• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.412-412
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• 2009

Carbon-based nano materials have a significant effect on various fields such as physics, chemistry and material science. Therefore carbon nano materials have been investigated by many scientists and engineers. Especially, since graphene, 2-dimemsonal carbon nanostructure, was experimentally discovered graphene has been tremendously attracted by both theoretical and experimental groups due to their extraordinary electrical, chemical and mechanical properties. Electrical conductivity of graphene is about ten times to that of silicon-based material and independent of temperature. At the same time silicon-based semiconductors encountered to limitation in size reduction, graphene is a strong candidate substituting for silicon-based semiconductor. But there are many limitations on fabricating large-scale graphene sheets (GS) without any defect and controlling chirality of edges. Many scientists applied micromechanical cleavage method from graphite and a SiC decomposition method to the fabrication of GS. However these methods are on the basic stage and have many drawbacks. Thereupon, our group fabricated GS through Thermo-electrical Pulse Induced Evaporation (TPIE) motivated by arc-discharge and field ion microscopy. This method is based on interaction of electrical pulse evaporation and thermal evaporation and is useful to produce not only graphene but also various carbon-based nanostructures with feeble pulse and at low temperature. On fabricating GS procedure, we could recognize distinguishable conditions (electrical pulse, temperature, etc.) to form a variety of carbon nanostructures. In this presentation, we will show the structural properties of OS by synthesized TPIE. Transmission Electron Microscopy (TEM) and Optical Microscopy (OM) observations were performed to view structural characteristics such as crystallinity. Moreover, we confirmed number of layers of GS by Atomic Force Microscopy (AFM) and Raman spectroscopy. Also, we used a probe station, in order to measure the electrical properties such as sheet resistance, resistivity, mobility of OS. We believe our method (TPIE) is a powerful bottom-up approach to synthesize and modify carbon-based nanostructures.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2001년도 창립10주년 제20회 학술발표회
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• pp.25-25
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• 2001

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.111.2-111.2
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• 2010

One-dimensional nanostructures such as carbon nanotubes could be ideal templates for formation of metallic nanoparticles. Furthermore, bimetallic component nanoparticles have recently been interesting issues for having high catalytic activity. This work provides both a facile method to synthesize bimetallic catalysts via N atoms of carbon nanotubes and also a picture about how to design the optimal bimetallic catalyst for hydrogen generation from the hydrogen storage material. In principle, the ratio of one component to another component could be generically extended to fabricate the high-performance bimetallic catalysts on host nanostructures. Indeed, we demonstrate that the bimetallic catalyst composed of the optimum composition results in the excellent hydrogen generation property from an aqueous borane ammonia solution, thus being capable of satisfying the Depart of Energy in USA target required for many advanced applications even with the small amount of our bimetallic catalysts attached onto the N-doped carbon nanotubes. This high hydrogen generation rate is found to be attributed to the optimal distance between active Pt and cheap Ni atoms for effective hydrogen generation.

• Advances in nano research
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• 제16권1호
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• pp.91-109
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• 2024

Carbon nanotubes are drawing wide attention of research communities and several industries due to their versatile capabilities covering mechanical and other multi-physical properties. However, owing to extreme operating conditions of the synthesis process of these nanostructures, they are often imposed with certain inevitable structural deformities such as single vacancy and nanopore defects. These random irregularities limit the intended functionalities of carbon nanotubes severely. In this article, we investigate the mechanical behaviour of double-wall carbon nanotubes (DWCNT) under the influence of arbitrarily distributed single vacancy and nanopore defects in the outer wall, inner wall, and both the walls. Large-scale molecular simulations reveal that the nanopore defects have more detrimental effects on the mechanical behaviour of DWCNTs, while the defects in the inner wall of DWCNTs make the nanostructures more vulnerable to withstand high longitudinal deformation. From a different perspective, to exploit the mechanics of damage for achieving defect-induced shape modulation and region-wise deformation control, we have further explored the localized longitudinal and transverse spatial effects of DWCNT by designing the defects for their regional distribution. The comprehensive numerical results of the present study would lead to the characterization of the critical mechanical properties of DWCNTs under the presence of inevitable intrinsic defects along with the aspect of defect-induced spatial modulation of shapes for prospective applications in a range of nanoelectromechanical systems and devices.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.281-281
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• 2014

The field emission properties of GaN are reported in the present study. To be a good field emitter, it requires a low work function, high aspect ratio, and strong mechanical stability. In the case of GaN, it has a quite low work function (4.1eV) and strong chemical/mechanical/thermal stabilities. However, so far, it was difficult to fabricate vertical GaN nanostructures with a high aspect ratio. In this study, we successfully achieved vertically well aligned GaN nanostructures with chemical vapor-phase etching methods [1] (Fig. 1). In this method, we chemically etched the GaN film using hydrogen chloride and ammonia gases at high temperature around $900^{\circ}C$. This process effectively forms vertical nanostructures without patterning procedure. This favorable shape of GaN nanostructures for electron emitting results in excellent field emission properties such as a low turn-on field and long term stability. In addition, we observed a uniform fluorescence image from a phosphor film attached at the anode part. The turn-on field for the GaN nanostructures is found to be about $0.8V/{\mu}m$ at current density of $20{\mu}A$/cm^2. This value is even lower than that of typical carbon nanotubes ($1V/{\mu}m$). Moreover, threshold field is $1.8V/{\mu}m$ at current density of $1mA$/cm^2. The GaN nanostructures achieved a high current density within a small applied field range. We believe that our chemically etched vertical nanostructures are the promising structures for various field emitting devices.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2613-2618
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• 2012

