• Korean Chemical Engineering Research
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• 제49권6호
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• pp.752-757
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• 2011

암모니아수와 zinc acetate로부터 액상 수열합성법에 의한 ZnO의 제조에 있어 반응온도, 반응물의 농도와 혼합방법, 용액의 pH 등 반응조건에 따른 ZnO 입자의 형상과 입자분포 등 제조특성을 고찰하고, UV 조사하에 tartrazine의 광분해를 측정하여 합성된 ZnO의 광촉매로서의 성능을 확인하였다. 반응용액의 pH가 높을수록 ZnO 입자의 평균 크기는 증가하였고, zinc acetate의 농도가 증가할수록 그리고 반응온도가 증가할수록 입자의 크기는 감소하였다. 반응용액의 혼합시 암모니아수 주입 후에 zinc acetate를 첨가하였을 경우 더 작은 입자를 얻을 수 있었다. 최소 크기의 ZnO 입자의 생성을 위한 최적 조건은 용액의 pH 11.2, zinc acetate의 농도 0.6 M, 반응온도 $90^{\circ}C$였으며, 입자 평균크기는 3.133 ${\mu}$m이었다. 합성온도 $80^{\circ}C$, zinc acetate 농도 1.0M 및 반응용액의 pH 11.2의 조건에서 합성된 ZnO에 의한 tartrazine의 광촉매 분해는 분해시간 60분에서 약 97%의 분해율을 보였다.

• 한국응용과학기술학회지
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• 제34권4호
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• pp.705-716
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• 2017

본 연구에서는 0.5, 1.0, 1.5 wt%의 $TiO_2$를 함유하는 인듐-티타늄 수산화물을 졸 및 염기 첨가에 의해 얻었고, $200^{\circ}C$와 $500^{\circ}C$에서 겔화 과정을 통해 ITiO(Indium Titanate Oxide)를 얻었다. $200^{\circ}C$에서 겔화 과정 후 얻어지는 ITiO 입자가 작아서 조밀성이 있는 ITiO 타겟을 제조하였다. 0.5, 1.0, 1.5 wt%의 $TiO_2$를 함유하는 ITiO 타겟을 스퍼터링하여 ITiO 박막을 유리판위에 제작하여 비저항, 전하 이동도, 캐리어 농도를 조사하였다. 이들 박막 중에서 산소 조성이 0.4 %인 조건에서 0.5 wt% 중량% $TiO_2$를 함유하는 ITiO 타겟으로부터 제작된 ITiO 박막이 가장 낮은 비저항, 가장 큰 전하이동도 및 가장 낮은 캐리어 농도를 보임을 알 수 있었고, 얻어진 ITiO 박막의 광투과율을 측정하여 적외선 영역에서 광투과율이 ITO(Indium Tin Oxide) 박막에 비해 현저히 증가함을 발견하였다.

• Journal of Electrochemical Science and Technology
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• 제6권1호
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• pp.16-25
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• 2015

Transition metal oxide nanocrystalline materials are playing major role in energy storage application in this scenario. Nickel oxide is one of the best antiferromagnetic materials which is used as electrodes in energy storage devices such as, fuel cells, batteries, electrochemical capacitors, etc. In this research work, nickel oxide nanoparticles were synthesized by combustion route in presence of organic fuels such as, glycine, glucose and and urea. The prepared nickel oxide nanoparticles were calcined at 600℃ for 3 h to get phase pure materials. The calcined nanoparticles were preliminarily characterized by XRD, particle size analysis, SEM and EDAX. To prepare nickel oxide electrode materials for application in supercapacitors, the calcined NiO nanoparticles were mixed with di-methyl-acetamide and few drops of nafion solution for 12 to 16 h. The above slurry was coated in the graphite sheet and dried at 50℃ for 2 to 4 h in a hot air oven to remove organic solvent. The dried sample was subjected to electrochemical studies, such as cyclic voltammetry, AC impedance analysis and chrono-coulometry studies in KOH electrolyte medium. From the above studies, it was found that nickel oxide nanoparticles prepared by combustion synthesis using glucose as a fuel exhibited resulted in low particle diameter (42.23 nm). All the nickel oxide electrodes have shown better good capacitance values suitable for electrochemical capacitor applications.

