• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.590-592
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• 2010

Li-Mn spinel ($LiMn_2O_4$) is prepared by a hydrothermal process with K-Birnessite ($KMnO_4{\cdot}yH_2O$) as a precursor. The K-Birnessite obtained via a hydrothermal process with potassium permanganate [$KMnO_4$] and urea [$CO(NH_2)_2$] as starting materials are converted to Li-Mn spinel nanoparticles reacting with LiOH. The molar ratio of LiOH/K-Birnessite is adjusted in order to find the effect of the ratio on the structural, morphological and electrochemical performances of the Li-Mn spinel. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetry (TG) are used to investigate the crystal structure and morphology of the samples. Galvanostatic charge and discharge are carried out to measure the capacity and rate capability of the Li-Mn spinel. The capacity shows a maximum value of $117\;mAhg^{-1}$ when the molar ratio of LiOH/K-Birnessite is 0.8 and decreases with the increase of the ratio. However the rate capability is improved with the increase of the ratio due to the reduction of the particle size.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.53-56
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• 2009

At room-temperature, a facile, seedless, and environmentally benign green route for the synthesis of star like PbS nanoclusters at 7 min in aqueous solution of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM] [$EtSO_{4}$], room-temperature ionic liquid (RTIL), via ultrasonic irradiation is proposed. The X-ray diffraction studies display that the products are excellently crystallized in the form of cubic structure. An energy dispersive X-ray spectroscopy (EDX) investigation reveals the products are extremely pure. The absorption spectra of the product exhibit band gap energy of about 4.27 eV which shows an enormous blue shift of 3.86 eV that can be attributed to very small size of PbS nanoparticles produced and quantum confinement effect. A possible formation mechanism of the PbS nanoparticles using ultrasonic irradiation in aqueous solution of the RTIL is presented.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.160-160
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• 2013

본 실험에서는 CIGS 흡수층을 스퍼터링 방식과 급속열처리 장비를 이용한 2-step 방식을 이용하여 형성시켰다. 전구체는 DC 스퍼터링 방법으로 $Cu_{0.75}Ga_{0.25}/In$의 다층 전구체를 구성 후, 독성이 없는 셀레늄 팰릿을 graphite 상자에 넣어 급속열처리 장비로 온도를 $475{\sim}680^{\circ}C$로 온도를 조절하면서 셀렌화 하였다. 이렇게 구성된 CIGS 흡수층의 특성을 scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray differection (XRD)를 통해서 측정을 하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.139-140
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• 2015

Zn/HA coating on the Ti-xNb alloys after nanotube formation for dental lmplant was researched using various experimental methods. Due to g ood biocompatibility and osteoconductivity, hydroxyapatite (HA) coating s on metallic biomedical implants were widely employed in orthopedic and dental applications. To improve biocompatibilities, Zinc (Zn) plays very important roles in the bone formation and immune reg ulations. The nanotube formed Zn-HA films were characterized with X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS).

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.537-541
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• 2010

Pt-Sn with various ratios was supported on carbon black after pretreatment in an acidic solution by a reduction method. The Pt/Sn ratio was controlled by varying the concentration of each component in the solution, and the influence of the composition on the electrocatalytic activities was investigated. The crystallinity of the synthesized materials was investigated by XRD (X-ray Diffraction), and the oxidation states of both the platinum and tin were determined by XPS (X-ray Photoelectron Spectroscopy). SEM (Scanning Electron Microscopy)-EDS (Energy Dispersive Spectroscopy) was utilized to examine the morphology and composition of the synthesized electrode, and the particle size of the Pt-Sn was analyzed by TEM (Transmission Electron Microscopy). The electrocatalytic activity for oxygen reduction was evaluated in a 0.5 M $H_2SO_4$ solution using a rotating disk electrode system. The activity and stability were found to be strongly dependent on the electrode composition (Pt/Sn ratio). The catalytic activity and stability for methanol oxidation were also measured using cyclic voltammetry (CV) in a mixture of 0.5 M $H_2SO_4$ and 0.5 M $CH_3OH$ aqueous solution. The addition of proper amount of Sn was found to significantly improve both catalytic activity and stability for methanol oxidation.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.272.2-272.2
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• 2016

Copper-Tin (CuSn) thin films were synthsized by rf magnetron co-sputtering method with pure Cu and Sn metal targets with various rf powers and sputtering times. The obtained CuSn thin films were characterized by a surface profiler (alpha step), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES), and contact angle measurement. The deposition rates were calculated by the thickness of CuSn thin films and sputtering times. We observed hexagonal Cu20Sn6 and cubic Cu39Sn11 phases from the films by XRD measurement. From the survey XPS spectra, the Cu and Sn main peaks were observed. Therefore, we could conclude CuSn thin films were successfully fabricated on the substrate in this study. The changes of oxidation states and chemical environment of the films were investigated with high resolution XPS spectra in the regions of Cu 2p, Cu LMM, and Sn 3d. Surface free energy (SFE) and wettability of the CuSn thin films were studied with distilled water (DW) and ethylene glycol (EG) using the contact angle measurement. The total SFE of CuSn thin films decreased as rf power on Cu target increased. The contribution to the total SFE of dispersive SFE was relatively superior to polar SFE.

