• 한국광물학회지
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• 제29권4호
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• pp.191-198
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• 2016

인회석 광물 군에 속하는 녹연석($Pb_{4.85}(P_{1.02}O_4)_3Cl_{1.04}$)에 대한 상온-고압 상태방정식 연구를 시행하였다. 대칭형 다이아몬드 앤빌기기를 이용하여 33.4 GPa까지 압력을 증가시키면서 각분산 X-선 회절법과 방사광을 이용하여 회절 데이터를 검출하였으며, 시료에 가해준 압력은 루비 형광파의 파장변화를 측정하여 결정하였다. 본 고압실험에서 시행한 압력의 범위 내에서 상변이는 관찰되지 않았으며, 정압상태에서 체적탄성률($K_0$)은 $K{_0}^{\prime}=13(2)$일 때 80(7) GPa로 계산되었다. 본 연구에서 결정된 상온상태에서 녹연석의 체적탄성률 신뢰도를 정규화압력 및 정규화응력변형 분석을 하여 평가하였다.

• 한국재료학회지
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• 제27권3호
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• pp.172-178
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• 2017

The aim of this study is to consider the effect hydrogen on dezincification behavior of Cu-Zn alloys. The investigations include microstructural observations with scanning electron microscope and chemical composition analysis with energy dispersive spectrometer. The dezincification layer was found to occur in high pressure hydrogen atmosphere, not in air atmosphere. In addition, the layers penetrated into the inner side along the grain boundaries in the case of hydrogen condition. The shape of the dezincification layers was porous because of Zn dissolution from the ${\alpha}$ or ${\beta}$ phase. In the case of stress corrosion cracks formed in the Cu-Zn microstructure, the dezincification phenomenon with porous voids was also accompanied by grain boundary cracking.

• 상하수도학회지
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• 제27권2호
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• pp.155-164
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• 2013

The main purpose of this research was to examine the adsorption/ion exchange characteristics of radioactive species such as cesium and strontium onto synthetic Na-birnessite (sodium-birnessite). As part of efforts to investigate the sorption behavior of cesium and strontium onto synthetic Na-birnessite, batch isotherm tests were performed under different experimental conditions. Na-birnessite was synthesized by the oxidation of $Mn^{2+}$ ions in sodium hydroxide solution. The synthetic Na-birnessite was characterized by powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) surface area analysis. Cesium and strontium concentrations were determined by atomic absorption spectroscopy (AAS). The removal efficiency of strontium by Na-birnessite was around 95 % which was much higher than that of cesium (~ 32 %). The results imply that strontium has a higher affinity for Na-birnessite than cesium because strontium, divalent cation leads to larger electrostatic attraction than monovalent cesium.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1230-1236
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• 2016

This study aims to determine the effect of fly ash with a high replacing ratio of clay on the radiation shielding properties of bricks. Some interaction parameters (mass attenuation coefficients, half value layer, effective atomic number, effective electron density, and absorption efficiency) of clay fly ash bricks were measured with a NaI(Tl) detector at 661.6 keV, 1,173.2 keV, and 1,332.5 keV. For the investigation of their shielding behavior, fly ash bricks were molded using an admixture to clay. A narrow beam transmission geometry condition was used for the measurements. The measured values of these parameters were found in good agreement with the theoretical calculations. The elemental compositions of the clay fly ash bricks were analyzed by using an energy dispersive X-ray fluorescence spectrometer. At selected energies the values of the effective atomic numbers and effective electron densities showed a very modest variation with the composition of the fly ash. This seems to be due to the similarity of their elemental compositions. The obtained results were also compared with concrete, in order to study the effect of fly ash content on the radiation shielding properties of clay fly ash bricks. The clay fly ash bricks showed good shielding properties for moderate energy gamma rays. Therefore, these bricks are feasible and eco-friendly compared with traditional clay bricks used for construction.

• KCI Concrete Journal
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• 제11권3호
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• pp.127-140
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• 1999

In this paper, a microscopic analysis of prefinitelv strained cement paste specimen was carried out. The microscopic behavior of concrete under triaxial stress must be fully understood in order to explain the additional ductilitv that comes from lateral confinement and to get microstructural information in large deformed and large strained concrete. The so-called "tube-squash" test was applied to achieve enormously high shear and deviatoric strain of concrete under extremly high pressure without fracture. Then, microscopic analyses by focusing on hydration and microstructure of Prefinitely strained cement paste were carried out on cored-out deformed and virgin (undeformed) cement paste specimens : the first specimen being 40 days old, the second one being one year old. The microscopic analysis bv Field Emission Scanning Electronic Microscope (FESEM) was carried out for comparison between the specimens after 40 days and those arter one year. For one year old specimens, X-Ray Diffractometer (XRD) analysis, Energy Dispersive x-rav Spectrometer (EDS) analysis, and Differential Thermal Analysis/Thermo-Gravitv (DTA/TG) analysis were also carried out to study the hydration and the microstructures of prefinitely strained cement paste specimen by focusing on the methodologies of their microscopic analyses. analyses.

