• 마이크로전자및패키징학회지
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• 제15권1호
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• pp.27-31
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• 2008

전자 부품의 소형화 요구에 따라서 기존 기판의 상부에 실장 되는 저항 소자를 감소하기 위한 방안으로 후막 저항 페이스트를 인쇄하여 저항체를 형성 한 후에 내장하는 수동소자 내장기술이 활발히 연구되고 있다. 본 연구에서는 카본 블랙과 에폭시 수지를 혼합하여 $0.35{\sim}4k{\Omega}/sq$으로 넓은 저항 범위를 가지는 저온 열경화형 후막 저항 페이스트를 제작하였으며, Ni-Cr alloy와 $SiO_2$ 분말을 첨가하여 온도에 따른 저항 변화인 TCR(Temperature Coefficient Resistivity) 값을 $100ppm/^{\circ}C$으로 개선하였다. 최종적으로 제작된 저항 페이스트를 이용하여 내장 저항 기판을 제작하였으며 온도에 변화에 따른 안정적인 저항 특성과 신뢰성을 확보 할 수 있었다.

• 공업화학
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• 제21권4호
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• pp.411-416
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• 2010

본 연구에서는 알칼리 현상형 감광성 수지재료와 전도성 카본블랙을 이용하여 만들어진 감광성 폴리머 저항 페이스트를 이용하여 후막저항체의 허용편차(tolerance)를 개선하고자 하였다. 먼저 카본블랙과 감광성 수지의 선택이 폴리머 후막저항(polymer thick film resistor, PTFR)의 저항값의 범위와 허용편차의 수준에 미치는 영향을 조사하였다. 이후 테스트 기판상에 감광성 저항 페이스트를 도포하는 방법에 따른 저항값 허용편차의 차이를 평가하였다. 감광성 저항 페이스트를 스크린 인쇄를 이용하여 테스트 기판의 전면에 도포한 경우에는 테스트 기판상에서 균일한 두께의 후막을 형성하기 어렵기 때문에 위치에 따른 저항값의 허용편차가 크게 나타났다. 반면, 롤러를 이용하여 페이스트를 도포하였을 때, 전체 기판 면적에 균일한 두께의 저항체 후막을 형성할 수 있었으며, 저항값 평가 결과 ${\pm}10%$ 이내의 낮은 허용편차를 나타내었다. 포토공정을 이용한 정밀한 패터닝 공정과 롤러를 이용한 균일한 두께의 저항막 도포 공정을 결합함으로써 후막저항의 허용편차를 개선할 수 있었다.

• 한국염색가공학회지
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• 제32권4호
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• pp.245-254
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• 2020

The sheet molding compound composite has been applied divers section. This paper reports processing of carbon fiber reinforced thermosetting composite with diverse resins and which was composed of chopped carbon fiber (30 ~ 60 wt%). Normally the paste that the viscosity is over 15,000 cps has been used in traditional Sheet molding compound (SMC) machine. In this research, SMC machine was designed to make Carbon-sheet molding compound (C-SMC) prepreg which was composed with low viscosity resin (1,800 ~ 2,500 cps increase up to 10,000 cps after aging). In order to confirm the optimal processing condition. Mechanical strength tests including tensile test, shear test, impact test, flexural strength test were conducted on C-SMC composites. Plus we identified the correlation between the mechanical properties and prepreg processing condition (carbon ratio and applied resin).

