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Mapping Platinum Species in Polymer Electrolyte Fuel Cells by Spatially Resolved XAFS Techniques 下载免费PDF全文
Dr. Shinobu Takao Dr. Oki Sekizawa Dr. Shin‐ichi Nagamatsu Dr. Takuma Kaneko Dr. Takashi Yamamoto Dr. Gabor Samjeské Dr. Kotaro Higashi Dr. Kensaku Nagasawa Dr. Takuya Tsuji Dr. Motohiro Suzuki Dr. Naomi Kawamura Dr. Masaichiro Mizumaki Prof. Dr. Tomoya Uruga Prof. Dr. Yasuhiro Iwasawa 《Angewandte Chemie (International ed. in English)》2014,53(51):14110-14114
There is limited information on the mechanism for platinum oxidation and dissolution in Pt/C cathode catalyst layers of polymer electrolyte fuel cells (PEFCs) under the operating conditions though these issues should be uncovered for the development of next‐generation PEFCs. Pt species in Pt/C cathode catalyst layers are mapped by a XAFS (X‐ray absorption fine structure) method and by a quick‐XAFS(QXAFS) method. Information on the site‐preferential oxidation and leaching of Pt cathode nanoparticles around the cathode boundary and the micro‐crack in degraded PEFCs is provided, which is relevant to the origin and mechanism of PEFC degradation. 相似文献
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A. Agui A. Asahi J. Sayama M. Mizumaki M. Tanaka T. Osaka 《Journal of magnetism and magnetic materials》2008
Magnetic circular dichroism (MCD) and X-ray absorption spectra (XAS) at the Co L2,3-edge of [Co/Pd]20 and [CoB/Pd]20 multilayered films, which were fabricated at 260 °C with different magnetic layer thicknesses (δ), have been measured. The lineshapes of XAS–MCD show that the electronic state of Co 3d of the films hardly changes even when sputtered at higher temperatures. The expectation values of orbital and spin angular momentum (〈Lz〉 and 〈Sz〉) are estimated using the sum rule, and it is found that 〈Lz〉/〈Sz〉 in δ<0.5 nm is larger than that in δ>0.5 nm. 相似文献
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Dr. Yasuhide Akizuki Dr. Ikuya Yamada Dr. Koji Fujita Kazuya Taga Dr. Takateru Kawakami Dr. Masaichiro Mizumaki Prof. Katsuhisa Tanaka 《Angewandte Chemie (International ed. in English)》2015,54(37):10870-10874
Of particular interest is a peculiar motion of guest atoms or ions confined to nanospace in cage compounds, called rattling. While rattling provides unexplored physical properties through the guest–host interactions, it has only been observed in a very limited class of materials. Herein, we introduce an A‐site‐ordered quadruple perovskite, CuCu3V4O12, as a new family of cage compounds. This novel AA′3B4O12‐type perovskite has been obtained by a high‐pressure synthesis technique and structurally characterized to have cubic Im$\bar 3$ symmetry with an ionic model of Cu2+Cu2+3V4+4O12. The thermal displacement parameter of the A‐site Cu2+ ion is as large as Uiso≈0.045 Å2 at 300 K, indicating its large‐amplitude thermal oscillations in the oversized icosahedral cages. Remarkably, the presence of localized phonon modes associated with rattling of the A‐site Cu2+ ion manifests itself in the low‐temperature specific heat data. This work sheds new light on the structure–property relations in perovskites. 相似文献
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Electrochemical acylation and ethylaminocarbonylation of amines and alcohols are performed by anodic oxidation of the hydroxamic acids and N-ethyl-N′hydroxyurea, respectively, in acetonitrile at a glassy-carbon electrode. 相似文献
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Akane Agui Masaichiro Mizumaki Koji Matsumoto Junichi Sayama 《Journal of Physics and Chemistry of Solids》2007,68(11):2148-2152
We have carried out X-ray absorption measurements with its magnetic circular dichroism (MCD) of perpendicular magnetic films of DyxCo100−x (15?x?33) at Dy M4,5 and Co L2,3 absorption edges to investigate electronic and spin states of the Dy 4f and Co 3d states, respectively. The replacement of major spin between Dy 4f and Co3d is clearly observed in the spectra between 20?x?25. The expected values of the orbital angular moment ∣〈Lz〉∣ of Dy 4f were estimated to be 1.4-0.8 μB while that of Co 3d was estimated to be around 0.2 μB. 相似文献
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Kubota M Murakami Y Mizumaki M Ohsumi H Ikeda N Nakatsuji S Fukazawa H Maeno Y 《Physical review letters》2005,95(2):026401
We have succeeded in detecting ferro-type orbital states in Ca2-xSrxRuO4, which is the first outcome in a 4d Mott transition system by the resonant x-ray scattering interference technique. For x=0 (Mott insulator), the resonant signal for d(xy) orbital ordering is observed even at room temperature, in which the Jahn-Teller distortion is negligible. The signal disappears near the metal-insulator transition. On the other hand, in a metallic phase for x=0.5, orbital polarization with d(yz/zx) character dominates. With lowering temperature, the magnitude of the resonant signal slightly decreases owing to the additional influence of the gamma band with d(xy) character. 相似文献
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ABSTRACTRecently, nano-polycrystalline diamond (NPD) anvils have been widely applied in high pressure research using X-ray absorption spectroscopy (XAS). The nanometer-sized polycrystallization in NPD anvils enables us to obtain glitch-free X-ray absorption spectra. This advantage of NPD anvils drastically improves the experimental conditions of XAS, which has previously used conventional single-crystal diamond (SCD) anvils. Distorted spectra due to the glitches from the SCD anvils have been an inevitable problem of XAS. This paper reviews recent studies of XAS and related spectroscopic techniques using the NPD anvils, which have mainly been performed on BL39XU of SPring-8. We demonstrate how NPD anvils are useful when using XAS for high pressure research. 相似文献
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Temperature‐Induced Intersite Charge Transfer Involving Cr ions in A‐Site‐Ordered Perovskites ACu3Cr4O12 (A=La and Y) 下载免费PDF全文
Dr. Shoubao Zhang Prof. Takashi Saito Dr. Masaichiro Mizumaki Prof. Yuichi Shimakawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(31):9510-9513
Changes in the valence state of transition‐metal ions in oxides drastically modify the chemical and physical properties of the compounds. Intersite charge transfer (ISCT), which involves simultaneous changes in the valence states of two valence‐variable transition‐metal cations at different crystallographic sites, further expands opportunities to show multifunctional properties. To explore new ISCT materials, we focus on A‐site‐ordered perovskite‐structure oxides with the chemical formula AA′3B4O12, which contain different transition‐metal cations at the square‐planar A′ and octahedral B sites. We have obtained new A‐site‐ordered perovskites LaCu3Cr4O12 and YCu3Cr4O12 by synthesis under high‐pressure and high‐temperature conditions and found that they showed temperature‐induced ISCT between A′‐site Cu and B‐site Cr ions. The compounds are the first examples of those, in which Cr ions are involved in temperature‐induced ISCT. In contrast to the previously reported ISCT compounds, LaCu3Cr4O12 and YCu3Cr4O12 showed positive‐thermal‐expansion‐like volume changes at the ISCT transition. 相似文献