• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.10a
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• pp.80-80
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• 2006

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.10a
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• pp.66-66
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• 2006

• Korean Journal of Materials Research
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• v.10 no.7
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• pp.505-514
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• 2000

The carburizing behavior and fatigue properties of the plasma carburized low carbon Cr-Mo steel(0.176C-1.014Cr-0.387Mo) have been investigated. The effective case depth in plasma carburized steel increased up to 50% in comparison with that of gas carburizing, and this case depth increased with the increasing surface carbon content. With increasing time in plasma carburizing, the surface carbon content increased but its increasing rate decreased. Fatigue properties were studied in terms of microstructure, case depth, retained austenite and residual stress near the surface. The fatigue limit of the plasma carburized steel was higher than that of gas carburized one. The initiation of microcracks and initial crack propagation were retarded due to a relatively little surface and internal oxidation layer in plasma carburized steel. Fractography showed the crack initiated at the surface, and transgranular fracture at surface layer was more predominant in plasma carburized steel compared to that of gas carburized steel.

• Journal of the Korean institute of surface engineering
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• v.47 no.5
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• pp.252-256
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• 2014

The TiAlCrSiN film was deposited on the WC-20%TiC-10%Co carbide, and its oxidation behavior was examined at $700-1000^{\circ}C$. It displayed relatively good oxidation resistance owing to the formation of $TiO_2$, $Al_2O_3$, $Cr_2O_3$, and $SiO_2$ up to $900^{\circ}C$. However, at $1000^{\circ}C$, the fast oxidation rate and partial oxidation of WC in the substrate led to the formation of the thick, fragile oxide scale.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.33-40
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• 2010

In this research, the effects for surface Improvement of plasma ion implanted carbide endmill tools were observed by measuring cutting forces and tools wear affecting surface roughness in high speed cutting. From the 2nd ion mass analysis, the oxidation layer was found to be built up by sputtering. The residual gas contamination of oxygen was found to be contained impurities in nitrogen gas. The plasma implanted ion was found to be spreaded, especially the nitrogen was implanted up to 150nm depth as impressed voltage and ion implanting time. It is analyzed as bring surface improvement by spreading deeply forming oxidation on surface. The factors in Analysis of Variance(ANOVA) about mutuality cause reference of cutting force. The cutting force Fx is affected by the interaction of spindle rpm and federate, the cutting force Fy is influenced by spindle rpm and time injected ion, and cutting force Fz is affected by the interaction of impressed voltage and feedrate. Also, it was found that the cutting forces of implanted tools become lower and the surface roughness is improved by the effect of nitrogen according to the implantation.

• Journal of the Korean institute of surface engineering
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• v.35 no.6
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• pp.391-400
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• 2002

Corrosion characteristics of Ti, Ti/Cr coated and plasma-nitrided surface for stainless steel containing Ti have been studied. Stainless steels containing 0.09-0.92wt% Ti were fabricated by using vacuum furnace and solutionized for 1hr at 105$0^{\circ}C$. Ti and Cr coatings were done on solutionized stainless steel surface by EB-PVD. The Ti coated specimen were coated by Cr and were nitrided by plasma at $450^{\circ}C$ for 5hr. Microstructure and phase analysis were performed using SEM, OM and EDX. Corrosion behavior of the coated specimen was investigated by electrochemical test. The coated surface was of fine columnar structure. The Ti/Cr coated surface was denser than the Ti coated and the Ti coated-nitrided surfaces. The corrosion and pitting potential increased in proportion to the Ti content, coating temperature, coating thickness and formation of stable oxide film. The current density in active and passive region decreased in the case of Ti/Cr coated sample and Ti coated-nitrided samples. Especially the plasma nitrided specimen after Ti coating have a good corrosion resistance compared with the Ti coated specimen. The number and size of pits decreased as Ti content of matrix increased.

• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.89-98
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• 2003

Corrosion characteristics of Ti, Ti/Cr coated and plasma-nitrided surface for stainless steel containing Ti have been studied. Stainless steels containing 0.09-0.92wt% Ti were fabricated by using vacuum furnace and solutionized for 1hr at $1050^{\circ}C$. Ti and Cr coatings were done on solutionized stainless steel surface by EB-PVD. The Ti coated specimen were coated by Cr and were nitrided by plasma at $450^{\circ}C$ for 5hr Microstructure and phase analysis were performed using SEM, OM and EDX. Corrosion behavior of the coated specimen was investigated by electrochemical test. The coated surface was of fine columnar structure. The Ti/Cr coated surface was denser than the Ti coated and the Ti coated-nitrided surfaces. The corrosion and pitting potential increased in proportion to the Ti content, coating temperature, coating thickness and formation of stable oxide film. The current density in active and passive region decreased in the case of Ti/Cr coated sample and Ti coated-nitrided samples. Especially the plasma nitrided specimen after Ti coating have a good corrosion resistance compared with the Ti coated specimen. The number and size of pits decreased as Ti content of matrix increased.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.157-157
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• 2017

