• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.569-572
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• 2003

Titanium dioxide ($TiO_2$) nanoparticles were prepared by the oxidation of titanium tetrachloride ($TiCl_4$) in a diffusion flame reactor. The average diameter of particles was 15 to 30 nm and mass fraction of anatase ranged from $40\;to\;80\%$. Effects of particle size and phase composition of those $TiO_2$ nanoparticles on photocatalytic properties such as decomposition of methylene blue and bacteria gas were investigated. The degree of decomposition of methylene blue by the $TiO_2$ nanoparticles under the illumination of the black light was directly proportional to the anantase mass fraction, but inversely to the particle size. The decomposition of bacteria by the $TiO_2$ nanoparticles under the illumination of the fluorescent light showed the same trend as in the case of the methylene blue.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.545-547
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• 2009

An immiscible Si/Sn (=7/3 by volume) powder mixture was subjected to simple grinding and subsequent leaching process to give Sn nanopowder reinforced or dispersed in Si powder. Crystallite and their agglomerates of Si were ca. 15 nm and 100 nm, respectively. Sn remained at 4.5 vol% in Si powder after aqueous HCl leaching, dispersively occluded in Si matrix as confirmed by ICP analysis and cross sectional TEM observation.

• Journal of Powder Materials
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• v.13 no.6 s.59
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• pp.432-438
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• 2006

Aluminum nitride (AlN) nanopowders with low degree of agglomeration and uniform particle size were synthesized by carbothermal reduction of alumina and subsequent direct nitridization. Boehmite powder was homogeneously admixed with carbon black nanopowders by ball milling. The powder mixture was treated under ammonia atmosphere to synthesize AlN powder at lour temperature. The effect of process variables such as boehmite/carbon black powder ratio, reaction temperature and reaction time on the synthesis of AlN nanopowder was investigated.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2004.11a
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• pp.80-81
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• 2004

The results obtained are summarized as follows; (1) Boehmite produced in the high temperature and acid region showed a nano fibrous shape with several nm in diameter and several hundreds nm in length having high specific surface areas with a maximum value of $409m^2/g$. (2) In order to obtain nano fibrous boehmite with high surface areas from nano metal powder, the hydrolysis reaction should be done at a high temperature over $50^{\circ}C$, high acidity under pH 6, and terminated before a transition to the bayerite phase.

• Journal of Powder Materials
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• v.19 no.4
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• pp.297-303
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• 2012

In this study, voltammetry system for realizing high sensitivity nano-labeled sensor of detecting heavy metals was designed, and optimal system operating conditions were determined. High precision digital to analog converter (DAC) circuit was designed to control applied unit voltage at working electrode and analog to digital converter (ADC) circuit was designed to measure the current range of $0.1{\sim}1000{\mu}A$ at counter electrode. Main control unit (MCU) circuit for controlling voltammetry system with 150 MHz clock speed, main memory circuit for the mathematical operation processing of the measured current value and independent power circuit for analog/digital circuit parts to reduce various noise were designed. From result of voltammetry system operation, oxidation current peaks which are proportional to the concentrations of Zn, Cd and Pb ions were found at each oxidation potential with high precision.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.47-53
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• 2003

자발착화연소법과 분무열분해법을 동시에 적용한 초음파분무연소법을 이용하여 40~50nm 크기를 갖는 결정성 ZnO 분말을 합성하였다. 또한 바리스터로의 응용을 위해 Bi, Sb, Co, Mn을 초기출발원료인 Zn-nitrate에 첨가하여 복합조성의 ZnO계 바리스터 분말을 합성하였다. 합성된 바리스터의 분말을 성형 및 소결하여 전기적 특성을 관찰한 결과 Co를 첨가한 분말보다 Mn을 첨가한 분말에서 우수한 전기적 특성을 나타내었다.

• 연구논문집
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• s.33
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• pp.123-135
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• 2003

Using the residence time calculated by computer simulation for temperature and gas velocity distribution in CVC reactor, the kinetics on the formation of $TiO_2$ nano powder was analyzed for coagulation process, After abrupt increase of particle size at initial growth stage (< 0.2 $\mus$ ), the particle grew in proportion of cubic root to time. The numerically calculated particle sizes well agreed with the experimental results. However, the coarse rutile $TiO_2$ powders having the particle size of over 40 nm were formed on the surface of quratz rod in the reactor. it is thought that the fine anatase particles condensed on quratz rod were sintered in a heated CVC reactor to grow and transform to coarse rutile phase, and the critical size for phase transformation anstase-to-rutile was around 25 nm tn this study.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1331-1332
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• 2006

The present investigation has attemped to optimize hydrogen reduction process for the mass production of Fe-8wt%Ni nanoalloy powder from ball milled $Fe_2O_3-NiO$ powder. In-situ hygrometry study was performed to monitor the reduction behavior in real time through measurement of water vapor outflowing rate. It was found that the reduction process can be optimized by taking into account the apparent influence of water vapor trap in the reactor on reduction kinetics which strongly depends on gas flow rate, reactor volume and reduction.

• 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.6 no.1
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• pp.75-80
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• 1999

The formation of $n-TiO_2$ powder by oxidation of Ti-ethoxied vapor in a flat flame burner reactor maintained under 20 torr has been studied. The produced powder were characterized in terms of crystal structure, chemical composition by XRD and TEM. The results showed that the powder consisted of loose agglomerated anatase and rutile particles and their size were about 10 nm and 20 nm, respectively. In the course of synthesis, changes of the flame color were happened to each condition during heating up the bubbler. The flame color transition phenomena reveled that a critical precursor delivery rate was needed for the powder formation (obtainable powder yield). The critical precursor delivery rate was estimated by a simple function of the bubbler temperature and the carrier gas flow rate. The critical precursor delivery rate was reviewed as an important variable of the nanopowder synthesis.