• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.32-38
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• 2023

In this study, the electrochemical properties of dopamine coated silicon/silicon carbide/carbon(Si/SiC/C) composite materials were investigated to improve cycle stability and rate performance of silicon-based anode active material for lithium-ion batteries. After synthesizing CTAB/SiO₂ using the Stöber method, the Si/SiC composites were prepared through the magnesium thermal reduction method with NaCl as heat absorbent. Then, carbon coated Si/SiC anode materials were synthesized through polymerization of dopamine. The physical properties of the prepared Si/SiC/C anode materials were analyzed by SEM, TEM, XRD and BET. Also the electrochemical performance were investigated by cycle stability, rate performance, cyclic voltammetry and EIS test of lithium-ion batteries in 1 M LiPF₆ (EC: DEC = 1:1 vol%) electrolyte. The prepared 1-Si/SiC showed a discharge capacity of 633 mAh/g and 1-Si/SiC/C had a discharge capacity of 877 mAh/g at 0.1 C after 100 cycles. Therefore, it was confirmed that cycle stability was improved through dopamine coating. In addition, the anode materials were obtain a high capacity of 576 mAh/g at 5 C and a capacity recovery of 99.9% at 0.1 C/0.1 C.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.1
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• pp.43-49
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• 2023

This study reports on the preparation of sodium caseinate-cardanol (CasNa/CL)-based papers coated with different amounts of bentonite (BN) for use as a sustainable packaging material. Their chemical and morphological structures, mechanical properties, water vapor permeability, surface properties, and antioxidant activity of coated papers was assessed as a function of the BN content. The drying of the CasNa/CL coated papers led to the formation of pinholes on their surfaces owing to the presence of trapped water resulting from the difference in the drying rate between the external surface and the inside of the coated layers. Increasing the BN content reduced the pinholes on surface of CasNa/CL/BN coated papers and highly decreased the water vapor transmittance rate of the papers from 387.3±1.9 g/m²·day to 269.25±4.5 g/m²·day. Free radical scavenging assays indicated the addition of CL to the CasNa exhibited the antioxidant activity and antioxidant activity of CasNa/CL/BN did not changed as increase of BN contents. The improved water vapor barrier property and antioxidant activity of CasNa/CL/BN coated papers can be promised for various packaging applications.

• Korean Journal of Heritage: History & Science
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• v.37
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• pp.285-307
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• 2004

Synthesize and examine petrological characteristic and geochemical characteristic by weathering formation of rock and progress of weathering laying stress on stone cultural properties of Unjusa temple of Chonnam Hwasun county site in this research. Examine closely weathering element that influence mechanical, chemical, mineralogical and physical weathering of rocks that accomplish stone cultural properties and these do quantification, wish to utilize by a basic knowledge for conservation scientific research of stone cultural properties by these result. Enforced component analysis of rock and mineralogical survey about 18 samples (pyroclastic tuff; 7, ash tuff; 4, granite ; 4, granitic gneiss; 3) all to search petrological characteristic and geochemical characteristic by weathering of Unjusa temple precinct stone cultural properties and recorded deterioration degree about each stone cultural properties observing naked eye. Major rock that constitution Unjusa temple one great geological features has strike of N30-40W and dip of 10-20NE being pyroclastic tuff. This pyroclastic tuff is ranging very extensively laying center on Unjusa temple and stone cultural properties of precinct is modeled by this pyroclastic tuff. Stone cultural propertieses of present Unjusa temple precinct are accomplishing structural imbalance with serious crack, and because weathering of rock with serious biological pollution is gone fairly, rubble break away and weathering and deterioration phenomenon such as fall off of a particle of mineral are appearing extremely. Also, a piece of iron and cement mortar of stone cultural properties everywhere are forming precipitate of reddish brown and light gray being oxidized. About these stone cultural properties, most stone cultural propertieses show SD(severe damage) to MD(moderate damage) as result that record Deterioration degree. X-ray diffraction analysis result samples of each rock are consisted of mineral of quartz, orthoclase,plagioclase, calcite, magnetite etc. Quartz and feldspar alterated extremely in a microscopic analysis, and biotite that show crystalline form of anhedral shows state that become chloritization that is secondary weathering mineral being weathered. Also, see that show iron precipitate of reddish brown to crack zone of tuff everywhere preview rock that weathering is gone deep. Tuffs that accomplish stone cultural properties of study area is illustrated to field of Subalkaline and Peraluminous, $SiO_2$(wt.%) extent of samples pyroclastic tuff 70.08-73.69, ash tuff extent of 70.26-78.42 show. In calculate Chemical Index of Alteration(CIA) and Weathering Potential Index(WPI) about major elements extent of CIA pyroclastic tuff 55.05-60.75, ash tuff 52.10-58.70, granite 49.49-51.06 granitic gneiss shows value of 53.25-67.14 and these have high value gneiss and tuffs. WPI previews that is see as thing which is illustrated being approximated in 0 lines and 0 lines low samples of tuffs and gneiss is receiving esaily weathering process as appear in CIA. As clay mineral of smectite, zeolite that is secondary weathering produce of rock as result that pick powdering of rock and clothing material of stone cultural properties observed by scanning electron micrographs (SEM). And roots of lichen and spore of hyphae that is weathering element are observed together. This rock deep organism being coating to add mechanical weathering process of stone cultural properties do, and is assumed that change the clay mineral is gone fairly in stone cultural properties with these. As the weathering of rocks is under a serious condition, the damage by the natural environment such as rain, wind, trees and the ground is accelerated. As a counter-measure, the first necessary thing is to build the ground environment about protecting water invasion by making the drainage and checking the surrounding environment. The second thing are building hardening and extirpation process that strengthens the rock, dealing biologically by reducing lichens, and sticking crevice part restoration using synthetic resin. Moreover, it is assumed to be desirable to build the protection facility that can block wind, sunlight, and rain which are the cause of the weathering, and that goes well with the surrounding environment.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.04a
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• pp.9-10
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• 2000

