• 한국분말재료학회지
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• 제8권3호
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• pp.157-162
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• 2001

An optimum route to fabricate the ferrous alloy dispersed $Al_2O_3$ nanocomposites such as $Al_2O_3$/Fe-Ni and $Al_2O_3$/Fe-Co with sound microstructure and desired properties was investigated. The composites were fabricated by the sintering of powder mixtures of $Al_2O_3$ and nano-sized ferrous alloy, in which the alloy was prepared by solution-chemistry routes using metal nitrates powders and a subsequent hydorgen reduction process. Microstructural observation of reduced powder mixture revealed that the Fe-Ni or Fe-Co alloy particles of about 20 nm in size homogeneously surrounded $Al_2O_3$, forming nanocomposite powder. The sintered $Al_2O_3$/Fe-Ni composite showed the formation of Fe$Al_2O_4$ phase, while the reaction phases were not observed in $Al_2O_3$/Fe-Co composite. Hot-pressed $Al_2O_3$/Fe-Ni composite showed improved mechanical properties and magnetic response. The properties are discussed in terms of microstructural characteristics such as the distribution and size of alloy particles.

• 대한금속재료학회지
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• 제48권6호
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• pp.543-550
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• 2010

This paper investigated the synthesis conditions of nano-sized $TiO_2$ powder in a hydrothermal process at a temperature range of $100{\sim}180^{\circ}C$ considering the precipitation agent, precipitation pH, reaction temperature and time. Titanium hydroxide formed by $NH_4OH$ exhibited a lower crystallization temperature than that by NaOH and formed less aggregated $TiO_2$ particles. As the precipitation pH increased above 8, the shape of the particles changed from spherical to needle form, which appeared to be caused by dissolution and re-precipitation of the titanium hydroxide in an alkali environment.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.405-406
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• 2005

A theoretical investigation of the solid-phase mechanochemical synthesis of nano-sized target product on the basis of dilution of the initial powdered reagent mixture by another product of an exchange reaction is presented. On the basis of the proposed 3-mode particle size distribution in mechanically activated mixture, optimal molar ratios of the components in mixture are calculated, providing the occurrence of impact-friction contacts of reagent particles and excluding aggregation of the nanosized particles of the target reaction product. Derivation of kinetic equations for mechanochemical synthesis of nanoscale particles by the final product dilution method in the systems of exchange reactions is submitted. On the basis of obtained equations the necessary times of mechanical activation for complete course of mechanochemical reactions are designed. Kinetics of solid phase mechanosynthesis of nano-TlCl by dilution of initial (2NaCl + $Tl_2SO_4$) mixture with the exchange reaction product (diluent, $zNa_2SO_4$, $z=z^*=11.25$) was studied experimentally. Some peculiar features of the reaction mechanism were found. Parameters of the kinetic curve of nano-TlCl obtained experimentally were compared with those for the model reaction KBr + TlCl + zKCl = (z + 1) KCl + TlBr ($z=z_l^*=13.5$), and for the first time the value of mass transfer coefficient in a mechanochemical reactor with mobile milling balls was evaluated. Dynamics of the size change was followed for nanoparticle reaction product as a function of mechanical activation time.

• 한국자동차공학회논문집
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• 제15권6호
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• pp.144-150
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• 2007

In recent years, the particle number emissions rather than particulate mass emissions in automotive engine have become the subject of controversial discussions. Recent results from the health effects studies imply that it is possible that particulate mass does not properly correlated with the variety of health effects attributed to diesel exhaust. So, the concern is instead now focusing on nano-sized particles emitted from I. C. engine. This study has been performed for the better understanding about the engine nano-particle for 3-measurement systems with different measuring principle. Firstly, EEPS is a newly introduced instrument for size distribution measurement of engine exhaust particles. It can measure nano-particles with an adequate resolution and in real time. In this study, the characteristics of EEPS were compared with ELPI and SMPS. As a research results, EEPS showed a same effect of engine load on the size distribution with ELPI and SMPS. But the quantitative results of EEPS were more similar to SMPS than ELPI, because the EEPS and SMPS use a same principle for classifying particles by size. The capability for transient measurement of EEPS was equivalent to that of ELPI.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.57-58
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• 2009

The dynamics of nano or micro sized-particles in liquid crystal (LC) medium under an external electric field is of theoretical and technological interest. A fullerene of 10 wt% was doped into the LC medium and its electric field induced motion was controlled by both in-plane and vertical electric fields. In the proposed device, pixel electrode I and pixel electrode II were designed consecutively on the bottom substrate and common electrode on the top of the substrate. When the electric field was applied, the fullerenes start to move in direction of applied electric field. The dark, grey and white states in the proposed device can be obtained by suitable combination of the polarity of applied electric field at pixel electrode I, pixel electrode II and common electrode. The dynamical motions of fullerene particles in LC medium suggest that fullerene can be designed for electronic-paper like displays.

