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排序方式: 共有74条查询结果,搜索用时 15 毫秒
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M. Hiroi M. Sera N. Kobayashi T. Nagata H. Fujino J. Akimitsu 《Journal of Low Temperature Physics》1999,117(5-6):1677-1681
Results for low temperature specific heat for single crystals of ladder/chain materials Sr
14–x
Ca
x
Cu
24
O
41
(x= 0, 8, 10, 11.5) in magnetic field up to 15 T are reported. A sharp peak of the specific heat of a single crystal Sr
2.5
Ca
11.5
Cu
24
O
41, was found at 2.3 K, clearly indicating the onset of a long range order. In measurements of the specific heat in magnetic fields the transition temperature, T
N
, was found to shift to lower temperatures with increasing magnetic field, indicating that the ordering is antiferromagnetic, which has been confirmed by neutron scattering measurements. With decreasing x T
N
rapidly shifts to lower temperatures. For x=10 T
N
decreases to 1 K and for x= 0 no anomaly indicating the transition was found down to 0.6K 相似文献
4.
5.
In this paper,a technique for designing 3-D separable-denominator state-spacedigital filters is developed. The design process is divided intotwo phases. First, the coefficient matrices related to stabilityare constructed for the filter to be stable by using alternatingvariable method. Next, the other matrices are obtained by solvinglinear equations. These phases are repeated until there is nosignificant change in the squared error function. 相似文献
6.
Disposable Australian iron-slurry (AL) and NiO-MoO3-Al2O3 (NiMo) catalysts were used in hydrocracking experiments to convert Marlim vacuum residue (ML-VR) in a slurry-bed continuous flow reactor at temperatures of 440-460 °C, under a hydrogen pressure of 14.7 MPa and an LHSV of 0.5. The degree of conversion ranged from 54 to 83%, depending on the reaction temperature and catalyst used, with AL giving more complete conversion than NiMo. AL also proved more active in the removal of nickel. Hydrogen consumption was linearly correlated with conversion regardless of the catalyst used. 相似文献
7.
Zirconium oxides (ZrO2−x) have been investigated as new cathodes for direct methanol fuel cells without platinum. ZrO2−x films were prepared using a radio frequency (RF) magnetron sputtering at RF powers from 75 to 175 W. The influence of the RF power on the catalytic activity for the oxygen reduction reaction (ORR) and properties of the ZrO2−x films were examined. The ORR activity of the ZrO2−x catalyst increased with the RF power in the range we studied. The onset potential for ORR over ZrO2−x deposited at 175 W was 0.88 V vs RHE. In addition, the relationship between the ORR activity and the composition, crystallinity, electric conductivity, as well as the ionization potential has been investigated. The zirconium oxide with an oxygen defected state and the higher electric conductivity showed the higher ORR activity, and the electrocatalytic activity for ORR increased with the decreasing in the ionization potential of the ZrO2−x catalyst. 相似文献
8.
Progress in non-precious metal oxide-based cathode for polymer electrolyte fuel cells 总被引:1,自引:0,他引:1
Akimitsu Ishihara 《Electrochimica acta》2010,55(27):8005-252
The cathode catalysts for polymer electrolyte fuel cells should have high stability as well as excellent catalytic activity for oxygen reduction reaction (ORR). Group 4 and 5 metal oxide-based compounds have been evaluated as a cathode from the viewpoint of their high catalytic activity and high stability. Although group 4 and 5 metal oxides have high stability even in acidic and oxidative atmosphere, they are almost insulator and have poor ORR activity because they have a large band-gap. It is necessary to modify the surface of the oxides to improve the ORR activity. We have tried the surface modification methods of oxides into four methods: (1) formation of complex oxide layer containing active sites, (2) substitutional doping of nitrogen, (3) introduction of surface oxygen defect and (4) partial oxidation of carbonitrides. These modifications were effective to improve the ORR activity of the oxides. The solubility of the oxide-based catalysts in 0.1 mol dm−3 at 30 °C under atmospheric condition was mostly smaller than that of platinum black, indicating that the oxide-based catalysts had sufficient stability compare to the platinum. The onset potential of various oxide-based cathodes for the ORR in 0.1 mol dm−3 at 30 °C achieved over 0.9 V vs. a reversible hydrogen electrode. 相似文献
9.
Zhenxiang Cheng Kiyoshi Ozawa Minoru Osada Akimitsu Miyazaki Hideo Kimura 《Journal of the American Ceramic Society》2006,89(4):1188-1192
We have demonstrated a synthetic procedure for nano-sized NaNbO3 powder and its thin films using a carbon-free precursor prepared by the reaction of H2 O2 with sodium and niobium alkoxides. A combination of X-ray powder diffraction, Raman spectra, and thermal gravity and differential thermal analysis, carbon analysis, fourier transform infrared spectra, transmission electron microscopy, and atomic force microscopy was used to characterize the resulting materials and precursor compounds. Results show that this procedure demonstrates the major advantages of low-temperature synthesis (∼400°C) and low weight loss during transformation into NaNbO3 because of its carbon-free nature, which also provides the option of preparing nano-sized particles and dense, crack-free NaNbO3 thin films. 相似文献
10.
Yoshio Yamada Akimitsu Matsumura Teruo Kondo Koji Ukegawa Etsuro Nakamura 《Petroleum Science and Technology》1984,2(2):165-176
The behavior of radicals formed in hydrotreated coal liquid with heat treatment and the influence of oxygen have been investigated by electron spin resonance (e.s.r.) spectroscopy. A set of e.s.r. spectral lines identified as phenalenyl radical appears from 50°C as the oil is heated in argon atmosphere. The radical concentration is enhanced with temperature, reaches a maximum between 130 and 150°C and then decreases at higher temperatures. The radical is very stable even at 200°C for the sample hydrotreated under mild condition, whereas the radical in the sample treated under severe conditions disappears drastically from 150°C. When oxygen is introduced in the oil, the radical is converted into semiquinone and/or aryloxy radicals and stable molecules. The treatment in the presence of oxygen at higher temperatures is considered to accompany the formation of other aryloxy radicals by the reaction of aromatic hydrocarbons and oxygen. 相似文献