd_2Al_3 was refined from X-ray diffraction data and revealed a superstructure of PrNi_2Al_3 - a CaCu_5 derivative (P6/m, a=1414.3(1), c=418.87(3) pm wR=0.0820, 1060 F"2 values, 48 variables). The same superstructure was subsequently found for PrNi_2Al_3 (P6/m, a=1407.87(4), c=406.19(2) pm, wR=0.0499, 904 F"2 values, 47 variables). In the crystal structure, the aluminium and transition metal atoms form a polyanionic network according to [T_2Al_3]"δ"-, while rare earth atoms fill cavities within the networks. They are coordinated by six transition metal and twelve aluminum atoms. In contrast to the PrNi_2Al_3 type structure reported so far, two crystallographic independent rare-earth sites are found of which one (1b) is shifted by 1/2 z, causing a distortion in the structure along with a recoloring of the T and Al atoms in the network.

Cesium and its analogs, rubidium and potassium, in rhombohedral [NaZr2(PO4)3 type] and cubic (langbeinite type) phosphates: 2. Properties: behavior on heating, in aqueous solutions, and in salt melts

International Nuclear Information System (INIS)

Orlova, A.I.; Orlova, V.A.; Buchirin, A.V.; Korchenkin, K.K.; Beskrovnyj, A.I.; ); Demarin, V.T.

2005-01-01

The properties (behavior on heating, in aqueous solutions, and in salt melts) of orthophosphates A 2 RM(PO 4 ) 3 , A 2 B 0.5 Zr 1.5 (PO 4 ) 3 , and ABR 2 (PO 4 ) 3 [A = K, Rb, Cs; B = Mg, Sr, Ba; R = Ga, Fe, Cr, Ln (Ce-Lu)] crystallizing in the structure of langbeinite mineral (cubic system, space group P2 1 3, Z = 4) were studied and compared with those of NaZr 2 (PO 4 ) 3 type phosphates. The thermal transformations of the structure and the influence of temperature on the distortion of the framework-forming polyhedra were examined. The volatilization of cesium, in particular, from the solid phase in the course of its formation, was evaluated. The rates of cesium and barium leaching at 90 and 95 deg C were determined [ru

Energy-loss straggling study of proton and alpha-particle beams incident onto ZrO{sub 2} and Al{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Behar, M.; Fadanelli, R.C. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91501-970 (Brazil); Abril, I. [Departamento de Fisica Aplicada, Universitat d' Alacant, 03080 Alacant (Spain); Garcia-Molina, R. [Departamento de Fisica, Centro de Investigacion en Optica y Nanofisica, Universidad de Murcia, 30100 Murcia (Spain); Nagamine, L.C.C. [Instituto de Fisica, Universidade de Sao Paulo, C.P.66318, 05315-970 Sao Paulo (Brazil)

2011-10-15

The energy-loss straggling of zirconia (ZrO{sub 2}) and alumina (Al{sub 2}O{sub 3}) has been experimentally determined for proton and alpha-particle beams mainly by means of the Rutherford backscattering technique and in some few cases using the transmission method. The incident energies of the projectiles covers a wide range, from 200 keV up to 2000 keV for H{sup +} and from 200 keV up to 4000 keV for He{sup +} in zirconia films. In the case of alumina films the studied energy range was 100 keV - 3000 keV for H{sup +} and 100 keV - 6000 keV for He{sup +}. Our experimental results compare very well with theoretical calculations based on the dielectric formalism and a suitable description of the electronic excitation spectrum of ZrO{sub 2} and Al{sub 2}O{sub 3} films through their energy-loss function. (authors)

Phase transformations, heat evolution, and atomic diffusion during slow heating of Al-rich Al/Zr multilayered foils

Energy Technology Data Exchange (ETDEWEB)

Fisher, Kaitlynn; Barron, S. C.; Knepper, R.; Weihs, T. P., E-mail: weihs@jhu.edu [Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218-2689 (United States); Bonds, M. A.; Browning, N. D. [Department of Chemical Engineering and Materials Science, University of California, Davis, California 95616 (United States); Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Livi, K. J. T. [High-Resolution Analytical Electron Microbeam Facility, Integrated Imaging Center, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Campbell, G. H. [Condensed Matter and Materials Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2013-12-28

We describe the energy and sequence of phase transformations in multilayered Al/Zr foils with atomic ratios of 3 Al:1 Zr during low temperature (<350 °C) heat treatments in a differential scanning calorimeter. The initial phase formed is an Al-rich amorphous phase that appears to grow by Zr diffusion through the amorphous phase. The subsequent nucleation and growth of tetragonal Al{sub 3}Zr along the Al/amorphous layer interface is mediated by Al diffusion through the crystalline intermetallic phase. Diffusion coefficients associated with these processes are higher than expected from reports of diffusivities measured at higher temperatures. The inferred heat of formation of the tetragonal Al{sub 3}Zr phase is 1240 ± 40 J/g (53 ± 2 kJ/mol atom). No anomalous variation in the energy or sequence of phase transformations is found with bilayer thickness for samples with bilayer thickness in the range of 17 nm to 90 nm despite anomalies in the bilayer dependence of self-propagating reaction velocities in the same foils.

