• Journal of Korea Foundry Society
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• v.39 no.2
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• pp.26-31
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• 2019

In this study, the mechanical characteristics and microstructure of hypereutectic Al-17Si-5Fe extruded alloys prepared by a rapid solidification process (RSP) were investigated. The hypereutectic Al alloy was fabricated by means of RSP and permanent casting. For RSP, the Al alloy melted at $920^{\circ}C$, cooling the specimens at a rate of $10^6^{\circ}C/s$ when the RSP was used, thus allowing the refining of primary Si particles more than when using permanent casting, at a rate of about 91%. We tested an extrusion RSP billet and a permanent-cast billet. Before the hot-extrusion process, heating to $450^{\circ}C$ took place for one hour. The samples were then hotextruded with a condition of extrusion ratio of 27 and a ram speed of 0.5 mm/s. Microstructural analyses of the extruded RSP method and the permanent casting method were carried out with OM and SEM-EDS mapping. The mechanical properties in both cases were evaluated by Vickers micro-hardness, wear resistance and tensile tests. It was found that when hypereutectic Al-17Si-5Fe alloys were fabricated by a rapid solidification method, it becomes possible to refine Si and intermetallic compounds. During the preparation of the hypereutectic Al-17Si-5Fe alloy by the rapid solidification method, the pressure of the melting crucible was low, and at faster drum speeds, smaller grain alloy flakes could be produced. Hot extrusion of the hypereutectic Al-17Si-5Fe alloy during the rapid solidification method required higher pressure levels than hot extrusion of the permanent mold-casted alloy. However, it was possible to produce an extruded material with a better surface than that of the hot extruded material processed by permanent mold casting.

• Journal of radiological science and technology
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• v.38 no.1
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• pp.1-6
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• 2015

Whole spine scanography (WSS) is a radiological examination that exposes the whole body of the individual being examined to x-ray radiation. WSS is often repeated during the treatment period, which results in a much greater radiation exposure than that in routine x-ray examinations. The aims of the current study were to evaluate the patient dose of WSS using computer simulation, image magnification and angulation of phantom image using different patient position. We evaluated the effective dose(ED) of 23 consecutive patients (M : F = 13:10) who underwent WSS, based on the automatic image pasting method for multiple exposure digital radiography. The Anterior-Posterior position(AP) and Posterior-Anterior position( PA) projection EDs were evaluated based on the PC based Monte Carlo simulation. We measured spine transverse process distance and angulation using DICOM measurement. For all patient, the average ED was 0.069 mSv for AP position and 0.0361 mSv for PA position. AP position calculated double exposure then PA position. For male patient, the average ED was 0.089 mSv(AP) and 0.050 mSv(PA). For female patient, the average ED was 0.0431 mSv(AP) and 0.026 mSv(PA). The transverse process of PA spine image measured 5% higher than AP but angulation of transverse process was no significant differences. In clinical practice, just by change the patient position was conformed to reduce the ED of patient. Therefor we need to redefine of protocol for digital radiography such as WSS. whole spine scanography, effective dose, patient exposure dose, exposure direction. protocol optimization.

• Journal of Surface Science and Engineering
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• v.49 no.2
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• pp.166-171
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• 2016

Cathodic protection is widely recognized as the most cost effective and technically appropriate corrosion prevention methodology for the port, offshore structures, ships. When applying the cathodic protection method to metal facilities in seawater, on the surface of the metal facilities a compound of calcium carbonate($CaCO_3$) or magnesium hydroxide($Mg(OH)_2$) films are formed by $Ca^{2+}$ and $Mg^{2+}$ ions among the many ionic components dissolving in the seawater. And calcareous deposit films such as $CaCO_3$ and $Mg(OH)_2$ etc. are formed by the surface of the steel product. These calcareous deposit film functions as a barrier against the corrosive environment, leading to a decrease in current demand. On the other hand, the general calcareous deposit film is a compound like ceramics. Therefore, there may be some problems such as weaker adhesive power and the longer time of film formation uniting with the base metal. In this study, we tried to determine and control the optimal condition through applying the principle of cathodic current process to form calcareous deposit film of uniform and compact on steel plate. The quantity of precipitates was analyzed, and both the morphology, component and crystal structure were analyzed as well through SEM, EDS and XRD. And based on the previous analysis, it was elucidated mechanism of calcareous deposit film formed in the sacrificial anode type (Al, Zn) and current density (1, 3, $5A/m^2$) conditions. In addition, the taping test was performed to evaluate the adhesion.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.16-21
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• 2016

