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排序方式: 共有919条查询结果,搜索用时 15 毫秒
31.
Yusaku Takita Jun-ichi Moriyama Hiroyasu Nishiguchi Tatsumi Ishihara Fusakazu Hayano Tetsuo Nakajo 《Catalysis Today》2004,88(3-4):103-109
Activity for hydrolysis of CCl2F2 (CFC12) on various metal sulfate was investigated. Zr(SO4)2 was found to be the most active while FeSO4, Cr2(SO4)3, Al2(SO4)3, La2(SO4)3 and Ce2(SO4)3 had intermediate activity. MnSO4, CoSO4, and MgSO4 showed low activity and SrSO4, CaSO4, and BaSO4 had even less activity. The major carbon containing product was CO2 and small amount of CClF3 and CO were formed over several sulfates. The crystal structure of the sulfates was stable during decomposition of CCl2F2, and the conversion reached a steady state after initial decrease at 275 °C over Zr(SO4)2 catalyst. The concentration of surface hydroxyl was larger than that over AlPO4-based catalysts and a reaction mechanism similar to that over AlPO4-based catalysts was proposed. 相似文献
32.
Titanium bis(2-pyridinethiolate) complexes, Ti(6-R-SPy)2(NMe2)2 (6-R-SPy = 6-R-2-pyridinethiolate, 3a: R = H; 3b: R = Me; 3c: R = Ph; 3d: R = C6H4-4-Me; 3e: R = C6H4-4-t-Bu; 3f: R = C6H3-3,5-Me2), and the titanium bis(2-pyridinolate) complexes, Ti(6-Ph-OPy)2(NMe2)2 (6-Ph-OPy = 6-phenyl-2-pyridinolate, 8) were prepared by treating Ti(NMe2)4 with 2 equiv. of 6-R-2-pyridinethiol or 6-Ph-2-pyridinol. The cis-configuration of the diamido moieties in the pseudo octahedral geometry was elucidated by X-ray crystallography for 3a. Reaction of M(NMe2)4 (M = Ti, Zr) with 4 equiv. of 2-pyridinethiol cleanly gave tetrakis(pyridinethiolate) complexes, M(6-H-SPy)4·THF (6: M = Ti; 7: M = Zr). The triangular dodecahedral geometries of 6 and 7 were also revealed by X-ray crystallography. These complexes catalyzed ethylene polymerization upon activation with MAO (methylaluminoxane) or MMAO (modified MAO). The catalytic activities of titanium bis(6-aryl-pyridinethiolate) systems were found to be remarkably higher than that of titanium bis(6-methyl-pyridinethiolate) system. Among the complexes synthesized in this study, Ti[6-(C6H3-3,5-Me2)-SPy]2(NMe2)2 (3f)/MMAO showed the highest activity (1200 kg/Ti-mol h atm) for ethylene polymerization at 60 °C under atmospheric pressure. In contrast, the activity of the corresponding 6-aryl-pyridinolate system 8/MMAO was rather low (9.3 kg/Ti-mol h atm). Both the N-S chelating structure and the bulky aryl substituents are essential for the high activities of the 6-aryl-pyridinethiolate complexes. 相似文献
33.
Munehisa Yasuniwa Shinsuke Tsubakihara Koji Iura Yoshinori Ono Yusuke Dan Kazuhisa Takahashi 《Polymer》2006,47(21):7554-7563
The crystallization behavior of poly(l-lactic acid) was studied in the range of 80-160 °C. The peak crystallization time (τp) was defined and obtained from the crystallization isotherm measured with a differential scanning calorimeter (DSC). Isothermal crystallization temperature (Tc) dependence of log(τp) discretely changed at 113 °C (= Tb). The linear growth rate of spherulite, G, was measured with a polarizing microscope. The Tc dependence of G and the size of the spherulite also discretely changed at Tb. Crystal structures for samples isothermally crystallized at temperatures which were higher and lower than Tb were orthorhombic (α-form) and trigonal (β-form), respectively. The discrete change of the crystallization behavior was explained by the formation of different crystal. 相似文献
34.
Tatsumi Ishihara Kuninobu Shimose Takanari Kudo Hiroyasu Nishiguchi Taner Akbay Yusaku Takita 《Journal of the American Ceramic Society》2000,83(8):1921-1927
A yttria-stabilized zirconia (YSZ) thin film on an La0.8 Sr0.2 MnO3 porous cathode substrate was prepared, using electrophoretic deposition (EPD) to fabricate a solid oxide fuel cell (SOFC). The electrical conductivity of an La0.8 Sr0.2 MnO3 substrate is satisfactorily high at room temperature; therefore, YSZ powder could be deposited electrophoretically onto an La0.8 Sr0.2 MnO3 substrate without any extra surface treatment, such as a metal coating. Successive repetition of EPD and sintering was required to obtain a film without gas leakage, because of the thermal expansion coefficient mismatch between the YSZ and the La0.8 Sr0.2 MnO3 substrate. On the other hand, the electromotive force of the oxygen concentration in the cell that used YSZ film prepared via EPD increased and attained the theoretical value when the number of deposition and calcination cycles was increased. Six or more successive repetitions were required to obtain a YSZ film without gas leakage. A planar-type SOFC was fabricated, using nickel as the anode and YSZ film (∼10 μm thick) that had been deposited onto the La0.8 Sr0.2 MnO3 substrate as the electrolyte and cathode. The cell exhibited an open circuit voltage of 1.0 V and a maximum power density of 1.5 W/cm2 . Thus, the EPD method could be used as a colloidal process to prepare YSZ thin-film electrolytes for SOFCs. 相似文献
35.
