• 센서학회지
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• 제18권5호
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• pp.343-348
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• 2009

$NiO{\cdot}(Co_{0.25}Mn_{0.75})_2O_3$(Mn-Ni-Co) and $Ba_{0.5}Sr_{0.5}TiO_3$(BST) thick films were screen printed on Pt patterned alumina substrate to investigate the effects of sintering temperature on humidity and temperature sensing properties of ceramic sensors. A raise in sintering temperature increased resistance and B constant of the Mn-Ni-Co temperature sensor. This may have derived from the synergic effects of the reduction in charge carriers caused by the substitution of Co for Mn as well as the formation of microcracks from the difference in thermal expansion coefficients. Dependence of resistance on humidity of the Mn-Ni-Co temperature sensor, however, was not found. BST films sintered at temperatures in the range of $1100^{\circ}C$ to $1150^{\circ}C$ showed excellent humidity sensing properties. The BST humidity sensor was faster in its response than the Mn-Ni-Co temperature sensor. The humidity sensor, however, proved to be unstable under various temperatures, suggesting a need for a temperature stabilizing device. In contrast, the Mn-Ni-Co temperature sensor was stable under humid conditions.

• 센서학회지
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• 제3권2호
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• pp.40-49
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• 1994

$CaF_{2}$ 불화물 고체전해질을 모물질로하는 저온동작용($300^{\circ}C{\sim}$500^{\circ}C) 산소센서를 제조하였다. $CaF_{2}$ 산소센서는 수축률과 SEM사진의 결과를 토대로 $850^{\circ}C$-3hr 동안 열처리 하였다. 디스크형 산소 센서는 기준전극으로 Air($O_{2}:21%$)|Pt를, 전해질로는 $CaF_{2}$, 감지전극으로 Pt를 사용하였으며, 기준전극 내장형 산소센서는 기준전극으로 NiO/Ni (30:70)을 사용하였다. 디스크형 산소센서의 경우 측정온도 $400^{\circ}C$에서 산소농도($0.1 %{\sim}10%$)로 변화시 45mV 정도의 기전력 변화를 보였으며, 기준전극 내장형의 경우는 40mV의 변화를 보였다.

• 한국진공학회지
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• 제12권S1호
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• pp.17-20
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• 2003

We have studied magnetic and structural properties of ultrathin Ni films grown on PI(lII) surface using in situ surface magneto-optic Kerr effect and X-ray photoelectron spectroscopy. Perpendicular magnetic anisotropy was absent, and longitudinal Kerr signal was only detectable for Ni films thicker than 6 monolayers. Enhancement in longitudinal Kerr signal by 30% was achieved by post-annealing at temperatures below 800K, but upon annealing at 820K, surface alloy was formed. By using core-level binding-energy shifts, the composition was determined to be Ni 70 at. %.

• 센서학회지
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• 제21권6호
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• pp.425-428
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• 2012

This paper presents the fabrication and characterization of graphene based hydrogen sensors. Graphene was synthesized by annealing process of Ni/3C-SiC thin films. Graphene was transferred onto oxidized Si substrates for fabrication of chemiresistive type hydrogen sensors. Au electrode on the graphene shows ohmic contact and the resistance is changed with hydrogen concentration. Nanoparticle catalysts of Pd and Pt were decorated. Response factor and response (recovery) time of hydrogen sensors based on the graphene are improved with catalysts. The response factors of pure graphene, Pt and Pd doped graphenes are 0.28, 0.6 and 1.26, respectively, at 50 ppm hydrogen concentration.

• E2M - 전기 전자와 첨단 소재
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• 제6권6호
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• pp.537-544
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• 1993

기본조성이 0.5[Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_{3}$]-0.5[0.65PbTiO$_{3}$ -0.35PbZrO$_{3}$] (PNN-PT-PZ)인 압전세라믹스를 NaCl-KCI를 사용한 flux의 양 및 소결온도에 따른 생성반응과 소결특성, 유전 및 압전특성을 조사하였다. 이때 1몰의 산화물에 대한 flux의 양은 0.1, 2 및 5mole로 하였으며 소결온도는 1000-1200.deg.C로 하였다. 본 연구의 flux법은 고상반응법에 비해 낮은 하소온도에서 pyrochlore상을 현저히 줄일수 있었으며 고상반응법보다 낮은 온도에서 치밀화가 이루어질뿐 아니라 유전 및 압전특성을 개선할 수 있었으며 소결온도도 낮출 수 있었다. Flux의 양이 증가할수록 결정의 입성장이 빨랐으며 유전 및 압전특성이 가장 좋은 flux의 첨가량의 조건은 1mole이었다.

• 센서학회지
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• 제13권2호
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• pp.152-156
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• 2004

The dielectric and piezoelectric properties of 0.36Pb($Sc_{1/2}Nb_{1/2}$)$O_{3}$-0.25Pb($Ni_{1/3}Nb_{2/3}$)$O_{3}$-0.39Pb$TiO_{3}$ (hereafter PSNNT) at the morphotropic phase boundary (MPB) composition were investigated with $0{\sim}2.5$ mot% $MnO_{2}$ doping. Bulk density, dielectric loss and tetragonality of crystal structure were all improved with increasing $MnO_{2}$ additive content. With increasing $MnO_{2}$ additive content, the electromechanical coupling factor and quality factor were also increased: Electromechanical coupling $k_{p}$ and quality factor $Q_{m}$ at 2.0 mol% $MnO_{2}$ doping with were showed highest values of 55.6 % and 252, respectively.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.141-145
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• 2007

