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  • 1. Abbasalizadeh, A.
    et al.
    Sridar, S.
    Chen, Z.
    Sluiter, M.
    Yang, Y.
    Sietsma, J.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hari Kumar, K. C.
    Experimental investigation and thermodynamic modelling of LiF-NdF3-DyF3 system2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 753, p. 388-394Article in journal (Refereed)
    Abstract [en]

    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.

  • 2. Altincekic, T. G.
    et al.
    Boz, I.
    Baykal, A.
    Kazan, S.
    Topkaya, R.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Synthesis and characterization of CuFe2O4 nanorods synthesized by polyol route2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 493, no 1-2, p. 493-498Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Arvhult, Carl-M
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Gueneau, C.
    Univ Paris Saclay, DEN, SCCME, CEA, F-91191 Gif Sur Yvette, France..
    Gosse, S.
    Univ Paris Saclay, DEN, SCCME, CEA, F-91191 Gif Sur Yvette, France..
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermodynamic assessment of the Fe-Te system. Part II: Thermodynamic modeling2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 767, p. 883-893Article in journal (Refereed)
    Abstract [en]

    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).

  • 4. Avazkonandeh-Gharavol, M. H.
    et al.
    Haddad-Sabzevar, M.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    On the microsegregation of Al-Mg alloys by thermal analysis and numerical modeling2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 610, p. 462-471Article in journal (Refereed)
    Abstract [en]

    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.

  • 5. Aydin, M.
    et al.
    Unal, B.
    Esat, B.
    Baykal, A.
    Karaoglu, E.
    Toprak, Muhammet Sadaka
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Sozeri, H.
    Synthesis, magnetic and electrical characteristics of poly(2-thiophen-3-yl-malonic acid)/Fe(3)O(4) nanocomposite2012In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 514, p. 45-53Article in journal (Refereed)
    Abstract [en]

    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.

  • 6. Baykal, A.
    et al.
    Bitrak, N.
    Ünal, B.
    Kavas, H.
    Durmus, Z.
    Özden, S.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Polyol synthesis of (polyvinylpyrrolidone) PVP-Mn3O4 nanocomposite2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 502, no 1, p. 199-205Article in journal (Refereed)
    Abstract [en]

    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.

  • 7. Birsoz, B.
    et al.
    Baykal, A.
    Sozeri, H.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Synthesis and characterization of polypyrrole-BaFe12O19 nanocomposite2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 493, no 1-2, p. 481-485Article in journal (Refereed)
    Abstract [en]

    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.

  • 8. Brennhaugen, David D. E.
    et al.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Louzguine-Luzgin, Dmitri V.
    Arnberg, Lars
    Aune, Ragnhild E.
    Predictive modeling of glass forming ability in the Fe-Nb-B system using the CALPHAD approach2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 707, p. 120-125Article in journal (Refereed)
    Abstract [en]

    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.

  • 9. Cao, Xiaohua
    et al.
    Cao, Xiaoling
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Zhang, Qing
    Nanoscale indentation behavior of pseudo-elastic Ti-Ni thin films2008In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 465, no 1-2, p. 491-496Article in journal (Refereed)
    Abstract [en]

    48.28 at.%Ti-51.72 at.%Ni thin films were prepared by magnetron sputtering and post-annealed at 450, 500, 550 and 600 degrees C, respectively. The evolution of structure, phase transformation and nanoscale indentation behavior of Ti-Ni thin film annealed at different temperature were investigated by X-ray diffractometer (XRD), differential scanning calorimetry (DSC) and nanoindention test, respectively. The results showed that the as-deposited Ti-Ni thin films were amorphous and crystallized after post-annealing. As the annealing temperature increased from 450 to 600 degrees C, both the content of parent phase (B2) and that of the precipitate phase (Ni4Ti3) increased. Both the phase transformation temperature and the micro-hardness of the annealed Ti-Ni thin films increased as well. Meanwhile, the pseudo-elasticity energy recovery ratio 77 first increased to the maximum value and then decreased with the increasing annealing temperature. It revealed that the annealed Ti-Ni thin film specimens exhibited the highest pseudo-elasticity degree with the largest 71 values under the load of 10 mN.

  • 10. Cedervall, Johan
    et al.
    Andersson, Mikael Svante
    Sarkar, Tapati
    Delczeg-Czirjak, Erna K.
    Bergqvist, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Hansen, Thomas C.
    Beran, Premysl
    Nordblad, Per
    Sahlberg, Martin
    Magnetic structure of the magnetocaloric compound AlFe2B22016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 664, p. 784-791Article in journal (Refereed)
    Abstract [en]

    The crystal and magnetic structures of AlFe2B2 have been studied with a combination of X-ray and neutron diffraction and electronic structure calculations. The magnetic and magnetocaloric properties have been investigated by magnetisation measurements. The samples have been produced using high temperature synthesis and subsequent heat treatments. The compound crystallises in the orthorhombic crystal system Cmmm and it orders ferromagnetically at 285 K through a second order phase transition. At temperatures below the magnetic transition the magnetic moments align along the crystallographic a-axis. The magnetic entropy change from 0 to 800 kA/m was found to be - 1.3 J/K kg at the magnetic transition temperature.

