Ex-situ and in-situ investigations of thermal anti-oxidation treatments of stainless steels by reflection mode EXAFS

Different thermal treatments were performed for the anti-oxidation of steel surfaces, and the processes were investigated ex-situ and in-situ by surface sensitive reflection mode EXAFS experiments at the Cr and Fe K-edges. While the samples for the ex-situ studies were heat-treated in a conveyor belt furnace at temperatures between 600 and 900 °C in inert carrier gases (N2 or Ar) using different additives such as hydrogen (H2) and monosilane (SiH4), the in- situ anti-oxidation treatments have been performed in a high vacuum environment (p < 10-6 mbar). While the ex-situ experiments suggest that SiH4-additives are needed for the reduction of the steel to a metallic state, the in-vacuum treatments appear successful for temperatures above approx. 900 °C.DFG/FR 1388/8-1DFG/Ma 1175/48-

Quick EXAFS setup at the SuperXAS beamline for in situ X ray absorption spectroscopy with 10 ms time resolution

The quick-EXAFS (QEXAFS) method adds time resolution to X-ray absorption spectroscopy (XAS) and allows dynamic structural changes to be followed. A completely new QEXAFS setup consisting of monochromator, detectors and data acquisition system is presented, as installed at the SuperXAS bending-magnet beamline at the Swiss Light Source (Paul Scherrer Institute, Switzerland). The monochromator uses Si(111) and Si(311) channel-cut crystals mounted on one crystal stage, and remote exchange allows an energy range from 4.0 keV to 32 keV to be covered. The spectral scan range can be electronically adjusted up to several keV to cover multiple absorption edges in one scan. The determination of the Bragg angle close to the position of the crystals allows high-accuracy measurements. Absorption spectra can be acquired with fast gridded ionization chambers at oscillation frequencies of up to 50 Hz resulting in a time resolution of 10 ms, using both scan directions of each oscillation period. The carefully developed low-noise detector system yields high-quality absorption data. The unique setup allows both state-of-the-art QEXAFS and stable step-scan operation without the need to exchange whole monochromators. The long-term stability of the Bragg angle was investigated and absorption spectra of reference materials as well as of a fast chemical reaction demonstrate the overall capabilities of the new setup

Preliminary investigation of chlorine speciation in zirconolite glass-ceramics for plutonium residues by analysis of Cl K-edge XANES

A zirconolite glass-ceramic material is a candidate wasteform for immobilisation of chlorine contaminated plutonium residues, in which plutonium and chlorine are partitioned to the zirconolite and aluminosilicate glass phase, respectively. A preliminary investigation of chlorine speciation was undertaken by analysis of Cl K-edge X-ray Absorption Near Edge Spectroscopy (XANES), to understand the incorporation mechanism. Cl was found to be speciated as the Cl- anion within the glass phase, according to the characteristic chemical shift of the X-ray absorption edge. By comparison with Cl K-edge XANES data acquired from reference compounds, the local environment of the Cl- anion is most closely approximated by the mineral marialite, in which Cl is co-ordinate to 4 x Na and/or Ca atoms

Secondary phases and their influence on the composition of the kesterite phase in CZTS and CZTSe thin films

Secondary phases zinc sulfide selenide and copper sulfide in Cu2ZnSnS4 CZTS and Cu2ZnSnSe4 CZTSe thin film samples are investigated by X ray absorption near edge structure XANES analysis at the chalcogen K edges. Because of the formation of secondary phases the composition of the kesterite phase can deviate significantly from the total sample composition. For a large set of non stoichiometric samples we find that the cation ratios of the kesterite phase never exceed Zn Sn 1 even for Zn rich CZTS and CZTSe, with all excess Zn being contained in secondary phases. For CZTS the cation ratios are found to be additionally constrained by Cu Sn amp; 8804; 2, which means that Cu excess always leads to the formation of CuxS secondary phases. These results give clear bounds on the Cu rich and Zn rich sides of the single phase region in polycrystalline CZTS Se thin film

ОБЩИННАЯ ТЕОРИЯ Н.Г.ЧЕРНЫШЕВСКОГО В ИСТОРИОГРАФИИ

Розглядається общинна теорія М.Г.Чернишевского та шляхи її вивчення у дореволюційній та радянській історіоргафії. Вказано на досягнення та вади, які були властиві достідникам цього питання.There is investigated a community theory of N.Cheryshevsky and ways of its studying in prerevolutional and revolutional historiography. There are pointed out faults and achievements of this problem researchers