• Journal of Powder Materials
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• v.24 no.4
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• pp.279-284
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• 2017

The formation mechanism and photocatalytic properties of a multiwalled carbon nanotube (MWCNT)/$TiO_2$-based nanotube (TNTs) composite are investigated. The CNT/TNT composite is synthesized via a solution chemical route. It is confirmed that this 1-D nanotube composite has a core-shell nanotubular structure, where the TNT surrounds the CNT core. The photocatalytic activity investigated based on the methylene blue degradation test is superior to that of with pure TNT. The CNTs play two important roles in enhancing the photocatalytic activity. One is to act as a template to form the core-shell structure while titanate nanosheets are converted into nanotubes. The other is to act as an electron reservoir that facilitates charge separation and electron transfer from the TNT, thus decreasing the electron-hole recombination efficiency.

• Current Photovoltaic Research
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• v.4 no.4
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• pp.140-144
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• 2016

In this paper, core-shell structure of nickel/gold (Ni/Au) conductive layer on poly-methyl-methacrylate (PMMA) micro-ball was fabricated and its conduction property was investigated. Firstly, PMMA micro-ball was synthesized by using dispersion polymerization method. Size of the ball was $2.8{\mu}m$ within ${\pm}7%$ deviation, and appropriate elastic deformation of the PMMA micro-ball ranging from 31 to 39% was achieved under 3 kg pressure. Also, 200 nm thick Ni/Au conductive layer was fabricated on the PMMA micro-ball by uniformly depositing with electroless-plating. Adhesion of the conductive layer was optimized with help of surface pre-treatment, and the layer adhered without peeling-off despite of thermal expansion by collision with accelerated electrons. Composite paste containing core-shell structured particles well cured at low temperature of $130^{\circ}C$ while pressing the test chip onto the substrate to make electrical contact, and electrical resistance of the conductive layer showed stable behavior of about $6.0{\Omega}$. Thus, it was known that core-shell structured particle of the Ni/Au conductive layer on PMMA micro-ball was feasible to flexible electronics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.392-397
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• 2022

We present the structural and optical properties of Au@TiO₂ core-shell microsphere structure prepared by a hydrothermal synthesis method. As a way to improve the efficiency of organic solar cells, the Au@TiO₂ core-shell microsphere was synthesized to use the local surface plasmon resonance (LSPR) phenomenon. The synthesized results were confirmed to have the Au@TiO₂ core-shell structure using a high-resolution transmission electron microscopy. An absorption was observed to occur at 527 nm belonging to the visible light region using a visible light spectroscopy, which supports the LSPR phenomenon. We suggest that the Au@TiO₂ core-shell microsphere is highly likely to be applied to organic solar cells including dye-sensitized solar cells. In addition, we expect it to be widely used not only in the energy but also in the bio as well as in the environmental fields.

• Journal of Surface Science and Engineering
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• v.56 no.1
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• pp.104-114
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• 2023

Three dimensional (3D) porous structures consisting of Cu@CoO core-shell-type nano-dendrites were synthesized and tested as the anode materials in lithium secondary batteries. For this purpose, first, the 3D porous films comprising Cu@Co core-shell-type nano-dendrites with various thicknesses were fabricated through the electrochemical co-deposition of Cu and Co. Then the Co shells were selectively anodized to form Co hydroxides, which was finally dehydrated to get Cu@CoO nanodendrites. The resulting electrodes exhibited very high reversible specific capacity almost 1.4~2.4 times the theoretical capacity of commercial graphite, and excellent capacity retention (~90%@50^th cycle) as compared with those of the existing transition metal oxides. From the analysis of the cumulative irreversible capacity and morphology change during charge/discharge cycling, it proved that the excellent capacity retention was attributed to the unique structural feature of our core-shell structure where only the thin CoO shell participates in the lithium storage. In addition, our electrodes showed a superb rate performance (70.5%@10.8 C-rate), most likely due to the open porous structure of 3D films, large surface area thanks to the dendritic structure, and fast electron transport through Cu core network.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2683-2688
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• 2011

Silica-manganese oxides with a core-shell structure were synthesized via precipitation of manganese oxides on the $SiO_2$ core while varying the concentration of a precipitation agent. Elemental analysis, crystalline property investigation, and morphology observations using low- and high-resolution electron microscopes were applied to the synthesized silica-manganese oxides with the core-shell structure. As the concentration of the precipitating agent increased, the manganese oxide shells around the $SiO_2$ core sequentially appeared as $Mn_3O_4$ particles, $Mn_2O_3+Mn_3O_4$ thin layers, and ${\alpha}-MnO_2$ urchin-like phases. The prepared samples were assembled as electrodes in a supercapacitor with 0.1 M $Na_2SO_4$ electrolyte, and their electrochemical properties were examined using cyclic voltammetry and charge-discharge cycling. The maximum specific capacitance obtained was 197 F $g^{-1}$ for the $SiO_2-MnO_2$ electrode due to the higher electronic conductivity of the $MnO_2$ shell compared to those of the $Mn_2O_3$ and $Mn_3O_4$ phases.

