• Transactions on Electrical and Electronic Materials
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• 제7권3호
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• pp.129-133
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• 2006

Ferroelectric PZT heterolayered thick films were fabricated by the alkoxide-based sol-gel method. PZT(20/80) and PZT(80/20) paste were made and alternately screen-printed on the alumina substrates. The coating and drying procedure was repeated 4 times to form the heterolayered thick films. The thickness of the PZT heterolayered thick films was approximately $60{\mu}m$. All PZT thick films showed the typical XRD patterns of a polycrystalline rhombohedral structure. And in the PZT thick films sintered at $1100^{\circ}C$, the pyrochlore phase was observed due to the evaporation of PbO. The relative dielectric constant and the dielectric loss of the PZT thick films sintered at $1050^{\circ}C$ were 445.2 and 1.90 % at 1 kHz, respectively. The remanent polarization and coercive field of the PZT thick films sintered at $1050^{\circ}C$ were $14.15{\mu}C/cm^2$ and 19.13 kV/cm, respectively.

• 전기학회논문지
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• 제61권9호
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• pp.1296-1299
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• 2012

$YBa_2Cu_3O_{7-x}$ thin films were fabricated by the spin-coating method on $SiO_2$/Si substrate using an alkoxide-based sol-gel method. The structural and electrical properties were investigated for various 1st annealing temperature. Due to the formation of the polycrystalline single phase, synthesis temperature was observed at around $720^{\circ}C-800^{\circ}C$. $YBa_2Cu_3O_{7-x}$ thin films with the 1st annealing temperature of $450^{\circ}C{\sim}500^{\circ}C$ showed the single XRD patterns without the second phase, such as $YBa_2Cu_4O_8$. The thickness of films was approximately $0.23{\mu}m{\sim}0.27{\mu}m$. Aerage grain size, resistance and temperature coefficient of resistance (TCR) of $YBa_2Cu_3O_{7-x}$ thin films with the 1st annealing temperature of $500^{\circ}C$ were $0.27{\mu}m$, $59.7M{\Omega}$ and -3.7 %/K, respecvitely.

• 한국전기전자재료학회논문지
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• 제30권8호
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• pp.508-513
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• 2017

Ultraviolet (UV) photodetectors are used in various industries and fields of research, including optical communication, flame sensing, missile plume detection, astronomical studies, biological sensors, and environmental research. However, general UV detectors that employ Schottky junction diodes and p-n junctions have high fabrication cost and low quantum efficiency. In this study, we investigated the characteristics of materials used to manufacture UV photodetectors in a low-cost solution process that requires easy fabrication of flexible substrates. We fabricated p-type NiO and n-type ZnO substrates with wide band gap by the sol-gel method and compared the characteristics of substrates prepared under different spin-coating and heat-treatment conditions.

• 동력기계공학회지
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• 제17권4호
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• pp.115-119
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• 2013

The resistance spot welding of high strength steel degrades the weldability because of its high strength with rich chemical composition and coating layer to protect from corrosion. And the weld Expulsion is prone to occur and severely affect the nugget guality when the initial gap between automatic borrowing galvanied steel sheets(SGARC35) and Zn-coateel trip steels(GA580TRIP and GA980 TRIP) exist in resistance spot welding(RSW). RSW is one of the most popular welding processes used to join sheet metals. but weld guality sometimes do creases due to welding condition. in this paper to verity tue weldability using spot welding with the hemispherically concaved electrode, tensile shear strength and cross-tensile strength were measured by a universal test machine. in addition, the nugget size on cross-sectional area of the weld was observed by optical and electron microscopy. As a result, the nugget size of this specimen is increased with increasing welding current and Max load of tensile-shear strength is increased with welding current is increasing.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.190-190
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• 2010

Zinc oxide is the most attractive material due to the large direct band gap (3.37 eV), excellent chemical and thermal stability, and large exciton binding energy (60 meV). Recently, ZnO nanorods were used as the high efficient antireflection coating layer of solar cells based on silicon (Si). In this reports, we studied the effects of rapid thermal annealing (RTA) treatment on optical properties of ZnO nanorods. For fabrication of ZnO nanorods, there are many methods such as hydrothermal method, sol-gel method, and metal organic chemical vapor deposition method. Among of them, we used the conventional wet chemical method which is simple and low temperature growth. In order to synthesize the ZnO nanorods, the ZnO films were deposited on Si substrate by RF magnetron sputtering at room temperature and the samples were dipped to aqua solution containing the zinc nitrate and hexamethylentetramines (HMT). The synthesis process was achieved in keeping with temperature of $90-95^{\circ}C$ and under constant stirring. The morphology of ZnO nanorods on glass and Si was characterized by scanning electron microscopy. For the analysis of antireflection performance, the reflectance and transmittance were measured by spectrophotometer. And for analyzing the effects of RTA treatment on ZnO nanorods, crystalline properties were investigated by X-ray diffraction measurements and optical properties was estimated by photoluminescence spectra.

• Journal of Ceramic Processing Research
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• 제20권4호
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• pp.395-400
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• 2019

This study was conducted on the structural and electrical properties of (Ba0.7Sr0.3)TiO3 thin films prepared by the sol-gel and spin-coating methods in order to investigate their applicability to electrocaloric devices. All specimens showed a tetragonal crystal structure and lattice constants of a = 3.972 Å, c = 3.970 Å. The mean grain size of specimens sintered at 800 ℃ was about 30 nm, and the average thickness of 5 times coated specimens was 304~311 nm. In the specimen sintered at 750 ℃, The relative dielectric constant and loss of specimens measured at 20 ℃ were 230 and 0.130, respectively, while dependence of the dielectric constant on unit DC voltage was -8.163 %/V. The remanent polarization and coercive fields were 95.5 μC/㎠ and 161.3 kV/cm at 21 ℃, respectively. And, the highest electrocaloric property of 2.69 ℃ was observed when the electric field of 330 kV/cm was applied.