Characterization of physical properties of Al2O3 and ZrO2 nanofluids for heat transfer applications

International Nuclear Information System (INIS)

Rocha, Marcelo S.; Cabral, Eduardo L.L.; Sabundjian, Gaiane; Yoriyaz, Helio; Lima, Ana Cecilia S.; Belchior Junior, Antonio; Prado, Adelk C.; Filho, Tufic M.; Andrade, Delvonei A.; Shorto, Julian M.B.; Mesquita, Roberto N.; Otubo, Larissa; Baptista Filho, Benedito D.; Pinho, Priscila G.M.; Ribatsky, Gherhardt; Moraes, Anderson Antonio Ubices

2015-01-01

Studies demonstrate that nanofluids based on metal oxide nanoparticles have physical properties that characterize them as promising fluids, mainly, in industrial systems in which high heat flux takes place. Water based nanofluids of Al 2 O 3 and ZrO 2 were characterized regarding its promising use in heat transfer applications. Three different concentrations of dispersed solutions of cited nanofluids were prepared (0.01% vol., 0.05% vol., and 0.1% vol.) from commercial nanofluids. Experimental measurements were carried out at different temperatures. Thermal conductivity, viscosity and density of the prepared nanofluids were measured. (author)

Influence of aluminium incorporation on the structure of ZrN films deposited at low temperatures

Energy Technology Data Exchange (ETDEWEB)

Araiza, J J [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Paseo a la Bufa esq, Calzada Solidaridad s/n 98060, Zacatecas (Mexico); Sanchez, O [Departamento de Fisica e Ingenieria de Superficies, Instituto de Ciencia de Materiales de Madrid-CSIC, C/ Sor Juana Ines de la Cruz 3, 28049 Cantoblanco, Madrid (Spain)], E-mail: olgas@icmm.csic.es

2009-06-07

We have studied the influence of Al incorporation in the crystalline structure of ZrN thin films deposited by dc magnetron sputtering at low temperature. The amount of aluminium in the films depends directly on the power applied to the aluminium cathode during the deposition. Energy dispersive x-ray analysis and x-ray diffraction (XRD) were used to obtain the chemical composition and crystalline structure of the films, respectively. When Al atoms are incorporated into the ZrN coatings, the strong ZrN (2 0 0) orientation is modified by a combination of other ones such as ZrN (1 1 1), Zr{sub 3}N{sub 4} (2 1 1) and hexagonal AlN (1 0 0) as detected from the XRD spectra for high aluminium concentrations. Fourier-transform infrared spectroscopy allowed us to identify oxides and nitrides, ZrO, AlO and AlN, incorporated into the deposited films. The effect of a bias voltage applied to the substrate has also been investigated and related to the changes in the microstructure and in the nanohardness values of the ZrAlN films.

Development of powder metallurgy 2XXX series Al alloys for high temperature aircraft structural applications

Science.gov (United States)

Chellman, D. J.

1984-01-01

The objective of the present investigation was to improve the strength and fracture toughness combination of P/M 2124 Al alloys in accordance with NASA program goals for damage tolerance and fatigue resistance. Two (2) P/M compositions based on Al-3.70 Cu-1.85 Mg-0.20 Mn with 0.12 and 0.60 wt. pct. Zr were selected for investigation. The rapid solidification rates produced by atomization were observed to prohibit the precipitation of coarse, primary Al3Zr in both alloys. A major portion of the Zr precipitated as finely distributed, coherent Al3Zr phases during vacuum preheating and solution heat treatment. The proper balance between Cu and Mg contents eliminated undissolved, soluble constituents such as Al2CuMg and Al2Cu during atomization. The resultant extruded microstructures produced a unique combination of strength and fracture toughness. An increase in the volume fraction of coherent Al3Zr, unlike incoherent Al20Cu2Mn3 dispersoids, strengthened the P/M Al base alloy either directly by dislocation-precipitate interactions, indirectly by a retardation of recrystallization, or a combination of both mechanisms. Furthermore, coherent Al3Zr does not appear to degrade toughness to the extent that incoherent Al20Cu2Mn3 does. Consequently, the addition of 0.60 wt. pct. Zr to the base alloy, incorporated with a 774K (935 F) solution heat treatment temperature, produces an alloy which exceeds all tensile property and fracture toughness goals for damage tolerant and fatigue resistant applications in the naturally aged condition.

Characterization of the interaction layer in diffusion couples U-Mo-Zr/Al and U-Mo-Zr/Al-A356 at 550 C degrees

International Nuclear Information System (INIS)

Komar Varela, Carolina; Arico, Sergio; Mirandou, Marcela; Balart, Silvia; Gribaudo, Luis

2007-01-01

Out-of-pile diffusion experiments were performed between U-7 wt.% Mo-1 wt.% Zr and Al or Al A356 (7,1 wt.% Si) at 550 C degrees. In this work morphological characterization and phase identification on both interaction layers are presented. They were carried out by the use of different techniques: optical and scanning electron microscopy, X-ray diffraction and WDS microanalysis. In the interaction layer U-7 wt.% Mo-1 wt.% Zr/Al, the phases UAl 3 , UAl 4 , Al 20 Mo 2 U and Al 43 Mo 4 U 6 were identified. Similar results in the interaction layer of the U-7 % Mo/Al at 580 C degrees were previously obtained. In the interaction layer U-7 wt.% Mo-1 wt.% Zr/Al A356, the phases U(Al,Si) 3 with 25 at.% Si and Si 5 U 3 were identified. This last phase, with a higher Si concentration, was identified with X-ray diffraction synchrotron radiation performed at the National Synchrotron Light Laboratory, Campinas, Brazil. (author) [es

