• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.04b
• /
• pp.79-80
• /
• 2009

The local oxidation using an atomic force microscopy (AFM) is useful for Si-base fabrication of nanoscale structures and devices. SiC is a wide band-gap material that has advantages such as high-power, high-temperature and high-frequency in applications, and among several SiC poly types, 4H-SiC is the most attractive poly type due to the high electron mobility. However, the AFM local oxidation of 4H-SiC for fabrication is still difficult, mainly due to the physical hardness and chemical inactivity of SiC. In this paper, we investigated the local oxidation of 4H-SiC surface using an AFM. We fabricated oxide patterns using a contact mode AFM with a Pt/Ir-coated Si tip (N-type, $0.01{\sim}0.025\;{\Omega}cm$) at room temperature, and the relative humidity ranged from 40 to 50%. The height of the fabricated oxide pattern ($1{\sim}3\;nm$) on SiC is similar to that of typically obtained on Si ($10^{15}{\sim}10^{17}\;cm^{-3}$). We perform the 2-D simulation to further analyze the electric field between the tip and the surface. Whereas the simulated electric field on Si surface is constant ($5\;{\times}\;10^7\;V/m$), the electric field on SiC surface increases with increasing the doping concentration from ${\sim}10^{15}$ to ${\sim}10^{17}\;cm^{-3}$. We demonstrated that a specific electric field ($4\;{\times}\;10^7\;V/m$) and a doping concentration (${\sim}10^{17}\;cm^{-3}$) is sufficient to switch on/off the growth of the local oxide on SiC.

• Transactions on Electrical and Electronic Materials
• /
• v.18 no.1
• /
• pp.46-50
• /
• 2017

The Zn1-xMnxO ($0.00{\leq}x{\leq}0.06$) samples have been synthesized in the form of powder by the coprecipitation method at low temperature using $Zn(CH_3COO)_2$. $2H_2O$ and $Mn(CH_3COO)_2$. $4H_2O$ powders, as well as HCl and $NH_4OH$ solutions as starting materials. Characterization was conducted using XRD, TEM, XRF, FTIR and VSM. The result shows that the $Zn_{(1-x)}Mn_xO$ ($0.00{\leq}x{\leq}0.06$) nanoparticles have the wurtzite phase with a hexagonal structure and particle sizes ranging from 17.48 to 118.83 nm. In a qualitative analysis of XRF, the peaks that confirm the existence of the manganese element in Mn-doped ZnO samples were observed. Meanwhile, FTIR test result shows that there are peaks at around $500cm^{-1}$ and $400cm^{-1}$ in the FTIR spectra for Mn doped ZnO samples which clearly reveal the existence of the (Zn, Mn)-O strain mode. The (Zn, Mn)-O absorption peak positions have shifted to a lower wave number with increasing Mn doping content. The peak intensity is also lower if compared to that of the ZnO sample without doping. From the VSM test, it is shown that $Zn_{(1-x)}Mn_xO$ ($0.00{\leq}x{\leq}0.06$) nanoparticles are all paramagnetic having monotonically increased susceptibility as increasing Mn content.

• Fashion & Textile Research Journal
• /
• v.16 no.3
• /
• pp.492-498
• /
• 2014

Lotus(Nelumbo nucifera gaertn) is intimate plant to many people that it has clean and noble characteristics despite growth in the mud. Especially Lotus seedpods, byproduct of lotus, are rich in oligometric procyanidins and could be a new source of procyanidins. Procyanidins, also known as condensed tannins, are a class of polyphenols. In other words lotus seedpod contains plenty of tannins. Commonly tannins colorants could increase adsorption and fastness properties in fabric dyeing. This study was made to investigate colorants characteristics of lotus seedpod and various colorfastness properties of dyed silk fabrics. The wavelength of maximum absorption of lotus seedpod solution appeared at 273.5 nm from UV-vis spectrophotometer. From the results of FT-IR spectra measurements, IR absorption band of lotus seedpod colorants appeared at $3415cm^{-1}$, $2900cm^{-1}$ and $1620cm^{-1}$ by tannin structure. And tannin ingredient contents was the highest at pH 9 and flavonoid at pH 11. Lotus seedpod colorants showed relatively good affinity at pH 3 on silk fabrics and optimum dyeing temperature and time for silk was for 50 min, at $80^{\circ}C$. K/s of Light fastness according to different washing method was the highest at process including ironing and ${\Delta}E$ was the lowest. All of fastness(Light rubbing laundering perspiration dry cleaning) showed excellent results over 4 or 4-5 grades.