• 폴리머
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• 제33권5호
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• pp.397-406
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• 2009

유기 박막 트랜지스터 (OTFTs)의 소스-드레인 전극을 스크린 인쇄를 통해 제작하였고, 전극용 페이스트로써 전도성 카본블랙 페이스트를 사용하였다. 전도성 카본블랙 페이스트를 제조하기 위해 서로 다른 분자량 및 고분자 사슬 구조를 갖는 2종류의 분산제(DB-2150, DB-9077)를 사용하여 분산제 함량(SOF; solid on powder, 10-40%)에 따른 카본블랙 밀베이스의 분산 특성을 검토한 결과, 분산제 함량이 증가함에 따라 분산 특성이 더 우수해 짐을 알 수 있었다. 전도성 카본블랙 페이스트를 제조하여 레올로지 측정을 통해 카본블랙의 분산상태 및 응집구조에 대해 검토한 결과, 분산제로 DB-2150을 사용한 페이스트들은 분산제 함량이 증가함에 따라 페이스트의 분산 특성이 향상되어 저장 탄성률(G')이 감소하였지만, DB-9077을 사용한 페이스트들은 카본블랙 사이의 상호작용에 의해 망목구조가 존재하였고, 분산제 함량이 증가함에 따라 카본블랙과 분산제간 또는 분산제간의 상호작용에 의해 페이스트의 저장 탄성률(G')은 더욱 증가하였다. 이러한 응집구조는 페이스트의 내부 저항력 (tacky)을 발생시켜 DB-9077을 사용한 페이스트들은 분산제 함량이 증가함에 따라 스크린 인쇄 적성이 좋지 못하였다. 하지만, 스크린 인쇄된 OTFTs용 소스-드레인 전극의 전기적 특성은 카본블랙 사이에 형성된 망목구조에 의해 카본블랙의 도전 경로(conduction Path)가 형성됨에 따라 DB-2150을 사용한 페이스트들의 OTFTs에 비해 더 우수하였다. 그러나, 2종류의 분산제를 사용한 페이스트 모두, 분산제의 함량이 증가함에 따라 카본블랙 표면을 감싸는 분산제 함량 또한 증가하게 되어 이로 인해 카본블랙간의 도전 경로 형성은 어렵게 되고 전극의 특성은 점점 열화되었다.

• 한국건축시공학회지
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• 제14권1호
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• pp.68-75
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• 2014

In order to increase the integrity of the wellbore which is used to prevent the leakage of supercritical $CO_2$, it is necessary to develop a concrete that is strongly resistant to carbonation. In an environment where the concentration of $CO_2$ is exceptionally high, $Ca^{2+}$ ion concentration in pore solution of Portland cement concrete will drop significantly due to the rapid consumption of calcium hydroxide, which decreases the stability of the calcium silicate hydrate. In this research, calcium phosphates were used to modify Portland cement system in order to produce hydroxyapatite, a hydration product that is strongly resistant to carbonation under such an environment. According to the experimental results, calcium phosphates reacted with Portland cement to form hydroxyapatite. The formation of hydroxyapatite was verified using X-ray diffraction analyses with selective extraction techniques. When using dicalcium phosphate dihydrate and tricalcium phosphate, the 28-day compressive strength was lower than that of plain cement paste. However, the specimen with monocalcium phosphate monohydrate showed equivalent strength to that of plain cement paste.

• 한국응용과학기술학회지
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• 제29권2호
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• pp.302-310
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• 2012

Bio assay of mercury and cadmium ions were searched using voltammetric analysis using DNA doped carbon nanotube paste electrodes (DCP). The square-wave stripping voltammetryic optimized results indicated working ranges of 1-10.0 $ngL^{-1}$ and 20-100 $ugL^{-1}$, Hg(II) Cd(II) within an accumulation time of 120 seconds, in 0.1-M phosphate buffer solutions of pH 6.3. The relative standard deviations of 5 $ngL^{-1}$ Hg(II) and Cd(II) that observed were 0.14 and 0.22% (n=12), respectively, using optimum conditions. The low detection limit (S/N) was pegged at 0.1 $ngL^{-1}$ ($4.9{\times}10^{-11}M$) Hg(II) and 0.2 $ngL^{-1}$ ($1.77{\times}10^{-10}M$) Cd(II). The developed methods can be applied to assays in biological fish kidneys and water samples.