  • 11.
    Chen, Kaixuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Chen, Xiaohua
    Univ Sci & Technol Beijing, State Key Lab Adv Met & Mat, Beijing 100083, Peoples R China..
    Wang, Zidong
    Univ Sci & Technol Beijing, Sch Mat Sci & Engn, Beijing 100083, Peoples R China..
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology. KTH, School of Industrial Engineering and Management (ITM), Centres, Brinell Centre - Inorganic Interfacial Engineering, BRIIE.
    Optimization of deformation properties in as-cast copper by microstructural engineering. Part I. microstructure2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 763, p. 592-605Article in journal (Refereed)
    Abstract [en]

    The microstructural features required to optimize both the strength and ductility of copper are investigated by examining the as-cast pure Cu and Cu-(1.0e3.0)Fe-0.5Co and Cu-1.5Fe-0.1Sn (wt %) alloys. Uniaxial tensile tests show that (Fe, Co)- or (Fe, Sn)-doping improves both the strength and ductility of pure copper. The microstructure evolution with Fe, Co, or Sn doping is characterized by using optical and scanning and transmission electron microscopies. The effects of Fe, Co, and Sn doping on the microstructure clearly show that (i) iron-rich nanoparticles are dispersed inside the grains. The spherical nanoparticles grow in size with increasing Fe content, and when the Fe content exceeds 2.0 wt %, the particles transition into a petal-like morphology. (ii) The microstructure of the alloys (grain size and morphology) is notably influenced by the Fe and Co contents, and the grain size is reduced from an average of 603 mu m in pure Cu to an average of 26 mm in the Cu-3.0Fe-0.5Co alloy. (iii) The addition of 1.5wt % Fe and 0.1wt % Sn dramatically reduces the grain size to an average of 42 mu m, and this reduction is correlated with the appearance of smaller spherical iron-rich nanoparticles. The evolution mechanisms of the iron-rich nanoparticles and grain structure under the alloying effect are discussed.

  • 12.
    Cheng, Yajuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Jing
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Optimization of high-quality vertically aligned ZnO rod arrays by the response surface methodology2015In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 626, p. 180-188Article in journal (Refereed)
    Abstract [en]

    Optimization of the deposition parameters was conducted by the response surface methodology to synthesize high-quality ZnO rod arrays with a high texture coefficient, a large aspect ratio and a narrow bandgap. In addition, mathematical models based on statistical analysis were also developed to predict the texture coefficient, aspect ratio and bandgap of the ZnO rod arrays. With the optimized parameters, all of the three involved responses obtained the desired optimum values. The results show that the texture coefficient can be elevated up to a value of 0.998, which represents an almost perfect value. Moreover, wide range of aspect ratios was obtained for various applications and the obtained maximum value of 21.3 is relatively high value by wet chemical method, especially when no capping agent and no refreshing growth solution in a nearly neutral solution is used.

  • 13. Danwittayakul, Supamas
    et al.
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology, Thailand.
    Controlled growth of zinc oxide microrods by hydrothermal process on porous ceramic supports for catalytic application2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 586, p. 169-175Article in journal (Refereed)
    Abstract [en]

    The growth of zinc oxide (ZnO) microrods on porous ceramic substrates by mild hydrothermal process was studied. One-dimensional ZnO microrods were grown on ZnO nanoparticle seeded substrates by using equimolar concentration of zinc nitrate and hexamethylenetetramine at temperatures lower than 100 degrees C. We found that the growth of ZnO microrods on alumina and diatomite substrates were affected due to hydrolysis of substrate surfaces. Stunted ZnO microrod growth on gamma-alumina and diatomite substrates were attributed to arise due to the degradation of hexamine molecules in the growth solution. Adjusting the pH prior to the growth of ZnO microrods on both alumina and diatomite lead to the growth of ZnO microrods similar to what is observed on flat glass substrates. Cordierite does not hydrolyze easily and hence ZnO microrods with aspect ratio as high as 24, were obtained without any pH control of the growth solution. Copper nanoparticles deposited on ZnO microrods were utilized as a catalyst for methanol steam reforming and about 14% hydrogen yield was obtained with almost 90% methanol conversion at reforming temperature of 350 degrees C.

  • 14. Durmus, Z.
    et al.
    Kavas, H.
    Baykal, A.
    Sozeri, H.
    Alpsoy, L.
    Celik, S. U.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Synthesis and characterization of L-carnosine coated iron oxide nanoparticles2011In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 509, no 5, p. 2555-2561Article in journal (Refereed)
    Abstract [en]

    L-Carnosine coated iron oxide nanoparticles (CCIO NPs) have been prepared via co-precipitation of iron oxide in the presence of L-carnosine. Crystalline phase was identified as magnetite with an average crystallite size of 8 nm as estimated from X-ray line profile fitting. Particle size estimated from TEM by log-normal fitting was similar to 11 nm. FTIR analysis showed that the binding of carnosine onto the surface of iron oxide is through unidentate linkage of carboxyl group. CCIO NPs showed superparamagnetic charactersitic at room temperature. The magnetic core size of superparamagnetic CCIO NPs was found slightly smaller than the size obtained from TEM, due to the presence of magnetically dead layer. Magnetization measurements revealed that L-carnosine iron oxide composite has immeasurable coercivity and remanence with absence of hysteritic behavior, which implies superparamagnetic behavior at room temperature. The low value of saturation magnetization compared to the bulk magnetite has been explained by spin canting. LDH activity tests showed slight cytotoxicity of high dose of CCIO NPs. The ac conductivity of CCIO NPs was found to be greater than that of carnosine and the effective conduction mechanism was found as correlated barrier hopping (CBH). dc activation energy of the product at around room temperature was measured as 0.312 eV which was in good agreement with the earlier reports.

  • 15. Durmus, Zehra
    et al.
    Kavas, Hueseyin
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Baykal, Abduelhadi
    Altincekic, Tuba Guerkaynak
    Aslan, Ayse
    Bozkurt, Ayhan
    Cosgun, Sedat
    L-lysine coated iron oxide nanoparticles: Synthesis, structural and conductivity characterization2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 484, no 1-2, p. 371-376Article in journal (Refereed)
    Abstract [en]

    L-lysine coated iron oxide (LCIO) nanoparticles were synthesized by a co-precipitation method in the presence of amino acid. XRD analysis confirmed the presence of cubic magnetite phase with an average crystallite size of 8 +/- 4 nm. Particle size estimated from TEM, by log-normal fitting, is similar to 114 nm. The difference between the crystallite size from XRD and particle size from TEM indicates polycrystalline nature of synthesized particles. FT-IR show that the binding Of L-lysine on the surface of iron oxide through carboxyl groups is via unidentate linkage. The presence of L-lysine on iron oxide is also confirmed by zeta potential measurements on LCIO nanoparticles, revealing a partial coverage of iron oxide with L-lysine. In order to obtain chemically stable, well-dispersed and uniform sized nanoparticles, amino acids are suitable because they play a very important role in the body. Conductivity measurements were performed to investigate the influence of the coating on the conduction characteristics of iron oxide and results show the existence of a hopping conduction mechanism. Magnetic transition is observed at similar to 70 degrees C for uncoated iron oxide and LCIO samples. Frequency (1 Hz to 3 MHz) and temperature (290-420 K) dependant AC conductivity measurements have resulted in AC activation energies between 0.048 and 0.041 eV for uncoated and 0.050-0.044 eV for LCIO nanoparticles. Temperature-dependant DC resistivity measurements of iron oxide and LCIO at high temperatures resulted in the DC activation energies of 0.22 and 0.43 eV respectively. The higher activation energy value for LCIO is the result of coating by insulating L-lysine layer.