An important business-field of world-wide steel-industry is the coating of thin metal-sheets with zinc, zinc-aluminum and aluminum based materials. These products mostly go into automotive industry. in particular for the car-body. into building and construction industry as well as household appliances. Due to mass-production, the processing is done in large continuously operating plants where the mostly cold-rolled metal-strip as the substrate is handled in coils up to 40 tons unwind before and rolled up again after passing the processing plant which includes cleaning, annealing, hot-dip galvanizing / aluminizing and chemical treatment. In the liquid Zn, Zn-AI, AI-Zn and AI-Si bathes a combined action of corrosion and wear under high temperature and high stress onto the transfer components (rolls) accounts for major economic losses. Most critical here are the bearing systems of these rolls operating in the liquid system. Rolls in liquid system can not be avoided as they are needed to transfer the steel-strip into and out of the crucible. Since several years, ceramic roller bearings are tested here [1.2], however, in particular due to uncontrollable Slag-impurities within the hot bath [3], slide bearings are still expected to be of a higher potential [4]. The today's state of the art is the application of slide bearings based on Stellite\ulcorneragainst Stellite which is in general a 50-60 wt% Co-matrix with incorporated Cr- and W-carbides and other composites. Indeed Stellite is used as the bearing-material as of it's chemical properties (does not go into solution), the physical properties in particular with poor lubricating properties are not satisfying at all. To increase the Sliding behavior in the bearing system, about 0.15-0.2 wt% of lead has been added into the hot-bath in the past. Due to environmental regulations. this had to be reduced dramatically_ This together with the heavily increasing production rates expressed by increased velocity of the substrate-steel-band up to 200 m/min and increased tractate power up to 10 tons in modern plants. leads to life times of the bearings of a few up to several days only. To improve this situation. the Mechanical Alloying (MA) TeChnique [5.6.7.8] is used to prOduce advanced Stellite-based bearing materials. A lubricating phase is introduced into Stellite-powder-material by MA, the composite-powder-particles are coated by High Energy Milling (HEM) in order to produce bearing-bushes of approximately 12 kg by Sintering, Liquid Phase Sintering (LPS) and Hot Isostatic Pressing (HIP). The chemical and physical behavior of samples as well as the bearing systems in the hot galvanizing / aluminizing plant are discussed. DependenCies like lubricant material and composite, LPS-binder and composite, particle shape and PM-route with respect to achievable density. (temperature--) shock-reSistibility and corrosive-wear behavior will be described. The materials are characterized by particle size analysis (laser diffraction), scanning electron microscopy and X-ray diffraction. corrosive-wear behavior is determined using a special cylinder-in-bush apparatus (CIBA) as well as field-test in real production condition. Part I of this work describes the initial testing phase where different sample materials are produced, characterized, consolidated and tested in the CIBA under a common AI-Zn-system. The results are discussed and the material-system for the large components to be produced for the field test in real production condition is decided. Outlook: Part II of this work will describe the field test in a hot-dip-galvanizing/aluminizing plant of the mechanically alloyed bearing bushes under aluminum-rich liquid metal. Alter testing, the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed. Part III of this project will describe a second initial testing phase where the won results of part 1+11 will be transferred to the AI-Si system. Part IV of this project will describe the field test in a hot-dip-aluminizing plant of the mechanically alloyed bearing bushes under aluminum liquid metal. After testing. the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.3
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• pp.33-38
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• 2021