• Asian-Australasian Journal of Animal Sciences
• /
• v.17 no.12
• /
• pp.1712-1716
• /
• 2004

Copper-bearing montmorillonite (Cu-MMT) was produced by $Cu^{2+}$ cation exchange reaction. X-ray diffraction analysis showed that that the (001) basal spacing of the MMT crystal lattice increased from 1.544 to 1.588 nm after $Cu^{2+}$ exchange. This indicated that $Cu^{2+}$ entered into interlayer position of MMT as a hydrated cation or composite cation. In vitro results indicated that Cu-MMT had antibacterial activity on Escherichia coli $K_{88}$. Cu-MMT had unbalanced positive charge after cation exchange. Its antibacterial activity resulted from two aspects, one was electrostatic attraction which made E. coli $K_{88}$ being adhered on the montmorillonite surface, the other was the $Cu^{2+}$ slowly released, which could kill bacteria. In an in vivo study, four replicates of eight weanling pigs were assigned to each of two dietary treatments to study the effects of Cu-MMT on diarrhea, E. coli in the lumen of the jejunum and morphology of jejunal mucosa. As compared to the control, supplementation of the diet with 0.2% Cu-MMT improved average daily gain by 12.50% (p<0.05) and decreased F/G by 9.42% (p<0.05). The mean diarrhrea incidence was decreased by 71.80% (p<0.05). The viable counts of Escherichia coli in jejunal contents were significantly reduced (p<0.05). Villus height and the villus height to crypt depth ratio at the jejunal mucosa were increased by 19.09% (p<0.05) and 37.10% (p<0.05), respectively.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.15 no.3
• /
• pp.217-228
• /
• 1993

The purpose or this study was to observe the histological alteration of Langerhans cells on wound healing process in applying low energy laser irradiation. For this study, 50 Spraque-Dewly rats, weighing 150Gm or more were devided into control, experimental control group(0), 47.5Hz(1), 190Hz(3), 380Hz(5), 760Hz(7), lased group. All the experimental animals were made excision wound on buccal mucosa, 2mm depth, and lased with stoma laser (904nm, semconductor type ASGaAI, Sedalac France) 47.5Hz, 380Hz, 960Hz, 3minutes one time respectively except experimental control group. After the experiment, experimental animals were sacrificed after 24hours, 48hours, 72hours on each. Taken specimens were embedden in paraffin, sectioned 6-8u in thickness. And the langerhans cell were detected using ant S-100 protein antibody, and histochemically processed with Avidin Biotin complex method. All the Langerhan cells were calculated under light microspe in 400 multiplication field and standard deviation, probability test between each group were evaluated using statistical analysis system(S.A.S)program. Following results were obtained. 1. Langerhan cells were increased in experimental control group compared to that in control group(P<0.01). 2. 24hour after experiments, Langerhans cell were decreased compare to that in control group and control experimental group 5, 1, 3. Probability test shows significance between control experimental and 5, 1, 3 group on a =0.05 range. 3. 48our after experiment, Langerhans cells were decreased compare to that on experimental control group, and probability test shows significance between control experimental and 3, 7, 5 group an a=0.05 range. 4. 72hour after experiments, Langerhans cells were decreased compare to that on experimental control group and probability test on group comparison shows significance between control experimental and 1, 5 and 1 between 3, 7 between 3, and 5, between 7, respeilively on a=0.05 range. 5. Langerhans cells number in experimental group were decreased compare to that on experimental control group in applying laser irradiation.

• The Korea Journal of Herbology
• /
• v.23 no.4
• /
• pp.45-49
• /
• 2008

Objectives: To investigate the quantitative determination of marker constituents of Dioscoreae Rhizoma by the packaging methods Methods: HPLC for the determinations of allatoin in the Dioscoreae Rhizoma. the separation method was performed on an Luna $NH_2$ column($250mm{\times}4.6mm,\;5{\mu}m$, Phenomenes) using solvent water-acetonitrile(2:8, v/v%) with photo diode array detector(210nm). The flow rate was 2.0 mL/min. Results: Retention time of allatoin in HPLC chromatogram was about 4.8 min and calibration curve showed good linearity($R^2$=0.9994) at concentrations from 50.0 to 1000.0 ${\mu}g/mL$ of allantoin. Average content of allantoin by packaging methods was $0.16{\sim}0.40%$. In addition. weight loss rate(%) of Dioscoreae Rhizoma according to the packaging methods was $-0.60{\sim}1.80%$. Conclusions: The variation on content of the marker constituent of Dioscoreae Rhizoma by the packaging methods didn't show difference.

