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Sökning: L773:0925 8388 OR L773:1873 4669

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1.
  • Schmitt, T, et al. (författare)
  • Resonant soft X-ray emission spectroscopy of doped and undoped vanadium oxides
  • 2004
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 362:1-2, s. 143-150
  • Tidskriftsartikel (refereegranskat)abstract
    • Resonant soft X-ray emission (RSXE) spectra of NaV2O5, MoxV1-xO2 and V2O3 have been recorded for a series of excitation energies at resonances of the V L- and O K-absorption band. Resonant excitation allows us, firstly, to separate V 3d and O 2p projected density-of-states of the valence band and, secondly, to study charge-neutral low-energy excitations due to resonant inelastic X-ray scattering (RIXS). We found that both the V L- and the O K-emission spectra clearly show components originating from O 2p- and V 3d-states, reflecting the high degree of hybridization of the valence band in all compounds. At threshold excitation we observed that NaV2O5 spectra are dominated by RIXS whereas MoxV1-xO2 and V2O3 spectra show bandlike features, which may be due to differences in the correlation effects of the compounds. We compared the RSXE spectra with cluster model calculations, which gives a good account for NaV2O5 whereas the RSXE spectra of the other compounds show RIXS only at certain energies well above the threshold. In fact, we interpret the trend in the RSXE spectra of the MoxV1-xO2 compound system as a successive filling of the (rigid) V 3d band with increasing Mo content. (C) 2003 Elsevier B.V. All rights reserved.
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2.
  • Edvardsson, Sverker, et al. (författare)
  • The energy matrix using determinantal product states applied to Ho:YAG
  • 2000
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 303-304, s. 280-284
  • Tidskriftsartikel (refereegranskat)abstract
    • A program written in C is applied for calculations of energy levels and wavefunctions of the lanthanides or actinides. Standard non-relativistic phenomenological operators are used. Simple determinantal product states are used to form the basis set. The complete energy matrix is diagonalized with all operators interacting simultaneously thus allowing mixing of all quantum numbers. The crystal field splitting can also be studied via the standard crystal field hamiltonian as well as the magnetic field influence on the energy levels. The program is here applied to the technologically interesting trivalent ion holmium which is used to form extremely strong magnets as well as the medical eye-safe laser Ho:YAG. Both experimentally fitted and calculated self-consistent crystal field parameters are used to study the energy structure. Crystal ionic polarizabilities with electron correlation included are partly calculated. Zeeman split levels are also studied.
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3.
  • El-Mahallawy, N., et al. (författare)
  • On the reaction between aluminum, K2TiF6 and KBF4
  • 1999
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 292:1-2, s. 221-229
  • Tidskriftsartikel (refereegranskat)abstract
    • The reaction between molten Al and KBF4 and K2TiF6 was analyzed. Additions of the two salts separately, consecutively and simultaneously were made at 800 and 1000 °C. The phases formed were identified and their morphology investigated. When adding K2TiF6 emulsification of the salt occurs. Residual salt containing K, Ti, Al and O was found in addition to slag containing K, Al and O. In an emulsified region, a new globular morphology of Al3Ti-type was found. No evidence of emulsification of KBF4 was found. This implies that the two salts react individually with Al. A new morphology of AlB2, in the form of thin plates, formed presumably at the salt/aluminum interface, was also found.
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4.
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5.
  • Godlewski, M., et al. (författare)
  • Mn2+ intra-shell recombination in bulk and quantum dots of II-VI compounds
  • 2002
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 341:1-2
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Origin of a fast component of the photoluminescence (PL) decay of Mn 2+ intra-shell 4T1 ? 6A 1 transition in bulk and quantum dot structures is discussed based on the results of PL, PL kinetics and optically detected magnetic resonance experiments. It is demonstrated that a fast component of the PL decay, reported previously for quantum dot structure and related to quantum confinement effects, is also observed in bulk samples and is very much enhanced upon generation of free carriers. The appearance of this fast component of the PL decay is related to a very efficient spin cross-relaxation between localized spins of Mn ions and spins of free carriers. © 2002 Elsevier Science B.V. All rights reserved.
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6.
  • Hillert, M., et al. (författare)
  • Point defects in B2 compounds
  • 2001
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 329:02-jan, s. 208-213
  • Tidskriftsartikel (refereegranskat)abstract
    • Point defects in B2 compounds are described with a model based on the formula (A,B,Va),(B,A,Va), and results are compared with previous results from two models based on combined defects and using the formulae (A,B), (B,A), and (A,Va)(1) (B,A)(1) The comparison is straight-forward close to the stoichiometric composition but not closer to the pure elements. Using the more general model, it is demonstrated that the fact that vacancies are the predominant defect in some B2 compounds with a small excess of B atoms depends primarily on interactions between next-nearest neighbours rather than on a high enthalpy of formation of the compound, as proposed earlier.
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7.
  • Hillert, Mats (författare)
  • The compound energy formalism
  • 2001
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 320:2, s. 161-176
  • Tidskriftsartikel (refereegranskat)abstract
    • The compound energy formalism for solution phases with sublattices is very flexible and thermodynamic models for a large variety of phases have been constructed within this formalism. The range of applications is reviewed and the methods of handling various problems are examined. Recent developments including treatments of short range order within the compound energy formalism are reviewed.
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8.
  • Kiros, Yohannes, et al. (författare)
  • Effect and characterization of dopants to Raney nickel for hydrogen oxidation
  • 2003
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 360:02-jan, s. 279-285
  • Tidskriftsartikel (refereegranskat)abstract
    • Raney nickel and its alloys with the transition metals were prepared and investigated as gas diffusion electrodes for the hydrogen oxidation reaction (HOR) in 6 M KOH and at 60degreesC. The spongy Raney nickel prepared by a mixture of Ni and Al with a weight ratio of 1: 1 was compared for the catalytic activity as hydrogen electrodes with other alloy formations containing 2 wt.% of Cu, Fe, Cr, Ti and La. Depending on the composition of the active layer, the electrocatalytic activity of the Raney nickel was found to decrease in a descending order of the doped metals: Cr>La>Ti>Cu>Fe and with no admixture. The catalytic response of the electrodes, especially for the Cr and Ti-based Raney Ni showed high enrichment and aggregation on the surface and hence affects the activity and stability. Surface area, particle size. average pore diameter, particle morphology and surface elements of the various alloy combinations, have been analyzed and assessed using BET-specific surface areas, SEM and EDXS.
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9.
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10.
