Wavelength-dispersive X-ray Spectroscopy Analysis Research Articles

Laser-assisted reduction of iron ore using aluminum powder

This study reports on the laser-assisted reduction of iron ore waste using Al powder as a reducing agent. Due to climate change and the global warming situation, it has become of paramount importance to search for and/or develop green and sustainable processes for iron and steel production. In this regard, a new method for iron ore utilization is proposed in this work, investigating the possibility of iron ore waste reduction via metallothermic reaction with Al powder. Laser processing of iron ore fines was performed, focusing on the Fe2O3–Al interaction behavior and extent of the iron ore reduction. The reaction between the materials proceeded in a rather intense uncontrolled manner, which led to the formation of Fe-rich domains and alumina as two separate phases. In addition, a combination of Al2O3 and Fe2O3 melts, as well as transitional areas such as intermetallics, was observed, suggesting the occurrence of incomplete reduction reaction in isolated regions. The reduced iron droplets were prone to acquire a sphere-like shape and concentrated mainly near the surface of the Al2O3 melt or at the interface with the iron oxide. Scanning electron microscopy, energy-dispersive x-ray spectroscopy, and wavelength-dispersive x-ray spectroscopy analyses were employed to analyze the chemical composition, microstructure, and morphological appearances of the reaction products. High-speed imaging was used to study the process phenomena and observe differences in the movement behavior of the particles. Furthermore, the measurements acquired from x-ray computed microtomography revealed that approximately 2.4% of iron was reduced during the laser processing of Fe2O3–Al powder bed, most likely due to an insufficient reaction time or inappropriate equivalence ratio of the two components.

Synthesis, crystal structure and physical properties of the clathrate-I phase Ba8RhxSi46−x−y□y

The new clathrate-I phase Ba(8)Rh(x)Si(46-x-y□y) (2.36 < x < 2.74; y = 0.65 for x = 2.74), Pearson symbol cP54, space group Pm3[combining macron]n, was prepared as a single phase and characterized. For these compositions, the lattice parameter does not change significantly and was found to be a = 10.347(1) Å. Phase relations were investigated by means of metallographic and thermal analyses. The incongruently melting phase Ba(8)Rh(x)Si(46-x-y□y) was obtained by annealing a solidified melt of the stoichiometric composition at 1000 °C for five days. Below 850 °C, the clathrate phase slowly decomposes to BaSi(2), Si and the new compound BaRh(2)Si(9). Crystal structure and vacancy concentration were investigated by means of single crystal and powder X-ray diffraction and wavelength dispersive X-ray spectroscopy analyses. Quantum chemical calculations show that the Rh 4d states hybridize with Si 3p states so that the DOS structure cannot be simply deduced in a rigid band approach from that of the binary Ba(8)Si(46). Analysis of the chemical bonding applying the ELI-D approach yielded covalent two-center two-electron bonds between Rh and Si atoms. For the composition Ba(8)Rh(2.74)Si(42.61□0.65), a temperature dependent diamagnetic susceptibility and an almost temperature independent electrical resistivity (ρ≈ 5 μΩm) were observed. The magnitude of the negative Seebeck coefficient is increasing linearly with temperature from 0 μV K(-1) at 2 K to -35 μV K(-1) at 850 K indicating n-type electrical conductivity.

Formation Mechanisms of Islands on Cu-Alloyed GaN Grown by Plasma Assisted Molecular Beam Epitaxy

Cu-alloyed GaN epilayers were prepared by plasma assisted molecular beam epitaxy in a Ga-rich environment with Cu-to-Ga beam equivalent pressure ratios of 1.2 to 4.8%. Islands enriched with Cu are found on all the GaN epitaxial layers. The islands are composed of a Cu9Ga4 intermetallic phase and GaN with the orientation relationship: [111]Cu9Ga4//[1 10]GaN and (10 )Cu9Ga4//(0001)GaN. The formation mechanisms of the islands are discussed in detail. Wavelength dispersive X-ray spectroscopy analyses indicate that the 1.2 and 4.8% samples contain 0.10 ± 0.02 atom % Cu and 0.04 ± 0.03 atom % Cu, respectively. Both samples show ferromagnetic behavior with a magnetization of in a range of (2.3–5.1) × 103 A/m at saturation. A strategy to suppress the island formation and increase Cu incorporation is accordingly proposed and verified.

