Papers by Keyword: Core-Shell Structure

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Authors: Wei Liu, Chun Hua Zhou, Guang Qiang Xu, Ying Feng
Abstract: Sodium 2-olefinsulfonate (AOS) is used as reactive surfactant to prepare 10 nm around magnetic CoFe2O4 nanoparticles in advance. Magnetic P(St-BA-AOS)-coated CoFe2O4 composite nanoparticles has been synthesized in situ soapless emulsion. The effects of the amount of the initiator, monomer concentration and polymerizing temperature on the convention of monomer are investigated. So the polymerizing conditions are KPS=4.010-3mol/l St=0.75mol/l, mMP=20g/l, T=75 BA=0.15mol/l t=6.0h [AOS]=2% without any surfactant in the latex system. Results of IR and TEM analysis demonstrate that the desired polymer chains has been covalently bonded to the surface of CoFe2O4 nanoparticles, and confirmed that the composite particles have the core-shell structure. Copolymer P(St-BA-AOS) has a good hydrophile ability with functional groups such as -SO3Na and -COO- groups. The saturated magnetization of CoFe2O4/ P(St-BA-AOS) composite could reach 2.10emu/g, and show the characteristics of super-paramagnetism.
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Authors: Shi Chao Xu, Yue Qian Yang, Yan Shan Liu, Heng Miao, Mei Dong, Juan Yang, Ji Mei Zhang, Zhao Dai, Guo Zheng, Bo Sun, Shu Qing Sun, Zhen Zhong Jiang
Abstract: The core-shell CdTe/ZnS quantum dots were prepared with an improved process in aqueous phase. CdTe QDs were synthesized under conditions of pH 9.1, 96 °C, refluxing for 5h, and which was used as core material; ZnS was formed as shell material to enhance the optical properties. Optical properties were characterized with fluorescence spectrum (FS), and morphology of QDs was investigated via transmission electron microscopy (TEM) method. Moreover, composition and formation of CdTe/ZnS core-shell QDs was characterized via x-ray diffraction (XRD) method. Optimum conditions were investigated to obtain the qualified CdTe/ZnS core-shell QDs, the results indicated QDs with high quantum yields and fluorescence intensity were achieved under conditions of pH 9.0, 45 °C, refluxing for 1h, and v/v/v ratio of CdTe/Na2S/ZnSO4 is 4/1/1. The TEM data indicated that average size of 5 nm CdTe core was prepared, and CdTe/ZnS core-shell QDs with average size of 11 nm were achieved under the optimum conditions. ca 30nm of red shift of a maximum emission wavelength from ca 530 nm (CdTe) to 560 nm (CdTe/ZnS) was observed via FS under the optimum conditions, which inferred the growth of QDs and formation of ZnS shells. Furthermore, the enhanced fluorescence intensity of CdTe/ZnS core-shell QDs was detected and over two times of fluorescence intensity was increased after formation of ZnS shell. The obtained QDs will have great potential application in biological researches and biosensing system based on fluorescence resonance energy transition (FRET).
212
Authors: Shi Zhao Kang, Tan Wu, Xiang Qing Li, Yi Lun Zhou, Jin Mu
Abstract: Core-shell montmorillonite-TiO2 colloids were prepared in a hydrothermal process and characterized with transmission electron microscope, powder X-ray diffraction analysis, Brunauer-Emmett-Teller analysis and UV-vis spectra. Afterwards, their photocatalytic activity was investigated under UV irradiation using methyl orange as a model contaminant. In addition, the stability of the core-shell montmorillonite-TiO2 colloids was investigated by repeatedly performing methyl orange photocatalytic degradation experiments. The results indicate the as-prepared core-shell montmorillonite-TiO2 colloids are a highly efficient photocatalyst for the degradation of organic dyes in water. And this photocatalytic activity remains almost unchanged after eight successive cycles.
404
Authors: Gui Mei Shi, Wei Min Sun, Da Wei Lu, Shu Lian
Abstract: Fe nanoparticles with shell of Ni-P coating layer were successfully synthesized using Ni electroless plating process. Electromagnetic-wave absorption of Ni-P coated Fe nanoparticles has been investigated. In contrast to earlier reported materials, the absorption amplitude of as-prepared samples is found not largely decrease with increasing absorption-layer thickness. A reflection loss (RL) exceeding -20 dB can be obtained for almost the whole frequencies within the 2-18GHz range by choosing an appropriate layer thickness between 0.9 and 6.0mm. The broadest bandwidth (RLu-bands(12-18GHz), is obtained for 1.1mm layer. At the same time, it is worth noticing that in a thin thickness range 0.91-2.0mm, the reflection loss (RL) exceeding -10 dB in the 6-18GHz range is obtained, which covers half of C-bands (4-8GHz), the whole X-bands (8-12GHz) and Ku–bands (12-18GHz).
