• 한국분말재료학회지
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• 제29권1호
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• pp.56-62
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• 2022

Atomic layer deposition (ALD) is a promising technology for the uniform deposition of thin films. ALD is based on a self-limiting mechanism, which can effectively deposit thin films on the surfaces of powders of various sizes. Numerous studies are underway to improve the performance of thermoelectric materials by forming core-shell structures in which various materials are deposited on the powder surface using ALD. Thermoelectric materials are especially relevant as clean energy storage materials due to their ability to interconvert between thermal and electrical energy by the Seebeck and Peltier effects. Herein, we introduce a surface and interface modification strategy based on ALD to control the performance of thermoelectric materials. We also discuss the properties of the interface between various deposition materials and thermoelectric materials.

• Advances in nano research
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• 제12권5호
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• pp.483-488
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• 2022

The present work is an attempt to study the vibration analysis of the single-walled carbon nanotubes (SWCNTs) under the effect of the surface irregularity using Donnell's model. The surface irregularity represented by the parabolic form. According to Donnell's model and three-dimensional elasticity theory, a novel governing equations and its solution are derived and matched with the case of no irregularity effects. To understand the reaction of the nanotube to the irregularity effects in terms of natural frequency, the numerical calculations are done. The results obtained could provide a better representation of the vibration behavior of an irregular single-walled carbon nanotube, where the aspect ratio (L/d) and surface irregularity all have a significant impact on the natural frequency of vibrating SWCNTs. Furthermore, the findings of surface irregularity effects on vibration SWCNT can be utilized to forecast and prevent the phenomena of resonance of single-walled carbon nanotubes.

• 농업과학연구
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• 제29권1호
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• pp.44-54
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• 2002

이 실험은 우리나라 농가에서 사육되고 있는 타조(African ostrich) 신선란의 내 외부적인 품질 특성을 구명하고자 하였다. 타조의 난형은 장경 15.1~16.1cm, 단경 12.1~13.6cm로, 난형지수는 평균 81.0의 값을 나타내었고, 난각색은 계란보다 광택이 좋은 백색을 나타내었다. 계산식에 의한 난각강도와 난표면적 은 각각 $41.155kg/cm^3$과 $804.7cm^2$이었다. 타조 난의 난각두께는 난각막을 포함하여 1.89mm로, 각 부위별 난각두께는 거의 비슷한 값을 나타내었으며, 난각막 두께는 0.10mm로, 적도부가 두껍고 둔단부가 상대적으로 얇은 것으로 나타났다. 난각 기공수는 19.77개/$cm^2$으로, 첨단부의 기공수가 대체로 많은 것으로 나타났으며, 1개 알의 총기공수는 약 15241개 정도로 측정되었다. 타조 알의 각 부위의 난중에 대한 비율은 난황 25.1%, 난백 58.2% 그리고 난각은 16.7%이었고, 난백에 대한 난황의 비율(Y/W)은 0.43을 나타내었다. 타조의 알에 대한 난백과 난황의 품질을 조사한 결과 난액에 있어 직경과 높이는 각각 19.7cm 와 13.2mm로 난백지수는 0.07 이며, H.U는 -69.7, pH는 8.3이었으며, 난황에 있어서는 직경이 14.4 cm, 높이 29.4 mm로 난황지수는 0.20으로 나타났고, pH는 6.6 이었다. 또한 난황색은 두터운 난황막으로 인하여 계란보다는 엽은 황색을 보였다.

• 한국재료학회지
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• 제28권8호
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• pp.466-473
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• 2018

Nickel oxide(NiO) thin films, nanorods, and carbon nanotube(CNT)/NiO core-shell nanorod structures are fabricated by sputtering Nickel at different deposition time on alumina substrates or single wall carbon nanotube templates followed by oxidation treatments at different temperatures, 400 and $700^{\circ}C$. Structural analyses are carried out by scanning electron microscopy and x-ray diffraction. NiO thinfilm, nanorod and CNT/NiO core-shell nanorod structurals of the gas sensor structures are tested for detection of $H_2S$ gas. The NiO structures exhibit the highest response at $200^{\circ}C$ and high selectivity to $H_2S$ among other gases of NO, $NH_3$, $H_2$, CO, etc. The nanorod structures have a higher sensing performance than the thin films and carbon nanotube/NiO core-shell structures. The gold catalyst deposited on NiO nanorods further improve the sensing performance, particularly the recovery kinetics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1341-1342
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• 2006

Electrical characteristics of field-effect thin film transistors (TFTs) with p-channels of CdTe/CdHgTe core-shell nanocrystals are investigated in this paper. For the fabrication of bottom- and top-gate TFTs, CdTe/CrHgTe nanocrystals synthesized by colloidal method are first dispersed on oxidized p+ Si substrates by spin-coating, the dispersed nanoparticles are sintered at $150^{\circ}C$ to form the channels for the TFTs, and $Al_{2}O_{3}$ layers are deposited on the channels. A representative bottom-gate field-effect TFT with a bottom-gate $SiO_2$ layer exhibits a mobility of $0.21cm^2$/ Vs and an Ion/Ioff ratio of $1.5{\times}10^2$ and a representative top-gate field-effect TFT with a top-gate $Al_{2}O_{3}$ layer provides a field-effect mobility of $0.026cm^2$/ Vs and an Ion/Ioff ratio of $2.5{\times}10^2$. $Al_{2}O_{3}$ was deposited for passivation of CdTe/CdHgTe core-shell nanocrystal layer, resulting in enhanced hole mobility, Ior/Ioff ratio by 0.25, $3{\times}10^3$, respectively. The CdTe/CdHgTe nanocrystal-based TFTs with bottom- and top gate geometries are compared in this paper.