  • Lyubimtsev, A. L., et al. (författare)
  • The structure and bonding of Ni3Sn
  • 2002
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 340:02-jan, s. 167-172
  • Tidskriftsartikel (refereegranskat)abstract
    • The electronic structure of Ni3Sn was calculated at ab initio levels for the crystal structure of the low-temperature modification of Ni3Sn refined upon data of single-crystal X-ray diffractometry (P6(3)/mmc, a=5.2950(7), c=4.247(1) Angstrom R=0.0288). The calculations were made with the use of fixed Gaussian (CRYSTAL98 software) and energy-dependent (Stuttgart TB-LMTO-ASA software) basis sets. Difference electron charge density maps were analysed and compared with that of a hypothetical hcp Ni in order to understand bonding in Ni3Sn. It was found that bonding in Ni3Sn has multicentre character with Ni-Sn interaction stronger than Ni-Ni one.
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11.
  • Mao, Huahai, et al. (författare)
  • Volumetric properties and phase relations of silica - thermodynamic assessment
  • 2001
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 327:1-2, s. 253-262
  • Tidskriftsartikel (refereegranskat)abstract
    • Taking into account various available experimental data, an improved internally consistent data set for the SiO2 system is obtained by thermodynamic assessment. The volumetric properties for SiO2 polymorphs are reassessed using the CALPHAD method. A two-coefficient expression is used to describe the thermal expansion and bulk modulus. For liquid phase, one equation is achieved in the temperature range of 298-4000 K either for thermal expansion or for bulk modulus. Phase diagrams have been calculated up to 40 GPa. It has been concluded that, in the pressure range lower than 20 GPa, there is no significant difference between the phase diagrams calculated by the Birch-Murnaghan equation of state (EOS) and by Murnaghan EOS.
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12.
  • Nilsson, Göran, et al. (författare)
  • X-ray powder diffraction and high-resolution electron microscopy studies of new intergrowth compounds between Ba(Nb,Zr)O3 and NbO
  • 2001
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 314:1-2, s. 67-77
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of Ba2Nb5O9 can be described as intergrown layers of perovskite (BaNbO3) and NbO. The compound is a member of the BanNbn+3mO3(n+m) homologous series where n and m are the perovskite and NbO slab widths, respectively. The substitution of Zr for Nb according to the formula Ba2Nb5−xZrxO9 has been investigated. The increase of the c axis length as a function of the overall composition shows, in combination with microanalysis in scanning and transmission electron microscopes, that the maximum value of x is approximately 0.6. The microanalysis indicates that Zr prefers the MO6 octahedra in the perovskite slab. The X-ray powder diffraction (XRD) analysis and high-resolution electron microscopy (HREM) images show that for 0.6≤x≤1.5 a disordered intergrowth of Ba(Nb;Zr)O3 and NbO layers is formed. The XRD patterns and microanalyses of cation content showed that a new homologue Ba3(Nb,Zr)6O12 with n:m=3:1 in the series Ban(Nb;Zr)n+3mO3(n+m) is formed in some of these samples. It has the unit cell parameters a=4.1725(6) Å and c=16.429(3) Å and crystallises in space group P4/mmm, Z=1. The structure of this compound was determined by comparing simulated and experimental HREM images.
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13.
  • Nilsson, Mattias, et al. (författare)
  • Synthesis, structural characterisation and magnetic properties of Gd14W4O33-xNy(0<=x<=17+/-2, 0<=y<=9+/-2), a new fluorite-related oxynitride
  • 1996
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 240:1-2, s. 60-69
  • Tidskriftsartikel (refereegranskat)abstract
    • A series of crystalline Gd-W oxides, with Gd:W ratios spanning the values 0.1-3.5, has been prepared and treated with a flow of NH3(g) in the temperature range 700-1100 degrees C. Besides the previously reported formation of GdWO3N and Gd2WO3N2, the following new results were obtained: (i) cubic Gd0.1WO3 upon ammonolysis forms an (oxy)nitride Gd0.1W(O,N)(y) with an f.c.c. lattice; (ii) the previously described Gd2WO3N2 exhibits a solid solubility range Gd3-xW1+x(O,N)(y) with, approximately, 0 less than or equal to x less than or equal to 1; (iii) ammonolysis of Gd14W4O33 yields an oxynitride, the composition of which varies with the synthesis temperature according to Gd14W4O33-xNy(O less than or equal to x less than or equal to 17+/-2, 0 less than or equal to y less than or equal to 9+/-2). All strong diffraction lines, including those of the pure oxide (x = y = 0), can be indexed with a body-centred monoclinic unit cell derived from that of fluorite. For Gd14W4O33 the cell 3 parameters are a = 5.3592(11), b = 3.7295(7), c = 3.8636(8) Angstrom, beta = 92.170(2)degrees and V = 77.17 Angstrom(3). However, strong superstructure reflections in the electron diffraction patterns indicate that the true unit cell is considerably larger. A partial structure determination of Gd14W4O33-xNy has been carried out by the Rietveld method. Magnetic susceptibility measurements in the temperature interval 15-300 K show a Curie-Weiss law behaviour for Gd14W4O33-xNy, with mu(eff) = 8.08+/-0.06 Bohr magntons per Gd3+ and theta = -12.4+/-1.1 K for all compositions.
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14.
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15.
  • Svensson, Gunnar, 1960-, et al. (författare)
  • Studies on Ba2Nb5−xTixO9 (0≤x≤1.75)
  • 1997
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 248:1-2, s. 33-41
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of Ba2Nb5O9 can be described as an intergrowth between perovskite- (BaNbO3) and NbO-type slabs. The substitution of Ti for Nb according to the formula Ba2Nb5−xTixO9 (0.00≤x≤1.75) has been investigated. The decrease in unit cell parameters as a function of overall composition determined by microanalysis shows the maximum value of x to be around 0.9. At higher x values increasing amounts of BaNb1−xTixO3 and Nb were found. Rietveld refinements of the structure using X-ray powder diffraction data show Ti to prefer Nb positions in the perovskite slab (NbO6 octahedra) and the Nb positions in the NbO slab closest to the perovskite slabs. This latter Nb is five-fold coordinated by oxygen atoms, forming a square pyramid. The third Nb position, in the middle of the NbO slab with a square planar coordination of oxygen atoms, remains undoped. The electrical resistivity and magnetic susceptibility of the x = 0.0, 0.25, 0.50 and 0.75 samples were measured. All samples were found to be metallic conductors and temperature-independent paramagnetic.
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16.