Influence of Thickness of Multilayered Nano-Structured Coatings Ti-TiN-(TiCrAlN and Zr-ZrN-(ZrCrNbAlN on Tool Life of Metal Cutting Tools at Various Cutting Speeds

Directory of Open Access Journals (Sweden)

Alexey Vereschaka

2018-01-01

Full Text Available This paper considers the influence of thickness of multilayered nano-structured coatings Ti-TiN-(TiCrAlN and Zr-ZrN-(ZrCrNbAlN on tool life of metal cutting tools at various cutting speeds (vc = 250, 300, 350 and 400 m·min−1. The paper investigates the basic mechanical parameters of coatings and the mechanism of coating failure in scratch testing depending on thickness of coating. Cutting tests were conducted in longitudinal turning of steel C45 with tools with the coatings under study of various thicknesses (3, 5, and 7 µm, with an uncoated tool and with a tool with a “reference” coating of TiAlN. The relationship of “cutting speed vc—tool life T” was built and investigated; and the mechanisms were found to determine the selection of the optimum coating thickness at various cutting speeds. Advantages of cutting tools with these coatings are especially obvious at high cutting speeds (in particular, vc = 400 m·min−1. If at lower cutting speeds, the longest tool life is shown by tools with thicker coatings (of about 7 μm, then with an increase in cutting speed (especially at vc = 400 m·min−1 the longest tool life is shown by tools with thinner coating (of about 3 μm.

Valence electron structure and properties of stabilized ZrO2

Institute of Scientific and Technical Information of China (English)

LI JinPing; HAN JieOai; MENG SongHe; ZHANG XingHong

2008-01-01

To reveal the properties of stabilizers in ZrO2 on nanoscopic levels,the valence elec-tron structures of four stable ZrO2 phases and c-ZrO2 were analyzed on the basis of the empirical electron theory of solids and molecules.The results showed that the hybridization levels of Zr atoms in c-ZrO2 doped with Ca and Mg dropped from B17 to B13,the hybridization levels of Zr atoms in c-ZrO2 doped with Y and Ce dropped from B17 to B15,and that the four stabilizing atoms all made the hybridization levels of O atoms drop from level 4 to level 2.The numbers of covalent electrons in the strongest covalent bond in the descending order are c-ZrO2>ZrCeO2>ZrYOZrMgO>ZrCaO.The bond energies of the strongest covalent bond and the melting points of the solid solutions in the descending order are ZrCeO2>c-ZrO2>ZrYO>ZrMgO>ZrCaO.The percent-ages of the total number of covalent electrons in the descending order arec-ZrO2>ZrYO> ZrCeO2>ZrMgO> ZrCaO.From the above analysis,it can be concluded that the stabilizing degrees of the four stabilizers in the descending order are CaO> MgO>Y2O3>CeO2.

Design of Rh/Ce0.2Zr0.8O2-Al2O3 nanocomposite for ethanol steam reforming

International Nuclear Information System (INIS)

De Rogatis, Loredana; Montini, Tiziano; Casula, Maria F.; Fornasiero, Paolo

2008-01-01

Rh(1 wt.%)/Ce 0.2 Zr 0.8 O 2 (10 wt.%)-Al 2 O 3 nanocomposite has been investigated as active and thermally stable catalyst for ethanol steam reforming. Rh nanoparticles were synthesised by surfactant assisted route, using N-hexadecyl-N-(2-hydroxyethyl)-N,N-dimethyl ammonium bromide (HEAC16Br). Metal particles with average diameter of 2.1 nm were obtained at 0.53 Rh/HEAC16Br molar ratio, while increasing the amount of surfactant lead to formation of larger particles. The preformed Rh nanoparticles have been effectively embedded into a porous layer of nanocomposite oxides. Low temperature H 2 chemisorption experiments and activity data confirm that most of the Rh atoms are accessible to the reaction mixture. The Ce 0.2 Zr 0.8 O 2 mixed oxide inhibits the dehydration of ethanol to ethylene and favours the water gas shift reaction. The alumina ensures good thermal stability and high surface area of the catalyst. No significant deactivation is observed after repeated run-up and run-down experiments

Synthesis of ZrO2-8%CeO2 and ZrO2-8%Y2O3 by polymeric precursors route

International Nuclear Information System (INIS)

Macedo, D.A.; Macedo, M.C.; Melo, D.M.A.; Nascimento, R.M.; Rabelo, A.A.

