• Journal of the Korean Magnetics Society
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• v.14 no.3
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• pp.105-108
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• 2004

Array of magnetic Ni nanostructures has been fabricated on Si substrate by using nanoporous alumina film as a mask during deposition. The nanostructures are truncated cone-shape and the lateral sizes are comparable to height. While the continuous film shows well-defined in-plane magnetization, the nanostructure shows perpendicular component of magnetization at remanence. The hysterectic behavior of nanostructures is dominated by the demagnetizing field instead of interaction among them.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.168.2-168.2
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• 2017

발열체는 전기 에너지를 열 에너지로 변환시키는 전기 저항체인데, Ni-Cr계 합금이 발열 가능 온도가 범위가 크고 열 효율 및 내 산화성, 내 부식성이 우수하여 발열체로 많이 사용되고 있다. 그리고 기존의 선형 발열체의 효율성을 개선한 면상 발열체가 개발되었고, 최근 나노 기술의 발달로 나노크기의 ITO(Indium Tin Oxide) 입자나 탄소나노튜브가 코팅된 형태의 투명 면상 발열체가 개발되어 주목을 받고 있다. 투명 면상 발열체는 발열체의 형태를 거시적으로 확인할 수 없기 때문에 자동차의 전면 유리 히터 및 건축용 기능성 창호 등의 심미적 효과를 요구하는 제품에 사용될 수 있다. 본 연구에서는 PVP(Poly vinyl Pirrolidone)을 이용하여 Ni-Cr Nanofiber 제조를 위한 효율적인 전기 방사 조건을 도출한다. PVP 질량에 따라서 Ethanol과 Methanol, 물을 이용하여 viscosity와 ion conduciviy를 조절하였고, 전기방사 조건으로 bead를 최소화 하는 나노섬유를 얻었다. 이어서 Ni-Cr/PVP 용액은 Metal Precursor wt.% 조절 및 방사조건으로 100~300nm의 직경을 가진 나노 섬유를 얻을 수 있었다. 산화/환원 열처리 후 PVP와 Oxide가 제거된 Ni-Cr nanofiber를 합성하였다. Nanofiber 형상은 FE-SEM으로 측정하였으며, XRD, FT-IR 분석을 통해 제작된 나노 섬유의 구조적 특성을 확인하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.2
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• pp.78-83
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• 2021

In this study, we prepared NiCo2O4 nanoparticles with large surface area by hydrothermal synthesis. In order to optimize the processing conditions for spinel NiCo2O4 nanoparticles with large surface area, experimental variables including concentration of Ni and Co precursor, reaction time, and temperature for post-heat treatment were evaluated. Optimized conditions for spinel NiCo2O4 with large surface area were [Ni]/[Co] 1:2 ratio, reaction time for 12 h, and post-heat treatment at 400℃. To investigate the feasibility as potential application for glucose sensor, electrochemical tests of the prepared NiCo2O4 nanoparticles in response to glucose was performed, which suggests that the NiCo2O4 can be suitable for a non-enzymatic-based electrochemical glucose sensor based on its high sensitivity and selectivity for glucose detection.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.10
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• pp.1306-1311
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• 2020

In this study, we proposed an anti-reflective nano-structure to improve the photoresponsivity of AlGaN UV photodiode that can be used as a receiver in a solar blind UV optical communication system. The anti-reflective nano-structure was fabricated by forming Ni nano-clusters on SiO2 film followed by etching the underneath SiO2 film. A sample with the anti-reflective nano-structure exhibited lower surface reflection along with less dependency on the wavelength in comparison with a sample without the nano-structure. Finally, a UV photodiode was fabricated by applying an anti-reflective structure produced by heat-treating a 2 nm-thick Ni layer. The photodiode fabricated with the proposed nano-structure exhibited noticeable improvement in the photoresponsivity at the wavelength range from 240 nm to 270 nm in comparison with the same photodiode with a SiO2 film without the nano-structure.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.593-599
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• 2023

Nickel oxide (NiO) nanoparticles were successfully synthesized by a simple liquid phase process for producing ceramics powder using a precursor impregnated with a nickel(II) nitrate hexahydrate aqueous solution in an industrial pulp. The microfibrile structure of the precursor impregnated with nickel nitrate hexahydrate aqueous solution was confirmed by scanning electron microscope (SEM), and the crystal structure and particle size of nickel oxide (NiO) particles produced as the heat treatment temperature of the precursor were analyzed by X-ray diffraction (XRD) and SEM. As a result, it was confirmed through XRD and SEM analysis that the temperature at which the organic material of the precursor is completely thermally decomposed was 495-500℃, and the size and crystallinity of the nickel oxide particles produced increased as the heat treatment temperature increased. The size of the nickel oxide particles obtained by heat treatment at 500-800℃ for 1 hour was 50-200 nm. It was confirmed by XRD and SEM analysis that a NiO crystal phase was formed at a heat treatment temperature of 380℃, only a single NiO phase existed until 800℃.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.06a
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• pp.130-131
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• 2004