• 한국추진공학회지
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• 제22권3호
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• pp.65-71
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• 2018

황색 산화철과 적색 산화철을 적용한 추진제의 초기점도는 각각 5.4, 5.6 kps로 특이한 차이점이 없었다. 또한 황색 산화철을 첨가한 물질의 열분해 속도가 적색 산화철을 첨가한 것 보다 빠르게 진행되며, 특히 고온 고압에서의 압력지수가 18% 낮은 것을 확인하였다. 황색 산화철을 적용한 추진제의 산화제 비율 변화에 따른 점도를 비교하면 큰 입자/작은 입자 비율 71%일 때 초기점도가 가장 낮았다.

• 대한기계학회논문집
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• 제15권2호
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• pp.618-629
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• 1991

The purpose of this experiment is to understand the distribution of coal particles inside CWM droplet which is believed to be a very important factor controlling the flame stability. CWM slurry is atomized by an air assisted twin fluid nozzle. An experimental rig is designed and fabricated. The mean size of coal particle distribution in CWM slurry, atomizing air pressure, coal particle loading in slurry and sampling position inside spray are main experimental variables. The atomized CWM droplets are sampled on the thin white layer of magnesium oxide by the emergency sampling shutter. The sampled coal particles on magnesium oxide layers are collected into test tubes and dispersed completely by Ultra-Sonicator. The size distribution of coal particles inside droplets are measured by Coulter Counter. The presence of coal particle inside the impressions of droplets on magnesium oxide layer are investigated by photo technique. There are quite many droplets which do not have any coal particles. Those are just water droplets, not CWM droplets. The population ratio of droplets without coal particles to toal number of droplets is strongly affected by the mean size of coal particle distribution in slurry and this ration becomes bigger number as the mean size of coal particles be larger. The size distribution of coal particles inside CWM droplets is not even and depends on the size of droplet. Experimental results show that the larger CWM droplets has droplets has bigger mean value of particle size distribution. This trend becomes more evident as the atomizing air pressure is raised and the mean size of coal particles in CWM slurry is bigger. That is, the distribution of coal particles inside CWM dropolets is very much affected by the atomizing air pressure and the mean size of pulverized coal particles in CWM slurry.

• 한국재료학회지
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• 제23권9호
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• pp.489-494
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• 2013

In this study, by using nickel chloride solution as a raw material, a nano-sized nickel oxide powder with an average particle size below 50 nm was produced by spray pyrolysis reaction. A spray pyrolysis system was specially designed and built for this study. The influence of nozzle tip size on the properties of the produced powder was examined. When the nozzle tip size was 1 mm, the particle size distribution was more uniform than when other nozzle tip sizes were used and the average particle size of the powder was about 15 nm. When the nozzle tip size increases to 2 mm, the average particle size increases to roughly 20 nm, and the particle size distribution becomes more uneven. When the tip size increases to 3 mm, particles with an average size of 25 nm and equal to or less than 10 nm coexist and the particle size distribution becomes much more uneven. When the tip size increases to 5 mm, large particles with average size of 50 nm partially exist, mostly consisting of minute particles with average sizes in the range of 15~25 nm. When the tip size increases from 1 mm to 2 mm, the XRD peak intensities greatly increase while the specific surface area decreases. When the tip size increases to 3 mm, the XRD peak intensities decrease while the specific surface area increases. When the tip size increases to 5 mm, the XRD peak intensities increase again while the specific surface area decreases.

