Topic
Chemical state
About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.
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TL;DR: In this paper, the effect of heavy ion irradiation on the crystalline phase transformation of oxide of Zr-2.5Nb alloys has been studied and the variation of the crystal structure along the depth of the irradiated oxide have been characterized non-destructively by Grazing Incidence X-ray Diffraction technique and compared with unirradiated-oxide.
5 citations
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TL;DR: In this paper, the use of high resolution transmission electron microscopy (TEM) or energy filtered TEM (EFTEM) associated to energy dispersive X-Ray analysis (EDX) and electron energy loss spectroscopy (EELS) was discussed.
Abstract: In order to achieve a full characterisation of metal particles nanostructures at the microstructural level, we show in this overview the use of different techniques: i) High resolution transmission electron microscopy (TEM) or energy filtered TEM (EFTEM) associated to energy dispersive X-Ray analysis (EDX) and electron energy loss spectroscopy (EELS). ii) A surface analysis technique like X-Ray photoelectron spectrocopy (XPS). iii) A technique sensitive to the local structure and chemical state like X-Ray absorption spectroscopy (XAS). Two systems will be described to illustrate this study: i) Nickel particles dispersed in an amorphous carbon matrix have been synthesized by a sonication method, and further heated at 773 K under Ar atmosphere. The as-prepared sample shows amorphous spherical particles (TEM) formed by Ni 2þ highly dispersed in carbon (XPS, XAS). The heated sample shows spherical grains formed by nanocrystalline Ni particles embedded in an amorphous carbon matrix (HRTEM). Heterogeneities at micro- and nanoscopic scale have been determined by TEM/EELS and EFTEM. Quantification of the oxidation level for the heated sample was also determined by XAS. ii) Gold nanoparticles modified with neoglycoconjugates molecules have been prepared by a wet chemical method. Aggregates, isolated nanoparticles or two-dimensional self-organised nanostructures have been obtained by controlling the interaction forces between biological significant oligosaccharides. The EFTEM analysis has been used to demonstrate the role of divalent cations in the formation of the nanostructures.
5 citations
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TL;DR: In this paper, first-principles DFT + U calculations are performed to unambiguously determine the actual oxidation states of metal ions in U ternary oxides containing multivalent transition-metals (TMs: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W).
Abstract: Uranium (U) has attracted considerable fundamental and applied studies; among them, the rigorous determination of its chemical state is one of the crucial topics owing to its well-known multivalent feature associated with complicated chemical bonding. However, the related studies on solid-state U ternary or beyond ternary compounds are quite in lack. Herein, first-principles DFT + U calculations are performed to unambiguously determine the actual oxidation states of metal ions in U ternary oxides containing multivalent transition-metals (TMs: Ti, V, Cr, Mn, Fe, Ni, Nb, Mo, W). For the first time, the actual oxidation states of U and TM in the ternary oxides are obtained in a quantitative and atom-resolved manner, thereby providing their nominal compositions. The results disclose the variations of U oxidation states with TM’s properties, chemical surrounding, local structure, and oxygen vacancy. In terms of charge transfer, electronic structure, orbital energy level, and oxygen vacancy effect, I conclude that the oxidation state is the competitive consequence of those electronic and structural factors and that electron-structure-related factors play more important roles. Because of the increasing orbital expansion from 3d to 4d and 5d TMs, the latter TMs (Nb, Mo, W) have the greater tendency to form high oxidation states and suppress the formation of high oxidation states of U. On the contrary, 3d TMs, especially Cr, Mn, Fe, and Ni, tend to adopt low oxidation states, thereby promoting the emergence of high oxidation states of U.
5 citations
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TL;DR: In this paper, Angle-dependent high-resolution XPS spectra of S 2p, In 3d 5/2 and P 2p have been measured on the InP(001) sample etched chemically, treated with (NH 4 ) 2 S x at room temperature (RT), exposed to air at RT and annealed at 400°C in a vacuum.
Abstract: Angle-dependent high-resolution XPS spectra of S 2p, In 3d 5/2 and P 2p have been measured on the InP(001) sample etched chemically, treated with (NH 4 ) 2 S x at room temperature (RT), exposed to air at RT and annealed at 400°C in a vacuum. Three kinds (S-I, S-II and S-III) of chemical states of sulphur on the (NH 4 ) 2 S x -treated InP(001) surface at RT are found. It is suggested that S-I. S-II and S-III correspond to sulphur in the bulk, sulphur bridge-bonded to indium on the surface and elemental sulphur, respectively. Chemical state of S-III is decreased for the treated sample exposed to air at RT for 1 month. It is removed upon annealing the sample at 400°C in a vacuum, while S-I and S-II remain on the surface. The thickness of the sulphide layer on the annealed surface is estimated to be about one monolayer. Angle-dependent XPS spectra of S 2p and In 3d 5/2 are discussed.
5 citations