• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.1
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• pp.17-21
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• 2005

Shielded laser ablation system composed of laser system, image analyser, XYZ translator with motion controller, ablation chamber, manipulator and various optics was designed. Nd:YAG laser which can be tunable from 1064 nm to 266 m was selected as light source. CCD camera(< $\pm$200) was chosen to analyze a crater less than 50 un in diameter. XYZ translator was composed of three linear stage which can travel 50 w with a minimum movement of 1 um and motion controller. Before the performance test, each part of system was optically aligned. To perform the ablation test, the specimen was ablated by 50 um interval and observed by image analyser The shape of crater was almost round, indicating laser beam has homogeneous energy distribution. The resolution and magnification of image system were compatible with the design.

• Journal of Powder Materials
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• v.14 no.5
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• pp.281-286
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• 2007

Ordered $L1_0$ to FePt nanoparticles are strong candidates for high density magnetic data storage media because the $L1_0$ phase FePt has a very high magnetocrystalline anisotropy $(K_u{\sim}6.6-10{\times}10^7erg/cm^3)$, high coercivity and chemical stability. In this study, the ordered $L1_0$ FePt nanoparticles were successfully fabricated by chemical vapor condensation process without a post-annealing process which causes severe particle growth and agglomeration. The $Fe_{50}Pt_{50}$ nanopowder was obtained when the mixing ratio of Fe(acac) and Pt(arac) was 2.5 : 1. And the synthesized FePt nanoparticles were very fine and spherical shape with a narrow size distribution. The average particle size of the powder tended to increase from 5 nm to 10 nm with increasing reaction temperature from $800^{\circ}C$ to $1000^{\circ}C$. Characterisitcs of FePt nanopowder were investigated in terms of process parameters and microstructures.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.35 no.3
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• pp.179-191
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• 2009

The objective of this study was to investigate the effect of ethanol on the emulsion prepared by poly(oxyethylene) hydrogenated castor oils (HCOs)/oil/ethanol/water system. Emulsions were prepared using homogenizer as high-energy method. To evaluate effect of ethanol on the emulsion, physical properties such as droplet size and size distribution were determined and other components were almost fixed to analyze the effect of ethanol on the surfactant. In case of HCO-20, the droplet diameter was in micrometers and the droplet size was gradually deceased as the ethanol concentration was increased. The droplet diameter of nano-emulsion containing 4.00 % of HCO-30 was shown in nanometers and its mean droplet size was $128.15{\pm}1.06nm$ and the most stable at the 4.25 % of ethanol contents by the Form. 1 and $136.10{\pm}0.99nm$ at the 3.50 % of ethanol contents by the Form. 2. Similarly, the droplet diameter of nano-emulsion containing 4.00 % of HCO-40 and 4.50 % ethanol by the Form. 1 was $115.85{\pm}0.78nm$ and $121.15{\pm}0.35nm$ at the 3.25 % of ethanol by the Form. 2 and both size distributions were also narrow. Finally, the droplet size of nano-emulsion containing 4.00 % of HCO-60 and 2.25 % ethanol was $262.35{\pm}0.64nm$ and the most stable. The higher ethanol concentrations became the smaller size of emulsion became in the microscale emulsion but we determined nano-emulsion had a minimum size at a certain ethanol concentration. The results showed that the breakdown process of this nano-emulsion could be attributed to Ostwald ripening. This study about effect of ethanol on the emulsion showed that ethanol contents to prepare a stable emulsion could be determined as studying the effect of ethanol on the emulsion with the type of surfactants.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.223-228
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• 2006

Pore-size controlled porous carbons for the catalyst supports of the direct methanol fuel cell were prepared from the mesophase pitch by using the silica spheres with different sizes. Pitch solution in THF and spheres were mixed, carbonized and etched by 5 M NaOH to make porous carbon. Specific surface area of the porous carbons was $14.7{\sim}87.7m^2/g$ and average pore diameter was 50~550 nm which were dependent on the size of silica spheres. Aqueous reduction method was used to load 60 wt% PtRu on the prepared porous carbon supports. The electro-oxidation activity of the supported 60 wt% Pt-Ru catalysts was measured by cyclic voltammetry and unit cell test. For the 60 wt% Pt-Ru/porous carbon synthesized by 50 nm silica, current density value in the cyclic voltammetry test was $123mA/cm^2$ at 0.4 V and peak power density in the unit cell test were 105 and $162mW/cm^2$ under oxygen at 60 and $80^{\circ}C$, respectively.

