• 열처리공학회지
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• 제33권1호
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• pp.13-19
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• 2020

Annealing effects on the properties of Bi-doped ZnO thin films were investigated. Bi- doped ZnO thin films were deposited on quartzs substrates at 300℃ by using radio-frequency magnetron sputtering system. Post heat treatments at 600, 700, and 800℃ were performed to evaluate the effect of annealing temperatures on the structural, optical, and electrical properties of Bi-doped ZnO thin films. FE-SEM images showed the dramatic surface morphology changes by rearrangement of elements at high heat treatment temperature of 800℃. X-ray diffraction analysis indicated that the peaks of the Bi-doped ZnO thin films were same as the peaks of the (002) planes of ZnO peak-positioned at 2θ=34.0° and peak intensities and FWHMs were improved as the annealing temperatures increased. The optical transmittance was improved with increasing annealing temperatures and was over 80% in the wavelength region between 435 and 1100 nm at the annealing temperature of 700 and 800℃. With increasing annealing temperature, the electron concentrations and electron mobilities were increased. On the other hand, electric resistivity of the films were decreased with increasing annealing temperatures. These results showed that the heat treatment temperature is an important parameter to improve the structural, optical, and electrical properties of Bi-doped ZnO thin films.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.799-801
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• 1988

This paper was studied on the effects of Ca-La-Nb substitution and Zr/Ti ratio variation to Pb(Zr, Ti)$O_3$ system on structural, electrical, optical and sound level characteristics in order to develope the piezoelectric and electrooptic ceramic devices. Also the specimens were prepared by the two stage sintering technique. The molecular formular was X($CaO{\cdot}1/4La_{2}O_{3}{\cdot}1/4Nb_{2}O_{5}){\cdot}(1-X)Pb(Zr_{Y}Ti_{1-Y})O_{3}$(x=100X, y=100Y), and the variation of x was $6{\sim}12$, y was 60${\sim}$49 and second stage sintering time was 20${\sim}$40 hours. The experimental results obtained from this study are as follows : 1. The density was decreased, the grain size was increased according to increase of Ca-La-Nb substitution. 2. The crystal structure was rhombohedral in composition 6/60/40, and the crystal structure was tetragonal and cubic according to increase of Ca-La-Nb substitution. 3. The Ca substitution of PZT system enhanced the sintering property. The Pb site vacancy resulting from the substitution of La-Nb increased the dielectrical constant, the piezoelectric charge constant, the dielectric loss and decreased the coercive field. 4. The resistivity of PZT system which has the P type conduction mechanism increased according to substitution of La-Nb because of the substituent acting as donor. 5. The PZT ceramics varied from ferroelectric substance according to increase of Ca-La-Nb substituent. The coercive field and saturation remanent polarization decreased, and at last straight line according to increase of La-Nb substitution. 6. The amount of Ca-La-Nb substitution to improve the light transmittance of speciment was 10 mol%, the Zr/Ti ratio was 49/51, and the second stage sintering time was 40 hours. 7. According to Ca-La-Nb substitution, the specimens was to be transparent. The 7.5/51/49 specimen was suitable for transparent sound vibrator because it had 58% light transmittance (thick 0.2[mm], wave length 700[mm]) and 48% electromechanical coupling factor.

• 한국표면공학회지
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• 제48권6호
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• pp.253-259
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• 2015

The test equipment becomes more important with the development of semiconductor industry. MEMS probe is an important testing component to detect the defects from the generated electric signal when it contacts the metal pad of semiconductor devices. Ni-Pd alloy has been paid attention to as a candidate of MEMS probe material because of its high surface hardness and relatively low resistivity. In this study, electroplated Ni-Pd alloy has been prepared by using ethylene diamine as a complexing agent. Solid solution alloy coating could be formed when concentration of palladium chloride and current density were in the ranges of 1~5 mM and $0.2{\sim}1.5A/dm^2$, respectively. The increase of current density brought about an decrease in palladium content, which made both of lattice parameter and grain size smaller. As a result of grain refinement, high hardness could be obtained. However, surface cracking was observed due to residual stress when the current density was above $1.3A/dm^2$. When effects of heat treatment temperature on hardness and sheet resistance were investigated, the accompanied grain growth decreased both of them. The decrease of hardness remained stable at a temperature of $200^{\circ}C$. The sheet resistance was drastically reduced at $100^{\circ}C$. After that, it was found to become constant.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.597-598
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• 2005