  • 16. Ebin, Burcak
    et al.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Gurmen, Sebahattin
    Preparation and electrochemical properties of nanocrystalline LiBxMn2-xO4 cathode particles for Li-ion batteries by ultrasonic spray pyrolysis method2015In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 620, p. 399-406Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline LiBxMn(2-x)O(4) (x = 0.1-0.4) particles are prepared by ultrasonic spray pyrolysis using lithium nitrate, manganese nitrate and boric acid at 800 degrees C in an air atmosphere. The materials properties are characterized by X-ray diffraction, scanning electron microscopy, and atomic absorption spectroscopy. The electrochemical behaviors are investigated with cyclic voltammetry and galvanostatic techniques. The particle characterization studies show that nanocrystalline particles have spinel structure of submicron size with spherical morphology. All boron substituted lithium manganese oxide spinels show improved cycling performance. Among them, LiB0.3Mn1.7O4 particles exhibit 92 mAh g(-1) discharge capacity and 82% capacity retention after 50 cycles at a 0.5 C rate. The higher degree of atomic ordering and the avoidance of the formation of a glass phase in LiBxMn2-xO4 materials are responsible for the better electrochemical performance.

  • 17. Elawad, M.
    et al.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Mola, G. T.
    Yu, Z.
    Arbab, E. A. A.
    Enhanced performance of perovskite solar cells using p-type doped PFB:F4TCNQ composite as hole transport layer2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 771, p. 25-32Article in journal (Refereed)
    Abstract [en]

    Conjugated polymers have been widely used as hole transport materials (HTM) in the preparation of mesoscopic perovskite solar cells (PSCs). In this work, we employed p-type doped conducting polymer known as poly(9,9-dioctylfluorene-co-bis-N,N-(-4-butyl phenyl)-bis-N,N-phenyl-1,4-phenylenediamine) (PFB) as a hole transport material (HTM) in perovskite based solar cell. The effect of dopant concentration on the optical and electrical properties of PEB was investigated to optimize the electrical properties of the material for the best function of the solar cell. The highest power conversion efficiency of mesoscopic perovskite solar cells (PSCs), fabricated in this investigation, was found to be 14.04% which is 57% higher than that of pristine PFB hole transport layer. The UV–Vis absorption and Raman spectroscopy measurements confirm the occurrence of oxidation in a p-type doped PFB hole transport layer. This is attributed to the transfer of electrons from the highest occupied molecular orbital (HOMO) of PEB to the lowest unoccupied molecular orbital (LUMO) of F4TCNQ. The solar cells produced using p-type doped PFB:F4TCNQ composite not only improves device performances but also shows superior long-term stability. The optical, morphological and electrical properties of the doped composite PFB: F4TCNQ and newly fabricated devices are presented and discussed in this paper.

  • 18. Eloirdi, R.
    et al.
    Gouder, T.
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Wastin, F.
    Rebizant, J.
    Dilution effect on the U-5f states: U in an Ag matrix2005In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 386, no 1-2, p. 70-74Article in journal (Refereed)
    Abstract [en]

    The electronic structure of U-diluted in an Ag matrix has been studied in situ by ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS, respectively). UxAg100-x thin films (x = 0-100 at.%) were produced by sputter co-deposition in an Ar atmosphere. UPS spectra of the Ag-4d line indicate formation of a homogeneous mixture despite the fact that U and Ag do not form stable alloys. A major goal of this work was to find out whether the dilution of U atoms in an inert matrix with no bonding states induces the localisation of the U-5f states. Both U-4f core level spectra and the U-5f spectra indicate U-5f delocalisation, down to 5 at.% of uranium in UxAg100-x films.

  • 19. Frisk, K.
    et al.
    Selleby, Malin
    KTH, Superseded Departments, Materials Science and Engineering.
    The compound energy formalism: applications2001In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 320, no 2, p. 177-188Article in journal (Refereed)
  • 20.
    Gao, Zhan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Liu, Xingmin
    Bergman, Bill
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Comparative study of Ce(0.85)Sm(0.075)Nd(0.075)O(2-delta) electrolyte synthesized by different routes2011In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 509, no 35, p. 8720-8727Article in journal (Refereed)
    Abstract [en]

    In this work, four different methods, including polyvinyl alcohol (PVA)-assisted sol-gel process, polyethylene glycol (PEG)-assisted sol-gel process, citrate sol-gel process and oxalate coprecipitation process (OCP) are employed to synthesize the Sm and Nd co-doped ceria electrolyte with the composition of Ce(0.85)Sm(0.075)Nd(0.075)O(2-delta) (SNDC). The phase structure of the powders can be well indexed with the fluorite-type CeO(2) structure. The morphology of sintered samples indicates that the ceramics can be highly densified. The relative density and the average grain size vary with the synthesis processes and the sintering temperatures. The bulk conductivities are quite close and the OCP-SNDC yields highest grain-boundary conductivities and total conductivities. The results indicate that the OCP process for the powder synthesis results in higher relative density and conductivities, lower grain-boundary resistance and activation energy. Grain-boundary space charge potentials for different specimens are calculated based on the Mott-Schottky model. The synthesis process and sintering temperature have significant effect on the space charge potential and the specific grain-boundary conductivity. (C) 2011 Elsevier B.V. All rights reserved.

