• 한국재료학회지
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• 제21권5호
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• pp.288-294
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• 2011

Simultaneous Ni and C codeposition by electrolysis was investigated with the aim of obtaining better corrosion resistivity and surface conductivity of a metallic bipolar plate for application in fuel cells and redox flow batteries. The carbon content in the Ni-C composite plate fell in a range of 9.2~26.2 at.% as the amount of carbon in the Ni Watt bath and the roughness of the composite were increased. The Ni-C composite with more than 21.6 at.% C content did not show uniformly dispersed carbon. It also displayed micro-sized defects such as cracks and crevices, which result in pitting or crevice corrosion. The corrosion resistance of the Ni-C composite in sulfuric acid is similar with that of pure Ni. Electrochemical test results such as passivation were not satisfactory; however, the Ni-C composite still displayed less than $10^{-4}$ $A/cm^2$ passivation current density. Passivation by an anodizing technique could yield better corrosion resistance in the Ni-C composite, approaching that of pure Ni plating. Surface resistivity of pure Ni after passivation was increased by about 8% compared to pure Ni. On the other hand, the surface resistivity of the Ni-C composite with 13 at.% C content was increased by only 1%. It can be confirmed that the metal plate electrodeposited Ni-C composite can be applied as a bipolar plate for fuel cells and redox flow batteries.

• 대한치과보철학회지
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• 제38권1호
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• pp.108-115
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• 2000

This study was designed to compare the effect of polishing on surface roughness of composite resin. We used Z100(3M) composite resin and placed the composite resin in the hole (4mm thick and 4mm in diameter) of vinyl plate and polymerized it under manufacturer's instructions. Samples were divided into 5 groups by polishing methods. Group 1 was control: resin was polymerized under glass plate, Group 2: resin was polymerized without any polishing procedure, Group 3: resin was polymerized with a polishing procedure of abrasive disc, Group 4: bonding agent was applyed in thin layer and polymerized on the polished polymerized resin surface. Group 5: resin was polymerized under transparent celluloid strip. The surface roughness of each specimen was measured with Sufacoder SEF-30D (Kosaka lab. Ltd) under 0.08mm cut off, 0.05mm/s stylus speed, ${\times}40$ horizontal magnification, ${\times}5000$ vertical magnification. The results were as follows : 1. Group 1 showed the most smooth surface in this study. 2. Group 3 showed more rough surface than Group 2. Considering the surface roughness, it would be better to make the shape completely before polymerize the resin. To finish and polish after the polymerization of resin makes less smooth surface. 3. When we use the transparent celluloid strip, minimum finishing procedures are recommended. Any polishing procedure could not recover the smooth resin surface of celluloid strip. 4. Application and polymerization of the thin layer of bonding agent on the polished surface showed the minimum surface smoothing effect.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.40-43
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• 1999

Electrochemical surface treatment of PAN-based carbon fibers in acidic electrolyte has been studied in increasing the surface functional groups on fiber surfaces for the improvement of fiber-matrix adhesion of the resulting composites. According to the FT-IR and XPS measurements, it reveals that the oxygen functional groups on fibers are largely influence on the composite mechanical behaviors, whereas the nitrogen functional groups are not affected in the system. In this work, a good correlation between surface functionality and mechanical properties is established.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.54-57
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• 2003

Since passenger cars require five wheels including a spare, the weight reduction of wheels without sacrificing performance is important. Recently, the structured components of cars made of steel are replaced by composites. plastics and other nonmetallic materials such as aluminum and magnesium for weight reduction. From these new tried materials are most promising due to their high specific stiffness and specific strength. The composites manufactured by resin transfer molding (RTM) process has not only low cost for the manufacturing but also reduces the lead time and development because the molds for RTM is easy to manufacture. In this work, composite wheels for passenger cars were designed and manufactured by RTM process. Since surface quality of wheels is important for passenger cars, the optimal stacking sequence for composite wheels was selected considering surface quality and mechanical properties. Also, the manufacturing method for the composite mold was depicted.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.441-446
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• 2000

Although the net-shape molding of composites is generally recommended, molded composites frequently required cutting or grinding due to the dimensional inaccuracy for precision machine elements. During the composite machining operations such as cutting and grinding, the temperature at the grinding area may increase beyond the allowed limit due to the low thermal conductivity of composites, which might degrade the matrix of composite. Therefore, in this work, the temperature at the grinding point during surface grinding of carbon fiber epoxy composite was measured. The grinding temperature and surface roughness were also measured to investigate the surface grinding characteristics of the composited. The experiments were performed both under dry and wet grinding conditions with respect to cutting speed, feed speed, depth of cut and stacking angle. From the experimental investigation, the optimal conditions for the composite plain grinding were suggested.

