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991.
Ran Li Jinyan Du Yanmei Zheng Yueqin Wen Xinxiang Zhang Wenbin Yang Ang Lue Lina Zhang 《Cellulose (London, England)》2017,24(3):1417-1426
Ultra-lightweight cellulose foams were prepared by regeneration of sodium dodecyl sulfate (SDS)/cellulose/NaOH/urea blend solution via mechanical agitation and then freeze-drying. The morphology and properties of the blend solutions and foams were investigated via optical microscope, rheometer, BET and SEM. As a result, it was found that the inclusion complex structure between cellulose macromolecules and the solvent molecules was not destroyed. Moreover, the bubbles were about 20–50 μm in the solutions and larger (>100 μm) in the foams. Not only the micropores (bubbles) but also the nanopores could be observed in the wet and dried foams. The cellulose foams possessed ultra-low density of about 30 mg/cm3 and high specific surface area. The result of X-ray diffraction and Fourier transform infrared spectroscopy indicated that the cellulose foams were transited from cellulose I to cellulose II after dissolution and gelation. Bubbles inside the wet foams weakened the mechanical properties, but inversely increased the mechanical properties in the dried foams. Typical “J”-shaped curves were observed during the mechanical test, which revealed good compressive strength of dried foams. In this work, cellulose foams with ultra-lightweight and good mechanical properties were obtained, which exhibited great potentials for further development and comprehensive utilization of cellulose. 相似文献
992.
993.
Tian Jin Lu Zhao Maolin Huang Yan Yue Zhe-Bin Zheng Won-Hun Ham 《Tetrahedron: Asymmetry》2017,28(5):725-729
Concise stereoselective syntheses of (?)-clavaminol A and deacetyl (+)-clavaminol H have been achieved from simple starting materials. Highlights of the synthesis for (?)-clavaminol A include a highly diastereoselective chelation-controlled hydride reduction of an amino ketone to give the anti amino alcohol directly, and NaBH4-mediated dehalogenation. The main synthetic approach for deacetyl (+)-clavaminol H features a highly diastereoselective chelation-controlled hydride reduction of the amino ketone to construct the anti amino alcohol and a palladium catalyzed hydrogenation reaction at the final step. 相似文献
994.
Evolution of concentration fluctuation during phase separation of polystyrene/poly(vinyl methyl ether) blend in the presence of nanosilica 下载免费PDF全文
Qi Chen Min Zuo Ruiquan Yang Jifei Zhang Xiong Lv Wenjing Zhang Yihu Song Qiang Zheng 《Journal of Polymer Science.Polymer Physics》2017,55(17):1337-1349
The influence of nanosilica on the concentration fluctuation of polystyrene/poly (vinyl methyl ether) (PS/PVME) mixtures was investigated during phase separation. The amplitude of concentration fluctuation was quantified by dielectric spectrums based on the idea of Lodge–Mcleish model and the linearized Cahn–Hilliard theory could describe the amplitude evolution of concentration fluctuation at the early stage of phase separation. Hydrophilic nanosilica A200 dispersed in PVME‐rich phase behaved an obvious inhibition effect on the concentration fluctuation of blend matrix, while hydrophobic nanosilica R974 dispersed in PS‐rich phase had little effect on the concentration fluctuation. The kinetics and amplitude evolution of concentration fluctuation during phase separation for PS/PVME/A200 nanocomposites were remarkably restrained due to the surface adsorption of PVME on A200. As the segmental dynamics of PVME and PS in homogeneous matrix was hardly influenced by A200 and R974, the enhanced miscibility and the significantly constrained flow relaxation of PVME chains might contribute to the retarded concentration fluctuation of PS/PVME/A200 nanocomposites. While the weak interaction between R974 and components of blend matrix and little effect of R974 on the molecular dynamics of PS chains may result in the weak retardation of concentration fluctuation for blend matrix. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1337–1349 相似文献
995.
996.
Yao Chengli Zhu Jinmiao Li Hongying Zheng Bin Wei Yanxin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(13):2680-2685
Russian Journal of Physical Chemistry A - Zinc oxide (ZnO) nanostructured materials have received significant attention because of their unique physicochemical and electronic properties. In... 相似文献
997.
QIN Qing HUANG Nan LIU Wei-Bin LIU Yu-Dong PENG Yue-Mei QIU Jing WANG Dou WANG Xin-Hao WANG Na WANG Jiu-Qing WEI Yuan-Yuan WEN Xue-Mei XING Jun XU Gang Yu Cheng-Hui ZHANG Chuang ZHANG Yuan ZHAO Zheng ZHOU De-Min 《中国物理C(英文版)》2009,33(Z2)
During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider(BEPC Ⅱ),which started on Nov.12,2006 and Oct.24,2007,respectively,we got the luminosity one tenth of its design value,provided beams to synchrotron radiation users for about 4 months,and studied beam dynamics as well.In this paper,some beam dynamics studies on the storage rings and their preliminary results are given. 相似文献
998.
A novel plasmonic nanolens formed by a tapered subwavelength metal slit surrounded by surface dielectric gratings is proposed and demonstrated numerically. By patterning surface corrugations on the output surface, the beam can be focused, by regulating the aperture, the focal length can be controlled effectively. Numerical simulations using Finite-Difference Time-Domain (FDTD) method coupled with anisotropic perfectly matched layer (APML) boundary conditions verify that the proposed metallic lens can focus the radiation on the scale of a wavelength below the substrate and the method is effective for the design of nano-optical devices such as optical microprobes. 相似文献
999.
Three new compounds, 2‐methoxy‐3,4‐(methylenedioxy)benzophenone ( 1 ), 4‐hydroxy‐2,3‐dimethoxybenzophenone ( 2 ), and 3‐hydroxy‐4,6‐dimethoxy‐9H‐xanthen‐9‐one ( 3 ), besides three known compounds were isolated from the roots of Securidaca inappendiculata. Their structures were established by spectroscopic means and X‐ray crystallographic diffraction analysis. The biogenetic relationships among these six compounds are discussed. 相似文献
1000.