  • Tyutyunnik, A P, et al. (författare)
  • Rietveld refinement studies of Nb4N5- and Nb5N6-related phases in the (Mn)-Nb-O-N system
  • 1998
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 278:1-2, s. 83-91
  • Tidskriftsartikel (refereegranskat)abstract
    • The structures of two Nb and two Mn–Nb (oxy)nitrides have been refined from Cu Kα1 powder diffractometer data by the Rietveld method and have been characterised by electron diffraction. The phases Nb3.49N4.56O0.44 and Mn0.54Nb3.07N4.40O0.60 have structures related to that of Nb4N5, an NaCl type with ordered metal vacancies. Refinements in space group I4/m, with RF=1.3% and 1.1%, respectively, have shown that they are disordered and that metal atoms partially occupy both the nominally filled 8h position and the nominally empty 2a position in the Nb4N5 type. The observed bond lengths indicate that the 2a position is occupied only by Mn atoms in Mn0.54Nb3.07N4.40O0.60. The Nb5N6 type structure of Nb5(N,O)6 and the related structure of MnNb2(N,O)3 has been refined in space group P63/mcm to RF=1.5% and 2.9%, respectively. In the latter, the trigonal prism sites 6g are found to be occupied only by Nb, the octahedral 4d sites by approximately equal amounts Mn and Nb and the octahedral 2a site, empty in the Nb5N6 type structure, only by Mn. The Nb (oxy)nitride structures exhibit short Nb–Nb distances which indicates localised bonding between Nb atoms. Magnetic susceptibility and electrical conductivity measurements of the tetragonal phases at 15–300 K show, respectively, small magnetic moments which are coupled in an antiferromagnetic manner at low temperatures and poor, nearly temperature-independent, conductivities.
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17.
  • Vennström, Marie, et al. (författare)
  • Phase relations in the Ti3Sn–D system
  • 2004
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 364:1-2, s. 127-131
  • Tidskriftsartikel (refereegranskat)abstract
    • Ti3Sn forms an orthorhombic metal hydride phase at 25-kPa deuterium pressure and 650 °C. The unit cell parameters were determined to be a=6.179(1) Å, b=9.877(2) Å and c=4.7898(6) Å and the space group to beC2221. The crystal structure was determined from neutron powder diffraction data with the Rietveld method. Three phases are formed in the Ti3Sn–D system upon hydrogenation, and appear in the following order at increasing deuterium pressures: an orthorhombic structure (Ti3SnD0.80), a hexagonal phase and a cubic metal hydride phase (Ti3SnD). The cubic phase, Ti3SnD, crystallises in the CaTiO3-type structure, space group Pm3m, with the unit cell parameter a=4.1776(2) Å. The stability of the three Ti3SnDx phases is in agreement with calculated total energies, based on first principles theory.
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18.
  • Wang, Z. W., et al. (författare)
  • The melting of corundum (Al2O3) under high pressure conditions
  • 2000
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 299:1-2, s. 287-291
  • Tidskriftsartikel (refereegranskat)abstract
    • We have developed a simple model to address the melting of corundum (Al2O3). For this simple model, a critical volume representative for the melting point was determined, and by employing the relation between thermal pressure and temperature, the melting point of corundum at high pressure conditions can be obtained. This study indicates that a good agreement exists between our calculation, experimental results, and two-phase molecular dynamics simulations for corundum (Al2O3).
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19.
  • Wei, L.Y., et al. (författare)
  • Solidification behaviour of Mg-Al-rare earth alloys
  • 1996
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 232:1-2, s. 264-268
  • Tidskriftsartikel (refereegranskat)abstract
    • Solidification paths and as-cast microstructures were determined for the Mg-Al-MM (misch metal) alloys: AE21, AE41 and AE91. Two types of interdendritic phase were identified using analytical electron microscopy. These were Al4MM and Al12Mg17. Only Al4MM was found in AE21 while both phases were found in the other two alloys. Most of the solidification in AE21 takes place in a rather narrow solidification gap (approx.40°C), while this gap is much greater (approx. 150°C) in the higher Al alloys. This combined with the large volume fraction of interdendritic eutectic phases explains the good castability of AE91
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20.
  • Zhang, Zongyin, et al. (författare)
  • Fe-Mn-Si master alloy steel by powder metallurgy processing
  • 2004
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 363:02-jan, s. 194-202
  • Tidskriftsartikel (refereegranskat)abstract
    • Fe-Mn-Si master alloy powders were produced by three methods: milling, atomising, and a combination of atomisation and milling. The effects of sintering temperature, time and atmosphere on the properties of sintered steels with these Fe-Mn-Si master alloy powders were studied. The density of the compacts increases with sintering temperature and time. The ultimate tensile strength and hardness increases with sintering temperature and time mainly due to increasing amounts of bainite and martensite after cooling. Elongation is initially raised with sintering temperature and time probably due to improved bonding between powder particles. The compacts with the milled and atomised-milled master alloy showed about the same mechanical properties. On the other hand, the steel with the atomised powder gave lower strength and elongation in both hydrogen and argon-5% hydrogen. Small dimensional changes have been obtained in the steels with milled and atomised-milled Fe-Mn-Si master alloys sintered at 1200degreesC. It was shown that transient liquid phase sintering accelerates the sintering process, which leads to improved mechanical properties.
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21.
  • ZUBKOV, VG, et al. (författare)
  • SYNTHESIS, HIGH-RESOLUTION ELECTRON-MICROSCOPY AND CRYSTAL-STRUCTURE REFINEMENT OF THE CLUSTER COMPOUND BA3NB16O23 BY X-RAY AND NEUTRON-DIFFRACTION
  • 1994
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 203, s. 209-216
  • Tidskriftsartikel (refereegranskat)abstract
    • Ba3Nb16O23 was prepared by reducing a mixture of BaCO3 and Nb2O5 with acetylene soot under vacuum at 1550-1600-degrees-C. The structure was determined from high resolution electron microscopy images and was refined by the Rietveld technique using X-ray and neutron powder diffraction data. The unit cell parameters are a = 20.9301(4) angstrom, b = 12.4785(3) angstrom and c = 4.1619(1) angstrom, space group Cmmm, Z = 2. The crystal structure can be described as an intergrowth of BaNbO3 and NbO. Characteristic building units are quadruple chains of corner-sharing Nb6 octahedra connected via columns with a perovskite-type structure to form a three-dimensional network.
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22.
  • Åberg, Daniel, et al. (författare)
  • The crystal dependent open-shell polarizability of f-elements : higher order contributions
  • 2000
  • Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 303-304:24 May, s. 345-348
  • Tidskriftsartikel (refereegranskat)abstract
    • It has earlier been shown that the use of a self consistent multipole electrostatic model to derive the crystal field parameters (CFP) actually gives the correct curve shape when the CFP are plotted against the various rare-earth ions (S. Edvardsson, M. Klintenberg, The use of CI calculated polarizabilities to study rare-earth CFP dependencies in the laser host RE:YLF. Mater. Sci. Forum, 1999;315-317:407). It is also known that the electrostatic contribution is important for the lower order parameters. In this connection; our primary interest is to revisit this model and investigate theoretically some aspects of the dipole polarizability (alpha(D)). A few approximations were done in the earlier calculations: the treatment of unfilled shells, the neglect that also higher order terms of the type A(10)r(t)C(0)(t) contribute with t odd (not only the A(10)r(1)C(0)(1) term), correlation effects and second order contributions in perturbation theory. The solutions of the inhomogeneous Schrodinger equation are solved by a powerful numerical method. The problem is reformulated and results instead in a simple linear equation system (symmetric tridiagonal matrix) which is stable and fast to solve. The various theoretical results will be used in future applications.