• 센서학회지
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• 제23권3호
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• pp.170-172
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• 2014

$CO_2$ sensor was used only one solid electrolyte in many cases. To improve the sensing characteristics of $CO_2$ sensors, solid electrolyte $CO_2$ sensor has been developed by bi-electrolyte type sensor using Na-Beta-alumina and YSZ. However, in many further studies, bi-electrolyte type sensor was made by pellet pressed by press machine and additional treatment for formation of interface. In the aspect of mass production, using thick film and additional treatment is not suitable. In this study, $CO_2$ sensor was fabricated by bi-electrolyte structure which was made by an NBA paste layer deposited on YSZ pellet and fired at $1650^{\circ}C$ for 2 hour. The formation of stable interface between YSZ and NBA were confirmed by SEM image. When the type IV electrochemical cell arrangement represented by $CO_2,O_2,Pt{\mid}Li_2CO_3-CaCO_3{\parallel}NBA{\parallel}YSZ{\mid}O_2,Pt$ is used to measure the $CO_2$ concentration in air. This sensor EMF should depend only on the concentration of $CO_2$ by logarithmic. Also, sensor shows $P_{CO_2}$ and EMF relationship like nerstian reaction at a temperature of $450^{\circ}C$.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.172-173
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• 2021

With the development of nano-reinforcement technology and the increasing concern for environmental issues, TiO₂ nanomaterials have received wide attention as an additive besides carbon nanomaterials that can be used to enhance the mechanical properties of cement-based materials. Also, TiO₂-based materials can allow cement-baned materials with photocatalytic capability, providing a potentially effective approach to reduce environmental problems. In this work, compressive strength, splitting tensile strength, and degradation of methylene blue solution were used as target to assess the effect of TiO₂ nanotubes on the mechanical strength and photocatalytic effect of hardened cement paste at different curing time. According to the strength results, the optimum amount of TiO₂ was identified as 0.5% of the weight of cement. Meanwhile, the TiO₂ nanotubes-reinforced specimen exhibited better photocatalytic effect in the early stage of curing.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.115-116
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• 2023

This study aims to investigate and improve the carbon dioxide sequestration capability and the mechanical properties of non-hydraulic low calcium silicate cement especially designed for CO₂ reaction and ordinary Portland cement subjected to the carbonation curing facilitating pH swing method. Nitric acid (HNO₃) was utilized as an liquid for the mixing of cement paste to enhance the initial dissolution of Ca ions from the cements by promoting low pH environment and prevent the direct precipitation of Ca with the anion, owing to the high solubility of Ca(NO₃)₂ in water. The results presented that the higher the concentration of HNO₃, the higher the compressive strength and CO₂ sequestration (until 0.1 M). Ca dissolution caused by the harsh acid attack onto the anhydrous cement particle lead to the higher carbonation reaction degree, forming abundant CaCO₃ crystals after the reaction. However, cement paste mixed with excessively high concentration of HNO₃ presented deterioration due to the too harsh pH environment and abundant NO₃- ions which are known to retard the reaction of cement.

• 대한건축학회논문집:구조계
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• 제34권3호
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• pp.37-42
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• 2018

The use of fly ash in construction materials is increasing worldwide due the various advantages of using it, such as to produce durable concrete, or to use less cement and thus lower carbon dioxide emissions. The quality of fly ash is often determined by loss on ignition value (LOI), where an upper limit of LOI is set in each country for quality control purpose. However, due to many reasons, production of high LOI fly ash is increasing that cannot be utilized in concrete, ending up in landfill. In this study, the effect of fly ash use in cementitious materials on nitrogen oxides adsorption is examined. In particular, the effect of using high LOI, and thus high carbon content fly ash on nitrogen oxides adsorption is investigated. The results suggest that the higher carbon content fly ash is related to higher nitrogen dioxide adsorption, although normal fly ash was also more effective in nitrogen dioxide adsorption than ordinary portland cement. Also, higher replacement rate of up to 40% of fly ash is beneficial for nitrogen dioxide adsorption. These results demonstrate that high carbon fly ash can be used as construction materials in an environmentally friendly way where strength requirement is low and where nitrogen oxides emissions are high.