• Korean Chemical Engineering Research
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• 제51권2호
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• pp.195-202
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• 2013

본 연구에서는 Titanium(IV) sulfate($Ti(SO_4)_2$)와 암모니아수로부터 수열합성법을 이용하여 비교적 낮은 합성온도($80{\sim}100^{\circ}C$)와 상압에서 소성과정을 거치지 않고 $TiO_2$ 분말을 제조하였고, $TiO_2$ 제조 시 반응온도, 반응물의 초기농도, 혼합용액의 pH와 같은 반응조건에 따른 $TiO_2$ 입자의 결정구조와 입자분포, 형상 등과 같은 물리적 특성을 고찰하였다. 제조한 시료는 UV 조사 하에 Brilliant Blue FCF(BB-FCF)의 광분해 실험을 실시하여 광분해 성능과 DRS 분석을 통해 광촉매 활성을 비교하였다. 제조한 시료의 물성은 XRD, SEM, PL, 입도분포 측정을 통하여 확인하였다. Titanium(IV) sulfate($Ti(SO_4)_2$)의 초기농도가 증가할수록 $TiO_2$의 평균 입자크기와 결정화도는 증가하였고 광촉매 활성은 감소하였다. 혼합용액의 pH가 높을수록 평균 입자크기는 감소하였고 광촉매 활성은 증가하였다. 반응온도가 높을수록 결정화도와 광촉매 활성은 증가하였다. 이상의 결과들로부터 $Ti(SO_4)_2$와 암모니아수를 이용한 비교적 낮은 합성온도와 상압에서의 수열합성법으로도 순수한 anatase 결정구조의 $TiO_2$가 제조됨을 확인할 수 있었다.

• Journal of Ginseng Research
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• 제38권2호
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• pp.136-145
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• 2014

Background: This study aimed to develop a biocontrol system for ginseng root rot caused by Fusarium cf. incarnatum. Methods: In total, 392 bacteria isolated from ginseng roots and various soils were screened for their antifungal activity against the fungal pathogen, and a bacterial isolate (B2-5) was selected as a promising candidate for the biocontrol because of the strong antagonistic activity of the bacterial cell suspension and culture filtrate against pathogen. Results: The bacterial isolate B2-5 displayed an enhanced inhibitory activity against the pathogen mycelial growth with a temperature increase to $25^{\circ}C$, produced no pectinase (related to root rotting) an no critical rot symptoms at low [$10^6$ colony-forming units (CFU)/mL] and high ($10^8CFU/mL$) inoculum concentrations. In pot experiments, pretreatment with the bacterial isolate in the presumed optimal time for disease control reduced disease severity significantly with a higher control efficacy at an inoculum concentration of $10^6CFU/mL$ than at $10^8CFU/mL$. The establishment and colonization ability of the bacterial isolates on the ginseng rhizosphere appeared to be higher when both the bacterial isolate and the pathogen were coinoculated than when the bacterial isolate was inoculated alone, suggesting its target-oriented biocontrol activity against the pathogen. Scanning electron microscopy showed that the pathogen hyphae were twisted and shriveled by the bacterial treatment, which may be a symptom of direct damage by antifungal substances. Conclusion: All of these results suggest that the bacterial isolate has good potential as a microbial agent for the biocontrol of the ginseng root rot caused by F. cf. incarnatum.

• Korean Chemical Engineering Research
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• 제53권5호
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• pp.565-569
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• 2015

Envisaging the role of Co in theranautics and biomedicine it is immensely important to evaluate its antimicrobial activity. Hence in this study CoO thin nanosheets (CoO-TNs) were synthesized using wet chemical solution method at a very low refluxing temperature ($90^{\circ}C$) and short time (60 min). Scanning electron microscopy of the grown structure revealed microflowers ($2{\sim}3{\mu}m$) composed of thin sheets petals (60~80 nm). The thickness of each individual grown sheet varies from 10~20 nm. Antimicrobial activities of CoO-TNs against two Gram positive bacteria (Micrococcus luteus, and Staphylococcus aureus), and two Gram negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were determined. A 98% and 65% growth inhibition of M. luteus and S. aureus respectively, was observed with $500{\mu}g/ml$ of CoO-TNs compared to 39 and 34% growth inhibition of E. coli and P. aeruginosa, respectively with the same concentration of CoO-TNs. Hence, synthesized CoO-TNs exhibited antimicrobial activity against Gram negative bacteria and an invariably higher activity against tested Gram positive bacteria. Therefore, synthesized CoO-TNs are less prone to microbial infections.

