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Effect of Oxide Dispersion on Dendritic Grain Growth Characteristics of Cast Aluminum Alloy
Kim, Gwang-Ho,Hong, Sung-Mo,Lee, Min-Ku,Kim, Soon-Ho,Ioka, Ikuo,Kim, Byoung-Suhk,Kim, Ick-Soo The Japan Institute of Metals 2010 Materials transactions Vol.51 No.10
<P>The dispersion characteristics of the nano-sized Y<SUB>2</SUB>O<SUB>3</SUB> powders in molten aluminum were investigated from the viewpoint of changes in microstructure and mechanical property as a function of oxide contents. As the solidification structure, the oxide nanoparticles dispersed in the columnar crystal was mainly segregated on the grain boundary, whereas the oxide nanoparticles dispersed in the equiaxed crystal was uniformly dispersed on both grain boundary and inside the crystal. The most uniform dispersion of oxide nanoparticles was observed at Y<SUB>2</SUB>O<SUB>3</SUB> content of 2 mass%. As Y<SUB>2</SUB>O<SUB>3</SUB> content of 3 mass%, the size of oxide nanoparticles in metal matrix increased due to the particle aggregation, as confirmed by SEM analysis. Moreover, it was found that the mechanical properties such as hardness and tensile strength were improved at Y<SUB>2</SUB>O<SUB>3</SUB> content of 2 mass%, indicating the well-dispersion of nano-sized Y<SUB>2</SUB>O<SUB>3</SUB> powders in cast aluminum. The hardness was increased by 1.2 times up to 57 <I>H</I><SUB>V</SUB> and tensile strength was increased by 1.55 times up to 80 MPa, compared with the case of pure aluminum. However, at Y<SUB>2</SUB>O<SUB>3</SUB> content of 3.0 mass%, tensile strength was sharply decreased by 0.6 times due to aggregation of oxide nanoparticles, while the hardness was increased to 57 <I>H</I><SUB>V</SUB>, which is the same as the case of Y<SUB>2</SUB>O<SUB>3</SUB> content of 2.0 mass%.</P>
Kim, Wan-Jin,Ko, Tae Hoon,Seo, Min-Kang,Chung, Yong-Sik,Kim, Hak-Yong,Kim, Byoung-Suhk THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.59 No.-
<P><B>Abstract</B></P> <P>A binder-free electrode for flexible supercapacitor applications was fabricated using carbon fiber papers (CFPs) via a facile paper making method. CV curves and galvanostatic charge/discharge profiles exhibited ideal capacitive behavior and linear voltage–time function with small <I>IR</I> drop. O<SUB>2</SUB> activation process greatly affected the porosity and surface structures. The CFP electrodes activated at 325°C for 45min by O<SUB>2</SUB> oxidizing gas showed highest specific capacitance of 156.9Fg<SUP>−1</SUP> and excellent cycle stability (∼90.2%) after 5000 cycles at 1.0Ag<SUP>−1</SUP> in 1.0M H<SUB>2</SUB>SO<SUB>4</SUB>, which presented the possibilities as flexible electrodes with excellent electrochemical performances for EDLCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Core/shell structured flexible carbon fiber paper electrodes are prepared. </LI> <LI> The O<SUB>2</SUB> activation effects of the core/shell strucuted carbon fibers is studied. </LI> <LI> It delivers the highest specific capacitance of 156.9Fg<SUP>−1</SUP>. </LI> <LI> It shows the excellent cyclic stability with retention of 90.2% after 5000 cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Polyelectrolyte Multilayer Microcapsules: Self-Assembly and Toward Biomedical Applications
Kim, Byoung-Suhk,Choi, Jeong-Woo Korean Society for Biotechnology and Bioengineerin 2007 Biotechnology and Bioprocess Engineering Vol.12 No.4
Over the past few years, many studies have been performed involving the application of the Layer-by-Layer (LbL) deposition of oppositely charged polyelectrolytes onto charged colloidal particles, followed by the dissolution of the templates, ultimately resulting in polyelectrolyte multilayer microcapsules. The ease of preparation of polyelectrolyte multilayer microcapsules afforded by the LbL self-assembly technique, as well as the advantages of accurate control over size, composition, and the thickness of the multilayer shell make these capsules very promising for a number of applications in materials and biomedical science. In this review, we describe the assembly and stimuli-responsive properties ("smart" capsules) of polyelectrolyte multilayer microcapsules, and also discuss the potential of this technique in regard to biomedical applications. In addition, we illustrate two measurement techniques for determining the mechanical properties of polyelectrolyte multilayer microcapsules-(i) osmotic swelling and (ii) AFM compression experiments. These capsules are believed to have great potential for future applications, including biosensors, bioreactors, and carriers for targeted drug delivery.
