Showing papers on "Chemical state published in 1986"
TL;DR: In this paper, the chemical state of fission products in irradiated UO2 fuel has been estimated for FBR as well as LWR on the basis of equilibrium calculation with the SOLGASMIX-PV code.
75 citations
TL;DR: In this article, the authors compare the infrared (IR) and X-ray photoelectron spectroscopy (XPS) spectra of Si-rich oxides (SiO x, x 2 and low oxygen content a-Si:H:O alloys) with those of SiO x and XO 2.
65 citations
TL;DR: In situ X-ray absorption near edge experiments have the considerable advantage over others that they can be applied to real catalytic problems, sensing changes in the bonding electron distribution and coordination of the environment of the absorber and resulting in more closely matching models of structure and reaction processes.
Abstract: Publisher Summary Near-edge X-ray absorption (XAS) spectroscopy and techniques related to it by an extension of the photoelectron energy range or a modification in the experimental detection mode have all matured in the past years. The contributions of near-edge X-ray absorption spectroscopy to catalysis and surface science have grown considerably, essentially since the development of synchrotron radiation sources. On a low interpretative level the application of threshold fine-structure effects to catalyst diagnostics has rapidly taken off as atoms in different structural or bonding conditions result in fingerprints that can readily be used for analysis of their structural and chemical state. The near-edge spectroscopy is at its best as an adjunct to other physicochemical characterization methods, such as other XAS techniques, and in combination with XRD, STEM, Auger electron spectroscopy (AES), thermal desorption, and catalytic activity measurements, can expect to bring new insights into the nature of basic catalytic reaction processes. In situ X-ray absorption near edge experiments have the considerable advantage over others that they can be applied to real catalytic problems, sensing changes in the bonding electron distribution and coordination of the environment of the absorber and resulting in more closely matching models of structure and reaction processes.
48 citations
TL;DR: Experiments demonstrate that the near-edge structure in the x-ray absorption coefficient of an element is affected by chemistry and local environment and can be exploited in x-rays both to identify and enhance the detectability of different chemical states of the same element.
Abstract: The near-edge structure in the x-ray absorption coefficient of an element is affected by chemistry and local environment. Experiments demonstrate that this property can be exploited in x-ray imaging both to identify and enhance the detectability of different chemical states of the same element. Chemical contrast images are obtained by digital subtraction of absorption images taken at carefully selected energy values.
28 citations
TL;DR: The effect of argon ion etching on surface composition and chemical state was studied using α-Fe2O3, Na2CrO4, tungsten oxides and some nickel alloys as target materials and employing the XPS technique as discussed by the authors.
22 citations
TL;DR: Auger parameters for a variety of silicon compounds have been measured by a combination of XPS using both AIKα ZrLα characteristic x-radiation, and of XAES using Bremsstrahlung radiation as mentioned in this paper.
Abstract: Auger Parameters for a variety of silicon compounds have been measured by a combination of XPS using both AIKα ZrLα characteristic x-radiation, and of XAES using Bremsstrahlung radiation. The Parameters so derived have then been used to study the chemical states of silicon at and near interfaces in the oxide film formed by air-and CO2-oxidation of Fe/Si alloys. Supportive evidence for the interpretations is provided by the widths and shapes of the silicon KL2,3 L2,3 Auger peaks.
21 citations
TL;DR: In this paper, a laser-induced sputtering from the surface of BaF2 was investigated under ultrahigh vacuum conditions, applying fluences well below the macroscopic damage threshold.
Abstract: Laser‐induced sputtering from the (111) surface of BaF2 was investigated under ultrahigh vacuum conditions, applying fluences well below the macroscopic damage threshold. Measurement of the wavelength‐dependent desorption of Ba+ indicates that Ba+ is emitted from two chemically different surroundings at the surface. For a fixed wavelength, the emission rates of Ba+ and F+ as functions of time show a distinct anticorrelation, confirming the existence of two different chemical states of the surface, and suggesting that the sputtering takes place layer by layer.
20 citations
TL;DR: In this article, the use of X-ray emission microanalysis, electron energy loss spectroscopy and microdiffraction available in a dedicated high resolution STEM is described in the case of metallic and non-metallic catalytic particles deposited on high area supports.
13 citations
01 Jan 1986-International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes
TL;DR: In this paper, a simultaneous multitracer method was applied to a study on micronutrient metal elements in soybean plants, using 59 Fe, 65 Zn and 57 Co as tracers, the uptake and distribution of the three elements fed at different growth stages of the plants were investigated.
7 citations
TL;DR: In this paper, it was shown that the only broad absorption band in the visible region observed in the reflectance spectra of a chrome-tin pink stain would be caused by Cr4+ in this distorted octahedral symmetry.
Abstract: Heating of the mixture of CaCO3, SnO2, SiO2 and Cr2O3 developed reddish color simultaneously with the formation of tin-sphene (CaO⋅SnO2⋅SiO2). Characterization of chromium in tin-sphene by chemical analysis, ESCA and ESR revealed that the chromium was mostly tetravalent. ESR and chemical analyses of vanadium in tin-sphene showed that the vanadium was also mostly tetravalent, substituting for the Sn4+ in the tetragonally distorted octahedral symmetry. It was pointed out that the only one broad absorption band in the visible region observed in the reflectance spectra of a chrome-tin pink stain would be caused by Cr4+ in this distorted octahedral symmetry. Furthermore, chemical states of chromium and tin in glazes containing calcium were studied by ESR and ESCA in connection with the glaze colors.
