• 한국구조물진단유지관리공학회 논문집
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• 제26권3호
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• pp.72-83
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• 2022

본 논문에서는 전도성 재료인 탄소섬유(carbon fiber, CF)와 강섬유(steel fiber, SF)를 함유한 시멘트 모르타르의 미세구조 및 전기적 특성, 압축강도에 미치는 영향을 연구하였다. 전도성 섬유보강 시멘트 모르타르(fiber-reinforced cement mortar, FRCM)의 비저항은 4-probe 방법을 이용하여 측정하였고, 압축강도는 압축시험을 기반으로 측정하였다. 이들의 성능은 플레인 모르타르(plain mortar, PM)와 비교, 검토하였다. 게다가 전도성 FRCM 파단면의 표면형상과 구성성분은 주사전자현미경(scanning electron microscope, SEM)과 에너지 분산형 X-ray 분광분석기(energy disperse X-ray spectrometer, EDS)를 이용하여 분석하였다. 그 결과 모든 시편에서 양생재령이 경과됨에 따라 비저항이 점차 증가하는 반면, 섬유혼입률이 증가할수록 비저항은 상당히 감소하였다. 강섬유를 1.25%까지 추가하여도 시멘트 모르타르의 비저항에는 크게 영향을 미치지 않았다. 대조적으로, 탄소섬유는 낮은 함량(즉, 0.1~0.3%)에서도 비저항이 다소 감소하였고, 그 이후에는 현저히 저하되었다. 본 실험에 사용된 CF가 함유된 전도성 CFRCM의 침투 임계점은 0.4%이었고, 압축강도 성능을 유지하면서 전도성 효과를 극대화하는 최적의 탄소섬유 혼입량이라고 판단된다. 전도성 FRCM의 표면형상 및 구성성분 분석을 위해 SEM/EDS를 통해 파단면을 관찰하였다. 이러한 결과는 시멘트 모르타르 내에서 보강섬유의 미세구조 메커니즘을 확립하는 데 매우 유용할 것으로 사료된다.

• 한국진공학회지
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• 제10권1호
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• pp.87-92
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• 2001

자기 Fe-Co(C)나노(nano)캡슐과 Fe-Co 나노입자들이 메탄과 혼합기체($H_2$+Ar) 두 종류의 분위기속에서 각각 아크방전으로 제조되었다. 이 두 종류의 초미세 입자들의 특성과 자기적 성질들을 XRD(X-ray Diffraction), Mossbauer 분광, XPS(X-ray Photoelectron Spectroscopy), TEM(transmission Electron Microscopy), EDS(Energy Disperse Spectroscopy), 화학적 분석, 산소량 측정과 자기 측정 등을 통하여 체계적으로 조사하였다. 메탄기체로부터 분해되어 나온 탄소원소가 미세입자들의 상구조, 자기적 상태 그리고 표면 특성들에 끼치는 효과를 아르곤원소를 사용했을 때와 비교하였다. 두 미세입자에서의 Fe/Co 질량비가 약간 다르게 나타났으며 Fe-Co나노입자의 크기가 Fe-Co(C)나노캡슬보다 약 두배였다. 또한 Fe-Co(C)나노캡슐의 포화자화값이 Fe-Co 나노입자보다 약 8% 높았으며 둘 다 유사한 상구조를 보였다. 핵 표면에 쌓인 껍질들이 매우 얇아 XRD측정으로는 그 존재를 탐지하기 어려웠으나 XPS분석을 통하여 그들이 탄소층과 산소층임을 결론지을 수 있었다.

• Carbon letters
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• 제7권1호
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• pp.34-41
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• 2006

The objective of this paper is to compare the variation of surface properties by hydrochloric acid pre-treatment and of metallic potassium and their salts loading effect for activated carbon after surfaces transformation by acid. From the results of nitrogen adsorption, each isotherm shows a distinct knee band, which is closely related to the characteristic of microporous carbons with capillary condensation in micropores. In order to present the causes of the differences in surface properties and $S_{BET}$ after the samples were treated with hydrochloric acid, pore structure and surface morphology are investigated by adsorption analysis. X-ray diffraction (XRD) patterns indicate that activated carbons show better performance for metallic potassium and potassium salts by pre-treatment with hydrochloric acid. Scanning electron microscopy (SEM) pictures of potassium/activated carbon particles provide information about the homogeneous distribution of metal or metal complex on the surface. For the chemical composition microanalysis for potassium treatment of the activated carbon pre-treated with hydrochloric acid, samples were analyzed by energy disperse X-ray (EDX). Finally, the type and quality of oxygen groups are determined from the method proposed by Boehm. A positive influence of the acidic groups on the carbon surface by acid treatment is also demonstrated by an increase in the contents of potassium salts with increasing of acidic groups calculated from Boehm titration.

