• Asian Journal of Atmospheric Environment
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• v.11 no.1
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• pp.54-60
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• 2017

Quantifying the trace elements in infinitesimal ambient liquid samples (e.g., single raindrop, cloud/fog water, and the soluble fraction extracted from the particles collected for a short time) is an important task for understanding formation processes, heating/cooling rates, and their health hazards. The purpose of this study is to employ an in-air micro PIXE system for quantitative analysis of the trace elements in a thimbleful of reference liquid sample. The bag type liquid sample holder originally designed with $10{\mu}m$ thick $Mylar^{(R)}$ film retained the original shape without any film perforation and apparent peaks of film blank by the end of the analysis. As one of tasks to be solved, the homogeneity of the elemental distribution in liquid reference species was verified by the X-ray line profiles for several references. It was possible to resolve the significant peaks for whole target elements corresponding to the channel number of micro-PIXE spectrum. The calibration curves for the six target elements (Si, S, Cl, Fe, Ni, and Zn) in standard solutions were successfully plotted by concentration (ppm) and ROI of interest net counts/dose (nC).

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.266-270
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to material characteristics, such as, thermal conductivity and high temperature flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld parameters. FE simulation is performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.

• Journal of the Korean institute of surface engineering
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• v.51 no.3
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• pp.149-156
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• 2018

The corrosion and strength degradation characteristics of 1.25Cr-0.5Mo steels were studied under $650^{\circ}C$ in $76%N_2+6%O_2+16%CO_2+2%SO_2$ gas condition up to 500 hrs. Corroded specimens were characterized by weight gain, scanning electron microscope(SEM), energy dispersive X-ray spectroscopy(EDS), and X-ray diffraction(XRD). The tensile test was conducted to evaluate the mechanical strength and fracture mode with corrosion at high temperature. As the results of the experiments, thick Fe-rich oxide layers over $200{\mu}m$ were formed on the surface within 500 hrs. The thick oxide layers are formed with reduction of the cross-sectional area of the specimens. Thus, the strength tended to decrease with reduction of the cross-sectional area.

• Journal of the Korean institute of surface engineering
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• v.27 no.3
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• pp.158-165
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• 1994

Cu-Cr alloy thin film requires good quality of etching be used for TAB technology. The etched cross sec-tion was clean enough when the etching was performed in 0.1M $FeCl_3$ solution at $50^{\circ}C$. The etching rate was increased with the amount of $KMnO_4$. For enhanced profile of cross section and rate, the spray etchning was found to be superior compared to the immersion etching. A series of experiments were performed to improve the uniformity of the current distribution in electrodeposition onto the substrate with lithographic patterns. Copper was electrodeposited from quiescent-solution, paddle-agitated-solution, and air-bubbled-solution to in-vestigate the effect of the fluid flow. The thickness profile of the specimen measured by profilmetry has the non uniformity at feature scale in quiescent-solution, because of the longitudinal vortex roll caused by the natural convection. However, uniform thickness profile was achieved in paddle-agitated or air bubbled solu-tion.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.2883-2888
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• 2013

To enhance the power conversion efficiency of dye-sensitized solar cell (DSSC), the surface of titanium dioxide ($TiO_2$) photoelectrode was modified by hydroxylation treatment with $NH_4OH$ solution at $70^{\circ}C$ for 6 h. The $NH_4OH$ solutions of various concentrations were used to introduce the hydroxyl groups on $TiO_2$ surface. As the concentration of $NH_4OH$ was increased, the short-circuit current density ($J_{SC}$) value and conversion efficiency of solar cells were increased because the amount of adsorbed dye molecules on $TiO_2$ surface was increased. As a result of the surface modification to introduce hydroxyl groups, the concentration of adsorbed dye on the $TiO_2$ surface could be improved up to 32.61% without the changes of morphology, surface area and pore volume of particles. The morphology, the specific surface area, the pore volume and the chemical states of $TiO_2$ surface were characterized by using FE-SEM, $N_2$ adsorption-desorption isotherms and XPS measurements. The amount of adsorbed dye and the performance of fabricated cells were analyzed by using UV-Vis absorption spectroscopy and solar simulator.