• Biomedical Science Letters
• /
• v.13 no.4
• /
• pp.349-354
• /
• 2007

The purpose of this study was to examine the effect of vanillic acid on the cell viability and melanogenesis in melanocytes damaged by reactive oxygen species (ROS). The human skin melanoma cells (SK-MEL-3) were cultured with various concentrations of hydrogen peroxide $(H_2O_2)$. The cell viability for $H_2O_2$-induced cytotoxicity or vanillic acid against $H_2O_2$ was measured by XTT assay in these cultures. For the effect of vanillic acid on the melanogenesis, the tyrosinase inhibitory activity was measured by colorimetric assay at a wavelength of 490 nm, and melanin synthesis activity were assessed after cells were cultured in the media with or without various cencentrations of vanillic acid. In this study, $H_2O_2$ decreased cell viability dose- and time-dependent manners and $XTT_{50}$ was determined at a concentration of 80 ${\mu}M$, $H_2O_2$. Vanillic acid increased the cell viability dose dependently in human skin melanoma cells damaged by $H_2O_2$-induced cytotoxicity. In the tyrosinase inhibitory activity, vanillic acid supresssed tyrosinase activity in dosedependent manner, and also decreased significantly melanin synthesis activity compared with $H_2O_2$-treated group. From these results. It is suggested that $H_2O_2$-mediated cytotoxicity was highly by the toxic criteria of Borenfreund and Puerner and also, vanillic acid has the protective effect on ROS-induced cytotoxicity and melanogenesis in these cultures.

• Korean Journal of Materials Research
• /
• v.12 no.12
• /
• pp.904-910
• /
• 2002

Surface alloying using TiC, $TiB_2$ and VC ceramic particles on carbon steel has been performed using high voltage electron beam. Each type of ceramic particles was mixed with flux of Al and $MgF_2$ in 1 to 4 ratio. The microstructures of the surface alloyed layers consisted of melted region, interface region. heat affected region and the unaffected matrix. The surface layer of the TiC surface alloyed had a cubed primary and a eutectic type of TiC. $TiB_2$ in surface layer of $TiB_2$ surface alloyed were incompletely melted with$ TiB_2$ particles as observed before the alloying. On the surface layer of the VC surface alloyed, very well defined cell structure was observed with VC on the cell boundary. In addition, ~50 nm in diameter VC particles in high density were ubiquitous in the matrix. Those fine VC particles prominently improved the hardness and wear resistance of the surface layer of the VC surface alloyed.

• Korean Journal of Materials Research
• /
• v.23 no.6
• /
• pp.299-303
• /
• 2013

In this study, a micro gas sensor for $NO_x$ was fabricated using a microelectromechanical system (MEMS) technology and sol-gel process. The membrane and micro heater of the sensor platform were fabricated by a standard MEMS and CMOS technology with minor changes. The sensing electrode and micro heater were designed to have a co-planar structure with a Pt thin film layer. The size of the gas sensor device was about $2mm{\times}2mm$. Indium oxide as a sensing material for the $NO_x$ gas was synthesized by a sol-gel process. The particle size of synthesized $In_2O_3$ was identified as about 50 nm by field emission scanning electron microscopy (FE-SEM). The maximum gas sensitivity of indium oxide, as measured in terms of the relative resistance ($R_s=R_{gas}/R_{air}$), occurred at $300^{\circ}C$ with a value of 8.0 at 1 ppm $NO_2$ gas. The response and recovery times were within 60 seconds and 2 min, respectively. The sensing properties of the $NO_2$ gas showed good linear behavior with an increase of gas concentration. This study confirms that a MEMS-based gas sensor is a potential candidate as an automobile gas sensor with many advantages: small dimension, high sensitivity, short response time and low power consumption.

• Korean Journal of Materials Research
• /
• v.27 no.10
• /
• pp.534-543
• /
• 2017

$Gd_2O_3:Eu^{3+}$ red phosphors were prepared by template method from crystalline cellulose impregnated by metal salt. The crystallite size and photoluminescence(PL) property of $Gd_2O_3:Eu^{3+}$ red phosphors were controlled by varying the calcination temperature and $Eu^{3+}$ mol ratio. The nano dispersion of $Gd_2O_3:Eu^{3+}$ was also conducted with a bead mill wet process. Dependent on the time of bead milling, $Gd_2O_3:Eu^{3+}$ nanosol of around 100 nm (median particle size : $D_{50}$) was produced. As the bead milling process proceeded, the luminescent efficiency decreased due to the low crystallinity of the $Gd_2O_3:Eu^{3+}$ nanoparticles. In spite of the low PL property of $Gd_2O_3:Eu^{3+}$ nanosol, it was observed that the photoluminescent property was recovered after re-calcination. In addition, in the dispersed nanosol treated at $85^{\circ}C$, a self assembly phenomenon between particles appeared, and the particles changed from spherical to rod-shaped. These results indicate that particle growth occurs due to mutual assembly of $Gd(OH)_3$ particles, which is the hydration of $Gd_2O_3$ particles, in aqueous solvent at $85^{\circ}C$.