• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1211-1212
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• 2006

The electrophoretic deposition process of Ni nano-particles was employed for self-repairing of heat exchanger tubes. For electrophoretic deposition of Ni nano-particles on pitted Ni alloy specimen, a constant electric field of 100 V $cm^{-1}$ was applied to the specimen for 180 s in Ni-dispersed solution. It was found that as electrophoretic deposition proceeded, the size of the pit remarkably decreased due to the agglomeration of Ni nano-particles at the pit. This strongly suggests that the electrophoretic mobility of the charged particles is larger for the pit with a higher current value rather than outer surfaces with a lower current value.

• 한국분말재료학회지
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• 제14권4호
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• pp.238-244
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• 2007

The electrophoretic deposition process of Ni nano-particles in organic suspension was employed for self-repairing of heat exchanger tubes. For this purpose, Ni nano-particles prepared by levitational gas condensation method were dispersed into the solution of ethanol with the addition of dispersant Hypermer KD2. For electrophoretic deposition of Ni nano-particles on the Ni alloy specimen, constant electric fields of 20 and 100 V $cm^{-1}$ were applied to the specimen in Ni-dispersed solution. It was found that as electrophoretic deposition proceeds, the size of the pit or crack remarkably decreased due to the agglomeration of Ni nano-particles at the pit or crack. This strongly suggests that the electrophoretic mobility of the charged particles is larger for the damaged part with a higher current value rather than outer surfaces with a lower current value.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.623-623
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• 2008

• 한국대기환경학회지
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• 제27권6호
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• pp.681-691
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• 2011

The size distributions of smoke particles from fire are prerequisite for the studies on fire detection and adverse health effects. Above the flame of the fire, coagulation dominates and the smoke particles grow from 1 to 50 nm up to 100 to 3,000 nm, sizes ranging from the free-molecular regime to the continuum regime. The characteristics of the agglomeration of the smoke particles are well known, independently for each of the free-molecular and continuum regimes. However, there are not many systematic studies in the entire regime by the complexity of the mechanisms. The purpose of this work is to find the characteristics of the development of the size distribution of smoke particles by agglomeration in the entire size range covering the free-molecular regime, via transition regime, to the near-continuum and continuum regime for each variation of parameters such as fractal dimension, primary particle size and dimensionless coagulation time. In this work, the dynamic equation for the discrete-size spectrum of the particles was solved using a nodal method based on the modification of a sectional method. In the calculation, the collision frequency function for the entire regime, which is derived by using the concept of collision volume and general enhancement function, was applied. The self-preserving size distribution for the entire regime is compared with the ones for the free-molecular or continuum regimes for each variation of the parameters.

• 한국진공학회지
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• 제21권5호
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• pp.233-241
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• 2012

단결정 MgO (001) 기판에 DC 마그네트론 스퍼터로 하지층과 상지층으로 구성된 이중층을 증착, 열처리 온도와 시간을 고정시키고 이중층의 두께를 변화시켜 응집현상을 제어하여 자기구조화, 나노 구조화된 박막을 제작하였다. 진행한 실험에선 기존에 연구되었던 단층에서의 응집현상이 아닌 하지층과 상지층으로 구성된 이중층의 응집현상으로 나노 점을 형성하였다. 하지층은 Ti, Cr, Co 그리고 상지층은 Ag를 증착하였다. Atomic force microscopy를 통하여 하지층의 물질에 따라 나노 점의 형성 여부가 관찰되었고 형성된 나노 점의 형상이 다르게 나타난 것을 확인하였다. 결과적으로 이중층의 응집현상을 이용하여 나노 점을 제작할 때 가장 적합한 하지층의 물질은 Ti로 확인하였다. 또한 Ti/Ag 시료는 X-ray Diffraction 분광법을 통하여 Ag는 기판으로 사용된 MgO의 (001) 방향을 따라서 에피택셜하게 성장한 것을 확인하였다.

• 한국전기전자재료학회논문지
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• 제17권2호
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• pp.138-143
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• 2004

CMP (Chemical Mechanical Polishing) technology for global planarization of multilevel interconnection structure has been widely studied for the next generation devices. Among the consumables for CMP process, especially, slurry and their chemical compositions play a very important role in the removal rates and within-wafer non-uniformity (WIWNU) for global planarization ability of CMP process. However, CMP slurries contain abrasive particles exceeding 1 ${\mu}{\textrm}{m}$ size, which can cause micro-scratch on the wafer surface after CMP process. Such a large size particle in these slurries may be caused by particle agglomeration in slurry supply-line. In this work, to investigate the effects of agglomeration on the performance of oxide CMP slurry, we have studied an aging effect of silica slurry as a function of particle size distribution and aging time during one month. We Prepared and compared the self-developed silica slurry by adding of alumina powders. Also, we have investigated the oxide CMP characteristics. As an experimental result, we could be obtained the relatively stable slurry characteristics comparable to aging effect of original silica slurry. Consequently, we can expect the saving of high-cost slurry.

