Results 1 - 10 of 1776
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[en] Electronic spectral studies of lanthanides (Ln) in mixed metal environments of the type [Ln(III).DTPA.M(II)] (where Ln(III)=Pr, Nd, Sm, Dy, Er, Tm; and M(II)=Mn, Fe, Co, Ni, Cu and Zn) in aqueous phase at controlled pH (∝4.00) have been carried out in order to evaluate electronic spectral parameters, viz: (i) oscillator strength (fJO), (ii) Judd-Ofelt parameters (Tλ), (iii) interelectronic repulsion (Racah) parameters (δEk) and (iv) nephelauxetic ratio (δE3/δE1) values in mixed metal environments and to examine their variations as a result of insertion of M(II) (3d transition metal) ions in a [Ln.DTPA] environment. Octadentate DTPA has been used as a bridging ligand between two elemental moieties, viz: Ln(III) and M(II). The electronic spectral parameters (fJO), (Tλ) and (δE3/δE1) values show marked dependence on the nature of M(II) ions inserted in [Ln.DTPA] complex with a general sequence of Mn< Fe< Co< Ni< Cu>Zn indicating an allowed dependence of the spectral parameters on the nature of the M(II) ion. The variations in the spectral parameters have been discussed in light of partial covalency, symmetry around the Ln(III) cation and the degree of delocalisation of the 4f shell. J quantum number dependency of the electronic spectral parameters has also been discussed. (orig.)
[en] Raman Ln-Cl stretching spectra (Ln=rare earth ion) were measured for alcoholic solutions (alcohol=methanol, ethanol and n-propanol) of anhydrous rare earth chlorides. From the extended s-shaped variation of the frequency for the Ln-Cl stretching Raman band across the series, it is concluded that the inner-coordination number of rare earth ions decreases by one in the latter region of the rare earth series. (orig.)
[en] We report EXAFS (extended X-ray absorption fine structure) measurements on three solid solutions of rare-earth monotelluride in order to measure the x-dependence of the cation-anion distance and Debye-Waller factor. We find Yb1-xEuxTe is an ideal solid solution with a bimodal distribution of distances, accommodated by the Te sublattice, at contrast with the two other solid solutions Pb1-xEuxTe and Yb1-xGdxTe. The anomalous behaviour of the EXAFS parameters in the last system is related to the shallow nature of the Gd donor. (orig.)
[en] Highlights: ► Phase diagram of Fe–B–V system was modelled by CALPHAD method. ► Database for thermodynamic calculations for Fe–B–V system was created. ► The new ternary phase was found in 67Fe–18B–15V [in at.%] alloy. - Abstract: The phase equilibria of the Fe–B–V ternary system are studied experimentally and theoretically in this paper. Phase diagram of the system was modelled by CALPHAD method. Boron was modelled as an interstitial element in the FCC and BCC solid solutions. The calculations of isothermal sections of phase diagram are compared with our experimental results at 903 and 1353 K and with available literature experimental data. New ternary phase (with chemical composition 28Fe32V40B in at.%) was found in 67Fe–18B–15V alloy [in at.%]. Further experimental studies for the determination of exact nature of the ternary phase including crystallographic information are necessary.
[en] The role of the donor impurity band in the conduction of highly doped and compensated intermetallic semiconductors with MgAgAs type of structure was investigated. A simulation of the electronic structure for TiCo1-xNi xSb semiconducting solid solution was carried out. A scheme of the impurity band transformation in TiCoSb semiconductor due to donor impurities doping was advanced. A conduction transition from activated to metallic type when the TiCo1-xNi xSb solid solution composition changes was observed. This conduction transition is associated with the Anderson-type transition
[en] Highlights: ► The binary and ternary interdiffusion coefficients in Ti-rich β Ti–Al–Fe alloys have been determined at 1423 K using the extended Matano method. ► The main and cross interdiffusion coefficients are positive in the ternary alloys. ► The repulsive interactions exist between Al and Fe atoms in the ternary alloys. ► Al occur by vacancy diffusion mechanisms and Fe diffusion takes place by some kind of interstitial diffusion mechanism in β Ti–Al–Fe alloys. - Abstract: The binary interdiffusion coefficients D∼(Ti–Fe) in β Ti–Fe alloy and D∼(Ti–Al) in β Ti–Al alloy, Fe impurity diffusion coefficients DFe(Ti–Al)∗ in β Ti–Al alloys, and ternary interdiffusion coefficients D∼AlAlTi, D∼FeFeTi, D∼AlFeTi and D∼FeAlTi in Ti-rich β Ti–Al–Fe alloys were determined at 1423 K using binary and ternary diffusion couples by ordinary and extended Matano methods and Hall’s one. The D∼(Ti–Al) values increase with Al concentration, and the D∼(Ti–Fe) values show almost no concentration dependence. The DFe(Ti–Al)∗ values in β Ti–Al alloys steeply decrease with Al concentration up to 7 at.%Al and become almost constant over about 7 at.%Al. In the ternary β Ti–Al–Fe alloys, the D∼AlAlTi, D∼FeFeTi, D∼AlFeTi and D∼FeAlTi values are positive, and the D∼FeFeTi and D∼FeAlTi values are larger than the D∼AlAlTi and D∼AlFeTi ones, respectively. They show the complicated dependence on concentrations of Al and Fe elements. The positive ratios of D∼FeAlTi/D∼FeFeTi and D∼AlFeTi/D∼AlAlTi indicate that the repulsive interactions exist between Al and Fe atoms in the ternary alloys, but the negative ratios of converted interdiffusion coefficients D∼FeTiAl/D∼FeFeAl show the attractive interactions between Ti and Al and between Ti and Fe atoms in this alloy. These diffusion coefficients and data suggest that Al diffusion occur by vacancy diffusion mechanisms and Fe diffusion takes place by some kind of interstitial diffusion mechanism in β Ti–Al–Fe alloys.