665
Authors: Di Fang Zhao, Ming Hua Li, Jin Song Xie
Abstract: In this work, Core-shell structure palygorskite/nanoCaCO3 (PnC) composite particles have been synthesized chemically, employing solution precipitation methods. Crystal structure, morphology and thermal stability properties are investigated by means of X-ray diffraction (XRD), transmission electronic microscopy (TEM) and Thermogravimetric (TG) analysis. The results showed that the PnC particles were almost monodispersed microsphere aspect with the size was about 1-3 μm diameter. The nanocomposite particles exhibit the marked thermal stability properties than the palygorskite clay mineral.
348
Authors: Yi Zhou, Xiao Ping Wang, Wen Yi Li, Hui Li, Ming Tian, Xia Wang
Abstract: Coaxial nanocomposites were prepared by in–situ chemical polymerization of 4– dibromomethyl–2,5–2–octyloxy phenylene in the presence of multiwall carbon nanotubes. The morphology, microstructure and thermal and electrochemical properties of the resulting nanocomposites were investigated by scanning electron microscopy, Fournier infrared spectroscopy, thermal gravimetric analysis and cyclic voltammetry. The results indicated that the nanocomposites with uniform core-shell structure exhibited higher thermal stability than neat poly (phenylene vinylene). Furthermore, energy storage ability of these coaxial nanocomposites as electrode materials for supercapacitor was evaluated.
325
Authors: Run Zhou Huang, Cheng Jun Zhou, Yang Zhang, Qing Lin Wu
Abstract: As a new-generation green composite, core-shell structure nature fibers/ polymer composites (NFPC) has been recently developed and used to enhance performance characteristics of composites. The shell layer, made of thermopolymers unfilled or filled with minerals or nature fibers and other additives, plays a critical role in enhancing overall composite properties. The co-extrusion technology for different structural and material combinations are, however, needed to achieve desired processing. In this paper, co-extrusion technology and core-shell structure NFPC have been discussed by systematically studying the effect of structure on properties of NFPC. The result of this paper can help provide a fundamental base for developing new functional applications of core-shell structure NFPCs.
497
Authors: Yuliya V. Yermolayeva, Yuriy N. Savin, Alexander V. Tolmachev
Abstract: The “islands” of ZnO nanocrystals on amorphous monodisperse 200 nm SiO2 spheres (core-shell particles) were obtained by simple one-step technique based on low-temperature crystallization from liquid phase. The influence of starting reagents types and concentration of zinc ions in the reaction mixture on the morphology of ZnO shells obtained was studied. Crystalline structure of ZnO nanocrystals obtained was proofed by the X-ray diffraction data. The average diameter of ZnO nanocrystals on SiO2 spheres is 10 nm according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) data. It was shown that SiO2/ZnO particles obtained have high luminescence characteristics. Photoluminescence spectra of core-shell SiO2/ZnO particles show two emission peaks centred at 386 nm and 570 nm. Core-shell SiO2/ZnO particles obtained are perspective for active photonic crystals creation for UV-spectral region.
264
Authors: Xi Chang Wang, Xin Li
Abstract: The electromagnetic nanocomposites with a core-shell structure are synthesized by in situ chemical oxidative polymerization. The Co doped Fe3O4 magnetic particles (Co-Fe3O4) act as the core and poly (3,4-ethylenedioxythiophene)-poly (sodium-p-styrenesulfonate) (PEDOT-PSS) as the conductive polymer shells. The morphology, structure, crystallinity, conductive and magnetic properties were studied by transmission electron microscopy (TEM), Scanning electron Microscope (SEM), Fourier Transform Infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), four-probe conductivity meter and vibrating sample magnetometer (VSM). It is found that the core-shell nanocomposites exhibit controllable electromagnetic properties by adjusting the molar ratio of Co-Fe3O4 to EDOT monomer.
607
Authors: Kei Ameyama, Hiroshi Fujiwara
Abstract: Conventional material developments have emphasized ultrafine grain refinement and homogenization. However, “nano- and homo-” materials do not usually satisfy the need to be both strong but ductile, which are of course rather contradictory characteristics. To solve such a problem, we have succeeded in designing a “Harmonic Structure Material” that is both a “nano- and harmonic” material which has overcome that antinomy through use of one of the non-equilibrium powder metallurgy (PM) processes called the severe plastic deformation (SPD) PM process. In the present study, pure Ti, Ti-6Al-4V alloy and SUS316L stainless steel powders are subjected to mechanical milling (MM) for various periods of time. The MM powders have two kinds of microstructure, which can be controlled by the MM conditions. They include ultra fine and coarse grain structures known as “shell” and “core”, respectively. Subsequently, these MM powders are sintered using conventional sintering processes. The sintered materials with the shell and the core have a network structure of continuously connected shells, which we refer to as a harmonic structure. The sintered materials with the harmonic structure simultaneously demonstrate both high strength and elongation. These outstanding mechanical properties are influenced by harmonic structure characteristics such as shell and core grain sizes, shell area fraction and shell network size. Thus, the harmonic structure can be considered as a remarkable design for improving the mechanical properties of materials
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