• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.11
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• pp.716-719
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• 2016

In this paper, we fabricated flexible CNT/PVDF (carbon nanotube / polyvinylidene fluoride) piezoelectric composite device with flexible poly(3,4-ethylenedioxythiophene) : polystyrene sulfonate (PEDOT:PSS) conducting polymer electrode using spray coating method. We tried to improve the piezoelectric performance from the CNT/PVDF composite film by enhancing electrical conductivity of the PEDOT:PSS electrodes. Electrical conductivity of the PEDOT:PSS electrode was enhanced by dipping it into the EG (ethylene glycol) solvent. Changes of chemical composition of the PEDOT:PSS electrode were analyzed with the dipping time by XPS (x-ray photoelectron spectroscopy) in terms of oxygen (O1s). Finally, Piezoelectric performances such as output voltage and current were measured with the dipping time. We found that enhanced electrical conductivity of the PEDOT:PSS electrodes resulted in improvement of the piezoelectric performance of the CNT/PVDF films.

• Journal of Periodontal and Implant Science
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• v.25 no.2
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• pp.418-437
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• 1995

The effect of the hydroxyapatite coatings on Titanium implants has been the subject of recent investigations. So far, the use of HA coating remains substantially controversial.This study was aimed to evaluate histologically the bone healing patterns around titanium plasm sprayed(TPS) amd HA-coated implant after implantation into the femur neck of ten adult dogs. After implantation, animals were sacrificed at the intervals of 2,4,6,8 and 12 weeks.The fluorescent dyes were injected on the postoperative 4th and 12th week into the animals supposed to be killed at the 12th week. The morphology and direction of new bone formation was similar in both TPS and HA-coated implants.There was a tendency toward more bone formation in the cortical bone area than in the cancellous bone area. Histologically,in the interface of the HA-coated implants, bone response and bone maturation was faster, compared to the TPS implants in the 2nd and 4th week. By fluorescent microscopy, new bone formation was active in the 4th week around both implants and was directed from the periosteum overlying cortical bone to the cancellous bone. These results suggest that the bone formation and maturation is faster during the early healing stage in the interface of the HA-coated implant and where the cortical bone quality is poor, HA coated implant is superior to the TPS implant in the early phase of new bone formation.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.425.2-425.2
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• 2014

$TiO_2$ possesses great photocatalytic properties but absorbs only UV light owing to high band gap energy (Eg = 3.2 eV). By narrowing the band gap through doping a metal ion, the photocatalytic activity can be enhanced in condition of the light of a higher than 365 nm wavelength. Main purpose for this study is to evaluate the activities of metal doped $TiO_2$ for degrading the volatile organic compounds (VOCs); p-xylene is chosen in the VOC removal test. Vanadium is selected in this study because an ionic radius of vanadium is almost the same as titanium ion and vanadium can be easily doped into $TiO_2$. V-doped $TiO_2$ was synthesized by sol-gel methods and compared with pure $TiO_2$. Pure TiO2 powder and V-doped $TiO_2$ powder were coated on glasses by spray coating method. UV-Visible spectrophotometer was used for the measurement of the band gap changes. VOC concentration degradation level was tested with using various UV light sources in an enclosed chamber. Catalytic activities of prepared samples were evaluated based on the experimental results and compared with coated pure $TiO_2$ sample.

• Journal of the Korean institute of surface engineering
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• v.27 no.2
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• pp.99-108
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• 1994

Films of glass-ceramics $Li_2O-Al_2O_3-SiO_2$(LAS)system were prepared on substrate of an iron plate(SCP) by sol-gel technique using metal alkoxide such as Si$(OC_2H_5)_4$,Al$(OC_2H_9)_3$) and Ti$(OC_2H_6)_4$). Sol which was made by means of simple spray coating, on the substrate was hydrolyzed at 75~$80^{\circ}C$ in moisture cabinet (80~90 % humidity) to form the multicomponent gel. The films up to about 0.8~1.0$mu extrm{m}$ in thickness can be obtained by repeating operation, spraylongrightarrowhydrolysis and condensationlongrightarrowdryinglongrightarrowheating and crystallization at $700^{\circ}C$ for 3~5min. The far-infrared radiation spectra of the coated films on substrate were examined by FT-IR and of films was also observed by scanning electron micrograph technique. The thermal evaluation of the gel-film is followed by TG/DTA measurements. The structure evaluation is followedd X-ray diffraction. These results suggest that this process is applicable to far-infrared radiat at thin film technique.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.97-97
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• 2017

This study investigated the corrosion protection by electrodeposited copper layer on AZ31 Mg alloy with and without additional silver layer by immersion test, salt spray test, OCP transient and potentiodynamic polarization experiment. The single electrodeposited Cu layer on AZ31 Mg alloy showed a nodular structure with many imperfections of crevices between the nodules, which resulted in the fast initiation of pitting corrosion within first few hours of immersion. Double-layer coating of Cu and outer Ag layer slightly increased the initiation time for pitting corrosion. Triple-layer coatings of Cu/Ag/Cu exhibited the most efficient corrosion protection of AZ31 Mg alloy, compared to the single- and double-layer coatings. Surface morphology of the outer Cu layer in the triple-layer was changed from the nodular structure to fine particle structure with no crevices due to the presence of an additional Ag layer. Thus, the improved corrosion resistance of AZ31 Mg alloy by electrodeposited Cu/Ag or Cu/Ag/Cu layers is readily ascribed to the decreased number of imperfections in the electrodeposited layers due to the additional silver layer. It is concluded that the additional silver layer provides many nucleation sites for the second Cu plating, resulting in the formation of finer and denser structure than the first Cu electrodeposit.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.96-102
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• 2001