[en] Graphical abstract: Well-crystallized PtAu alloy clusters and carbon supported PtAu alloy clusters were successfully fabricated via a one-step route by a solution plasma sputtering technique at atmospheric pressure, and show good electrocatalytic activity. Highlights: ► Crystalline PtAu alloy clusters were synthesized by a plasma sputtering technique. ► The technique was an operation in an open system under atmospheric pressure. ► PtAu alloy nanoclusters (1.5 ± 1.0 nm) show good electrocatalytic activity. ► Carbon supported PtAu alloy clusters were fabricated via a one-step route, too. ► The process will have potential application in synthesis of other nanomaterials. -- Abstract: Well-crystallized PtAu alloy clusters of about 2.0 nm in mean diameter are successfully fabricated via a one-step route of solution plasma sputtering at atmospheric pressure. The solution plasma provides a novel reaction field with highly energetic state for the formation of PtAu alloy clusters. The synergetic effects of rapid energetic radicals’ bombardment, atom vapor diffusion, plasma expansion and solution medium condensation resulted in the formation of PtAu alloy clusters with various relative atom amount ratios. PtAu alloy clusters are highly dispersive in water for a long time without any polymeric stabilizer. As-fabricated PtAu alloy clusters show well electrocatalytic activity. PtAu alloy clusters are easily collected and well re-dispersed in various organic solvents for various potential applications. And PtAu alloy clusters supported on carbon were successfully fabricated by a one-step route. These results imply that this novel process will have potential application in future in the design and mass production of various multifunctional metal and/or alloy clusters
[en] The phase structures and electrochemical performance of V2.1TiNi0.5Hf0.05Cox (x=0, 0.113, 0.152 and 0.192) alloys have been investigated. It is found that the addition of Co into the V2.1TiNi0.5Hf0.05 alloy decreases the amount of the V-based solid solution main phase and increases the amount of C14-type secondary phase without any change in the pattern of the three-dimensional network structure. With increasing Co content, the unit cell of the main phase contracts and that of the secondary phase expands. Electrochemical measurements show that the maximum discharge capacity of the Co-added alloys is much less than that of V2.1TiNi0.5Hf0.05 alloy, but their high-rate dischargeability and cycle stability are markedly improved
[en] Research highlights: → Thermodynamic optimization of the Au-Sb binary system was updated. → The Si-Sb binary system was assessed from critical review of experimental information. → Thermodynamic modeling of the Au-Sb-Si ternary system was performed. → The phase relations of this ternary system are useful to design Au-based solders. - Abstract: Thermodynamic optimization of the Au-Sb binary system was updated as well as the Si-Sb binary system was assessed thermodynamically using the CALPHAD method based on the critical review of the available experimental information from the published literature. The solution phases including liquid, fccA1(Au), diamondA4(Si) and rhombohedralA7(Sb), are modeled as substitutional solutions and their excess Gibbs energies are expressed by a Redlich-Kister polynomial. The solubility of Si in the intermetallic compound AuSb2 is not taken into account because of the lack of experimental information. Combined with previous assessment of the Au-Si binary system, thermodynamic modeling of the Au-Sb-Si ternary system was performed to reproduce well the measured phase equilibria. The liquidus projection and several vertical sections of this ternary system were calculated, which are in reasonable agreement with the reported experimental data.
[en] Encouraged by the promising application of the Al-Cu-Sc system in the development of high strength aluminum alloy, the Al-rich region of this system was assessed by the CALPHAD approach. In order to make the models used for the phases in the three binary sub-systems compatible with each other, Al-Sc and Cu-Sc system were remodeled. Substitutional solution model was used for solution phases and sublattice model for binary intermetallic phases and the ternary compound Al8-xCu4+xSc. Comparisons between the calculated and experimental results showed that most of the experimental information was satisfactorily described by the present thermodynamic description.