• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.294-299
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• 2003

The efficiency of complex slurry preparation route for the development of high performance RS-SiCf/SiC composites has been investigated. The green bodies for RS-SiC and RS-SiCf/SiC composite materials prior to the infiltration of molten silicon were prepared with various C/SiC complex matrix slurries, which associated with both different sizes of starting SiC particles and blending ratios of starting SiC and carbon particles. The reinforcing materials in the composite system were uncoated and C coated Tyranno SA SiC fiber. The characterization of RS-SiC and RS-SiCf/SiC composite materials was examined by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, process optimization methodology is discussed.

• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.393-401
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• 1997

Commercial flake graphite cast iron substrate was coated with titanium powder by low pressure plasma spraying and was irradiated with a $CO_2$ laser to produce the wear resistant composite layer. From the experimental results of this study, it was possible to composite TiC particles on the surface layer by direct reaction between carbon existed in the cast iron matrix and titanium with thermal sprayed coating by remelting and alloying them using laser irradiation. The cooling rate of laser remelted cast iron substrate without titanium coating was about $1{\times}10^4$ K/s to $1{\times}10^5$ K/s in the order under the condition used in this study. The microstructure of alloyed layer consisted of three zones, that is, TiC particule crystallized zone (MHV $400{\sim}500$), the mixed zone of TiC particule+ledebulite (MHV $650{\sim}900$) and the ledebulite zone (MHV $500{\sim}700$). TiC particules were crystallized as a typical dendritic morphology. The secondary TiC dendrite arms were grown to the polygonized shape and were necking. And then the separated arms became cubic crystal of TiC at the slowly solidified zone. But in the rapidly solidified zone of fusion boundry, the fine granular TiC particules were grouped like grape.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.363-363
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• 2010

The high capillarity of a plastic fiber network having superhydrophilic Si-DLC coating is studied. Although the superhydrophilic surface maximize wetting ability on the flat surface, there remains a requirement for the more wettable surface for various applications such as air-filters or liquid-filters. In this research, the PET non-woven fabric surface was realized by superhydrophilic coating. PTE non-woven fabric network was chosen due to its micro-pore structure, cheap price, and productivity. Superhydrophobic fiber network was prepared with a coating of oxgyen plasma treated Si-DLC films using plasma-enhanced chemical vapor deposition (PECVD). We first fabricated superhydrophilic fabric structure by using a polyethylene terephthalate (PET) non-woven fabric (NWF) coated with a nanostructured films of the Si-incorporated diamond-like carbon (Si-DLC) followed by the plasma dry etching with oxygen. The Si-DLC with oxygen plasma etching becomes a superhydrophilic and the Si-DLC coating have several advantages of easy coating procedure at room temperature, strong mechanical performance, and long-lasting property in superhydrophilicity. It was found that the superhydrophobic fiber network shows better wicking ability through micro-pores and enables water to have much faster spreading speed than merely superhydrophilic surface. Here, capillarity on superhydrophilic fabric structure is investigated from the spreading pattern of water flowing on the vertical surface in a gravitational field. As water flows on vertical flat solid surface always fall down in gravitational direction (i.e. gravity dominant flow), while water flows on vertical superhydrophilic fabric surface showed the capillary dominant spreading.

• Journal of the Korean institute of surface engineering
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• v.31 no.3
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• pp.142-150
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• 1998

Stainless steel is being used widely for various purposes due to its good corrosion resistance. There has been much research to produce colored stainless steel by several methods such as anodizing and ion plating. In this experiment, we coated TiN(C,O,H)films SUS304 substraate with the DC magnetron spttering system made by Leybold Heraeus and studied the interlater structure and abhesive strength of the films as a function of additional gases, acetylene, hydrogen and oxygen. When the acetylene gas was added into the chamber, the specimen with the interlayer phase had good adhesion due to the toughness of the $\gamma'-Fe_4N$ plase induced from a solid solution of carbon atoms, while low adhesion appeared on the specimen of the non interlayer phase. The formation of the interlayer phase($\gamma'-Fe_4N$) was due to hydrogen embrittlement and internal stress induced by $\gamma'-Fe_4N$ formation in the interlayer. We could fine the interlayer phase ($\gamma'-Fe_4N$) at the interface between the film and the substrate of the TEM image when $\gamma'-Fe_4N$ was detected by the X-ray duffraction metheod.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.27 no.1
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• pp.17-23
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• 2021

Recent studies on recyclable materials in the packaging have an increased attention due to the eco-friendly policies of reducing carbon dioxide emissions in worldwide. Roasted coffee beans mostly packed in multi-layered films and papers according to their expiration date. To satisfy both recyclability and barrier properties, researches have been continued on paper-based packaging materials to enhance their properties. In this study, packaging materials for coffee beans are developed by laminating bioplastic films on papers. The tests of packaging materials were performed with mechanical properties, gas and water vaper permeability, recyclability and storage quality for coffee beans. Compared to other samples, the paper/bioplastics-based coffee package composed of starch coated papers and two bioplastics showed the lowest barrier properties, comparable mechanical strength and ability to maintain the quality of roasted coffee beans. Thus, it could be a good alternative for multi-layered packages for roasted coffee beans.