• 공업화학
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• 제27권4호
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• pp.386-390
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• 2016

축전식 탈염전극의 에너지 효율을 향상시키기 위하여 탄소나노튜브를 불소화 표면처리하고 이를 도전재로 적용하였다. 탄소나노튜브는 상온에서 불소와 질소의 혼합가스로 불소화 처리되었으며, 미처리 탄소나노튜브와 불소화 탄소나노튜브를 각각 활성탄소 대비 0~0.5 wt% 첨가하여 활성탄소 기반 축전식 탈염전극을 제조하였다. 불소화 탄소나노튜브는 미처리 탄소나노튜브에 비하여 전극 슬러리 및 전극 내에서 분산성이 향상된 것을 제타 전위와 전자주사현미경을 통해 확인하였다. 불소화 탄소나노튜브를 첨가한 전극은 미처리 탄소나노튜브를 첨가한 전극보다 전체적으로 높은 탈염효율을 보였으며, 에너지 소비량 역시 감소하였다. 이는 불소화 표면처리로 인한 탄소나노튜브의 분산성 향상으로 인해 축전식 탈염 전극의 저항이 감소되었기 때문이다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.331-331
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• 2009

Hafnium oxide ($HfO_2$) attracted by one of the potential candidates for the replacement of si-based oxides. For applications of the high-k gate dielectric material, high thermodynamic stability and low interface-trap density are required. Furthermore, the amorphous film structure would be more effective to reduce the leakage current. To search the gate oxide materials, metal-insulator-metal (MIM) capacitors was fabricated by pulsed laser deposition (PLD) on indium tin oxide (ITO) coated glass with different oxygen pressures (30 and 50 mTorr) at room temperature, and they were deposited by Au/Ti metal as the top electrode patterned by conventional photolithography with an area of $3.14\times10^{-4}\;cm^2$. The results of XRD patterns indicate that all films have amorphous phase. Field emission scanning electron microscopy (FE-SEM) images show that the thickness of the $HfO_2$ films is typical 50 nm, and the grain size of the $HfO_2$ films increases as the oxygen pressure increases. The capacitance and leakage current of films were measured by a Agilent 4284A LCR meter and Keithley 4200 semiconductor parameter analyzer, respectively. Capacitance-voltage characteristics show that the capacitance at 1 MHz are 150 and 58 nF, and leakage current density of films indicate $7.8\times10^{-4}$ and $1.6\times10^{-3}\;A/cm^2$ grown at 30 and 50 mTorr, respectively. The optical properties of the $HfO_2$ films were demonstrated by UV-VIS spectrophotometer (Scinco, S-3100) having the wavelength from 190 to 900 nm. Because films show high transmittance (around 85 %), they are suitable as transparent devices.

• 한국분말재료학회지
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• 제27권1호
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• pp.52-57
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• 2020

In this study, we report the microstructure and characterization of Ta₂₀Nb₂₀V₂₀W₂₀Ti₂₀ high-entropy alloy powders and sintered samples. The effects of milling time on the microstructure and mechanical properties were investigated in detail. Microstructure and structural characterization were performed by scanning electron microscopy and X-ray diffraction. The mechanical properties of the sintered samples were analyzed through a compressive test at room temperature with a strain rate of 1 × 10^-4 s^-1. The microstructure of sintered Ta₂₀Nb₂₀V₂₀W₂₀Ti₂₀ high-entropy alloy is composed of a BCC phase and a TiO phase. A better combination of compressive strength and strain was achieved by using prealloyed Ta₂₀Nb₂₀V₂₀W₂₀Ti₂₀ powder with low oxygen content. The results suggest that the oxide formed during the sintering process affects the mechanical properties of Ta₂₀Nb₂₀V₂₀W₂₀Ti₂₀ high-entropy alloys, which are related to the interfacial stability between the BCC matrix and TiO phase.