• Korean Journal of Materials Research
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• v.27 no.4
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• pp.221-228
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• 2017

Various morphologies of copper oxide (CuO) have been considered to be of both fundamental and practical importance in the field of electronic materials. In this study, using Cu ($0.1{\mu}m$ and $7{\mu}m$) particles, flake-type CuO particles were grown via a wet oxidation method for 5min and 60min at $75^{\circ}C$. Using the prepared CuO, AlN, and silicone base as reagents, thermal interface material (TIM) compounds were synthesized using a high speed paste mixer. The properties of the thermal compounds prepared using the CuO particles were observed by thermal conductivity and breakdown voltage measurement. Most importantly, the volume of thermal compounds created using CuO particles grown from $0.1{\mu}m$ Cu particles increased by 192.5 % and 125 % depending on the growth time. The composition of CuO was confirmed by X-ray diffraction (XRD) analysis; cross sections of the grown CuO particles were observed using focused ion beam (FIB), field emission scanning electron microscopy (FE-SEM), and energy dispersive analysis by X-ray (EDAX). In addition, the thermal compound dispersion of the Cu and Al elements were observed by X-ray elemental mapping.

• Journal of The Korean Astronomical Society
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• v.41 no.2
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• pp.23-37
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• 2008

The high-resolution optical region spectroscopic data of the symbiotic nova AG Peg secured with the Hamilton Echelle Spectrograph at the Lick Observatory, have been analyzed along with the International Ultraviolet Explorer UV archive data. We measure about 700 line intensities in the wavelengths of 3859 to $9230{\AA}$ and identify about 300 lines. We construct pure photoionization models that represent the observed lines and the physical condition for this symbiotic nova. The spectral energy distribution of the ionizing radiation is adopted from stellar model atmospheres. Based on photoionization models, we derive the elemental abundances; C & N appear to be similar to be smaller than the Galactic planetary nebular value while O is enhanced. Our result is compared with the Contini (1997, 2003) who analyzed the UV region spectral data with the shock + ionization model. The Fe abundance appears to be enhanced than that of normal planetary nebulae, which suggests that AG Peg may have formed in the Galactic disk. The models indicate that the temperature of the central star which excite the shell gas may have fluctuated to an unexpected extent during the years 1998 - 2002.

• Journal of the Korean Ceramic Society
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• v.44 no.6 s.301
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• pp.313-318
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• 2007

ITO (Indium-tin oxide) thin films have been prepared by a sol-gel spinning coating method and fired and annealed in the temperature range of $450-600^{\circ}C$. The XRD patterns of the films indicated the main peak of (222) plane and showed higher crystallinity with increasing an annealing temperature. The surface of the ITO thin films were treated with 0.1 N HCl 20% solution at room temperature. The effects of surface treatment on electrical properties and surface morphologies of the ITO films were investigated with the results of sheet resistance and FE-SEM, AFM images. The samples, subsequently treated with acidic solution for 40 sec showed the sheet resistance of $0.982\;k{\Omega}/square$. The surface treatment using acidic solution diminished the RMS (root mean square) value and the residual carbon content of the ITO films. It seemed that the acid-cleaning of the ITO thin films lead to the decrease of surface roughness and sheet resistance.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.97-102
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• 1998

Transition metal Cr3+ and Fe3+ ion was diffused in white sapphire {0001}, {1010} crystal plane which were grown by the Verneuil method. It enhanced and changed the physical, electrical and optical properties of sapphires. After mixing the metallic oxide and metal powder, it were used for diffusion. Metallic oxide was synthesized by precipitation method and it's composition was mainly alumina which doped with chromium or ferric oxide. In case using metallic oxide, the dopping was slowly progressed and it needed the longer duration time and higher temperature, relatively. Metallic powder was vapoured under 1x10-4 torr of vacuum pressure at 1900(iron metal) and 2050(chromium)℃, first step. Diffusion condition were kept by 6atm of N2 accelerating pressure at 2050∼2150℃. Each surface density of sapphire crystal are 0.225(c) and 0.1199atom/Å2(a). The color of the Cr-doped sapphires was changed to red. Dopping reaction was come out more deep in th plane of {1010} than {0001}. It was speculated that the planar density was one of the factors to determine diffusion effect.

• Journal of Environmental Health Sciences
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• v.15 no.1
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• pp.51-62
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• 1989

This survey was performed to investigate contamination degree and significance in each item of 406 samples of ground water, which was collected in Seoul area from Jan. to Dec. 1988. The results of this study were as follows 1. The unsuitable rate of ground water investigated was 69.7%(32.4% in only bacteria, 23.6% in both bacteria and physico-chemistry and 13.6% in only physico-chemical contamination). 2. The unsuitable rate in each item was the highest(54.2%) in standard plate countland 29.8% in coliform, 12.8% in turbidity, 11.3% in Zn, and 10.8% in Mn. 3. The total mean concentrations in each item were lower than standard except standard plate count, coliform, and Fe. 4. In the analysis of corelation, among items, both total hardness and residual solids were showed very high correlationship (P < 0.01) with other items, and both S.P.C. and coliform showed very highly significant (P < 0.01) with NH$_3$-N.