  • 21. Heathman, S.
    et al.
    Haire, R. G.
    Le Bihan, T.
    Ahuja, R.
    Li, S.
    Luo, W.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    The unique high-pressure behavior of curiurn probed further using alloys2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 444, p. 138-141Article in journal (Refereed)
    Abstract [en]

    The changing role of the 5f electrons across the actinide series has been of prime interest for many years. The remarkable behavior of americium's 5f electrons under pressure was determined experimentally a few years ago and it precipitated a strong interest in the heavy element community. Theoretical treatments of americium's behavior under pressure followed and continue today. Experimental and theoretical findings regarding curium's behavior under pressure have shown that the pressure behavior of curium was not a mirror image of that for americium. Rather, one of the five crystallographic phases observed with curium (versus four for americium) was a unique monoclinic structure whose existence is due to a spin stabilization effect by curium's 5f(7) electronic configuration and its half-filled 5f-shell. We review briefly the behavior of pure curium under pressure but focus on the pressure behaviors of three curium alloys with the intent of comparing them with pure curium. An important experimental finding confirmed by theoretical computations, is that dilution of curium with its near neighbors is sufficient to prevent the formation of the unique C2/c phase that appears in pure Cm metal under pressure. As this unique C2/c phase is very sensitive to having a 5f7 configuration to maximize the magnetic spin polarization, dilution of this state with adjacent actinide neighbors reduces its stability.

  • 22. Hillert, M.
    et al.
    Selleby, Malin
    KTH, Superseded Departments, Materials Science and Engineering.
    Point defects in B2 compounds2001In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 329, no 02-jan, p. 208-213Article in journal (Refereed)
    Abstract [en]

    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.

  • 23.
    Hillert, Mats
    KTH, Superseded Departments, Materials Science and Engineering.
    The compound energy formalism2001In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 320, no 2, p. 161-176Article in journal (Refereed)
    Abstract [en]

    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.

  • 24. Hou, X. M.
    et al.
    Chou, K. C.
    Zhong, X. C.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Oxidation kinetics of aluminum nitride at different oxidizing atmosphere2008In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 465, no 1-2, p. 90-96Article in journal (Refereed)
    Abstract [en]

    In the present work, the oxidation kinetics of AlN powder was investigated by using thermogravimetric analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experiments were carried out both in isothermal as well as non-isothermal modes under two different oxidizing atmospheres. The results showed that the oxidation reaction started at around 1100 K and the rate increased significantly beyond 1273 K forming porous aluminum oxide as the reaction product. The oxidation rate was affected by temperature and oxygen partial pressure. A distinct change in the oxidation mechanism was noticed in the temperature range 1533-1543 K which is attributed to the phase transformation in oxidation product, viz. alumina. Diffusion is the controlling step during the oxidation process. Based on the experimental data, a new model for predicting the oxidation process of AlN powder had been developed, which offered an analytic form expressing the oxidation weight increment as a function of time, temperature and oxygen partial pressure. The application of this new model to this system demonstrated that this model could be used to describe the oxidation behavior of AlN powder.

  • 25.
    Johansson, Börje
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Li, Sa
    The actinides - a beautiful ending of the Periodic Table2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 444, p. 202-206Article in journal (Refereed)
    Abstract [en]

    The 5f elements, actinides, show many properties which have direct correspondence to the 4f transition metals, the lanthanides. The remarkable similarity between the solid state properties of compressed Ce and the actinide metals is pointed out in the present paper. The alpha-gamma transition in Ce is considered as a Mott transition, namely, from delocalized to localized 4f states. An analogous behavior is also found for the actinide series, where the sudden volume increase from Pu to Am can be viewed upon as a Mott transition within the 5f shell as a function of the atomic number Z. On the itinerant side of the Mott transition, the earlier actinides (Pa-Pu) show low symmetry structures at ambient conditions; while across the border, the heavier elements (Am-Cf) present the dhcp structure, an atomic arrangement typical for the trivalent lanthanide elements with localized 4f magnetic moments. The reason for an isostructural Mott transition of the f electron in Ce, as opposed to the much more complicated cases in the actinides, is identified. The strange appearance of the delta-phase (fcc) in the phase diagram of Pu is another consequence of the border line behavior of the 5f electrons. The path leading from delta-Pu to alpha-Pu is identified.

  • 26. Karaoglu, E.
    et al.
    Baykal, A.
    Deligoz, H.
    Senel, M.
    Sozeri, H.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Synthesis and characteristics of poly(3-pyrrol-1-ylpropanoic acid) (PPyAA)-Fe(3)O(4) nanocomposite2011In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 509, no 33, p. 8460-8468Article in journal (Refereed)
    Abstract [en]

    Poly(3-pyrrol-1-ylpropanoic acid) (PPyAA)-Fe(3)O(4) nanocomposite was successfully synthesized by an in situ polymerization of 1-(2-carboxyethyl) pyrrole in the presence of synthesized Fe(3)O(4) nanoparticles. Evaluation of structural, morphological, electrical and magnetic properties of the nanocomposite was performed by XRD, FT-IR, TEM, TGA, magnetization and conductivity measurements, respectively. XRD analysis reveals the inorganic phase as Fe(3)O(4) and TGA shows about 90 wt% loading of Fe(3)O(4) in the nanocomposite. FT-IR analysis indicates a successful conjugation of Fe(3)O(4) particles with polypyrrole acetic acid. Magnetization measurements show that polypyrrole acetic acid coating decreases the saturation magnetization of Fe(3)O(4) 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. The conductivity and dielectric permittivity measurements strongly depend on the thermally activated polarization mechanism and thermal transition of PPyAA in the nanocomposite structure. Large value of dielectric permittivity (epsilon') of the nanocomposite at lower frequency is attributed to the predominance of species like Fe(2+) ions and grain boundary defects (interfacial polarization).

