• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3835-3839
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• 2013

A new synthesis route for Pt nanoparticles by direct electrochemical reduction of a solid-state Pt ion precursor ($K_2PtCl_6$) is demonstrated. Solid $K_2PtCl_6$-supported polyethyleneimine (PEI) coatings on the surface of glassy carbon electrode were prepared by simple mixing of solid $K_2PtCl_6$ into a 1.0% PEI solution. The potential cycling or a constant potential in a PBS (pH 7.4) medium were applied to reduce the solid $K_2PtCl_6$ precursor. The reduction of Pt(IV) began at around -0.2 V and the reduction potential was ca. -0.4 V. A steady state current was achieved after 10 potential cycling scans, indicating that continuous formation of Pt nanoparticles by electrochemical reduction occurred for up to 10 cycles. After applying the reduction potential of -0.6 V for 300 s, Pt nanoparticles with diameters ranging from $0.02-0.5{\mu}m$ were observed, with an even distribution over the entire glassy carbon electrode surface. Characteristics of the Pt nanoparticles, including their performance in electrochemical reduction of $H_2O_2$ are examined. A distinct reduction peak observed at about -0.20 V was due to the electrocatalytic reduction of $H_2O_2$ by Pt nanoparticles. From the calibration plot, the linear range for $H_2O_2$ detection was 0.1-2.0 mM and the detection limit for $H_2O_2$ was found to be 0.05 mM.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.33.1-33.1
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• 2018

pH is expressed mathematically as $pH=-{\log}[H^+]$, is a measure of the hydrogen ion concentration, [$H^+$] to specify the acidity or basicity of an aqueous solution. The pH scale usually ranges from 0 to 14. Every aqueous solution can be measured to determine its pH value. The pH values below 7.0 express the acidity, above 7.0 are alkalinity and pH 7.0 is a neutral solution. The solution pH can be determined by indicator or by measurement using pH sensor, which measuring the voltage generated between a glass electrode and a reference electrode according to the Nernst Equation. The pH value of solutions depends on the temperature and the activity of contained ions. In nickel electroless plating process, the controlled pH value in some limited ranges are extremely important to achieve optimal deposition rate, phosphorus content as well as solution stability. Basically, nickel electroless plating solution contains of $Ni^{2+}ions$, reducing agent, buffer and complexing agents. The plating processes are normally carried out at $82-92^{\circ}C$. However, the change of its pH values with temperatures does not follow any rule. Thus, the purpose of study is to understand the relationship between pH and temperature of some based solutions and electroless nickel plating solutions. The change of pH with changing temperatures is explained by view of the thermal dynamic and the practical measurements.

• 전기전자학회논문지
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• 제26권2호
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• pp.219-225
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• 2022

우리나라의 섬유산업 중 염색가공 분야는 에너지 다소비 업종으로, 노동 집약적 특성에 따라 원단위 생산성이 낮고, 대부분 중소·영세기업 특징이 있다. 염색 원단의 불량률이 높아지면 재염색으로 인한 생산단가 상승과 초과 에너지 투입으로 비용이 증가하기 때문에, 불량률을 최소를 통한 생산량 향상이 초점이었다. 또한 고온고압의 환경에서 이루어지는 염색공정은 사고 위험으로 염색기 원단 투입구를 실시간으로 개방할 수 없기 때문에 실시간으로 원단의 염색상태 확인이 어려웠다. 최근에는 염액을 실시간으로 모니터링하는 연구가 활발히 진행중이다. 본 논문에서는 탁도, pH, 전도도 센서를 이용하여 염액의 흡진율을 계측할 수 있는 복합센서 흡진율 모델 및 구성시스템을 제안하였으며, 실험방법소개와 실험결과 분석을 실시하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.222-222
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• 2012

Metal oxide gas sensors based on semiconductor type have attracted a great deal of attention due to their low cost, flexible production and simple usability. However, most works have been focused on n-type oxides, while the characteristics of p-type oxide gas sensors have been barely studied. An investigation on p-type oxides is very important in that the use of them makes possible the novel sensors such as p-n diode and tandem devices. Monoclinic cupric oxide (CuO) is p-type semiconductor with narrow band gap (~1.2 eV). This is composed of abundant, nontoxic elements on earth, and thus low-cost, environment-friendly devices can be realized. However, gas sensing properties of neat CuO were rarely explored and the mechanism still remains unclear. In this work, the neat CuO layers with highly ordered mesoporous structures were prepared by a template-free, one-pot solution-based method using novel ink solutions, formulated with copper formate tetrahydrate, hexylamine and ethyl cellulose. The shear viscosity of the formulated solutions was 5.79 Pa s at a shear rate of 1 s-1. The solutions were coated on SiO2/Si substrates by spin-coating (ink) and calcined for 1 h at the temperature of $200{\sim}600^{\circ}C$ in air. The surface and cross-sectional morphologies of the formed CuO layers were observed by a focused ion beam scanning electron microscopy (FIB-SEM) and porosity was determined by image analysis using simple computer-programming. XRD analysis showed phase evolutions of the layers, depending on the calcination temperature, and thermal decompositions of the neat precursor and the formulated ink were investigated by TGA and DSC. As a result, the formation of the porous structures was attributed to the vaporization of ethyl cellulose contained in the solutions. Mesoporous CuO, formed with the ink solution, consisted of grains and pores with nano-meter size. All of them were strongly dependent on calcination temperature. Sensing properties toward H2 and C2H5OH gases were examined as a function of operating temperature. High and fast responses toward H2 and C2H5OH gases were discussed in terms of crystallinity, nonstoichiometry and morphological factors such as porosity, grain size and surface-to-volume ratio. To our knowledge, the responses toward H2 and C2H5OH gases of these CuO gas sensors are comparable to previously reported values.

• 센서학회지
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• 제1권2호
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• pp.173-181
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• 1992

RP 반응성 스펏터링으로서 P형 실리콘 웨이퍼위에 $Ta_{2}O_{5}$막을 제조하였다. 시편의 구조 및 조성은 XRD와 AES로 조사하였다. 산소의 혼합비가 10%일 때 C-V 특성으로부터 구한 $Ta_{2}O_{5}$막의 비유전률은 10-12이었다. AES와 RBS로 측정한 $Ta_{2}O_{5}$막의 Ta : O의 비는 각각 1 : 2와 1 : 2.49로 나타났으며, 산소분위기에서 $700^{\circ}C$의 열처리 온도에서 결정성장이 시작되었다. 산소분위기에서 $1000^{\circ}C$로 열처리한 $Ta_{2}O_{5}$막의 비유전률값은 20.5였으며, 질소분위기에서 열처리한 경우의 비유전률값은 23으로 나타났다. 이 때 가육방전계(pseudo hexagonal ${\delta}-Ta_{2}O_{5}$)의 결정구조를 나타내었다. 시편의 ${\Delta}V_{FB}$와 누설전류밀도는 산소의 혼합비가 증가함에 따라 감소하였다. 그리고 최대절연파괴전장은 산소가 10% 혼합되었을 때 2.4MV/cm로 나타났다. 이러한 $Ta_{2}O_{5}$막은 수소이온 감지막 및 기억용소자의 게이트 절연막 등에 응용될 수 있을 것이다.