• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.156-157
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• 2007

나노임프린팅 기술을 이용하여 원기둥형 나노 패턴을 갖는 도광판을 제작하였다. 나노 임프린트 공정을 이용하기 위해서는 니켈 스탬퍼가 필요하기 때문에 이를 제작하기 위하여 실리콘 웨이퍼 상에 건식식각을 이용하여 실리콘 몰드를 제작하였다. 제작된 실리콘 몰드를 전주도금을 이용하여 니켈 스탬퍼를 제작하였다. 제작된 니켈 스탬퍼를 사용한 나노임프린트 공정을 통해 원기둥 나노패턴을 갖는 도광판을 제작하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.405-413
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• 2017

In this paper, we study the biaxial buckling analysis of nonlocal MEE(magneto-electro-elastic) nano plates based on the first-order shear deformation theory. The in-plane electric and magnetic fields can be ignored for MEE(magneto-electro-elastic) nano plates. According to magneto-electric boundary condition and Maxwell equation, the variation of magnetic and electric potentials along the thickness direction of the MME plate is determined. In order to reformulate the elastic theory of MEE(magneto-electro-elastic) nano-plate, the nonlocal differential constitutive relations of Eringen is used. Using the variational principle, the governing equations of the nonlocal theory are discussed. The relations between nonlocal and local theories are investigated by computational results. Also, the effects of nonlocal parameters, in-plane load directions, and aspect ratio on structural responses are studied. Computational results show the effects of the electric and magnetic potentials. These computational results can be useful in the design and analysis of advanced structures constructed from MEE(magneto-electro-elastic) materials and may be the benchmark test for the future study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1109-1117
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• 2014

We study free vibration analysis of sigmoid functionally graded materials(S-FGM) nano-scale plates, using a nonlocal elasticity theory of Eringen in this paper. This theory has ability to capture the both small scale effects and sigmoid function in terms of the volume fraction of the constituents for material properties through the plate thickness. Numerical solutions of S-FGM nano-scale plate are presented using this theory to illustrate the effect of nonlocal theory on natural frequency of the S-FGM nano-scale plates. The relations between nonlocal and local theories are discussed by numerical results. Further, effects of (i) power law index (ii) nonlocal parameters, (iii) elastic modulus ratio and (iv) thickness and aspect ratios on nondimensional frequencies are investigated. In order to validate the present solutions, the reference solutions are compared and discussed. The results of S-FGM nano-scale plates using the nonlocal theory may be the benchmark test for the free vibration analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.179-179
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• 2010

1차원 나노구조를 갖는 ZnO를 성장하기 위해 Laser ablation, Chemical vapor deposition (CVD), Chemical transport method, Molecular beam epitaxy, Sputtering 등의 다양한 형성법들이 이용되어지고 있다. 특히 대량생산과 경제성 측면에서 많은 장점을 가지고 있는 CVD를 이용한 ZnO 성장 및 응용 연구가 활발하게 수행되고 있다. 본 연구에서는 Thermal CVD를 이용하여 반응물질과 기판 사이의 거리, 기판온도, $O_2$/Zn 비율 등의 성장변수를 변화시켜 ZnO 나노구조를 성장하고 구조 및 광학적 특성을 연구하였다. Scanning electron microscope를 통한 구조 특성평가 결과 반응물질과 기판 사이의 거리가 13 cm 이하의 조건에서 ZnO 나노구조들은 나노판(Nanosheet)과 나노선(Nanowire)이 혼재하여 성장된 것을 보였다. 그리고 반응물질과 기판사이의 거리가 15 cm 이상부터 나노판이 없어지고 수직한 ZnO 나노막대(Nanorod)가 형성되었다. 상온 Photoluminescence 스펙트럼에서 반응물질과 기판사이의 거리가 5에서 15 cm로 증가할수록 결함 (Defect)에 의해 발생된 515 nm 파장의 최대세기 (Maximum intensity)가 10배 이상 감소한 반면, ZnO 나노구조에 의한 378 nm 파장의 NBE발광 (Near band edge emission)은 8배 이상 증가하였다. 이러한 구조 및 광학적 결과로부터, 질서 없이 성장된 것보다 수직 성장된 ZnO 나노구조의 결정질(Crystal quality)이 좋은 것을 확인하였다. 이를 바탕으로 성장변수에 따른 ZnO 나노구조의 형성 메커니즘을 Zn와 O 원자의 성장거동을 기반으로 한 모델을 이용하여 해석하였다.