• 한국전기전자재료학회논문지
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• 제22권1호
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• pp.86-92
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• 2009

We fabricated the charged particle type display using opposite-charged two toner particles. The particles were composed of polymer, colorant($TiO_2$, carbon black) and external additives(nano-sized silica and so on). In fabrication process we controlled the putting layers of this toner particles on the inner panel. To get the effect of number of layers ($1{\sim}3$), we measured the threshold, driving and breakdown voltages, reflectivity, viewing angle, and color characteristics using RT-300 anisotropic scattering system. We ascertained that these voltages are increased with increasing of layers of particles. Cell gap between electrodes must be enlarged with increment of layers and the size of particles. The lumping phenomena of particles at near of the rib observed by optical system with same CIE values.

• 자원리싸이클링
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• 제27권2호
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• pp.24-31
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• 2018

본 연구에서는 폐 ITO 타겟을 염산에 용해시킴으로써 인듐-주석 복합 산 용액을 제조하여 원료용액으로 사용하였다. 이 원료용액으로부터 분무열분해 공정에 의하여 평균입도 30 nm 이하의 ITO 분체를 제조하였다. 또한 본 연구에서는 인듐-주석 산화물(ITO) 형성을 위한 열역학적 수식들을 확립하였다. 반응온도가 $800^{\circ}C$로부터 $900^{\circ}C$로 증가됨에 따라 평균입도 30 nm 이하인 나노입자들이 응집되어 있는 액적 형태의 비율 및 크기는 감소하는 반면 표면 조직은 더욱 치밀해짐을 알 수 있었다. 반응온도가 $800^{\circ}C$인 경우에는 생성된 분체의 평균입도는 약 20 nm이었으며, 현저한 소결 현상은 나타나지 않았다. 한편, 반응온도가 $900^{\circ}C$인 경우에는 노즐에 의하여 미립화되는 액적의 분열 현상은 $800^{\circ}C$의 경우보다 심하게 나타났으며 액적 형태의 비율은 현저하게 감소하였다. 형성된 입자들의 평균 입도는 약 25 nm로서 $800^{\circ}C$의 경우보다 약간 증가하였다. 반응온도에 관계없이 ITO 입자들은 단결정으로 구성되어 있었다. XRD 분석 결과 분무열분해 공정에 의하여 염화물 상은 전혀 존재하지 않았으며 오직 ITO 상만이 형성되었음을 알 수 있었다. 반응온도가 $800^{\circ}C$로부터 $900^{\circ}C$로 증가함에 따라 비표면적은 약 30% 감소하였다.

• 한국표면공학회지
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• 제50권3호
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• pp.212-218
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• 2017

$Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrite powders were prepared by self-propagating high temperature synthesis followed by classifying with an ultrasonic wet-magnetic separation unit to get high pure nano-sized particles. The $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrites were well formed by using several powders like iron, nickel oxide, zinc oxide and magnesium oxide at 0.1 MPa of oxygen pressure. The ultrasonic wet-magnetic separation of pre-mechanical milled ferrite powders resulted in producing the powders with average size of 800 nm. The addition of a surfactant during the wet-magnetic separation process improved productivity more than twice. The coercive force, maximum magnetization and residual magnetization of the $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ nano-powders with 800 nm size were 3651 A/m, $53.92Am^2/kg$ and $4.0Am^2/kg$, respectively.

• 동력기계공학회지
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• 제18권6호
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• pp.174-179
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• 2014

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the specific wear rate under the various applied load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and followed by scanning electron microscope observations. The presence of silica filler in epoxy composites was demonstrated significant influence on the friction and wear behavior of epoxy nanocomposites. With the incorporation of silica filler into the epoxy matrix, reduction of the coefficient of friction and specific wear rate were identified. Wear mechanism was discussed by analyzing the worn surface by scanning electron microscope as well.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.791-796
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• 2017

본 연구에서는 알루미늄 입자 크기에 따른 파라핀 혼합연료의 연소 특성에 관한 실험을 수행하였다. 평균 입도 100 nm 및 $8{\mu}m$ 크기의 알루미늄 입자와 Sasol사의 마이크로크리스탈린 파라핀 왁스(Sasol 0907)를 이용하여 연소실험을 수행하였고 순수 파라핀과 알루미늄 입자 5 wt%를 첨가한 파라핀 혼합연료의 후퇴율과 압력선도, 특성배기속도 등을 비교하였다. 마이크로 입자의 첨가는 산화제 유속이 증가할수록 후퇴율을 향상시켰으나 나노 입자의 첨가는 후퇴율이 감소하는 경향을 보였다.