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23.
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24.
  • Abbasalizadeh, A., et al. (författare)
  • Experimental investigation and thermodynamic modelling of LiF-NdF3-DyF3 system
  • 2018
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 753, s. 388-394
  • Tidskriftsartikel (refereegranskat)abstract
    • Electrolysis of molten fluorides is one of the promising methods for the recovery and recycling of rare earth metals from used magnets. Due to the dearth of phase equilibria data for molten fluoride systems, thermodynamic modelling of LiF-DyF3-NdF3 system using the CALPHAD approach was carried out. Gibbs energy modelling for LiF-NdF3 and LiF-DyF3 systems was performed using the constitutional data from literature. Ab initio calculations were used to obtain enthalpy of reaction of LiDyF4, an intermediate phase that is found to exist in the LiF-DyF3 system. Differential thermal analysis was carried out for selected compositions in the NdF3-DyF3 system, in order to determine liquidus and solidus temperatures. The Gibbs energy parameters for the limiting binaries determined in this work is used for modelling the Gibbs energy functions of equilibrium phases in the ternary system. Selected compositions of LiF-NdF3-DyF3 were subjected to DTA in order to validate the calculated phase temperatures involving melt.
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25.
  • Ahmad, Zubair, et al. (författare)
  • Fine-tuning of redox-ability, optical, and electrical properties of Bi2MoO6 ceramics via lanthanide doping and rGO integration for photo-degradation of Methylene Blue and Ciprofloxacin
  • 2024
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 1002
  • Tidskriftsartikel (refereegranskat)abstract
    • Herein, lanthanide ion (Gd+3) doped Bismuth Molybdate (Bi2MoO6) integrated on the rGO sheets has been prepared as a novel photocatalyst (Gd@Bi2MoO6/rGO) for the photocatalytic treatment of toxic pollutants. Different physiochemical, optical, electrical, thermal, and electrochemical properties of Gd@Bi2MoO6/rGO, along with its counterparts (Bi2MoO6 and Gd@Bi2MoO6) were studied through XRD, SEM/TEM, FT-IR, UV/Vis, I-V, TGA, Mott-Schottky, and EIS measurements. Photocatalytic experiments revealed that Gd@Bi2MoO6/rGO exhibited significantly enhanced photocatalytic activity, achieving 96.2 % photo-degradation of Methylene Blue with 120 min of irradiation, which is 6.5 and 3.1 times higher compared to Bi2MoO6 (40.9 %) and Gd@Bi2MoO6 (64.8 %), respectively. Moreover, Gd@Bi2MoO6/rGO demonstrated a notable photocatalytic efficiency of 81.7 % towards Ciprofloxacin, significant as per the existing literature benchmark. The enhanced photocatalytic activity is ascribed to the in-built Gd+3 redox centers, high electrical conductivity (7.35 × 10−3 S/m), favorable flat band potential (-0.81 V), and low semiconductor impedance (Rct = 51.71 Ω and Rs = 0.90 Ω). Additionally, the electron-capturing ability of lanthanide dopant ions and S-C heterojunction of Gd@Bi2MoO6/rGO facilitates the separation of photo-generated e-/h+ pairs and favors high concentrations of ROS. The results obtained highlight the potential of Gd@Bi2MoO6/rGO for applications in photocatalysis and wastewater treatment.
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26.
  • Ahmadkhaniha, Donya, et al. (författare)
  • Effect of SiC particle size and heat-treatment on microhardness and corrosion resistance of NiP electrodeposited coatings
  • 2018
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 769, s. 1080-1087
  • Tidskriftsartikel (refereegranskat)abstract
    • Electrodeposition of NiP composite coatings with nano and sub-micron sized SiC has been carried out to investigate the possibility of replacing hard chromium coatings. The composition and structure of the coatings were evaluated by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis, respectively. Microhardness was measured by Vickers indentation and polarization measurements were carried out to study the corrosion behavior of the coatings. The results showed that submicron particles can be codeposited with a higher content as compared to nano sized ones. However, even if a smaller amount of the nano-sized SiC particles are incorporated in the coating, the contribution to an increasing microhardness was comparable with the submicron sized particles, which can be related to the higher density of codeposited particles. SiC particles did not change the anodic polarization behavior of NiP coatings in a 3.5% NaCl solution. Finally, the effect of heat-treatment on the coatings properties at 400 °C for 1 h was studied to investigate the contribution of particles and heat-treatment on hardness and corrosion properties. It was found that the heat-treatment doubled the microhardness and changed the anodic polarization behavior of the coatings from passive to active with respect to the as-plated conditions.
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27.
  • Ahmed, Shahbaz, et al. (författare)
  • Accurate First-Principles Evaluation of Structural, Electronic, Optical and Photocatalytic Properties of BaHfO3 and SrHfO3 Perovskites
  • 2022
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 892
  • Tidskriftsartikel (refereegranskat)abstract
    • A reliable first-principles account of experimentally observed physical properties of perovskite oxides is crucial for realizing their employment in electronic and optical devices. In this context, SCAN meta-GGA functional of DFT offers good approximation for the exchange-correlation energy; facilitating accurate determination of structural and energetic properties. However, SCAN is unable to reproduce electronic and optical properties of wide bad gap materials. In the present study, we report systematic DFT calculations to show that structural, energetic, electronic and optical properties of hafnium based BaHfO3 and SrHfO3 perovskite oxides can be accurately determined through a combine application of SCAN and Tran-Blaha modified Becke-Johnson (TB-mBJ) meta-GGAs. The structural and energetic properties computed using SCAN functional for both BaHfO3 and SrHfO3 are found to be in good agreement with experimental data; achieving a level of accuracy comparable to computationally expansive hybrid DFT calculations. On the other hand, TB-mBJ calculated band gaps computed using the SCAN optimized lattice parameters provide better agreement with experimental data at a low computational cost. The optical properties, band edge potentials and effective masses of the charge carriers in BaHfO3 and SrHfO3 are also computed to examine the combined application of SCAN and TB-mBJ meta-GGAs in predicting the photocatalytic performance of these wide band gap materials. Our results clearly show that the combination of the two meta-GGAs provide a computationally economical route for evaluating the photocatalytic performance of alkaline-earth metal hafnates.
  •  
28.