  • 27. Kavas, Hueseyin
    et al.
    Baykal, Abduelhadi
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Koeseoglu, Yueksel
    Sertkol, Murat
    Aktas, Bekir
    Cation distribution and magnetic properties of Zn doped NiFe2O4 nanoparticles synthesized by PEG-assisted hydrothermal route2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 479, no 1-2, p. 49-55Article in journal (Refereed)
    Abstract [en]

    Nanosize ZnxNi1-xFe2O4 spinel composites with x = 0, 0.2, 0.4, 0.6, 0.8 and I were synthesized by using surfactant (polyethylene glycol (PEG)) assisted hydrothermal route and characterized by TEM, XRD and VSM techniques. The crystallite size was calculated from different characterization methods, and magnetic core size was found to be in the range of 9-20 nm from VSM. All particles showed superparamagnetic character at room temperature and M, decreased with increasing concentration of Zn2+. Due to the bigger ionic radius of Zn2+ with respect to Ni2+, the unit cell parameter 'a' increased linearly with increasing x, likewise, the oxygen positional parameter 'u' increased theoretically and experimentally as observed in the literature. Particle size was observed to decrease by substitution of Zn. The cation distribution has been calculated analytically by using X-ray diffraction data and Fe3+ cations were found to occupy mostly tetrahedral sites revealing almost an inverse-spinel structure. These results are proved to be consistent with the results of magnetic measurements. The site preference of Fe3+ cations on tetra sublattice is attributed to the synthesis conditions utilizing surfactant and low temperature.

  • 28.
    Khan, Abdullah
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Johnsson, M.
    Han, L.
    Nong, N. V.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Fabrication, spark plasma consolidation, and thermoelectric evaluation of nanostructured CoSb32014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 612, p. 293-300Article in journal (Refereed)
    Abstract [en]

    Nanostructured powders of thermoelectric (TE) CoSb3 compounds were synthesized using a chemical alloying method. This method involved co-precipitation of oxalate precursors in aqueous solution with controlled pH, followed by thermochemical treatments including calcination and reduction to produce stoichiometric nanostructured CoSb3. Moreover, CoSb3 nanoparticles were consolidated by spark plasma sintering (SPS) with a very brief processing time. Very high compaction densities (>95%) were achieved and the grain growth was almost negligible during consolidation. An iterative procedure was developed to maintain pre-consolidation particle size and to compensate Sb evaporation during reduction. Significant changes in particle size and morphology were observed, and the post-reduction cooling was found to be an important stage in the process. The spark plasma sintering (SPS) parameters were optimized to minimize the grain growth while achieving sufficient densification. Grain sizes in the range of 500 nm to 1 mu m, with compaction density of 95-98% were obtained. Preliminary measurements of thermal diffusivity and conductivity showed the dependence on grain size as well as on porosity. TE transport properties were measured in the temperature range of 300-650 K. Sample showed p-type behavior with a positive Seebeck coefficient, which increases with increasing temperature. Electrical conductivity measurements indicate metallic behavior and it decreases with increasing temperature. Thermal conductivity also decreases with increasing temperature and major contribution is due to the lattice component. A TE figure of merit of 0.15 was achieved for high purity CoSb3 nanostructured TE material at 650 K and these results are comparable with the values reported for the best unfilled/undoped CoSb3 in the literature.

  • 29.
    Kiros, Yohannes
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Majari, M.
    Nissinen, T. A.
    Effect and characterization of dopants to Raney nickel for hydrogen oxidation2003In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 360, no 02-jan, p. 279-285Article in journal (Refereed)
    Abstract [en]

    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.

  • 30.
    Kjellqvist, Lina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermodynamic assessment of the Cr-Mn-O system2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 507, no 1, p. 84-92Article in journal (Refereed)
    Abstract [en]

    The C-Cr-Fe-Ni-O and Fe-Mn-O systems have been studied earlier with the intention to thermodynamically describe the influence of oxygen on high alloyed steels. In this study the ternary Cr-Mn-O system is assessed. The liquid phase is assessed using the ionic two-sublattice model. Good agreement between calculated and experimental values is achieved.

  • 31. Kulkarni, Shrinivas R.
    et al.
    Vennila, Selva
    Phatak, Nishad A.
    Saxena, S. K
    Zha, C. S.
    El-Raghy, T
    Barsoum, W
    Luo, Wei
    Ahuja, Rajeev
    Study of Ti2SC under compression up to 47 GPa2008In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 448, no 1-2, p. L1-L4Article in journal (Refereed)
    Abstract [en]

    The pressure dependence of the lattice parameters of the ternary layered carbide, Ti2SC, was measured by using synchrotron radiation X-ray diffraction and a diamond anvil cell setup. The experiment was conducted at room temperature and no phase transformation was observed up to the maximum pressure of 47 GPa. The a and c lattice parameters at room condition are 3.216 (A) over circle and 11.22 (A) over circle, respectively. The bulk modulus, calculated using the Birch-Murnaghan equation of state, is 191 +/- 3 GPa, with a pressure derivative of 4.0 +/- 0.3 and that obtained by our ab initio calculations is 183 GPa, with a pressure derivative of 4.1. L Like the majority of the ternary layered carbides (MAX phases), compressibility along the c-axis was higher than that along the a-axis.

  • 32. Landa, Alex
    et al.
    Söderlind, Per
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Research Institute for Solid State Physics and Optics, Hungary .
    Density-functional calculations of alpha-Pu-Ga(Al) alloys2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 444, p. 296-299Article in journal (Refereed)
    Abstract [en]

    First-principles methods are employed to study the ground-state atomic volumes of alpha-Pu-Ga(Al) alloys. It is shown that a random distribution of Ga(Al) atoms in the monoclinic lattice of alpha-Pu results in a maximum expansion of this lattice and creation of the so-called alpha'-Pu phase. Any kind of ordering of Ga(Al) atoms on the monoclinic lattice results in a shrinking of the lattice constant while the ordered alpha(8)-(Pu-Ga(Al)) configuration yields the smallest lattice constant which is very close to that of pure alpha-Pu. In addition, energetics of the ordered (unrelaxed and relaxed) and disordered configurations is discussed.