• Journal of Ceramic Processing Research
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• 제21권6호
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• pp.725-730
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• 2020

This study investigated the structural and electrical properties of thin K(Ta_0.6Nb_0.4)O₃ films for their applicability to electrocaloric devices. Both of the sol-gel and spin coating methods were used to fabricate thin films. Those sintered at 650 ℃ showed a KTN phase with pyrochlore of K₂Ta₂O₆, but those sintered at 750 ℃ showed pure polycrystalline phase without a pyrochlore phase. The lattice constants observed were a= 3.990nm. The dielectric constant rapidly decreased due to decrease in polarization of space charge approximately at an applied frequency of 10 kHz. The dielectric constant and loss at 30 ℃ of the thin films sintered at 750 ℃ were 3,617 and 0.264. The dielectric constant of the specimen sintered at 750 ℃ decreased to about -8.27 %/V according to the applied DC field. The remanent polarization and coercive field at 36 ℃ of the specimen sintered at 750 ℃ were 20.0 µC/cm² and 122.6 kV/cm. When the electric field of 247 kV/cm was applied to the specimen sintered at 750 ℃, the highest electrocaloric property of 3.02 ℃ was obtained.

• Journal of Ceramic Processing Research
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• 제23권5호
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• pp.583-588
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• 2022

KTN/BFO multilayer films were manufactured using the spin-coating method on Pt/Ti/SiO2/Si substrate with KTN(62/38) andBFO metal alkoxide solutions. The mean thickness of the multilayer films was about 420-450 nm. A rough interfacial layerwas observed at the interface between the lower substrate and the film when sintered at 650oC. Dense microstructures withoutpores inside of the films were shown via TEM analysis, and an interface between the KTN and BFO layers was clearlyobserved. The Curie temperature was about 16oC. Dielectric constant and dielectric loss were 1380 and 0.384 at 20oC,respectively. Coercive field of the 2-layer and 6-layer films were 72.6 and 80.4 kV/cm at room temperature, respectively. ΔTand EC coefficient of the 6-layer films sintered at 630oC were 1.96oC and 0.13×10-6 oCmV-1, respectively.

• Journal of Ceramic Processing Research
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• 제22권2호
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• pp.214-220
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• 2021

Heterolayered potassium tantalate niobate(KTN(70/30)/KTN(30/70)) thin films on Pt/Ti/SiO2/Si substrates prepared by the sol-gel process and spin coating method. When sintered at 700 ℃ or higher, the X-ray diffraction intensities of the perovskite phase were greatly increased, and it was observed as the main phase of the KTN heterolayered thin film. As the sintering temperature increased from 650 ℃ to 800 ℃, the average grain size increased from 146nm to 380 nm, and the average thickness of the KTN films coated six times was about 394-441 nm. Dielectric constant and dielectric loss of the KTN film sintered at 750 ℃ and room temperature showed good properties of about 2850 and 0.573, respectively, and all films exhibited the typical dielectric relaxation characteristics. The phase transition temperature of KTN thin film was around 12-13 ℃. Remanent polarization and the coercive field of KTN film sintered at 750 ℃ showed excellent properties of 23.98 μC/cm2 and 35.41 kV/cm, respectively. Adiabatic temperature changes (ΔT) and electrocaloric strength of the KTN films sintered at 750 ℃ at 60 ℃ were 2.67℃ and 0.012 KcmkV-1, respectively.

• 멤브레인
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• 제21권1호
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• pp.62-71
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• 2011

공기 중 산소의 분압이 높아지면 불연성인 질소의 감소로 높은 열효율을 낼 수 있으며, 고농도의 질소는 LNG선의 방폭기체 및 청과류의 신선도를 유지하는데 이용되므로 효율적인 공기 중의 산소/질소 분리 공정은 매우 중요하다. 분리막은 적은 에너지 소모로 산소와 질소를 동시에 분리 농축시킬 수 있다. 본 연구에서는 막 재료로 폴리이서설폰을, 방사용매로 NMP를 그리고 첨가제로는 비용매이면서 PES를 잘 팽윤시키는 Acetone을 사용하였다. 방사용액을 아세톤의 첨가량의 변화에 따라 0, 6.5, 15, 25, 31.5% (wt%)로 조절하여 제조하였고, 각 방사용액을 0~10 cm의 방사높이 변화에 따라 방사하였다. 제조된 중공사막은 실리콘을 코팅하여 산소 및 질소의 선택도 및 투과도를 코팅전후와 비교하여 조사하였다. Acetone의 함량 변화에 크게 관계없이 방사높이가 증가할수록 투과도는 감소하고 선택도는 증가하였다. 연신방법을 이용하여 방사한 결과 자유낙하(free fall)로 방사한 중공사막에 비해 선택도는 약간 감소하였지만 투과도는 증가하는 것으로 나타났다. 최적의 중공사막은 폴리이서설폰 37 wt%, Acetone 6.5 wt% NMP 56.5 wt%의 용액을 사용하였고, 실리콘 코팅 후에 외경 $320{\mu}m$와 7.3의 $O_2/N_2$ 선택도 및 산소투과도 4.3 GPU의 우수한 성능을 나타내었다.