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.133-140
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• 2010

Carbon fiber has many potential applications in a wide array of fields of solar cell, fuel cell, batteries, and polymer matrix composites due to an exceptional mechanical properties and chemical stability. In this study, the effects of catalysts on the property of carbon nanostructures grown on the carbon fiber were systematically investigated. The surface treatment of carbon fiber and catalysts synthesis for carbon nanostructures growth were carried out by one-pot ELP method and thermal CVD, respectively. The surface morphology and crystal structure of carbon nanostructures were examined using a field emission scanning electron microscope and transmission electron microscope. Depending on the type of catalysts and the molar ratio, various types of carbon nanostructures like carbon nanotube, carbon nanofilament, carbon nanospring and etc. were synthesized on the surface of carbon fibers surface.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.29.1-29.1
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• 2011

ReRAM은 metal-oxide-metal구조로 차세대 비활성 메모리를 대체하기 위하여 연구되어왔다. ReRAM은 낮은 전력 소모와 다른 두 저항상태 사이의 높은 scalability를 갖는 장점이 있지만 높은 reset전류와 일정하지 않은 저항 값을 갖고 있어 실용화에 어려움을 겪고 있다. 저항변화현상의 메커니즘은 일반적으로 일정 전압이 가해 졌을 때, MIM 구조의 산화물 내에서 필라멘트가 형성되었다 파괴되는 것으로 알려져 있다. 저항스위칭 메모리의 작동능력을 증진시키기 위해서는, oxide층의 두께조절, 산화층과 electrode 사이의 계면 특성 연구가 필요하다. 본 연구에서는, 전기화학증착법을 이용하여 Au-NiO-Au segmented 나노와이어 구조를 만들었다. 전기화학증착 방법을 이용하면 에칭 손상없이 간단하게 나노 구조체를 형성 할 수 있고, 나노 사이즈로 제작된 산화층이 전도성 필라멘트가 형성되는 영역을 제한하여 reset전류를 줄일 수 있는 장점이 있다. 또한 열처리 과정에서 Au가 NiO부분에 diffusion되는 현상을 이용하여 doping에 따른 switching 변화 특성도 관찰하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.25-29
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• 2012

The properties of carbon nanotube-metal hybrid nanostructures are critically dependent on the structure and chemistry of the metal-carbon nanotube interface. In this study, the interface between nickel and multi-walled carbon nanotubes (CNTs) has been investigated using physical vapor-deposited (sputter-deposited) nickel onto the surface of freestanding carbon nanotube arrays processed by nano-imprint lithography (NIL). These interfaces have been characterized by transmission electron microscopy and 3D atom probe tomography. In the nickel nanocrystals growing on the CNT surface, a metastable hexagonal $Ni_3C$-types phase appears to be stabilized. The structural stability of the nickel-CNT interface is also discussed and related to potential implications for the properties of these nanocomposites.

• Clean Technology
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• v.28 no.2
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• pp.154-162
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• 2022

Microstructured Al@Al₂O₃ and Al@Ni-Al LDH (LDH = layered double hydroxide) core-shell metal-ceramic composites are prepared by hydrothermal reactions of aluminum (Al) metal substrates. Controlled hydrothermal reactions of Al metal substrates induce the hydrothermal dissolution of Al ions at the Al-substrate/solution interface and reconstruction as porous metal-hydroxides on the Al substrate, thereby constructing unique metal-ceramic core-shell composite structures. The morphology, composition, and crystal structure of the core-shell composites are affected largely by the ions in the hydrothermal solution; therefore, the critical physicochemical and surface properties of these unique metal-ceramic core-shell microstructures can be modulated effectively by varying the solution composition. A Ni/Al@Al₂O₃ catalyst with highly dispersed catalytic Ni nanoparticles on an Al@Al₂O₃ core-shell substrate was prepared by a controlled reduction of an Al@Ni-Al LDH core-shell prepared by hydrothermal reactions of Al in nickel nitrate solution. The reduction of Al@Ni-Al LDH leads to the exolution of Ni ions from the LDH shell, thereby constructing the Ni nanoparticles dispersed on the Al@Al₂O₃. The catalytic properties of the Ni/Al@Al₂O₃ catalyst were investigated for CO₂ methanation reactions. The Ni/Al@Al₂O₃ catalyst exhibited 2 times greater CO₂ conversion than a Ni/Al₂O₃ catalyst prepared by conventional incipient wetness impregnation and showed high structural stability. These results demonstrate the high effectiveness of the design and synthesis methods for the metal-ceramic composite catalysts derived by hydrothermal reactions of Al metal substrates.