Recently, the performance of portable electric equipment can often improved by a Li-ion battery assisted by a supercapacitor. A supercapacitor can provide high power density as well as a low resistance in the hybrid system. In this study, we have prepared, as the pluse power souce, a commercially supplied Li-ion battery with a capacity of 700mAh and AC resistivity of $60m\Omega$ at 1kHz and nonaqeous asymmetric hybrid capacitor composed of an activated carbon cathode and MCMB anode, and have examined the electrochemical characteristics of hybrid capacitor and the pulse performances of parallel connected battery/hybrid capacitor source. The nonaqueous asymmetric hybrid capacitor, the stacks of 10 pairs of the cathode, the porous separator and the anode electrode were housed in Al-laminated film cell. The hybrid capacitor, which was charged and discharged at a constant current at $0.25mA/cm^2$ between 3 and 4.3V, has exhibited the capacitance of 100F. And the equivalent series resistance was $32m\Omega$ at 1kHz. By combining a Li-ion battery and a hybrid capacitor, the pulse performance of battery can be improved 23% in run time under a pulse discharge of 7C-rate.

• 패션비즈니스
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• 제23권2호
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• pp.1-17
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• 2019

The objective of this study was to investigate electrical conductivity of fabrics from polyester (PET) and Nylon (N) containing polyurethane (PU), with silver paste patterns screen-stenciled in three directions. The PET/PU and N/PU fabrics knitted or woven were uniaxially strain-recovered up to 22.5% in three times when each change in electrical resistance was simultaneously measured. This study established four variables that complexly affected electrical conductivity of these specimens; fabric structures, components, cover factors, and the percolation of silver particles. The woven or knitted fabric structures did not distinctively cause the changes in electrical resistance, however, the woven fabrics with the diagonal patterns showed their relatively high electrical resistance. The PET/PU fabrics with increasing the PET proportion generally presented the opposite propensity to its electrical conductivity. The changes in electric resistance of the PET/PU 85/15 2/1 twill and double plain fabrics instantaneously responded to the rate of elongation. The PET/PU group exhibited a reverse correlation between its cover factor and electrical resistivity. The highest electrical conductivity of the PET/PU 95/5 interlock fabric, with very few fluctuations, was attributed to the deep percolation of the silver particles that bridged the gaps between one loop and another. On the other hand, the occurrence of the silver cracks along with the elongated direction led to the immeasurably high change in electrical resistance as the strain increased.

• 지질공학
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• 제31권3호
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• pp.257-267
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• 2021

Constraints on the structure and composition of the active layer are important for understanding permafrost evolution. Soil convection owing to repeated moisture-induced freeze-thaw cycles within the active layer promotes the formation of self-organized patterned ground. Here we present the results of ground penetrating radar (GPR) surveys across a selected sorted circle near King Sejong Station, Antarctica, to better delineate the active layer and its relation to the observed patterned ground structure. We acquire GPR data in both bistatic mode (common mid-points) for precise velocity constraints and monostatic mode (common-offset) for subsurface imaging. Reflections are derived from the active layer-permafrost boundary, organic layer-weathered soil boundary within the active layer, and frozen rock-fracture-filled ice boundary within the permafrost. The base of the imaged sorted circle possesses a convex-down shape in the central silty zone, which is typical for the pattern associated with convection-like soil motion within the active layer. The boundary between the central fine-silty domain and coarse-grained stone border is effectively identified in a radar amplitude contour at the assumed active layer depth, and is further examined in the frequency spectra of the near- and far-offset traces. The far-offset traces and the traces from the lower frequency components dominant on the far-offset traces would be associated with rapid absorption of higher frequency radiowave due to the voids in gravel-rich zone. The presented correlation strategies for analyzing very shallow, thin-layered GPR reflection data can potentially be applied to the various types of patterned ground, particularly for acquiring time-lapse imaging, when electric resistivity tomography is incorporated into the analysis.

