The dissolution and speciation mechanism of the chromium aqua and chloro complex in hydrochloric acid solutions.

The distribution of Ce in orthophosphate Sr-3(PO4)(2) was investigated by the combined single-crystal X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) analyses. Sr-3(PO4)(2):Ce3+ compounds with two different Sr sites (3a and 6c sites) were synthesized using the solid-state reaction method. Single-crystal XRD analysis confirmed the location of Ce at the 3a site along with the corresponding vacancy or coexisting Li at the 6c site. Additionally, the Ce K-edge EXAFS analysis supported the occupancy of Ce3+ at the 3a site rather than at the 6c site.

<title>Abstract</title>Distribution of Ge atoms between tetrahedral and octahedral sites in the spinel-type structure of Fe_2.64Ge_0.36O₄ thin films fabricated by radio frequency sputtering with a composite target of magnetite and Ge has been investigated by extended X-ray absorption fine structure analysis. The local structural changes around the Ge atoms in the films induced by annealing at 573 and 873 K are discussed through comparison of the local structure for sintered crystalline Fe_2.7Ge_0.3O₄ in which Ge atoms preferentially located at the tetrahedral site of the spinel-type structure. This work provides successful information on the structural change with magnetic property of the thin films as follows: the Ge atoms statistically distributed at the tetrahedral and octahedral sites of the as-synthesized films and preferentially occupied the tetrahedral site by annealing at 873 K corresponding to the increase in magnetization.

Fe–Ga alloys are functional magnetostrictive materials, which are promising for application in actuators and sensors. Because surface properties of these alloys such as corrosion resistance are important in technological applications, it is required to characterize the chemical composition and state of the surface of these alloys, which depend on annealing conditions. In this study, X-ray absorption spectroscopy (XAS) and secondary ion mass spectrometry (SIMS) were used to characterize surface layers formed on the Fe–Ga alloys annealed under different atmospheric conditions. The XAS spectra of the annealed sample showed that the amount of gallium in the surface layers increased due to annealing, whereas the XAS spectra of the as-polished alloys revealed that the amounts of iron and gallium arise from the bulk composition. The XAS spectra of the alloys annealed in argon–hydrogen with residual oxygen showed that gallium is increased for its preferential oxidation. SIMS depth profile also showed the enrichment of gallium on the surface and the inhomogeneous distribution of iron on the surface layers.

This study tested the removal of arsenic from copper ore concentrate via a mechanochemical treatment by planetary ball milling. The harmful components of ore, such as arsenic, are increasing year by year and decreasing the copper grade, therefore there is a strong need to improve the separation of arsenic from copper ore. The effect of grinding as a result of chemical activation caused by mechanochemical treatment was evaluated by XRD and X-ray absorption spectroscopy (XAS) measurements. From the results of the XRD analysis, several crystalline minerals were identified from the original samples. The diffraction peaks of the original samples were reduced by grinding, although grinding did not generate any new diffraction peaks. The comparison of the results of grinding in dry and wet conditions showed that the rate of disappearance of the crystalline minerals was faster in dry grinding than in wet grinding. To clarify the chemical state of arsenic in copper ore, XAS analysis was carried out. The results indicated that the arsenic compound changed from sulfide, in the original sample, to oxide after grinding. As a result of oxidation, the arsenic was easy to dissolve in a water and alkaline solution, and optimized dry and wet grinding conditions achieved up to 76% arsenic removal efficiency.

Acquiring the quantitative state-of-charge (SOC) distribution of a lithium-ion battery cathode is important to improve the performance of lithium-ion batteries for the application to large-scale devices. The conventional method to obtain SOC distribution, i.e., X-ray absorption spectroscopy (XAS), requires a synchrotron radiation facility, references that are difficult to prepare, and an investigation of the XAS spectra of the references. Herein, we demonstrate that laser-induced breakdown spectroscopy (LIBS) can acquire a quantitative SOC of a charged lithium-ion battery cathode with high accuracy by comparing the SOC values of charged cathodes containing Li2NaV2(PO4)(3) as an active material determined by LIBS, XAS, and a charge-discharge curve. We perform LIBS measurements in a reduced argon atmosphere of 1000 Pa and use a calibration curve obtained by measuring the emission intensities at 610.4 nm of the pristine cathode. The SOCs of the charged cathodes agree well with the average SOCs estimated from the charge-discharge curves, whereas those determined by XAS do not. Therefore, LIBS is more suitable to acquire a quantitative SOC distribution of a lithium-ion battery cathode than XAS because LIBS is a laboratory-scale measurement and requires a single simple reference in addition to its high accuracy. (c) 2019 The Electrochemical Society.

Microscopic residual stress evolution in an austenite (γ) grain during a shape-memory process in an Fe-Mn-Si-Cr alloy was investigated using the white X-ray microbeam diffraction technique. The stresses were measured on a coarse grain, which had an orientation near &lt 144&gt , parallel to the tensile loading direction with a high Schmid factor for a martensitic transformation. The magnitude of the residual stresses in a grain of the sample, which was subjected to a 23 % tensile strain and subsequent shape-recovery heating, was found to be very small and comparable to that prior to tensile deformation. Measurements of the recovery strain and microstructural analyses using electron backscatter diffraction suggested that the low residual stresses could be attributed to the significant shape recovery caused by a highly reversible martensitic transformation in the grain with a particular orientation.

<p>Development of a novel alcohol reduction technique for the one-pot synthesis of Cu–Ni NWs by elucidating the formation mechanism by using <italic>in situ</italic> spectroscopic measurements.</p>

In this study, in situ white X-ray microbeam diffraction experiments were conducted to investigate the microscopic deformation behavior of a Cu-Al-Mn superelastic alloy during tensile testing. Local deformation both at a grain scale and an intragranular scale was revealed by analyzing Laue spot streaking that occurred within a grain and in some grains with different orientations. The streaking measured within a grain under tensile load showed inhomogeneous behavior because of an inhomogeneous martensitic transformation. Moreover, the effect was dependent on grain orientation. In a grain with a high Schmid factor, a large dispersion in the 20 diffraction angle of Laue spots was observed due to significant Laue spot streaking, which can be attributed to that grain's favored martensitic transformation.

The magnetic iron oxide particles are very attractive for biomedical applications because of good biological compatibility.

Fe-Ga alloys show large magnetostriction, which strongly depends on crystal orientation. This phenomenon is considered to be associated to some degree with large elastic anisotropy in single crystals. In this study, white X-ray diffraction with micro-beam synchrotron radiation was used to evaluate the microscopic stresses evolved in a polycrystalline Fe-Ga alloy under tensile loading. In the analysis, the large elastic anisotropy of the Fe-Ga alloy was focused. The stress distribution in the alloy microstructure under tensile loading was estimated using a finite element method (FEM) simulation that considered the dependence of the elasticity on the crystal orientation. The crystal orientation of grains in the polycrystalline Fe-Ga alloy was measured using electron backscatter diffraction. The FEM simulation showed that the stress distribution in the microstructure depended on the crystal orientation. The X-ray diffraction stress analysis indicated that under tensile loading, the stresses in the alloy depended on the crystal orientation. This finding is similar to the results obtained from the FEM simulation, although the absolute values of the stresses may have reflected the effects of heterogeneous deformation on the stress distribution.

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Fe-Ni hydroxide fine particles with a layered double hydroxide-type structure were precipitated as an intermediate in polyol (ethyleneglycol) solution with Fe compositions ranging between about 10 and 90 at%. Subsequent reduction-annealing of the above polyol-derived particles with 13-56 at% Fe at 673 K resulted in the synthesis of fcc Fe-Ni alloy fine particles with their sizes less than about 50 nm. The lattice constants of fcc Fe-Ni alloy particles were close to those of the bulk fcc Fe-Ni alloy with similar compositions. X-ray absorption spectroscopy measurements suggested that fcc Fe-Ni alloy was formed through simultaneous reduction of Fe and Ni in Fe-Ni hydroxide. Consequently, the reduction-annealing of polyol-derived Fe-Ni hydroxide fine particles is proved to be an effective process for obtaining composition-controlled Fe-Ni alloy fine particles.

Single-phase Co carbide particles with the Co3C structure were obtained by the polyol process using tetraethylene glycol (TEG) solution containing polyvinylpyrrolidone (PVP). Additionally, particles with a mixture of face-centered cubic Co and hexagonal close-packed Co were precipitated in the TEG solution without PVP. The particles synthesized with PVP exhibited coercivity of about 5.7 kOe, which was larger than that of the particles synthesized without PVP. Thus, the addition of PVP to the TEG solution induces the formation of Co3C-structured Co carbide particles with large coercivity. Particles precipitated from the TEG solution with an initial molar ratio of Co: Ni = 8:2 were also identified as the single phase of the Co3C structure by X-ray diffraction measurement. In addition, it was confirmed by measurements of the extended X-ray absorption fine structure spectra that Ni atoms in the precipitated particles had a local structure similar to that of Co atoms in the single-phase particles with the Co3C structure. Thus, Ni-substituted Co carbide particles with the Co3C structure can be obtained by the polyol process using PVP.

White X-ray microbeam diffraction was applied to investigate the microscopic deformation behavior of individual grains in a Cu-Al-Mn superelastic alloy. Strain/stresses were measured in situ at different positions in several grains having different orientations during a tensile test. The results indicated inhomogeneous stress distribution, both at the granular and intragranular scale. Strain/stress evolution showed reversible phenomena during the superelastic behavior of the tensile sample, probably because of the reversible martensitic transformation. However, strain recovery of the sample was incomplete due to the residual martensite, which results in the formation of local compressive residual stresses at grain boundary regions.

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Various dopants were added to BaZrO3 and the conductivities, the proton concentrations, the site occupancy of the dopants and the change in lattice volume as a result of chemical expansion were investigated. Lanthanide group dopants occupied both the Ba and Zr sites, but the amount of these dopants in the Ba site was too limited to significantly influence the conductivity. The samples doped with Yb, Tm, Er, Y and Ho showed both high proton concentrations and high conductivities, together with a relatively large lattice expansion as a result of hydration. We therefore suggest that, in most instances, the proton concentration, proton conductivity and lattice change as a result of chemical expansion were all correlated in proton conductive acceptor-doped BaZrO3. However, Sc-doped BaZrO3 seemed to be different. Its proton concentration was high, but the conductivity and lattice change as a result of chemical expansion were relatively small. This indicates that the conductivity was strongly related to the lattice expansion resulting from hydration rather than simply the proton concentration.

X-ray diffraction (XRD) and electron microprobe microanalysis (EPMA) were used for characterizing the structure and composition of surface layers formed on austenitic Fe-Mn-Si shape memory alloys under vacuum. The XRD results demonstrated that during annealing, face centered cubic austenite is transformed to hexagonal close packed martensite on the alloy surface. The EMPA results revealed that manganese in the surface layer was depleted during annealing. Further, this analysis determined that the thickness of the surface layer of the alloy annealed at 1173 K for 1 h was approximately 20 μm and that value is consistent with the depth detected by XRD. The compositional changes of the surface layers such as manganese depletion by annealing were discussed based on the ternary Fe-Mn-Si phase diagram. Although the formation of body centered cubic ferrite is detrimental to shape memory alloys, the amount of manganese was also observed to change during processing and strongly influence the stability of the shape memory alloys.

<p>The monoanionic state of ethylene glycol was theoretically and experimentally confirmed to be the active species during reduction reaction of metal salts.</p>

New hybrid compounds LnCoCl(deg)(2) (deg = diethyleneglycolate; Ln = Nd, Sm, Eu, Gd and Ho) have been synthesized by mixing cobalt and rare earth cations in a boiling diethyleneglycol (degH(2)) medium. Their crystallographic structures have been ab initio solved from synchrotron powder diffraction data. They consist of edge sharing tetrameric sub-units [(Ln(2)CO(2))(deg)(4)(Cl)(2)] forming 1D infinite chains along the c parameter of a monoclinic unit cell (SG = C2/c). The five-and seven-coordination of Co2+ and Ln(3+) cations inferred from the crystallographic results is confirmed by UV-visible absorption and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. In the LnCoCl(deg)(2) (Ln = Nd, Sm, Eu, Gd, Ho) series, weak antiferromagnetic superexchange interactions have been evidenced, between high spin Co2+ and Ln(3+) orbitally degenerate cations. These materials are considered as potential precursors for the simultaneous reduction of Co-Ln-glycolate species into bimetallic nanoparticles by the polyol process.

Electron backscatter diffraction was used to observe the microstructure of an austenitic high-manganese twinning-induced plasticity steel and investigate the crystal orientation of grains in this steel. The results showed that mechanical twins are formed in a grain with a high Schmid factor during the tensile test. The orientation data obtained were used to estimate the anisotropic elasticity of the grains in the steel. The microscopic stress and strain evolved in the microstructure of the steel unloaded after plastic deformation were estimated using finite element method simulation in which the elastic anisotropy of the steel was taken into account. The simulation indicated that the evolution of microscopic stress and strain in the microstructure is considerably influenced by the crystal orientation of the grains. Furthermore, white X-ray diffraction with microbeam synchrotron radiation was used to characterize the evolution of microscopic stress and strain in the grains of the steel. The stress analysis during white X-ray diffraction indicated the formation of residual microscopic stress after tensile deformation, which was found to be distributed heterogeneously in the steel. It was also shown that the direction of the maximum principal stresses at different points in the microstructure under loading were mostly oriented along the tensile direction. These results are fairly consistent with the results obtained by the simulation, although absolute values of the real principal stresses may be influenced by the heterogeneously evolved strain and the several assumptions used in the simulation.

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Fine crystalline LiFePO4 particles with an average secondary size of about 200 nm were synthesized in ethylene glycol (EG) solution at 393 K. Their molar ratio of Li:Fe:P was about 1.3:1:1, implying the precipitation of an impurity containing extra Li ions. The unit cell volume of crystalline LiFePO4 in heat-treated particles was larger than that in as-synthesized particles. The Fe K absorption edge in the X-ray absorption spectrum was shifted toward a lower energy position by heat treatment. These results suggest that the composition of crystalline LiFePO4 in fine particles is modified by heat treatment because of the reaction with extra Li ions. Additionally, in the radial structural function obtained by Fourier transform of the extended X-ray absorption fine structure oscillation, the Fe-P correlation and Fe-Fe correlation peaks became high due to the heat treatment, implying the rearrangement of FeO6 octahedra and PO4 tetrahedra. In consequence of the above-mentioned structural changes, the electronic capacity of fine particles precipitated in EG solution was enhanced to about 150 mA/h by heat treatment at 673 K. (C) 2013 Elsevier B.V. All rights reserved.

Influence of tungstate ions on the transformation of chloride-containing green rust (GR(Cl-)) to fine goethite (alpha-FeOOH) particles due to the oxidation reaction via aqueous solution at about 300 K was investigated by in situ measurements of X-ray absorption spectra. Results showed that the transformation rate of GR(Cl-) in the suspension containing 5 mol% W was lower than that in the suspension without tungstate ions. Almost all tungstate ions in the suspension were adsorbed on GR(Cl-) and alpha-FeOOH. It is probable that the adsorption of tungstate ions reduces the transformation rate of GR(Cl-) and also leads to the precipitation of fine particles. (C) 2014 Elsevier Ltd. All rights reserved.