Silicon/Carbon/CNT composites as anode materials for lithium-ion batteries were synthesized to overcome the large volume change during lithium alloying-de alloying process and low electrical conductivity. Silicon/Carbon/CNT composites were prepared by the fabrication processes including the synthesis of SBA-15, magnesiothermic reduction of SBA-15 to obtain Si/MgO by ball milling, carbonization of phenolic resin with CNT and HCl etching. The prepared Silicon/Carbon/CNT composites were analysed by XRD, SEM, BET and EDS. In this study, the electrochemical effect of CNT content to improve the capacity and cycle performance was investigated by charge/discharge, cycle, cyclic voltammetry and impedance tests. The coin cell using Silicon/Carbon/CNT composite (Si:CNT=93:7 in weight) in the electrolyte of $LiPF_6$ dissolved in organic solvents (EC:DMC:EMC=1:1:1 vol%) has better capacity (1718 mAh/g) than those of other composition coin cells. The cycle performance of coin cell was improved as CNT content was increased. It is found that the coin cell (Si:CNT=89:11 in weight) has best capacity retension (83%) after 2nd cycle.

• Conservation Science in Museum
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• v.1
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• pp.87-91
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• 1999

During the process of conservation treatment for the shoes[object No. Bon 7038], a red piece of textile was discovered. It was confirmed that hematite(Fe₂O₃) was used as pigment, through the following scientific examinations as color measurements, solubility in a particular solvent, discoloration, thin-section investigation of cross section under the microscope, composition analysis by SEM-EDS and etc. This is the first red pigment of Kaya period discovered so far, and it is significant because it exists on textile. Besides, red pigment discovered on the shield trace excavated from Tomb No. 11 of Daesung-dong in Kimhae was confirmed as Mercury sulfide(HgS). These two facts testify that similar red pigments had been used both in Kaya and Three Kingdoms around the same period.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.289-295
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• 2017

The International Maritime Organization (IMO) in accordance with the regulations with respect to the combustion gases, such as NOx, SOx generated by the marine engine. The combustion gases must be equipped with a device to reduce emissions from all ships passing through the Baltic SECAs. In Korea, the International Maritime Organization (IMO) and the development of a device for NOx, SOx reduction. Scrubber is used in the ammonia water and the Urea solution in the waste water. The waste water containing ammonium nitrate and ammonium sulfate, react of the NOx and SOx gas. In this study, the recovery of by-product, which contains the waste water was used as an organic solvent extraction method of salting out. Ammonium nitrate and ammonium sulfate, the recovery process. A qualitative analysis of the collected by-product FT-IR analysis. Through the elemental analysis and SEM-EDS, characteristic evaluation was performed with an impurity.

• Particle and aerosol research
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• v.6 no.2
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• pp.51-59
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• 2010

ZnO quantum dots embedded in a silica matrix without agglomeration were synthesized from $TEOS:Zn(NO_3)_2$ solutions in one-step process by aerosol-gel method. It was successfully demonstrated that the size of ZnO Q-dots could be controlled from 2 to 7 mm verified by a high resolution transmission electron microscope observation. The line scanning energy dispersive X-ray spectroscopy(EDS) revealed that the Q-dots existed preferentially inside SiO2 sphere when Zn/Si < 0.5. However, the Q-dots distributed homogeneously all over the sphere when Zn/Si > 1.0. Blue-shifted UV/Vis absorption peak observation confirmed the quantum size effect on the optical properties. The photoluminescence(PL) emission peaks of the powders at room temperature were consistent with previous reports in the following aspects: 1) PL characteristics are dominated by two peaks of deep-level defect-related emissions at 2.4 - 2.8 eV, 2) the first defect-related peak at 2.4 eV was blue shifted due to the quantum size effect with decreasing the concentration of $Zn(NO_3)_2$(decreasing the size of ZnO q dots). More interestingly, the existence of surface-exposed ZnO q dots affects greatly the second defect PL peak at 2.8 eV.

