• Journal of the Korean Electrochemical Society
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• v.22 no.4
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• pp.172-176
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• 2019

The first commercialized cathode material, $LiCoO_2$, suffers from disadvantages such as high cost and toxicity and also possesses safety problems. The nickel-rich $LiNi_{0.9}Mn_{0.1}O_2$ cathode material, used as an alternative to $LiCoO_2$, has highly reversible capacity and high energy density. So, the nickel-rich $LiNi_{0.9}Mn_{0.1}O_2$ cathode material is widely used as an alternative to $LiCoO_2$ due to its highly reversible capacity and high energy density. However, $LiNi_{0.9}Mn_{0.1}O_2$ has several disadvantages as well, such as poor cycle performance and poor thermal instability. To address these problems, we synthesized a new material, $LiNi_{0.5}Mn_{0.5}O_2$, as a shell on the surface of a core to suppress the surface degradation. The new material showed high structural and thermal stabilities and could also maintain a high capacity. The capacity retention of the core-shell cathode (87.7%) was better than that of the core cathode (76.9%) after 50 cycles. Analysis using differential scanning calorimetry revealed that the heat generation in the core-shell cathode ($65.9Jg^{-1}$) was lower than that in the core cathode ($559.7Jg^{-1}$).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.5
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• pp.449-453
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• 2015

Recently, surfaces with micro and nano structures are the focus of various research and engineering fields to enhance wetting characteristics of the surfaces. Hydrophilic surfaces with hierarchical structures are generally characterized by the interfacial behavior of water droplets. In this study, the interfacial behavior of water droplets is experimentally investigated considering the scale of structures. Using the dry etching and conventional lithography method, quantitative hierarchical structured surfaces are developed. The behavior of the liquid-vapor interface on the test sections is visualized using an automatic goniometer and a high-speed camera. On the basis of the visualized data, the interfacial behavior of water droplets is intensively investigated according to surface geometrical characteristics.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.596-601
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• 2009

Double-layered ZnO nanostructures have been synthesized by aqueous solution method on (001) plane of ZnO nanorod. A stepwise changing of aqueous solution concentration gave rise to a new nano-structured layer consisting of either multiple of nanorods or nanowires with much smaller radii than that of the ZnO nanorod on which the new layer was grown. As the first step the ZnO nanorods have been grown to have the (001) preferential orientation in the aqueous solution consisting of 0.1M zinc nitrate and 0.1 M HMT. This preferentially aligned ZnO nanorods have been regrown in either a less diluted solution of 0.01M zinc nitrate and 0.01 M HMT or a more diluted solution of 0.005M zinc nitrate and 0.01 M HMT. A new nano-layer consisting of numerous aligned nanorods or nanowires has been produced on the (001) planes of ZnO nanorods. The growth mechanism for this double layered ZnO nanostructure is ascribed to the (001) polar surface energy instability and inhibition of (001) plane growth due to the step-wise change of aqueous solution concentration; ZnO nuclei formed on the (001) plane grow preferentially in (010) plane instead of (001) plane to reduce the total surface energy. Surface area of ZnO nanostructure can be increased in orders of magnitudes by forming a new layer consisting of smaller nanorods/nanowires on (001) plane of ZnO nanorods.

• Composites Research
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• v.34 no.4
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• pp.264-268
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• 2021

In this study, we propose a method for fabricating hydrophobic coatings/films with three-dimensional (3D) hierarchical nanostructured organic/inorganic composite surfaces. An epoxy-based, large-area 3D ordered nanoporous template is first prepared through an advanced photolithography technique called Proximity-field nanoPatterning (PnP). Then, a hierarchically structured surface is generated by densely impregnating the template with silica nanoparticles with an average diameter of 22 nm through dip coating. Due to the coexisting micro- and nano-scale roughness on the surface, the fabricated composite film exhibits a higher contact angle (>137 degrees) for water droplets compared to the reference samples. Therefore, it is expected that the materials and processes developed through this study can be used in various ways in the traditional coating/film field.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.21-27
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• 2011

A nano-porous structure of tin oxide was prepared using an anodic oxidation process and the sample's electrochemical properties were evaluated for application as an anode in a rechargeable lithium battery. Microscopic images of the as-anodized sample indicated that it has a nano-porous structure with an average pore size of several tens of nanometers and a pore wall size of about 10 nanometers; the structural/compositional analyses proved that it is amorphous stannous oxide (SnO). The powder form of the as-anodized specimen was satisfactorily lithiated and delithiated as the anode in a lithium battery. Furthermore, it showed high initial reversible capacity and superior rate performance when compared to previous fabrication attempts. Its excellent electrode performance is probably due to the effective alleviation of strain arising from a cycling-induced large volume change and the short diffusion length of lithium through the nano-structured sample. To further enhance the rate performance, the attempt was made to create porous tin oxide film on copper substrate by anodizing the electrodeposited tin. Nevertheless, the full anodization of tin film on a copper substrate led to the mechanical disintegration of the anodic tin oxide, due most likely to the vigorous gas evolution and the surface oxidation of copper substrate. The adhesion of anodic tin oxide to the substrate, together with the initial reversibility and cycling stability, needs to be further improved for its application to high-power electrode materials in lithium batteries.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.973-976
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• 2004