  • Ahuja, B. L., et al. (författare)
  • A study of electron momentum density and charge transfer in W-Cu system
  • 2009
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 467:1-2, s. 595-599
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first ever Compton scattering study on WxCu1-x(x=0.60, 0.72) alloys. The Compton profile measurements have been made using 20Ci (CS)-C-137 gamma-ray source. The experimental data are compared with the superposition of APW-based Compton profiles of constituent metals. A schematic study on charge transfer has been reported using the experimental valence band Compton profiles of both the alloys, W and Cu. Our first ever data support the charge transfer from W to Cu on alloying, which is also confirmed by our band structure calculations employing exact muffin-tin orbitals method (EMTO). (C) 2007 Elsevier B.V. All rights reserved.
  •  
29.
  • Akhtar, Farid, et al. (författare)
  • Enhanced sintering, microstructure evolution and mechanical properties of 316L stainless steel with MoSi(2) addition
  • 2011
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 509:35, s. 8794-8797
  • Tidskriftsartikel (refereegranskat)abstract
    • Sintering 316L stainless steel to near full density with an appropriate sintering additive can ensure high mechanical properties and corrosion resistance. We present here a sintering approach which exploits the dissociation of ceramics in steels at high temperatures to activate sintering densification to achieve near full dense 316L stainless steel materials. MoSi(2) ceramic powder was used as a sintering additive for pre-alloyed 316L stainless steel powder. Sintering behavior and microstructure evolution were investigated at various sintering temperatures and content of MoSi(2) as sintering additive. The results showed that the sintering densification was enhanced with temperature and MoSi(2) content. The distribution of MoSi(2) was characterized by XMAPs. It was found that MoSi(2) dissociated during sintering and Mo and Si segregated at the grain boundaries. Excess Mo and Si were appeared as separate phases in the microstructure. Above 98% of theoretical density was achieved when the specimens were sintered at 1300 degrees C for 60 min with 5 wt.% MoSi(2) content. The stainless steel sintered with 5 wt.% MoSi(2) exhibited very attractive mechanical properties.
  •  
30.
  • Akhtar, Farid (författare)
  • Microstructure evolution and wear properties of in situ synthesized TiB 2 and TiC reinforced steel matrix composites
  • 2008
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 459:1-2, s. 491-497
  • Tidskriftsartikel (refereegranskat)abstract
    • Steel matrix composite reinforced with TiB2 and TiC reinforcements (30 to 70wt%) have been produced through the synthesis reaction from Ti, C and FeB. The sintered composites were characterized by X-ray diffraction and scanning electron microscopy. TiB2, TiC and steel were detected by X-ray diffraction analysis. The scanning electron micrographs revealed the morphology and distribution of the reinforcements. TiB2 and TiC were thermally stable in the steel matrix. The results showed that different mechanisms of evolution of reinforcements in steel matrix were operative. TiB2 grew in hexagonal prismatic or rectangular shape and TiC in spherical shape. The reciprocating sliding wear test was conducted on the composite. The results of sliding wear showed that the wear loss decreased with increase in the reinforcement content. The wear mechanisms were polishing wear and microploughing for the composites containing high volume fraction of the reinforcements, whereas microploughing and grooving were the dominant wear mechanisms for the composites containing low volume fraction of the reinforcements.
  •  
31.
  • Akhtar, Farid, et al. (författare)
  • Processing, microstructure and mechanical properties of TiC-465 stainless steel/465 stainless steel layer composites
  • 2007
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 439:1-2, s. 287-293
  • Tidskriftsartikel (refereegranskat)abstract
    • Layered composites of carbide reinforcements and stainless steel have been prepared successfully by powder technology. The layer material consisted of two layers. Top layer consisted of reinforcements (TiC and NbC) and 465 stainless steel as binder material for carbides. The substrate material was of binder material (465 stainless steel). The microstructure of the composite was characterized by scanning electron microscopy. The microstructural study revealed that top layer (TiC-NbC/465 stainless steel) showed the typical core-rim microstructure of conventional steel bonded cermets and the substrate material showed the structure of sintered steel. An intermediate layer was formed due to diffusion reaction of top layer and substrate material. This intermediate layer showed a gradient microstructure. The bending strength of layered material measured in the direction perpendicular to the layer alignment was remarkably higher. Nineteen percent increase in bending strength in case of 53 wt% reinforcement in top layer and 35% increase in case of 73 wt% reinforcement in top layer was found. The variation of strength as a function of thickness of substrate material revealed that the character of material changed from cermet to a layer composite and then towards metallic materials. The fracture morphologies of top layer, substrate material and intermediate layer are also reported
  •  
32.
  • Alami, J., et al. (författare)
  • High power pulsed magnetron sputtering : Fundamentals and applications
  • 2009
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 483:1-2, s. 530-534
  • Tidskriftsartikel (refereegranskat)abstract
    • Direct current magnetron sputtering (dcMS) is a widely used technique for deposition of a large number of compound and metallic coatings with specified mechanical, electrical and optical properties. Although dcMS is a successful coating technique, it suffers from fundamental problems, such as low target utilization and target poisoning during reactive sputtering, which results in process instabilities and poor deposition rates. In order to alleviate some of these problems, alternative techniques, such as radio frequency magnetron sputtering, additional ionization by rf coils or microwaves, or increased magnetic confinement by a multipolar magnetic setup are used. High power unipolar pulsing of the target voltage is another approach that has been used of late, in order to increase the ionization fraction in the discharge. in this deposition technique, known as high power pulsed magnetron sputtering (HPPMS), the power supply operates at low (or zero) power level and pulses to a high voltage for a short time each cycle. Thus, high electron densities are generated leading to increased ionization of the sputtered material. With peak power densities typically of several kW cm(-2), ionization fractions of the sputtered material ranging from 4.5% for C to 70% for Cu are achieved. HPPMS has been used to grow metallic and compound coatings. In the present work, a summary over some of the important results related to this technique are presented. The mechanisms taking place in the discharge and at the coating surface during deposition are discussed and the benefits of using HPPMS are reviewed: tailoring of coating properties, control of the coating bombardment during deposition, enhancement of the coating mechanical properties and morphology. Finally, TiAlN coatings are deposited using an industrial coater, and the coatings properties are studied.
  •  
33.
  • Allal, Adel, et al. (författare)
  • Structural stability, mechanical, electronic and optical behaviour of RbXS2 (X = Y and La) under high pressure : A first-principle study
  • 2020
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 848
  • Tidskriftsartikel (refereegranskat)abstract
    • The high-pressure behaviour of the ternary sulphides, RbXS2 (X = Y and La), has been investigated by using first-principle calculations based on density functional theory. Upon applying hydrostatic pressure, the unit-cell parameters (a, c) decrease with different rates, indicating an anisotropic axial compression. The most of RbYS2 and RbLaS2 crystals compressibility comes from Rb+1-S-2 bonds. Elastic constants and their dependence on pressure and related mechanical properties have been reported and analysed. From Pugh's criterion, RbYS2 and RbLaS2 turn from brittle to ductile material for applied pressures beyond 3.1 GPa and 2.9 GPa, respectively. Stability criteria show that RbYS2 and RbLaS2 are not mechanically stable in ci-NaFeO2 crystal structure above 20.63 GPa and 16.24 GPa, respectively. Both RbYS2 and RbLaS2 have indirect band gap, which decreases with increasing pressure. However, no indirectdirect band gap transition is observed for both materials. Finally, the calculated optical spectrum of both compounds exhibits an anisotropy and a broadening at high pressures.
