• 한국표면공학회지
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• 제43권1호
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• pp.25-30
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• 2010

Titanium and titanium alloys are widely used for orthopedic and dental implants for their superior mechanical properties, low modulus, excellent corrosion resistance and good biocompatibility. In this study, corrosion behaviors of nanotube formed on the bone plate of Ti-6Al-4V alloy for dental use have been investigated. $TiO_2$ nanotubes were formed on the dental bone plates by anodization in $H_3PO_4$ containing 0.6 wt % NaF solution at $25^{\circ}C$. Electrochemical experiments were performed using a conventional three-electrode configuration with a platinum counter electrode and a saturated calomel reference electrode. Anodization was carried out using a scanning potentiostat (EG&G Co, Model 263A USA), and all experiments were conducted at room temperature. The surface morphology was observed using field emission scanning electron microscopy (FE-SEM) and energy dispersive x-ray spectroscopy(EDS). The corrosion behavior of the dental bone plates was examined using potentiodynamic test(potential range of -1500~2000 mV) in a 0.9% NaCl solution by potentiostat (EG&G Co, PARSTAT 2273. USA). The inner diameter of nanotube was about 150~180 nm with wall thickness of about 20 nm. The interspace of nanotube to nanotube was 50 nm. The passive region of the nanotube formed bone plates showed the broad range compared to non-nanotube formed bone plates. The corrosion surface of sample was covered with corrosion products.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.164-171
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• 2021

The europium sorption on Tamusu clay was investigated by batch sorption experiments and spectroscopic study under the condition of strong ionic strength. The results demonstrated that europium sorption on Tamusu clay increased rapidly with pH value, but decreased with the ionic strength of solution increased. The europium sorption also increased in the presence of humic acid, especially at low pH value. The sorption could be fitted by Freundlich isotherm model and the europium sorption on clay was spontaneous and endothermic reaction. Besides, the result indicates that ion exchange was the main process at low pH value, while inner-sphere surface complexation dominated the sorption process at high pH value. The Backscatter electron scanning/Energy Dispersive Spectrometer(BSE/EDS) and the effect of Na for europium sorption results further suggested that europium sorption on Tamusu clay mainly competed with Na at low pH value. Overall, the results in this research were of significance to understand the sorption behavior of europium on the geological media under high ionic strength.

• 한국해안·해양공학회논문집
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• 제25권5호
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• pp.285-290
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• 2013

선형과 천해 edge wave로 구분되는 이들의 거동을 더 잘 이해하기 위해 비교하였다. 본 연구에서는 변수분리법을 사용하여, Ursell (1952)이 해의 유도과정 없이 제시한, 선형 edge wave의 해를 얻었다. 천해 edge wave는 비록 천해방정식으로부터 유도되지만 분산특성을 갖는다. 완만한 해저경사의 경우, 천해 파형은 선형 파형과 거의 같게 되고 천해 파형은 다루기가 쉬운 장점이 있다. Gaussian 분포형태의 이동체에 의해 생성되는 edge wave를 계산하기 위해 천해 고유파형으로 전개한 해를 구성하였고, 이에 대한 결과를 제시하고 특성을 기술하였다.

• 공업화학
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• 제27권4호
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• pp.421-426
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• 2016

본 연구에서는 폴리옥소메탈레이트(polyoxometalate, POM)가 도핑된 폴리피롤(polypyrrole, Ppy)을 3차원 구조의 탄소천(carbon cloth, CC) 표면 위에 전기화학적 증착법을 이용하여 합성하고 이의 의사커패시터 특성을 순환전압전류법과 정전류 충전-방전법을 사용하여 분석하였다. POM-Ppy의 코팅은 전기화학적 증착 시간에 따라서 얇은 conformal형태의 코팅으로 조절되었다. 제조된 POM-Ppy/CC의 재료 특성은 전자주사현미경과 X-선 분광분석을 사용하여 분석하였다. POM-Ppy/CC의 3차원 나노복합체 구조는 높은 비정전용량($561mF/cm^2$), 고속 충방전(85% 용량 유지율) 및 장수명 특성(97% 용량 유지율)을 나타내었다.

• 열처리공학회지
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• 제21권5호
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• pp.235-243
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• 2008

Ni-C composite films were prepared using a combination of microwave plasma CVD and ion beam sputtering deposition working in a codeposition way. The structure of these films was characterized by energy-dispersive X-ray diffraction (EDXRD), transmission electron microscopy (TEM) and Raman spectroscopy. It was found that a nickel carbide phase, $Ni_3C$ (hcp), formed as very fine crystallites over a wide temperature range when Ni-C films were deposited at low $CH_4$ flow rates. The thermal stability of this nonequilibrium carbide $Ni_3C$ was also studied. As a result, the $Ni_3C$ carbide was found to decompose into nickel and graphite at around $400^{\circ}C$. With high $CH_4$ flow rates (> 0.2 sccm), the structure of the Ni-C films became amorphous. The formation behavior of the carbide and amorphous Ni-C phases are discussed in relation to the electrical resistivity of the films.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1244_1245
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• 2009

