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수소 확산화염에서 화염온도가 TiO<sub>2</sub> 나노입자의 합성에 미치는 영향
이교우,이승복,이종수,배귀남,Lee Gyo Woo,Lee Seung Bok,Lee Jongsoo,Bae Gwi-Nam 대한기계학회 2005 大韓機械學會論文集B Vol.29 No.9
In this work, $TiO_2$ nanoparticles were synthesized using a N2-diluted hydrogen coflow diffusion flame. The effects of flame temperature on the crystalline structure and the size of formed nanoparticles were investigated. The maximum centerline temperature of the flame ranged from 1,920K for $H_2-only$ flame to 863k for $81\%\;N_2-diluted$ flame. The morphology and the crystal structure of $TiO_2$ nanoparticles were analyzed by a TEM and a XRD, respectively. The particle size distribution was also measured by using a scanning mobility particle size. (SMPS). The mean particle diameter was calculated from the TEM images depended on the flame temperature, having minimum at about 1,look. Based on the SMPS measurements, the mean particle diameter of $TiO_2$ nanoparticles at flame temperatures > 1,300K was smaller than that at flame temperatures < 1,300K. From the XRD analysis, it was evident that the anatase fraction increased with decreasing the flame temperature. The portion of anatase phase in $TiO_2$ nanoparticles might be greater than $80\%$ when the flame temperature was lower than 1,000K.
에틸렌 역확산화염을 열원으로 사용하여 촉매금속 기판 상에 합성한 탄소나노튜브와 탄소나노섬유
이교우(Gyo Woo Lee),정종수(Jongsoo Jurng),강경태(Kyung-Tae Kang),황정호(Jungho Hwang) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
Synthesis of carbon nanotubes and nanofibers on a catalytic metal substrate, using an ethylene fueled inverse diffusion flame, was investigated. Multi-walled carbon nanotubes, with diameters of 20 - 60㎚, were formed on the substrate coated with nickel-nitrate in the region of 5 - 6㎜ from the flame center along the radial direction. The gas temperature for this region was ranging from about 1400 to 900K. Nickel particles originated from the coated nickel-nitrate on the substrate were the major catalyst for the formation of the nanomaterials. HR-TEM and Raman spectrum revealed that synthesized carbon nanotubes had multi-walled structures with some defective graphite layers at walls.
화염법으로 제조된 감마-Al<sub>2</sub>O<sub>3</sub> 나노입자의 화염조건에 따른 입자특성 연구
이교우(Gyo Woo Lee) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.5
본 논문은 수소를 연료로 하는 확산화염을 이용하여 알루미나 나노입자를 합성할 때, 합성되는 알루미나 나노입자의 특성에 미치는 화염온도의 영향을 조사하였다. 합성된 나노입자의 특성을 전자현미경 이미지, 결정 구조 분석, 비표면적과 기공의 크기 분석, 화염온도 측정 등의 여러 특성분석 방법으로 조사하였다. 사용된 화염의 중심축 최고온도는 산화제의 산소농도가 19, 21, 30, 47%인 각각의 실험조건에서 1507.8K, 1593.8K, 1753.1K, 1998.7K으로 측정되었다. SEM 이미지 분석 및 BET 비표면적 측정을 통해서는 47% 산소농도인 경우 에는 50 nm 수준의 독립적인 구형입자가 생성되었음을 확인할 수 있었으며, 19%와 21%의 경우에는 응집된 상태의 20-30 nm 수준의 입자를 볼 수 있었다. XRD 결과에서는 감마(γ)-알루미나가 주를 이루는 것으로 판단되었다. 이상의 결과를 바탕으로 촉매 담체로 사용하기 위한 알루미나 나노입자를 연소합성 하기 위한 가장 적절한 조건으로 실험했던 네 경우 중에서는 산화제의 산소농도가 21%인 두 번째 경우를 선택할 수 있었다. In this study, γ-Al<sub>2</sub>O<sub>3</sub> nanoparticles were synthesized by using coflow hydrogen diffusion flames. The synthesis conditions were varied with using several oxygen concentrations in the oxidizing air. The particle characteristics of the flame-synthesized Al<sub>2</sub>O<sub>3</sub> nanoparticles were determined by examining the crystalline structure, shape, and specific surface area of the nanoparticles. The measured maximum centerline temperature of the flames ranged from 1507.8 K to 1998.7 K. The morphology and crystal structure of the Al<sub>2</sub>O<sub>3</sub> nanoparticles were determined from SEM images and XRD analyses, respectively. The particle sizes were calculated from measured BET specific surface areas and ranged from 25 nm to 52 nm. From XRD analyses, it was inferred that a large number of the synthesized nanoparticles were γ-Al<sub>2</sub>O<sub>3</sub> nanoparticles including θ-Al<sub>2</sub>O<sub>3</sub> nanoparticles.
TTIP를 전구체로 사용하는 TiO₂ 나노입자의 연소합성 및 열처리에 따른 상변환 특성
이교우(Gyo Woo Lee),강희용(HeeYong Kang),김민수(Min Soo Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
In this article, TiO₂ nanoparticles were synthesized by using O₂-enriched coflow, hydrogen, diffusion flames. We investigated the thermal stability of the flame-synthesized TiO₂ nanoparticles by examining the crystalline structures of the nanoparticles. Also, the results were compared with those of commercial P-25 nanoparticles. TiO₂ nanoparticles, which were spherical with diameters approximately ranging from 30 to 60㎚, were synthesized. From the XRD analyses, about 96wt% of the synthesized nanoparticles were anatase-phase. After the heat-treatment at 800℃ for 30 minutes, the synthesized TiO₂ nanoparticles showed no significant changes of their shapes and crystalline phases. On the other hand, most of the commercial particles sintered with each other and changed to the rutile-phase. Based on the result of XRD analysis it is believed that the flame-synthesized TiO₂ nanoparticles have higher thermal stability at 800℃ than the commercial particles.