• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.276-279
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• 2002

$Bi_{2}Sr_{2}CaCu_{2}O_{x}$ was prepared by the conventional method of solid state reaction and SHS method. The samples were annealed in different atmosphere in order to examine the influence of atmospheres on the carbon contents in the $Bi_{2}Sr_{2}CaCu_{2}O_{x}$ compound. The lowest carbon content in $Bi_{2}Sr_{2}CaCu_{2}O_{x}$ could be attended when the sample was annealed in $O_{2}$ at $800^{\circ}C$ for 100 hours. The $CO_{2}$ in air pollute the samples and increase the carbon content in the sintering process. The critical current density of the $Bi_{2}Sr_{2}CaCu_{2}O_{x}$ samples will decrease with the increasing carbon contents in the samples. The impurity carbon will deposit in the grain boundary, which makes critical current density lower.

• Journal of the Korean Applied Science and Technology
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• v.23 no.3
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• pp.199-206
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• 2006

Direct decomposition of methane over three types of carbon black (N330-p, N330-f, and HI-900L) was carried out in a fluidized bed quartz reactor. Properties of carbon black before and after reaction were measured and found to be related with surface structure and weight gain. For N330-p and N330-f, some carbon deposit on the surface was considered to be the reason for the increase of BET surface area and pore volume with weight gain. Carbon deposits on the surface and the conglutination of some aggregates may explain the slight increase of particle size. Properties of HI-900L changed much more significantly with weight gain. It is supposed that the increase of aggregate size of HI-900L were due to some unknown oily components. The corresponding agglomeration might be the reason for the decrease of BET surface area with weight gain, as compared with the increase of that for the case of N330 black.

• Journal of the Korean Institute of Gas
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• v.16 no.3
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• pp.48-53
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• 2012

The purpose of this paper studies the failure cases including with system of liquefied phase injection in liquified petroleum gas vehicle. The first case, resulting with inspection the injector of LPG, it occasionally certified the injection damage phenomenon that the fuel efficiency(km/l) was decreased to 5% by carbon deposit with injector hole when the driver operates the vehicle. The second case, it certified the interference phenomenon of air flow with carbon deposit in ISA system control for idle speed of engine and throttle body suppling air into engine. As a result, the fuel efficiency was decreased 7%. The third case, the outer air during intake stroke was intermittently flowed in this gasket gap because of weaken adhesion power phenomenon for cylinder block by intake manifold gasket tearing. Consequentially, it certified the decrease for fuel efficiency to 3% by risen the amount of fuel injection as the air inflow quantity. These failure examples reduced the power performance of engine and the fuel efficiency of vehicle. It have to minimize of failure phenomenon preparing through quality management.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.139-144
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• 2007

This paper presents development of carbon nanotube (CNT) tip modified by focused ion beam (FIB) and experimental results in non-contact mode of atomic force microscopy (AFM) using fabricated tip. We used an electric field which causes dielectrophoresis, to align and deposit CNTs on a conventional silicon tip. The morphology of the fabricated CNT tip was then modified into a desired shape using focused ion beam. We measured anodic aluminum oxide sample and trench structure to estimate the performance of FIB-modified tip and compared with those of conventional Si tip. We demonstrate that FIB modified tip in non contact mode had superior characteristics than conventional tip in the respects of wear, image resolution and sidewall measurement.

• Journal of Welding and Joining
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• v.6 no.2
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• pp.40-46
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• 1988

The effect of heat input on the content of residual .delta.-ferrite and the hot cracking susceptibility in the austenitic stainless steel overlaid on the carbon steel was studied in the range of heat input from 7.5 to 15.1 KJ/cm. Present study shows that residual .delta.-ferrite content in the overlay is mainly determined by the dilution of the base metal (carbon steel) which is in turn affected by heat input, i.e. the amount of dilution decreases as heat input increase. Accordingly, higher heat input results in a substantial increase in Cr equivalent but a little increase in Ni equivalent due to the less dilution of carbon from base metal. This fact can explain the result obtained in this study, i, e, the higher content of .delta.-ferrite in the weld deposit made with higher heat input. This in turn causes more resistant overlaying weld metal to hot cracking.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.461-462
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• 2006

This paper reports on the development of a scanning probe microscopy(SPM) tip with caborn nanotubes. We used an electric field which causes dielectrophoresis(DEP), to align and deposit CNTs on a metal-coated SPM tip. Using the CNT attached SPM tip, we have obtained an enhanced resolution and wear property compared to that from the bare silicon tip through the scanning of the surface of the bio materials. The carbon nanotube tip align toward the source of the ion beam allowing their orientation to be changed at precise angles. By this technique, metal coated carbon nanotube tips that are several micrometer in length are prepared for scanning probe microscopy.

