• 농업생명과학연구
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• 제44권4호
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• pp.29-43
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• 2010

The numerical analysis by using CFX 11.0 commercial code was done for proper design of the heat exchanger. The present experimental studies were also conducted to investigate the effects of circulating solid particles on the characteristics of fluid flow, heat transfer and cleaning effect in the fluidized bed vertical shell and tube type heat exchanger with counterflow, at which a variety of solid particles such as glass ($3mm{\Phi}$), aluminum ($2{\sim}3mm{\Phi}$), steel ($2{\sim}2.5mm{\Phi}$), copper ($2.5mm{\Phi}$) and sand ($2{\sim}4mm{\Phi}$) were used in the fluidized bed with a smooth tube. Seven different solid particles have the same volume, and the effects of various parameters such as water flow rates, particle diameter, materials and geometry were investigated. The present experimental and numerical results showed that the flow velocity range for collision of particles to the tube wall was higher with heavier density solid particles, and the increase in heat transfer was in the order of sand, copper, steel, aluminum, and glass. This behavior might be attributed to the parameters such as surface roughness or particle heat capacity.

• 한국분말재료학회지
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• 제9권6호
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• pp.433-440
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• 2002

Synthesis and compaction of Al-base nano powders by pulsed discharge method were investigated. The aluminum based powders with 50 to 200 nm of diameter were produced by pulsed wire evaporation method. The powders were covered with very thin oxide layer. The perspective process for the compaction and sintering of nanostructured metal-based materials stable in a wide temperature range can be seen in the densification of nano-sized metal powders with uniformly distributed hard ceramic particles. The promising approach lies in utilization of natural uniform mixtures of metal and ceramic phases, e.g. partially oxidized metal powders as fabricated in our synthesis method. Their particles consist of metal grains coated with oxide films. To construct a metal-matrix material from such powder, it is necessary to destroy the hard oxide coatings of particles during the compaction process. This goal was realized in our experiments with intensive magnetic pulsed compaction of aluminum nanopowders passivated in air.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.708-709
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• 2006

New Al-based alloys with very high ultimate tensile strength were developed in high Al concentration range of 91-95 at.% for Al-Fe-Cr-Ti-M (M: Co and Mo) systems and Al-Fe-Cr-Mo-Ti-Co system by the dispersion of nanoscale quasicrystalline particles in Al phase. The effect of adding elements, M was discussed in the viewpoint of stability of super-cooled liquid state and formation ability of quasicrystalline phase. The P/M Al-Fe-Cr-Ti-M alloys with dispersed nanoscale quasicrystalline particles exhibited ultimate tensile strength of 350MPa at 573K and 200MPa at 673K.

• Nuclear Engineering and Technology
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• 제45권7호
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• pp.979-986
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• 2013

Uranium metal particle dispersion plates have been proposed as targets for Molybdenum-99 (Mo-99) production to improve the radioisotope production efficiency of conventional low enriched uranium targets. In this study, uranium powder was produced by centrifugal atomization, and miniature target plates containing uranium particles in an aluminum matrix with uranium densities up to 9 $g-U/cm^3$ were fabricated. Additional heat treatment was applied to convert the uranium particles into UAlx compounds by a chemical reaction of the uranium particles and aluminum matrix. Thus, these target plates can be treated with the same alkaline dissolution process that is used for conventional $UAl_x$ dispersion targets, while increasing the uranium density in the target plates.

• 상하수도학회지
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• 제19권2호
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• pp.161-172
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• 2005

Recently, water treatment methods utilizing microbubbles such as DAF and EF are gaining interest and being studied. Current study is focused on the fundamental research of electroflotation by examining the characteristics of microbubbles and particles. The objects of this research consist of two things; (1) theoretical modeling of microbubble-particle collision, (2) the experimental investigation of removal efficiency of turbidity in electroflotation. From investigation, the mechanism of electroflotation can be explained not only by the characteristics of microbubbles and particles but also the chemistry of aluminum dissolved from aluminum electrode during the electroflotation experiment.