FeCo alloy particles synthesized by liquid phase reduction are disorder distribution of the alloying elements in bcc crystalline lattice. The particle size dependence of thermally ordering behavior during heating was investigated. Superlattice lines such indices as 100, 111 etc., which appear in the x-ray diffraction pattern when the atomic arrangement is ordered, are difficult to detect due to quite small difference between Fe and Co in the atomic x-ray scattering factor. In this study, the energy near to Fe K absorption edge for incident x-ray was used in order to apply the anomalous x-ray dispersion effect. From results of the in situ heated x-ray diffraction experiments using the Synchrotron radiation source, different ordering-onset temperature was observed for the two samples with different particle size. This is considered due to a difference on the lattice distortion and its elimination during heating.

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Rare earth-doped BaZrO3 is a very attractive material in electrochemical applications due to its proton conductive property. In this work, powder X-ray diffraction patterns of BaZr0.8M0.2O3- (M=Sc, Eu, Sm, Dy) were collected using synchrotron radiation, and also using characteristic X-ray of CuK in dry and wet atmospheres at high temperature. Then, a combined interpretation of the diffraction patterns was established by using Rietveld refinement. The results revealed that an obvious lattice expansion was observed for BaZr0.8M0.2O3- (M=Sc, Eu, Sm, Dy) in wet O-2 compared with the case in dry condition, indicating a chemical expansion effect on lattice volume by incorporating water into lattice. Eu, Sm, and Dy cations occupied both A- and B-sites of BaZrO3 crystalline lattice, whereas Sc cations were determined to occupy B-site only. These results indicate clearly an increasing tendency toward A-site occupation for the rare earth cations in BaZrO3 with an increasing radius.

In situ measurements of X-ray absorption spectra at an Fe K absorption edge were carried out during the transformation of chloride-containing green rust (GR(Cl-)) to oxyhydroxide (that is, lepidocrocite (gamma-FeOOH)), by oxidation via aqueous solution. Results showed that the Fe K absorption edge in X-ray absorption near-edge structure (XANES) spectrum shifted toward the higher energy side with increasing oxidation time. The factor analysis of the XANES spectra, using reference data, implied that dissolution of GR(Cl-) and precipitation of gamma-FeOOH occur simultaneously. The fraction of gamma-FeOOH in the suspension increased continuously with increasing oxidation time, in response to the continuous decrease of the fraction of GR(Cl-). The results lead us to conclude that GR(Cl-) transforms to gamma-FeOOH during oxidation under the present experimental conditions.

Nickel (Ni) is expected to be an attractive anode material for protonic ceramic fuel cells using Y-doped BaZrO3 (BZY) as an electrolyte, since Ni shows good catalytic properties for the anode reaction, and NiO is a sintering aid for BZY. In this work, a systematic investigation has been performed to reveal the influence of Ni incorporation on structural and electrochemical properties of BZY. Then, some new knowledge was obtained; the important point is that Ni cations occupy the interstitial position of (1/2, 0, 0) in the lattice of BZY, with a greatly Ba-deficient environment. As a result, Ba cations were possibly driven to the grain boundary and induced the formation of a liquid phase, which promoted the sintering process. However, the occupation of Ni on this (1/2, 0, 0) position also resulted in a negative influence on conductivity. A careful processing is required to apply Ni as the electrode in BZY based fuel cells.

Novel Ni-Pd nanocubes of a few tens of nm in size encased in a Pt cage have for the first time been synthesized using a long-chain alcohol reduction process. The unique distribution of Pt atoms in these particles holds the key for the design of high turnover catalysts for the future.

White X-ray diffraction with micro-beam synchrotron radiation was used to analyze microscopic stress evolved in coarse grains of a twinning-induced plasticity Fe-Mn-C steel under tensile loading. In addition, electron backscatter diffraction (EBSD) was used to determine the crystal orientation of grains in the polycrystalline Fe-Mn-C steel. Based on these orientation data, the stress and strain distribution in the microstructure of the steel under tensile loading was estimated using an FEM simulation where the elastic anisotropy or the crystal orientation dependence of the elasticity was taken into account. The FEM simulation showed that the strain distribution in the microstructure depends on the crystal orientation of each grain. The stress analysis by the white X-ray diffraction indicated that the direction of the maximum principal stresses at measured points in the steel under tensile loading are mostly oriented toward the tensile direction. This is qualitatively consistent with the results of by the FEM simulation, although absolute values of the principal stresses may contain the effect of heterogeneous plastic deformation on the stress distribution.

The ordering process of FePt nanoparticles synthesized in polyol solution at 383 K was investigated. Whereas X-ray diffraction peaks of the as-synthesized specimen corresponded to the fcc structure, the Fe-O correlation and Pt-O correlation peaks were observed in the radial structure functions of Fe and Pt atoms obtained by X-ray absorption spectroscopy. Thus, the as-synthesized specimen was composed of crystalline FePt alloy phase and poorly crystallized Fe- and Pt-oxide phase. In X-ray diffraction patterns of the specimens which were heat-treated at temperatures above 568 K in a mixture of 5% H in Ar, diffraction peaks corresponding to superlattice lines were observed. Although the lattice constants of the as-synthesized specimen were much larger than that of the bulk fcc-FePt alloy with equiatomic composition, the lattice constants of the specimen heat-treated at 1173 K were very close to the bulk L1(0)-FePt alloy. Additionally, in the radial structure function, peaks corresponding to the Fe-O and Pt-O correlations disappeared and peaks corresponding to Fe-Pt (or Fe) and Pt-Fe (Pt) correlations clearly appeared after heat treatment at temperatures above 568 K. Consequently, it is highly probable that the disorder-order transformation of FePt nanoparticles synthesized in polyol solution is accompanied by compositional homogenization due to the reduction of the poorly crystallized Fe- and Pt-oxide phase.

Microscopic residual stress evolution in different austenite (gamma) grains during shape memory process in an Fe-Mn-Si-Cr alloy was investigated using the white X-ray microbeam diffraction technique. The use of high-energy white X-ray microbeam with small beam size allowed us to measure the microscopic residual stress in coarse gamma grains with specific orientation. After tensile deformation large compressive residual stress was evolved in gamma grains due to the formation of stress-induced epsilon martensite, but upon recovery heating it almost disappeared as a result of reverse transformation of martensite. The magnitude of compressive residual stress was higher in grains with orientations close to &lt; 144 &gt; and &lt; 233 &gt; orientations than in a grain with near &lt; 001 &gt; orientation. Analysis of the microstructure of each grain using electron backscattering diffraction suggested that the difference in the magnitude of compressive residual stress could be attributed to different martensitic transformation characteristics in the grains. (C) 2013 Elsevier B.V. All rights reserved.

Size-controlled nickel nanocrystals have been successfully synthesized using 2-octanol as the reducing agent. The elucidation of the reduction mechanism of nickel ions by 2-octanol was monitored by using UV-vis spectrometry, FT-IR spectrometry, X-ray diffractometry and transmission electron microscopy and the formation of intermediate layered hydroxides that subsequently undergoes reduction to metallic nickel was identified. Although, the nickel particles obtained in the 2-octanol-Ni acetate system were irregularly shaped with size in the sub-micrometer range, the addition of surfactants, hydroxyl ions and metal seed particles to the alcoholic system facilitated the synthesis of nanocrystals with controlled size and size distribution. The optimization of the synthesis conditions based on the above analytical data led to the preparation of a toluene-based suspension dispersing Ni nanoparticles with an average particle size of about 16 nm.

Y-doped BaZrO3 (BZY) is of the perovskite structure (ABO(3)), and is promising as an electrolyte in protonic ceramic fuel cells (PCFCs). However, factors limiting its protonic conductivity have not been clarified entirely, such as the unclear site occupancy of Y. In this work, X-ray diffraction patterns were collected utilizing synchrotron radiation with an incident energy close to the energy of the Y K absorption edge. Therefore, precise Rietveld refinement was performed to determine the site occupancy of Y by the anomalous dispersion effect. The results revealed that for the stoichiometric sample of BaZr0.8Y0.2O3-delta, Y only occupied the B-site. But in the Ba-deficient sample of Ba0.9Zr0.8Y0.2O3-delta, two perovskite phases with different compositions were observed. In the Y-poor phase, all Y occupied the B-site, while in the other greatly Y-rich and Ba-deficient phase, Y was found to occupy both A and B-sites. These results clearly indicate the tendency towards A-site occupation of Y with an increasing Ba-deficiency.

Magnetite (Fe3O4) particles were synthesized by oxidation of a hydroxyl chloride green rust (GR(Cl-)) suspension at room temperature. The formation process of Fe3O4 particles was characterized by X-ray diffraction, magnetization and electrochemical measurements. The results showed that a small amount of fine Fe 3O4 particles were nucleated when the supernatant solution of the as-synthesized GR(Cl-) suspension was replaced by deaerated water. By controlling the injection of oxygen gas at room temperature, Fe 3O4 particles of about 70 nm in diameter formed from such GR(Cl-) suspension, while goethite (α-FeOOH) particles were mainly obtained from the as-synthesized GR(Cl-) suspension under the same oxidation conditions. Hence, the saturation magnetization of final oxidation products obtained from the GR(Cl-) suspension in which the supernatant solution was replaced was about 60 emu/g, which was six times larger than that obtained from the as-synthesized GR(Cl-) suspension. In the early stage of the oxidation process, the oxidation-reduction potential (ORP) in the GR(Cl-) suspension in which supernatant solution was replaced was lower than that in the as-synthesized GR(Cl-) suspension. In addition, the value of pH of the former suspension was higher than that of the latter suspension. It is concluded that the formation of Fe3O4 particles is enhanced in solution with relatively low ORP and high pH. © 2013 ISIJ.

Since selective oxidation of alloying elements on the surface of-steel products influences their surface properties, characterization of the surface oxides which can be considered as non-metallic inclusions is of great importance. In this study, X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD) and X-ray absorption spectroscopy (XAS) were used for characterizing the formation process of Mn oxides on the surface of annealed Fe-Mn alloys under a low partial pressure of oxygen. The results obtained by XPS showed that the enrichment and oxidation of Mn occurs on the surface of the Fe-Mn alloys annealed under low oxygen partial pressure, and Mn oxides are formed in the metallic Fe matrix in the surface layers. XAS spectra using grazing-exit X-ray fluorescence measurements showed depth-resolved information on chemical state of Mn. These Mn oxides were identified as MnO (manganosite) by grazing-incident XRD measurements. It was found using in situ XRD measurements at high temperatures that the lattice constant of MnO increased with increasing annealing temperature, which attributed to the non-stoichiometry of MnO. These oxidation characteristics of Mn in the Fe-Mn alloys are discussed on the basis of thermochemical properties of Mn.

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A novel process for preparing scorodite particles with a diameter of approximately 20 mu m from Fe(II) and As(V) in aqueous solution has been developed by DOWA Metals and Mining. In the present study, the dissolution characteristics of iron and arsenic from the scorodite particles synthesized by this process have been investigated under different conditions. The results show that the concentration of arsenic dissolved from the particles in aqueous solution is very low, but it has a complicated dependence on the temperature and pH of the solution. Transmission electron microscopy (TEM) with an energy dispersive X-ray spectrometer (EDS) was used to analyze the morphology, structure, and composition of the scorodite particles. The results indicate that the scorodite particles exhibit a nearly octahedral shape with planes composed of almost (111) planes in the orthorhombic structure. The concentration of iron at the surface of the particles is higher than that of iron inside of the particles. This characteristic morphology, along with the minimal surface defects of the scorodite particles, is considered to be responsible for the low dissolution of arsenic from the particles in aqueous solution. Atmospheric temperature and solution conditions were also found to be important for the safe, long-term storage of arsenic using scorodite particles.

Nanoparticles of Ni carbide of about 50 nm in diameter were synthesized by the reduction of Ni salt in a polyol solution in the presence of polyvinylpyrrolidone (PVP). It was found that the aggregation of nanoparticles was suppressed when PVP was added to the polyol solution during synthesis. Diffraction peaks of the fcc and hexagonal structures were observed for the specimen synthesized without PVP. On the other hand, no peaks assigned to the fcc structure and no spontaneous magnetization were observed for the specimen synthesized with 50 g/L PVP, although pure bulk Ni are fcc structure and ferromagnetic at room temperature. Additionally, small peaks were observed in the X-ray diffraction pattern at 2 theta = 26.2, 35.7 and 47.8 degrees, originated not from the impurity phase but from the hexagonal phase. The specimen synthesized with 50 g/L PVP was fundamentally identified as Ni carbide with a Ni3C-type structure, as small peaks mentioned above were assigned to superlattice peaks. The structure parameters of the Ni carbide were refined by Rietveld analysis. It is concluded that the formation of the Ni carbide nanoparticles with Ni3C-type structure in the polyol solution is enhanced by the addition of PVP. [doi:10.2320/matertrans.M2012160]

The site selectivity of Sc, Y, Sm, Eu, and Dy in doped BaZrO3 was investigated. The measurement of water contents and conductivities of the samples were performed. The results revealed that for doping rare-earth cations into BaZrO3, all the examined dopants mainly occupied B-site, while a partial A-site occupation of Sm and Eu was significantly recognized. Sm and Eu are considered to be more amphoteric for doping into BaZrO3. The concentration of hydroxide ions in the sample of BaZr0.8Dy0.2O3-delta hydrated in wet Ar was obviously higher than that hydrated in wet O-2 at the same humidification level. The bulk conductivity of BaZr0.8-DY0.2O3-delta in wet Ar or H-2 is higher than that in a dry one, indicating the generation of protonic conductivity of BaZr0.8Dy0.2O3-delta. The strong dependence of conductivity on partial pressure of oxygen was also recognized. The bulk conductivities of BaZr0.8Dy0.2O3-delta. in wet Ar and H-2 were comparable to that of BaZr0.8Y0.2O3-delta. (c) 2011 Elsevier B.V. All rights reserved.

High frequency properties of (a) as-synthesized and (b) flattened by ball milling Fe-based alloys particles and their potential as antenna materials is reported. The high frequency properties of Fe-Co nanoparticles exhibited a resonance peak in the range of a few gigahertz (GHz), and the resonance peak shifted to a higher region for decreasing particle size. However, magnetic permeability was not high enough to be used as high performing electromagnetic wave absorbers. On the other hand, the permeability of Fe-Ni particles at 1 GHz was 2.5 and the magnetic loss was 0.36. However, permeability was enhanced to a value of more than 3 and the magnetic loss decreased by more than half, when the dispersibility and planular aggregates were realized through ball milling. Additional experiments suggested that the particle aggregation had greater influence in the high frequency properties than the composition and magnetic properties. Similarly, when Fe50Co50 particles were also subjected to ball milling, their magnetic loss decreased below the values achieved by Fe-Ni and suggested the possibility of becoming a potential candidate for antenna applications. (C) 2012 American Institute of Physics. [doi:10.1063/1.3678296]

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金属鉄表面では水分や酸素の影響を受けて、Fe(II)やFe(III)からなる酸化物が生成する。その酸化物のひとつにgreen rustがあり、green rustには多くのFe(II)やアニオンが含まれている。ここでは、green rustの室温での酸化に伴う局所構造変化を明らかにするために、その場X線吸収分光測定を行った。それらの結果から、Fe(II)からFe(III)への酸化に伴う、green rustの消滅およびFeOOHの生成の過程を示した。

The leaching characteristics of scorodite particles synthesized from Fe(II) under different conditions, such as reaction time and temperature, were investigated. The solution conditions, such as pH and temperature, were changed in leaching experiments. The results showed that the leaching characteristics depend on the synthesis temperature of scorodite particles, particle size, type of solvent and so on. Since the amount of As dissolved from particles with the high Fe/As molar ratio is relatively low, the Fe/As molar ratio of the particles is an important factor to control the dissolution of As from scorodite particles. The results of leaching tests with repeated renewal solution showed that pH of solution is the most important factor in the As dissolution. It was found that the addition of goethite to the scorodite is also effective to reduce the amount of As in solution. (C) 2011 Elsevier B.V. All rights reserved.

