• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.117-122
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• 2005

Electron Beam Physical Vapor Deposition (EB-PVD) is a typical technology for thermal barrier coating with Yttria Stabilized Zirconia (YSZ) on aero gas turbine engine. In this study EB-PVD method was used to fabricate dense YSZ film on NiO-YSZ as a electrolyte of Solid Oxide Fuel Cell (SOFC). Dense YSZ films of -10 $\mu$m thickness showed nano surface structure depending on deposition temperature. Electrical conductivities of YSZ film and electric power density of the single cell were evaluated after screen- printing $LaSrCoO_3$ as a cathode.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.203-209
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• 1999

LaAlO3d single phase used as the butter layer on Si wafer for YBa2Cu3O7-$\delta$ superconductor application were prepared by solid state reaction method and by self-sustaining combustion process. The microstructure and crystallity of synthesiszed LaAlO3 powder studied using scanning electron microscope (SEM) and X-ray diffractometer(XRD), specific surface area and sintering characteristics fo powder were investigated by Brunauer-Emmett-Teller (BET) method and dilatometer respectively. In solid state reaction method, it is difficult to obtain LaAlO3 single phase up to 150$0^{\circ}C$ period. However, in self-sustaining combustion process, it is to easy to do it only $650^{\circ}C$. Based on the results of analysis of dilatometer it is easier to obtain high sintering density (98.87%) in self-sustaining combustion process than in the solid state reaction method. This reason is that the average particle size prepared by self-sustaining combustion process is nano crystal size and has high specific surface are value(56.54 $m^2$/g) compared with that by solid state reaction method. Also, LaAlO3 layer on the Si wafer has been achieved by screen printing and sintering method. Even though the sintering temperature is 130$0^{\circ}C$, the phenomena of silicon out diffusion in LaAlO3/Si interphase are not observed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.374-374
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• 2014

의료용 X-ray는 과거 analog 방식과, 연구가 진행 중이며 현재 많이 사용되고 있는 digital 방식으로 나누어진다. 최근, 광도전체와 형광체 기반의 flat panel X-ray detector의 발전에 따른 상용화가 이루어지고 있으며, 많은 발전 가능성이 제기되고 있다. flat panel X-ray detector 검출방식은 direct method (직접 방식)와 indirect method (간접 방식)로 나누어진다. 본 연구는 일반적으로 상용화 되어있는 amorphous seleinum (비정질 셀레늄)의 큰 일함수에 의한 저 해상력이라는 단점을 보완하기 위해, 작은 일함수를 가지는 물질을 사용하여, 영상을 얻을 시에 높은 해상력으로 표현할 수 있도록 하고, 원자번호가 높은 물질을 사용하여 X-ray 흡수율을 높일 수 있도록 기존 direct method에 많이 사용되고 있는 amorphous seleinum 기반 digital X-ray detector가 아닌, 이러한 장점을 충족시킬 수 있는 PbI2 물질 층을 사용하여 시편을 제작 하였다. PbI2를 같은 두께로 올린 후, 물질 층 상부에 Au 전극 면적을 다른 size로 제작한 시편으로 X-ray에 노출 시켰다. 이는 상부 전극 size 차이에 따른 신호 차이를 측정하여 전기적 특성을 평가하기 위한 것이다. 전도성을 띠고 있는 ITO (Indium - Tin - Oxide) glass를 이용하여 screen printing 방법으로 제작하였다. PbI2층을 약 160~180 um두께, $3cm{\times}3cm$ size로 5개 제작하였으며, 상부 전극으로는 Au를 진공 증착 시켰다. 상부 전극 size는 각각 시편 5개에 $0.5cm{\times}0.5cm$, $1cm{\times}1cm$, $1.5cm{\times}1.5cm$, $2cm{\times}2cm$, $2.5cm{\times}2.5cm$로 PbI2 물질 층 중앙에 증착 시켰다. 이러한 설정으로 X-ray 노출 시 관찰할 수 있는 PbI2의 전기적인 특성을 평가할 수 있었다. 관전압을 40 kVp, 60 kVp, 80 kVp, 100 kVp, 120 kVp, 140 kVp로 설정하고, 관전류는 100 mA로 설정하였으며, Dark current, Sensitivity를 측정하였다. Dark current와 Sensitivity를 측정한 뒤, 그 값을 이용하여 SNR (신호 대 잡음 비)값을 구해보았다.실험 결과 단위면적당 signal과 SNR을 분석할 수 있었다. 80 kVp로 기준을 잡고 결과 값을 보면 $0.5cm{\times}0.5cm$ 시편에서 2.92 nC/cm2, $2.5cm{\times}2.5cm$ 시편에서 0.84 nC/cm2로 상부 전극 크기가 작을수록 더 좋은 신호를 측정할 수 있었다. 똑같은 기준에서 SNR을 계산 해 보았을 때, $0.5cm{\times}0.5cm$ 시편에서 6.46, $2.5cm{\times}2.5cm$ 시편에서 1.91로 SNR역시 상부 전극 크기가 작을수록 더 큰 값을 확인할 수 있었다. 이러한 결과는 edge-effect의 영향으로 인해 나온 결과라고 할 수 있다. 이러한 실험 결과, detector 제작 시, 같은 물질을 사용하여 더 높은 효율을 내기 위해서는 큰 size의 상부 전극 보다는 작은 size의 상부 전극을 증착 시키는 것이 전기적 특성을 더욱 효율적으로 평가할 수 있을 것이라고 사료된다.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.36-44
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• 2023