• Laser Solutions
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• v.2 no.2
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• pp.34-41
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• 1999

A RS840 $CO_2$laser and a powder auto-feeding apparatus have been used to deposit single tracks of Ni-base superalloy on low carbon steel. In this paper, the effects of laser cladding parameters on clad geometry, dilution and microhardness are studied. As a results, the w/h ratio of the clad layer increases with decreasing powder feed rate and increasing laser scan speed. Increase of powder density and decrease of specific energy have little effect on dilution. It was found that the clad layer of the highest hardness has a structure in which fine and leaf like phases are dispersed in ${\gamma}$Ni matrix.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.29-30
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• 2001

This paper presents some results of plasma nitriding on hard chromium deposit. The substrates were C45 steel and $30~50{\;}\mu\textrm{m}$ of chromium deposit by electroplating was formed. Plasma nitriding was carried out in a plasma nitriding system with $95NH_3{\;}+{\;}SCH_4$ atmosphere at the pressure about 600 Pa and different temperature from $450^{\circ}C{\;}to{\;}720^{\circ}C$ for various time. Optical microscopy and X-ray diffraction were used to evaluate the characteristics of surface nitride layer formed by nitrogen diffusion from plasma atmosphere inward iCr coating and interface carbide layer formed by carbon diffusion from substrate outward Cr coating. The microhardness was measured using microhareness tester at the load of 100 gf. Corrosion resistance was evaluated using the potentiodynamic measurement in 3.5% NaG solution. A saturated calomel electrode (SiCE) was used as the reference electrode. Fig.1 shows the typical microstructures of top surface and cross-section for nitrided and unnitrided samples. Aaer plasma nitriding a sandwich structure was formed consisting of surface nitride layer, center chromium layer and interface carbide layer. The thickness of nitride and carbide layers was increased with the increase of processing temperature and time. Hardness reached about 1000Hv after nitriding while 900Hv for unnitrided hard chromium deposit. X-ray diffraction indicated that surface nitrided layer was a mixture of $Cr_2N$ and CrN at low temperature and erN at high temperature (Fig.2). Anodic polarization curves showed that plasma nitriding can greatly improve the corrosion resistance of chromium e1ectrodeposit. After plasma nitriding, the corrosion potential moved to noble direction and passive current density was lower by 1 to 4 orders of magnitude compared with chromium deposit(Fig.3).

• Journal of Surface Science and Engineering
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• v.50 no.6
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• pp.531-535
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• 2017

Enormous amount of waste oyster-shell (OS) has a major disposal problem in coastal regions. OSs have attracted much attention for recycling, because these are mainly composed of calcium carbonate with rare impurities. In this study, we demonstrate the calcareous deposit films on steel plate by using OSs on the basic of cathodic protection technique. The composition of the OSs was analyzed by wavelength dispersive X-ray fluorescence spectrometer. Carbon dioxide gas was pumped into distilled water to make carbonic acid solution for dissolution of OS. The calcareous deposit was characterized by second electron microscope (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction. Corrosion rates were estimated by measurements of anodic polarization and immersion test. It is confirmed that calcareous deposits on steel plate are formed under all condition of cathodic protection by using waste OS from the SEM and EDX results. Calcareous deposits on steel by OS provide good corrosion resistance by acting as a barrier to oxygen supply to the steel surface.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1016-1022
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• 2010

An Experimental study of cleaning solution has been performed on a high capacity steam boiler burning heavy fuel oil to on-line cleaning of deposit. The deposit is mixture of soot, slag, ash, metal oxide and clinker. The traditional technology of deposit cleaning was carried hand-crafted. The conventional technology of boiler cleaning method is mechanical removal by the worker while the boiler shut down operation. In this experiment, the deposit of mixture of soot, slag, ash, metal oxide and clinker has been removed by the cleaning agents without shut down of boiler burning. This study found out the optimum cleaning solution composition. The best results have been obtained when the mixture of ammonium nitrate and $MgNO_3$ were used in cleaning solution. The various transition metal effect was investigated for optimum mixing condition. In this research, the metal compound additive of the clean solution compoition was obtained. The combustion efficiency was improved by on-line cleaning with derived clean solution compoition. On-line cleaning method prevents the fouling and corrosion in the boiler and heat exchanger.