• Korean Journal of Optics and Photonics
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• v.32 no.4
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• pp.163-171
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• 2021

Conventional white light-emitting diodes (LEDs) for lighting applications consist of blue LEDs and yellow phosphors, the spectrum of which lacks deep red. To improve the color-rendering characteristics of white LEDs, a red quantum-dot film was applied to the diffuser plate of LED lighting. The mean free paths of the quantum dots and the concentration of the TiO₂ particles in the diffuser plate were adjusted to optimize the optical structure of the lighting. The color-rendering index (CRI) was greater than 90 for most conditions, which demonstrates that adoption of the red quantum-dot film is an effective way for improving the color-rendering properties of conventional white LEDs. The angular dispersion of color coordinates could be removed by utilizing the optical cavity formed between the diffuser plate and the reflector on the bottom of the lighting, where multiple passages of the light through the quantum-dot film reduced the differences in optical path length depending on the viewing angle.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.201.2-201.2
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• 2015

현대 디지털 사회에서 고효율 에너지와 파워소스에 관한 요구가 커짐에 따라 차세대 에너지 저장 소자에 대한 연구가 계속되고 있다. 그 중 리튬이온 배터리, 슈퍼커패시터, 그리고 연료 전지들이 우리의 일상생활에서 점점 더 중요하게 자리잡아가고 있는데 이런 다양한 에너지 저장소자 중 슈퍼커패시터가 많은 관심을 받고 있다. 이는 긴 수명, 빠른 충-방전 속도, 높은 에너지 밀도, 그리고 안전함 때문이다. 슈퍼커패시터는 에너지 저장 메커니즘에 따라 두 가지로 분류될 수 있는데 전기이중층 커패시터(EDLC)와 슈도커패시터(pseudocapacitor)로 나누어질 수 있다. 슈도커패시터는 active 물질과 전해질 이온 간의 전기화학적 반응으로 인해 EDLC보다 더 많은 에너지를 저장할 수 있다. 그러므로 지금까지 새로운 형태의 슈도용량성 물질을 만들기 위한 노력이 집중되고 있다. 본 연구에서는 전기화학적증착 방법을 통해 graphene-like ${\beta}$-nickel hydroxide (${\beta}-Ni(OH)_2$) 나노판 구조를 전도성 직물에 합성하였다. ${\beta}-Ni(OH)_2$ 슈도커패시터의 유연하고 효율적인 비용의 전극으로서 높은 비정전용량, 우수한 전기화학 가역성, 그리고 뛰어난 사이클 안정성을 보였다. 이런 쉬운 방법으로 유연한 전도성 직물에 합성된 metal hydroxide/oxide 나노구조는 웨어러블 에너지 저장소자와 변환소자 분야에 사용될 것으로 기대된다.

• Applied Chemistry for Engineering
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• v.35 no.2
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• pp.96-99
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• 2024

A sintering paste for bonding copper plates was synthesized using Cu formate nanofibers on Cu microparticles, mixed with formic acid. Copper oxide nanofibers of 10 ㎛ grown at 400 ℃ on Cu microparticles on the surface were transformed into copper formate nanofibers through the mixing of formic acid. Compared to Cu bulk particles or nanoparticles, Cu formate on Cu microparticles decomposed into metallic Cu at a lower temperature of 210 ℃, facilitating the sintering of copper paste. The growth of nanofiber on Cu microparticles allowed for an increase in the reaction rate of formation to copper formate, aggregating surface area, and decomposition rate of copper formate, resulting in fast sintering.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.52-60
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• 2017

This study examined the structural stability of nonlocal magneto-electro-elastic nano plates on elastic foundations using first-order shear deformation theory. Navier's method has been used to solve the buckling loads for all edges simply supported boundary conditions. On the other hand, biaxial buckling analysis of nano-plates has beenrarely studied. According to the Maxwell equation and the magneto-electro boundary condition, the change inthe magnetic and electric potential along the thickness direction of the magneto-electro-elastic nano plate wasdetermined. To reformulate the elasticity theory of the magneto- electro-elastic nano plate, the differential constitutive equation of Eringen was used and the governing equation of the nonlocal elasticity theory was studied using variational theory. The effects of the elastic foundation arebased on Pasternak's assumption. The relationship between nonlocal theory and local theory was analyzed through calculation results. In addition, structural stability problems were investigated according to the electric and magnetic potentials, nonlocal parameters, elastic foundation parameters, and side-to-thickness ratio. The results of the analysis revealedthe effects of the magnetic and electric potential. These calculations can be used to compare future research on new material structures made of magneto-electro-elastic materials.

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.452-455
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• 2001

고분자/실리케이트 나노복합체란 고분자 매트릭스에 층상 구조의 점토 광물을 나노 스케일의 시트상의 기본 단위로 박리(exfoliation)ㆍ분산시켜 얻어진 복합체를 말한다. 실리케이트를 구성하는 두께 1nm 정도의 판으로 박리ㆍ분산시키기 때문에 5wt% 정도의 첨가량만으로도 고분자의 획기적인 물성 개선이 가능하다는 장점을 가지고 있다[1]. (중략)

• Composites Research
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• v.24 no.2
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• pp.38-45
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• 2011

In this paper, we present an optimization method for the single Dallenbach-layer type microwave absorbers composed of E-glass fabric/epoxy composite laminates. The composite prepreg containing carbon nanotubes (CNT) was used to control the electrical property of the composites laminates. The design technology using the genetic algorithm was used to get the optimal thicknesses of the laminates and the filler contents at various center frequencies, for which the numerical model of the complex permittivity of the composite laminate was incorporated. In the optimal design results, the content of CNT increased in proportion to the center frequency, but, on the contrary, the thickness of the microwave absorbers decreased. The permittivity and reflection loss are measured using vector network analyzer and 7 mm coaxial airline. The influence of the mismatches in between measurement and prediction of the thickness and the complex permittivity caused the shift of the center frequency, blunting of the peak at the center frequency and the reduction of the absorbing bandwidth.