Core-shell TiO₂/Ag nanoparticles were synthesized by a modified sol-gel process and the reverse micelle method using acetoxime as a reducing agent in water/dodecylbenzenesulfonic acid (DDBA)/cyclohexane. The structure, shape, and size of the TiO₂/Ag nanoparticles were investigated using X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis (TGA). The size of TiO₂/Ag nanoparticles could be controlled by changing the [water]/[DDBA] molar ratio values. The size and the polydispersity of TiO₂/Ag nanoparticles increased when the [water]/[DDBA] molar ratio rose. The resultant Ag nanoparticles over the anatase crystal TiO₂ nanoparticles exhibited a strong surface plasmon resonance (SPR) peak at about 430 nm. The SPR peak shifted to the red side with the increase in nanoparticle size. Conductive pastes with 70 wt% TiO₂/Ag nanoparticles were prepared, and the pastes were coated on the PET films using a screen-printing method. The printed paste films of the TiO₂/Ag nanoparticles demonstrated greater surface resistance than conventional Ag paste in the range of 405~630 μΩ/sq.

• Applied Chemistry for Engineering
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• v.32 no.1
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• pp.28-34
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• 2021

SiO2/Ag core-shell nanoparticles were synthesized by combining modified Stöber process and reverse micelle method using acetoxime as a reducing agent in water/dodecylbenzenesulfonic acid (DDBA)/cyclohexane reverse micells. The SiO2/Ag core-shells were studied for structure, morphology and size using UV-visible spectroscopy, XRD, SEM and TEM. The size of a SiO2/Ag core-shell could be controlled by changing the [water]/[DDBA] molar ratio (WR) values. The size and the polydispersity of SiO2/Ag core-shells increased with increase of the WR value. The resultant Ag nanoparticles exhibit a strong surface plasmon resonance (SPR) peak at 430 nm over the amorphous SiO2 nanoparticles. The SPR peak shifted to the red side with increase in nanoparticle size. Conductive pastes with 70 wt% SiO2/Ag core-shell were prepared, and the pastes were coated on the PET films using a screen-printing method. The printed paste film of the SiO2/Ag core-shell showed higher surface resistance than the commercial Ag paste in the range of 460~750 µΩ/sq.

• Korean Journal of Materials Research
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• v.8 no.9
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• pp.813-818
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• 1998

Ultrafine powders of $\textrm{In}_{2}\textrm{O}_{3}$-doped $\textrm{SnO}_{2}$ were synthesized by a coprecipitation method and the effects of pH value and the amount of In2Q addition on particle size were investigated. The influence of pH value on particle size could be negligible, whereas the amount of $\textrm{In}_{2}\textrm{O}_{3}$ has influenced on particle size and specific surface area. The gas sensitivity to hydrocarbOn($\textrm{C}_{3}\textrm{H}_{8}$, $\textrm{C}_{4}\textrm{H}_{10}$) increased with $\textrm{In}_{2}\textrm{O}_{3}$ addition and reached a maximum at 3wt.% addition. From the results of impedance analysis and I-V characteristics. it was showed that the agglomeration structure of particles and the boundaries between agglomerates were the important factors to determine the gas sensing mechanism.