  • 33.
    Li, Shuai
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Li, Zhicheng
    Bergman, Bill
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lanthanum gallate and ceria composite as electrolyte for solid oxide fuel cells2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, ISSN 0925-8388, Vol. 492, no 1-2, p. 392-395Article in journal (Refereed)
    Abstract [en]

    The composite of doped lanthanum gallate (La(0.9)Sr(0.1)Ga(0.8)Mg(0.2)O(2.85), LSGM) and doped ceria (Ce(0.8)Sm(0.2)O(1.9), CSO) was investigated as an electrolyte for solid oxide fuel cell (SOFC). The LSGM-CSO composite was examined by X-ray diffraction (XRD) and impedance spectroscopy. It was found that the sintered LSGM-CSO composite contains mainly fluorite CeO(2) phase and a minority impurity phase, Sm(3)Ga(5)O(12). The LSGM-CSO composite electrolyte shows a small grain boundary response in the impedance spectroscopy as compared to LSGM and CSO pellets. The composite electrolyte exhibits the highest conductivity in the temperature range of 250-600 degrees C, compared to LSGM and CSO. The LSGM-CSO composite can be expected to be an attractive intermediate temperature electrolyte material for solid oxide fuel cells.

  • 34.
    Li, Xiaoqing
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Third-order elastic constants and anharmonic properties of three fcc high-entropy alloys from first-principles2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 764, p. 906-912Article in journal (Refereed)
    Abstract [en]

    Third-order elastic constants (TOECs) are very important for understanding the nonlinear mechanical response of materials and evaluating the anharmonicity of crystal lattices. Here, we are concerned with investigating the six independent TOECs and related anharmonic properties of three face-centered cubic (fcc) high-entropy alloys (HEAs), namely CrFeCoNi, CrMnFeCoNi, and Cr10Mn40Fe40C10, using density-functional simulations. To benchmark computational accuracy, three ab initio codes are used to obtain the complete set of TOECs for fcc Ni. For the HEAs, we observe that the TOECs C-123 and C-456 are positive, and C-123 is particularly large. The Cauchy relations for the TOECs are partially satisfied for the three studied HEAs. With the help of the derived TOECs, the average TOECs for an isotropic polycrystal are estimated. Using the obtained TOECs, we reveal the pressure derivatives of the effective second-order elastic constants and polycrystalline moduli as well as derive the nonlinearity constant delta. The obtained pressure derivative of bulk modulus agrees very well with the available experimental data for CrMnFeCoNi. For the three considered HEAs, delta along high-symmetry directions orders as delta([011]) > delta([111]) > delta ([100]).

  • 35.
    Li, Xiaoqing
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Schönecker, Stephan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Zhao, J.
    Johansson, Börje
    Uppsala University, Sweden.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden; Wigner Research Center for Physics, Hungary.
    Alloying effect on the ideal tensile strength of ferromagnetic and paramagnetic bcc iron2016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 676, p. 565-574Article in journal (Refereed)
    Abstract [en]

    Using ab initio alloy theory formulated within the exact muffin-tin orbitals theory in combination with the coherent potential approximation, we investigate the ideal tensile strength (ITS) in the [001] direction of bcc ferro-/ferrimagnetic (FFM) and paramagnetic (PM) Fe1-xMx (M = Al, V, Cr, Mn, Co, or Ni) random alloys. The ITS of ferromagnetic (FM) Fe is calculated to be 12.6 GPa, in agreement with available data, while the PM phase turns out to posses a significantly lower value of 0.7 GPa. Alloyed to the FM matrix, we predict that V, Cr, and Co increase the ITS of Fe, while Al and Ni decrease it. Manganese yields a weak non-monotonic alloying behavior. In comparison to FM Fe, the alloying effect of Al and Co to PM Fe is reversed and the relative magnitude of the ITS can be altered more strongly for any of the solutes. All considered binaries are intrinsically brittle and fail by cleavage of the (001) planes under uniaxial tensile loading in both magnetic phases. We show that the previously established ITS model based on structural energy differences proves successful in the PM Fe-alloys but is of limited use in the case of the FFM Fe-based alloys. The different performance is attributed to the specific interplay between magnetism and volume change in response to uniaxial tension. We establish a strong correlation between the compositional effect on the ITS and the one on the shear elastic constant C' for the PM Fe-alloys and briefly discuss the relation between hardenability and the ITS.

  • 36.
    Li, Zhou
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Mao, H.
    Selleby, Malin
    A new thermodynamic description of stable Cr-carbides for the third generation of thermodynamic databasesIn: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669Article in journal (Other academic)
  • 37. Liu, Hui-ping
    et al.
    Colarieti-Tosti, M
    Broddefalk, A
    Andersson, Y
    Lidström, E
    Eriksson, O
    On the structural polymorphism of CePt2Sn2: experiment and theory2000In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 306, p. 30-39Article in journal (Refereed)
  • 38. Lou, Changsheng
    et al.
    Wang, Qiang
    Wang, Chunjiang
    Liu, Tie
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Jicheng
    Migration and rotation of TiAl3 particles in an Al-melt solidified under high magnetic field conditions2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 472, no 1-2, p. 225-229Article in journal (Refereed)
    Abstract [en]

    The effects of high magnetic fields on the migration and rotation of TiAl3 particles in an Al-7 wt.% Si alloy were studied. Without magnetic fields, the rod-like TiAl3 particles segregate at the lower part of the solidified structure. Under high uniform magnetic fields, these particles rotate to an orientation with their longitudinal axes parallel to the direction of the magnetic flux. The segregation of the particles reduces with the increase of the magnetic flux density. A negative gradient field enhances the effect of the uniform magnetic field. By altering high magnetic fields, Al-Si alloy samples containing homogeneously distributed and preferably aligned TiAl3 particles were prepared.

