• Composites Research
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• 제22권4호
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• pp.33-40
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• 2009

유리섬유/에폭시 복합재료로 피막한 판유리의 표변파괴거동에 대한 섬유방향효과를 미소강구 충격실험을 통해 연구했다. 본 연구에서는 단순소다유리판(soda-lime glass plates), 일방향 유리섬유/에폭시박막 (glass/epoxy lamina ply)을 1층 및 2층 접착, 직교형 유리섬유/에폭시 박막 (2층)을 접착한 4종류의 시편을 사용하였다. 유리판 배면에 스트레인게이지를 부착하여 충격중의 최대 응력과 흡수파괴에너지를 측정하였다. 피막없는 판유리의 경우 충격속도 증가에 따라 링균열, 콘균열, 레이디얼 균열이 충격표면부에서 발생하였다. 복합재료 박막으로 피막한 결과, 소다유리판의 균열은 현저히 감소하였으며 섬유층과 판유리사이의 박리 및 소성변형영역의 방향은 섬유방향으로 진행했다. 최대응력과 흡수파괴에너지를 이용하여 구한 충격 표면파괴지수는 표면저항의 효과적인 평가지수로서 사용될 수 있었다.

• The Korean Journal of Ceramics
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• 제3권2호
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• pp.105-109
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• 1997

The effects of surface conditions of the C-2 cemented carbide substrate on the adhesion of diamond film were investigated. The substrates were pretreated for different times with Murakami's reagent and then the acid solution of an H2SO4-H2O2. The adhesion strength was estimated by a peeling area around the Rockwell-A indentation. The cutting performance of the diamond-coated tools was evaluated by measuring flank wears in dry turning of Al-17% Si alloy. The morphology of deposited diamond crystallites was dominated by (111) and (220) surfaces with a cubooctahedral shape. The diamond film quality was hardly affected by the surface conditions of the substrate. The variation of tool life with longer substrate etching times resulted from a compromies between the increase of film adhesion at the interface and the decrease of toughness at the substrate surface. The coated tools were mainly deteriorated by chipping and flaking of the diamond film form a lock of adhesion strength, differently from the wear phenomena of PCD tools.

• Nuclear Engineering and Technology
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• 제38권1호
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• pp.61-68
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• 2006

CHF characteristics of nano- fluids were investigated with different volumetric concentrations of $TiO_2$ nanoparticles. Pool boiling experiments indicated that the application of nano-fluids, instead of pure water, as a cooling liquid significantly increased the CHF. SEM (scanning electron microscope) observations subsequent to the pool boiling experiments revealed that nanoparticles were coated on the heating surface during pool boiling of nano-fluids. In order to investigate the roles of nanoparticles in CHF enhancement ofb nano-fluids, pool boiling experiments were performed using (a) a nanoparticle-coated heater, prepared by pool boiling of nano-fluids, immersed in pure water and (b) a nanoparticle-coated heater immersed in nano-fluids. The results demonstrated two different roles of nanoparticles in CHF enhancement using nano-fluids: the effect of nanoparticles coated on the heater surface and the effect of nanoparticles suspended in nano- fluids.

• 한국인쇄학회지
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• 제15권2호
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• pp.25-40
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• 1997

This research was carried out to investigated the effect of base paper and latex binder on printability and obtical properties of coated paper. Especially, it examined the effect of th pH of vase paper surface and functional groups of latices on the interactions between coating color components and on the structure of coated layer. It was found that the behavior of coating color containing amphoeric latex depends on the pH in the boundary region between coating color and base paper. Thus, the coating color formulated with amphoteric latex formed bulky coating layer by inducing stronger interaction between paper surface and coating components than the coating color with anionic latex. The coated paper with amphoteric latex showed better optical properties (i.e.gloss and optical) and printability (i.e. ink receptivity, wet ink receptivity, and ink set off) than the conventional anionic latex in the acidic and alkaline paper. However, dry pick strength of the coated paper was less decreased. This result indicated that amphoteric latex could also be applied practically to the alkaline paper.

• Tribology and Lubricants
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• 제15권1호
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• pp.29-38
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• 1999

In recent years, the tribological behavior of coated ceramic material has been the issue of much interest. Particularly, the understanding of the tribological performance of thin film under light load is important for its potential in applications of MEMS. The friction and wear behavior of ceramic material that occur at light load depends on several factors such as surface roughness, contact area and material properties. In this work, the tribological behavior of coated silicon under light load and low speed was investigated. Particularly, the effects of coated materials, humidity and undulated surface were also studied. The results show that the effect of humidity on fiction was influenced by the apparent area of contact between the two surfaces. Also both adhesive and abrasive wear occurred depending on the sliding condition. Finally, undulations on the silicon wafer were found to be effective in trapping wear particles and resulted in the reduction of friction.