Recently, rollable and foldable displays are attracting great attention in the flexible display market due to their excellent form factor. To predict and prevent the mechanical failure of the display panels, it is essential to accurately understand the mechanical properties of brittle SiN_x thin films, which have been used as an insulating film in flexible displays. In this study, tensile properties of the ~130 nm- and ~320 nm-thick SiN_x thin films were successfully measured by coating a ~190 nm-thick organic nano-support-layer (PMMA, PS, P3HT) on the fragile SiN_x thin films and stretching the films as a bilayer state. Young's modulus values of the ~130 nm and ~320 nm SiN_x thin films fabricated through the controlled chamber pressure and deposition power (A: 1250 mTorr, 450 W/B: 1000 mTorr, 600 W/C: 750 mTorr, 700 W) were calculated as A: 76.6±3.5, B: 85.8±4.6, C: 117.4±6.5 GPa and A: 100.1±12.9, B: 117.9±9.7, C: 159.6 GPa, respectively. As a result, Young's modulus of ~320 nm SiN_x thin films fabricated through the same deposition condition increased compared to the ~130 nm SiN_x thin films. The tensile testing method using the organic nano-support-layer was effective in the precise measurement of the mechanical properties of the brittle thin films. The method developed in this study can contribute to the robust design of the rollable and foldable displays by enabling quantitative measurement of mechanical properties of fragile thin films for flexible displays.

• Clean Technology
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• v.20 no.3
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• pp.232-240
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• 2014

The significance of thermoplastic polyolefin polypropylene (PP) lies in its potential to replace polyvinyl chloride (PVC), the most widely used material for automobile interiors (door trim, dash board), which discharges harmful compounds in certain conditions. Another benefit of PP (0.855 amorphous - 0.946 crystalline $g/cm^3$) is its low density compared to that of PVC ($1.1-1.45g/cm^3$), which reduces vehicle weight. Market demand for eco-friendly water-based adhesive/coating material is rising significantly as a substitute for solvent-based adhesive/coating material which emits VOC and causes harmful working conditions. Under such context, in this study, a series of eco-friendly waterborne polyurethane-urea primer (a paint product that allows finishing paint to adhere much better than if it were used alone) for hydrophobic PP were prepared from different mix of DMPA content, NCO/OH molar ratio, various wt% of silicone diol and various soft segment content, among which DMPA of 21 mole %, NCO/OH molar ratio of 1.2, modified silicone diol of 5 wt% and soft segment content of 73 wt% led to good adhesion strength. Additionally, the incorporation of optimum content of additives (0.5 wt% dispersing agent, 0.5 wt% levelling agent, 1.5 wt% antifoaming agent, 3.0 wt% matting agent) into the optimum waterborne polyurethane-urea also enabled good stability, levelling, antifoaming and non-glossy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.618-626
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• 2019

Stem cell therapy is not expected to bestow any therapeutic benefit because of the low engraftment rates after transplantation.Various cell-carrying scaffolds have been developed in order to overcome this problem. When the scaffold is formed by 3-dimensional (3D) printing, it is possible to create various shapes of scaffolds for specific regions of injury. At the same time, scaffolds provide stem cells as therapeutic-agents and mechanically support an injured region. PCL is not only cost effective, but it is also a widely used material for 3D printing. Therefore, rapid and economical technology development can be achieved when PCL is printed and used as a cell carrier. Yet PCL materials do not perform well as cell carriers, and only a few cells survive on the PCL surface. In this study, we tried to determine the conditions that maximize the cell-loading capacity on the PCL surface to overcome this issue. By applying a plasma treated condition and then collagen coating known to improve the cell loading capacity, it was confirmed that the 3% collagen coating after plasma treatment showed the best cell engraftment capacity during 72 hours after cell loading. By applying the spheroid cell culture method and scaffold structure change, which can affect the cell loading ability, the spheroid cell culture methods vastly improved cell engraftment, and the scaffold structure did not affect the cell engraftment properties. We will conduct further experiments using PCL material as a cell carrier and as based the excellent results of this study.