• 한국결정성장학회지
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• 제27권1호
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• pp.18-21
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• 2017

본 연구에서는 homogeneous precipitation method를 통하여 구형의 단분산(monodispersed) YAG : $Ce^{3+}$를 합성했다. 단분산 YAG : $Ce^{3+}$의 전구체를 합성하는 과정에서 aluminum ion들이 먼저 석출되어 aluminum 화합물을 형성하고 후에 yttrium 화합물들이 aluminum 화합물들의 표면에서 석출된다. 합성된 전구체를 파우더형태로 얻기 위해 건조과정을 거치는데, oven에서 건조했을 때 보다 동결건조기에서 건조했을 때 비교적 구형의 단분산 YAG : $Ce^{3+}$ 입자를 얻을 수 있었다. 하소 과정에서 공정을 진행하는 온도로서 $1100^{\circ}C$와 $1200^{\circ}C$를 비교해 보았다. 실험 결과 $1200^{\circ}C$의 온도로 상압에서 6시간 동안의 하소 과정을 진행하였을 때 400~500 nm 입자크기를 가진 단분산된 구형의 나노 YAG : $Ce^{3+}$ 입자가 합성되었다.

• Bulletin of the Korean Chemical Society
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• 제16권9호
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• pp.808-810
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• 1995

A strong SERS effect has been observed on silver surfaces which were prepared by Ag deposition in anodic aluminum oxide nanotemplates and subsequent partial removal of the oxide layers. The advantage of these surfaces for SERS studies is that the controlled size and dispersion of Ag particles can be achieved.

• 한국분말재료학회지
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• 제10권3호
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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 Pharmaceutical Investigation
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• 제18권4호
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• pp.175-180
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• 1988

The role and effect of aluminum tristearate in microencapsulation were investigated based on the dispersion system of ethambutol hydrochloride in acetone-liquid paraffin. Eudragit RS was used as a wall-forming material. Eudragit RS microcapsules prepared using aluminum tristearate were uniform, free-flowing particles. The phase diagram of ethambutol hydrochloride-Eudragit RS-aluminum tristearate indicated that spherical microcapsules ranging from 250 to 1400 ${\mu}m$ in diameter could be prepared only in a very limited region. Instrumental analysis using an energy dispersive-type X-ray microanalyser and a scanning electron microscope showed that aluminum tristearate was localized near the surface of microcapsules. From these results, it was presumed that aluminum tristearate reduced the phase tension between Eudragit microcapsules and liquid paraffin. The dissolution rates of ethambutol hydrochloride from Eudragit RS microcapsules were consideraly lower than those from ethambutol hydrochloride powders and decreased as the amount of aluminum tristearate decreased.

• 구강회복응용과학지
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• 제29권1호
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• pp.69-79
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• 2013

본 연구의 목적은 각각 다른 표면처리를 한 지르코니아를 레진시멘트로 접착한 후 전단결합강도를 평가, 비교하는 것이다. 디스크 모양의 산화 지르코늄(3-TZP, Kyoritsu, Tokyo, Japan) 시편 120 개를 다음과 같이 표면처리 하였다. (1)110 ${\mu}m$ 산화 알루미나 분사 처리 (2)Silica coating(RocatecTM, 3M ESPE) (3)처리하지 않음 시편을 한 군당 10 개씩 총 6 개군으로 나누어 두 개의 지르코니아 시편을 자가 접착형 레진 시멘트(RelyX U-200, 3M ESPE)로 합착하였다. (1)처리하지 않음/처리하지 않음 (2)처리하지 않음/110 ${\mu}m$ 산화 알루미나 분사처리 (3)처리하지 않음/Silica coating (4)110 ${\mu}m$ 산화 알루미나 분사 처리/110 ${\mu}m$ 산화 알루미나 분사 처리 (5)110 ${\mu}m$ 산화 알루미나 분사 처리/Silica coating (6)Silica coating/Silica coating. 각 군의 전단결합강도를 만능시험기로 측정하였다. 표면처리에 따른 결합강도의 차이를 살펴보기 위해 일원변량분석(One-way ANOVA)을 이용하고 사후 분석으로 Tukey HSD test를 실시하였다. Silica coating을 한 두 개의 시편을 접착한 군이 가장 높은 결합 강도를 보였다(P<0.05). 표면 처리하지 않은 시편을 접착한 군과 두 개의 시편 모두 알루미나 분사 처리한 시편을 접착한 군은 서로 간에 유의한 차이를 보이지 않았으며, 그 외의 군에 비해서는 유의하게 낮았다(P<0.05). 본 연구의 결과에 따르면 Silica coating은 자가중합형 레진시멘트를 이용하여 접착한 두 지르코니아 간의 결합을 증진시키는데 효과적이었다.