  • 39. Luo, Wei
    et al.
    Ahuja, Rajeev
    Ab initio prediction of high-pressure structural phase transition in BaH22007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 446, p. 405-408Article in journal (Refereed)
    Abstract [en]

    We have performed ab initio electronic structure calculations to calculate the structural properties and high-pressure phase transition in Barium dihydride (BaH2). Our results show that BaH2 crystallizes the orthorhombic phase (CoSi2-type structure) with Pnma space group at ambient conditions. A phase transition to the hexagonal (Ni2In-type structure) with P6(3)/mmc space group is found at pressure around 4 GPa. At the phase transition, the coordination number of hydrogen increases from 9 to 11 and the average bond length of Ba-H increases. The results show a band gap of 2.9 eV for orthorhombic and 1.8 eV for hexagonal phase. In addition, it was also found that more energy is required to desorb hydrogen atom from high-pressure phase as compared to ambient phase.

  • 40. Lyubimtsev, A. L.
    et al.
    Baranov, A. I.
    Fischer, Andreas
    KTH, Superseded Departments, Chemistry.
    Kloo, Lars A.
    KTH, Superseded Departments, Chemistry.
    Popovkin, B. A.
    The structure and bonding of Ni3Sn2002In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 340, no 02-jan, p. 167-172Article in journal (Refereed)
    Abstract [en]

    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.

  • 41.
    Mao, Huahai
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Sundman, Bo
    KTH, Superseded Departments, Materials Science and Engineering.
    Wang, Z. W.
    Saxena, S. K.
    Volumetric properties and phase relations of silica - thermodynamic assessment2001In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 327, no 1-2, p. 253-262Article in journal (Refereed)
    Abstract [en]

    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.

  • 42.
    Najmoddin, Najmeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Beitollahi, Ali
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Ansari, Narges
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Devlin, Eamonn
    Mohseni, Seyed Majid
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101), Material Physics, MF (Closed 20120101).
    Rezaie, Hamidreza
    Niarchos, Dimitris
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Effect of nanoconfinement on the formation, structural transition and magnetic behavior of mesoporous copper ferrite2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 598, p. 191-197Article in journal (Refereed)
    Abstract [en]

    Superparamagnetic, cubic single phase, ordered mesoporous copper ferrite is synthesized through confinement in nanocages of mesoporous silica. The heat generated during the reaction is conserved in the silica template pore channels, which allows the formation of copper ferrite at a relatively low processing temperature. The Jahn-Teller distortion is suppressed due to the effect of nanoconfinement and thus the high temperature phase of cubic copper ferrite is stabilized at room temperature. The particle size obtained from TEM, the crystallite size calculated from XRD and the magnetic domain size estimated from magnetization measurements are all in good agreement, manifesting the significant role of the confinement in the growth and fabrication of crystalline, single magnetic domain, nanoparticles with superparamagnetic behavior at room temperature.

  • 43. Oak, Jeong-Jung
    et al.
    Inoue, Akihisa
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Chun, Ho-Hwan
    Park, Yong Ho
    Surface modified Ti based metallic glasses for bioactivation by electrochemical treatment technique2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 615, p. S136-S141Article in journal (Refereed)
    Abstract [en]

    The aim of this study is surface modification of Ni-free type Ti based metallic glass (Ti42Hf11Cu11Pd36 at.%) for increasing calcification by electrochemical treatment. Ni-free type Ti based metallic glass has excellent mechanical and chemical properties which are comparable with those of Ti based alloys. Surface of Ti based metallic glasses was prepared as follows; one is anodically-oxidized porous layer by potentiostatic control in 5 M NaOH solution at 25 degrees C for 2 h, and the other is simple hydrothermal treated poros layer by immersion in 5 M NaOH solution at 60 degrees C for 24 h. The synthesized surface structures were characterized by X-ray diffraction (XRD) identification, SEM observation, energy dispersive X-ray spectroscopy (EDS) analysis and Auger electron spectroscopy (AES) analysis. These surfaces on the modified specimens have nano-mesh laminated structures and are consist of sodium titanate and titanium oxide. In addition, the above two types surfaces with nano-mesh laminated layer were immersed in Hank's balance salt solution (HBSS) at 37 degrees C for 21 days for evaluation of calcification. The apatite-forming ability on these surfaces is observed by SEM observation and EDS analysis. As stated above surface modifications are also discussed about calcification effect by different surface treatment and different formability of porosity in this study.

  • 44. Ozkaya, Tevhide
    et al.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Baykal, Abdulhadi
    Kavas, Hueseyin
    Koseoglu, Yuksel
    Aktas, Bekir
    Synthesis of Fe3O4 nanoparticles at 100 degrees C and its magnetic characterization2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 472, no 1-2, p. 18-23Article in journal (Refereed)
    Abstract [en]

    Superparamagnetic iron oxide nanoparticles were synthesized by a novel, simple and cost-effective gel-to-crystalline method by alkalizing ferrous chloride with ammonium hydroxide at 80-100 degrees C under refluxing conditions. Average crystallite size is determined as 11 nm from XRD and 11.4 nm from TEM: magnetic domain size is 9.7 nm. The saturation magnetization is 390 emu/cm(3) at 300 K, and TB is 134 K. The reduction of magnetic particle size and M-s is attributed to the presence of non-magnetic (dead) surface layer, compositional variations, superparamagnet relaxation and spin canting because of the ultrafine nature of the material. The maximization in magnetization near the blocking temperature, T-B, is attributed to a large degree of inversion of the Fe3O4 particles. Results also indicated the existence of interparticle interactions in the thermomagnetic characteristics of spinels at lower field strengths.

  • 45. Pan, Guanjun
    et al.
    Balagna, Cristina
    Martino, Luca
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Spriano, Silvia
    Microstructure and transformation temperatures in rapid solidified Ni-Ti alloys. Part II: The effect of copper addition2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 589, p. 633-642Article in journal (Refereed)
    Abstract [en]

    Ternary rapidly solidified alloys were produced and tested in this research work. Cu was added to a near equiatomic Ti49Ni51 alloy, by substituting Ni. Three compositions were considered: Ti49Ni51 Cu-x(x) (x = 5, 15, 25). Samples with the shape of cones were obtained, in order to test the effects of different rapid solidification rates. The aim of this research is to analyze the use of rapid solidification in the low regime of cooling rates (10(2)-10(3) K/s), which is much more suitable for industrial processes than the extremely high cooling rates (such as melt spinning). We found that, as Cu was added into the alloy, the transformation temperatures rapidly decline and they reach a minimum between 5 and 15 at.% of Cu. Then, they begin to increase and they are comparable with those of the binary alloy when Cu is equal to 25 at.% A higher cooling rate lowers the transformation temperatures, showing an opposite effect respect to Cu addition. Moreover, the Cu addition reduces the transformation hysteresis. Some precipitates were found in the ternary alloys and Ni and Cu showed a linear exchanging tendency in the precipitates, in the explored range of Cu content.