In this study, influences of P on the microstructure, mechanical properties, and retained austenite characteristics in transformation induced plasticity (TRIP) steels were investigated. Microstructure of 0.2mass%P containing TRIP steel was inhomogeneous and it resulted in deterioration of the mechanical properties. Retained austenite characteristics such as volume fraction and carbon concentration were also affected by P. The stability of retained austenite in P containing TRIP steel was different from that in P-free TRIP steel. Such difference in the stability of retained austenite was attributed to the effect of the carbon concentration in retained austenite as well as their different microstructure.

Low temperature synthesis of equiatomic FePt alloy nanoparticles with the FCC structure was carried out by the polyol process in the presence of NaOH at above 383 K. The Pt content in the FePt alloy particles decreased with decreasing reaction temperature and equiatomic FCC-FePt alloy nanoparticles were successfully obtained at 383 K. When the FCC-FePt alloy nanoparticles synthesized at 383 K were annealed at 573 K, a partially ordered phase with the L1(0) structure was observed. For comparison, FCC-FePt alloy nanoparticles were synthesized at 468 K without adding NaOH. Results showed that the degree of atomic ordering of the sample synthesized at 383 K with the addition of NaOH was higher than those obtained at 468 K after annealing at low temperatures. Thus, it is concluded that the temperature employed during the synthesis of FCC-FePt alloy nanoparticles affects the ordering transformation temperature.

Dowa Metals & Mining Co. Ltd. has developed and plant-practiced a unique scorodite synthesis technology (DMSP (R)) for arsenic immobilization by oxidizing Fe(Il) ions in the presence of As(V) ions. Dowa has improved the DMSP (R) technology and has developed the process extensively for other applications. This paper focuses on the applicability of the DMSP (R) for various cases of copper smelting, and introduces other technologies for fixing arsenic and recycling gallium from GaAs, simultaneously processing (fixing) arsenic and thallium, and fixing and recovering arsenic from dilute arsenic solutions. The DMSP (R) was found to be applicable not only for various processes in nonferrous smelting, but also for other applications with a high potential for reducing environmental problems.

Dowa's scorodite, synthesized by oxidation of Fe(II) ions in the presence of As(V) ions at atmospheric pressure, was characterized. The scorodite was well crystallized and had a very low solubility. To examine the conditions for stable storage of the scorodite for long periods, experiments with various synthesis and leaching conditions were done. The scorodite had a very low arsenic solubility in sea water. It was estimated in consecutive leaching tests that the arsenic concentration would eventually converge to zero. The prevention of arsenic leaching by adding goethite or ferrihydrite was limited in some cases. Very low toxicity was confirmed by toxicity tests. The investigation results suggest that disposal at a specifically designed well-controlled storage place is preferable for the scorodite whose toxicity had been made sufficiently low. Disposal to an isolated final disposal site with more stringent prevention for the outflow of toxic substances was thought another option.

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The microstructure of transformation induced plasticity (TRIP) steels was characterized by means of electron backscattering diffraction (EBSD) technique to identify and quantify their different microstructures such as ferrite, bainite, and retained austenite. Further, the strain distribution in ferrite and retained austenite was analyzed during deformation. The TRIP steels were annealed by austempering for different durations to investigate the effect of the austempering time on the volume fraction change of the microstructural constituents. The quantitative analysis by EBSD coupled with an image contrast analysis revealed that the amount of retained austenite decreased and the amount of bainite increased with increasing austempering time. The mechanical properties of the TRIP steels were also affected by the austempering time. The maximum elongation was obtained in the sample austempered for 5 min, probably because of the good stability of retained austenite. The strain distribution in bcc and fcc phases during tensile deformation was characterized by evaluating the changes in the average local misorientation of the phases. (C) 2011 Elsevier B.V. All rights reserved.

The synthesis of novel cubic shaped-standing Ni-Pt alloy nano-particles is reported. Incorporation of a few percent of Pt atoms in the presence of chloride ions and oleylamine, which helps to control the growth and prevents agglomeration, facilitates the formation of highly monodispersed cubic shaped particles. Furthermore, these cubic-shaped particles stand on their corners, which is believed to be due to the magnetic interaction between particles whose easy axis is in the [111] direction. The formation of these unique shaped particles with different sizes has been realized by using platinum particles as seeds. It should be noted that these particles are highly reproducible and holds great potential for catalytic applications.

We report a large decrease in tetragonal to cubic phase transformation temperature when grain size of bulk CuFe2O4 is reduced by mechanical ball milling. The change in phase transformation temperature was inferred from in situ high temperature conductivity and x-ray diffraction measurements. The decrease in conductivity with grain size suggests that ball milling has not induced any oxygen vacancy while the role of cation distribution in the observed decrease in phase transformation temperature is ruled out from in-field Fe-57 Mossbauer and extended x-ray absorption fine structure measurements. The reduction in the phase transformation temperature is attributed to the stability of structures with higher crystal symmetry at lower grain sizes due to negative pressure effect. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3493244]

Some Fe-based alloys containing Mn exhibit characteristic plastic deformation modes such as twin induced plasticity (TWIP) and transformation induced plasticity (TRIP). In this study, microstructural changes induced by a tensile test in polycrystalline Fe-25% Mn-0.6% C alloys exhibiting TWIP were characterized. Electron backscatter diffraction (EBSD) and two-dimensional (2D) X-ray diffraction (XRD) measurements using synchrotron radiation were carried out to characterize the microstructure and crystallographic orientation of the polycrystalline alloy samples. The samples were deformed by 10%, 30%, and 60% in a tensile test. The EBSD results showed that deformation twins appeared to form preferentially in grains with large Schmid factors for twinning, and these had an orientation of nearly &lt; 011 &gt; - &lt; 111 &gt; parallel to the tensile direction. In addition to twinning, plastic deformation by dislocation slip was also observed in the interior of grains and near grain boundaries. In the polycrystalline sample, the heterogeneous strain by twinning and dislocation slip evolved overall with tensile strain. The 2D-XRD results also indicated that dislocation slip as well as twinning occurs in tensile deformed samples, and the contribution of twinning and dislocation slip in grains depends on tensile strain. Therefore, multiple plastic deformation modes consisting of different deformation twins and dislocation slips are attributed to large elongation in Fe-Mn-C alloys. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11

Evolutions of martensitic transformation and texture during cold rolling in novel bcc Fe-Mn-Al-Ni-Cr alloys were studied. X-ray diffraction (XRD) and electron backscattering diffraction (EBSD) analyses revealed that this alloy undergoes a -&gt; epsilon -&gt; gamma' martensitic transformation during deformation. At a 20% cold rolling strain, most of the a phase transformed into gamma', and the transformed gamma' phase had a Kurdjumov-Sachs (K-S) relationship with the parent a phase. Strong {hkl}&lt; 111 &gt; and weak {110}&lt; 001 &gt; transformation textures were formed after deformation. This texture evolution appeared to be related to the variant selection that occurred during the martensitic transformation.

Fluorescence yield (FY) X-ray absorption spectroscopic experiments with a grazing-exit geometry for detection of emitted fluorescence were carried out. The observed XAFS spectra provide the information about depth-resolved chemical state in the surface layer of film materials through the take-off angle dependence of the escape depth of the fluorescent X-ray emitted from the sample. For La1-xSrxMnO3 films which are the oxygen electrode materials of a solid-oxide fuel cell (SOFC), the Mn K XANES spectra were measured using undulator radiation at BL37XU in SPring-8 synchrotron radiation facility. The results of the conventional FY-XAS indicated differences due to distortion of MnO6 caused by different temperature, oxygen partial pressure p(O-2) and voltage loading conditions in the spectrum profiles. From the results of the angle-resolved measurements at 973 K in air, a depth-dependent variation of the Mn K XANES profile in surface region of the film was observed. Though such depth-dependence was also measured in case of lower p(O-2) or voltage loading conditions at the same temperature, the absorbance proportion of absorbing bands contributing the change was different among the split 1s -> 4p transition bands. These results indicate a difference in surface region caused by a difference between the surface and the inside of the film in the chemical potential of oxygen. Copyright (C) 2010 John Wiley & Sons, Ltd.

The first report on the synthesis of submicron sized pure Fe particles solely by polyol process was published by the authors a couple of years ago. Recent applications in biomedical fields demand stable and high saturation magnetization particles of sizes below 100 nm. In this paper, we report the successful synthesis of size controlled Fe nanoparticles ranging between 90 and 10 nm by polyol process using H2PtCl6 as the nucleating agent. The size of cubic Fe particles synthesized without the nucleating agent was 150 nm. The gradual decrease in size was observed with the increase in Pt ion concentration and the minimum size of 10-15 nm was achieved under a Pt ion concentration of 2 x 10(-7) M. The Fe particles retained their cubic morphology for sizes above 25 nm and became spherical and agglomerated with further reduction in size. Saturation magnetizations of Fe particles were size dependent and varied between 210 and 90 Am-2 kg(-1). The as-prepared particles with diameters up to 60 nm were highly stable in air due to the formation of a thin passive layer of Fe-oxide shell. Consequently, this particle is considered a better candidate for biomedical application than magnetite due to higher saturation magnetization and biocompatible nature of the oxide layer formed on the surface. (C) 2010 Elsevier B.V. All rights reserved.

The first report on the synthesis of submicron sized pure Fe particles solely by polyol process was published by the authors a couple of years ago. Recent applications in biomedical fields demand stable and high saturation magnetization particles of sizes below 100 nm. In this paper, we report the successful synthesis of size controlled Fe nanoparticles ranging between 90 and 10 nm by polyol process using H2PtCl6 as the nucleating agent. The size of cubic Fe particles synthesized without the nucleating agent was 150 nm. The gradual decrease in size was observed with the increase in Pt ion concentration and the minimum size of 10-15 nm was achieved under a Pt ion concentration of 2 x 10(-7) M. The Fe particles retained their cubic morphology for sizes above 25 nm and became spherical and agglomerated with further reduction in size. Saturation magnetizations of Fe particles were size dependent and varied between 210 and 90 Am-2 kg(-1). The as-prepared particles with diameters up to 60 nm were highly stable in air due to the formation of a thin passive layer of Fe-oxide shell. Consequently, this particle is considered a better candidate for biomedical application than magnetite due to higher saturation magnetization and biocompatible nature of the oxide layer formed on the surface. (C) 2010 Elsevier B.V. All rights reserved.

In this study, evolution characteristics of the texture and microstructure of Fe-Mn-Si-Cr shape memory alloys (SMAs) upon tensile deformation were investigated. Electron backscatter diffraction analysis revealed that the tensile deformation in the rolling direction (RD) of sample sheets resulted in the evolution of microstructure containing stress-induced epsilon martensite and texture components belonging to &lt; 1 1 1 &gt; and &lt; 1 0 0 &gt;//RD fibers. Quantitative measurement of epsilon martensite formation in individual austenite grains at the strain levels of 4% and 5% revealed that among the &lt; 1 0 0 &gt;, &lt; 1 0 1 &gt;, and &lt; 1 1 1 &gt; grains which are oriented along the tensile direction, &lt; 1 0 1 &gt; oriented grain showed the highest epsilon martensite formation rate. In the recrystallized state, the volume fraction of &lt; 1 0 1 &gt; texture component in 20% tensile deformed samples was slightly higher in the transverse direction (TD) than in the RD. Because of that preferred orientation recovery strain was slightly higher in the TD sample than in the RD sample. (C) 2010 Elsevier B.V. All rights reserved.

Alloying elements added to steel for improving surface properties such as corrosion resistance are often enriched to the surface of the alloys during annealing at high temperatures. Their behavior depends on difference in their chemical characters and the condition of annealing. In this study, nondestructive depth-resolved analysis of amount distribution and chemical state of alloying element by using X-ray fluorescence analysis (XRF) technique in combination with X-ray absorption spectroscopy (XAS) in order to characterize the enrichment and oxidation of manganese on the surface layers of an Fe-Mn alloy annealed under low oxygen partial pressure. The experiments were carried out using a two-dimensional detector with geometrical arrangement of grazing exit in detection of fluorescence X-ray emitted from sample surface. The results showed that manganese was enriched to surface layers of the Fe-Mn alloys during annealing at high temperatures and formed as manganese oxide. The preferential oxidation of manganese by annealing under low oxygen partial pressure is considered the driving force for their enrichment on the alloy surface.

Cr in Fe-Cr alloys often forms some different phase of oxides during annealing at high temperatures. The phases of Cr oxides are determined depending on the annealing condition such as temperature and oxygen partial pressure. In this study, depth-resolved X-ray fluorescence analysis (XRF) of Fe and Cr were carried out using a two-dimensional pixel array detector with geometrical arrangement of the grazing exit in detection of fluorescence X-ray emitted from the sample surface, in order to characterize the depth-directional distribution of the elements in the surface layers of Fe-Cr alloys annealed under low oxygen partial pressure. In addition, depth-resolved X-ray absorption spectra will also be able to be obtained by measuring the incident X-ray energetic dependencies of the fluorescence intensity. These techniques facilitate non-destructive measurement of the elemental distribution and the phase of metal or oxides in depth direction. The experiments were performed at the BL01B1 of SPring-8 synchrotron radiation facility. The results showed that Cr was enriched and covered on the surface of the alloys during annealing and formed as Cr2O3 or FeCr2O4. The phase and thickness of formed oxides depended on the alloy composition and the annealing conditions.

The oxidation of hydrosulphate green rust (GR2(SO(4)(2-))) suspension containing different chromium ion species was investigated by X-ray diffraction, X-ray absorption spectroscopy and transmission electron microscopy. The pH, oxidation-reduction potential and amount of dissolved oxygen in aqueous solutions were measured during the reactions. The results show that the addition of Cr(III)(2)(SO(4))(3) solution suppresses the transformation of GR2(SO(4)(2-)) into iron oxyhydroxides and oxides in aqueous solution, while the addition of Na(2)Cr(VI)O(4) solution promotes the transformation of GR2(SO(4)(2-)) in which Cr(VI) is reduced to Cr(III); alpha-FeOOH particles were refined by the addition of the chromium ions. (C) 2009 Elsevier Ltd. All rights reserved.

Iron oxide nanoparticles of reduced oxidation state, mainly in the form of magnetite, have been synthesized utilizing a new continuous, gas-phase, nonpremixed flame method using hydrocarbon fuels. This method takes advantage of the characteristics of the inverse flame, which is produced by injection of oxidizer into a surrounding flow of fuel. Unlike traditional flame methods, this configuration allows for the iron particle formation to be maintained in a more reducing environment. The effects of flame temperature, oxygen-enrichment and fuel dilution (i.e. the stoichiometric mixture fraction), and fuel composition on particle size. Fe oxidation state, and magnetic properties are evaluated and discussed. The crystallite size. Fe(II) fraction, and saturation magnetization were all found to increase with flame temperature. Flames of methane and ethylene were used, and the use of ethylene resulted in particles containing metallic Fe(0), in addition to magnetite, while no Fe(0) was present in samples synthesized using methane. (c) 2010 Elsevier Ltd. All rights reserved.

