• Korean Journal of Materials Research
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• v.28 no.11
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• pp.653-658
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• 2018

$ZrO_2$ is a candidate material for hip and knee joint replacements because of its excellent combination of biocompatibility, corrosion resistance and low density. However, the drawback of pure $ZrO_2$ is a low fracture toughness at room temperature. One of the most obvious tactics to cope with this problem is to fabricate a nanostructured composite material. Nanomaterials can be produced with improved mechanical properties(hardness and fracture toughness). The high-frequency induction heated sintering method takes advantage of simultaneously applying induced current and mechanical pressure during sintering. As a result, nanostructured materials can be achieved within very short time. In this study, W and $ZrO_2$ nanopowders are mechanochemically synthesized from $WO_3$ and Zr powders according to the reaction($WO_3+3/2Zr{\rightarrow}W+3/2ZrO_2$). The milled powders are then sintered using high-frequency induction heating within two minutes under the uniaxial pressure of 80MPa. The average fracture toughness and hardness of the nanostructured W-3/2 $ZrO_2$ composite sintered at $1300^{\circ}C$ are $540kg/mm^2$ and $5MPa{\cdot}m^{1/2}$, respectively. The fracture toughness of the composite is higher than that of monolithic $ZrO_2$. The phase and microstructure of the composite is also investigated by XRD and FE-SEM.

• Carbon letters
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• v.10 no.1
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• pp.14-18
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• 2009

We measured the degree of macrodispersion of the various single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) using UV-VIS-NIR absorption spectroscopy. CNTs were dispersed with SDS of 2 wt % in deionized water using the homogenizer and then were further centrifugated at 6000 g for 10 min. The degree of macrodispersion, expressed by $D_m({\lambda})=A_a({\lambda})/A_b({\lambda})^*100$ (%), where ${\lambda}$ is the wavelength and $A_a({\lambda})$ and $A_b({\lambda})$ are the absorbance of the sample after and before centrifugation, respectively. In the case of MWCNTs, we evaluated the degree of macrodispersion by the average degree of macrodispersion ($D_m({\lambda})$) between 1000 and 1200 nm. The degree of macrodispersion of SWCNTs was evaluated at the wavelength in which van Hove singularity-related transition regions were excluded, i.e., the range was chosen between ${E_{11}}^S$ and ${E_{22}}^S$ peaks. We have estimated six samples with the same method. The standard deviation of each sample was lower than 5. Therefore, we presented a reliable evaluation method for the macrodispersion of CNTs for standardization.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.59-59
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• 2010

Graphene is a 2-D sheet of $sp^2$-bonded carbon arranged in a honeycomb lattice. This material has attracted major interest, and there are many ongoing efforts in developing graphene devices because of its high charge mobility and crystal quality. Therefore clear understanding of the substrate effect and mechanism of synthesis of graphene is important for potential applications and device fabrication of graphene. In a published paper in J. Phys. Chem. C (2008), the effect of substrate on the atomic/electronic structures of graphene is negligible for graphene made by mechanical cleavage. However, nobody shows the interaction between Ni substrate and graphene. Therefore, we have studied this interaction. In order to studying these effect between graphene and Ni substrate, We have observed graphene synthesized on Ni substrate and graphene transferred on $SiO_2$/Si substrate through Raman spectroscopy. Because Raman spectroscopy has historically been used to probe structural and electronic characteristics of graphite materials, providing useful information on the defects (D-band), in-plane vibration of sp2 carbon atoms (G-band), as well as the stacking orders (2D-band), we selected this as analysis tool. In our study, we could not observe the doping effect between graphene and Ni substrate or between graphene and $SiO_2$/Si substrate because the shift of G band in Raman spectrum was not occurred by charge transfer. We could noticed that the bonding force between graphene and Ni substrate is more strong than Van de Waals force which is the interaction between graphene and $SiO_2$/Si. Furthermore, the synthesized graphene on Ni substrate was in compressive strain. This phenomenon was observed by 2D band blue-shift in Raman spectrum. And, we consider that the graphene is incommensurate growth with Ni polycrystalline substrate.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.95-107
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• 2018