• 한국세라믹학회지
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• 제44권3호
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• pp.152-156
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• 2007

Tungsten carbide powder was synthesized by SHS (self-propagating high-temperature synthesis). Except $WO_{3}$, each concentration of raw material ($WO_{3},\;Mg,\;NaCl,\;Na_{2}CO_{3},\;C$) was investigated. Final product was characterized by XRD and SEM. X-ray data demonstrated that the $NaCl+Na_{2}CO_{3}$ combined mixture has superiority in the WC formation process. Single phase and submicrometer WC powder was synthesized at the temperature below $1600^{\circ}C$. The role of sodium salts in combustion process was discussed, and chemical mechanism of WC formation was proposed. WC powder prepared by salt-assisted combustion synthesis has a size $0.2{\sim}3\;{\mu}m$ and low agglomeration degree.

• 한국진공학회지
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• 제20권1호
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• pp.7-13
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• 2011

자기조립화된 Fe/Au 이중층 위에 $L1_0$형 구조를 갖는 FePd 나노 점을 성공적으로 제작하였다. AFM를 이용하여 초기에 편평한 Fe/Au 이중층 박막이 온도가 증가함에 따라서 응집되어 나노 점 구조로 변형되는 것을 확인하였다. 또한 형성된 이중층위에 FePd 다층막을 $300^{\circ}C$, $350^{\circ}C$, $400^{\circ}C$, $450^{\circ}C$에서 각각 증착하였다. 초격자 구조를 갖는 FePd 다층막의 표면형상은 응집현상에 의하여 자기조립화된 이중층의 형상과 유사하였다. XRD 측정결과, $350^{\circ}C$ 이상에서 열처리된 FePd 다층막은 $L1_0$형 구조를 갖는다는 것을 확인하였다. 그리고 박막두께에 따른 XPS 측정결과는 전체 박막의 화학적 조성이 증착순서와 일치하는 것을 보여주었다. 결과적으로 추가적인 식각공정 없이 화학적으로 규칙화된 FePd 초격자 나노 점의 제작에 성공하였다.

• 한국재료학회지
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• 제12권10호
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• pp.784-790
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• 2002

For mass product of nanocrystalline ZnO ultrafine powders, self-sustaining combustion process(SCP) and ultrasonic spray combustion method(USCM) were applied at the same time. Ultrasonic spray gun was attached on top of the vertical type furnace. The droplet was sprayed into reaction zone of the furnace to form SCP which produces spherical shape with soft agglomerate crystalline ZnO particles. To characterize formed particles, fuel and oxidizing agent for SCP were used glycine and zinc nitrate or zinc hydroxide. Respectively, with changing combustion temperature and mixture ratio of oxidizing agent and fuel, the best ultrasonic spray conditions were obtained. To observe ultrasonic spray effect, two types of powder synthesis processes were compared. One was directly sprayed into furnace from the precursor solution (Type A), the other directly was heated on the hot plate without using spray gun (Type B). Powder obtained by type A was porous sponge shape with heavy agglomeration, but powder obtained using type B was finer primary particle size, spherical shape with weak agglomeration and bigger value of specific surface area. 9/ This can be due to much lower reaction temperature of type B at ignition time than type A. Synthesized nanocrystalline ZnO powders at the best ultrasonic spray conditions have primary particle size in range 20~30nm and specific surface area is about 20m$^2$/g.

• 한국재료학회지
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• 제18권1호
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• pp.5-11
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• 2008

Thermally evaporated 10 nm-Ni/1 nm-Au/(30 nm-poly)Si structures were fabricated in order to investigate the thermal stability of Au-inserted nickel silicide. The silicide samples underwent rapid thermal annealing at $300{\sim}1100^{\circ}C$ for 40 seconds. The sheet resistance was measured using a four-point probe. A scanning electron microscope and a transmission electron microscope were used to determine the cross-sectional structure and surface image. High-resolution X-ray diffraction and a scanning probe microscope were employed for the phase and surface roughness. According to sheet resistance and XRD analyses, nickel silicide with Au had no effect on widening the NiSi stabilization temperature region. Au-inserted nickel silicide on a single crystal silicon substrate showed nano-dots due to the preferred growth and a self-arranged agglomerate nano phase due to agglomeration. It was possible to tune the characteristic size of the agglomerate phase with silicidation temperatures. The nano-thick Au-insertion was shown to lead to self-arranged microstructures of nickel silicide.