• Journal of Adhesion and Interface
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• v.12 no.1
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• pp.16-25
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• 2011

Multi core-shell composite particles were prepared by the water-born emulsion polymerization of various core monomer such as methyl methacrylate (MMA), n-butyl methacrylate (BMA), and shell monomer such as MMA, BMA, stylene (St), 2-hydroxyl ethyl methacrylate (2-HEMA) and acrylic acid (AA) in the presence of different concentration of sodium dodecyl benzene sulfonate (SDBS). The following conclusions are drawn from the measured conversion, particle size and distribution, average molecular weight, molecular structure, glass transition temperature with DSC, morphology, tensile strength and elongation. In the case of the concentration of 0.02 wt% SDBS, the conversion of MMA core-(BMA/St/AA) shell composite particle was excellent as 98%. In the case of the concentration of 0.03 wt% SDBS, the particle size of BMA core-(MMA/St/AA) shell composite particle was high as $0.47{\mu}m$. We confirmed that 3 points of glass transition temperatures appear for multi core-shell composite particles compared to 2 points of glass transition temperatures appear for general core-shell composite particles. We showed that it is possible to adjust glass transition temperatures according to the kind and composition of the inner shell monomer that it is can be used as a adhesive binder material with improved adhesive power.

• Korean Journal of Metals and Materials
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• v.48 no.5
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• pp.445-448
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• 2010

For an enhanced thermoelectric performance, one-dimensional heterostructure nanowires were created that consisted of aBi core and Te shell. The structure was fabricated by depositing Te in-situ onto a Bi nanowire grown by our unique OFF-ON (on-film formation of nanowires) method. After examining a cross-sectional TEM image, it was found that diffusive interface was formed between Bi and Te. Selected area electron diffraction revealed that the crystallinity of the Te shell was some what lower compared to the highly single-crystalline Bi core. The Bi-Te core/shell nanowires can be a smart structure that suppresses phonon transport by several scattering mechanisms, making the OFF-ON method the simplest way to realize that structure.

• Journal of Adhesion and Interface
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• v.14 no.1
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• pp.1-12
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• 2013

Multi core-shell composite particles were prepared by the water-born emulsion polymerization of various core monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA) and shell monomers such as MMA, EMA, 2-hydroxyl ethyl methacrylate (2-HEMA), glycidyl methacrylate (GMA) and methacrylic acid (MAA) in the presence of different concentrations of sodium dodecyl benzene sulfonate (SDBS). The following conclusions are drawn from the conversion, particle size and distribution, average molecular weight, molecular structure, glass transition temperature with DSC, contact angle after plasma treatment, tensile strength and isothermal decomposition kinetics. In the case of the concentration of 0.02 wt% SDBS, the conversion of MMA core-(EMA/GMA) shell composite particles was excellent as 98.5%. In the case of the concentration of 0.03 wt% SDBS, the particle size of EMA core-(MMA/GMA) shell composite particles was high as $0.48{\mu}m$. We confirmed that 3 points of glass transition temperatures appear for multi core-shell composite particles compared to 1~2 points of glass transition temperatures appear for general copolymer particles. Overall, the adhesion strength of shell composite particles was in the order of EMA/MAA > EMA/2-HEMA > EMA/GMA.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.447-453
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• 2011

The monodisperse spherical $SiO_2$ particles were overcoated with $Y_2O_3:Eu^{3+}$ phosphor layers via a Pechini sol-gel process and the resulting $SiO_2@Y_2O_3:Eu^{3+}$ core-shell phosphors were subsequently annealed at $800^{\circ}C$ at an ambient atmosphere. The crystallographic structure, morphology, and luminescent property of core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL). The spherical, nonagglomerated $SiO_2$ particles prepared by a Stober method exhibited a relatively narrow size distribution in the range of 260-300 nm. The thickness of phosphor shell layer in the core-shell particles can be facilely controlled by varying the coating number of $Y_2O_3:Eu^{3+}$ phosphors. The core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors showed a strong red emission, which was dominated by the $^5D_0-^7F_2$ transition (610 nm) of $Eu^{3+}$ ion under the ultraviolet excitation (263 nm). The PL emission properties of $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were also compared with pure $Y_2O_3:Eu^{3+}$ nanophosphors.

• Advances in environmental research
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• v.4 no.2
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• pp.69-81
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• 2015

A new magnetite-silica core/shell nanocomposite ($Fe_3O4@nSiO_2@mSiO_2$) was synthesized and functionalized with trimethylchlorosilane (TMCS). The prepared nanocomposite was used for the removal of diesel oil from aqueous media. The characterization of magnetite-silica nanocomposite was studied by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), surface area measurement, and vibrating sample magnetization (VSM). Results have shown that the desired structure was obtained and surface modification was successfully carried out. FTIR analysis has confirmed the presence of TMCS on the surface of magnetite silica nanocomposites. The low- angle XRD pattern of nanocomposites indicated the mesoscopic structure of silica shell. Furthermore, TEM results have shown the core/shell structure with porous silica shell. Adsorption kinetic studies indicated that the nanocomposite was able to remove 80% of the oil contaminant during 2 h and fit well with the pseudo-second order model. Equilibrium studies at room temperature showed that the experimental data fitted well with Freundlich isotherm. The magnetic property of nanocomposite facilitated the separation of solid phase from aqueous solution.