• Journal of Soil and Groundwater Environment
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• v.25 no.1
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• pp.95-105
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• 2020

In this study, iron nanoparticles impregnated hydrochar (FeNPs@HC) was synthesized using lignocellulosic waste and simple one-pot synthetic method. During hydrothermal carbonization (HTC) process, the mixture of lignocellulosic waste and ferric nitrate (0.1~0.5 M) as a precursor of iron nanoparticles was added and heated to 220℃ for 3 h in a teflon sealed autoclave, followed by calcination at 600℃ in N₂ atmosphere for 1 h. For the characterization of the as-prepared materials, X-ray diffraction (XRD), cation exchange capacity (CEC), fourier transform infrared spectrometer (FT-IR), Brunauer-Emmett-Teller (BET), transmission electron microscope (TEM), Energy Dispersive X-ray Spectroscopy (EDS) were used. The change of Fe(III) concentration in the feedstock influenced characteristics of produced FeNPs@HC and removal efficiency towards As(V) and Pb(II). According to the Langmuir isotherm test, maximum As(V) and Pb(II) adsorption capacity of Fe_0.25NPs@HC were found to be 11.81 and 116.28 mg/g respectively. The results of this study suggest that FeNPs@HC can be potentially used as an adsorbent or soil amendment for remediation of groundwater or soil contaminated with arsenic and cation heavy metals.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.87-92
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• 2001

Magnetic Fe-Co(C) nanocapsules and Fe-Co nanoparticles were prepared by arc-discharge in two kinds of atmospheres, i.e. methane and a mixture of ($H_2$+Ar), respectively. Characterization and magnetic properties of this two kinds of ultrafine particles were investigated systematically by means of X-ray diffraction, Mssbauer spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, energy disperse spectroscopy analysis, chemical analysis, oxygen determination and magnetization measurement. Effects of carbon element, decomposed from a methane atmosphere in carbon arc process, on phase structures, magnetic states and surface characterization were studied in comparison to that of Ar element. Two ultrafine particles showed a little difference in the weight ratio of (Fe/co) and the size for Fe-Co nanoparticles was about two times bigger than Fe-Co(C) nanocapsules. The saturation magnetization of Fe-Co (C) nanocapsules was about 8% higher than that of Fe-Co nanoparticles while their phase constitutions were similar. Although no carbon could be detected by XRD measurement because of extremely thin shells on the surfaces of the cores, it is still believed that they are carbon and oxygen layers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.481-486
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• 2010

ENIG (electroless Ni immersion gold) is one of surface finishing which has been most widely used in fine pitch SMT (surface mount technology) and BGA (ball grid array) packaging process. The reliability for package bondability is mainly affected by interfacial reaction between solder and surface finishing. Since the behavior of IMC (intermetallic compound), or the interfacial reaction between Ni and solder, affects to some product reliabilities such as solderability and bondability, understanding behavior of IMC should be important issue. Thus, we studied the properties of ENIG with P contents (9 wt% and 13 wt%), where the P contents is one of main factors in formation of IMC layer. The effect of P content was discussed using the results obtained from FE-SEM(field-emission scanning electron microscope), EPMA(electron probe micro analyzer), EDS(energy dispersive spectroscopy) and Dual-FIB(focused ion beam). Especially, we observed needle type irregular IMC layer with decreasing Ni contents under high P contents (13 wt%). Also, we found how IMC layer affects to bondability with forming continuous Kirkendall voids and thick P-rich layer.