  •  
34.
  • Altincekic, T. G., et al. (författare)
  • Synthesis and characterization of CuFe2O4 nanorods synthesized by polyol route
  • 2010
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 493:1-2, s. 493-498
  • Tidskriftsartikel (refereegranskat)abstract
    • Uniform, high quality, CuFe2O4 nanorods with high aspect ratios were synthesized by a surfactant-free single step polyol process at 220 degrees C. The structure of the product was characterized by XRD and FT-IR, and the morphology of the product was analyzed by SEM. The results showed that the as-prepared nanorods have a uniform cross-section and with average diameter of similar to 100 nm and aspect ratio in the range of 13-52. X-ray line profile fitting resulted in crystallite size of 15 nm, which reveals the polycrystalline nature of these nanorods. Magnetic characterization of product was performed by EPR and VSM techniques and the results show that the CuFe2O4 nanorods are ferromagnetic. The line width of the resonance lines in FMR is about 1.8 kOe which may originate from different resonance fields of randomly distributed nanocrystals which have different orientation of magnetic easy axes.
  •  
35.
  • Arvhult, Carl-M, et al. (författare)
  • Thermodynamic assessment of the Fe-Te system. Part II : Thermodynamic modeling
  • 2018
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 767, s. 883-893
  • Tidskriftsartikel (refereegranskat)abstract
    • A thermodynamic description of the Fe-Te system modeled via the Calphad method is proposed, based on data published in a preceding publication Part I: Experimental study, and that available in literature. End-member formation energies for the phases beta, beta', delta, delta' and epsilon, as well as lattice stabilities of FCC and BCC tellurium, have been evaluated via DFT and used in the numerical optimization. The final Gibbs energy models fit thermodynamic and phase diagram data well, and inconsistencies are discussed. The thermodynamic description is then used to evaluate Gibbs energy of formation for selected Fe-Te compounds of interest for the modeling of internal corrosion of stainless steel fuel pin cladding during operation of Liquid Metal-cooled Fast Reactors (LMFR).
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36.
  • Arvhult, Carl, et al. (författare)
  • Thermodynamic assessment of the Fe-Te system. Part I : Experimental study
  • 2019
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 773, s. 314-326
  • Tidskriftsartikel (refereegranskat)abstract
    • A thermodynamic description of the Fe-Te system needs to be developed in order to model internal corrosion by fission products in fuel pins of Generation IV nuclear reactors. In preparation for a thermodynamic assessment of the system, an experimental study has been performed in order to clarify some unknown or conflicting phase diagram data. New phase diagram data have been obtained using Differential Thermal Analysis and isothermal heat treatments followed by electron microscopy with EDS and WDS analysis. The DTA analysis revealed new phase boundary data, and confirmed a very steep Fe-rich liquidus, supporting the possibility of a liquid miscibility gap in the Fe-FeTe region. The analyses also confirmed the probable eutectoid reaction δ→β+δ’ at 523 °C. The invariant arrests of the unknown γ phase were consistent with information available in literature, but the phase was not identified via XRD of samples at its postulated composition. However, metallography of the samples revealed an unexpected microstructure pertaining to the δ phase, which might be the γ phase, and is discussed in this paper. The monoclinic space group C2/m is proposed for the δ phase based on XRD. The collected data will be used together with that available in literature to perform a thermodynamic Calphad assessment in a subsequent paper Part II: Thermodynamic modeling.
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37.
  • Avazkonandeh-Gharavol, M. H., et al. (författare)
  • On the microsegregation of Al-Mg alloys by thermal analysis and numerical modeling
  • 2014
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 610, s. 462-471
  • Tidskriftsartikel (refereegranskat)abstract
    • Knowledge about solid fraction versus temperature during solidification is crucial for the control of solidification processes. In the present paper solidification sequence and path of Al-Mg binary alloys containing 6.7 and 10.2 wt.% Mg was investigated by a series of DTA and quenching experiments and numerical modeling in 0.5 and 5 K min(-1) cooling rates. Experimental results show that at both cooling rates, Al-6.7 wt.% Mg solidifies with a single phase structure, but Al-10.2 wt.% Mg solidifies with a two phase structure. According to the results of numerical modeling, good agreement between calculated solidification curves and experimental solid fractions, but poor correlation with concentration profiles. The source of discrepancies is discussed according to different theories of microsegregation.
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38.
  • Aydin, M., et al. (författare)
  • Synthesis, magnetic and electrical characteristics of poly(2-thiophen-3-yl-malonic acid)/Fe(3)O(4) nanocomposite
  • 2012
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 514, s. 45-53
  • Tidskriftsartikel (refereegranskat)abstract
    • Poly(2-thiophen-3-yl-malonic acid)/Fe(3)O(4) nanocomposite was synthesized by the precipitation of Fe(3)O(4) in the presence of poly(2-thiophen-3-yl-malonic acid) (PT3MA). Characterizations of the nanocomposite were performed by XRD, FT-IR, TEM, TGA, AC/DC conductivity and dielectric measurements. The capping of PT3MA around Fe(3)O(4) nanoparticles was confirmed by FTIR spectroscopy, the interaction being between bridging oxygen of the carboxylate and the nanoparticle surface through bidentate binding. The crystallite particle sizes of 6 +/- 3 nm and 7 +/- 3 nm were obtained from XRD line profile fitting and from TEM image analysis respectively, and they are in good agreement with each other. Magnetization measurements revealed that PT3MA coated magnetite particles do not saturate at higher fields. The material showed superparamagnetic character as revealed by the absence of coercivity and remnant magnetization. Magnetic particle size was calculated as 7.3 +/- 1.0 nm from the mean magnetization term in the Langevin function which is also in conformity with the values determined from TEM micrographs and XRD line profile fitting. The TEM particle size analysis of the nanoparticles revealed the presence of a slightly modified magnetically dead nanoparticle surface. AC and DC conductivity measurements were performed to elucidate the electrical conduction characteristics of the product.
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39.