Hydrothermal route have been used in different conditions for preparation of $Ni(OH)_2$ nanostructures. The NiO nanoparticles were obtained by calcining the $Ni(OH)_2$ precursor at $450^{\circ}C$ for 2 h. The effect of sodium dodecyl sulfonate (SDS) as surfactant on the morphology and size of $Ni(OH)_2$ nanoparticles were discussed in detail. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize the products. The growth mechanism of the as-synthesized nanostructures was also discussed in detail based on the experimental results. Coming up, the NiO nanoparticle modified carbon paste electrode was applied to the determination of captopril in aqueous solution.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.276-276
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• 2013

Time-Of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and Atomic Force Microscopy (AFM) are the useful instruments to measure nanostructures of material surfaces. Surface pattern formation in blending homopolymer and diblock copolymer films was investigated as a function of film thickness and annealing conditions. In this study, surface structures of blending homopolymer [deuterated polystyrene (Mn 20,000), poly (methyl methacrylate) (Mn 18,000)] and diblock copolymer [Poly (deuteratedstyrene(d8)-b-methyl methacrylate) (Mn 19,500-18,100)] films were observed. The AFM result indicated that the nanostructures and film thickness depended on temperature, concentration and solvent. TOF-SIMS depth profiling was obtained for the lamellar morphology of symmetric dPS-b-PMMA which is found to orient parallel to the surface of the substrate. Elemental and molecular depth profiles measured in the negative ion mode by a Cs+ primary ion beam demonstrate variations in hydrogen, deuterium, carbon, oxygen, hydrocarbons and deuterated hydrocarbons within the diblock copolymer according to the depth.

• 한국재료학회지
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• 제26권6호
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• pp.298-305
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• 2016

In this work, recent progress on graphene/metal oxide composites as advanced materials for $HgCl_2$ and $CO_2$ capture was investigated. Density Functional Theory calculations were used to understand the effects of temperature on the adsorption ability of $HgCl_2$ and water vapor on $CO_2$ adsorption on CaO (001) with reinforced carbon-based nanostructures using B3LYP functional. Understanding the mechanism by which mercury and $CO_2$ adsorb on graphene/CaO (g-CaO) is crucial to the design and fabrication of effective capture technologies. The results obtained from the optimized geometries and frequencies of the proposed cluster site structures predicted that with respect to molecular binding the system possesses unusually large $HgCl_2$ ($0.1-0.4HgCl_2g/g$ sorbent) and $CO_2$ ($0.2-0.6CO_2g/g$ sorbent) uptake capacities. The $HgCl_2$ and $CO_2$ were found to be stable on the surface as a result of the topology and a strong interaction with the g-CaO system; these results strongly suggest the potential of CaO-doped carbon materials for $HgCl_2$ and $CO_2$ capture applications, the functional gives reliable answers compared to available experimental data.

• Structural Engineering and Mechanics
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• 제64권3호
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• pp.329-337
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• 2017

This study concerns the vibrational behavior of multi-walled nested silicon-carbide and carbon nanotubes using the finite element method. The beam elements are used to model the carbon-carbon and silicon-carbon bonds. Besides, spring elements are employed to simulate the van der Waals interactions between walls. The effects of nanotube arrangement, number of walls, geometrical parameters and boundary conditions on the frequencies of nested silicon-carbide and carbon nanotubes are investigated. It is shown that the double-walled nanotubes have larger frequencies than triple-walled nanotubes. Besides, replacing silicon carbide layers with carbon layers leads to increasing the frequencies of nested silicon-carbide and carbon nanotubes. Comparing the first ten mode shapes of nested nanotubes, it is observed that the mode shapes of armchair and zigzag nanotubes are almost the same.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.108-109
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• 2012

This talk will begin with the demonstration of facile synthesis of silicon nanostructures using the magnesiothermic reduction on silica nanostructures prepared via self-assembly, which will be followed by the characterization results of their performance for energy storage. This talk will also report the fabrication and characterization of highly porous, stretchable, and conductive polymer nanocomposites embedded with carbon nanotubes (CNTs) for application in flexible lithium-ion batteries. It will be presented that the porous CNT-embedded PDMS nanocomposites are capable of good electrochemical performance with mechanical flexibility, suggesting these nanocomposites could be outstanding anode candidates for use in flexible lithium-ion batteries. Directed self-assembly (DSA) of block copolymers (BCPs) can generate uniform and periodic patterns within guiding templates, and has been one of the promising nanofabrication methodologies for resolving the resolution limit of optical lithography. BCP self-assembly processing is scalable and of low cost, and is well-suited for integration with existing semiconductor manufacturing techniques. This talk will introduce recent research results (of my research group) on the self-assembly of Si-containing block copolymers for the achievement of sub-10 nm resolution, fast pattern generation, transfer-printing capability onto nonplanar substrates, and device applications for nonvolatile memories. An extraordinarily facile nanofabrication approach that enables sub-10 nm resolutions through the synergic combination of nanotransfer printing (nTP) and DSA of block copolymers is also introduced. This simple printing method can be applied on oxides, metals, polymers, and non-planar substrates without pretreatments. This talk will also report the direct formation of ordered memristor nanostructures on metal and graphene electrodes by the self-assembly of Si-containing BCPs. This approach offers a practical pathway to fabricate high-density resistive memory devices without using high-cost lithography and pattern-transfer processes. Finally, this talk will present a novel approach that can relieve the power consumption issue of phase-change memories by incorporating a thin $SiO_x$ layer formed by BCP self-assembly, which locally blocks the contact between a heater electrode and a phase-change material and reduces the phase-change volume. The writing current decreases by 5 times (corresponding to a power reduction of 1/20) as the occupying area fraction of $SiO_x$ nanostructures varies.