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排序方式: 共有570条查询结果,搜索用时 109 毫秒
101.
Hiroshi Negishi Saiko Negishi Minoru Sasaki Masasi Inoue Shigeo Ohara 《Molecular Crystals and Liquid Crystals》2013,570(2):63-68
Abstract EXAFS and XANES spectra of Ti K-edge have been measured for 3d transition metal intercalation compounds M x TiS2 (M = Mn, Fe, Co and Ni; x ≤ 0.33). We have found that the interatomic distance between Ti and the first nearest neighbor S atoms, R(Ti-S), increases with the guest concentration x. The variation in XANES spectra with x reveals the reduction of the valence state of Ti atoms upon intercalation of M. From these results as well as the M K-edge EXAFS data studied previously, we have proposed a simple model on the local structure of M x TiS2 to reproduce the observed values of R(Ti-S) by averaging local shift of S atoms caused by intercalation. 相似文献
102.
The sensitivity of tin oxide is dependent on various factors, one of which is the grain size. Three methods have been investigated with the aim of stabilising the grain size in the nanometer range, namely; (i) encapsulation within a silica matrix, (ii) coating the crystallites with hexamethyldisilazane and (iii) pinning the grain boundaries with a second metal oxide nanocrystal. The resulting materials have been characterised by X-ray powder diffraction (XRPD), Extended X-ray absorption fine structure (EXAFS) and conductivity measurements. 相似文献
103.
浓度及冷冻-解冻处理对CuCl_2水溶液中Cu~(2+)区域结构的影响 总被引:1,自引:0,他引:1
应用扩展X射线吸收精细结构(EXAFS)光谱研究了CuCl2水溶液中Cu2+的区域环境结构,通过测定CuCl2水溶液在不同浓度条件下及冷冻-解冻(FT)处理前后CuK边EXAFS吸收谱,研究了浓度及冷冻-解冻处理对Cu2+第一配位层结构的影响.EXAFS实验结果表明,CuCl2水溶液中Cu2+第一配位层距离中心原子Cu最近邻原子为O原子,配位数介于3.0-4.3之间,Cu—O键长在0.192-0.198nm之间,这种结构与Cu2+的Jahn-Teller效应有关.不同浓度的CuCl2水溶液中Cu2+的区域环境结构有很大不同,随着CuCl2水溶液浓度的升高,Cu2+第一配位层配位数减小,Cu—O键伸长.结构参数拟合结果证实冷冻-解冻处理对Cu2+的区域环境结构有影响,CuCl2溶液经冷冻-解冻处理后,Cu2+第一配位层配位数变大,热无序度增加. 相似文献
104.
The local structure of In2O3 cosubstituted with Zn and Sn (In2−2xSnxZnxO3, x≤0.4 or ZITO) was determined by extended X-ray absorption fine structure (EXAFS) for x=0.1, 0.2, 0.3 and 0.4. The host bixbyite In2O3 structure is maintained up to the enhanced substitution limit (x=0.4). The EXAFS spectra are consistent with random substitution of In by the smaller Zn and Sn cations, a result that is consistent with the “good-to-excellent” conductivities reported for ZITO. 相似文献
105.
Yusuke Hamabe Sungbong Jung Hikotaro Suzuki Naoto Koizumi Muneyoshi Yamada 《Journal of synchrotron radiation》2010,17(4):530-539
Ni species on the spent NiMo catalyst from ultra‐deep hydrodesulfurization of gas oil in a commercial plant were studied by Ni K‐edge EXAFS and TEM measurement without contact of the catalysts with air. The Ni–Mo coordination shell related to the Ni–Mo–S phase was observed in the spent catalyst by quasi in situ Ni K‐edge EXAFS measurement with a newly constructed high‐pressure chamber. The coordination number of this shell was almost identical to that obtained by in situ Ni K‐edge EXAFS measurement of the fresh catalyst sulfided at 1.1 MPa. On the other hand, large agglomerates of Ni3S2 were observed only in the spent catalyst by quasi in situ TEM/EDX measurement. MoS2‐like slabs were sintered slightly on the spent catalyst, where they were destacked to form monolayer slabs. These results suggest that the Ni–Mo–S phase is preserved on the spent catalyst and Ni3S2 agglomerates are formed by sintering of Ni3S2 species originally present on the fresh catalyst. 相似文献
106.