  • Azdouz, M., et al. (författare)
  • Crystal chemistry, Rietveld refinements and Raman spectroscopy studies of the new solid solution series: Ba3−xSrx(VO4)2 (0≤x≤3)
  • 2010
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 498:1, s. 42-51
  • Tidskriftsartikel (refereegranskat)abstract
    • The new solid solution series Ba3-xSrx(VO4)(2) (0 <= x <= 3) has been synthesized and studied by a combination of X-ray powder diffraction and Raman vibrational spectroscopy. This continuous solid solution crystallise in the hexagonal system with R (3) over barm space group. The structure has been determined at room temperature from X-ray diffraction by the Rietveld method analysis. It is formed by a 3D network of (Ba/Sr)((1))(VO4)(2)(4-) layers linked into a crystal network by (Ba/Sr)(2+)((2)) cations. The vibrational spectra of this crystalline orthovanadate solid solution series are interpreted by means of factor group analysis in terms of space group R (3) over barm (D-3d(5)). Assignments of the V-O vibrational stretching and bending modes, as well as some of the external modes, have been made. While all the modes show a monotonous shift as a function of the composition x, a break in the curves of intensities, full width at half maximum and band areas as a function of x is observed and attributed to the statistical distribution of Ba and Sr ions in the same crystallographic sites.
  •  
40.
  • Azofeifa, D. E., et al. (författare)
  • Hydrogen induced changes in the optical properties of Pd capped V thin films
  • 2013
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 580:Suppl. 1, s. S114-S118
  • Tidskriftsartikel (refereegranskat)abstract
    • Optical properties of 50 nm thick single crystal vanadium films deposited on double side polished MgO substrates have been obtained from spectrophotometric measurements. The films were coated with a polycrystalline Pd layer (5 nm thick) to protect them from oxidation and to favor absorption of atomic hydrogen. Electrical resistance was recorded while hydrogen pressure was increased slowly up to 750 mbar keeping temperature constant. Simultaneously, under normal incidence of non-polarized radiation [350-950 nm], transmittance spectra of this Pd/V/MgO system were measured. These were numerically inverted to obtain the spectral behavior of the Pd, V. PdHy, and VHx dielectric functions at 22 and 140 degrees C, and at 750 mbar. Hydrogen concentration in V film was first determined from a resisto-optical method. Finally, we demonstrate the possibility to determine the concentration in the Pd and the V layers independently, solely using the changes in the optical transmission. 
  •  
41.
  • Babizhetskyy, V., et al. (författare)
  • Investigation in the ternary Ta-Ni-P system : Solid state phase equilibria at T=1070 K, crystal and electronic structures of new ternary phosphides
  • 2021
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 864
  • Tidskriftsartikel (refereegranskat)abstract
    • The solid state phase diagram for the ternary Ta-Ni-P system was established at T=1070 K in the region of up to 67 at% of P by means of X-ray powder diffraction methods (PXRD). Six ternary compounds, namely Ta4NiP (Nb4CoSi-type), Ta1.10-0.82Ni0.90-1.18P (TiNiSi-type), TaNiP2 (NbNiP2-type), Ta(5.00-4.81)Ni(4.00-4.19)P4 (Nb5Cu4Si4-type), TaNi2P (own structure type) and Ta1-0.08(1)Ni0.08(1)P2 (OsGe2-type) have been confirmed to exist. Rather minor Ta/Ni homogeneity ranges have been found for alpha-Ta3-xNixP (x=0.2) (Ti3P-type), Ta1-xNixP (x=0.18) (NbAs-type), Ni3-xTaxP (x=0.2) (Ni3P-type) and Ni2-xTaxP (x=0.25) (Fe2P-type). The crystal structure of Ta4.811(9)Ni4.189(9)P4 has been refined from single crystal X-ray diffraction data (Nb5Cu4Si4-type, space group I4/m, a =9.8474(17), c=3.5182(7) angstrom, R1=0.0283, wR2=0.0470), while that of the new TaNi2P compound was determined by means of PXRD. This phosphide crystalizes in its own structure type (space group Pnma, a=8.3588(3), b=3.5208(1), c=6.7051(3) angstrom, R-I=0.044, R-P=0.161). A new isostructural Fe-compound, TaFe2P (a=8.358(2), b=3.5194(7), c=6.703(1) angstrom), was also synthetized. The electronic structures of Ta5Ni4P4 and TaNi2P were analyzed using the tight-binding linear muffin-tin orbital (TB-LMTO) and extended Huckel methods.
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42.
  • Baranovskiy, A. E., et al. (författare)
  • Electronic structure, bulk and magnetic properties of MB6 and MB12 borides
  • 2007
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 442:1-2, s. 228-230
  • Tidskriftsartikel (refereegranskat)abstract
    • The bulk and magnetic properties of MB6 and MB12 were investigated on the basis of first principles electronic structure calculations. The elastic constants were measured for ZrB12, HoB12, ErB12, TmB12, LuB12, YB6 and LaB6 compounds at low temperatures. The calculated equations of states and balanced crystal orbital overlap populations have allowed to analyse bonding and magnetic properties of MB6 and MB12 .
  •  
43.
  • Barrirero, Jenifer, et al. (författare)
  • Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy
  • 2014
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 611, s. 410-421
  • Tidskriftsartikel (refereegranskat)abstract
    • The mechanical properties of Al-7 wt.% Si can be enhanced by structural modifications of its eutectic phase. Addition of low concentrations of certain elements, in this case 150 wt-ppm Sr, is enough to cause a transition from a coarse plate-like Si structure to a finer coralline one. To fully understand the operating mechanism of this modification, the composition of the eutectic Si phase in unmodified and Sr-modified alloys was analysed and compared by atom probe tomography and (scanning) transmission electron microscopy. The unmodified alloy showed nanometre sized Al-segregations decorating defects, while the Sr-modified sample presented three types of Al-Sr segregations: (1) rod-like segregations that promote smoothening of the Al-Si boundaries in the eutectic phase, (2) particle-like segregations comparable to the ones seen in the unmodified alloy, and (3) planar segregations favouring the formation of twin boundaries. Al and Sr solubilities in Si after solidification were determined to be 430 +/- 160 at-ppm and 40 +/- 10 at-ppm, respectively. Sr predominantly segregates to the Si phase confirming its importance in the modification of the eutectic growth.
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44.
  • Bayat, Nazlin, et al. (författare)
  • In-Situ Study of Phase Transformations during Homogenization of 6005 and 6082 Al Alloys
  • 2017
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 725, s. 504-509
  • Tidskriftsartikel (refereegranskat)abstract
    • Intermetallic β-Al5FeSi phase and coarse Mg2Si particles have negative effects on extrudability and workability of 6xxx Al alloy billets. To achieve extruded products with a high surface quality as-cast billets are therefore heat-treated before extrusion. During heat treatment the undesired intermetallic particles, i.e., β-AlFeSi platelets, are transformed to a rounded α-Al(FeMn)Si intermetallic phase. This transformation was studied in-situ by TEM for 6005 and 6082 Al alloys. It was observed that the Mg2Si particles precipitate in the Al matrix at about 250 °C; this precipitation also occurred at the edge and faces of beta intermetallic particles, and the Mg2Si particles were the preferred sites for α-Al(FeMn)Si particle nucleation. The transformation proceeded faster and at lower temperatures, 350–450 °C, than what has been reported earlier for homogenization studies of bulk samples and industrial billets. This could be associated with the thin characteristic of used samples in TEM giving contribution from fast surface diffusion, but it was also concluded that the phase boundary layer diffusion was important for the understanding of how the transformations proceed.