We report the high-frequency properties of sub-micron-sized Fe-Co particles synthesized with a polyol process, and what influence hard magnetic and non-magnetic oxide layers had on those high-frequency properties. The Fe-Co particles exhibited a resonance peak in the range of a few gigahertz, and the resonance peak shifted to a higher region for decreasing particle size. Furthermore, the presence of a multi-resonance peak in the gigahertz range was recorded. The permeability of surface-oxidized particles decreased and the resonant frequency shifted to a higher region for increasing CoFe₂O₄ layer thickness on the surface of the particles. However, SiO₂ coating did not influence the resonant frequency even though the permeability decreased due to the decrease in the volume fraction of FeCo particles in the sample.

Alloying elements are added to steel for improving surface properties such as corrosion resistance. The alloying elements exhibit different chemical characters, and they are often enriched to the surface of the alloys during annealing at high temperatures. In this study, depth-resolved X-ray absorption spectroscopy (XAS) measurements were carried out using a two-dimensional detector with geometrical arrangement of grazing exit in detection of fluorescence X-ray emitted from sample surface, in order to characterize the enrichment and oxidation of manganese on the surface layers of an Fe-Mn alloy annealed under low oxygen partial pressure. This technique facilitates non-destructive measurement for characterizing the compositional distribution of manganese in the depth direction. The results showed that manganese was enriched to surface layers of the Fe-Mn alloys during annealing at high temperatures and formed as manganese oxide. The preferential oxidation of manganese by annealing under low oxygen partial pressure is considered the driving force for their enrichment on the alloy surface.

X-ray photoelectron spectroscopy (XPS) has been used for analyzing the surface composition of polyol process-derived Fe30Co70, Fe50Co50, and Fe70Co30 alloy nanoparticles with diameters 50, 100 and 150 nm, respectively. These Fe-Co alloy particles have high oxidation resistance in the atmospheric environment even though their particle size is so small. The XPS results revealed that the concentration of iron at the surface of the as-synthesized Fe-Co alloy nanoparticles was lower than that in bulk and increased with increasing bulk cobalt composition, although the surface of nanoparticles was covered with native oxide layer formed during their exposure to atmosphere. This low concentration of iron and very thin oxide layer at the surface are considered to protect the particle from oxidation. The concentration of iron at the surface of Fe70Co30 nanoparticles increased when they were annealed at 573 K in N-2 and H-2 atmosphere. The results indicate that nonuniformity of the chemical composition between particle surface and core occurs during the formation of the same in polyol, and atomic diffusion at the surface of particle can occur even at relatively low temperature. The above is considered to arise from the difference in the chemical characteristics of iron and cobalt during co-precipitation in the polyol.

X-ray diffraction applied anomalous dispersion effect was used for characterizing the order-disorder transformation in Fe50Co50 fine particles synthesized by polyol process. The long range order parameter was estimated from the superlattice peak intensities in the diffraction pattern of particles annealed in the temperature range between 20 and 800 degrees C. The results showed that fine particles of as-synthesized Fe-Co have a disordered structure at room temperature, while the ordered structure is present, to a great extent, in Fe-Co bulk alloys. The fine particles of the disordered alloy were transformed to the ordered state by annealing up to about 450 degrees C. The magnetic properties of the Fe-Co alloy fine particles annealed at different temperatures were also investigated using a vibrating sample magnetometer, in which magnetic fields of up to 15 kOe were applied to samples at room temperature. The saturation magnetization of the as-synthesized particles increased with annealing temperature. This may be attributed to transformation from disordered to ordered structure, along with sintering. [doi:10.2320/matertrans.M2009251]

In-situ X-ray absorption spectroscopy (XAS) at the Fe K-edge X-ray absorption near edge was used to investigate the chemical change of LiFePO 4, which is a candidate cathode material for lithium ion batteries, during charge-discharge cycles. The relative amount of FePO4 formed in the LiFePO4 by the charge-discharge cycles was estimated from the XAS spectra. The results show that the amount Of FePO4 in the LiFePO4 increased with charging and decreased with discharging. While a linear relationship between the relative amount of FePO4 and electrical capacity was observed during the initial charging, it deviated from linearity during the charge-discharge cycles. This may be attributed to the irreversible diffusion paths of lithium ions and/or the partial formation of inactive FePO4 in the LiFePO4 during the charge-discharge cycles. It is shown that in-situ XAS has sufficient potential to nondestructively characterize heteroseneous electrochemical reactions in electrode materials during charge-discharge cycles. ©2010 The Japan Institute of Metals.

To clarify the role of Cu in the oxidation of green rust (GR(Cl-)), which contains Fe(II) and Fe(III) ions, Cu-containing GR(Cl-) suspensions were synthesized and oxidized under various reaction conditions using nitrogen gas containing oxygen as the oxidant. X-ray diffraction (XRD) measurements were performed for analyzing the solid particles formed in the synthesis and oxidation steps. Upon the addition of Cu ions, a part of GR(Cl-) was oxidized to Fe3O4, while the Cu ions were reduced to metallic Cu (Cu(0)) in the GR(Cl-) suspensions. The pH and oxidation-reduction potentials (ORPs) of the aqueous solutions were measured during oxidation. The results showed that after oxidation, the pH of the solutions decreased. while the ORP increased. After the introduction of oxygen, GR(Cl-) was converted to iron oxides such as gamma-FeOOH, alpha-FeOOH, and Fe3O4. The rate of conversion of GR(Cl-) to Fe3O4 was enhanced after the addition of Cu ions. The oxidation processes of the GR(Cl-) suspension containing copper revealed a reaction process in the ORP curve, which may be attributed to the reaction of Cu(0)/Cu(II) in the aqueous solution. [doi: 10.2320/matertrans.M2009279]

X-ray photoelectron spectroscopy (XPS), electron microprobe microanalysis (EPMA), and secondary ion mass spectrometry (SIMS) have been used for analyzing the chemical composition in surface layers of iron-base alloys. Samples analyzed in this study were a ferritic Fe-Mn alloy annealed under low partial pressure of oxygen and an austenitic Fe-Mn-Si-Cr alloy annealed under vacuum. The XPS results showed that manganese was enriched and oxidized while iron was metallic in the surface layer of the Fe-Mn alloy annealed under a low partial pressure of oxygen. The EPMA results showed that manganese was depleted while chromium was enriched in the Surface layer of the Fe-Mn-Si-Cr alloy annealed under vacuum. The SIMS depth profiles coupled with the EPMA results indicated that the enrichment of chromium in the surface layer improves the oxidation resistance of the alloy. The enrichment and depletion of manganese in the surface layer is discussed on the basis of the thermodynamic properties of the iron-manganese system.

Quantitative X-ray diffraction analysis coupled with the reverse Monte Carlo simulation technique has been made for characterizing the structure of iron oxyhydroxides and oxides formed from green rust (GR) with manganese ions and nickel ions in aqueous solution. The main component of GR(ox) was found to be alpha-FeOOH in all cases presently investigated. The distortion in the atomic-scale structure of alpha-FeOOH particles was clearly found to be induced by the existence of manganese ion. Such structural variation was not observed in the structure of alpha-FeOOH obtained from GR(ox) with nickel ion.

Removal of selenate ion from the liquid phase by hydroxysulfate green rust (GR(SO4)) was investigated in the pH range from 7.5 to 10.0. Batch tests showed that the total selenium concentration decreased more rapidly with increasing pH. However, the amount of selenium removed from the liquid phase increased as the pH decreased. X-ray absorption spectrometric analysis demonstrated that the Se(VI) in the selenate ion was reduced to elemental selenium Se(0) at pH 9.0, whereas the existence of small amount of intermediate Se(IV) was detected at pH 7.5. Comparing the mass balance of the amount of consumed ferrous iron in GR(SO4), [Delta Fe(II)], and the amount of Se(VI) removed from the liquid phase, [Delta Se(VI)], [Delta Fe(II)] is approximately six times larger than [Delta Se(VI)] in mol units. This is also indirect but convincing evidence that the oxidation of Fe(II) in GR(SO4) leads to the simultaneous reduction of Se(VI) to Se(0). Powder X-ray diffraction analysis showed that the end product of GR(SO4) depends on the pH: magnetite for pH > 9.0, goethite for pH < 8.0, and their mixture at pH 8.5. These results indicate that the solution pH has a significant effect on the reaction path of selenate removal by GR(SO4). (C) 2009 Elsevier Ltd. All rights reserved.

A novel method for synthesizing large scorodite (FeAsO4 center dot 2H(2)O) particles was recently developed for the fixation of arsenic. This method involves the coprecipitation of scorodite particles from an Fe(II) and As(V) aqueous solution at approximately 95 degrees C by oxygen injection. In order to understand the process of coprecipitation of scorodite particles by this method, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used for characterizing reaction products extracted from the suspension during the reaction. The SEM observation showed that the formation of large scorodite particles was almost completed after a reaction time of 3 h, and then, fine particles precipitated on the large particles by further reactions. The XRD results indicated that scorodite particles with specific lattice parameters were formed in the reaction. The XPS results indicated that the arsenic composition on the surface of the scorodite particles decreased until 3 h from the start of precipitation reaction and increased thereafter. These results correspond to the results on the morphology of the scorodite particles obtained by SEM. Furthermore, X-ray absorption spectra (XAS) in the range of X-ray absorption near edge structure (XANES) were measured for gel-like reaction products formed in the initial stages of the reaction. The spectra revealed that the gel-like reaction products were composed of Fe(H) and Fe(III). The coprecipitation of scorodite particles synthesized by the novel method is discussed on the basis of these results together with previous results on the analyses of iron and arsenic concentrations in solution. [doi: 10.2320/matertrans.M-M2009804]

Green rust (GR) containing both ferrous (Fe(II)) and ferric (Fe(III)) ions is formed in an aqueous solution with a relatively low electrochemical potential. In this study, in order to understand the formation and oxidation of GR, a suspension of GR containing chloride ions (GR(Cl-)) was synthesized and subsequently oxidized by injecting nitrogen gas containing oxygen under different conditions. X-ray diffraction (XRD) measurements were performed for identifying the solid particles formed under different conditions. The results show that the GR(Cl-) suspension was formed from specific concentrations of hydroxyl, ferrous, and ferric ions. The pH values and oxidation-reduction potential (ORP) of the aqueous solution were measured during oxidation of the GR(Cl-) suspension. It was observed that because of oxygen injection, GR(Cl-) was transformed into iron oxides such as alpha-FeOOH, gamma-FeOOH, and Fe3O4. These iron oxide and oxyhydroxide species formed by oxidation were dependent on the oxidation conditions such as temperature. This suggested that conditions of aqueous solution are crucial for the transformation of GR(Cl-) into different iron oxides and oxyhydroxides.

Debye rings obtained by synchrotron X-ray diffraction were analyzed for investigating structural changes caused by stress-induced martensitic transformation and reverse transformation of a polycrystalline austenitic Fe-Mn-Si shape memory alloy. The chemical composition of the shape memory alloy was Fe-28 mass%Mn-6 mass% Si-5 mass%Cr. The results showed that a part of the austenitic gamma phase was transformed to a martensitic phase by room-temperature tensile deformation, and the F phase was reversely transformed by subsequent heating. Diffraction intensities in Debye rings changed non-uniformly on tensile deformation and heating, indicating that occurrences of the stress-induced and reverse transformation depend on the crystallographic orientations of grains with respect to the tensile direction. The optimum recovery strain induced h the reverse transformation was obtained for a sample deformed by about 10% tensile strain, which was consistent with the structural changes caused by the reverse transformation. X-ray diffraction lines were shown to be broadened by tensile strain. This indicated that irreversible deformation due to dislocations restricted the reverse transformation, leading to the optimum recovery strain. [doi: 10.2320/matertrans.MRA2008211]

Green rust (GR) consisting both of Fe(II) and Fe(III) was formed in an aqueous solution with a relatively low electrochemical potential. In order to understand both the reduction and oxidation reactions of copper in a GR suspension, the aqueous solution containing Green Rust 2(SO42-) (GR2(SO42-)) was mixed with a copper sulfate solution and it was subsequently oxidized by passing a gas containing oxygen at room temperature. X-ray diffraction, X-ray absorption spectroscopy, and transmission electron microscopy were used for characterizing the reaction products. Copper ions were found to be reduced to metallic copper in the GR2(SO42-) suspension, while a part of GR2(SO42-) was oxidized to be transformed to alpha-FeOOH. The pH and oxidation-reduction potential values of the aqueous Solution were measured during the reactions. The importance of the reduction of Cu(II) to metallic copper occurred in the GR2(SO42-) suspension, and the oxidation processes of the suspension containing metallic copper was suggested as distinct reaction stages. These reaction stages are considered to be attributed to the different electrochemical potential of Cu(II)/Cu(0) and Fe(III)/Fe(II) in solution. [doi: 10.2320/matertrans.MAW200818]

Measurements of X-ray absorption fine structure (XAFS), that is X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), were performed for characterizing the reactions of hydrosulphate green rust (GR) with copper or nickel sulphate ions. Fe K edge XANES spectra showed that a part of Fe (II) in GR2 was oxidized by the addition of copper sulphate ions, while Fe (II) in GR was not oxidized by the addition of nickel sulphate ions. Cu K edge and Ni K edge XANES spectra showed that copper sulphate ions were reduced to zero charge copper in the GR suspension, whereas nickel sulphate ions were not reduced. Radial structural functions for iron obtained from Fe K edge EXAFS spectra indicated that the structure of GR consisted of corner sharing of structural units formed by FeO6 octahedra. Radial structural functions for copper and nickel also indicated that copper sulphate ions were transformed to metallic copper with the face-centered cubic structure in the GR suspension, whereas the local structure of nickel sulphate ions were unchanged. XANES and EXAFS data of GR oxidized by a H 2O2 solution were also investigated for comparison.

The X-ray absorption near edge structure (XANES), the extended X-ray absorption fine structure (EXAFS) and X-ray diffraction (XRD) measurements were used for characterising the effect of the addition of copper sulphate ions on the chemical state and local structure of hydrosulphate green rust (GR). Fe K edge XANES spectra showed that Fe(II) in GR was partially oxidised by the addition of the copper sulphate solution. Cu K edge XANES spectra showed that the copper sulphate ions in the GR suspension were reduced to zero charge copper. Radial structural functions indicated that the structure of GR comprised edge sharing of FeO6 octahedral units, which was changed by the oxidation of Fe(II). In addition, it was found that the GR was partially oxidised to alpha-FeOOH by the addition of copper ions. (C) 2008 Elsevier Ltd. All rights reserved.