• Journal of the Korean Society of Radiology
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• v.3 no.2
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• pp.27-31
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• 2009

Now a days, the Medical X-ray equipments has become digitalized from analog type such as film, cassette to CR, DR. And many scientists are still researching and developing the Medical X-ray equipment. In this study, we used the Bismuth tri-iodide to conversion material for digital X-ray equipments and we couldn't get the satisfying result than previous study, but it opened new possibility to cover the disadvantage of a-Se is high voltage aplly and difficultness of make. In this paper, we use $BiI_3$ powder(99.99%) as x-ray conversion material and make films that have thickness of 200um and the film size is $3cm{\times}3cm$. Also, we deposited an ITO(Indium Tin Oxide) electrode as top electrode and bottom electrode using a Magnetron Sputtering System. To evaluate a characteristics of the produced films, an electrical and structural properties are performed. Through a SEM analysis, we confirmed a surface and component part. And to analyze the electrical properties, darkcurrent, sensitivity and SNR(Signal to Noise Ratio) are measured. Darkcurrent is $1.6nA/cm^2$ and sensitivity is $0.629nC/cm^2$ and this study shows that the electrical properties of x-ray conversion material that made by screen printing method are similar to PVD method or better than that. This results suggest that $BiI_3$ is suitable for a replacement of a-Se because of the reduced manufacture processing and improved yield.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.993-994
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• 2008

Electrochromic (EC) devices are capable of reversibly changing their optical properties upon charge injection and extraction induced by the external voltage. The characteristics of the EC device, such as low power consumption, high coloration efficiency, and memory effects under open circuit status, make them suitable for use in a variety of applications including smart windows and electronic papers. Coloration due to reduction or oxidation of redox chromophores can be used for EC devices (e-paper), but the switching time is slow (second level). Recently, with increasing demand for the low cost, lightweight flat panel display with paper-like readability (electronic paper), an EC display technology based on dye-modified $TiO_2$ nanoparticle electrode was developed. A well known organic dye molecule, viologen, was adsorbed on the surface of a mesoporous $TiO_2$ nanoparticle film to form the EC electrode. On the other hand, ZnO is a wide bandgap II-VI semiconductor which has been applied in many fields such as UV lasers, field effect transistors and transparent conductors. The bandgap of the bulk ZnO is about 3.37 eV, which is close to that of the $TiO_2$ (3.4 eV). As a traditional transparent conductor, ZnO has excellent electron transport properties, even in ZnO nanoparticle films. In the past few years, one-dimension (1D) nanostructures of ZnO have attracted extensive research interest. In particular, 1D ZnO nanowires renders much better electron transportation capability by providing a direct conduction path for electron transport and greatly reducing the number of grain boundaries. These unique advantages make ZnO nanowires a promising matrix electrode for EC dye molecule loading. ZnO nanowires grow vertically from the substrate and form a dense array (Fig. 1). The ZnO nanowires show regular hexagonal cross section and the average diameter of the ZnO nanowires is about 100 nm. The cross-section image of the ZnO nanowires array (Fig. 1) indicates that the length of the ZnO nanowires is about $6\;{\mu}m$. From one on/off cycle of the ZnO EC cell (Fig. 2). We can see that, the switching time of a ZnO nanowire electrode EC cell with an active area of $1\;{\times}\;1\;cm^2$ is 170 ms and 142 ms for coloration and bleaching, respectively. The coloration and bleaching time is faster compared to the $TiO_2$ mesoporous EC devices with both coloration and bleaching time of about 250 ms for a device with an active area of $2.5\;cm^2$. With further optimization, it is possible that the response time can reach ten(s) of millisecond, i.e. capable of displaying video. Fig. 3 shows a prototype with two different transmittance states. It can be seen that good contrast was obtained. The retention was at least a few hours for these prototypes. Being an oxide, ZnO is oxidation resistant, i.e. it is more durable for field emission cathode. ZnO nanotetropods were also applied to realize the first prototype triode field emission device, making use of scattered surface-conduction electrons for field emission (Fig. 4). The device has a high efficiency (field emitted electron to total electron ratio) of about 60%. With this high efficiency, we were able to fabricate some prototype displays (Fig. 5 showing some alphanumerical symbols). ZnO tetrapods have four legs, which guarantees that there is one leg always pointing upward, even using screen printing method to fabricate the cathode.