2006-01-01

The stabilization of zirconia in the cubical and tetragonal structures comes gaining importance because of its excellent thermal stability, chemical resistance, mechanical properties and oxygen conductivity. Its main applications include electrolytes of high temperature fuel cells, sensors of oxygen and electrochemical reactors. In this work the polymeric precursors route was used to synthesize ZrO 2 -8 mol% Y 2 O 3 and ZrO 2 -8 mol%CeO 2 . In this process the dopant concentration, besides making possible the stabilization of distinct structures, influences in the morphologic characteristics of the powders synthesized. The characterization of the powders was carried through X-ray diffraction for existing phases verification and average crystallite size, thermogravimetric analysis, specific surface area measures, particles size distribution by laser scattering and the powder morphology was observed using scanning electronic microscopy. The powder only calcined at 700 deg C had presented of average crystallite size of 6,77 nm for ZrO 2 -8%Y 2 O 3 and 7,14 nm for ZrO 2 -CeO 2 . (author)

Crystal Structure, Spectroscopic Investigations, and Physical Properties of the Ternary Intermetallic REPt2Al3 (RE = Y, Dy–Tm and RE2Pt3Al4 Representatives (RE = Tm, Lu

Directory of Open Access Journals (Sweden)

Fabian Eustermann

2018-04-01

Full Text Available The REPt2Al3 compounds of the late rare-earth metals (RE = Y, Dy–Tm were found to crystallize isostructural. Single-crystal X-ray investigations of YPt2Al3 revealed an orthorhombic unit cell (a = 1080.73(6, b = 1871.96(9, c = 413.04(2 pm, wR2 = 0.0780, 942 F2 values, 46 variables with space group Cmmm (oC48; q2pji2hedb. A comparison with the Pearson database indicated that YPt2Al3 forms a new structure type, in which the Pt and Al atoms form a [Pt2Al3]δ− polyanion and the Y atoms reside in the cavities within the framework. Via a group-subgroup scheme, the relationship between the PrNi2Al3-type structure and the new YPt2Al3-type structure was illustrated. The compounds with RE = Dy–Tm were characterized by powder X-ray diffraction experiments. While YPt2Al3 is a Pauli-paramagnet, the other REPt2Al3 (RE = Dy–Tm compounds exhibit paramagnetic behavior, which is in line with the rare-earth atoms being in the trivalent oxidation state. DyPt2Al3 and TmPt2Al3 exhibit ferromagnetic ordering at TC = 10.8(1 and 4.7(1 K and HoPt2Al3 antiferromagnetic ordering at TN = 5.5(1 K, respectively. Attempts to synthesize the isostructural lutetium compound resulted in the formation of Lu2Pt3Al4 (Ce2Ir3Sb4-type, Pnma, a = 1343.4(2, b = 416.41(8, c = 1141.1(2 pm, which could also be realized with thulium. The structure was refined from single-crystal data (wR2 = 0.0940, 1605 F2 values, 56 variables. Again, a polyanion with bonding Pt–Al interactions was found, and the two distinct Lu atoms were residing in the cavities of the [Pt3Al4]δ– framework. X-ray photoelectron spectroscopy (XPS measurements were conducted to examine the electron transfer from the rare-earth atoms onto the polyanionic framework.

The Structural Evolution of (Gd, Y)Ba2Cu3Ox Tapes With Zr Addition Made by Metal Organic Chemical Vapor Deposition

Energy Technology Data Exchange (ETDEWEB)

Lei, CH; Galstyan, E; Chen, YM; Shi, T; Liu, YH; Khatri, N; Liu, JF; Xiong, XM; Majkic, G; Selvamanickam, V

2013-06-01

Structural analysis of (Gd, Y) Ba2Cu3Ox tapes with Zr addition made by metal organic chemical vapor deposition has been conducted with transmission electron microscopy and X-ray diffraction. Zr content in the films was varied from 0 to 25% in the precursor. In all Zr-doped films, self-assembled nanocolumnar structures of BaZrO3 (BZO) were observed along the c-axis. The amount of BaZrO3 was found to increase steadily with Zr content. Additionally, planar BZO plates were found on the (001) plane of (Gd, Y) Ba2Cu3Ox film. The size and thickness of BZO plates were seen to increase with Zr doping level. Rare-earth copper oxide phases were observed to begin to emerge in the 20% Zr-doped film. Cross-sectional study of the interface between (Gd, Y)Ba2Cu3Ox and LaMnO3 cap layer revealed a thin discrete BZO layer on the LaMnO3 in the 20% Zr doped film.

Evaluating the toughness of APS and HVOF-sprayed Al2O3-ZrO2-coatings by in-situ- and macroscopic bending

Czech Academy of Sciences Publication Activity Database

Kiilakoski, J.; Mušálek, Radek; Lukáč, František; Koivuluoto, H.; Vuoristo, P.

2018-01-01

Roč. 38, č. 4 (2018), s. 1908-1918 ISSN 0955-2219 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Thermal spray * Al2O3-ZrO2 * Toughening * Fracture * Mechanical testing Subject RIV: JK - Corrosion ; Surface Treatment of Materials OBOR OECD: Coating and films Impact factor: 3.411, year: 2016 https://www.sciencedirect.com/science/article/pii/S0955221917308051

Effect of {gamma}` and {gamma} (Ag{sub 2}Al) precipitates on the steady state creep of Al-16wt%Ag alloys with and without Zr addition

Energy Technology Data Exchange (ETDEWEB)

Deaf, G.H. [Ain Shams Univ., Cairo (Egypt). Dept. of Physics; Youssef, S.B. [Ain Shams Univ., Cairo (Egypt). Dept. of Physics; Mahmoud, M.A. [Ain Shams Univ., Cairo (Egypt). Dept. of Physics

1996-11-16

The steady state creep behaviour of Al-16 wt% Ag and Al-16 wt% Ag-0.1 wt% Zr alloys has been studied at constant load (= 137.2 MPa) and tested at different working temperatures for samples aged at temperatures favouring the formation of {gamma}` and {gamma} precipitates. It was found that addition of Zr to Al-16 wt% Ag alloy accelerates the precipitations {gamma}` and {gamma} due to the formation of the metastable phase Al{sub 3}Zr. For both alloys, two values of activation energy have been obtained as (34 {+-} 0.3) kJ/mol for viscous glide of dislocations due to the existence of {gamma}` precipitates and (68 {+-} 0.3) kJ/mol for grain boundary diffusion due to the existence of {gamma} precipitates. TEM investigations of {gamma}` and {gamma} precipitates confirmed the above-mentioned effect of Zr addition. (orig.)