• Korean Journal of Materials Research
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• v.24 no.6
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• pp.277-284
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• 2014

Using the spray pyrolysis process, nano-sized cobalt oxide powder with average particle size below 50 nm was prepared from cobalt chloride solution. The influences of the raw material solution on the properties of the powder formed examined. When the concentration of Co was low(20 g/L), the average particle size of the powder formed was roughly 20 nm, and the cohesion between these particles was significantly strong. When the concentration of Co increased to 100 g/L, the droplets nearly failed to exist in circular form and reflected a severely divided form. Furthermore, the average size of the particles formed was roughly 40 nm, and the particles reflected a polygonal form. When the solution was increased to nearly saturation level (Co at 200 g/L), the particle size distribution reflected significant unevenness due to severe droplet division while the surface also reflected significant unevenness. Furthermore, the average size of the particles formed increased significantly to 70 nm. The results of XRD analysis showed that the strength of the peaks reflected very little change when the concentration of Co was increased from 20 g/L to 50 g/L. Alternatively, when the concentration was increased to 100 g/L, the strength of the peaks increased compared to when the concentration was 50 g/L. However, when the concentration was increased to 200 g/L, the strength of the peaks failed to reflect significant change compared to when the concentration was 100 g/L. The specific surface area dramatically decreased by 30 % when the concentration of Co was increased from 20 g/L to 50 g/L. Alternatively, when the concentration of Co the solution increased to 100 g/L, the specific surface area decreased by roughly 15 %. Furthermore, when the concentration of Co was increased to nearly saturation level(200 g/L), the specific surface area decreased by roughly 35%.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.2
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• pp.103-118
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• 2012

In this study, the cellular protective effect of isoquercitrin against $H_2O_2$ and rose bengal-indued HaCaT cell damage was investigated. The ethosome and elastic liposome for enhanced transdermal delivery were prepared. Particle size, loading efficiency and cumulative permeated amounts of them were evaluated. Isoquercitrin didn't show any characteristic cytotoxicity at 50 ${\mu}M$. When HaCaT cells were treated with 5 mM $H_2O_2$ and 25 ${\mu}M$ rose bengal, isoquercitrin protected the cells against the oxidative damage in a concentration dependent manner (6.25 ~ 50 ${\mu}M$). The size of 0.03 % isoquercitrin loaded ethosome was 222.85 nm and the loading efficiency was 82.26 %. The ethosome loaded with 0.03 % isoquercitrin was stable and maintained the constant particle size for 2 weeks after being prepared. The ethosome exhibited more enhanced skin permeability than general liposome and ethanol solution. The optimal ratio of lipid to surfactant of 0.1 % isoquercitrin loaded elastic liposomes was observed to be 89 : 5 through evaluating particle size (341.2 nm), deformability index (59.89), loading efficiency (54.3 %), and skin permeability (54.4 %).

• Economic and Environmental Geology
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• v.49 no.5
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• pp.335-347
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• 2016

The mineralogical and geochemical characteristics of diverse carbonate rocks can be investigated by using VNIRSWIR(visible near infrared-short wavelength infrared) spectroscopic analysis as a rapid, nondestructive, and inexpensive tool. Comparing whole rock analysis to VNIR-SWIR spectroscopic analysis, the analytical method was investigated to estimate CaO contents, mud impurity, and whiteness of carbonate rocks involved in high-grade limestones in the field. We classify typical carbonate rocks in the upper Pungchon Formation in high-grade limestone mine area such as the Gangweon, Chungmu and Baegun mine in the Jeongseon area. The results show that powdered specimen has much higher reflectance than cutted specimen between the same sample. Whiteness is highly correlated with reflectance(0.99) for powdered specimen. The absorption of mineral mixtures shifts in position as a result of the mass ratio of calcite and dolomite in the Chungmu mine by changing to 75:25, 50:50, and 25:75. The absorption peak position in carbonate mixtures is highly correlated with CaO contents(0.98~0.99). Based on color system, the carbonate rocks are grouped into (milky) white, light grey, light brown, grey, and dark grey. The absorption peak position shifts from 2340 nm to 2320 nm as CaO contents decrease from 55.86 wt.% to 29.71 wt.%. We confirmed that absorption peak position shifts depending on the amount of Ca, which is bonded to $CO{_3}^{-2}$, Mg, and Fe contents replacing Ca. This result suggests that CaO contents in carbonate rocks can be considered to quantitative analysis in the field by spectroscopic analysis.