This presentation will give an overview of Ca-aluminate based biomaterials and their proposed use within the field of nanostructured biomaterials. The paper describes typical features of Ca-aluminate materials with regard to technology, chemistry, biocompatibility including hemocompatibility and bioactivity, and developed microstructure. Special focus will be on the developed microstructure, which is in the nanosize range. Application possibilities within odontology, orthopedics, and drug delivery are presented. The nanostructure including pore size below 5 nm in these structures opens up this material for some use in specific dental-related applications in which antibacterial and bacteriostatic aspects are of importance, and as thin coating on implants within dental and orthopaedic applications. Nanosize porosity is essential in drug delivery systems for controlled release of medicaments. The priority field for Ca-aluminate biomaterials is implant materials, which use minimally-invasive techniques to offer in vivo, on-site developed biomaterials.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.3977-3980
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• 2012

Nanostructured thermoelectric bismuth telluride ($Bi_2Te_3$) powders with various morphologies, such as nanoplates, nanorods, and nanotubes, were prepared by a hydrothermal method based on the reaction between $BiCl_3$, Te, and sodium ethylenediaminetetraacetate ($Na_2$-EDTA) at 150, 180, and $210^{\circ}C$. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). The effect of reaction temperature on the morphology of the $Bi_2Te_3$ particles was investigated, and the possible mechanism of morphology control was proposed.

• Advances in nano research
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• v.1 no.3
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• pp.153-158
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• 2013

An approach to achieving of spatially homogeneous, ordered ensemble of semiconductor quantum rods in polymer film of polyvinyl butyral is reported. The CdSe/ZnS quantum rods are embedded to the polymer film. Obtained film is stretched up to four times to its initial length. A concentration of quantum rods in the samples is around $2{\times}10^{-5}$ M. The absorption spectra, obtained in the light with orthogonal polarization, confirm the occurrence of spatial ordering in a quantum rod ensemble. Anisotropy of the optical properties in the ordered quantum rod ensemble is examined. The presented method can be used as a low-cost solution for preparing the nanostructured materials with anisotropic properties and high concentration of nanocrystals.

• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.22-26
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• 2003

This short communication reports on the experiment which demonstrates that superhard nanostructured films with hardness of about 40 GPa and greater can be composed not only of two or more nanocrystalline and/or amorphous phases of different materials, as it is in the case of nanocomposite coatings, but also that can be formed by a mixture of small (<10 nm) nanocrystalline grains of the same material with different crystallographic orientation and/or lattice structures. This finding opens new possibilities to develop advanced nanostructured materials with enhanced physical and functional properties.

• Journal of the Korean Ceramic Society
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• v.56 no.5
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• pp.497-505
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• 2019

Lanthanum-based transition metal cations containing perovskites have emerged as potential catalysts for the intermediate-temperature (600-800℃) oxygen reduction reaction (ORR). Here, we report a facile acetylacetone-assisted combustion route for the synthesis of nanostructured La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF6428) cathodes for intermediate-temperature solid-oxide fuel cells (IT-SOFCs). The as-prepared powder was analyzed by thermogravimetry analysis-differential scanning calorimetry. The powder calcined at 800℃ was characterized by X-ray diffraction, scanning electrode microscopy, energy dispersive X-ray spectroscopy, and Brunauer-Emmett-Teller surface area measurements. It was found that the porosity of the air electrode significantly increased by utilizing the nanostructured LSCF6428 instead of commercial powder. The performance of a single cell fabricated with the nanostructured LSCF6428 cathode increased by 112%, from 0.4 to 0.85 W cm^-2, at 700℃. Electrochemical impedance spectroscopy showed a considerable reduction in the area-specific resistance and activation energy from 133.5 to 61.5 kJ/mol, resulting in enhanced electrocatalytic activity toward ORR and overall cell performance.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.75-75
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• 2012

This presentation will focus on computational materials research carried out across length scales. Examples will be presented that illustrate the way in which state-of-the-art quantum mechanical calculations and atomistic simulations can be applied to explain experimental data, design new structures, determine mechanisms, and enable new investigations. In particular, the presentation will present key findings from an integrated experimental and computational investigation of the tribological properties of polytetrafluoroethylene and its composites and predictions regarding the mechanical and tribological properties of inorganic nanostructured materials.

• Advances in Computational Design
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• v.9 no.1
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• pp.53-71
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• 2024

Owing to these mechanical properties, carbon nanotubes have the potential to be employed in many future devices and nanostructured materials. As an example, high Young modulus accompanied by their low density, makes them a good choice for reinforcing material in composites. Therefore, we empathize and manually derive the results which shows the utilized lemma and criterion are believed effective and efficient for aircraft structural analysis of composite and nonlinear scenarios. To be fair, the experiment by numerical computation and calculations were explained the perfectness of the methodology we provided in the research.