Effect of Zr on microstructures and mechanical properties of an Al-Mg-Si-Cu-Cr alloy prepared by low frequency electromagnetic casting

Energy Technology Data Exchange (ETDEWEB)

Meng, Yi, E-mail: yimonmy@sina.com; Cui, Jianzhong; Zhao, Zhihao; He, Lizi

2014-06-01

The Al-1.6Mg-1.2Si-1.1Cu-0.15Cr (all in wt. %) alloys with and without Zr addition prepared by low frequency electromagnetic casting process were investigated by using the optical microscope, scanning electron microscope and transmission electron microscope equipped with energy dispersive analytical X-ray. The effects of Al{sub 3}Zr phases on the microstructures and mechanical properties during solidification, homogenization, hot extrusion and solid solution were studied. The results show that Al{sub 3}Zr phases reduce the grain size by ∼ 29% and promote the formation of an equiaxed grain structure during solidification. Numerous spherical Al{sub 3}Zr dispersoids with 35–60 nm in diameters precipitate during homogenization, and these fine dispersoids change little during subsequent hot extrusion and solid solution. Adding 0.15 wt. % Zr results in no recrystallization after hot extrusion and partial recrystallization after solid solution, while the recrystallized grain size is 400–550 μm in extrusion direction in the Zr-free alloy. In addition, adding 0.15 wt. % Zr can obviously promote Q′ phase precipitation, while the β″ phases are predominant in the alloy without Zr. Adding 0.15 wt. % Zr, the ultimate tensile strength of the T6 treated alloy increases by 45 MPa, while the elongation remains about 16.7%. - Highlights: • Minor Zr can refine as-cast grains of the LFEC Al-Mg-Si-Cu-Cr alloy. • L1{sub 2} Al{sub 3}Zr phases with 35–60 nm in diameter precipitate during homogenization. • L1{sub 2} and DO{sub 22} Al{sub 3}Zr phases result in partial recrystallization after solid solution. • Minor Zr can promote the precipitation of Q′ phases. • Mechanical properties of Al-Mg-Si-Cu-Cr-Zr alloy are higher than those of AA7005.

Effect of Zr on microstructures and mechanical properties of an Al-Mg-Si-Cu-Cr alloy prepared by low frequency electromagnetic casting

International Nuclear Information System (INIS)

Meng, Yi; Cui, Jianzhong; Zhao, Zhihao; He, Lizi

2014-01-01

The Al-1.6Mg-1.2Si-1.1Cu-0.15Cr (all in wt. %) alloys with and without Zr addition prepared by low frequency electromagnetic casting process were investigated by using the optical microscope, scanning electron microscope and transmission electron microscope equipped with energy dispersive analytical X-ray. The effects of Al 3 Zr phases on the microstructures and mechanical properties during solidification, homogenization, hot extrusion and solid solution were studied. The results show that Al 3 Zr phases reduce the grain size by ∼ 29% and promote the formation of an equiaxed grain structure during solidification. Numerous spherical Al 3 Zr dispersoids with 35–60 nm in diameters precipitate during homogenization, and these fine dispersoids change little during subsequent hot extrusion and solid solution. Adding 0.15 wt. % Zr results in no recrystallization after hot extrusion and partial recrystallization after solid solution, while the recrystallized grain size is 400–550 μm in extrusion direction in the Zr-free alloy. In addition, adding 0.15 wt. % Zr can obviously promote Q′ phase precipitation, while the β″ phases are predominant in the alloy without Zr. Adding 0.15 wt. % Zr, the ultimate tensile strength of the T6 treated alloy increases by 45 MPa, while the elongation remains about 16.7%. - Highlights: • Minor Zr can refine as-cast grains of the LFEC Al-Mg-Si-Cu-Cr alloy. • L1 2 Al 3 Zr phases with 35–60 nm in diameter precipitate during homogenization. • L1 2 and DO 22 Al 3 Zr phases result in partial recrystallization after solid solution. • Minor Zr can promote the precipitation of Q′ phases. • Mechanical properties of Al-Mg-Si-Cu-Cr-Zr alloy are higher than those of AA7005

Surface Characterization of ZrO2/Zr Coating on Ti6Al4V and IN VITRO Evaluation of Corrosion Behavior and Biocompatibility

Science.gov (United States)