Coating of amorphous nitride thin layers, such as boron nitride (BN) and carbon nitride (CN), has been performed on carbon nanotubes (CNTs) for the purpose of enhancing their electron-emission performances because those nitride films have relatively low work functions and commonly exhibit negative electron affinity behavior. The CNTs were directly grown on metal-tip (tungsten, approximately 500 nm in diameter at the summit part) substrates by inductively coupled plasma-chemical vapor deposition (ICP-CVD). Sharpening of the tungsten tips were carried out by electrochemical etching. Morphologies and microstructures of BN and CN films were analyzed by field-emission scanning electron microscopy (FE-SEM), energy dispersive x-ray (EDX) spectroscopy, and Raman spectroscopy. The electron-emission properties (such as maximum emission currents and turn-on fields) of the BN-coated and CN-coated CNT-emitters were characterized in terms of the thickness of BN and CN layers.

• Computers and Concrete
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• 제17권4호
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• pp.553-566
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• 2016

Fracture energy is one of the key parameters reveal cracking resistance and fracture toughness of concrete. The main purpose of this study is to determine fracture behavior, mechanical properties and microstructural analysis of high strength basalt fiber reinforced concrete (HSFRC). For this purpose, three-point bending tests were performed on notched beams produced using HSFRCs with 12 mm and 24mm fiber length and 1, 2 and $3kg/m^3$ fiber content in order to determine the value of fracture energy. Fracture energies of the notched beam specimens were calculated by analyzing load versus crack mouth opining displacement curves by the help of RILEM proposal. The results show that the effects of basalt fiber content and fiber length on fracture energy are very significant. The splitting tensile and flexural strength of HSFRC increased with increasing fiber content whereas a slight drop in flexural strength was observed for the mixture with 24mm fiber length and $3kg/m^3$ fiber content. On the other hand, there was no significant effect of fiber addition on the compressive strength and modulus of elasticity of the mixtures. In addition, microstructural analysis of the three components; cement paste, aggregate and basalt fiber were performed based on the Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy examinations.

• 한국수소및신에너지학회논문집
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• 제19권6호
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• pp.482-489
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• 2008

Ti-Cr alloys consist of BCC solid solution, C36, C14 and C15 Laves phase at high temperature. Among others, the BCC solid solution phase was reported to have a high hydrogen storage capacity. However, activation, wide range of hysteresis at hydrogenation/dehydrogenation, and degradation of hydrogen capacity due to hydriding/dehydriding cycles must be improved for its application. In this study, to improve such problems, we added a Nb. For attaining target materials, Ti-10Cr-xNb(x=1, 3, 5wt.%) specimens were prepared by arc melting. The arc melting process was carried out under argon atmosphere. As-received specimens were characterized using XRD(X-ray diffraction), SEM(Scanning Electron Microscopy) with EDX(Energy Dispersive X-ray) and TG/DSC(Thermo Gravimetric Analysis/Differential Scanning Calorimetry). In order to examine hydrogenation behavior, the PCI(pressure-Composition-Isotherm) was performed at 293, 323, 373 and 423K.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권1호
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• pp.72-77
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• 2017

Purpose: The electrochemical corrosion behavior of tin oxide film coated on PET substrates has been studied under varying concentrations of acrylic acid to investigate possible corrosion in contact with the acidic environment. Method: Potentiodynamic test was performed for a commercial ITO/PET film in 0.1, 0.3, and 0.5 M of acrylic acid. The surface morphology was analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Results: Potentiodynamic test results showed an increase in Icorr and decrease in Ecorr value with increasing concentration of acid. Microscopic evaluation suggested the presence of certain deep cracks on the surface of the film in addition with a severe acidic attack. Conclusion: Exposure of ITO to acrylic acid resulted in the stress corrosion cracking of ITO film due to the mechanical mismatch between brittle inorganic ITO fim and a compliant organic PET substrate leading to the subsequent failure of the film.

• International Journal of Concrete Structures and Materials
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• 제9권1호
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• pp.35-43
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• 2015

The critical element for sustainable growth in the construction industry is the development of alternative cements. A new technological process called geopolymerization provides an innovative solution, and the presence of aluminum and silicon oxides in fly ash has encouraged its use as a source material. Many previous investigations have involved curing the binder in a heated environment. To reduce energy consumption during the synthesis of geopolymers, the present study investigated the properties of ambient cured geopolymer mortar at early ages. An experimental program was executed to establish a relationship between the activator composition and the properties of geopolymer mortar in fresh and hardened states. Concentrations of sodium hydroxide and sodium silicate were ascertained that are advantageous for constructability and mechanical behavior. Scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction techniques were also used to characterize the material. Test results indicate that there is potential for the concrete industry to use fly ash based geopolymer as an alternative to portland cement.