• Journal of the Korean Ceramic Society
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• v.49 no.5
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• pp.404-411
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• 2012

The reliability of solid oxide fuel cells (SOFCs) particularly depends on the high quality of solid oxide electrolytes. The application of thinner electrolytes and multi electrolyte layers requires a more reliable characterization method. Most of the investigations on thin film solid electrolytes have been made for the parallel transport along the interface, which is not however directly related to the fuel cell performance of those electrolytes. In this work an array of ion-blocking metallic Ti/Au microelectrodes with about a $160{\mu}m$ diameter was applied on top of an ultrathin ($1{\mu}m$) yttria-stabilized-zirconia/gadolinium-doped-ceria (YSZ/GDC) heterolayer solid electrolyte in a micro-SOFC prepared by PLD as well as an 8-${\mu}m$ thick YSZ layer by screen printing, to study the transport characteristics in the perpendicular direction relevant for fuel cell operation. While the capacitance variation in the electrode area supported the working principle of the measurement technique, other local variations could be related to the quality of the electrolyte layers and deposited electrode points. While the small electrode size and low temperature measurements increaseed the electrolyte resistances enough for the reliable estimation, the impedance spectra appeared to consist of only a large electrode polarization. Modulus representation distinguished two high frequency responses with resistance magnitude differing by orders of magnitude, which can be ascribed to the gadolinium-doped ceria buffer electrolyte layer with a 200 nm thickness and yttria-stabilized zirconia layer of about $1{\mu}m$. The major impedance response was attributed to the resistance due to electron hole conduction in GDC due to the ion-blocking top electrodes with activation energy of 0.7 eV. The respective conductivity values were obtained by model analysis using empirical Havriliak-Negami elements and by temperature adjustments with respect to the conductivity of the YSZ layers.

• Korean Journal of Materials Research
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• v.22 no.2
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• pp.103-109
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• 2012

Red-emitting $Eu^{3+}$-activated $(Y_{0.95-x}Al_x)VO_4$ (0 < x $\leq$ 0.12) nanophosphors with the particle size of ~30 nm and the high crystallinity have been successfully synthesized by a hydrothermal reaction. In the synthetic process, deionized water as a solvent and ethylene glycol as a capping agent were used. The crystalline phase, particle morphology, and the photoluminescence properties of the excitation spectrum, emission intensity, color coordinates and decay time, of the prepared $(Y_{0.95-x}Al_x)VO_4:Eu^{3+}$ nanophosphors were compared with those of the $YVO_4:Eu^{3+}$. Under 147 nm excitation, $(Y_{0.95-x}Al_x)VO_4$ nanophosphors showed strong red luminescence due to the $^5D_0-^7F_2$ transition of $Eu^{3+}$ at 619 nm. The luminescence intensity of $YVO_4:Eu^{3+}$ enhanced with partial substitution of $Al^{3+}$ for $Y^{3+}$ and the maximum emission intensity was accomplished at the $Al^{3+}$ content of 10 mol%. By the addition of $Al^{3+}$, decay time of the $(Y,Al)VO_4:Eu^{3+}$ nanophosphor was decreased in comparison with that of the $YVO_4:Eu^{3+}$ nanophosphor. Also, the substitution of $Al^{3+}$ for $Y^{3+}$ invited the improvement of color coordinates due to the increase of R/O ratio in emission intensity. For the formation of transparent layer, the red nanophosphors were fabricated to the paste with ethyl celluloses, anhydrous terpineol, ethanol and deionized water. By screen printing method, a transparent red phosphor layer was formed onto a glass substrate from the paste. The transparent red phosphor layer exhibited the red emission at 619 nm under 147 nm excitation and the transmittance of ~80% at 600 nm.