• International Journal of Concrete Structures and Materials
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• v.9 no.1
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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.

• Journal of Surface Science and Engineering
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• v.48 no.5
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• pp.199-204
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• 2015

Recently, fuel cell is a good alternative for energy source. Separator is a important component for fuel cell. In this study, The surface of separator was modified for corrosion resistance and electric conductivity. Reduced graphene oxide (rGO) was made by Staudenmaier's method. Nickel, phosphorus and rGO were coated on 6061 aluminum alloy as a separator of proton exchange membrane fuel cell by composite electroless plating. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were used to examine the morphology of Ni-P-rGO. Surface images were shown that the rGO was dispersed on the surface of Ni-P electroless plating, and nickel was combined with the un-reduced oxygen functional group of rGO.

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.674-682
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• 2010

Fe-fullerene/$TiO_2$ composite photocatalysts were prepared with titanium (IV) n-butoxide (TNB) by a sol-gel method. The samples were characterized by scanning electron microscopy (SEM), Transmission electron microscope (TEM), specific surface area (BET), X-ray diffraction analysis (XRD) and energy dispersive X-ray spectroscopy (EDX). The photocatalytic activities were evaluated by the photocatalytic degradation of methylene blue (MB) solution. XRD patterns of the composites showed that the Fe-fullerene/$TiO_2$ composite contained a typical single and clear anatase phase. The surface properties shown by SEM present a characterization of the texture on Fe-fullerene/$TiO_2$ composites and showed a homogenous composition in the particles for the titanium sources used. The EDX spectra for the elemental identification showed the presence of C and Ti with strong Fe peaks for the Fe-fullerene/$TiO_2$ composite. From the photocatalytic results, the excellent activity of the Fe-fullerene/$TiO_2$ composites for degradation of methylene blue under UV light irradiation could be attributed to both the effects between photocatalytic reaction of the supported $TiO_2$, decomposition of the organometallic reaction by the Fe compound and energy transfer effects such as electron and light of the fullerene.

• Advances in materials Research
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• v.2 no.2
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• pp.119-131
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• 2013

Impedance and electrical conduction studies of $Ba(Nd_{1/2}Nb_{1/2})O_3$ ceramic prepared using conventional high temperature solid-state reaction technique are presented. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single-phase cubic structure with space group $Pm\bar{3}m$. Energy dispersive X-ray analysis and scanning electron microscopy studies were carried to study the quality and purity of compound. The circuit model fittings were carried out using the impedance data to find the correlation between the response of real system and idealized model electrical circuit. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type and negative temperature coefficient of resistance character. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in $Ba(Nd_{1/2}Nb_{1/2})O_3$. The ac conductivity data were used to evaluate the density of states at Fermi level, minimum hopping length and apparent activation energy.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.101-102
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• 2022

A new hydrazone derivatives namely (E)-N'-(4-(dimethylamino)benzylidene)-2-(5-methoxy-2-methyl-1H-indol-3-yl)acetohydrazide (HIND) has been confirmed for mitigating the corrosion of the steel rebar exposed to chloride contaminated synthetic concrete pore solution (ClSCPS). The mitigation of corrosion properties has been characterized by weight loss and electrochemical methods (Electrochemical impedance, Potentiodynamic polarization studies) as well as surface observations. The presence of HIND in the ClSCPS decreased the corrosion of steel rebar by adsorption of HIND molecules on the surface of the steel rebar. The optimal HIND concentration was 0.5 mmol/L, corresponding to an inhibition efficiency of 88.4%. The use of HIND enables the corrosion process to have a higher energy barrier. X-ray photo electron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) spectroscopy interpretations confirmed that HIND mitigates the corrosion attack on the surface steel rebar.

• Journal of Ceramic Processing Research
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• v.21 no.4
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• pp.479-487
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• 2020

Ceramic ZnS nanocomposites were prepared by mechanical processing and one-step heat sintering with powder mixtures of fly ash, waste glass, and ZnS (template-free hydrothermal method manufacturing). Chemical durability and morphological characteristics of heat-treated samples at 800 ℃ with/without acid treatment were evaluated. The photocatalytic activities were estimated with methyl orange (MO), methylene blue (MB), acetaldehyde (ATA), and 2,4-dichlorophenoxyacetic acid (2,4-D) as photodegradation targets. Crystallization behaviors of the prepared ceramic ZnS nanocomposites were investigated using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectrometry (EDS). In addition, compressive and bending strength as mechanical properties were evaluated. Ceramic ZnS nanocomposites were found to showed improvement in optimal photocatalytic reaction and physical properties regardless of acid treatment when the amount of ZnS nanoparticles was increased from 7.0 to 25.0 wt%. Degrees of photocatalytic decomposition of MO, ATA, 2,4-D, and MB by acid treated ceramic ZnS nanocomposites containing 25 wt% ZnS were about 0.185, 0.121, 0.216, 0.236, respectively, after UV irradiation for 180 min.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1182-1190
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• 2014