6 citations
TL;DR: In this article, the influence of supports and preparation methods on the chemical state of the promoter for Pt-Sn catalysts has been studied by Mossbauer spectroscopy and no regular trend or pattern is found for the supports studied.
Abstract: The influence of supports and preparation methods on the chemical state of the promoter for Pt-Sn catalysts has been studied by Mossbauer spectroscopy. No regular trend or pattern is found for the supports studied. Impregnation with a complex compound results in the highest content up to 55% of Sn(O)+Sn (II) in the catalyst. However, if the Sn (IV) state is desired, such catalysts can be prepared and the Sn (IV) state can be stabilized using a specific preparation method.
TL;DR: In this article, surface studies of aluminophosphate and alu-mino silicate molecular sieves have been carried out with x-ray photoelectron spectroscopy methods.
Abstract: Ultrahigh vacuum surface studies of aluminophosphate and alu-mino silicate molecular sieves have been carried out with x-ray photoelectron spectroscopy methods. Both qualitative and quantitative analyses were performed. The C 1s, 0 1s, Na 1s, Al 2p, Si 2p and P 2p transitions were collected with MgK∝ radiation. Narrow scans for each of these elements were collected, when appropriate, with a constant absolute energy mode with a pass energy of 50 eV. Collected data were analyzed with curve resolution procedures to determine the number of surface species. Quantitative analyses were done to determine Si 4+ /Al 3+ ratios of the zeolites and other ratios, Al 3+ /P 5+ ratios, for aluminophosphate molecular sieves. Besides photoelectron lines, x-ray excited Auger lines were also collected. Data from the photoelectron and Auger transitions were used to construct chemical state plots for silicon, aluminum and phosphorous. Data for zeolites have been compared to literature data. These surface studies suggest that there are different regions on both Si and Al chemical state plots for high Si/Al and low Si/Al zeolites. The surface data reported here also suggest that Al 3+ environments for aluminophosphate molecular sieves more closely resemble aluminum-rich faujasitic zeolites rather than aluminum-deficient zeolites like ZSM-5.
TL;DR: In this article, the distribution of tritium in various chemical states depended considerably on the alloy composition, but was little affected by irradiation temperature and neutron fluence in the range studied.
Abstract: Chemical states of tritium formed in lithium-lead alloys irradiated with neutrons were studied using a radiometric method. A scavenger technique was applied to distinguish the LiT fraction from the other species. The distribution of tritium in various chemical states depended considerably on the alloy composition, but was little affected by irradiation temperature and neutron fluence in the range studied. The experimental results could be well explained with the kinetic theory for hot atom reaction and showed some characteristics in the condensed phase.
TL;DR: In this article, the main Fe component is estimated as highly dispersed Fe in the Fe/Pd range of 0.05-0.3 and α-Fe ensemble and Fe−Pd intermetallics in the range above 0.3.
Abstract: Fe-57 Mossbauer spectra of silica-supported Pd−Fe bimetallic catalysts show remarkable changes with varying Fe/Pd atomic ratios. From the spectra, the main Fe-component is estimated as highly dispersed Fe in the Fe/Pd range of 0.05–0.3 and α-Fe ensemble and Fe−Pd intermetallics in the Fe/Pd range above 0.3. It is suggested that the chemical state of iron is associated with the catalytic performance in effective CO−H2 conversion to methanol.
TL;DR: The reactivity of XeF2 and CF3 on thermally grown SiO2 surfaces has been investigated in this paper, where X-ray photoelectron spectroscopy (XPS) was used to determine the chemical state of the surface after exposure to the gases.
Abstract: The reactivity of XeF2 and CF3 on thermally grown SiO2 surfaces has been investigated. CF3 radicals were generated by infrared multiple-photon dissociation of C2F6 using a pulsed CO2 laser. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical state of the surface after exposure to the gases. Both CF3 and XeF2 are relatively inert to annealed SiO2 surfaces. Ion damaged surfaces are much more reactive. Implications for ion enhancement of etching are discussed. XPS spectra reveal fluorine, from XeF2 bonded to both silicon and oxygen. The CF3 radical appears to undergo little dissociation upon chemisorption on SiO2.
TL;DR: In this paper, the yttrium-doped a-poly crystalline alumina was studied by microscopy observations and by extended X-ray absorption fine-structure experiments, and the results were compared to those obtained for a standard Y2O3 powder and to theoretical spectra for Y3Al5O12 calculated on the basis of crystallographic data.
Abstract: Yttrium-doped a-poly crystalline alumina was studied by microscopy observations and by extended X-ray absorption fine-structure experiments. The latter results were compared to those obtained for a standard Y2O3 powder and to theoretical spectra for Y2O3, and Y3Al5O12 calculated on the basis of crystallographic data. Most of the yttrium in the doped alumina is precipitated as a Y3Al5O12 phase. An observed threshold displacement involves a slight valence electron delocalization for the Y3+ ion.
01 Jan 1986-International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry
TL;DR: In this paper, the activity distribution of recoil iodine-128, formed by the (n, γ) reaction, was measured in a series of iodate-nitrate mixed crystals.