Wang, Ruoyun; Sun, Yonghua; He, Xiaojing; Gao, Yuee; Yao, Xiaohong

Biocompatibility is crucial for implants. In recent years, numerous researches were conducted aiming to modify titanium alloys, which are the most extensively used materials in orthopedic fields. The application of zirconia in the biomedical field has recently been explored. In this study, the biological ZrO2 coating was synthesized on titaniumalloy (Ti6Al4V) substrates by a duplex-treatment technique combining magnetron sputtering with micro-arc oxidation (MAO) in order to further improve the corrosion resistance and biocompatibility of Ti6Al4V alloys. The microstructures and phase constituents of the coatings were characterized by scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), the surface wettability was evaluated by contact angle measurements. The results show that ZrO2 coatings are porous with pore sizes less than 2μm and consist predominantly of the tetragonal ZrO2 (t-ZrO2) and cubic ZrO2(c-ZrO2) phase. Electrochemical tests indicate that the corrosion rate of Ti6Al4V substrates is appreciably reduced after surface treatment in the phosphate buffer saline (PBS). In addition, significantly improved cell adhesion and growth were observed from the ZrO2/Zr surface. Therefore, the hybrid approach of magnetron sputtering and MAO provides a surface modification for Ti6Al4V to achieve acceptable corrosion resistance and biocompatibility.

Al2O3 Passivation Effect in HfO2·Al2O3 Laminate Structures Grown on InP Substrates.

Science.gov (United States)

Kang, Hang-Kyu; Kang, Yu-Seon; Kim, Dae-Kyoung; Baik, Min; Song, Jin-Dong; An, Youngseo; Kim, Hyoungsub; Cho, Mann-Ho

2017-05-24

The passivation effect of an Al 2 O 3 layer on the electrical properties was investigated in HfO 2 -Al 2 O 3 laminate structures grown on indium phosphide (InP) substrate by atomic-layer deposition. The chemical state obtained using high-resolution X-ray photoelectron spectroscopy showed that interfacial reactions were dependent on the presence of the Al 2 O 3 passivation layer and its sequence in the HfO 2 -Al 2 O 3 laminate structures. Because of the interfacial reaction, the Al 2 O 3 /HfO 2 /Al 2 O 3 structure showed the best electrical characteristics. The top Al 2 O 3 layer suppressed the interdiffusion of oxidizing species into the HfO 2 films, whereas the bottom Al 2 O 3 layer blocked the outdiffusion of In and P atoms. As a result, the formation of In-O bonds was more effectively suppressed in the Al 2 O 3 /HfO 2 /Al 2 O 3 /InP structure than that in the HfO 2 -on-InP system. Moreover, conductance data revealed that the Al 2 O 3 layer on InP reduces the midgap traps to 2.6 × 10 12 eV -1 cm -2 (compared to that of HfO 2 /InP, that is, 5.4 × 10 12 eV -1 cm -2 ). The suppression of gap states caused by the outdiffusion of In atoms significantly controls the degradation of capacitors caused by leakage current through the stacked oxide layers.

Effect of Zr Purity and Oxygen Content on the Structure and Mechanical Properties of Melt-Spun and Suction-Cast Cu46Zr42Al7Y5 Alloy

Directory of Open Access Journals (Sweden)

Kozieł T.

2016-06-01

Full Text Available The effect of oxygen content in zirconium on the structure and mechanical properties of the Cu46Zr42Al7Y5 alloy, in the form of melt-spun ribbons and suction-cast rods, was investigated. Two types of Zr, rod and crystal bar of different nominal purities and oxygen contents, were used to synthesize the alloy by arc melting. Rapidly solidified ribbons were produced by melt spinning and their amorphous structures were confirmed by X-ray diffractometry (XRD and differential scanning calorimetry (DSC. Bulk samples in the form of rods were cast using a special water-cooled suction casting unit attached to the arc melting system. XRD and DSC studies proved the amorphous structure of the bulk alloy synthesized from low-oxygen Zr and partial crystallization of the same alloy for high-oxygen Zr. In both bulk samples, uniformly distributed crystalline particles were identified as yttrium oxides. Higher mean compressive strength of amorphous alloy was observed. The hardness of amorphous phase was close to 500 HV1 in both bulk alloys, while the hardness of crystalline dendritic areas, observed in the alloy synthesized from high oxygen Zr, was lower by about 50 HV1.

Alpha and beta stabilizer character of Al in Zr-Nb-Al alloys

International Nuclear Information System (INIS)

Peruzzi Bardella, A.; Bolcich, J.C.

1987-01-01

The T β/α+β of Zr5Nb and Zr5Nb2Al (weight %) were determined in order to observe the alpha-stabilizer character of Al in ternary Zr-Nb-Al alloys. Techniques employed were change of resistivity with temperature in dynamic experiences, and metallography of samples quenched to room temperature after isothermal annealings. The T β/α+β of the ternary resulted 17 ± 8 deg C higher than that of the binary alloy. In addition, taking into account the results of previous investigations of the transformation of beta on quenching Zr-Nb-Al alloys from the beta field to room temperature, it is concluded that the beta-stabilizer character of Nb is stronger than the alpha-stabilizer character of Al in these Zr alloys, and that the Al can have important influence on the mechanical properties by the appearance of TRIP effect. (Author) [es

Structural characterization and optical properties of perovskite ZnZrO 3 nanoparticles