plasma-sprayed Cr$_2$O$_3$-based coatings containing MoO$_3$ were studied to gain a better understanding of the influence of MoO$_3$ composition in the coatings on their tribological behaviour. A reciprocal type tribo-tester was employed to examine friction and wear behavior of the specimens at high temperature(450。C). The physical characteristics of worn surfaces were investigated by scanning electron microscopy and chemical composition of the coating surfaces was analyzed using a X-ray photoelectron spectrometer. The results showed that friction coefficient of the MoO$_3$-added coatings were lower than those without MoO$_3$ addition. The larger protecting layers were observed at the worn surface of plasma spray coated specimens with MoO$_3$ addition. XPS analysis of the protecting layer indicated that MoO$_3$ composition was dominantly formed at the surface. MoO$_3$ composition in the protecting layer appears to be more favorable in reducing the friction.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.190-190
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• 2012

전북대학교 고온 플라즈마 응용 연구 센터는 교육과학기술부 기초연구사업 중 고가연구장비 구축사업의 일환으로 소재공정용 다목적 100 kW 플라즈마 발생장치를 구축하고 있다. 100kW급 ICP (RF)형 플라즈마 발생장치는 RF 전력 인출이 이중으로 되어있어 한쪽에서는 수~수십 um 크기의 금속, 세라믹 등 고융점 원료분말을 순간적으로 용해, 기화 및 분해시키고 이들 기화 또는 분해된 증기를 급랭시키는 과정에서 초미분(<1 um)을 합성하는 플라즈마 합성법 연구가 가능하도록 RF 플라즈마 분말 합성 시스템이 연결되어 있고 다른 한쪽으로는 진공 챔버 내에서 고온 고속의 RF 플라즈마 불꽃을 형성 한 후 RF 플라즈마의 축 방향으로 반응성 가스 및 코팅 대상 물질을 주입하여 코팅 할 수 있는 열플라즈마 용사코팅 시스템이 연결되어 있는 다목적 연구 장치이다. 본 장치는 100 kW급 RF 전원 공급기와 유도결합형 플라즈마 토치, 플라즈마 분말 합성 부, 플라즈마 코팅 및 반응성 증착부, 가스 공급부, 냉각수 공급부, 전기 계장/제어부로 구성되어 있다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.256-257
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• 2015

마그네슘 합금은 낮은 비중, 높은 비강도, 주조성 및 절삭가공성, 치수안정성, 내흠집성이 우수한 특성을 지니고 있는 경량금속으로써 우수한 주조성과 상온강도, 연신율을 나타낸다. 최근에는 마그네슘 합금을 사용한 IT 기기의 케이스 및 자동차 내, 외장 부품 등의 제품이 다양하게 출시되어지며 금속 질감의 감성 기능까지 적용시킨 전자 기기 제품에 대한 수요가 급증하고 있는 추세이다. 하지만 마그네슘 합금의 낮은 부식 저항성은 마그네슘 합금을 적용시킨 제품에 큰 단점으로 작용되고 있으며 이를 해결하기 위한 연구가 활발히 진행 중이다. 본 연구에서는 플라즈마 전해산화법과 실리카 졸-겔 코팅법을 이용하여 마그네슘 합금의 내부식성을 향상시킴과 동시에 금속질감의 감성 기능을 구현하고자 하였다. 플라즈마 전해산화 공정으로 형성된 산화피막층과 $SiO_2$ 코팅으로 형성된 코팅층의 표면과 단면에 대해서는 FE-SEM(Field emission Scanning Electron Microscope)과 FE-TEM(Field emission Transmission Electron Microscope)으로써 확인하였고 전기화학적 특성 분석을 통한 동전위(Potentiodynamic polarization)와 EIS(Eletrochemical Impedance Spectroscopy) 그리고 Salt spray등을 분석하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.781-783
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• 2010

Chonbuk national university High-enthalpy plasma research center is under construction for 60kW and 200kw ICP(RF) Plasma system as Advance Material R&D and production equipment. The 60kW & 200kW ICP(RF) plasma systems will contribute to promote Korea's material industrial development and Thermal plasma technology.

• Journal of the Semiconductor & Display Technology
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• v.13 no.1
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• pp.7-12
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• 2014

In this study, we investigate the effects of corona-discharge pre-treatment on the properties of carbon nanotubes (CNTs) which are used as flexible transparent electrodes. The CNTs are deposited on PET (polyethylene terephthalate) substrates using a spray coating method. Prior to the deposition of CNTs, the PET substrates are corona-treated by varying the feeding directions of the PET substrate and the numbers of treatments. The variations in the surface morphologies and roughnesses of the PET substrates due to corona-treatment are characterized via atomic force microscopy (AFM). Dynamic contact angles (DCAs) of the corona-treated PET substrates are measured and analyzed as functions of the treatment conditions. Also, the sheet resistances and visible-range transmittances of the CNTs deposited on PET substrates are measured before and after bending test. The experimental results obtained in this study provide strong evidences that the adhesive forces between CNTs and PET substrates can be substantially enhanced by corona-discharge pretreatment.