• Journal of Electrochemical Science and Technology
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• 제9권1호
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• pp.69-77
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• 2018

Aluminum electrodeposition was carried out in dimethylsulfone ($DMSO_2$) baths containing 6.2-28.3 mol% $AlCl_3$ at 403 K. The electrochemically active species for Al electrodeposition in $DMSO_2$ baths were investigated. Electrochemical behavior of the electrolyte and the deposition mechanism were studied via cyclic voltammetry (CV). Properties of the deposits were assessed by scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction. In addition, structures of the ionic complexes formed with aluminum in the bath were characterized by $^{27}Al$ nuclear magnetic resonance (NMR) spectroscopy. NMR spectra revealed that all baths contained two ionic species: $AlCl_4{^-}$ and $[Al(DMSO_2)_3]^{3+}$. Al electrodeposited when the $[Al(DMSO_2)_3]^{3+}$ concentration was the highest (23.3 mol% $AlCl_3$) exhibited fine grain sizes, relatively smooth surfaces, and high purities.

• Geomechanics and Engineering
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• 제21권4호
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• pp.337-348
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• 2020

Tropical organic soils having more than 65% of organic matters are named "peat". This soil type is extremely soft, unconsolidated, and possesses low shear strength and stiffness. Different conventional and industrial binders (e.g., lime or Portland cement) are used widely for stabilisation of organic soils. However, due to many factors affecting the behaviour of these soils (e.g., high moisture content, fewer mineral particles, and acidic media), the efficiency of the conventional binders is low and/or cost-intensive. This research investigates the impact of different constituents of cement-sodium silicate grout system on the compressibility behaviour of organic soil, including settlement and void ratio. A microstructure analysis is also carried out on treated organic soil using Scanning Electron Micrographs (SEM), Energy Dispersive X-ray spectrometer (EDX), and X-ray Diffraction (XRD). The results indicate that the settlement and void ratio of treated organic soils decrease gradually with the increase of cement and kaolinite contents, as well as sodium silicate until an optimum value of 2.5% of the wet soil weight. The microstructure analysis also demonstrates that with the increase of cement, kaolinite and sodium silicate, the void ratio and porosity of treated soil particles decrease, leading to an increase in the soil density by the hydration, pozzolanic, and polymerisation processes. This research contributes an extra useful knowledge to the stabilisation of organic soils and upgrading such problematic soils closer to the non-problematic soils for geotechnical applications such as deep mixing.

• 한국표면공학회지
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• 제54권6호
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• pp.315-323
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• 2021

In general, surface treatments of electroless Ni-P coating are extensively applied in the industry due to their excellent properties for considerable wear resistance, hardness, corrosion resistance. This study aims to determine the effect of ultrasonic conditions on the morphology, alumina content, roughness, hardness, and corrosion resistance of electroless Ni-P-Al₂O₃ composite coatings. The characteristics were analyzed by Energy-dispersive X-ray spectroscopy (EDX), x-ray diffractions (XRD), and atomic force microscopy (AFM), etc. In this study, the effect of ultrasonic condition uniformly distributed alumina within Ni-P solution resulting in a smoother surface, lower surface roughness. Furthermore, the corrosion resistance behavior of the coating was analyzed using tafel polarization curves in a 3.5 wt.% NaCl solution at 25 ℃. Under ultrasonic, Al₂O₃ content in Ni-P composite solution increased from 0.5 to 5.0 g/L, Al₂O₃ content at 3.0 g/L was showed a significantly enhanced corrosion resistance. These results suggested that ultrasonic condition was an effective method to improve the properties of the composite coating.

• International Journal of Oral Biology
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• 제44권3호
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• pp.108-114
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• 2019

In the present study, rutile phase titanium dioxide nanoparticles ($R-TiO_2$ NPs) were prepared by hydrolysis of titanium tetrachloride in an aqueous solution followed by calcination at $900^{\circ}C$. The composition of $R-TiO_2$ NPs was determined by the analysis of X-ray diffraction data, and the characteristic features of $R-TiO_2$ NPs such as the surface functional group, particle size, shape, surface topography, and morphological behavior were analyzed by Fourier-transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, transmission electron microscopy, dynamic light scattering, and zeta potential measurements. The average size of the prepared $R-TiO_2$ NPs was 76 nm, the surface area was $19m^2/g$, zeta potential was -20.8 mV, and average hydrodynamic diameter in dimethyl sulfoxide (DMSO)-$H_2O$ solution was 550 nm. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and morphological observations revealed that $R-TiO_2$ NPs were cytocompatible with oral cancer cells, with no inhibition of cell growth and proliferation. This suggests the efficacy of $R-TiO_2$ NPs for the aesthetic white pigmentation of teeth.

• Journal of Electrochemical Science and Technology
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• 제10권3호
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• pp.257-270
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• 2019

The inhibition performance of sodium gluconate (SG), cetyltrimethylammonium bromide (CTAB) and their mixture (SG/CTAB) on the corrosion behavior of ${\alpha}$-brass in 0.5 M $H_2SO_4$ solution has been investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Scanning Electron Microscope with Energy-Dispersive Spectrometer (SEM-EDS), Inductively Coupled Plasma Spectrometry (ICPS) and molecular dynamics (MD) simulation techniques. The results reveal that SG with 5ppm CTAB, noted SG/CTAB, acts as a good corrosion inhibitor and its inhibition efficiency reached 89% after 24 h immersion in sulfuric acid solution, but slightly decreased at higher temperatures. The polarization curves displayed that SG/CTAB acts as a cathodic-kind inhibitor. Electrochemical impedance spectroscopy (EIS) studies revealed that the addition of 5ppm CTAB to different concentrations of SG considerably increases the corrosion resistance of ${\alpha}$-brass. The SEM-EDS and ICPS analyses support the experimental results. Further, molecular dynamics (MD) simulations were used to understand the adsorption profiles of SG/CTAB on Cu(111) and Zn(111) surfaces.