The results of numerous studies in III-V semiconductors show that sulfur treatment improves the electrical parameters of III-V compound devices. In this article, we examine the effects of sulfidation of HgCdTe surface on the interfacial characteristics of metal-ZnS-HgCdTe structures. Different from sulfidation in III-V material, S can not be act as an impurity because II-S compounds (ZnS, CdS) generally used as passivant for HgCdTe. Our studies of sulfur-treatment on HgCdTe surface show that sulfur agent forms the S- S, II-S bonds at the surface layer. These bonds are very effective to improve the electrical properties of ZnS layer on HgCdTe by reducing the possibility of native oxides formation. After the sulfidation process, MIS capacitors of HgCdTe show great improvement in electrical properties, such as low density of fixed charge and reduced hystereisis width.

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.585-591
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• 2018

Characteristics of nano-structured $SiO_2:Zn$ hollow powders prepared in the micro drop fluidized reactor process were investigated with respect to bandgap energy and surface activity. The $SiO_2:Zn$ hollow powders were successfully prepared continuously in the one step process with reasonable production efficiency, with varying the amount of THAM (tris(hydroxymethyl)-aminomethane) additive and concentration of $Zn^{2+}$ ions. The doping of $Zn^{2+}$ ions into $SiO_2$ lattice led to the reduction of bandgap energy by forming the acceptor level of $Zn^{2+}$ below the conduction band of $Si^{4+}$ ions. The hollow shape also contributed to reduce the bandgap energy of $SiO_2:Zn$ powders. The doping of $Zn^{2+}$ ions into $SiO_2$ hollow powders could enhance the surface activity by forming SiO-H stretching and oxygen vacancies at the surface of $SiO_2:Zn$ powders.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.97-97
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• 2013

The exterior structures of natural organisms have continuously evolved by controlling wettability, such as the Namib Desert beetle, whose back has hydrophilic/hydrophobic contrast for water harvesting by mist condensation in dry desert environments, and some plant leaves that have hierarchical micro/nanostructures to collect or repel liquid water. In this work, we have provided a method for wettability contrast on metals by both nano-flake or needle patterns and tuning of the surface energy. Metals including steel alloys and aluminum were provided with hierarchical micro/nanostructures of metaloxides induced by fluorination and a subsequent catalytic reaction of fluorine ions on metal surfaces in water with various ranges from room to boiling temperature of water. Then, a hydrophobic material was deposited on the structured surfaces, rendering superhydrophobicity. Plasma oxidization induces the formation of superhydrophilic surfaces on selective regions surrounded by superhydrophobic surfaces. We show that wettability contrast surfaces align liquid water within patterned hydrophilic regions during the condensation process. Furthermore, this method could have a greater potential to align other liquids or living cells.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.5
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• pp.105-109
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• 2022

In the field of medical and marine industries, antibacterial surfaces have been emerged as one of the most important issues. Recently, many researchers have been studying antibacterial surfaces to kill bacteria or prevent the adhesion of bacteria. In their researches, various materials and structures are suggested to inhibit the adhesion of bacteria or kill the attached bacteria. However, chemical materials such as antibiotics or metal could be toxic. Moreover, frequent use of antibiotics causes super bacteria having resistance to antibiotics. In this study, nano-pillar structured surface was fabricated using polyurethane acrylate (PUA) and the mechanically induced antibacterial function was confirmed based on the fabricated nanostructures. Nanostructures can damage the bacterial membrane of Gram-negative bacteria through stretching of bacterial membrane via interaction with the nanostructures and the bacterial membrane. Consequently, the proposed transparent, flexible and nanostructured PUA films can be one of promising candidates for antifouling and antibacterial surfaces which can be applied in various industries.

• BMB Reports
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• v.41 no.9
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• pp.640-644
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• 2008

The preS1 surface protein of the hepatitis B virus (HBV) is a key factor involved in initial viral entry into hepatocytes. It has been long postulated that an anti-HBV effect should be achievable using peptide fragments of the preS1. Recent reports demonstrated that several preS1-derived lipo-peptides in genotype D HBV exhibit nano to picomolar inhibitory activity against HBV infection. In this study, an acylated analog of a preS1 fragment, a 21-residue lipo-peptide (named 7524 BVS7) with a sequence of palmitoyl-GMGTNLSVPNPLGFFPDHQLDC-$NH_2$, from genotype C HBV was produced base upon a previous structural study and was shown potently inhibits HBV infection with an $IC_{50}$ of $\approx$ 20 nM.