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排序方式: 共有193条查询结果,搜索用时 15 毫秒
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Dr. Yun Wu Dr. Wei Wang Dr. Lingli Liu Dr. Sane Zhu Dr. Xiaochen Wang Dr. Enzhu Hu Dr. Kunhong Hu 《ChemistryOpen》2019,8(3):333-338
The use of metal complex immobilized/decorated porous materials as catalysts has found various applications. As such, finding a new and mild method for synthesis of metal complex immobilized over porous material is of great interest. Immobilized porous materials for styrene oxidation were reported in this work. Immobilized porous material of Cu-Schiff base complex @MIL-101 were described, in which immobilized Cu-Schiff base complex within super cage of a metal-organic framework (MOF)-based porous material, chromium (III) terephthalate MIL-101. They were systematically characterized by using elemental analysis, powder X-ray diffraction, fourier transform infrared spectroscopy, N2 absorption-desorption, and so on, also used as catalyst for the selective oxidation of styrene to benzaldehyde. Comparatively, the immobilized heterogeneous catalyst of Cu-Schiff base complex@MIL-101 acted as an efficient heterostructure catalyst in the oxidation of styrene to benzaldehyde up to six cycles, and showed superior activity for styrene oxidation over MIL-101. 相似文献
63.
In this work, a simple and effective method to modify the surface of single sisal fibers with G. xylinum was described. Single fiber tensile strength test, single fiber fragmentation test, thermal gravimetric analyses were conducted to assess the effects of different modification methods (unmodified, NaOH treatment and BC treatment). Fourier transform infrared spectroscopy, scanning electron microscopy and water uptake experiments were employed to characterize the resulting interfacial adhesion. It was shown that BC treatment produced better reinforced polymer composites with improved mechanical and long-term properties. The results also elucidated that BC nanofibrils formed a dense three dimensional network on single sisal fibers covering the roughened surface and filling the grooves and other surface ‘defects’ caused by NaOH modification in addition to its exposed hydroxyl groups to form hydrogen bonds with sisal fiber, all contributed to enhanced mechanical properties of sisal fibers as well as the better binding between sisal fibers and resin matrix. Moreover, this work also confirmed that internal geometrical and morphological differences exist in sisal fibers and this result is insightful for future natural fiber research about the importance of careful selection of fibers for consistent comparisons. 相似文献
64.
Jifeng Liu Xiaochen Sun Yu Bai Kenneth E. Lee Eugene A. Fitzgerald Lionel C. Kimerling Jurgen Michel 《中国光学快报(英文版)》2009,(4):271-273
We report an above-band-gap radiative transition in the photoluminescence spectra of single crystalline Ge in the temperature range of 20-296 K. The temperature-independence of the peak position at -0.74 eV is remarkably different from the behavior of direct and indirect gap transitions in Ge. This transition is observed in n-type, p-type, and intrinsic single crystal Ge alike, and its intensity decreases with the increase of temperature with a small activation energy of 56 meV. Some aspects of the transition are analogous to III-V semiconductors with dilute nitrogen doping, which suggests that the origin could be related to an isoelectronic defect. 相似文献
65.
66.
Zhenzhou Cheng Feng Song Changguang Zou Ruiyuan Su Xiaochen Yu Weiping Zang Jianguo Tian Shibin Jiang 《Optical and Quantum Electronics》2008,40(13):1021-1031
In this work, a model for analyzing the gain characteristics of heavily Er3+/Yb3+ co-doped compact fiber amplifier is presented. Four-level rate equations and finite-difference beam propagation method are
applied to simulate the optical field evolution along the active fiber. Based on this model, the influences of ion concentration,
fiber length and pump power on the gain characteristics of Er3+/Yb3+ co-doped phosphate glass fiber amplifiers are theoretically investigated. Numerical results show that for a fiber length
of 3.6 cm the internal gain can reach 27.2 dB with N
Er = 2.6 × 1026 ions/m3 and N
Yb = 1.2 × 1027 ions/m3 when pumped with 224 mW at 980 nm. The gain per centimeter is 7.56 dB/cm. The results can provide useful information to optimize
the gain performance of these compact fiber amplifiers. 相似文献
67.
To comprehensively control the corner separation and mid-span boundary layer (BL) separation, this study proposed and evaluated two new flow control configurations. One is a slotted configuration composed of blade-end and whole-span slots, and the other is a combined configuration with end-wall BL suction and whole-span slot. Additionally, the adaptability of the combined configuration to the lower blade solidity (c/t) condition was verified. The results indicate that both the slotted configuration and combined configuration can eliminate the mid-span BL separation, but a better reduction in the corner separation can be observed in the combined configuration. The two configurations can remove the concentrated shedding vortex and reduce the passage vortex (PV) for the datum cascade, but the wall vortex (WV) will be generated. By contrast, the combined configuration has weaker WV and PV than the slotted configuration, which contributes to further reducing the corner separation. In the combined configuration with a c/t of 1.66 and 1.36, the total pressure loss is reduced by 38.4% and 42.1%, respectively, on average, while the averaged static pressure rise coefficient is increased by 16.2% and 17.6%, respectively. This is advantageous for enhancing the working stability and pressure diffusion capacity for compressors. Besides this, the combined configuration with lower c/t can achieve a stronger pressure diffusion capacity and smaller loss than the higher c/t datum cascade. Therefore, the combined configuration is advantageous to the improvement of the aero-engine thrust-to-weight ratio through decreasing the compressor single-stage blade number. 相似文献
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70.
Xiaoli Tian Jianpeng Zong Yusai Zhou Dapeng Chen Jia Jia Shuaibin Li Xiaochen Dong Yuhua Feng Hongyu Chen 《Chemical science》2021,12(10):3644
The plasmonic property of a nanostructure is highly dependent on its morphology, but there are few methods for appending a domain as the “functional group” or modifier. As a means of modulating plasmonic properties, we create and modulate Au hats on Au nanoparticles, including mortarboards, beret hats, helmets, crowns, antler hats and antenna hats. The structural control arises from the active surface growth as a result of dynamic competition between ligand absorption and metal deposition. It allows the continuous tuning of hat morphologies, from the facet-controlled growth of mortarboards, to the spreading-favored growth of beret hats and helmets, and to the vertical growth of pillars in crowns, antler hats and antenna hats. Among these plasmonic nanostructures, the mortarboards show excellent SERS enhancement of 8.1 × 105, which is among the best in colloidal nanostructures; and the antler hats show the photothermal conversion efficiency of 66.2%, which compares favorably with the literature reports.We show that active surface growth is an effective method to create structural variety in the appending domain of Au seeds. The dynamic competition between the growth sites led to different Au hats on seeds. 相似文献