Stress-induced martensitic transformation in Fe-Mn-Si alloys is characterized by the transformation of the fee matrix to the hcp phase, which is generally reversible. In this study, Debye rings obtained by monochromated X-ray diffraction using synchrotron radiation were used for analyzing the structural change of the fee matrix to the hcp phase in a polycrystalline austenitic Fe-Mn-Si-Cr alloy that was deformed by the tensile test at room temperature. Structural changes resulting from the reverse transformation due to heating were also studied. The results showed that the occurrence of the stress-induced martensitic transformation was not uniform, but depended on the relationship between the orientation of polycrystalline grains and the tensile direction. The transformation appears to preferentially occur in grains with large Schmid factors for the shear of [2 11](111) in the fee matrix, and the formation of hcp phases also depends on the orientation of grains. The reverse transformation due to heating does not necessarily occur in the crystallographically reversible route. This indicates that irreversible deformation induced by dislocations during the tensile test restricts the reversible transformation of the alloy.

A low temperature synthesis method using a modified polyol process is employed to synthesize FePt nanoparticles even at 393 K. The composition could be controlled using the above process by varying the reaction conditions to obtain Fe(50)Pt(50) nanoparticles at 473 K. The magnetic properties of the fcc-FePt nanoparticles indicate that they are not completely superparamagnetic in spite of the smaller particle size.

Structural analysis techniques such as X-ray diffraction and anomalous X-ray scattering were used for characterizing the influence of manganese on iron oxyhydroxides and oxides formed from green rust (GR) in an aqueous solution. The results showed that the formation of Fe3O4 was enhanced by the addition of manganese ions during the conversion of GR2(SO42-) to alpha-FeOOH and Fe3O4. The results obtained from anomalous X-ray scattering showed that manganese was present both in alpha-FeOOH and Fe3O4 particles. The incorporation of manganese in alpha-FeOOH appears to induce the distortion of the atomic-scale structure of alpha-FeOOH particles formed in an aqueous solution. (C) 2007 Elsevier Ltd. All rights reserved.

XPS and SIMS were used for characterizing the surface oxide layers formed on Fe - Al alloys during annealing under atmospheres with different partial pressures of oxygen, which were controlled by H2O/H-2 ratios in the gas. The XPS results showed that an aluminum oxide (Al2O3) layer was formed on the surfaces of samples annealed at a high temperature under a low partial pressure of oxygen, while such a layer was not formed on the surfaces of samples annealed under a high partial pressure of oxygen. SIMS depth profiles showed that the surfaces of samples annealed at high temperatures under a low partial pressure of oxygen were covered with a thin Al2O3 layer of approximately 50 nm thickness. It was also shown that oxygen penetrated the samples annealed under a high partial pressure of oxygen, and the depth profile of oxygen was correlated with that of aluminum. This indicates that internal oxidation of aluminum occurs in the samples annealed under a high partial pressure of oxygen. Grazing-incidence X-ray diffraction (GIXD) was also employed for analyzing the structure of the Al2O3 layer formed on the surface of samples annealed under a low partial pressure of oxygen. Copyright (c) 2008 John Wiley & Sons, Ltd.

Visible light sensitive and highly active Cu-doped ZnS hollow photocatalyst particles "Cu-ZnS-shell" were successfully developed. These particles could generate H-2 through photocatalytic decomposition of HS- ion in Na2S solution. The photoactivity under xenon lamp irradiation was 6 and 130 times higher than that of copper-free "ZnS-shell" and coprecipitated ZnS particles, respectively. "Cu-ZnS-shell" particles were prepared by doping the "ZnS-shell" particles synthesized using zinc oxide as precursor with Cu, utilizing the difference in ionization tendency between zinc and copper. Though the photoactivity of "ZnS-shell" was higher than that of coprecipitated ZnS, their photoactivity under visible light conditions was low. However, the "Cu-ZnS-shell" was active to light of wavelengths higher than 440 nm and is preferred over US, which requires an expensive support metal catalyst such as platinum to decompose HS- ion.

X-ray diffraction, transmission electron microscopy, and X-ray absorption spectroscopy were used for characterizing the role of nickel in the transformation of Green Rrust 2(SO42-) (GR2). GR2(SO42-) was synthesized from the solution of ferric and ferrous sulfate and that of sodium hydroxide. The suspension containing GR2(SO42-) with and without nickel was oxidized by passing oxygen gas into the aqueous solution, in which GR2(SO42-) was transformed into ferric oxyhydroxides. The pH and oxidation reduction potential (ORP) values of the aqueous solution were monitored during the transformation of GR2(SO42-). In addition, the concentrations of iron and nickel in the solution during the transformation of GR2(SO42-) were analyzed by using inductively coupled plasma atomic emission spectroscopy. The reaction conditions of the GR2(SO42-) suspension were found to be strongly influenced by the addition of nickel. The reaction product goethite, which was transformed from GR2(SO42-), also appeared to be stabilized by the addition of nickel. These results indicate that the species of the solid particles formed in the solution are controlled by the addition of foreign elements.

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Analyses of small-angle X-ray scattering (SAXS) and extended X-ray absorption fine structure (EXAFS) were performed for characterizing precipitates formed in a, Cu-Ni-Si alloy without and with a, small amount of Fe, the strength and electrical conductivity of which were improved by aging process. These alloy samples were aged at 720 K after a solution treatment. The SAXS profiles of the samples were measured to investigate the size of precipitates. The results of SAXS measurements showed that nanometer-size precipitates formed in the alloy samples during isothermal aging. The precipitates in the Cu-alloy sample without Fe appeared to be coarsened in a multi-modal size distribution by the aging process. In contrast, the precipitates with homogeneous size were formed for the Cu-alloy sample with Fe. The environmental structure of Ni and Fe of these alloys evaluated by EXAFS measurements revealed that the precipitates of these alloys have the structure of δ-Ni2Si, and Fe substitutes Ni in δ-Ni2Si. It is presumed that the precipitates of homogeneous size in the Fe-added Cu alloy were formed because highly dispersed Fe atoms serve as nucleation sites of Ni2Si. © 2008 The Surface Science Society of Japan.

In order to understand the formation mechanism of Cr(VI) in chromium-containing steel slag, X-ray diffractiometry (XRD), X-ray absorption spectroscopy (XAS) in the region of X-ray absorption near edge structure (XANES), and X-ray photoelectron spectroscopy (XPS) measurements were performed for analyzing the chromium contained in the model slag of CaO–SiO₂ base. The model slag was annealed under different temperatures and atmospheres to change the chemical state of chromium. XRD results showed that a diffraction peak that can be assigned to CaCrO₄ comprising of Cr(VI) was detected in the model–slag sample annealed under a high partial pressure of oxygen (air). XANES results showed that the Cr(VI) concentration in the slag increased by annealing under a high partial pressure of oxygen, while it was very low in the slag sample annealed under a low partial pressure of oxygen. The XANES results were consistent with the XRD results. The formation conditions of Cr(VI) were discussed on the basis of the thermodynamic characteristics of a Ca–Cr–O system. The XPS results for the slag surface were dependent on the leaching tests performed on the slag, while the XANES results were insensitive to the leaching tests. This indicates that Cr(VI) dissolved from only a surface layer of the model slag. The chromium that dissolved from the slag in an aqueous solution by the leaching test was also analyzed and was found to be in the form of Cr(VI); further, its concentration depended on the annealing conditions of the slag.

Antimony is sometimes added to iron based alloys, in order to improve the surface properties of the alloys. Although alloying elements are known to be often enriched to the surfaces of the alloys annealed at high temperatures, the enrichment of these elements at the alloy surfaces can occur due to different mechanisms. In this study, XPS was used for characterizing the enrichment of antimony on the iron surfaces by annealing under a low partial pressure of oxygen. The results showed that antimony was enriched to the iron based alloy surfaces by annealing at high temperatures, and the thicknesses of the antimony enriched layer was less than about 1nm. Although the addition of nickel to the alloy seemed to enhance the enrichment rate of antimony, the amount of antimony enriched on the sample surface was not influenced by the addition of nickel.

Structural changes of polycrystalline Fe-Mn-Si-Cr austenitic alloys by deformation at room temperature were studied by X-ray diffraction measurements using synchrotron radiation. The results showed that stress-induced martensitic transformation occurred by deformation, whereby a part of the face centered cubic structure in the alloy matrix (austenic phase) was transformed to the close packed hexagonal structure (ε-martensite phase). When the shape of the alloy deformed at room temperature was partially recovered by annealing at about 673K, indicating that the reverse transformation of martensite formed stress-induced transformation took place by heating. The crystallographic orientation relationships in the transformation and the reverse transformation were investigated in polycrystalline Fe-Mn-Si-Cr alloys. In addition, the crystallographic orientation changes in Fe-Mn-Si-Al alloys showing twining induced plasticity and transformation induced plasticity were also studied.

In order to characterize the chemical state of chromium and the dissolution characteristics of chromium from a slag used for stainless steel production, X-ray absorption near edge structure spectra were utilized for analyzing the chemical state of chromium in the slag and solution analyses were carried out for determining the dissolved amount of chromium. The results indicate that the amount of Cr(VI) in the slag was increased by annealing in air, and the amount of chromium dissolved from the slag annealed in air into aqueous solution was higher than that from the slag annealed under low partial pressure of oxygen. Since the amount of Cr(VI) in the slag measured by XANES was not changed after dissolution operation, it is considered that Cr(VI) dissolved in the solution originated from Cr(VI) in the surface layer of the slag annealed in air.

This paper proposes a new system for the simultaneous detoxification and thermal recovery of stainless steel refining slag in which hexavalent chromium contained in the slag is reduced to trivalent chromium by a reducing gas. The reducing gas was obtained by recovering the waste heat of molten slag. In the experiment, the properties of the hexavalent chromium leached from stainless-steel refining slag that is treated in oxidizing and reducing atmospheres at various temperatures was investigated. The results showed that the amount of hexavalent chromium leached decreased for treatment at over 1173 K in oxidizing and reducing atmospheres. Furthermore, the heat recovery system for producing the reducing gas was analyzed, in which a heat and material balance model predicted all the operating data of the system based on the actual operation, and then energy analysis based on the predicted data was conducted to validate the system theoretically. The results showed that the proposed system can potentially produce 3.9 billion Nm^3 of hydrogen per year, and it reduces the energy consumption to 65.8% of that of the conventional method.

X-ray absorption near-edge structure (XANES) is useful to analysis of the valence of selected element or the symmetry surrounding it. XAFS measurements by using in-house X-ray absorption spectrometer have high potential to apply to analyze the local structure or the electronic states of materials, it is not so popular recently with increasing the use of synchrotron facilities has become prevailing into various fields. The capacity of the in-house XAFS is shown in this paper along with some examples of experiments by a spectrometer with X-ray generator of only 3kW.

We investigated the influence of silicate ions on the formation of goethite converted from hydroxysulphate green rust, which was synthesized by neutralizing mixted solution of Fe-2(SO4)(3) and FeSO4 with NaOH solution, by O-2 in an aqueous solution. The pH and oxidation-reduction potential of the suspension and the Fe and Si concentrations in supernatant solutions were analyzed. X-ray diffraction results for the solid particles formed during the conversion were consistent with the results of the solution analyses. The results indicated that silicate ions suppressed the conversion from green rust to alpha-FeOOH and distorted the linkages of FeO6 octahedral units in the alpha-FeOOH structure. (C) 2007 Elsevier Ltd. All rights reserved.

Nanocrystalline cobalt ferrite particles of 8 nm grain size were synthesized by coprecipitation technique and subsequently suitably heat treated to obtain higher grain sizes. The experimentally observed changes in the dc electrical conductivity and Curie temperature with heat treatment have been attributed to the changes in the cation distributions as obtained from the Mossbauer and extended x-ray absorption fine structure (EXAFS) measurements and to the grain size. The activation energies for conduction as determined from the Arrhenius plots suggest that the conductivity is due to hopping of both electrons and holes. The observed decrease in conductivity when the grain size is increased from 8 to 92 nm is clearly due to the predominant effect of migration of some of the Fe3+ ions from octahedral to tetrahedral sites, as is evident from in-field Mossbauer and EXAFS measurements. But the higher conductivity of the 102 and 123 nm particles compared to that of the 92 nm particles is attributed to the higher grain size, since the cation distribution is found to be the same for all these three samples. The Neel temperature increases from 709 K for the as-prepared particles (8 nm) to 809 K for the 92 nm particles because of the change in the cation distribution and it remains almost the same for the higher grain sizes as there is no further change in the cation distribution. (c) 2007 American Institute of Physics.

Recently, the authors have demonstrated the successful synthesis of Fe-Co nanoparticles with various compositions by using polyol process. In this paper, the synthesis of Fe-Co nanoparticles with their sizes varying between 200 and 35 nm were reported. This was achieved by tuning experimental parameters such as hydroxyl ion and metal ion concentrations, which control the nucleation and growth processes of the system. (c) 2006 Elsevier B.V. All rights reserved.

Analyses of small-angle X-ray scattering (SAXS) and X-ray absorption fine structure (XAFS) were performed for characterizing precipitates formed in a Cu-3.1 at %Ni-1.4 at%Si alloy. the strength and electrical conductivity of which were improved by aging. SAXS profiles and XAFS spectra of samples aged at 720 K for different periods of time after a solution treatment were measured. SAXS profiles of samples, which were aged after the solution treatment and Subsequently cold rolled, were also measured to investigate the effect of dislocations on precipitation. The results of SAXS measurements showed that nanometer-size precipitates formed in the alloy samples during isothermal aging at 720 K. The precipitates in the samples without cold rolling were coarsened in a single modal size distribution with increasing aging time. In contrast, the precipitates formed in the cold-rolled samples appeared to be coarsened in a multi-modal size distribution with increasing aging time. This aging characteristic of the cold-rolled samples is presumably attributable to their good electrical conductivity. The results of XAFS measurements at the Ni K-edge showed that nickel was Substituted for copper in the face-centered cubic (fee) copper matrix and that the local structure around nickel was changed by isothermal aging. With increasing aging time, extended X-ray absorption line structure (EXAFS) functions at the Ni K-edge of the samples were found to be changed, which implies that nickel atoms were precipitated as nickel-silicon Clusters or intermediate compounds in the fee copper matrix. In addition, X-ray absorption near edge structure (XANES) spectra at the Ni K-edge indicated that the electronic Structure of nickel in the samples was influenced by silicon during aging.

FeCo alloy is a soft magnetic material that possesses the highest saturation magnetization of 2.4 T and crystallizes in bee structure as in the case of alpha-Fe. However, the particles synthesized were highly agglomerated. Thus, in this paper, an attempt was made to control the morphology of the particles using different types and concentrations of surfactants such as oleic acid, oleyl amine, polyvinylpyrrolidone (PVP), etc., during the synthesis of the particles. Though all the surfactant experimented partially prevented the agglomeration, products had larger size distribution except for PVP, which provided nearly monodispersed particles. Furthermore, the FeCo particles synthesized in the presence of PVP were either cubic or nearly spherical depending on the concentration of Fe.

In order to clarify the influence of reaction conditions on the formation of iron oxyhydroxides and oxides obtained from hydroxysulfate green rust (GR), the X-ray diffraction method was used for analyzing the solid particles formed during conversion. GR was synthesized from solutions of ferric sulfate, ferrous sulfate, and sodium hydroxide. The suspension containing GR was oxidized by passing oxygen gas. X-ray absorption spectroscopy and transmission electron microscopy were used for analyzing the chemical state and structure of the solid particles separated from the suspension, respectively. The results revealed that GR was converted primarily to alpha-FeOOH, and gamma-FeOOH and Fe3O4 were found to be partially formed during the conversion depending on the temperature and oxygen flow rate. Furthermore, the addition of manganese was shown to enhance the formation of Fe3O4. These results indicate that the formation of different structures of iron oxyhydroxides and oxides in an aqueous solution is sensitive to the reaction conditions.