• 대한치과기공학회지
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• 제27권1호
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• pp.97-104
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• 2005

The effect of Nb on interfacial bonding characteristics of Ni-Cr alloy for porcelain fused to metal crown (PFM) has been studied in order to investigate oxide layer. A specimens, which is 0.8mm in thickness, were fired at 1,000$^{\circ}C$ with four tests such as air, vacuum, air for 5 minutes and vacuum for 5 minutes in order to examine an oxide behavior of alloy surface generated by the adding of Nb to be controlled at a rate of 0, 1, 3 and 5. It observed oxide film form of the fired specimens with optical microscope and scanning electron microscope (SEM), and chemical formation of them with energy disperse X-ray spectroscopy (EDX). The other specimens, which is 2mm in thickness, were fired at 1,000$^{\circ}C$ with air and vacuum in order to analyze the diffusion behaviors of alloy-porcelain interface by X-ray dot mapping. The results of this study were as follows: 1. The observation of microstructure of specimens by SEM showed that the more Nb content is high, the more much intermediate compound of rich Nb is observed. 2. The surface morphology of oxide film is most dense in 3% Nb. The heat treatment in air constitutes denser oxide film than heat treatment under vacuum. 3. The diffusion behavior of oxide layer by X-ray dot mapping showed that Si, Al of porcelain diffuse toward metal.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.286-287
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• 2012

Reset-first resistive switching mechanism based on reduction reaction in HfO2-x with oxygen drift-diffusion was studied. we first report that the indirect evidence of local filamentary conductive path formation in bulk HfO2 film with local TiOx region at Ti top electrode formed during forming process and presence of anion-migration at interface between electrode and HfO2 during resistive switching through high resolution transmission electron microscopy (HRTEM), electron disperse x-ray (EDX), and electron energy loss spectroscopy (EELS) mapping. Based on forming process mechanism, we expected that redox reaction from Ti/HfO2 to TiOx/HfO2-x was responsible for an increase of initial current with increasing the post-annealing process. First-reset resistive switching in above $350^{\circ}C$ annealed Ti/HfO2 film was exhibited and the redox phenomenon from Ti/HfO2 to TiOx/HfO2-x was observed with high angle annular dark field (HAADF) - scanning transmission electron microscopy (STEM), EDX and x-ray photoelectron spectroscopy. Therefore, we demonstrated that the migration of oxygen ions at interface region under external electrical bias contributed to bipolar resistive switching behavior.

• 분석과학
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• 제19권3호
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• pp.226-238
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• 2006

The electroplating of the Ag ions from aqueous solution on activated porous carbons was investigated over a wide range of plating time. The adsorption capacities of Ag metallic carbons were associated with their internal porosity and were related to physical properties such as surface area and pore size distribution. And, surface morphologies and quantitative analysis for the metal supported carbons are investigated by scanning electron microscopy (SEM) and energy disperse X-ray (EDX) measurements to explain the changes in adsorption properties. It is considered that the pH is an very important factor at the reason of water pollutant with increasing acidity in industrial field. The results of ICP-AES analysis showed that the residual concentration of Ag ions decreased with an increasing electroplating time. The metallic Ag-activated porous carbons electroplated showed microbicidal effects and strong antibacterial activity against six kinds of strains that were used. Finally, we confirmed that the presence of the electrolytic plated Ag-activated porous carbons is a determining factor in the HCl removal by chemical reaction, clarifying the surface chemical behavior.

• 한국초전도ㆍ저온공학회논문지
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• 제22권3호
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• pp.7-12
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• 2020

Electromechanical properties of REBCO CC tapes are known to be limited by defects (cracks) that form in the brittle REBCO layer. These defects could be inherently acquired during the CC tapes' manufacturing process, such as slitting, and which can be initiated at the CC tapes' edges. If propagated and long enough, they are believed to cause critical current degradation and can substantially decrease the delamination strength of CC tapes. Currently, commercially available CC tapes from various manufacturers utilize different growth techniques for depositing the REBCO layers on the substrates in their CC tapes preparation. Their epitaxial techniques, unfortunately, cannot perfectly avoid the formation of particles, in which sometimes acts as current blocking defects, known as outgrowths. Collective research regarding the composition, size, and formation of these particles for various CC tapes with different deposition techniques are particularly uncommon in a single study. Most importantly, these particles might interact in one way or another to the existing cracks. Therefore, systematic investigation on the interactions between the cracks' development mechanism and particles on the REBCO superconducting layers of practical CC tapes are of great importance, especially in the design of superconducting devices. Here, a proper etching process was employed for the CC tapes to expose and observe the REBCO layers, clearly. The scanning electron microscope, field emission scanning microscope, and energy-dispersive x-ray spectroscopy were utilized to observe the interactions between cracks and particles in various practical CC tapes. Particle compositions were identified whether as non-superconducting or superconducting and in what manner it interacts with the cracks were studied.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.277-277
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• 2011