Kim, Kwan-Woo,Kim, Dong-Kyu,Kim, Byoung-Suhk,An, Kay-Hyeok,Park, Soo-Jin,Rhee, Kyong Yop,Kim, Byung-Joo Elsevier 2017 Composites Part B, Engineering Vol.112 No.-
<P><B>Abstract</B></P> <P>In this work, the composition effects of a nylon6 and epoxy blend system on the cure behaviors and mechanical properties of carbon fiber-reinforced nylon6/epoxy composites were investigated. Ethanol was used as a melting agent for nylon6 (alcohol-soluble nylon), and the content of nylon6 in the mixture was 0–50 wt%. The curing properties of the blend system were investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and fourier transform infrared spectroscopy (FT-IR). The surface morphologies of the fractured surfaces were observed by scanning electron microscopy (SEM). The mechanical properties of the composites were measured with the Charpy pendulum impact test to observe the cumulative energy absorption until final destruction of the composites. The Charpy energy of the N4:E6 sample was enhanced by 52% compared to that of the pure epoxy. This resulted from the curing relation between the composition of nylon6 and epoxy.</P>
Preparation and thermal properties of polyethylene-based carbonized fibers
Kwan-Woo Kim,Hye-min Lee,Byoung Suhk Kim,Seon-Hwan Hwang,Lee-Ku Kwac,Kay-Hyeok An,Byung-Joo Kim 한국탄소학회 2015 Carbon Letters Vol.16 No.1
In this study, carbonized fibers were prepared by using acidically cross-linked LDPE fibers. The surface morphologies of the carbonized fibers were observed by SEM. The effects of cross-linking process temperatures were studied using thermal analyses such as DSC and TGA. The melting and heating enthalpy of the fibers decreased as the cross-linking temperature increased. The cross-linked fibers had a carbonization yield of over 50%. From SEM results the highest yield of carbonized LDPE-based fibers was obtained by cross-linking at a sulfate temperature (170oC). As a result, carbonation yield of the carbonized fibers was found to depend on the functions of the cross-linking ratio of the LDPE precursors.
Kwan-Woo Kim,Byoung Suhk Kim,Sang Won Lee,Dong Chul Chung,Byung-Joo Kim 한국탄소학회 2017 Carbon Letters Vol.23 No.-
Carbon materials with at least one dimension of 1?100 nm are called carbon nanomaterials. A significant body of previous research in physics, chemistry and biology has demonstrated that the properties of nano-composites are significantly different than those of the bulk materials [1]. Some unique phenomena, such as the quantum tunneling effect, and surface effects, have also been observed, and attributed to the large surface area and small size of the carbon nanomaterials. It has been reported that such nanomaterials exhibit high temperature sensitivity, high ductility, large surface area, high strain resistance, and low electrical resistivity [2]. Because of these unique features, the potential range of carbon nanomaterial applications is very extensive.
Effects of cross-linking methods for polyethylene-based carbon fibers: review
Kwan-Woo Kim,Hye-Min Lee,Jeong-Hun An,Byoung-Suhk Kim,Byung-Gak Min,Shin-Jae Kang,Kay-Hyeok An,Byung-Joo Kim 한국탄소학회 2015 Carbon Letters Vol.16 No.3
In recent decades, there has been an increasing interest in the use of carbon fiber reinforced plastic (CFRP) in aerospace, renewable energy and other industries, due to its low weight and relatively good mechanical properties compared with traditional metals. However, due to the high cost of petroleum-based precursors and their associated processing costs, CF remains a specialty product and as such has been limited to use in high-end aerospace, sporting goods, automotive, and specialist industrial applications. The high cost of CF is a problem in various applications and the use of CFRP has been impeded by the high cost of CF in various applications. This paper presents an overview of research related to the fabrication of low cost CF using polyethylene (PE) control technology, and identifies areas requiring additional research and development. It critically reviews the results of cross-linked PE control technology studies, and the development of promising control technologies, including acid, peroxide, radiation and silane cross-linking methods.
유럽의 유전자변형체 관리규정 : Directive 2001/18/EC를 중심으로
김성환,김나영,박미아,김명희,송석린,임병순 중부대학교 자연과학연구소 2001 自然科學硏究論文集 Vol.10 No.1
Foods derived from Genetically Modified Organisms(GMOs) is the most import issue in the world. To establish safety regulation on foods derived from GMOs, it is needed to review various regulation. So this articles is to summarize the European legislation on GMOs. The objectives of Directive 2001/18/EC is to protect human health and the environment when placing on the market GMOs as or in products within the Community. There are various definition of terms used, such as GMO and environmental risk assessment. In this Directive, 'GMO' means an organism, with the exception of human beings, in which the genetic materials has been altered in a way that does not occur naturally by mating or natural recombination. Principles for the environment risk assessment, information required in the notification and monitoring plan also described in this Directive. Notifier who wants to market GMO shall submit notification to the competent authority according to notification procedure