Studies on lattice change of a nickel-phosphorus amorphous alloy were carried out using not only high temperature X-ray diffraction but also extended X-ray absorption fine structure (EXAFS) analysis. Their thermal properties were characterized by differential scanning calorimetry (DSC). Since the results suggested that lattice relaxation occurred in the amorphous state by annealing, EXAFS measurements were carefully performed for characterizing the local structure of the amorphous alloys. The EXAFS analysis showed that the local structures around Ni atoms, which may be the Ni-Ni and Ni-P correlation, were changed by annealing. High temperature X-ray diffraction showed that small amount of crystal phase appeared by annealing up to 820 K, while clear diffraction peaks of Ni3P were observed above 1100 K. These micro/nanoscale structural changes did not correspond to that obtained by DSC which showed an exothermic reaction of atomistic reordering at 630 K. We need analysis of the nanostructures by small angle X-ray scattering or a high resolution transmission electron microscope.

Solid particles of ferric oxyhydroxides or iron oxide were recrystallized from ferrous and ferric ions dissolved in aqueous solution. There are different structures of alpha-FeOOH, beta-FeOOH and gamma-FeOOH in the ferric oxyhydroxides, of which the formation is influenced by reaction conditions such as oxidation rate of ferrous ions. In this work, a few factors affecting the formation of the ferric oxyhydroxides and iron oxides, which was converted from hydrosulfate green rust, has been studied using different methods. The hydrosulfate green rust (GR2) was synthesized from solutions of ferric sulfate (Fe-2(SO4)(3)), ferrous sulfate (FeSO4), and sodium hydroxide (NaOH), and they were oxidized by gas containing oxygen. X-ray diffraction measurements and X-ray absorption spectroscopy were used for analyzing the structure and chemical state of solid particles extracted from the suspension during the oxidation. The morphology of the particles was observed by transmission electron microscopy. The results showed that gamma-FeOOH or Fe3O4 particles were formed together with alpha-FeOOH particles during conversion from the green rust, depending on oxidation temperature, oxygen flow rate and addition of manganese. This indicates that the species of ferric oxyhydroxides or iron oxides formed in aqueous solution is sensitively influenced by reaction conditions.

Studies on lattice change of a nickel-phosphorus amorphous alloy were carried out using not only high temperature X-ray diffraction but also extended X-ray absorption fine structure (EXAFS) analysis. Their thermal properties were characterized by differential scanning calorimetry (DSC). Since the results suggested that lattice relaxation occurred in the amorphous state by annealing, EXAFS measurements were carefully performed for characterizing the local structure of the amorphous alloys. The EXAFS analysis showed that the local structures around Ni atoms, which may be the Ni-Ni and Ni-P correlation, were changed by annealing. High temperature X-ray diffraction showed that small amount of crystal phase appeared by annealing up to 820 K, while clear diffraction peaks of Ni3P were observed above 1100 K. These micro/nanoscale structural changes did not correspond to that obtained by DSC which showed an exothermic reaction of atomistic reordering at 630 K. We need analysis of the nanostructures by small angle X-ray scattering or a high resolution transmission electron microscope.

Solid particles of ferric oxyhydroxides or iron oxide were recrystallized from ferrous and ferric ions dissolved in aqueous solution. There are different structures of alpha-FeOOH, beta-FeOOH and gamma-FeOOH in the ferric oxyhydroxides, of which the formation is influenced by reaction conditions such as oxidation rate of ferrous ions. In this work, a few factors affecting the formation of the ferric oxyhydroxides and iron oxides, which was converted from hydrosulfate green rust, has been studied using different methods. The hydrosulfate green rust (GR2) was synthesized from solutions of ferric sulfate (Fe-2(SO4)(3)), ferrous sulfate (FeSO4), and sodium hydroxide (NaOH), and they were oxidized by gas containing oxygen. X-ray diffraction measurements and X-ray absorption spectroscopy were used for analyzing the structure and chemical state of solid particles extracted from the suspension during the oxidation. The morphology of the particles was observed by transmission electron microscopy. The results showed that gamma-FeOOH or Fe3O4 particles were formed together with alpha-FeOOH particles during conversion from the green rust, depending on oxidation temperature, oxygen flow rate and addition of manganese. This indicates that the species of ferric oxyhydroxides or iron oxides formed in aqueous solution is sensitively influenced by reaction conditions.

A modified polyol process for the synthesis of cubic-shaped FeCo particles at 403 K is demonstrated. Control of the particle composition and size was achieved by varying the experimental conditions. The Fe content in the FeCo particles can be varied from 90 to 20 mol %, and the size of the cubes can be controlled to obtain particles with sizes between 300 and 35 nm (see figure). The magnetic properties of the particles closely resemble those of bulk FeCo.

Nanocrystalline Ni0.5Zn0.5Fe2O4 spinel ferrite with a grain size of 50 nm was prepared by using the ceramic method. The grain size was further reduced to 14 nm by milling the as-prepared ferrite particles in a high-energy ball mill. From the impedance spectroscopy studies we have observed that the dc electrical conductivity increases upon milling. Furthermore, the cation distribution data, as obtained from the in-field Mossbauer and extended x-ray absorption fine structure measurements, suggested a decrease in the conductivity for the milled sample. The increase in conductivity of the milled sample is, therefore, attributed to conduction by the oxygen vacancies created by mechanical milling. The higher values obtained for the activation energy for conduction are also evidence for the oxygen vacancy conduction. The increase in Neel temperature from 573 to 611K on reducing the grain size from 50 to 14 nm has been explained based on the changes in the cation distribution. The observed increase in the coercivity of the milled sample has been attributed to surface anisotropy of increasing number of ions on the surface. The Mossbauer spectra show canted spin structure for the milled samples.

The successful synthesis of Fe-Co nanoparticles by using a modified polyol process is reported. The formation of the alloy nanoparticles was confirmed by X-ray diffraction and X-ray extended absorption fine structure analyses. The concentration of iron in these particles could be varied between 40% and 90% by controlling the reaction conditions such as initial Fe/Co ratio, reaction temperature and hydroxyl ion concentration. The shape of the particles changed from spherical to cubic when the concentration of Fe was increased from 40 to above 60 at. %. The highest magnetization of 225 emu/g was recorded for Fe70Co30 nanoparticles. The magnetization of these particles decreased by about 20% when exposed to severe oxidizing atmosphere for seven days.

The polyol process and the parameters influencing the synthesis of metal and alloy nanoparticle are discussed. Then, the synthesis strategies to obtain hard (Fe-Pt) and soft (Fe-Co) nanoparticles by using polyol process is presented. Under optimum synthesis conditions, partially ordered Fe-Pt nanoparticles with an average grain diameter of 8 nm exhibited a coercivity of 460 kA/m in the as-synthesized state. In the case of Fe-Co alloy particles, synthesis technique to prepare particles with varying Fe concentration in the size ranging between 300 and 50 nm is reported.

Size-controlled Mn0.67Zn0.33Fe2O4 nanoparticles in the wide range from 80 to 20 nm have been synthesized, for the first time, using the oxidation method. It has been demonstrated that the particle size can be tailor-made by varying the concentration of the oxidant. The magnetization of the 80 nm particles was 49 A m(2) kg(-1) compared to 34 A m(2)kg(-1) for the 20 nm particles. The Curie temperatures for all wthe samples are found to be within 630 +/- 5 K suggesting that there is no size-dependent cation distribution. The critical particle size for the superparamagnetic limit is found to be about 25 nm. The effective magnetic anisotropy constant is experimentally determined to be 7.78 kJ m(-3) for the 25 nm particles, which is about an order of magnitude higher than that of the bulk ferrite. (c) 2006 Elsevier Ltd. All rights reserved.

Small-angle X-ray scattering (SAXS) measurements using synchrotron radiation and transmission electron microscopy (TEM) observation have been carried out for characterizing fine particles of ferric oxides including hydroxides and oxyhydroxides. A compact chamber was designed for SAXS measurements at BL15XU of SPring-8, Japan. SAXS profiles of reference particles of ferric oxyhydroxides, namely, α-FeOOH (goethite), β-FeOOH (akaganetite), and γ-FeOOH (lepidocrocite), obtained using the measurement system were compared with their morphologies observed by TEM. SAXS profiles of fine particles of ferric oxides, that were converted from condensed Fe(OH)₃ gel to β-FeOOH and α-Fe₂O₃ by aging, were also measured. While TEM observation provided information on the characteristic microstructure of well-crystallized fine particles of ferric oxides in a selected area of a sample, information regarding fine particles including poorly crystallized ferric oxides in the entire sample was obtained by SAXS measurements. The SAXS and TEM results indicated that the addition of foreign anions of sulfate or silicate to the gel delayed the conversion processes of the gel to β-FeOOH and α-Fe₂O₃. A combination of SAXS measurement with TEM observation and X-ray diffraction measurement is shown to be effective in the characterization of fine particles of different iron oxides, which are formed by aging in aqueous media. [DOI: 10.1380/ejssnt.2006.352]

Splitting of hydrogen sulfide using sunlight is a useful reaction to produce hydrogen. Alkaline sulfide solution, which is prepared by dissolving hydrogen sulfide into alkaline water, is selected as the reaction medium of photocatalytic hydrogen generation reaction. In this system, the photocatalytic reaction is assumed to occur as follows: 2H(2)O + 2e(-) -&gt; H-2 + 2OH (1) 2S(2-) + 2h(+) -&gt; 2S(2)(2-) (2) However, as the reaction progresses white solids precipitate in the reaction medium. Furthermore, the HPLC analysis suggested that the ratio between the consumption of sulfide ion and the amount of hydrogen generation was about 3:2, which is not stoichiometric. Thus, in this paper, we characterized the white solid precipitate and tried to optimize the solution condition to prevent the precipitation of the same. From our study, the white solid precipitate was confirmed as sulfur derived from the oxidation of the disulfide ion. It was confirmed that the addition of sulfite ions prevented the oxidation of disulfide ions, which causes the precipitation. In the absence of sulfite ions and for sufide ion concentration less than 0.1 K the precipitation of sulfur occurs in a very short reaction time. On the other hand the hydrogen evolution rate retarded when the sulfide ion concentration is higher than 0.1M. This was due to the degradation of the stratified CdS particles. Thus, the optimal concentration of Na2S solution was determined to be around 0.1M.

The synthesis of Cu doped ZnS particles by ion-exchange method and the influence on workable wavelength of light is reported. The workable wavelength of Cu doped ZnS was extended from the same of ZnS (310 rim). The photocatalytic activity of Cu doped ZnS was measured by hydrogen generation experiment using solar simulator and the highest apparent quantum yield was about 11% given from 1% Cu doped ZnS.

Cadmium Sulfide semiconductor has comparatively small band gap and act as photocatalyst under irradiation of visible light. For practical use, it is convenient to fix the photocatalyst on a substrate as a thin film. In this study, we prepared CdS thin film on Ti substrate by Chemical Bath Deposition (CBD). To improve photocatalytic activity, CdS film was annealed and optimum thickness was investigated.

ZnS shows high photocatalytic activity, nevertheless the operating wavelength is limited to less than 330 nm. On the other hand, CdS can be used at wavelength up to 512 nm. However, CdS requires Pt as supporting catalyst. We have synthesized Pt-free ZnxCd1-xS particles with x varying between 0 and 1 by co-precipitation method and evaluated their photocatalytic activities. The highest photocatalytic activity was recorded for Zn0.67Cd0.33S particles. Then. ZnxCd1-xS solid solution films were prepared using the above particles by dip-coating method and their photocatalytic activities were evaluated.

In this study, we focused our attention on photocatalytic decomposition of hydrogen sulfide as the resource of hydrogen using solar energy and prepared ZnxCd1-xS solid solution as photocatalyst. Samples were prepared by "stratified" method using Zn and Cd hydroxides as precursors and "coprecipitation" method under various Zn/Cd ratios to study the influence of Cd concentration on the properties such as crystal structure, light absorption and reactivity. The continuous change in the crystal lattice constant and UV-VIS reflection spectra from ZnS to US was observed in the ZnxCd1-xS samples prepared by both "coprecipitation" and "stratified" methods with increasing concentration of Cd. In the case of coprecipitation method, the reactivity was improved with the increase of Cd. But in the case of stratified method, the particles prepared at Zn: Cd=2:1 showed higher reactivity than the samples prepared at higher ratios of Cd and the samples prepared by coprecipitation method with similar Zn/Cd ratios. The samples prepared by stratified method at higher ratio of Zn/Cd turned black from yellow in color when exposed to light irradiation. This was believed due to the metal deposited by photocatalytic reduction of precursors. This metal deposition influences the photoreactivity of ZnxCd1-xS particles and is optimum for Zn(0.6)7Cd(0.33)S.

The Neel temperature of Ni0.5Zn0.5Fe2O4 spinel ferrite increases significantly from 538 K in the bulk state to 592 K when the grain size is reduced to 16 nm by milling in a high-energy ball mill. This has been attributed to an increase in the AB superexchange interaction strength due to a possible enhancement in the magnetic ion concentration in the A-site on milling, as is evident from extended x-ray absorption fine structure and in-field Mossbauer measurements. (c) 2005 American Institute of Physics.

The Ni nanoparticles with fcc or hcp phases have been synthesized in tetraethylene glycol by using the modified polyol process. The crystal structure has been controlled by changing the polyol/Ni mole ratio and the reaction temperature. The saturation magnetization of the as-prepared particles depends on the relative volume fraction of the hcp phase. The x-ray diffraction and extended x-ray absorption fine structure studies suggest the formation of pure fcc and hcp Ni phases. The hcp Ni particles show nonmagnetic behavior and thermally stable below 673 K. (c) 2005 American Institute of Physics.

In-house XAFS spectrometers suitable for routine experiments are getting fairly popular today. One of the problems of such apparatus is the capability to study low atomic number materials. In general, elements with atomic number 20 (i.e. Ca) and below is difficult to measure because absorption of air becomes large. In this energy region, very important elements for environmental studies, such as S and P are involved. Either an evacuated or a He-filled X-ray path is required for getting enough photons in the low energy region. Since most in-house XAFS spectrometers apply Rowland Circle configuration, the spectrometer shows fairly complicated movement during energy scan. Varying the distance between the X-ray source and the bent crystal requires bellows for evacuating the X-ray path or substituting by He, but it restricts the spectrometer scanning range, especially on the low angle side. However, the low angle range (i.e. 30 to 60 degree) is most commonly used and X-rays are efficiently collected in this range. We have customized a commercial XAFS spectrometer to be capable for energies as low as 2 keV for sulfur measurement without sacrificing its scanning range.

The extended X-ray absorption fine structure (EXAFS) method and transmission electron microscopy (TEM) have been used for characterizing the local structure and morphology of ferric oxyhydroxides, alpha-FeOOH and gamma-FeOOH, with and without chromium. These ferric oxyhydroxide powders were prepared from aqueous solutions containing iron and chromium ions. Radial structural functions for iron obtained by Fe K edge EXAFS spectra showed that the linkage of structural units formed by FeO6 octahedra in gamma-FeOOH is distorted by chromium addition, while such distortion in alpha-FeOOH is not clearly detected. On the other hand, Cr K edge EXAFS spectra showed that the local structure around chromium does not necessarily correspond to the local structure around of iron, which is observed by Fe K edge EXAFS spectra. This suggests that the structural units containing iron and chromium are heterogeneously distributed in these ferric oxyhydroxides. The local structural information was discussed coupled with morphological features of these ferric oxyhydroxides observed by TEM. (C) 2003 Elsevier Ltd. All rights reserved.

