• 한국분말재료학회지
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• 제8권1호
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• pp.49-54
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• 2001

The synthesis and characteristics of W-Ni-Fe nanocomposite powder by hydrogen reduction of ball milled W-Ni-Fe oxide mixture were investigated. The ball milled oxide mixture was prepared by high energy attrition milling of W blue powder, NiO and $Fe_2O_3$ for 1 h. The structure of the oxide mixture was characteristic of nano porous agglomerate composite powder consisting of nanoscale particles and pores which act as effective removal path of water vapor during hydrogen reduction process. The reduction experiment showed that the reduction reaction starts from NiO, followed by $Fe_2O_3$ and finally W oxide. It was also found that during the reduction process rapid alloying of Ni-Fe yielded the formation of $\gamma$-Ni-Fe. After reduction at 80$0^{\circ}C$ for 1 h, the nano-composite powder of W-4.57Ni-2.34Fe comprising W and $\gamma$-Ni-Fe phases was produced, of which grain size was35nm for W and 87 nm for $\gamma$-Ni-Fe, respectively. Sinterability of the W heavy alloy nanopowder showing full density and sound microstructure under the condition of 147$0^{\circ}C$/20 min is thought to be suitable for raw material for powder injection molding of tungsten heavy alloy.

• 대한금속재료학회지
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• 제49권10호
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• pp.811-817
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• 2011

In this study, we have investigated the role of a metal oxide hole injection layer (HIL) between an Indium Tin Oxide (ITO) electrode and an organic hole transporting layer (HTL) in organic light emitting diodes (OLEDs). Nickel Oxide films were deposited at different deposition times of 0 to 60 seconds, thus leading to a thickness from 0 to 15 nm on ITO/glass substrates. To study the influence of NiO film thickness on the properties of OLEDs, the relationships between NiO/ITO morphology and surface properties have been studied by UV-visible spectroscopy measurements and AFM microscopy. The dependences of the I-V-L properties on the thickness of the NiO layers were examined. Comparing these with devices without an NiO buffer layer, turn-on voltage and luminance have been obviously improved by using the NiO buffer layer with a thickness smaller than 10 nm in OLEDs. Moreover, the efficiency of the device ITO/NiO (< 5 nm)/NPB/$Alq_3$/ LiF/Al has increased two times at the same operation voltage (8V). Insertion of a thin NiO layer between the ITO and HTL enhances the hole injection, which can increase the device efficiency and decrease the turn-on voltage, while also decreasing the interface roughness.

• Composites Research
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• 제32권3호
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• pp.141-147
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• 2019

In this study, micro-sized and nano-sized pure aluminum (Al) powders were compressed by unidirectional pressure at room temperature. Although neither type of Al bulk was heated, they had a high relative density and improved mechanical properties. The microstructural analysis showed a difference in the process of densification according to particle size, and the mechanical properties were measured by the Vickers hardness test and the nano indentation test. The Vickers hardness of micro Al and nano Al fabricated in this study was five to eight times that of ordinary Al. The grain refinement effect was considered to be one of the strengthening factors, and the Hall-Petch equation was introduced to analyze the improved hardness caused by grain size reduction. In addition, the effect of particle size and dispersion of aluminum oxide in the bulk were additionally considered. Based on these results, the present study facilitates the examination of the effect of particle size on the mechanical properties of compacted bulk fabricated by the powder metallurgy method and suggests the possible way to improve the mechanical properties of nano-crystalline powders.

• 한국재료학회지
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• 제24권1호
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• pp.25-32
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• 2014

In this study, nano-sized cobalt oxide powder with an average particle size below 50 nm was prepared from a cobalt chloride solution by the spray pyrolysis process. The influences of reaction temperature on the properties of the generated powder were examined. The average particle size of the particles formed based on the spray pyrolysis process at a reaction temperature of $700^{\circ}C$ is roughly 20 nm. Moreover, most of these particles cannot appear with an independent type, thereby coexisting in a droplet type. When the reaction temperature increases to $800^{\circ}C$, the average particle size not only increases to roughly 40 nm but also shows a more dense structure while the ratio of particles which shows a polygonal form significantly increases. As the reaction temperature increases to $900^{\circ}C$, the distribution of the particles is from roughly 70 nm to 100 nm, while most of the particle surface is more intricately close and forms a polygonal shape. When the reaction temperature increases to $1000^{\circ}C$, the particle size distribution of the powder shows an existing form from 80 nm to at least 150 nm in an uneven form. As the reaction temperature increases, the XRD peak intensity gradually increases, yet the specific surface area gradually decreases.

• 한국분말재료학회지
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• 제11권6호
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• pp.493-502
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• 2004

In this study, nano-sized indium oxide powder with the average particle size below 100 nm is fab-ricated from the indium chloride solution by the spray pyrolysis process. The effects of the reaction temperature, the concentration of raw material solution and the inlet speed of solution on the properties of powder were studied. As the reaction temperature increased from 850 to $1000^{\circ}C$, the average particle size of produced powder increased from 30 to 100 nm, and microstructure became more solid, the particle size distribution was more irregular, the intensity of a XRD peak increased and specific surface area decreased. As the indium concentration of the raw material solution increased from 40 to 350 g/l, the average particle size of the powder gradually increased from 20 to 60 nm, yet the particle size distribution appeared more irregular, the intensity of a XRD peak increased and spe-cific surface area decreased. As the inlet speed of solution increased from 2 to 5 cc/min., the average particle size of the powder decreased and the particle size distribution became more homogeneous. In case of the inlet speed of 10 cc/min, the average particle size was larger and the particle size distribution was much irregular compared with the inlet speed of 5 cc/min. As the inlet speed of solution was 50 cc/min, the average particle size was smaller and microstructure of the powder was less solid compared with the inlet speed of 10 cc/min. The intensity of a XRD peak and the variation of specific area of the powder had the same tendency with the variation of the average par-ticle size.

• 공업화학
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• 제24권4호
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• pp.391-395
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• 2013

본 연구에서는 자외선 흡수 물질로 잘 알려진 zinc oxide (ZnO) 나노분말을 세 가지 합성조건에서 수열합성법으로 합성하였다. 또한, 분산성을 향상시키기 위하여 합성된 ZnO 나노분말의 표면을 다양한 실란계 계면활성제를 사용하여 표면 개질하였고, 표면개질된 ZnO 나노분말을 분산제로 72 h 동안 볼밀링하여 분산 졸 시료를 제조하였다. 30 nm 크기로 합성된 ZnO 나노분말을 3-chloropropyl trimethoxy silane로 표면개질하여 폴리우레탄계 분산제로 제조한 분산 졸 시료가 가장 높은 자외선 차단 특성 및 가시광 투과율을 가지면서 분산 안정성이 가장 우수하였다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2002년도 추계학술강연 및 발표대회
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• pp.76-77
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• 2002

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2005년도 춘계학술강연 및 발표대회강연 및 발표논문 초록집
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• pp.35-36
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• 2005

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2003년도 international symposium on advanced powder metallurgy
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• pp.80-81
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• 2003

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2008년도 High Temperature Superconductivity Vol.XVIII
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• pp.86-86
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• 2008