• 한국지반환경공학회 논문집
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• 제23권11호
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• pp.5-11
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• 2022

본 연구는 고로슬래그미분말(SG) 및 강섬유(SF)를 적용한 고유동 흙막이 벽체 재료(RWM)의 역학적 성능을 평가하기 위한 것으로써, 흙막이 벽체 재료의 재료분리저항성, 유동성, 연행공기량을 확보하기 위하여 고성능감수제, 공기연행제 및 증점안정화제를 굳지 않은 흙막이 벽체 재료에 적정량을 사용하였다. 흙막이 벽체 재료 경화체의 강도특성을 고찰하기 위하여 압축, 할열 인장 및 휨강도를 소정의 재령에서 측정하였으며, 표면전기저항, 흡수율 실험을 통하여 흙막이 벽체 재료의 역학적 성능을 평가하였다. 실험결과에 따르면 SGC 배합은 OPC 배합에 비하여 대체적으로 우수한 성능을 나타내었으며, SF는 흙박이 벽체 재료의 역학적 성능향상에 효과적인 것으로 조사되었다. 특히, SG의 사용은 흙막이 벽체 재료의 장기강도 발현 뿐만 아니라 차수성능 향상에 기여할 것으로 판단된다.

• 한국건설순환자원학회논문집
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• 제10권4호
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• pp.386-394
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• 2022

본 연구에서는 강섬유 및 나일론섬유를 적용한 섬유보강 콘크리트의 역학적 성능 및 내동해성을 실험적으로 평가하였다. 콘크리트의 역학적 성능 및 내동해성에 대한 섬유보강재의 효과를 평가하기 위하여 100 % 1종 보통포틀랜드시멘트(OPC) 콘크리트 및 50 % 대체 고로슬래그미분말(SGC) 콘크리트를 제조하였으며, 소정의 재령에서 압축 및 인장강도, 초음파펄스속도, 표면전기저항을 각각 측정하였으며, ASTM C666에 준하여 콘크리트의 상대동탄성계수 및 질량비를 측정하여 동결융해 저항성을 평가하였다. 실험결과에 의하면, 섬유보강재는 콘크리트의 역학적 성능을 효과적으로 개선시켰으며, 이러한 경향은 강섬유 적용 SGC 콘크리트에서 두드러지게 나타났다.

• 지질공학
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• 제32권4호
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• pp.525-534
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• 2022

지반 내부에 설치된 시트파일(sheet pile)의 근입 심도 확인을 위해 두 종류의 탐사기법을 활용하여 조사를 수행하였다. 탄성파탐사 원리를 활용하여 지반을 통해 전달되는 P파의 이동 속도 및 3성분 운동방향 분석을 통해 근입 심도를 추정하였다. 또한 시추공내의 전극배열에 따른 겉보기 비저항을 측정하는 전기 검층의 원리를 활용하여 단극-단극(pole-pole) 방법과 단극-쌍극(pole-dipole) 방법으로 각각 분석하여 근입 심도를 추정하였다. 그 결과, P파 검층에서 근입 심도는 9.0 m (±1.5 m), 전기검층에서 근입 심도는 7.5 m로 확인되었다. 다양한 물질들이 지반 내부에 존재하는 현장의 특성 상 전기탐사의 노이즈가 적어 탐사에 적합한 것으로 판단된다.

• 한국지반환경공학회 논문집
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• 제24권6호
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• pp.13-20
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• 2023

본 연구는 강섬유(SF) 혼입률에 따른 고유동 흙막이 벽체 재료(RWM)의 역학적 성능 및 내구성을 평가하기 위한 것으로써, 흙막이 벽체 재료의 재료분리저항성, 유동성, 연행공기량을 확보하기 위하여 적정량의 고성능감수제(SP), 공기연행제(AEA) 및 증점 안정화제(VMA)를 사용하였다. 흙막이 벽체 재료 경화체의 압축 및 쪼갬 인장강도를 소정의 재령에서 측정하였으며, 흙막이 벽체 재료의 역학적 성능은 표면전기저항성 및 흡수율 실험을 통하여 고찰하였다. 또, 염소이온 침투저항성 및 동결융해 저항성 실험을 통하여 흙막이 벽체 재료의 내구성능을 고찰하였다. 실험결과에 의하면, 강섬유를 적용한 배합이 강섬유 무혼입 배합에 비하여 우수한 성능을 나타내었으며, 2% 적용 배합이 경제성 및 성능 관점에서 상대적으로 효과적인 것으로 관찰되었다. 따라서, 적절한 SF의 적용은 흙막이 벽체 재료의 성능 향상에 기여할 것으로 판단된다.