  •  
45.
  • Baykal, A., et al. (författare)
  • Polyol synthesis of (polyvinylpyrrolidone) PVP-Mn3O4 nanocomposite
  • 2010
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 502:1, s. 199-205
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the synthesis of (polyvinylpyrrolidone) PVP-Mn3O4 nanocomposite via a polyol route. Crystalline phase was identified as Mn3O4 and the crystallite size was obtained as 6 +/- 1 nm from X-ray line profile fitting. Average particle size of 6.1 +/- 0.1 nm obtained from TEM analysis reveals nearly single crystalline nature of these nanoparticles in the composite. The capping of PVP around Mn3O4 nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carbonyl (C=O) and the nanoparticle surface. T-C and T-B for PVP-Mn3O4 nanocomposite were observed at 42K and 28.5 K, respectively. The sample has hysteresis with small coercivity and remanent magnetization at 40K, resembling the superparamagnetic state. ac conductivity measurements on PVP-Mn3O4 nanocomposite revealed a conductivity in the order of 10(-7) S cm(-1) at lower frequencies. The conductivity change with respect to frequency can be explained by electronic exchange occurring between Mr(+2) and Mn+3 existing in sublattice of spinel lattice.
  •  
46.
  • Belov, M P, et al. (författare)
  • Ab initio lattice dynamics of CoH and NiH
  • 2011
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 509, s. S857-S859
  • Tidskriftsartikel (refereegranskat)abstract
    • Ground state parameters and lattice dynamics of CoH and NiH phases are studied by means of the state-of-the-art ab initio pseudopotentials methods. Calculated ground state parameters and phonon DOS are in rather good agreement with available experimental data. No phase transformation for CoH and NiH was found in a wide pressure and temperature range.
  •  
47.
  • Bhardwaj, Anand, et al. (författare)
  • Auto tunable hyperthermic response of temperature sensitive magnetic fluid in agarose gel containing Mn1−xZnxFe2O4 nanoparticles
  • 2024
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 978
  • Tidskriftsartikel (refereegranskat)abstract
    • The present study reports the synthesis and physico-chemical characterization of Mn1−xZnxFe2O4 (x = 0.5, 0.4, 0.3, 0.2, 0.1) nanoparticles-based magnetic fluids with reference to magnetic fluid hyperthermia. The properties of these fluids are studied using XRD, FTIR, TGA, VSM and the induction heating equipment operated at 330 kHz. The heating response of the fluids is investigated within the safety limit of H·f (4.8 *108 A/m-s). The study is also extended to simulate it for the agarose gel phantom system. The power absorption by these samples in distilled water and in agarose gel is calculated to compare with the experimentally observed value. To the best of the author's knowledge, no study of temperature sensitive magnetic fluid is reported on agarose gel, which simulates or phantom an in vivo condition. Results analysis show that the control of hyperthermia temperature is possible at lower fields and frequencies for the A91 sample with the smallest possible concentration, which can be acceptable for in vitro study.
  •  
48.
  • Birsoz, B., et al. (författare)
  • Synthesis and characterization of polypyrrole-BaFe12O19 nanocomposite
  • 2010
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 493:1-2, s. 481-485
  • Tidskriftsartikel (refereegranskat)abstract
    • Polypyrrole-BaFe12O19 nanocomposite was successfully synthesized by an in situ polymerization of pyyrole in the presence of synthesized BaFe12O19 nanoparticles. Structural, morphological, electrical and magnetic properties of the nanocomposite were performed by XRD, FT-IR, TEM, TGA, VSM and ac conductivity measurements respectively. XRD analysis reveals the inorganic phase as bariumhexaferrite and TGA shows about 22 wt% loading of hexaferrite in the nanocomposite. FT-IR analysis indicates a successful conjugation of hexaferrite particles with polypyrrole. Magnetization measurements show that polypyrrole coating decreases the saturation magnetization of BaFe12O19 significantly. This reduction has been explained by the pinning of the surface spins by the possible adsorption of non-magnetic ions during the polymerization process. Interactions between the hard and impurity phases, determined using the Stoner-Wohlfarth theory, reveal that particles' single domain character and the coating destabilizes the remanence state of the polypyrrole-BaFe12O19 nanocomposite.
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49.
  • Boeije, M. F. J., et al. (författare)
  • On the phase stability of CaCu5-type compounds
  • 2017
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 722, s. 549-554
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a hybrid method to inspect the phase stability of compounds having a CaCu5-type crystal structure. This is done using 2D stability plots using the Miedema parameters that are based on the work function and electron density of the constituent elements. Stable compounds are separated from unstable binary compounds, with a probability of 94%. For stable compounds, a linear relation is found, showing a constant ratio of charge transfer and electron density mismatch. DFT calculations show the same trend. Elements from the s, d, f-block are all reliably represented, elements from the p-block are still challenging.
  •  
50.
  • Brennhaugen, David D. E., et al. (författare)
  • Predictive modeling of glass forming ability in the Fe-Nb-B system using the CALPHAD approach
  • 2017
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 707, s. 120-125
  • Tidskriftsartikel (refereegranskat)abstract
    • Accurate values needed for the most commonly used indicators of good Glass Forming Ability (GFA) in alloys, i.e. the liquidus (T-l), crystallization (T-x) and glass transition (T-g) temperatures, are only available after successful production of the metallic glass of interest. This has traditionally made discovery of new metallic glasses an expensive and tedious procedure, based on trial-and-error methodology. The present study aims at testing the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) approach for predicting GFA in the Fe-Nb-B system by the use of the Thermo-Calc software and the thermodynamic database TCFE7. The melting temperatures and phase stabilities were calculated and combined with data for an atomic size mismatch factor, lambda, in order to identify and map potential high-GFA regions. Selected compositions in the identified regions were later produced by suction casting and melt spinning, and the potential success verified using X-Ray Diffraction (XRD). Differential Scanning Calorimetry (DSC) was also used to compare thermodynamic calculations for the model predictions, and evaluate standard GFA indicators. The model is found to fit well with literature data, as well as predict new bulk glassy compositions at and around Fe70.5Nb7B22.5. These results show promise in further predictive use of the model.
  •  
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