• Nuclear Engineering and Technology
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• v.40 no.2
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• pp.147-154
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• 2008

The general corrosion behavior of austenitic and ferritic steels(316L, 304, N controlled 304L, and 410) in supercritical water is investigated in this paper. After exposure to deaerated supercritical water at $480^{\circ}C$/25 MPa for up to 500 h, the four steels studied were characterized using gravimetry, scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS), X-ray photoelectron spectroscopy(XPS), and X-ray diffraction(XRD). The results show that the 316L steel with a higher Cr and Ni content has the best corrosion-resistance performance among the steels tested. In addition to the oxide layer mixed with $Fe_{3}O_{4}$ and $(Fe,Cr)_{3}O_{4}$ that formed on all the samples, a $Fe_{3}O_{4}$ loose outer layer was observed on the 410 steel. The corrosion mechanism of stainless steels in supercritical water is discussed based on the above results.

• Journal of the Korean Electrochemical Society
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• v.18 no.2
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• pp.68-74
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• 2015

To compare the microstructure and electrochemical properties between two binary alloys (Cr-Si, Ni-Si), two composition of binary alloys with the same capacity were selected using phase-diagram and prepared by matrix-stabilization method to suppress the volume expansion of Si by inactive-matrix. Master alloys were made by Arc-melting followed by fine structured ribbon sample preparation by Rapid Solidification Process (RSP, Melt-spinning method) under the same conditions. Also powder samples were produced by wet grinding for X-Ray Diffraction (XRD) and electrochemical measurements. As predicted from the phase diagram, only active-Si and inactive-matrix ($CrSi_2$, $NiSi_2$) were detected. The results of Scanning Electron Microscope (SEM) and Transmission Electron Microscopy - Energy Dispersive X-ray Spectroscopy (TEM-EDS) show that Cr-Si alloy has finer microstructure than Ni-Si alloy, which was also predictable through phase diagram. The electrochemical properties related to microstructure were evaluated by coin type full- and half-cells. Separately, self-designed test-cells were used to measure the volume expansion of Si during reaction. Volume expansion of Cr-Si alloy electrode with finer microstructure was suppressed significantly and improved in cycle capability, in comparison Ni-Si alloy with coarse microstructure. From these, we could infer the correlation of microstructure, volume expansion and electrochemical degradation and these properties might be predicted by phase diagram.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.309-314
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• 2010

The surface modified $LiMn_2O_4$ materials with Li-Fe composites were prepared by a sol-gel method to improve the electrochemical performance of $LiMn_2O_4$ and were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and transmission electron microscopy (TEM)-EDS. XRD results indicate that all the samples (modified and pristine samples) have cubic spinel structures, and XRD, XPS, and TEM-EDS data reveal the formation of $Li(Li_xFe_xMn_{2-2x})O_4$ solid solution on the surface of particles. For the electrochemical properties, the modified material demonstrated dramatically enhanced reversibility and stability even at elevated temperature. These improvements are attributed to the formation of the solid solution, and thus-formed solid solution phase on the surface of $LiMn_2O_4$ particle reduces the dissolution of Mn ion and suppresses the Jahn-Teller effect.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.295-295
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• 2010

Nanoparticles of the compound semiconductor, Cu(In, Ga)Se2 (CIGS), were synthesized in solution under ambient pressure below $100^{\circ}C$ and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption spectroscopy and energy-dispersive X-ray (EDX) analyses. These materials have chalcopyrite crystal structures and the particle sizes less than 100 nm. Synthetic conditions were studied for the crystallized CIGS nanoparticles formation to prevent from side products of Cu2Se, Cu2-xSe, and CuSe etc. The single phase CIGS nanoparticles were applied to coating of thin films photovoltaic cells. The electro deposition of CIGS thin films is also a good non-vacuum technology and under investigation. In aqueous solutions, the different chemical compositions of CIGS thin films were obtained, depending on pH, concentration of starting materials and deposition potentials. The surface morphology of the prepared CIGS thin films depends on the complexing ligands to the solutions during the electrochemical deposition.