• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.248-248
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• 2006

The notable feature of the Cu(II) coordination polymer investigated here is its ability to self-assemble into a double-stranded helical structure with regular grooves along the helical axis, through the combination of metal-chloride dimeric interactions and repulsive interactions, as an organizing force. It is also remarkable that the double-stranded helices self-organize into a 2-D columnar structure in both the bulk state and aqueous solution. These results represent a unique example that weak metal-ligand bridging interactions can provide a useful strategy to construct stable double-stranded helical nanotubes.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권1호
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• pp.1-9
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• 2006

We introduce our in-house program, NANOCAD, for the modeling and simulation of carrier transport in nanoscale MOSFET devices including quantum-mechanical effects, which implements two kinds of modeling approaches: the top-down approach based on the macroscopic quantum correction model and the bottom-up approach based on the microscopic non-equilibrium Green’s function formalism. We briefly review these two approaches and show their applications to the nanoscale bulk MOSFET device and silicon nanowire transistor, respectively.

• 한국세라믹학회지
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• 제40권11호
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• pp.1027-1046
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• 2003

Nanostructured materials can be engineered by the controlled assembly of several suitable nano-objects as the building blocks. While, materials properties are determined by their atomic and molecular constituents and structure, their functionalities emerge when the microstructure of these early ensembles is in the nanometer regime. The properties and functionalities of these ensembles may be different as their size grows from the nano-regime to the micron regime and bulk structures. Nanotechnology, offers a unique possibility to manipulate the properties through the fabrication of materials using the nano-objects as building blocks. Nanotechnology is therefore considered an enabling technology by which existing materials, virtually all man-made materials, can acquire novel properties and functionalities making them suitable for numerous novel applications varying from structural and functional to advanced biomedical in-vivo and in-vitro applications.

• 한국전기전자재료학회논문지
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• 제32권3호
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• pp.252-255
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• 2019

Black phosphorus (BP) is a potential candidate for an anode in lithium ion batteries due to its high theoretical capacity and the large interlayer spacing in the monolayered phosphorene form, allowing for lithium intercalation/deintercalation. In this study, large-scale exfoliation of bulk BP was accomplished using a solution of NaOH and N-methyl-2-pyrrolidone (NMP), yielding phosphorene, which can be assembled into nanoflakes using electrophoretic deposition (EPD). Through the systematic addition of NaOH and subsequent sonication, BP nanoflakes were obtained in high yields by EPD, allowing for the integration of these nanoflakes into an anode in the film state. Anodes with a charge/discharge capacity of 172 mAh/g at a rate of 200 mA/g were obtained, which are promising for battery applications through various post-film treatments.

• 비파괴검사학회지
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• 제32권2호
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• pp.198-209
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• 2012

본 논문은 널리 사용되고 있는 표면 미세조직 검사 기술과 표면 및 표면직하의 평가가 가능한 마이크로/나노 비파괴평가 기술을 소개한다. 일반적으로 재료 표면에서의 마이크로/나노 결함과 조직 상태는 벌크재료의 기계적, 물리적, 화학적 특성에 크게 영향을 주게 된다. 표면 미세조직 검사 기술은 이러한 재료의 결함과 조직특성을 신뢰도 높게 평가하는 기술이다. 각 검사기술의 원리와 특징, 응용분야와 개발 등을 소개하였다. 따라서 비파괴산업에서 마이크로/나노 비파괴평가의 적용과 기술 개발이 폭넓게 가능할 것으로 판단된다.

• 한국염색가공학회지
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• 제21권4호
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• pp.33-38
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• 2009

Poly(vinyl acetate) films containing benzophenone were photocrosslinked by continuous UV irradiation.UV irradiation of PVAc film containing 5% benzophenone induced bulk crosslinking of the polymer indicated by 84.1% of gel fraction after ethyl acetate extraction. The crosslinking was attributed to the recombination of tertiary polymer radicals generated upon UV irradiation, which was enhanced by the hydrogen abstraction of benzophenone. Also the UV irradiation resulted in scission of ester linkage and photooxidation of PVAc surface, which was verified by ATR and zeta potential analysis, implying that the PVAc surface became more polar and hydrophilic. The zeta potential proportionally increased from +4.5mV to -26.8 mV with increasing UV irradiation. Also the surface energy of the PVAc film increased with higher UV irradiation upto 56.5 $mJ/m^2$ by the enhanced Lewis acid/base component with larger contribution of Lewis acid parameter. Accordingly the crosslinked PVAc showed higher thermal stability with increasing UV energy.