• 한국재료학회지
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• 제21권12호
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• pp.690-696
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• 2011

In this study, nano-sized tin oxide powder with an average particle size of below 50 nm is prepared by the spray pyrolysis process. The influence of air pressure on the properties of the generated powder is examined. Along with the rise of air pressure from $0.1kg/cm^2$ to $3kg/cm^2$, the average size of the droplet-shaped particles decreases, while the particle size distribution becomes more regular. When the air pressure increases from $0.1kg/cm^2$ to $1kg/cm^2$, the average size of the dropletshaped particles, which is around 30-50 nm, shows hardly any change. When the air pressure increases up to $3kg/cm^2$, the average size of the droplet-shaped particles decreases to 30 nm. For the independent generated particles, when the air pressure is at $0.1kg/cm^2$, the average particle size is approximately 100 nm; when the air pressure increases up to $0.5kg/m^2$, the average particle size becomes more than 100 nm, and the surface structure becomes more compact; when the air pressure increases up to $1kg/cm^2$, the surface structure is almost the same as in the case of $0.5kg/cm^2$, and the average particle size is around 80- 100 nm; when the air pressure increases up to $3kg/cm^2$, the surface structure becomes incompact compared to the cases of other air pressures, and the average particle size is around 80-100 nm. Along with the rise of air pressure from $0.1kg/cm^2$ to $0.5kg/cm^2$, the XRD peak intensity slightly decreases, and the specific surface area increases. When the air pressure increases up to $1kg/cm^2$ and $3kg/cm^2$, the XRD peak intensity increases, while the specific surface area also increases.

• 대한기계학회논문집B
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• 제29권9호
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• pp.1065-1073
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• 2005

The thermal conductivity of water- and ethylene glycol-based nanofluids containing alumina $(Al_2O_3)$, zinc oxide (ZnO) and titanium dioxide $(TiO_2)$ nanoparticles is measured by varying the particle diameter and volume fraction. The transient hot-wire method using an anodized tantalum wire for electrical insulation is employed for the measurement. The experimental results show that nanofluids have substantially higher thermal conductivities than those of the base fluid and the ratio of thermal conductivity enhancement increases linearly with the volume fraction. It has been found that the ratio of thermal conductivity enhancement increases with decreasing particle size but no empirical or theoretical correlation can explain the particle-size dependence of the thermal conductivity. This work provides, for the first time to our knowledge, a set of consistent experimental data over a wide range of nanofluid conditions and can therefore serve as a basis for developing theoretical models to predict thermal conduction phenomena in nanofluids.

• 한국안전학회지
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• 제30권3호
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• pp.32-37
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• 2015

In the fields of plant layout optimization, the main goal is to minimize the construction cost including pipelines as satisfying all constraints such as safety and operating issues. However, what is the lacking of considerations in previous researches is to consider proper safety and maintenance spaces for a complex plant. Based on the mathematical programming, MILP(Mixed Integer Linear Programming) problems including various constraints can be formulated to find the optimal solution which is to achieve the best economic benefits. The objective function of this problem is the sum of piping cost, pumping cost and area cost. In general, many conventional optimization solvers are used to find a MILP problem. However, it is really hard to solve this problem due to complex inequality and equality constraints, since it is impossible to use the derivatives of objective functions and constraints. To resolve this problem, the PSO (Particle Swarm Optimization), which is one of the representative sampling approaches and does not need to use derivatives of equations, is employed to find the optimal solution considering various complex constraints in this study. The EO (Ethylene Oxide) plant is tested to verify the efficacy of the proposed method.

• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.13-20
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• 2015

The self-cleaning properties of nano-zinc oxide on cotton fabrics have been investigated. The cotton fabric has been prepared by pad-dry method. The nano-zinc oxide was encapsulated in the polystyrene particle by mini-emulsion process prior used. The loading amount of zinc oxide particles into the mini-emulsion were various from 1% wt to 40%wt. The particles sizes of ZnO-encapsulated polystyrene mini-emulsion were determined using dynamic light scattering. It was showed that the particle size of the mini-emulsion was in the range of 124-205 nm. The topography and morphology of ZnO-encapsulated polystyrene which coated on cotton fabrics was observed using scanning electron microscopy. The crystal structure of ZnO-coated on cotton fabrics was explored by X-ray diffraction spectroscopy. The photocatalytic activities of zinc oxide were present through the self-cleaning properties. The presents of the zinc oxide on cotton fabrics significantly showed the improving of the self-cleaning properties under UV radiation.