KAUST Repository

Zhu, Xinhua

2014-03-17

Perovskite ZnZrO3 nanoparticles were synthesized by hydrothermal method, and their microstructures and optical properties were characterized. The crystallinity, phase formation, morphology and composition of the as-synthesized nanoparticles were characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED), high-resolutiontransmission electron microscopy (HRTEM), and energy-dispersive X-ray (EDX) spectroscopy analysis, respectively. TEM images demonstrated that the average particle size of the ZnZrO3 powders was increased with increasing the Zn/Zr molar ratios in the precursors, and more large ZnZrO3 particles with cubic morphology were observed at high Zn/Zr molar ratios. In addition, the phase structures of the ZnZrO3 particles were also evolved from a cubic to tetragonal perovskite phase, as revealed by XRD and SAED patterns. HRTEM images demonstrate that surface structures of the ZnZrO3 powders synthesized at high Zn/Zr molar ratios, are composed of corners bound by the {100} mini-facets, and the surface steps lying on the {100} planes are frequently observed, whereas the (101) facet isoccasionally observed. The formation of such a rough surface structure is understood from the periodic bond chain theory. Quantitative EDX analyses demonstrated that the atomic concentrations (at.%) of Zn:Zr:O in the particles were 20.70:21.07:58.23, as close to the composition of ZnZrO3. In the optical spectra, a significant red shift of the absorption edges (for the ZnZrO3 nanopowders) from UV to visible region (from 394 to 417 nm) was observed as increasing the Zn/Zr molar ratios in the precursors, which corresponds to that the band gap energies of the ZnZrO3 nanopowders can be continuously tuned from 3.15 to 2.97 eV. This opens an easy way to tune the band gap energies of the ZnZrO3 nanopowders. © 2014 The American Ceramic Society.

The behavior of ZrO{sub 2}/20%Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} coatings deposited on aluminum alloys at high temperature regime

Energy Technology Data Exchange (ETDEWEB)

Pintilei, G.L., E-mail: laura_rares082008@yahoo.com [Pitesti University, Faculty of Mechanics and Technology, Str. Targu din Vale nr.1, 110040 Pitesti, Arges (Romania); Technical University “Gheorghe Asachi” of Iasi, Faculty of Mechanics, Bld D. Mangeron nr. 61, 700050 Iasi (Romania); Crismaru, V.I. [Technical University “Gheorghe Asachi” of Iasi, Faculty of Mechanics, Bld D. Mangeron nr. 61, 700050 Iasi (Romania); Abrudeanu, M. [Pitesti University, Faculty of Mechanics and Technology, Str. Targu din Vale nr.1, 110040 Pitesti, Arges (Romania); Munteanu, C. [Technical University “Gheorghe Asachi” of Iasi, Faculty of Mechanics, Bld D. Mangeron nr. 61, 700050 Iasi (Romania); Baciu, E.R. [University of Medicine and Pharmacy “Gr.T.Popa”, Department Implantology, Removable Restorations, Technology, Str. Universitatii nr. 16, 700115 Iasi (Romania); Istrate, B.; Basescu, N. [Technical University “Gheorghe Asachi” of Iasi, Faculty of Mechanics, Bld D. Mangeron nr. 61, 700050 Iasi (Romania)

2015-10-15

Highlights: • In both the ZrO{sub 2}/20%Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} coatings the high temperature caused a decrease of pores volume and a lower thickness of the interface between successive splats. • The NiCr bond layer in the sample with a ZrO{sub 2}/20%Y{sub 2}O{sub 3} suffered a fragmentation due to high temperature exposure and thermal expansion which can lead to coating exfoliation. • The NiCr bond layer in the sample with an Al{sub 2}O{sub 3} coating showed an increase of pore volume due to high temperature. - Abstract: Aluminum alloy present numerous advantages like lightness, high specific strength and diversity which recommend them to a high number of applications from different fields. In extreme environments the protection of aluminum alloys is difficult and requires a high number of requirements like high temperature resistance, thermal fatigue resistance, corrosion fatigue resistance and galvanic corrosion resistance. To obtain these characteristics coatings can be applied to the surfaces so they can enhance the mechanical and chemical properties of the parts. In this paper two coatings were considered for deposition on an AA2024 aluminum alloy, ZrO{sub 2}/20%Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3}. To obtain a better adherence of the coating to the base material an additional bond layer of NiCr is used. Both the coatings and bond layer were deposited by atmospheric plasma spraying on the samples. The samples were subjected to a temperature of 500 °C and after that slowly cooled to room temperature. The samples were analyzed by electron microscopy and X-ray diffraction to determine the morphological and phase changes that occurred during the temperature exposure. To determine the stress level in the parts due to thermal expansion a finite element analysis was performed in the same conditions as the tests.