Synthesis strategies for the size and structure controlled Ni, Co, and FePt nanoparticles by manipulating the reaction kinetics of the polyol process are reported. In the case of Ni, particle size varied from a few micron to a few tens of nanometer, and the structure from fcc to a mixture of fcc and hcp was realized. The Co particle structure has been changed from a mixture of fcc and hcp at micron size range, to the fcc dominant mixture of fcc and hcp in the submicron size range, then to epsilon- and hcp-Co and finally to hcp-Co in the nanosize range. In the case of FePt, particles had fcc and fct phases with 5-10 nm in diameter. The magnetic properties of these particles are also reported. (C) 2004 American Institute of Physics.

Nanoparticles under a few nanometres in size have structures and material functions that differ from the bulk because of their distinct geometrical shapes and strong quantum confinement. These qualities could lead to unique device applications. Our mass spectral analysis of CdSe nanoparticles reveals that (CdSe)(33) and (CdSe)(34) are extremely stable: with a simple solution method, they grow in preference to any other chemical compositions to produce macroscopic quantities. First-principles calculations predict that these are puckered (CdSe)(28)-cages, with four- and six-membered rings based on the highly symmetric octahedral analogues of fullerenes, accommodating either (CdSe)(5) or (CdSe)(6) inside to form a three-dimensional network with essentially heteropolar sp(3)-bonding. This is in accordance with our X-ray and optical analyses. We have found similar mass spectra and atomic structures in CdS, CdTe, ZnS and ZnSe, demonstrating that mass-specified and macroscopically produced nanoparticles, which have been practically limited so far to elemental carbon(1), can now be extended to a vast variety of compound systems.

Nearly monodispersed CoFe2O4 nanoparticles with average sizes between 8 and 100 nm were synthesized by using seed-mediated growth dominant coprecipitation and modified oxidation methods. X-ray diffraction and Mossbauer spectroscopy analyses confirmed the spinel phase and a stoichiometric composition of (Co0.25Fe0.75)[Co0.75Fe1.25]O-4 for powders with different particle diameters. Rotational hysteresis loss (W-r) analysis showed an average switching field (H-p) of 17 kOe and a magnetic anisotropy field (H-k) of 38 kOe for the 40 nm CoFe2O4 particles. The corresponding magnetocrystalline anisotropy energy constant (K) was about 5.1x10(6) erg/cc. The H-c and H-p results suggest that the critical single-domain size of CoFe2O4 is about 40 nm. The room temperature coercivity (H-c) of the 40 nm CoFe2O4 particles is found to be as high as 4.65 kOe. (C) 2003 American Institute of Physics.

A two-compartment photoelectrochemical cell consisting of a CdS photoanode immersed in aqueous sulfide solution, Nafion membrane, platinum cathode and sulfuric acid solution as the dark-compartment electrolyte was constructed. The effects of the concentrations of the electrolytes, membrane surface and cathode materials on the performance of the cell were studied to reach high quantum yield of hydrogen production. Under optimized conditions, light to hydrogen conversion efficiency up to 12% was observed under sun light illumination. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.

Cobalt ferrite particles with diameters ranging from a few micrometer to about 15 run were synthesized using a modified oxidation process. The fine control of the particle size was achieved by introducing various concentrations of Fe3+ ions at the beginning of the reaction. Among the particle sizes obtained by using this method, particles with a grain size of about 36 nm showed a magnetization (M-S) of 64 emu/g and a maximum coercivity (H-C) of 2020 Oe at room temperature. The corresponding squareness ratio was found to be 0.53. (C) 2003 Elsevier Science (USA). All rights reserved.

The possibility for direct synthesis of fct-FePt nanoparticles of the order of 3-4 nm in diameter through the coreduction of iron and platinum ions in a polyol has been explored. We have succeeded in the synthesis of face-centered cubic structured 3-4 nm diameter FePt particles whose composition was very close to Fe50Pt50. The Fe:Pt ratio was influenced little by the molar ratios of Fe and Pt acetylacetonate dissolved in ethylene glycol. However, depending on the polyol/Pt ratio, the as-prepared samples were either superparamagnetic or ferromagnetic. The transition temperature (T-t) and magnetic properties of the as-prepared FePt were very sensitive to the reaction conditions, and the T-t varied between 593 and 893 K and the particles were ferromagnetic. The as-prepared FePt under the optimum condition had a T-t as low as 593 K and H-c as high as 1.11 kOe at an applied field of 1 T at room temperature. Furthermore, when the as-prepared FePt nanoparticles with T-t around 593 K were annealed at 673 K in H-2/N-2 atmosphere for an hour they transformed to the ordered fct (L1(0)) structure with coercivity as high as 4.2 kOe at 300 K. This confirmed the lowering of T-t by the manipulation of the reaction condition alone. (C) 2003 American Institute of Physics.

We report the synthesis and magnetic properties of CoPt nanoparticles by using the polyol process. Since the reduction potential of Pt is more positive than Co, Pt is easily reduced compared to Co. Hence, CoPt nanoparticles were realized by coreducing cobalt and platinum acetylacetonate in the presence of an appropriate amount of OH ions in trimethylene glycol. X-ray diffraction and transmission electron microscopy studies showed that the as-synthesized CoPt nanoparticles had fcc structure and about 5 nm in diameter. Composition analysis reveals that the as-synthesized particles are almost equiatomic Co50Pt50. Magnetic characterization revealed that these nanoparticles are ferromagnetic at room temperature, and that the magnetization and coercivity values were 8 emu/g and 380 Oe, respectively. Differential scanning calorimetry studies showed that the ordering temperature of the as-synthesized particles was only 550degreesC (peak temperature), against 825degreesC of the bulk. Annealing the CoPt nanoparticles above 550degreesC induced ordering with enhanced magnetic properties. (C) 2003 American Institute of Physics.

A growth-assisted coprecipitation process is proposed to achieve highly magnetic Mn-Zn ferrite particles. In this method, first, the particles were synthesized by coprecipitation under optimum condition. Then, further enhancement in particle size was obtained by using the already prepared particles as seed. The average crystallite size of the particles prepared by the proposed method was 12 nm. Furthermore, the magnetization at 1 T applied field was 50 emu/g compared to 37 emu/g of coprecipitated particles. It should be noted that the Curie temperature of the particles remained similar to the coprecipitated particles suggesting that the composition of the Mn-Zn ferrite particles has not been affected by the modified synthesis technique. The gradient of the magnetization-temperature curve was enhanced as a consequence of the rise in magnetization. These particles could be used for the synthesis of temperature sensitive magnetic fluid with higher magnetization and magnetization-temperature gradient. (C) 2003 American Institute of Physics.

Direct synthesis of fct-FePt nanoparticles was achieved by reducing platinum and iron acetylacetonates in tetraethylene glycol (TEG) at 300degreesC. The particle diameter was between 5 and 10 nm. The X-ray diffraction profile of the as-prepared FePt particles exhibited the superlattice reflections (001) and (110), which signified the tetragonality. The H-k of 31 kOe measured at room temperature (RT) from hysteresis loss analysis confirmed the presence of FePt particles with fractionally ordered fct structure which posses substantially high anisotropy. However, the RT coercivity was only 370 Oe due to strong magnetostatic interaction of the particles.

In this paper, we report the results on particle structure in water-based magnetic fluid (MF) using scanning probe microscope (SPM), dynamic light scattering (DLS) and small angle X-ray scattering (SAXS). The SPM analysis showed the presence of ring structures. Furthermore, the DLS measurements indicated the presence of particles as large as few hundred nanometers. The SAXS measurements suggested that the clusters are formed in water-based MF although the primary unit is similar to oil-based MF. The size and proportion of the clusters depended on the dispersion mechanism. (C) 2002 Elsevier Science B.V. All rights reserved.

We have succeeded in the synthesis of nanometer size monodispersed Ni-Co metal particles through the modified-polyol process. Ni-Co metal particles of about 40 and 100 nm with Co-rich core and Ni-rich shell were produced by the manipulation of the reaction kinetics through a suitable selection of hydroxyl ion concentration in the ethylene glycol-Ni-Co system. Furthermore, core-shell structured (NiCo)O(AFM)-NiCo(FM) was produced by oxidizing particles at 533 K in air for different times. The magnetic properties, especially the exchange-bias (HE) fields of 40 and 100-nm core-shell structured particles synthesized under similar conditions behaved differently. However, their behavior was explained considering exchange biased interactions at (NiCo)O(AFM)-NiCo(FM), and (Co)O(AFM)-Co(FM) interfaces with two different exchange coupling constants. The 40 nm particles oxidized for 4 h and composed of (NiCo)0(AFM)-NiCo(FM), exhibited a maximum H-E field of 36 and 201 Oe at 298 and 77 K, respectively.

Applications of CoFe(2)O(4) are limited due to the lack of synthesis technique to produce monodispersed, single domain and high coereivity (H(c)) nanoparticles. Here, we describe the growth dominant co-precipitation process to achieve high H(c) with moderate magnetization at room temperature (RT) in CoFe(2)O(4) nanoparticles. It is well known that the particle size is closely related to the relative interdependence between the nucleation and growth steps, which in turn can strongly be affected by the solution chemistry and precipitation conditions. Based on this premise, the effect of 1) reaction temperature, 2) NaOH concentration, and 3) feeding rate of metal ions into the alkali solution were evaluated. The maximum H(c) of 2.29 kOe (RT) was observed for the CoFe(2)O(4) prepared at 98 degreesC, 1.13-moI NaOH, and the metal ion feeding rate of 0.00103 M/min. To improve the coercivity, single domain CoFe(2)O(4) nanoparticles were produced by in situ growth of the CoFe(2)O(4) seeds followed by size separation method. A coercivity of 4-3 kOe was achieved at RT for 40-nm single domain CoFe(2)O(4) nanoparticles, which is close to the theoretical value of 5.3 kOe.

We have succeeded in synthesizing ZnS films on substrates such as glass or Si wafer by using CBD (chemical bath deposition) method. These semiconductor films were photocatalytic and showed high productivity of hydrogen gas from the solution containing HS- ions. From observation of SEM/TEM, it was found that the cluster film consisted of 100 nm sized agglomerated particles composed of nano-crystals. The result of EDS analysis for the cross-section of the film prepared by using FIB showed the presence of small amounts of oxygen along with zinc and sulfur. The information of the local quantum structures obtained from EXAFS/XANES analysis suggested that the cluster film has unique atomic-distribution and metastable electronic state different from bulk ZnS and ZnO. Based on the results of the above analysis, the relation between local quantum structures and properties was proposed.

The dimeric C-70 oxides were synthesized from C-70/C70O mixed powder by hydrothermal treatment at 373 K for 12 h in aqueous NaOH solution. In this treatment, nucleophilic OH- ions are abundant and nucleophilic addition reactions were considered to synthesize dimeric fullerene oxides. The yield was estimated as ca. 2-3% summing up each isomer and also produced polyoxides, it is lower than that Of C120O. Three isomers Of C140O were isolated using High Performance Liquid Chromatography (HPLC) and characterized with UV- vis, FT-IR, and C-13 NMR and other methods. The results of these methods show a close similarity between C140O and C120O and support that our C140O samples exhibit the structure of conventional furan-bridged dimers. On the basis of the results of C-13 NMR and PM3 calculations, structure assignments for each sample were attempted.

Nanometer-scale semiconductor and oxide particles are synthesized by solution methods, i.e. emulsion and reverse micelle techniques. Particle sizes are not only controlled by synthesis conditions, but also selected by flotation and filtration. The physical and chemical properties of these particles are analyzed in finding materials functions appeared in nanometer sizes. In particular, II-VI semiconductor particles show high photo-chemical activities, such as photo-catalytic processes. They also show several size and shape dependent stabilities in diameters &lt; 2 nm. C) 2002 Elsevier Science B.V. All rights reserved.

Preparing high coercivity CoFe2O4 nanoparticles suitable for high-density recording is still a challenge. The theoretical values for a random system of spherical, non-interacting single-domain CoFe2O4 particles with cubic anisotropy have been predicted to be: Ms (300 K)=80.8 emu/gm, Hc(300 K)=5.3 kOe and Mr/Ms=0.83. Here, for the first time, we report the synthesis of CoFe2O4 nanoparticles of about 40 nm with unusual high coercivity of 4.3 kOe at room temperature (RT).

Nanostructured CdFe2O4 spinel powders with various grain sizes ranging from 60 to 4 nm were synthesized by ball milling the bulk material. The magnetization measurements at 1 and 9 T reveal a spin-glass-like surface structure and the material is found to have a large anisotropy. Mossbauer studies at 10 K in external magnetic fields of 6 and 8.5 T applied parallel to the direction of gamma rays could clearly show that CdFe2O4 behaves like a mixed spinel on reducing the grain size to nanometer level and exhibits ferrimagnetic ordering. Fe3+ spins at both A and B sites exhibit spin canting. (C) 2001 American Institute of Physics.

Nanocrystalline NiFe2O4 spinel has been synthesized with various grain sizes by high-energy ball milling. From the high-field magnetization studies and extended x-ray-absorption fine-structure, and Mossbauer measurements in an external magnetic field of 5 T applied parallel to the direction of gamma rays, we could observe that Ni2+ ions occupy tetrahedral sites on grain-size reduction due to milling. The Fe3+ spins have a canted structure and the canting angle increases with grain-size reduction. It is possible that the core Fe3+ spins are also canted because of the magnetocrystalline anisotropy introduced by the occupancy of the Ni2+ ions in the tetrahedral sites.

In this report, a novel and efficient purification technique for multi-walled carbon nanotubes (MWNTs) combining wet grinding, hydrothermal treatment, and oxidation processes has been described. Graphite pieces of over few tens of mum were removed by wet grinding in water followed by sieving. The separation of graphite pieces of the order of a few mum and MWNTs was achieved through hydrothermal treatment followed by centrifuging. Finally, the carbon nanoparticles were removed by burning the semi-purified sample in an oxidizing atmosphere at 973 K. Scanning electron microscope, transmission electron microscope, and Raman spectroscopy were used to monitor the purification efficiency at each processing step. Using this purification method, 16 mg of the purified MWNTs were obtained from 850 mg of the inner core material from the negative electrode.

In a conventional in-laboratory XAFS apparatus using conventional X-ray source, sealed tube or rotating anode, has been used. In which the X-ray source is fixed and the sample is moved (translated and rotated). Hence it has been difficult or required a complex method in order to put a heavy element, such as a cryogenic cooler, high temperature furnace and an in-situ reacting cell, at a sample position. Nowadays, there is a strong demand for obtaining dynamic information of a sample and insitu observation becomes almost unavoidable. We have developed a compact X-ray tube and a new goniometer on which X-ray source is moved and monochromatic X-ray comes out of goniometer is fixed. Therefore it becomes easier to put a various cell at a sample position.