$Cd_{1-x}Zn_xS$-sensitized $K_4Nb_6O_{17}$ composite photocatalysts (designated $Cd_{1-x}Zn_xS/K_4Nb_6O_{17}$) were prepared via a simple deposition-precipitation method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), $N_2$ sorption, ultraviolet-visible light diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence measurements (PL), and X-ray photoelectron spectroscopy (XPS). The $Cd_{0.8}Zn_{0.2}S$ particles were scattered on the surface of $K_4Nb_6O_{17}$, and had a relatively uniform size distribution around 50 nm. The absorption edge of $K_4Nb_6O_{17}$ was shifted to the visible light region and the recombination of photo-generated electrons and holes suppressed after $Cd_{0.8}Zn_{0.2}S$ loading. The $Cd_{0.8}Zn_{0.2}S$(25 wt %)/$K_4Nb_6O_{17}$ composite possessed the highest photocatalytic activity for hydrogen production under visible light irradiation, evolving 8.278 mmol/g in 3 h. Recyclability tests were performed, and the composite photocatalysts were found to be fairly stable. The mechanism of charge separation between the photogenerated electrons and holes at the $Cd_{0.8}Zn_{0.2}S/K_4Nb_6O_{17}$ composite was discussed.

• Mass Spectrometry Letters
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• v.4 no.3
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• pp.51-54
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• 2013

Isotopic analysis using thermal ionization mass spectrometry coupled with scanning electron microscopy (SEM-TIMS) was performed to determine the isotopic ratios of uranium contained in micro-particles in the 6th Nuclear Signatures Interlaboratory Measurement Evaluation Programme (NUSIMEP-6) sample. Elemental analysis by energy dispersive X-ray spectroscopy (EDS) was conducted on uranium-bearing mirco-particles, which were transferred to rhenium filaments for TIMS loading using a micromanipulation system in a SEM. A multi-ion-counter system was utilized to detect the ion signals of the four isotopes of uranium simultaneously. The isotope ratios of uranium corrected by bracketing using a reference material showed excellent agreement with the certified values. The measurement accuracy for $n(^{234}U)/n(^{238}U)$ and (b) $n(^{235}U)/n(^{238}U)$ was 10% and 1%, respectively, which met the requirements for qalification for the NetWork of Analytical Laboratories (NWAL).

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.159-164
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• 1997

Pyrolytic carbon layer was coated on A1203 balls by fluidized bed type chemical vapour deposition unit to develop the coating technology for the preparation of coated nuclear fuel. The deposition was carried out at the temperature ranges between 110$0^{\circ}C$ and 130$0^{\circ}C$ with various gas contents and flow rates. Source and carrier gas were propane and argon, respectively. X-ray analysis shows that the deposition layer was typical carbon spectra. The growth rate of carbon layer depended on the amount of source gas and the deposition temperature. For the alumina balls with 2mm in diameter, the deposition rate was 11${\mu}{\textrm}{m}$/hr in the flow gases containing 30% source gas at 130$0^{\circ}C$ with a total flow rate of 2.0$\ell$/min. Microstructural observation of the deposits with scanning electron microscope revealed that the deposits had relatively dense and isotropic structure. Chemical analysis by energy dispersive spectroscopy showed that the layer was pure carbon.

• Corrosion Science and Technology
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• v.16 no.1
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• pp.8-14
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• 2017

The corrosion behavior of a ferritic/martensitic steel T91 exposed to an aqueous solution containing chloride and sulfate ions is investigated depending on the stimulated all-volatile treatment (AVT) and under oxygenated treatment (OT) conditions. The corrosion of T91 steel under OT condition is severe, while the corrosion under AVT condition is not. The co-existence of chloride and sulfate ions has antagonistic effect on the corrosion of T91 steel in both AVT and OT conditions. Unlike to corrosion resistance in the aqueous solution, OT pretreatment provides T91 steel lower oxidation-resistance than VAT pretreatment. From scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) analysis, the lower corrosion resistance in the aqueous solution by VAT conditions possibly is due to the formation of pits. In addition, the lower oxidation resistance of T91 steel pretreated by OT conditions is explained as follows: the cracks formed during the immersion under OT conditions accelerated peeling-off rate of the oxide film.