Mo-Cu 합금은 고강도이고 우수한 열전도성 및 전기전도성를 가지는 특성이 있어 현재 방열소재, 반도체 부품, 자동차 부품 등 여러 응용분야에서 연구가 활발히 진행되고 있다. 본 연구에서는 서로 고용성이 없는 Mo-Cu 합금을 제조하기 위해서 Mo, Cu 분말을 PBM (Planetary Ball Milling) 방법을 이용하여 제조 하였으며, 제조된 분말은 SPS (Spark Plasma Sintering) 공정을 이용하여 소결체를 제조하였다. Mo-Cu의 조성 변화는 Cu의 함유량을 각각 5at%Cu, 10at%Cu, 20at%Cu로 조절하여 수행하였으며, PBM 의 공정 변수로 회전수(RPM), 볼과 분말의 비율, 분산제의 양, 볼밀 시간, 분위기 변화를 주어 최적조건을 얻기 위한 실험을 진행하였다. PBM 방법을 이용하여 제조한 분말은 PSA (Particle Size Analysis)에 의해 분말의 크기를 측정하고 EDS(Energy Disperse X-ray Spectrometer) 분석에 의해 조성을 확인하였으며, XRD (X-Ray Diffraction) 분석에 의해 Cu peak이 사라지는 조건을 PBM의 최적조건으로 잡고 실험을 진행하였다. 소결체를 고밀도화하기 위해 소결공정을 SPS 방식으로 하였으며 소결체의 경도, 내마모성, 마찰계수 일함수 등을 분석하기 위해 소결체의 크기를 직경 30 mm 및 두께 5 mm로 설계하였고, 소결 공정 변수로 소결온도를 각각 $900^{\circ}C$, $1000^{\circ}C$, $1100^{\circ}C$, 소결압력을 50MPa, 60MPa, 70MPa, 유지시간을 0분, 10분, 20분으로 차이를 주어, 소결체의 밀도차이와 물성차이를 분석하였다. 그 결과 PBM의 최적조건으로는 5at%Cu 에서는 10h, 10at%Cu, 20at%Cu 에서는 20h의 최적의 밀링 시간을 확인하였고, 다른 공정 변수의 최적조건으로는 회전수 300RPM, 10:1의 볼과 분말 비, 분산제 4wt%, Ar 분위기라는 조건을 얻을 수 있었다. 각각의 공정변수 변화에 따른 소결체 최적밀도 달성조건, 소결체 물성 및 전기적 특성 등의 상관관계에 관하여 보고한다.

• 동력기계공학회지
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• 제17권5호
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• pp.78-85
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• 2013

A high thermal conductivity material, namely graphene is treated by planetary ball milling machine to transport the heat by increasing the temperature. Experiments were performed to assess the heat transfer enhancement benefits of coating the bottom wall of copper substrate with graphene. It is well known that the graphene is unable to disperse into base fluid without any treatment, which is due to the several reasons such as attachment of hydrophobic surface, agglomeration and impurity. To further improve the dispersibility and thermal characteristics, planetary ball milling approach is used to grind the raw samples at optimized condition. The results are examined by transmission electron microscopy, x-ray diffraction, Raman spectrometer, UV-spectrometer, thermal conductivity and thermal imager. Thermal conductivity measurements of structures are taken to support the explanation of heat transfer properties of different samples. As a result, it is found that the planetary ball milling approach is effective for improvement of both the dispersion and heat carriers of carbon based material. Indeed, the heat transfer of the ground graphene coated substrate was higher than that of the copper substrate with raw graphene.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1968-1972
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• 2010

Pt-Co alloy nanowire array was directly synthesized by electrochemical deposition with polycarbonate template at -1.0V and subsequent chemical etching of the template. The use of Pt-Co alloy nanowire array-modified electrode (Pt-Co NAE) for the determination of morphine (MO) is described. The morphology of the Pt-Co alloy nanowire array has been investigated by scanning electron microscopy (SEM) and energy disperse X-ray spectroscopy (EDS) analysis), respectively. The resulting Pt-Co NAE offered a linear amperometric response for morphine ranging from $2.35\times10^{-5}$ to $2.39\times10^{-3}$ M with a detection limit of $7.83\times10^{-6}$ M at optimum conditions. This sensor displayed high sensitivity and long-term stability.