Dielectric function and optical properties of quaternary AlInGaN alloys

The optical properties of quaternary AlxInyGa1-x-yN alloy films with 0.16&amp;lt;x&amp;lt;0.64 and 0.02&amp;lt;y&amp;lt;0.13 are presented. The (0001)-oriented AlInGaN layers were grown by metal-organic vapor phase epitaxy on thick GaN/sapphire templates. High-resolution x-ray diffraction measurements revealed the pseudomorphic growth of the AlInGaN films on the GaN buffer. Rutherford backscattering and wavelength-dispersive x-ray spectroscopy analysis were used in order to determine the composition of the alloys. The ordinary dielectric function (DF) of the AlInGaN samples was determined in the range of 1–10 eV by spectroscopic ellipsometry (SE) at room temperature (synchrotron radiation: BESSY II). The sharp onset of the imaginary part of the DF defines the direct absorption edge of the alloys. At higher photon energies, pronounced peaks are observed in the DF indicating a promising optical quality of the material. These features are correlated to the critical points of the band structure (van Hove singularities). An analytical model, which permits us to accurately describe the dielectric function (or optical constants) in the range of 1–10 eV, is also presented. The band-gap and high-energy interband transition values are obtained by fitting the experimental DF with the analytical model. The strain influence on the bandgap is evaluated by using the k×p formalism. Furthermore, an empirical expression is proposed which allows us to calculate the AlInGaN band-gap and high-energy inter-band transitions in the whole compositional range (x, y). The band-gap values obtained from the empirical expression are in good agreement with both the calculated ab initio and the experimental values determined by SE.

Complete Titanium Substitution by Boron in a Tetragonal Prism: Exploring the Complex Boride Series Ti3−xRu5−yIryB2+x (0 ≤ x ≤ 1 and 1 &lt; y &lt; 3) by Experiment and Theory

Polycrystalline samples and single crystals of four members of the new complex boride series Ti(3-x)Ru(5-y)Ir(y)B(2+x) (0 ≤ x ≤ 1 and 1 < y < 3) were synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere. The new silvery phases were structurally characterized by powder and single-crystal X-ray diffraction as well as energy- and wavelength-dispersive X-ray spectroscopy analyses. They crystallize with the tetragonal Ti(3)Co(5)B(2) structure type in space group P4/mbm (No. 127). Tetragonal prisms of Ru/Ir atoms are filled with titanium in the boron-poorest phase (Ti(3)Ru(2.9)Ir(2.1)B(2)). Gradual substitution of titanium by boron then results in the successive filling of this site by a Ti/B mixture en route to the complete boron occupation, leading to the boron-richest phase (Ti(2)Ru(2.8)Ir(2.2)B(3)). Furthermore, both ruthenium and iridium share two sites in these structures, but a clear Ru/Ir site preference is found. First-principles density functional theory calculations (Vienna ab initio simulation package) on appropriate structural models (using a supercell approach) have provided more evidence on the stability of the boron-richest and -poorest phases, and the calculated lattice parameters corroborate very well with the experimentally found ones. Linear muffin-tin orbital atomic sphere approximation calculations further supported these findings through crystal orbital Hamilton population bonding analyses, which also show that the Ru/Ir-B and Ru/Ir-Ti heteroatomic interactions are mainly responsible for the structural stability of these compounds. Furthermore, some stable and unstable phases of this complex series could be predicted using the rigid-band model. According to the density of states analyses, all phases should be metallic conductors, as was expected from these metal-rich borides.

Behavior of U-Zr Alloy Containing Simulated Fission Products during Anodic Dissolution in Molten Chloride Electrolyte

To investigate the distribution of fission product elements in the electrorefining of spent metallic fuel, electrorefining tests were carried out using U-Zr alloy containing simulated fission products. An intermediate region was found between undissolved alloy and Zr-rich regions formed by the anodic dissolution of uranium. The composition of this region determined by wavelength-dispersive X-ray spectroscopy (WDS) analysis corresponded to that of δ-phase (63–78 at% Zr) in the U-Zr binary phase diagram. This region is expected to form in the course of the anodic dissolution sequence that begins from an undissolved U-Zr alloy and ends with a Zr-rich region. From the results of chemical and WDS analyses of anode residue samples, it was predicted that noble metals would stay in the anode residue as long as zirconium remains even after most of the uranium in the alloy was dissolved. Analytical results indicated no large difference betweenthe noble metal behavior in simulated material and in irradiated EBR-II driver fuels. Decontamination factors of uraniumfrom molybdenum and palladium were defined as ratios between their concentrations in the initial alloy loaded into an anode and those in cathode products, and evaluated from the analytical results. Although there was some scattering of data, decontamination factors of around 70 for molybdenum and 10 for palladium would be expected.