In our earlier report, we have already proposed a novel purification method to obtain highly purified SWNTs. Considering the use of SWNTs for the industrial applications, automation of the proposed purification method is required to supply large quantifies of purified SWNTs. In this study, we designed the device to automate the purification process.

Semiconductor and oxide clusters were prepared in solution by chemical reactions, photo-etching and liquid chromatography. Electrodeposition technique is also applied to produce cluster-assembled films. Physical and chemical properties of these clusters were analyzed with respect to specific materials functions in nanometer scale. Clusters of II-VI semiconductor stabilize at several discrete sizes and shapes in the diameter range of 1 to 3 nm. Electro-deposited clusters of II-VI semiconductor assembled in a thin film show high activities in photoelectrolysis of H2S.

Nanometer size CdSe clusters are produced in toluene solution stabilized by decylamine using two phase protocol reaction. We have demonstrated possibility to remove selectively some parts of nanoparticles size distribution by selective photochemical etching. Method can be used to adjust particle size and size distribution. CdSe clusters of the size below 1 ran with narrow size distribution and perfect structure have been obtained. Photoetching increases quantum yield of photoluminescence by increasing the lifetime of charge carriers in nanoparticles.

The EXAFS method has been used for investigating the local structures of ferric oxyhydroxides which are reaction products formed on an iron surface exposed to air or immersed in salt water. Fe K EXAFS spectra of two references of ferric oxyhydroxides, i.e. goethite and lepidocrocite, which are often detected as components of reaction products, have been also studied for comparison thereof. The two reference oxyhydroxides demonstrated different EXAFS spectra, which are interpreted based on the atomic local structures. Fe K EXAFS spectra and their radial distribution functions of the reaction products formed on an iron surface have been compared with those of the reference oxyhydroxides. This comparison shows that the first and second nearest neighboring structures around ferric ions in the reaction products are different from those of the two references. These results indicate that the local structures around ferric ions in the reaction products are disordered, although the atomic local structures of Fe-O may be described as being local structural units. (C) 2001 Elsevier Science B.V. All rights reserved.

We have succeeded in synthesizing ZnS cluster film on substrates such as glass by chemical bath deposition (CBD) method. These semiconductor films were photocatalytic for wavelength less than 350 nm and showed high productivity of hydrogen gas from the solution containing HS- ions. On the other hand, when carbon nanotubes were used as the substrate for ZnS deposition, it showed even higher photocatalytic activity resulting in increased hydrogen evolution. Morphology, local atomic structure and electronic state of the films were analyzed by SEM/TEM, EXAFS and XANES, respectively. Based on the above data, the relation between local structure and photocatalytic activity was proposed.

We report the synthesis of highly photocatalytic stratified ZnS particles having the form of a capsule with a layer constituted of ZnS particles of 5-10 nm from 200nm of ZnO particles Particles were dispersed in Na2S solution and irradiated with mercury lamp Light of wavelength up to 350nm was absorbed and large amount of hydrogen was generated. Hydrogen evolution reaction was considered as follows Two protons in the Na2S solution received two electrons from the stratified ZnS particle and formed hydrogen On the other hand, 2HS(-) ions in the solution dissociated into 2H(+) and S-2(2-) and gave away two electrons to stratified ZnS particle.

In this paper, a purification method for single-walled nanotubes (SWNTs) using H2O2 solution as the oxidizing agent for amorphous carbon is proposed. By controlling the concentration of H2O2, amorphous carbon in the soot was selectively oxidized while the SWNTs remained intact. However, the key to the automation of the SWNTs purification depended very much on the automation of the decantation process, which was used for the separation of the SWNTs from large graphite particles and carbon nanoparticles Thus, a device to automate the decantation process has been proposed The performance and the prospects of automation of the entire process is discussed.

Nanocrystalline NiFe2O4 was synthesized by coprecipitation and ball milling techniques with different grain sizes and the samples were analyzed by in-house extended X-ray absorption fine structure (EXAFS) and in-field Mossabuer techniques. While the coprecipitated NiFe2O4 showed the inverse spinel structure even at 9 nm, the structural parameters of the ball milled sample of similar average grain size showed different structure. The in-field Mossbauer spectroscopy studies of ball milled samples showed that the Ni2+ ions occupy A sites and hence the structure changed from inverse to mixed spinel type.

We report a new and simple method to synthesize water-soluble fullerenes. Here, the fullerene oxides are simply boiled in alkali aqueous solution to obtain water-soluble species. The mass spectrometer of water-soluble sample confirmed the presence of C-60 suggesting the dissolution of the same in water. However, the fourier transform infrared (FT-IR) and ultraviolet-visible (UV-VIS) analysis suggested that the solution contains numerous species and their properties were different to that of C-60. To study the properties of water-soluble species in detail, the isolation using high performance liquid chromatography (HPLC) was attempted. The HPLC analysis of the products suggested the presence of several species of water-soluble fullerene derivatives and in most of the peaks, the presence of C-60 was confirmed. The results of the UV-VIS analysis confirmed the separation of soluble species by HPLC.

A simple method to synthesize fullerene/sulfur compounds has been developed. C60S16 crystal of glossy black color is grown in organic solution. From the analysis of C60S16 single crystal, cell constants and an orientation matrix of C60S16 corresponded to a C-centered monoclinic cell with dimensions: a=20.874(1)Angstrom, b=21.139(1)Angstrom, c=10.5690(6)Angstrom, beta=111.93(1)degrees, and the space group, C2/c (No 15).

We have succeeded in synthesizing ZuS film on substrates such as glass by chemical bath deposition (CBD) method. These semiconductor films were photocatalytic for wavelength less than 340 nm and showed high productivity of hydrogen gas from the solution containing HS- ions. On the other band, when carbon nanotubes were used as the substrate for ZnS deposition, it showed even higher photocatalytic activity resulting in increased hydrogen evolution. Morphology, local atomic structure and electronic state of the films were analyzed by SEM/TEM, EXAFS and XANES, respectively. Based on the above data, the relation between local quantum structure and photocatalytic activity is proposed.

A new approach for the synthesis of thin semiconducting n-ZnS film is described. This is based on cathodic electroreduction of sodium polysulfide in the presence of tetrahydroxyl zinc complex. Unlike classical ZnS deposition from acidic mixture of zinc sulfide and sodium thiosulfate, proposed method give metallic Zn-free film of excellent adhesion to the substrate. In this paper tentative mechanism of the deposition is discussed in detail. Prepared samples where characterized by photoelectrochemical techniques and scanning electron microscopy.

Electrochemical deposition method was used for preparation CdS thin films. Photocurrent of investigated films was described in the frame of the Schottky-Mott electrolyte/semiconductor junction model which takes into account two main mechanisms of electron-hole recombination losses (surface and bulk recombination) and rate of the surface electrochemical reaction. Optimal film thickness have been found. in the Pb ions containing solution on the photocurrent have been investigated.

In this report, we presented a novel and simple extraction method, namely Hydrothermally Initiated Dynamic Extraction (HIDE) method, which allows the extraction of exotic fullerenes remaining in the fullerene soot. In the HIDE method, the soot was treated in boiling water that neither dissolved fullerenes nor produced minimal by-products but untangles the fullerenes from the soot, prior to the extraction by organic solvent. As a result, the HIDE method allowed the extraction of exotic fullerenes, such as dimeric fullerene oxides, higher fullerenes having a low symmetry and oxidized higher fullerenes. Accordingly, the single walled nanotubes (SWNTs) with a purity of 99% by wt. was achieved for the first time with the application of the HIDE method.

Structures of poly-molybdate ions in acid Ni-Mo aqueous solutions have been investigated by the anomalous x-ray scattering (AXS), EXAFS and small angle x-ray scattering (SAXS) methods. In a solution containing only molybdenum ions, molybdenum ions form a poly-molybdate ion consisting of seven edge-sharing MoO6 octahedra. In a solution containing both Mo and Ni ions, there exists another poly-molybdate ion consisting of 6 edge-sharing MoO6 surrounding a Ni ion. The coordination number of Mo-Mo pairs decreases by half by adding citric ions. This indicates that the large poly-molybdate ion is decomposed to smaller molybdate ions due to formation of citric complexes. This is also confirmed by the SAXS measurement. Since molybdenum-nickel alloys are not electrodeposited from the solutions without citric ions, we expect that the decomposition of large poly-molybdate ions in the solution is closely related with the mechanism of the induced codeposition of molybdenum and nickel alloy.

In order to understand codeposition in Mo-Ni alloy electroplating, we studied the environmental atomic scale structure around metallic cations in aqueous solutions for electroplating using anomalous X-ray scattering (AXS) and EXAFS. The size of complex ions in aqueous solutions was also estimated by applying small-angle X-ray scattering (SAXS), and the distribution of chemical species in solutions was obtained from multivariate analysis of visible absorption spectra. The results of AXS, EXAFS and SAXS indicate that a solution containing molybdate involves a isopoly-molybdate anion consisting of seven edge-shared MoO₆ octahedra and a solution added nickel sulfate quite likely involves a heteropoly-molybdate anion formed by six edge-shared MoO₆ octahedra surrounding a nickel. On the other hand, linkages of octahedra in the heteropoly anion are broken when citrate is added to the Mo-Ni solution. From the multivariate analysis of visible absorption spectra, we found that addod citric ions form new complexes with Mo as well as Ni in aqueous solutions. Thus, disconnection of relatively large complex appears to be essential for the codeposition process as Mo-Ni alloy, and citric ions also play an important role in this electroplating.

The atomic scale structure of solutions has been recognized as one of the most important research subjects in both aqueous solution chemistry and hydrometallurgy. For this purpose, knowledge of the environmental structure around a certain metallic cation in solution is strongly required The anomalous x-ray scattering (AXS) method, particularly, the energy derivative AXS method, enables us to reduce difficulties due to corrections for scattering from a solution cell as well as for large contribution from water molecules. An attempt is made in this paper to review current studies of hydration structures in concentrated chloride solutions, local structures of ferric hydroxide gel and atomic structures of poly-molybdate ions in acid Mo-Ni aqueous solutions.

The atomic structure of poly-molybdate ions formed in acid Ni-Mo aqueous solutions has been determined by applying anomalous X-ray scattering (AXS) and EXAFS methods. In a solution containing only molybdenum ions, we found only a poly-molybdate ion consisting of seven edgesharing MoO₆ octahedra. In a solution containing both Mo and Ni ions, there exists another polymolybdate ion consisting of 6 edge-sharing MoO₆ surrounding an Ni ion. The total coordination number of Mo and Ni ions around a molybdenum ion is reduced by half when introducing citric ions into the Ni and Mo solution. This indicates that the large poly-molybdate ion is decomposed to smaller molybdate ions when forming citric complexes. Since molybdenum-nickel alloys can not be electrodeposited from solutions without citric ions, we propose a view that the structural change of the poly-molybdate ions in the solutions is closely related with the mechanism of induced codeposition of molybdenum and nickel alloy. The results of small-angle X-ray scattering (SAXS) measurements also support this conclusion.

High-quality as-fused silica glass, heat treated at 1523 K and prepared by the flame-fusion process using natural crystalline quartz and high-purity amorphous silica glass powders, was investigated by small-angle X-ray scattering (SAXS). The X-ray scattering intensity amplitude from the amorphous structure after heat treatment was analysed in terms of viscosity, density and metallic impurity content. It is shown that SAXS scattering of the amorphous sample is sensitive to the structural change induced by annealing.

An in-house anomalous X-ray scatterig (AXS) method has been done for determiningcation distribution in ZnFe<SUB>2</SUB>O<SUB>4</SUB>, NiFe<SUB>2</SUB>O<SUB>4</SUB> and NiAl<SUB>2</SUB>O<SUB>4</SUB> spinels using the anomalous dispersion effect near the K absorption edges of Zn and Ni. When introduced the ratio (<SUB>x</SUB>) of the number of divalent cations of M element, M<SUB>A</SUB>, residing in the tetrahedral A-site to the total number of M element, <I>x</I>=M<SUB>A</SUB>/M<SUB>total</SUB>, the measured intensity ratios of three reflection peaks with two energies close to the <I>K</I> edge of Zn or Ni can be quantitatively explained only by assigning the case where ZnFe<SUB>2</SUB>O<SUB>4</SUB> is the normal type (<I>x</I>=1.0) and NiFe<SUB>2</SUB>O<SUB>4</SUB> is the inverse type (<SUB>x</SUB>=0.0) spinel structure. On the other hand, the results for NiAl<SUB>2</SUB>O<SUB>4</SUB> suggests that 15% of Ni<SUP>2+</SUP> cations occupy the tetrahedral A-site (<I>x</I>=0.15) and the rest are octahedrally coordinated. The usefulness of the in-house AXS method is rather surprisingly well-recognized, particularly for obtaining the cation distribution in crystalline materials containing two elements of nearly the same atomic number.

<title>Abstract</title> The distribution of Zn²⁺ and Co²⁺ cations in ferrite spinels has been determined by applying anomalous X-ray scattering (AXS) near the K absorption edges of Fe, Co and Zn. The energy dependence of the reflection intensities of ZnFe₂O₄, detected at the Fe K and Zn K absorption edges, can only be explained when all Zn²⁺ being allocated to the tetrahedral site formed by oxygens. On the other hand, the results for CoFe₂O₄ suggest that 78% of Co²⁺ occupy the octahedral site, and that the present CoFe₂O₄ sample is classified as inverse spinel, although a partial disorder is included. The usefulness of this AXS method coupled with the common Rietveld analysis was well-recognized by determining the cation distribution even in a system with next neighboring elements of the periodic table.

The structure of molten silicon has been determined at three temperatures of 1440, 1460 and 1520<SUP>°</SUP> C by X-ray diffraction. All structure factors indicate a characteristic small hump on the higher wave vector side of the first peak and such specific feature becomes slightly obscure as the temperature increases. A small peak is found in the region between the first (0.245 nm) and second (0.55 nm) main peaks in the pair distribution functions with a shallow minimum at about 0.35 nm. This is not observed in the pair distribution functions for usual molten metals. The coordination numbers in the near-neighbor region have been estimated by applying the interference function refining technique and the results for the first two neighbors are 6.3 (4.6+1.7) at 1440<SUP>°</SUP> C, 5.7 (4.5+1.2) at 1460<SUP>°</SUP> C and 5.8 (4.4+1.4) at 1520<SUP>°</SUP> C. The present structural information is consistent with the recent results of density and electrical resistivity of molten silicon.

The atomic structure around ferric ions of the ferric hydroxide Fe(OH)3 in aqueous solution has been studied by the anomalous X-ray scattering (AXS) and EXAFS methods. It is found that this ferric hydroxide consists of the FeO6 octahedral unit structure and these octahedral units are connected with the edge and double-comer sharing linkage. On the other hand, the powder of the present ferric hydroxide prepared by freeze-drying the aqueous solution was also studied by the conventional X-ray diffraction method. The atomic structure of ferric hydroxide powder is also found to consist of the FeO6 octahedra connected with the edge and double-comer sharing linkage. Referring to the crystalline structures of other ferric hydroxides and oxides, it is predicted that the FeO6 octahedral chains formed by the edge sharing linkage are connected with the double-comer sharing linkage in the present ferric hydroxide Fe(OH)3 solution and powder. The number of the double-corner sharing linkage in solution is about 60% of that in powder. This implies that the solution structure is characterized by the octahedral chains with a relatively large amount of vacant space.