Titanium and its alloys that have a good biocompatibility, corrosion resistance, and mechanical properties such as hardness and wear resistance are widely used in dental and orthopedic implant applications. They can directly connect to bone. However, they do not form a chemical bond with bone tissue. Plasma electrolytic oxidation (PEO) that combines the high voltage spark and electrochemical oxidation is a novel method to form ceramic coatings on light metals such as titanium and its alloys. This is an excellent reproducibility and economical, because the size and shape control of the nano-structure is relatively easy. Silicon (Si), manganese (Mn), and magnesium (Mg) has a useful to bone. Particularly, Si has been found to be essential for normal bone, cartilage growth and development. Manganese influences regulation of bone remodeling because its low content in body is connected with the rise of the concentration of calcium, phosphates and phosphatase out of cells. Insufficience of Mn in human body is probably contributing cause of osteoporosis. Pre-studies have shown that Mg plays very important roles in essential for normal growth and metabolism of skeletal tissue in vertebrates and can be detected as minor constituents in teeth and bone. The objective of this work was to study nucleation and growth of bone-like apatite formation on Ti-6Al-4V in solution containing Mn, Mg, and Si ions after plasma electrolytic oxidation. Anodized alloys was prepared at 270V~300V voltages. And bone-like apatite formation was carried out in SBF solution for 1, 3, 5, and 7 days. The morphologies of PEO-treated Ti-6Al-4V alloy in containing Mn, Mg, and Si ions were examined by FE-SEM, EDS, and XRD.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.2
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• pp.204-210
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• 2000

The antioxidative effects of solvent fractions of kimchi on LDL oxidatiojn in vitro as well as hypolipidemic effects of these fractions in rabbit fed atherogenic diet were studied. Methanol extract of deffated kimchi was fractionated sequentially with dichloromethane, ethylacetate, butanol and water. All solvent fractions of kimchi inhibited Cu2+-induced LDL oxidation. Among these fractions, the dicholoromethane fraction at the concentration of 25$\mu\textrm{g}$/mL showed the highest antioxidant effects against LDL oxidation in the aspect of inhibiting TBARS production by 28.03% or prolonged lag phase duration 2-fold compared to those of control. Based on the results from in vitro study, New Zealand White Rabbits grouped six each were fed for 8 weeks either basal diet containing 1% cholesterol or experimental diet containing dichloromethane, ethylacetate or water fraciton added to the basal diet. The amount of solvent fraction of kimchi added to the experimental diet was equivalent to 5% of freeze-dried kimchi. The hypolipidemic effects was observed from all experimental gropus, especially from dichloromethane fraction added group. The plasma and LDL cholesterol levels of this group were decreased by 49% and 47%, respectively while that of HDL increased by 91% compared to those of control. The calculated atherogenic index for the dichloromethane group was the lowest among groups. However, TG lowering effect of experimental group was not observed since solbent fraction of kimchi was used instead of freeze-dried kimchi. The TBARS concentration of LDL isolated from rabbit fed dichloromethane fraction was decreased 21% than that of control. These results indicate that active principles responsible for inhibiting LDL oxidation and lowering plasma cholesterol may present abundantly in dichloromethane fraction of kimchi.

• Korean Journal of Metals and Materials
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• v.48 no.1
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• pp.49-56
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• 2010

This study investigated how the surface of Al-12wt.%Si alloy modified by the plasma electrolytic oxidation process (PEO). The PEO process was performed in an electrolyte with sodium hexametaphsphate as a conducting salt, and the effect of ammonium metavanadate on variations in the morphology of electrochemically generated oxide layers on the alloy surface was investigated. It is difficult to form a uniform passive oxide layer on Al alloys with a high Si content due to the differences in the oxidation behavior of the silicon-rich phase and the aluminum-rich phase. The oxide layer covered the entire surface of the Al-12WT.%Si alloy uniformly when ammonium metavanadate was added to the electrolyte. The oxide layer was confirmed as a mixture of $V_2O_3$ and $V_2O_5$ by XPS analysis. In addition, the oxide layer obtained by the PEO process with ammonium metavanadate exhibited a black color. Application of this surface modification method is expected to solve the problem of the lack of uniformity in the coloring of oxide layeres caused by different oxidation behaviors during a surface treatment.