• Applied Microscopy
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• v.46 no.1
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• pp.14-19
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• 2016

Currently, focused ion beams (FIB) are widely used for specimen preparation in atom probe tomography (APT), which is a three-dimensional and atomic-scale compositional analysis tool. Specimen preparation, in which a specific region of interest is identified and a sharp needle shape created, is the first step towards successful APT analysis. The FIB technique is a powerful tool for site-specific specimen preparation because it provides a lift-out technique and a controllable manipulation function. In this paper, we demonstrate a general procedure containing the crucial points of FIB-based specimen preparation. We introduce aluminum holders with moveable pin and an axial rotation manipulator for specimen handling, which are useful for flipping and rotating the specimen to present the backside and the perpendicular direction. We also describe specimen preparation methods for nanowires and nanopowders, using a pick-up method and an embedding method by epoxy resin, respectively.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.924-925
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• 2006

In this study, hydroxyapatite (HAp) and hydroxyapatite-yttria stabilized zirconia (HAp-3YSZ) with 20 vol.%-($ZrO_2+3%mol\;Y_2O_3$) nanopowders were consolidated very rapidly to full density by High-frequency induction heat sintering (HFIHS). Effects of temperature and the addition of 3YSZ on the toughness, hardness and microstructure properties have been studied. 3YSZ second phase toughening HAp composites with higher toughness were successfully developed at relatively low temperatures through this technique. Compared with hardness and toughness obtained for pure HAp, the hardness and toughness for HAp-20vol. % 3YSZ were much higher.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.955-956
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• 2006

Fe-doped $TiO_2$ nanopowders were prepared by mechanical alloying (MA) varying Fe contents up to 8.0 wt.%. The UV-vis absorption showed that the UV absorption for the Fe-doped powder shifted to a longer wavelength (red shift). The absorption threshold depends on the concentration of nano-size Fe dopant. As the Fe concentration increased up to 4 wt.%, the UV-vis absorption and the magnetization were increased. The benefical effect of Fe doping for photocatalysis and ferromagnetism had the critical dopant concentration of 4 wt.%. Based on the UV absorption and magnetization, the dopant level is localized to the valence band of $TiO_2$.

• Journal of Powder Materials
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• v.10 no.3
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• pp.157-160
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• 2003

Phase contents and elemental composition of ultradispersed powders obtained by the electrical explosion of tin-leadalloy powders are investigated. It is demonstrated that during the explosion and subsequent cooling, surface layers of powder particles are enriched in lead compared to the initial alloy. The thermal stability of powders oxidizing in air is also investigated.

• Journal of Powder Materials
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• v.10 no.3
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• pp.161-163
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• 2003

The feasibility of obtaining highly dispersed aluminum oxide powders by the electrical explosion of aluminum conductors in an inert gas atmosphere and the subsequent oxidation of aluminum particles by water prior to their contact with air is demonstrated. For a specific surface area of the initial aluminum powder of 6.5$m^2$/g, the corresponding specific surface area of the resultant aluminum oxide nanopowder was as large as 300$m^2$/g.

• Journal of Powder Materials
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• v.15 no.6
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• pp.466-470
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• 2008

Experiments with a URT-0.5 accelerator (0.5 MeV, 50 ns, 1 kW) generating a nanosecond electron beam for irradiation of silver nitrate in various liquid solutions (water and toluene) were performed with the aim of producing silver nanopowders. A radiochemical reaction allows making weakly agglomerated pure Ag powders with particles of 10-15 nm and 30-50 nm in size by irradiation in toluene and water respectively. The injection of the nanosecond electron beam energy to the solution is optimal. As the absorbed dose increases, the output of the radiochemical reaction does not grow, but more agglomerated powders are synthesized.

• Journal of the Semiconductor & Display Technology
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• v.12 no.3
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• pp.1-6
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• 2013

In many technical fields including electronics and display manufacturing processes, properties of coating liquids could be greatly enhanced by adding nanopowders and it requires efficient mixing techniques to achieve uniform dispersion of nanoparticles in liquids. This paper presents the three-dimensional CFD simulations on the flowfields of a highly viscous liquid in the large scale industrial mixer of impeller type. The effects of several important design and operation parameters such as impeller geometry, rotational speed, and degree of liquid viscosity are investigated to appreciate the mixing performance by examining the computational results for flow pattern of rotationally stirred liquid of high viscosity in the mixer.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1538-1539
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• 2006

직경 0.3mm, 길이 40mm의 은 와이어를 증류수 중에서 전기폭발(wire explosion)을 발생시켰다. 전기폭발에 의해서 액체 중에 충격파 발생에 의한 공간의 형성과 더불어 금속 증기 및 플라즈마가 발생하고, 증기의 응축에 의해서 나노분말이 생성되는 것을 확인하였다. 또한 생성된 나노분말은 생성공간의 붕괴와 더불어 액체속으로 자연스럽게 분산되었다. 제조된 은 나노분말은 비교적 잘 분산된 구형의 분말이었으며 비표면적은 $16.2m^2/g$(평균입도 35nm)을 나타내었다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.368-369
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• 2006

By means of magnetic pulsed compaction and sintering of weakly aggregated alumina based nanopowders the jet forming nozzle samples for the hydroabrasive cutting were fabricated. The ceramics was obtained from pure alumina, as well as from alumina, doped by $TiO_2$, MgO and AlMg. It was shown that the samples sintered from AlMg doped $Al_2O_3$ powder have the best mechanical properties and structural characteristics: relative density ${\sim}0.97$, channel microhardness. - 18-20 GPa, channel surface roughness ${\sim}0.7\;{\mu}m$, average crystallite size ${\sim}1\;{\mu}m$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2003.04a
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• pp.34-34
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• 2003

전기설()폭발(Electric Wire Explosion)법은 고밀도 전류를 금속와이어에 인가시키면 저항 발열에 의해서 금속와이어가 빠르게 가열되고, 수$\mu$sec 이내에 초기체적에 비해 2~3배나 팽창한 후 폭발하는 현상을 이용하여 나노분말을 제조하는 방법으로써, 다른 제조방법에 비해 값싼 비용으로 1~50$\mu$sec의 짧은 시간동안 극히 높은 온도($10^4~10^6K$)에 도달하기 때문에, 와이어 전체가 동시에 기화하여 원재료의 조성을 갖는 분말의 합성이 가능하며, 공급되는 에너지와 시간, 챔버의 용적과 압력을 제어함으로써 평균 분말 크기를 조절할 수 있다는 잇점이 있다. 또한, 금속 와이어 주위의 분위기를 조절함으로써 금속나노분말뿐만 아리나 산화물$\cdot$질화물$\cdot$탄화물 분말, 합금 분말, 화학적 화합물이나 복합재료 나노분말들을 만들 수 있어서 여러 산업분야에 대한 응용이 크게 기대되고 있다. 본 연구에서는 전기선()폭발 챔버(Fig. 1) 와 최대 20kV까지 제어 가능한 고출력 펄스 전원장치를 자체 제작하고, 이를 이용하여 은(Ag)나노분말 합성에 대한 실험을 행하였다. 이렇게 제조된 분말은 SEM, XRD, PSA, BET 등을 이용하여 비교분석 하였다.