• Current Research on Agriculture and Life Sciences
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• 제30권1호
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• pp.51-59
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• 2012

Fresh oyster mushrooms (Pleurotus ostreatus) were gamma-irradiated at 0, 1, 2, and 3 kGy. The effects on various quality attributes were determined during storage at $5{\pm}1^{\circ}C$. Color changes were more prominent in the cap region than the stem part. At the start of storage increase of Hunter's L-value (lightness) was observed in the caps of 2 and 3 kGy-irradiated samples. The L-value was higher in the all irradiated samples during storage. The trend was different in the case of stem region, where L-value decreased upon irradiation, but remained high throughout storage. The ${\alpha}$-value declined, whereas the b-value increased following irradiation. Irradiation showed a dose-dependent effect on the firmness, which was clearer during storage, but the samples irradiated at 1 kGy maintained an overall better texture than other irradiated samples. The weight loss was also higher in the all irradiated samples during storage. The samples irradiated at 1 kGy showed good physical appearance without any fungal attack at the end of storage; however color change in cap region was quite apparent. The ultra-structural drastic effect of irradiation was understandable using scanning electron microscopy. E-nose analysis demonstrated a clear change in the volatile profiles of all irradiated samples. Although the effect of irradiation on quality characteristics was quite clear but the all irradiated samples were free from fungal attack that was observed in the case of control sample.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1832-1836
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• 2014

A deep understanding of the metallic silver catalysts formation process on oxide support and the formation mechanism is of great scientific and practical meaning for exploring better catalyst preparing procedures. Herein the thermal decomposition process of supported silver catalyst with silver oxalate as the silver precursor in the presence of ethylenediamine and ethanolamine is carefully investigated by employing a variety of characterization techniques including thermal analysis, in situ diffuse reflectance infrared Fourier transform spectroscopy, scanning electron microscopy, and X-ray diffraction. The formation mechanism of supported silver particles was revealed. Results showed that formation of metallic silver begins at about $100^{\circ}C$ and activation process is essentially complete below $145^{\circ}C$. Formation of silver was accompanied by decomposition of oxalate group and removal of organic amines. Catalytic performance tests using the epoxidation of ethylene as a probe reaction showed that rapid activation (for 5 minutes) at a relatively low temperature ($170^{\circ}C$) afforded materials with optimum catalytic performance, since higher activation temperatures and/or longer activation times resulted in sintering of the silver particles.

• 신재생에너지
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• 제9권2호
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• pp.23-29
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• 2013

Furnace and laser is currently the most important doping process. However furnace is typically difficult appling for selective emitters. Laser requires an expensive equipment and induces a structural damage due to high temperature using laser. This study has developed a new atmospheric pressure plasma source and research atmospheric pressure plasma doping. Atmospheric pressure plasma source injected Ar gas is applied a low frequency (a few 10 kHz) and discharged the plasma. We used P type silicon wafers of solar cell. We set the doping parameter that plasma treatment time was 6s and 30s, and the current of making the plasma is 70 mA and 120 mA. As result of experiment, prolonged plasma process time and highly plasma current occur deeper doping depth and improve sheet resistance. We investigated doping profile of phosphorus paste by SIMS (Secondary Ion Mass Spectroscopy) and obtained the sheet resistance using generally formula. Additionally, grasped the wafer surface image with SEM (Scanning Electron Microscopy) to investigate surface damage of doped wafer. Therefore we confirm the possibility making the selective emitter of solar cell applied atmospheric pressure plasma doping with phosphorus paste.

• 한국진공학회지
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• 제18권5호
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• pp.384-389
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• 2009

ZnO는 육방정계결정구조의 물질로서 3.37 eV의 넓은 띠 간격과 60 meV의 큰 exciton 결합에너지에 따른 높은 효율의 자외선발광으로 짧은 파장의 빛 (녹, 청, 자외선)을 내는 LED (Light Emitting Diode) 분야에서 관심을 기울이고 있는 물질이다. LED제작을 위해서는 n형의 ZnO와 p형의 ZnO가 필요하지만 기본적으로 ZnO은 n형이므로 신뢰성 있는 p형 ZnO박막을 제작하기 위한 노력이 기울여지고 있다. 본 연구에서는 ALD (Atomic Layer Deposition)로 제작된 ZnO박막에 20 keV의 에너지를 갖는 질소이온을 $10^{13}{\sim}10^{15}ions/cm^2$로 조사한 후 Hall 효과 측정장치를 이용하여 질소이온 조사에 따른 전기적 특성변화를 조사하였다.