Due to their excellent catalytic activity with respect to methanol oxidation on platinum at low temperature, platinum nanosized catalysts have been a topic of great interest for use in direct methanol fuel cells (DMFCs). Since pure platinum is readily poisoned by CO, a by-product of methanol electrooxidation, and is extremely expensive, a number of efforts to design and characterize Pt-based alloy nanosized catalysts or Pt nanophase-support composites have been attempted in order to reduce or relieve the CO poisoning effect. In this review paper, we summarize these efforts based upon our recent research results. The Pt-based nanocatalysts were designed by chemical synthesis and thin-film technology, and were characterized by a variety of analyses. According to bifunctional mechanism, it was concluded that good alloy formation with $2^{nd}$ metal (e.g., Ru) as well as the metallic state and optimum portion of Ru element in the anode catalyst contribute to an enhanced catalytic activity for methanol electrooxidation. In addition, we found that the modified electronic properties of platinum in Pt alloy electrodes as well as the surface and bulk structure of Pt alloys with a proper composition could be attributed to a higher catalytic activity for methanol electooxdation. Proton conducting contribution of nanosized electrocatalysts should also be considered to be excellent in methanol electrooxidation (Spillover effect). Finally, we confirmed the ensemble effect, which combined all above effects, in Pt-based nanocatalsyts especially, such as PtRuRhNi and $PtRuWO_{3}$, contribute to an enhanced catalytic activity.

• 한국전기전자재료학회논문지
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• 제18권2호
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• pp.169-173
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• 2005

Ni oxide thin films were formed through annealing treatment in the atmosphere after Ni thin films deposited by a r.f. magnetron sputtering method and then electric and material properties were analyzed for application to thermal sensors. Resistivity of Ni thin films decreased after annealing treatment at 30$0^{\circ}C$ and 40$0^{\circ}C$ for five hours due to crystallization of Ni thin films but the value increased over 45$0^{\circ}C$ because of Ni thin film's oxidation. Resistivity values of Ni thin films were in the range of 10.5 $\mu$Ωcm/$^{\circ}C$ to 2.84${\times}$10$^4$$\mu$Ωcm/$^{\circ}C$ according to the degree of Ni oxidation. Also temperature coefficient of resistance(TCR) values of Ni oxide thin films depended on the degree of Ni oxidation such as 2,188 ppm/$^{\circ}C$ to 5,630 ppm/$^{\circ}C$ in the temperature range of 0 $^{\circ}C$∼150 $^{\circ}C$. The results demonstrate that Ni oxide thin films of annealing treatment at 40$0^{\circ}C$ for 5hours could be more advantageous than pure Ni thin films and Pt thin films from a point of output properties and TCR, applied to thermal sensors.

• 공업화학
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• 제25권1호
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• pp.78-83
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• 2014

본 연구에서는 수정된 폴리올법에 의해 합성된 백금-이트륨 및 백금-니켈 합금 촉매들의 성능 및 특성 평가를 진행하였다. 그렇게 합성된 합금 촉매들은 고분자전해질연료전지의 공기극 촉매로 사용되며 그 촉매들의 산소환원반응성 및 연료전지의 전기적 성능이 측정되고 상업적으로 사용되는 백금 촉매와 해당하는 결과들이 비교되었다. 성능 및 특성 비교를 위해, 백금 합금 촉매들의 입자크기와 분포는 투과전자현미경에 의해 관측되었고 활성표면적은 반복주사 전압-전류법에 의해 측정되었으며 그들의 산소환원반응성 및 연료전지의 전기적 성능은 회전원판 및 회전-고리 원판전극을 이용한 선형주사 전압-전류법 및 완전지 테스트를 통해 평가되었다. 그 결과 백금 합금 촉매들의 구조적 특성인 입자크기 및 분포 및 활성표면적은 상용 백금 촉매와 그 특성이 비슷하였다. 촉매들의 산소환원반응성의 경우에도 백금 합금 촉매들은 상용 백금 촉매와 비슷하거나 더 나은 반파장전위, 속도론적 전류밀도, 산소분자당 전이되는 전자수, 과산화수소 생성율을 나타내었다. 촉매의 구조적 특성 및 산소환원반응성에 입각해서 완전지 성능을 평가했을 때, 백금 합금 촉매들은 상용백금 촉매보다 더 우수한 0.6 V에서 전류밀도 및 최대출력밀도 값을 나타내었다. 이를 토대로 수정된 폴리올법에 의해 합성된 백금 합금 촉매들은 상용백금 촉매보다 비슷하거나 우수한 산소환원반응성 및 완전지 성능을 가질 수 있음을 제시하였다.

• Transactions on Electrical and Electronic Materials
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• 제8권4호
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• pp.161-165
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• 2007

In this work, Ni thin films with different thickness from $1,523{\AA}\;to\;9,827{\AA}$ were deposited for the application of micro thermal flow sensors by a magnetron sputtering and oxidized through annealing at $450^{\circ}C$ with increasing annealing time. The initial variation of resistivity decreased radically with increasing films thickness, then gradually stabilizes as the thickness increases. The resistivity of Ni thin films with $3,075{\AA}$ increased suddenly with increasing annealing time at $450{\circ}C$, then gradually stabilizes as the thickness increases after the annealing time 9 h. In case of $3,075{\AA}\;and\;9,827{\AA}$ films, the average of TCR values, measured for the operating temperature range of $0^{\circ}C\;to\;180^{\circ}C$, were $2,413.1ppm/^{\circ}C\;and\;4,438.5ppm/^{\circ}C$, respectively. Because of their high resistivity and very linear TCR, Ni oxide thin films are superior to pure Ni and Pt thin films for flow and temperature sensor applications.