  • 46. Phatak, Nishad A.
    et al.
    Kulkarni, Shrinivas R.
    Drozd, Vadym
    Saxena, Surendra K.
    Deng, Liwei
    Fei, Yingwei
    Hu, Jingzhu
    Luo, Wei
    Ahuja, Rajeev
    Synthesis and compressive behavior of Cr2GeC up to 48 GPa2008In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 463, no 1-2, p. 220-225Article in journal (Refereed)
    Abstract [en]

    M(n+1)AX(n) compounds have gathered huge momentum because of its exciting properties. In this paper we report the synthesis of ternary layered ceramic Cr2GeC, a 211 M(n+1)AX(n) compound by hot-pressing. Scanning electron microscopy and X-ray diffraction have been employed to characterize the new synthesized phase. High-pressure compressibility of Cr2GeC were measured using diamond anvil cell and synchrotron C radiation at room temperature up to 48 GPa. No phase transformation was observed in the experimental pressure range. The bulk modulus of Cr2GeC calculated using the Birch-Murnaghan equation of state is 169 +/- 3 GPa, with K' = 3.05 +/- 0.15.

  • 47. Rekhi, S.
    et al.
    Dubrovinsky, L. S.
    Ahuja, R.
    Saxena, S. K.
    Johansson, Börje
    Experimental and theoretical investigations on eskolaite (Cr2O3) at high pressures2000In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 302, no 02-jan, p. 16-20Article in journal (Refereed)
  • 48.
    Saleemi, Mohsin
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Famengo, A.
    Fiameni, S.
    Boldrini, S.
    Battiston, S.
    Johnsson, M.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Thermoelectric performance of higher manganese silicide nanocomposites2015In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 619, p. 31-37Article in journal (Refereed)
    Abstract [en]

    Higher manganese silicides (HMS) are proven to be promising candidates as p-type thermoelectric material in the temperature range of 400-700 K. In this work, a series of nanostructured (NS) bulk MnSi1.73 with different levels of Ytterbium inclusions were fabricated via ball milling and the solid state reaction was completed by spark plasma sintering (SPS). Nanopowders and SPS consolidated Yb-HMS nanocomposites (NC) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to reveal the crystal structure and morphology respectively. High resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray spectroscopy (EDS) was used to investigate the material composition in bulk grains. Yb was observed to stay as nanoinclusions at the grain boundaries. TE transport properties, including Seebeck coefficient, electrical resistivity, and thermal diffusivity as well as charge carrier concentrations were evaluated. Thermal conductivity decreased with increasing Yb content, while the electrical conductivity improved for the highest Yb content. A highest figure of merit (ZT) of 0.42 at 600 degrees C was achieved for 1% Yb-HMS NC sample.

  • 49. Serikov, V. V.
    et al.
    Kleinerman, N. M.
    Vershinin, A. V.
    Mushnikov, N. V.
    Protasov, A. V.
    Stashkova, L. A.
    Gorbatov, Oleg I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Institute of Metal Physics UB RAS, Russian Federation.
    Ruban, Andrei V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
    Gornostyrev, Yu N.
    Formation of solid solutions of gallium in Fe-Cr and Fe-Co alloys: Mossbauer studies and first-principles calculations2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 614, p. 297-304Article in journal (Refereed)
    Abstract [en]

    Investigation of Ga influence on the structure of Fe-Cr and Fe-Co alloys was performed with the use of Mossbauer spectroscopy and X-ray diffraction methods. The experimental results are compared with results of first-principles calculations of the mixing and solubility energies for Ga in an Fe-X (X = Co, Cr) alloy both in ferromagnetic and paramagnetic states. It is shown that Ga mainly goes into the solid solutions of the base alloys. In the alloys of the Fe-Cr system, doping with Ga handicaps the decomposition of solid solutions, observed in the binary alloys, and increases its stability. In the alloys with Co, Ga also favors the uniformity of solid solutions. The results of the first-principles calculations testify in favor of a preferable dissolution of Ga in the FeCo regions of a multicomponent structure rather than FeCr regions, both types of regions being in the ferromagnetic state at the temperature of annealing. The analysis of Mossbauer experiments gives some grounds to conclude that if, owing to liquation, clusterization, or initial stages of phase separation, there exist regions enriched in iron, some amount of Ga atoms prefer to enter the nearest surroundings of iron atoms, thus forming binary Fe-Ga regions (or phases).

  • 50. Sertkol, M.
    et al.
    Koseoglu, Y.
    Baykal, A.
    Kavas, H.
    Bozkurt, A.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Microwave synthesis and characterization of Zn-doped nickel ferrite nanoparticles2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 486, no 1-2, p. 325-329Article in journal (Refereed)
    Abstract [en]

    Microwave assisted combustion method was used to synthesize nanocrystalline ZnxNi1-xFe2O4 from a stoichiometric mixture of corresponding metal nitrates and urea powders. The structural, chemical and magnetic properties of Ni-Zn ferrite was determined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (FTIR), vibrating sample magnetometry (VSM) and DC conductivity measurements. Results showed that the material was spinel structure with a high purity with an estimated crystallite size of similar to 20 nm by X-ray line profile fitting. TEM analysis showed necked near-spherical particles with an average size of similar to 20 nm, reflecting highly crystalline nature of these nanoparticles. Magnetic properties showed anomalities as the Zn doping level increased. This has been explained and attributed to the relative positions of Ni, Zn, and Fe ions in the crystal lattice.

12 1 - 50 of 68
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