Behavior of U-Zr Alloy Containing Simulated Fission Products during Anodic Dissolution in Molten Chloride Electrolyte

To investigate the distribution of fission product elements in the electrorefining of spent metallic fuel, electrorefining tests were carried out using U-Zr alloy containing simulated fission products. An intermediate region was found between undissolved alloy and Zr-rich regions formed by the anodic dissolution of uranium. The composition of this region determined by wavelength-dispersive X-ray spectroscopy (WDS) analysis corresponded to that of δ-phase (63–78 at% Zr) in the U-Zr binary phase diagram. This region is expected to form in the course of the anodic dissolution sequence that begins from an undissolved U-Zr alloy and ends with a Zr-rich region. From the results of chemical and WDS analyses of anode residue samples, it was predicted that noble metals would stay in the anode residue as long as zirconium remains even after most of the uranium in the alloy was dissolved. Analytical results indicated no large difference betweenthe noble metal behavior in simulated material and in irradiated EBR-II driver fuels. Decontamination factors of uraniumfrom molybdenum and palladium were defined as ratios between their concentrations in the initial alloy loaded into an anode and those in cathode products, and evaluated from the analytical results. Although there was some scattering of data, decontamination factors of around 70 for molybdenum and 10 for palladium would be expected.

An AFM and XPS study of corrosion caused by micro-liquid of dilute sulfuric acid on stainless steel

Micro-liquid of dilute sulfuric acid deposited on SUS304 steel surface were observed with the ac non-contact mode of an atomic force microscopy (AFM), and the detail of the corrosion process caused by them was investigated with the contact mode of the AFM, X-ray photoelectron spectroscopy (XPS) and wavelength dispersive X-ray spectroscopy (WDXS). As a result, even not applying bias voltages between the tip of the cantilever and the specimen, micro-liquid of sulfuric acid can be successfully imaged using the ac non-contact mode of AFM. Two shapes of micro-acid, i.e., micro-droplets and micro-films, were found to co-exist on the specimen surface. On areas covered by micro-films of acid, only small corrosion product particles appeared and no corrosion pits were found. Beneath micro-droplets, corrosion reaction continue to produce pits until they were all consumed to form a corrosion product (mainly iron oxides) with almost the same shape with the droplet. The total corrosion reaction time was speculated to be between 690 and 1500ks. The corrosion product formed from micro-droplets was believed to be a process of accumulating small corrosion product particles from the liquid/substrate interface to the surface of the formerly produced corrosion product. The XPS and WDXS analysis also supports the above results.

Interdiffusion and Phase Behavior in Polysynthetically Twinned (PST) TiAl / Ti Diffusion Couples

ABSTRACTDiffusion couples of pure Ti and polysynthetically twinned (PST) TiAl (49.3 at.% Al) were prepared by high vacuum hot-pressing, with the bonding interface perpendicular to the lamellar planes. Diffusion experiments were carried out by annealing the couples in the same furnace at 650, 700 and 850°C for various times. The cross-section of the couple was studied using scanning electron microscopy (SEM) and quantitative wavelength-dispersive x-ray spectroscopy (WDS). A reaction layer whose composition is close to that of the stoichiometric α2-Ti3Al phase formed along the PST TiAl / Ti bonding interface in PST TiAl side. Direct measurements of the thickness of the reaction zone were performed at different phase regions and various boundaries. By assuming the thickness of the reaction zone increases as (Dt)1/2, where D is the diffusion coefficient and t is the annealing time, the diffusion coefficients at these temperatures were calculated. Composition profiles in the reaction zone, along the lamellae and at the lamellar interfaces were obtained by WDS analyses.