• 한국생산제조학회지
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• 제9권6호
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• pp.65-70
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• 2000

Although the net-shape molding of composites is generally recommended, molded composites frequently requires cutting or grinding due to the dimensional inaccuracy for precision machine elements. During the composite machining operations such as cutting and grinding, the temperature at the grinding area may increase beyond the allowed limit due to the low thermal conductivity of composites, which might degrade the matrix of composite. Therefore, in this work, the temperature at the grinding point during surface grinding of carbon fiber epoxy composite was measured. The grinding temperature and surface roughness were also measured to investigate the surface grinding characteristics of the composites. The experiments were performed both under dry and wet grinding conditions with respect to cutting speed, feed speed, depth of cut and stacking angle. From the experimental investigation, the optimal conditions for the composite surface grinding were suggested.

• 한국표면공학회지
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• 제36권1호
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• pp.85-88
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• 2003

By utilization of preceramic polymer of polymethylsiloxane (PMS), a $MoSi_2$SiOC/SiC ceramic composite was fabricated. The prepared composite displayed superior high temperature oxidation resistance by forming $SiO_2$ on the surface. The thin $SiO_2$ layer had some surface cracks, but they had not adversely deteriorated the oxidation resistance. The composite fabrication method employed in this study can be applied to protect any possible substrate material from aggressive oxidative attack, if the composite were coated on the substrate material.

• Steel and Composite Structures
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• 제25권2호
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• pp.209-216
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• 2017

In this paper, the analysis of the behavior of surface cracks in finite-thickness plates repaired with a Boron/Epoxy composite patch is investigated using three-dimensional finite element methods. The stress intensity factor at the crack-front was used as the fracture criteria. Using the Ansys Parametric Design Language (APDL), the stress intensities at the internal and external positions of repaired surface crack were compared. The effects of the mechanical and geometrical properties of the adhesive layer and the composite patch on the variation of the stress intensity factor at the crack-front were examined.

• 열처리공학회지
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• 제28권6호
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• pp.315-321
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• 2015

Friction stir processing (FSP) was applied to fabricate AZ31/CNT (Carbon Nano Tube) surface composite for improvement of surface hardness of AZ31 Mg-based alloy. The effects of traverse speed of rotating tool and volume fraction of CNT (i.e., groove depth of 3 mm and 4 mm) on the soundness and hardness of the composite layer were investigated. Multi-walled CNTs were fully filled in a machined groove and stirring tool was rotated at the speed of 1400 rpm. Only under the tool traverse speed of 25 mm/min for the specimen with a groove depth of 3 mm, surface composite layer with no defect was successfully produced. Increased hardness of about 35% was observed in the composite layer.

• The Journal of Advanced Prosthodontics
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• 제8권4호
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• pp.267-274
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• 2016

PURPOSE. This study aimed to evaluate the effect of surface treatments on bond strength of indirect composite material (Tescera Indirect Composite System) to monolithic zirconia (inCoris TZI). MATERIALS AND METHODS. Partially stabilized monolithic zirconia blocks were cut into with 2.0 mm thickness. Sintered zirconia specimens were divided into different surface treatment groups: no treatment (control), sandblasting, glaze layer & hydrofluoric acid application, and sandblasting + glaze layer & hydrofluoric acid application. The indirect composite material was applied to the surface of the monolithic zirconia specimens. Shear bond strength value of each specimen was evaluated after thermocycling. The fractured surface of each specimen was examined with a stereomicroscope and a scanning electron microscope to assess the failure types. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey LSD tests (${\alpha}$=.05). RESULTS. Bond strength was significantly lower in untreated specimens than in sandblasted specimens (P<.05). No difference between the glaze layer and hydrofluoric acid application treated groups were observed. However, bond strength for these groups were significantly higher as compared with the other two groups (P<.05). CONCLUSION. Combined use of glaze layer & hydrofluoric acid application and silanization are reliable for strong and durable bonding between indirect composite material and monolithic zirconia.