Geert Silversmit Hilde Poelman Philippe M. Heynderickx Sergey Nikitenko Philippe F. Smet Roger De Gryse Guy B. Marin 《Journal of Physics and Chemistry of Solids》2009,70(9):1274-88
The redox behaviour of a CuO-CeO2/Al2O3 catalyst is studied under propane reduction and re-oxidation. The evolution of the local Cu and Ce structure is studied with in-situ transmission X-ray absorption spectroscopy (XAS) at the Cu K and Ce L3 absorption edges.CuO and CeO2 structures are present in the catalyst as such. No structural effect on the local Cu structure is observed upon heating in He up to 873 K or after pre-oxidation at 423 K.Exposure to propane at reaction temperature (600-763 K) fully reduces the Cu2+ cations towards metallic Cu0. Quick EXAFS spectra taken during reduction show a small amount of intermediate Cu1+ species. Parallel to the CuO reduction, CeO2 is also reduced in the same temperature range. About 25% of the Ce4+ reduces rapidly to Ce3+ in the 610-640 K temperature interval, while beyond 640 K a further slower reduction of Ce4+ to Ce3+ occurs. At 763 K, Ce reduction is still incomplete with 32% of Ce3+.Re-oxidation of Cu and Ce is fast and brings back the original oxides.The propane reduction of the CuO-CeO2/Al2O3 catalyst involves both CuO and CeO2 reduction at similar temperatures, which is ascribed to an interaction between the two compounds. 相似文献
107.
Polycapillary‐optics‐based micro‐XANES and micro‐EXAFS at a third‐generation bending‐magnet beamline
Geert Silversmit Bart Vekemans Sergey Nikitenko Wim Bras Viktoria Czhech Gyula Zaray Imre Szaloki Laszlo Vincze 《Journal of synchrotron radiation》2009,16(2):237-246
A focusing system based on a polycapillary half‐lens optic has been successfully tested for transmission and fluorescence µ‐X‐ray absorption spectroscopy at a third‐generation bending‐magnet beamline equipped with a non‐fixed‐exit Si(111) monochromator. The vertical positional variations of the X‐ray beam owing to the use of a non‐fixed‐exit monochromator were shown to pose only a limited problem by using the polycapillary optic. The expected height variation for an EXAFS scan around the Fe K‐edge is approximately 200 µm on the lens input side and this was reduced to ~1 µm for the focused beam. Beam sizes (FWHM) of 12–16 µm, transmission efficiencies of 25–45% and intensity gain factors, compared with the non‐focused beam, of about 2000 were obtained in the 7–14 keV energy range for an incoming beam of 0.5 × 2 mm (vertical × horizontal). As a practical application, an As K‐edge µ‐XANES study of cucumber root and hypocotyl was performed to determine the As oxidation state in the different plant parts and to identify a possible metabolic conversion by the plant. 相似文献
108.
Dirk Lützenkirchen‐Hecht Ralph Wagner Ulrich Haake Anke Watenphul Ronald Frahm 《Journal of synchrotron radiation》2009,16(2):264-272
The hard X‐ray beamline BL8 at the superconducting asymmetric wiggler at the 1.5 GeV Dortmund Electron Accelerator DELTA is described. This beamline is dedicated to X‐ray studies in the spectral range from ~1 keV to ~25 keV photon energy. The monochromator as well as the other optical components of the beamline are optimized accordingly. The endstation comprises a six‐axis diffractometer that is capable of carrying heavy loads related to non‐ambient sample environments such as, for example, ultrahigh‐vacuum systems, high‐pressure cells or liquid‐helium cryostats. X‐ray absorption spectra from several reference compounds illustrate the performance. Besides transmission measurements, fluorescence detection for dilute sample systems as well as surface‐sensitive reflection‐mode experiments have been performed. The results show that high‐quality EXAFS data can be obtained in the quick‐scanning EXAFS mode within a few seconds of acquisition time, enabling time‐resolved in situ experiments using standard beamline equipment that is permanently available. The performance of the new beamline, especially in terms of the photon flux and energy resolution, is competitive with other insertion‐device beamlines worldwide, and several sophisticated experiments including surface‐sensitive EXAFS experiments are feasible. 相似文献
109.
通过甩带快淬法制备三元合金(Fe0.81Ga0.19)100-xBx (Fe-Ga-B)和(Fe0.81Ga0.19)100-xInx (Fe-Ga-In)薄带样品,并对Fe-Ga-B合金样品进行热处理。通过高分辨X射线衍射(HRXRD)和扩展X射线吸收精细结构谱(EXAFS)技术表征薄带的微观结构,利用振动样品磁强计和标准电阻应变仪测量了样品的磁性及饱和磁致伸缩系数。研究表明,有序的L12相降低了(Fe0.81Ga0.19)98B2样品的磁致伸缩系数。B原子添加形成的Fe2B相和modified-DO3相有利于提高Fe-Ga合金的磁致伸缩系数。但Fe2B相的饱和磁化强度小于A2相,饱和磁场却远大于A2相,因此随着B含量的增加,Fe-Ga-B薄带的饱和磁化强度逐渐减小,矫顽力逐渐增加。合金中形成的非磁性富In相使得In掺杂Fe-Ga-In合金的磁致伸缩系数和饱和磁化强度均减小。非磁性富In相使晶格产生畸变,减弱了磁弹性效应,并且抑制了磁畴的运动,从而明显地减小了Fe-Ga带材样品的磁致伸缩系数以及饱和磁化强度,提高了Fe-Ga合金的矫顽力。 相似文献
110.