• Journal of the Korean Vacuum Society
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• v.9 no.4
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• pp.411-418
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• 2000

$Al_2O_3$ thin films of 300 nm thickness were deposited at room temperature using DC reactive sputtering with variation of the $O_2$ content in the sputtering gas from 30% to 70%. Regardless of the $O_2$ content in the sputtering gas, the sputtered $Al_2O_3$ films were amorphous and exhibited the refractive index of 1.58. When the $O_2$ content in the sputtering gas was higher than 50%, the $Al_2O_3$ films exhibited excellent transmittance of about 98% at 550 nm wavelength. However, the transmittance decreased to about 94% for the $Al_2O_3$ films deposited with the sputtering gas of the 30% and 40% $O_2$contents. The optimum dielectric properties (dielectric constant of 10.9 and loss tangent of 0.01) was obtained for the $Al_2O_3$ film deposited with the sputtering gas of the 50% $O_2$ content. When the $O_2$ content in the sputtering gas was within 40% to 60%, the $Al_2O_3$ films exhibited no shift of flatband voltage $V_{FB}$ in C-V curves and exhibited leakage current density lower than $10^{-5}\textrm{A/cm}^2$ at 150 kV/cm.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.201-207
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• 2009

The hydrogenation reaction of methyl dodecanoate for the synthesis of 1-dodecanol has been carried out in the presence of a copper chromite catalyst. The catalysts were synthesized by ceramic method, co-precipitation, and improved co-precipitation method and the particles were characterized by SEM and XRD. Also, the products of the reaction were assigned by GC, GC/MSD and NMR. The particles synthesized by each method showed (1) a spherical shape with the size of 3.2 to $7.0{\mu}m$, (2) an agglomerated spherical shape with the size of 50 to 500 nm and (3) a spherical shape with smaller particle size, respectively. Especially, in order to control the size of particles, the particles were synthesized in various dispersant solutions as Span 80, polyacrylate, and polyethyleneglycols (PEGs). The particles synthesized in PEG (Mw = 4000) solution showed the smallest particle size of 30 to 50 nm and the regularity of the particle size distribution. Our experimental results elucidated that the activity of catalyst for hydrogenation increases with decreasing the size of catalyst particle. The highest yield of dodecanol in the hydrogenation reaction was 95.5% when copper chromite synthesized in the PEG solution was used as a catalyst in the optimized reaction condition.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.582-587
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• 2012

In this paper, it was studied on the crystallization characteristics of PLA film by adding ammonium phosphate (APP) as a nucleation agent. Crystallinity and crystallite size of PLA film were determined by Scherrer equation. Crystallization rate constant of PLA film was calculated through Avrami equation. Film samples in the study were prepared by two steps. PLA films were prepared by adding 1, 5, and 10 wt%, respectively, at first and was secondly annealed at 130, 140, and $150^{\circ}C$. Crystallinity of pure PLA film was average 4.6% and those of PLA film with adding 1, 5, and 10 wt% APP were 12.2, 47.7, and 50.0%, respectively. Crystallite size of PLA film was average 28.0 nm and those of PLA film with adding 1, 5, and 10 wt% APP were 26.8, 24.0, and 19.0 nm, respectively. Crystallization rate constants of PLA film with 1 wt% APP were 2.12, 3.86, and 0.27 by annealing at 130, 140, and $150^{\circ}C$, respectively, where was higher than pure PLA film and those with adding 5 and 10 wt% APP, respectively.