• 한국재료학회지
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• 제29권5호
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• pp.311-316
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• 2019

Transparent conducting electrodes are essential components in various optoelectrical devices. Although indium tin oxide thin films have been widely used for transparent conducting electrodes, silver nanowire network is a promising alternative to indium tin oxide thin films owing to its lower processing cost and greater suitability for flexible device application. In order to widen the application of silver nanowire network, the electrical conductance has to be improved while maintaining high optical transparency. In this study, we report the enhancement of the electrical conductance of silver nanowire network transparent electrodes by copper electrodeposition on the silver nanowire networks. The electrodeposited copper lowered the sheet resistance of the silver nanowire networks from $21.9{\Omega}{\square}$ to $12.6{\Omega}{\square}$. We perform detailed X-ray diffraction analysis revealing the effect of the amount of electrodeposited copper-shell on the sheet resistance of the core-shell(silver/copper) nanowire network transparent electrodes. From the relationship between the cross-sectional area of the copper-shell and the sheet resistance of the transparent electrodes, we deduce the electrical resistivity of electrodeposited copper to be approximately 4.5 times that of copper bulk.

• 박물관보존과학
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• 제25권
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• pp.27-34
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• 2021

국립중앙박물관 고려나전향상(高麗螺鈿香箱)은 당대의 제작기법과 미학적 표현을 종합적으로 보여주는 대표 문화재이다. 본 연구에서는 원형복원에 필요한 백골 제작에 사용된 수종 및 목공기술과 나전의 해부학적 특징을 조사하였다. 조사 결과 고려나전향상은 삼나무로 만들었으며 이는 일본과 교역관계를 짐작할 수 있으며 뚜껑 하단에 있는 띠 부분 부착하기 위하여 모서리 부분에 "주름꺾기법"을 사용한 것과 상판과 측판의 결합을 위하여 나무못을 사용한 것은 얇은 판재를 효율적으로 사용하기 위한 것으로 판단된다. 그리고 사용된 나전의 해부학적 특징을 조사한 결과 얇은 판상의 적층구조가 확인되었다. 이러한 특징은 일부 패각류에서 관찰되며 정확한 패각의 식별을 위한 연구가 필요하다.

• Korean Chemical Engineering Research
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• 제60권1호
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• pp.139-144
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• 2022

본 연구는 미세유체기술을 기반으로 매우 간단하고 효율적인 단분산성 하이드로젤 마이크로 입자 제조 방법을 제안하였다. 구체적으로, 유리모세관 미세유체장치 내에서 형성된 이중에멀젼은 자외선기반 자유라디칼 중합에 의해 빠르게 고형화가 이루어진다. 수용액에 분산됨과 동시에 계면활성제의 부족으로 인해 얇은 오일쉘은 자발적으로 분리되어, 단분산성 하이드로젤 입자를 형성하였다(C.V.=1%). 본 연구의 결과는 water-in-oil (w/o) 단일에멀젼 기반의 제조 방법과 달리 오일 부피를 최소한으로 사용하여 크기 및 조성 제어가 가능한 단분산성 하이드로젤 입자의 제조가 달성될 수 있음을 보여준다. 마지막으로, 상도표를 기반으로 미세유체장치 내 유동 패턴에 대한 심층 연구는 상대적인 부피 유속들 간의 중요한 상관관계를 나타내며 하이드로젤 마이크로 입자의 안정적인 제조를 위한 실험적 근거를 제시하였다.

• Journal of Mechanical Science and Technology
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• 제14권1호
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• pp.48-56
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• 2000

The bifurcation problem of thin walled structures in contact with rigid surfaces is formulated by adopting the multiple scales asymptotic technique. The general theory developed in this paper is very useful for the bifurcation analysis of waviness instabilities in the sheet metal forming. The formulation is presented in a full Lagrangian formulation. Through this general formulation, the bifurcation functional is derived within an error of O($(E^4)$) (E: shell's thickness parameter). This functional can be used in numerical solutions to sheet metal forming instability problem.

• 대한기계학회논문집
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• 제15권2호
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• pp.523-536
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• 1991

This dissertation analyzes the running mechanism of flexible and thin tape above rotating head through the numerical simulation and the experiment. The scope of analysis is confined to the phenomena of two dimensional elasto hydrodynamic lubrication between the protruded bump on a rotating cylinder and the running tape. This model is based on the elastic deformation equation of plate and shell and Reynolds equation. Finite difference method is employed as a numerical technique to calculate (1) the distribution of pressure between the running tape and rotating bump and (2) the vertical deformation of elastic thin tape over he rotating bump under hydrodynamic pressure. In numerical analyses, the effects of bump size on flying characteristics of the tape were evaluated and examined considering the influence of tension and stiffness of tape.