• Journal of Electrochemical Science and Technology
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• v.12 no.1
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• pp.74-81
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• 2021

Silicon (Si) is recognized as a promising anode material for high-energy-density lithium-ion batteries. However, under a condition of electrode comparable to commercial graphite anodes with low binder content and a high electrode density, the practical use of Si is limited due to the huge volume change associated with Si-Li alloying/de-alloying. Here, we report a novel core-shell composite, having a reversible capacity of ~ 500 mAh g-1, by forming a shell composed of a mixture of nano-Si, graphite nanosheets and a pitch carbon on a spherical natural graphite particle. The electrochemical measurements are performed using electrodes with 2 wt % styrene butadiene rubber (SBR) and 2 wt.% carboxymethyl cellulose (CMC) binder in an electrode density of ~ 1.6 g cm-3. The core-shell composites having the reversible capacity of 478 mAh g-1 shows the outstanding capacity retention of 99% after 100 cycles with the initial coulombic efficiency of 90%. The heterostructure of core-shell composites appears to be very effective in buffering the volume change of Si during cycling.

• Journal of the Korean institute of surface engineering
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• v.53 no.6
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• pp.360-368
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• 2020

Wear resistance of cutting tools is one of the most important requirements in terms of the durability of cutting tool itself as well as the machining accuracy of the workpiece. Generally, tungsten carbide ball end mills have been processed with hard coatings for high durability and wear resistance such as diamond coating and tetrahedral amorphous carbon(ta-C) coating. In this study, we developed multilayer ta-C coatings whose wear resistance is comparable to that of diamond coating. First, we prepared single layer ta-C coatings according to the substrate bias voltage and Ar gas flow, and the surface microstructure, raman characteristics, hardness and wear characteristics were evaluated. Then, considering the hardness and wear resistance of the single layer ta-C, we fabricated multilayer coatings consisting of hard and soft layers. As a result, it was confirmed that the wear resistance of the multilayer ta-C coating with hardness of 51 GPa, and elastic recovery rate of 85% improved to 97% compared to that of the diamond coated ball end mill.

• Journal of the Korea Institute of Building Construction
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• v.21 no.6
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• pp.539-550
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• 2021

In this study, Zn and Zn-15Al were coated on general carbon steel by plasma arc metal spraying and then immersed in a 3.5wt.% NaCl solution similar to the seawater environment to evaluate the corrosion resistance properties. Through the surface shape analysis test by SEM and XRD, it was found that the Zn coating was porous and needle-shaped, so the penetration of the electrolyte was easy, and thus the corrosion rate was rapid. On the other hand, the Zn-15Al coating had a uniform and dense shape and was shown to suppress corrosion.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.5
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• pp.262-269
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• 2022

In order to process materials such as engineering plastics, which are difficult to mold due to their high strength compared to conventional polymer materials, it is necessary to improve the hardness and strength of parts such as screws and barrels of injection equipment in extrusion system. High-velocity oxygen fuel (HVOF) process is well known for its contribution on enhancement of surface properties. Thus in this study, using the HVOF process, WC coating layers of different thicknesses were bonded to the surface of S30C substrate by controlling the movement speed of the spray nozzle and each property was evaluated to decide the optimization condition. Through the results, the thickness of WC coating layer increased from 0 to 200 ㎛ maximum, along with the decrement of nozzle movement speed and the surface hardness get increased. Especially, the coated layer with the thickness over 180 ㎛ under the nozzle speed 500 mm/s had high hardness than thinner layer. In addition, the amount of wear consumed per unit time was also significantly reduced due to the formation of the coating layer.

• Journal of the Korean Electrochemical Society
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• v.17 no.1
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• pp.37-43
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• 2014

In this study, capacitive deionization (CDI) was introduced for desalination of mining water. Ion-exchange polymer coated carbon electrodes (IEE) were used in CDI to desalt mining water. The CDI performance using the IEE for desalination of mining water was carried out and then was compared with that using general carbon electrodes without ion-exchange polymer coating (GE). Moreover, to investigate the effect of the concentration of influent solutions on CDI performance, the CDI performance using the IEE for desalination of brackish water (NaCl 200 ppm) was also performed and analyzed. As a result, the higher salt removal efficiency, rate and the lower energy consumption in the CDI process using the IEE and mining water were obtained compared with those using the GE and mining water. It is mainly due to higher non-Faradaic current, low ohmic resistance of the influent, overlapping effect of electric double layers in micropore of the electrode. In addition, the CDI process using the IEE and brackish water shows much higher salt removal efficiency and lower salt removal rate than that using the IEE and mining water. This results from the lower concentration (i.e., higher ohmic resistance) and salt amount of the influent.