• Journal of the Korean Wood Science and Technology
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• v.38 no.4
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• pp.333-340
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• 2010

The Korean Dendropanax lacquer, made from a natural resinous sap from Dendropanax orbifera Lev., was used as a golden and transparent varnish for the traditional artifacts (armor uits, helmets, arrowheads, etc.) to make them be brilliant golden color. The cured film of the acquer has excellent protective properties such as weatherability, water resistance, and nticorrosive. But, one of disadvantages is that takes a long time and much energy to fulfill curing the lacquer. The chemical constituents of the lacquer contained conjugated diene compounds s the photopolymerizable monomers. These monomers easily polymerized in sunlight to form olden-colored, hard-coating films in a short time. Photooxidation may be one of the most mportant reactions in the chemistry of the lacquer. Although the Korean Dendropanax Lacquer hould be dried to a thoroughly dry stage to achieve optimal film properties, curing with elevated emperatures may be required for the protracted curing time at atmospheric temperature. So we ntended to accelerate the curing rate of the lacquer by dual curing of thermal and radiation uring. The effect of thermal initiator on the thermal curing reaction was evaluated by monitoring he changes in double bond peak with FT-IR. Then the curing rate of the lacquer blended with hermal initiator and photoinitiator together was measured during dual curing using a RPT with V spot curing machine. Thermal initiator not only accelerated the curing rate but also improved he physical property. And the curing rate of the Korean Dendropanax lacquer was improved by ual curing method of thermal and UV curing. According to these results, the application area of he Korean Dendropanax lacquer could be expanded to surface coatings for electronic devices uch as mobile phones or electronics.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.527-533
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• 2006

Spinel $LiNi_xMn_{2-x}O_4$ thin films were synthesized up to x = 0.9 by a sol-gel method employing spin-coating. The Ni-substituted films were found to maintain cubic structure at low x but to exhibit tetragonal structure for $x{\geq}0.6$. Such cubic-tetragonal phase transition indicates that $Ni^{3+}(d7)$ ions with low-spin $(t_{2g}^6,e_g^1)$ state occupy the octahedral sites of the compound, thus being subject to the Jahn-Teller distortion. By x-ray photoelectron spectroscopy both $Ni^{2+}$ and $Ni^{3+}$ ions were detected. Optical properties of the $LiNi_xMn_{2-x}O_4$ films were investigated by spectroscopic ellipsometry (SE) in the visible?ultraviolet range. The measured dielectric function spectra by SE mainly consist of broad absorption structures attributed to charge-transfer (CT) transitions, $O^{2-}(2p){\rightarrow}Mn^{4+}(3d)$ for 1.9 $(t_{2g})$ and $2.8{\sim}3.0$ eV $(e_g)$ structures and $O^{2-}(2p){\rightarrow}Mn^{3+}(3d)$ for 2.3 $(t_{2g})$ and $3.4{\sim}3.6$ eV $(e_g)$ structures. Also, sharp absorption structures were observed at about 1.6, 1.7, and 1.9 eV, interpreted as due to d-d crystal-field transitions within the octahedral $Mn^{3+}$ ion. The strengths of these absorption structures are reduced by the Ni substitution. Rapid reduction of the CT transition strength involving the eg states for x = 0.6 is attributed to the reduced wavefunction overlap between the $e_g$ and the $O^{2-}(2p)$ states due to the tetragonal extension of the lattice constant by the Jahn-Teller effect.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.113-117
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• 2016

Recently, hydrogen is regarded as important energy in the future, because it is clean and renewable. The photoelectrochemical (PEC) system, which produce hydrogen using water splitting by solar energy, is one of the most promising energy systems because it has abundant energy sources and good theoretical efficiency. GaN has recently been regarded as suitable photoelectrode that could be used to split water to generate hydrogen without extra bias because its band edge position include water redox potential ($V_{redox}=1.23$ vs. SHE). GaN also shows considerable corrosion resistance in aqueous solutions and it is possible to control its properties, such as structure, band gap, and catalyst characteristics, in order to improve solar energy conversion efficiency. But, even if the band edge position of GaN make PEC reaction facilitate without bias, the overpotential of oxygen evolution reaction could reduce the efficiency of system. One of the ways to decrease overpotential is introduction of co-catalyst on photoelectrode. In this paper, we will investigate the effect of manganese dioxide ($MnO_2$) as a co-catalyst. $MnO_2$ particles were dispersed on GaN photoelectrode by spincoater and analyzed properties of the PEC system using potentiostat (PARSTAT4000). After coating $MnO_2$, the flat-band potential ($V_{fb}$) and the onset voltage ($V_{onset}$) were moved negatively by 0.195 V and 0.116 V, respectively. The photocurrent density increased on $MnO_2$ coated sample and time dependence was also improved. These results showed $MnO_2$ has an effect as a co-catalyst and it would enhance the efficiency of overall PEC system.