毛细管电泳仪具有灵敏度高、分析速度快等优势,为降低其生产成本,基于电泳原理,以荧光显微镜为基础,设计了一套毛细管电泳系统。以20 bp(base pairs,碱基对)DNA ladder和100 bp DNA ladder为样本,全面分析了系统的稳定性、灵敏度和分离效果。结果表明:该系统在9 min内可以实现1500 bp以内DNA片段的高效分离,系统检测极限为0.1 ng/μL;在优化的电泳条件下,对限制性内切酶φX174-HincⅡ作用过的λ-DNA片段5 min内实现了291 bp与297 bp DNA片段的区分。 相似文献
36.
Haksung Kim Cheol Ho Pyeon Yoshinori Sakurai Tsuyoshi Misawa 《Annals of Nuclear Energy》2011,38(11):2541-2549
Significant axial variation of radial uniformity is observed in Si-ingot neutron transmutation doping in the flux screening method, and leads to non-uniform resistivity distribution for a certain part of Si-ingot. This axial variation of radial uniformity is caused by the installation of a partial neutron screen which decreases the reaction rates differently in the center and surface at the region not surrounded by the partial neutron screen. For the improvement of the specific distribution of radial uniformity in the axial direction, a new concept of axial reflector is introduced to partly change the reaction rate at a certain region of Si-ingot, and neutron irradiation experiments are carried out at the heavy water neutron irradiation facility in the Kyoto University Research Reactor. Based on the experimental and numerical results, the new axial reflector is proved to be effective for improving the axial variation of radial uniformity. 相似文献
37.
Parametric analyses in drying processes of molded ceramics are performed to investigate the influence of heating modes on the formation of drying-induced strain-stress as well as the drying characteristic. The transient three-dimensional problem of strain-stress and heat and moisture transfer in a slab is solved simultaneously by the finite element method. Three modes of hot air, intermittent and internal heating are compared by modeling in the normalized parameters. The tensile and compressive stresses fluctuate, and fall remarkably during the low Biot number period when the slab is heated intermittently. In the internal heating mode, the drying rate is the fastest but stress formation is maintained at the lowest level among the three modes. This effectiveness of the internal heating is investigated experimentally by employing the microwave heating as well. 相似文献
38.
Qiang Dong Nobuhiro Kumada Yoshinori Yonesaki Takahiro Takei Nobukazu Kinomura Dan Wang 《Journal of Materials Science》2010,45(20):5685-5691
Hollow hematite (α-Fe2O3) microspheres with an average diameter of 3-4 μm and a shell thickness of approximate 150 nm was synthesized by a simple
hydrothermal route using FeCl3·6H2O solution and acetic acid without using any templates. The hollow microspheres were composed of α-Fe2O3 nanoparticles with the diameter range from 20 to 40 nm. The effects of reaction parameters such as reaction time, temperature,
concentration of FeCl3·6H2O solution, and initial pH on the morphology of the final products were investigated. A possible formation mechanism of hollow
α-Fe2O3 microspheres was also proposed, where the acetic acid played a role of etching in the formation of hollow structure. 相似文献
39.
Ryuichi Tayama Katsumi Hayashi a Ryo Iwasaki Masana Sasaki Yoshinori Etoh Hiroshi Sakurai 《Nuclear Engineering and Design》2001,210(1-3):239-248
A neutron-scanning device was developed for measuring accurate neutron densities of BWR high burn-up fuels up to 65 GWd tU−1. Characteristic test of this device was done with a 252Cf source and adopted to measure axial distributions of neutron densities of BWR spent fuels with various enrichments (2.0–3.4%), which had been irradiated up to 60 GWd tU−1 at Fukushima Daini Nuclear Power Station Unit 2(2F-2). We found the measured neutron densities were proportional to about fourth power of the corresponding burn-up values. The neutron densities calculated by the ORIGEN2.1 code and various cross section libraries showed good agreements with the measured ones in profile and absolute value except for BWR-UE file mainly based on ENDF/B-IV. The BS240J32 library based on JENDL3.2 was the best among the investigated libraries. 相似文献
40.