Computer simulation of the structural transformation in liquid Al2O3

International Nuclear Information System (INIS)

Vo Van Hoang; Oh, Suhk Kun

2005-01-01

We investigate the pressure-induced structural transformation in liquid Al 2 O 3 by a molecular dynamics (MD) method. Simulations were done in the basic cube, under periodic boundary conditions, containing 3000 ions with Born-Mayer-type pair potentials. The structure of the liquid Al 2 O 3 model with a real density at ambient pressure is in good agreement with Landron's experiment. In order to study the structural transformation, seven models of liquid alumina at temperature 2500 K and at densities in the range 2.80-4.5 g cm -3 have been built. The microstructure of Al 2 O 3 systems has been analysed through the pair radial distribution functions, coordination number distributions, interatomic distances and bond-angle distributions. And we found clear evidence of a structural transition in liquid alumina from a tetrahedral to an octahedral network. According to our results, this transformation occurred at densities in the range 3.6-4.5 g cm -3 . We also obtained an anomalous density dependence of the self-diffusion constant in the region of the structural transformation

Experimental Investigation of the 1073 K (800 °C) Isothermal Section of the Al-V-Zr Ternary System

Science.gov (United States)

Zhu, Yude; Ouyang, Xuemei; Yin, Fucheng; Zhao, Manxiu; Lou, Jia

2018-03-01

This work is focused on an experimental investigation of the phase equilibria of the Al-V-Zr system at 1073 K (800 °C). The phase equilibria were analyzed using scanning electron microscopy (SEM) coupled with energy-dispersive spectrometry and X-ray diffraction. The results confirmed the presence of twelve three-phase regions and one ternary compound, Τ, which contains 10.0 to 16.5 at. pct Zr, 52.8 to 55.2 at. pct Al, and 29.3 to 36.3 at. pct V. The T phase can be in equilibrium with Al8V5, Al3Zr, Al2Zr, and α-V. The T phase belongs to the tetragonal crystal system with confirmed lattice parameters of a = 0.658531 nm and c = 0.517334 nm. The Al2Zr phase region is extraordinarily large and can be in equilibrium with all the compounds in the Al-Zr and V-Zr systems, with the exception of the AlZr phase.

Performance improvement of charge-trap memory by using a stacked Zr{sub 0.46}Si{sub 0.54}O{sub 2}/Al{sub 2}O{sub 3} charge-trapping layer

Energy Technology Data Exchange (ETDEWEB)

Tang, Zhenjie; Hu, Dan; Zhang, Xiwei; Zhao, Yage [College of Physics and Electronic Engineering, Anyang Normal University, Anyang 455000 (China); Li, Rong [School of Mathematics and Statistics, Anyang Normal University, Anyang 455000 (China)

2016-11-15

The postdeposition annealing (PDA)-treated charge-trap flash memory capacitor with stacked Zr{sub 0.46}Si{sub 0.54}O{sub 2}/Al{sub 2}O{sub 3} charge-trapping layer flanked by a SiO{sub 2} tunneling oxide and an Al{sub 2}O{sub 3} blocking oxide was fabricated and investigated. It is observed that the memory capacitor exhibits prominent memory characteristics with large memory windows 12.8 V in a ±10 V gate sweeping voltage range, faster program/erase speed, and good data-retention characteristics even at 125 C compared to a single charge-trapping layer (Zr{sub 0.46}Si{sub 0.54}O{sub 2}, Zr{sub 0.79}Si{sub 0.21}O{sub 2}, and Zr{sub 0.46}Al{sub 1.08}O{sub 2.54}). The quantum wells and introduced interfacial traps of the stacked trapping layer regulate the storage and loss behavior of charges, and jointly contribute to the improved memory characteristics. Hence, the memory capacitor with a stacked trapping layer is a promising candidate in future nonvolatile charge-trap memory device design and application. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Correlation between local structure and stability of supercooled liquid state in Zr-based metallic glasses

International Nuclear Information System (INIS)

Saida, Junji; Imafuku, Muneyuki; Sato, Shigeo; Sanada, Takashi; Matsubara, Eiichiro; Inoue, Akihisa

2007-01-01

The correlation between the local structure and stability of supercooled liquid state is investigated in the Zr 70 (Ni, Cu) 30 binary and Zr 70 Al 10 (Ni, Cu) 20 (numbers indicate at.%) ternary metallic glasses. The Zr 70 Ni 30 binary amorphous alloy with a low stability of supercooled liquid state has a tetragonal Zr 2 Ni-like local structure around Ni atom. Meanwhile, the Zr 70 Cu 30 binary metallic glass has a different local structure of tetragonal Zr 2 Cu, where we suggest the icosahedral local structure by the quasicrystallization behavior in addition of a very small amount of noble metals. The effect of Al addition on the local structure in the Zr-Ni alloy is also examined. We have investigated that the dominant local structure changes in the icosahedral-like structure from the tetragonal Zr 2 Ni-like local structure by the Al substitution with Ni accompanying with the significant stabilization of supercooled liquid state. It is concluded that the formation of icosahedral local structure contributes to the enhancement of stability of supercooled liquid state in the Zr-based alloys

Bixbyite-type phases in the system Ta-Zr-O-N

Energy Technology Data Exchange (ETDEWEB)

Luedtke, Tobias; Orthmann, Steven; Lerch, Martin [Technische Univ. Berlin (Germany). Inst. fuer Chemie

2017-06-01

Phase-pure tantalum/zirconium oxide nitrides and nitrides were synthesized by the ammonolysis of amorphous oxide precursors. The nitrogen-rich oxide nitrides with variable anion composition and the nitride TaZrN3 crystallize in the cubic bixbyite-type structure (space group Ia3). The nitrogen content of these compounds has a significant influence on the cell parameters, the atomic positions, and the optical band gap. The results extend the already well-studied Ta-Zr-O-N system by new oxide nitrides in addition to the already known baddeleyite- and anosovite-type phases. TaZrN{sub 3} can be considered as a thermodynamically stable ternary variant of metastable Ta{sub 2}N{sub 3}.