• 한국표면공학회지
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• 제35권2호
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• pp.122-128
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• 2002

This study was conducted to synthesize the diamond like carbon films by plasma enhanced chemical vapor deposition (PECVD). The effects of gas composition on growth and mechanical properties of the films were investigated. A little amount of hydrogen or oxygen were added to base gas mixture of methane and argon. Methane dissociation and diamond like carbon nucleation were enhanced by installing negatively bias grid near substrate. The deposited films were indentified as hard diamond like carbon films by micro-Raman spectroscopy. The surface and fractured cross section of the films which were observed by scanning electron microscopy showed that film growth is very slow as about 0.3$\mu\textrm{m}$/hour, and relatively uniform with hydrogen addition. Vickers hardness of tungsten carbide (WC) cutting tool increased from about 1000 to 1600~1800 by deposition of DLC film, that of commercial TiN coated tool was about 1270. In cutting test of aluminum 6061 alloy, DLC coated cutting tool showed 1/3 or lower crater and flank wear than TiN coated or non-coated WC cutting tools.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.151-152
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• 2023

Lightweight aggregates has a dry specific gravity of 2.0 or less, which is lower than natural aggregates. Lightweght aggregate is efficient for weight reduction but has low compressive strength. In this study, EIS(electrochemical Impedance Spectroscopy) was used to confirm the ITZ(Interfacial Transition Zone) between the lightweight aggregate and cement paste according to the coated of blast furnace slag powder. As a result of EIS measurement, the correlation between ITZ characteristics and compressive strength was determined. The phase angle of EIS was different depending on the blast furnace slag powder coated of the lightweight aggregate. The surface-cotead lightweight aggregate was improved and the ITZ was strengthened.

• Journal of Periodontal and Implant Science
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• 제41권5호
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• pp.242-247
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• 2011

Purpose: The purpose of this study was to characterize the osseointegration of the fibronectin-coated implant surface. Methods: Sand-blasted, large-grit, acid-etched (SLA) surface implants, with or without a thin calcium phosphate and fibronectin coating, were placed in edentulous mandibles of dogs 8 weeks after extraction. All dogs were sacrificed forhistological and histomorphometric evaluation after 4- and 8-week healing periods. Results: All types of implants were clinically stable without any mobility. Although the bone-to-implant contact and bone density of the SLA implants coated with calcium phosphate (CaP)/fibronectin were lower than the uncoated SLA implants, there were no significant differences between the uncoated SLA surface group and the SLA surface coated with CaP/fibronectin group. Conclusions: Within the limits of this study, SLA surfaces coated with CaP/fibronectin were shown to have comparable bone-to-implant contact and bone density to uncoated SLA surfaces.

• Journal of Periodontal and Implant Science
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• 제40권6호
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• pp.276-282
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• 2010

Purpose: The present study was performed to evaluate the effect of erbium:yttrium-aluminium-garnet (Er:YAG) laser irradiation on the change of hydroxyapatite (HA)-coated implant surface microstructure according to the laser energy and the application time. Methods: The implant surface was irradiated by Er:YAG laser under combination condition using the laser energy of 100 mJ/pulse, 140 mJ/pulse and 180 mJ/pulse and application time of 1 minute, 1.5 minutes and 2 minutes. The specimens were examined by surface roughness evaluation and scanning electron microscopic observation. Results: In scanning electron microscope, HA-coated implant surface was not altered by Er:YAG laser irradiation under experimental condition on 100 mJ/pulse, 1 minute. Local areas with surface melting and cracks were founded on 100 mJ/pulse, 1.5 minutes and 2 minutes. One hundred forty mJ/pulse and 180 mJ/pulse group had surface melting and peeling area of HA particles, which condition was more severe depending on the increase of application time. Under all experimental condition, the difference of surface roughness value on implant surface was not statistically significant. Conclusions: Er:YAG laser on HA-coated implant surface is recommended to be irradiated below 100 mJ/pulse, 1 minute for detoxification of implant surface without surface alteration.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1483-1490
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• 2011

The protection effect of a $ZrO_2$ coating layer on a $LiCoO_2$ thin film was characterized. A wide and smooth $LiCoO_2$ thin film offers sufficient opportunity for careful observation of the reaction at the interface between cathode (coated and uncoated) and electrolyte. The formation of a $ZrO_2$ coating on a $LiCoO_2$ thin film was confirmed by secondary ion mass spectrometry. Scanning electron and atomic force microscopy were used to characterize the surface morphologies of coated and uncoated films before and after cycling. A $ZrO_2$-coated $LiCoO_2$ film showed a higher discharge capacity and rate capability than an uncoated film. This may be associated with a surface protection effect of the coating. The surface of a pristine film was damaged during cycling, whereas the coated film maintained a relatively clear surface under the same measurement conditions. This result clearly demonstrates the protection effect of a $ZrO_2$ coating on a $LiCoO_2$ thin film.