• 마이크로전자및패키징학회지
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• 제17권3호
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• pp.51-57
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• 2010

p형 $(Bi,Sb)_2Te_3$ 분말을 용해/분쇄법으로 제조하여 가압소결 후 가압소결조건에 따른 열전특성을 분석하였으며, 나노개재물로서 $ZrO_2$의 첨가에 따른 열전특성의 변화거동을 분석하였다. 가압소결온도를 $350^{\circ}C$에서 $550^{\circ}C$로 증가시킴에 따라 가압소결체의 Seebeck 계수가 275 ${\mu}V$/K에서 230 ${\mu}V$/K로 감소하였으며, 전기비저항이 6.68 $m{\Omega}m$-cm에서 1.86 $m{\Omega}$-cm로 감소하였다. 1 vol% 이상의 $ZrO_2$ 함량 증가에 따라 power factor가 계속 감소하는 거동으로부터 $(Bi,Sb)_2Te_3$ 가압소결체의 최대 power factor를 얻을 수 있는 $ZrO_2$ 나노개재물의 최적 함량은 1 vol% 미만으로 판단되었다.

• Structural Engineering and Mechanics
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• 제44권4호
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• pp.431-448
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• 2012

In this paper, the first-order shear deformation theory (FSDT) (Mindlin) for continuum incorporating surface energy is exploited to study the static behavior of ultra-thin functionally graded (FG) plates. The size-dependent mechanical response is very important while the plate thickness reduces to micro/nano scales. Bulk stresses on the surfaces are required to satisfy the surface balance conditions involving surface stresses. Unlike the classical continuum plate models, the bulk transverse normal stress is preserved here. By incorporating the surface energies into the principle of minimum potential energy, a series of continuum governing differential equations which include intrinsic length scales are derived. The modifications over the classical continuum stiffness are also obtained. To illustrate the application of the theory, simply supported micro/nano scaled rectangular films subjected to a transverse mechanical load are investigated. Numerical examples are presented to present the effects of surface energies on the behavior of functionally graded (FG) film, whose effective elastic moduli of its bulk material are represented by the simple power law. The proposed model is then used for a comparison between the continuum analysis of FG ultra-thin plates with and without incorporating surface effects. Also, the transverse shear strain effect is studied by a comparison between the FG plate behavior based on Kirchhoff and Mindlin assumptions. In our analysis the residual surface tension under unstrained conditions and the surface Lame constants are expected to be the same for the upper and lower surfaces of the FG plate. The proposed model is verified by previous work.

• Journal of Magnetics
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• 제13권4호
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• pp.149-152
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• 2008

In this report, we present the results of a study on the effects of the particle size on the properties of the Prussian blue (PB) analog $Na_xMn_y[Fe(CN){_6}]$. A novel synthesis method of the $Na_xMn_y[Fe(CN){_6}]$ nano-particles using an organic solvent, formamide, is employed. The size of the PB particles is found to be 100-150 nm for the samples prepared in the formamide solvent, which is much smaller than that of the samples prepared using water only. The broadening of the X-ray diffraction peaks of the nano-sized PB samples is attributed to the lattice disorder and a dramatic reduction in the particle size. The compositions of the samples are confirmed by an energy-dispersive X-ray analysis (EDAX), and the result proves that the samples are actually $Na_xMn_y[Fe(CN){_6}]$ Prussian blue. The UV-vis spectra show a broad intervalence charge-transfer (CT) band in the visible region between 400 and 700 nm, and the absorption decreases abruptly in the green region for the nano-sized PB sample. A divergence between the field cooled (FC) and zero field cooled (ZFC) magnetization curves is observed for the nano-sized PB sample at 11 K, indicating that nanoparticles in the sample are single domain superparamagnets with a blocking temperature of 11 K. Our results reveal that the nano-sized PB samples show significantly different optical and magnetic properties than those of the bulk PB samples.

• 한국분말재료학회지
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• 제21권4호
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• pp.301-306
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• 2014

Titanium alloys are extensively used in high-temperature applications due to their excellent high strength and corrosion resistance properties. However, titanium alloys are problematic because they tend to be extremely difficult-to-cut material. In this paper, the powder synthesis, spark plasma sintering (SPS), bulk material characteristics and machinability test of hybrid $Ti_2AlC$ ceramic bulk materials were systematically examined. The bulk samples mainly consisted of $Ti_2AlC$ materials with density close to theoretical value were synthesized by a SPS method. Random orientation and good crystallization of the $Ti_2AlC$ was observed at $1100^{\circ}C$ for 10 min under SPS sintering conditions. Scanning electron microscopy results indicated a homogeneous distribution and nano-laminated structure of $Ti_2AlC$ MAX phase. The hardness and electrical conductivity of $Ti_2AlC$ were higher than that of Ti 6242 alloy at sintering temperature of $1000^{\circ}C{\sim}1100^{\circ}C$. Consequently, the machinability of the hybrid $Ti_2AlC$ bulk materials is better than that of the Ti 6242 alloy for micro-EDM process of micro-hole shape workpiece.