• Proceedings of the Materials Research Society of Korea Conference
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• 2001.11a
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• pp.61-61
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• 2001

• Proceedings of the Korean Vacuum Society Conference
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• 2002.06a
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• pp.118-118
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• 2002

• Electrical & Electronic Materials
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• v.10 no.3
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• pp.217-225
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• 1997

In this study, the PVDF organic thin film was fabricated by the physical vapor deposition method to be dry-process. The distance of heat source and substrate was 5[cm] and the temperature of substrate was 30[.deg. C], when the pressure had reached 2.0 x 10$^{-5}$ [Torr], the temperature of heat source was reached to 285[.deg. C] to heat at 6-8[.deg. C/min] rate, the shutter was opened and deposition was started. TG-DTA(Thermogravimetric-Differential Thermal Analysis) spectrum of PVDF pellets showed that endothermic peak arose at 170[.deg. C] and exothermic peak at 524[.deg. C], but that of thin PVDF film showed that endothermic peak arose at 145[.deg. C] and exothermic peak at 443[.deg C]. The current density was increased linearly with increasing voltage but increased nonlinearly with higher electric field than 250[kV/cm] and activation energy was about 0.667[eV] at the temperature of 30-90[.deg. C].

• Journal of the Korean Ceramic Society
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• v.43 no.2 s.285
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• pp.85-91
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• 2006

Electron Beam Physical Vapor Deposition (EB-PVD) was applied to fabricate a thin film YSZ electrolyte with large area on the porous NiO-YSZ anode substrate. Microstructural and thermal stability of the as-deposited electrolyte film was investigated via SEM and XRD analysis. In order to obtain an optimized YSZ film with high stability, both temperature and surface roughness of substrate were varied. A structurally homogeneous YSZ film with large area of $12\times12\;cm^2$ and high thermal stability up to $900^{\circ}C$ was fabricated at the substrate temperature of $T_s/T_m$ higher than 0.4. The smoother surface was proved to give the better film quality. Precise control of heating and cooling rate of the anode substrate was necessary to obtain a very dense YSZ electrolyte with high thermal stability, which affords to survive after post heat treatment for fabrication a cathode layer on it as well as after long time operation of solid oxide fuel cell at high temperature.

• Journal of Ceramic Processing Research
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• v.21
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• pp.47-52
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• 2020

Graphene was synthesized using rapid thermal chemical vapor deposition (RT-CVD) equipment designed to produce largearea graphene at high speed. The effects of methane (CH₄), argon (Ar), and hydrogen (H₂) gases were investigated between 800 ℃ and 1,000 ℃ during heating and cooling in the graphene synthesis process. The findings reveal that multilayer domains increased due to hydrogen pretreatment with increase in temperature. Furthermore, when pretreated with the same gas, it was confirmed that the post-argon-treated sample cooled from 1,000 ℃ to 800 ℃ had a higher I_D/I_G value than that of the other samples. This result was consistent with the sheet resistance properties of graphene. The sample prepared in methane atmosphere maintained during both the pre-treatment and post-treatment demonstrated the lowest sheet resistance of 787.49 Ω/sq. Maintaining the methane gas atmosphere in the high-temperature region during graphene synthesis by RT-CVD reduced the defects and improved the electrical property.

• Journal of the Korean institute of surface engineering
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• v.39 no.4
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• pp.147-152
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• 2006

Failure mechanisms of electron beam physical vapor deposited thermal barrier coatings(EB-PVD TBCs) that occur during thermal cyclic oxidation were investigated. The investigations include microstructural degradation of NiCrAIY bond coat, thermally grown oxides(TGOs) along the ceramic top coat-substrate interface and fracture path within TBCs. The microstructural degradation of the bond coat during cyclic oxidation created Al depleted zones, resulting in reduction of NiAl and ${\gamma}$-Ni solid solution phase. It was observed that the fracture took placed primarily within the TGOs or at the interfaces between TGOs and bond coat.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.252.2-252.2
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• 2013

ZnO nanostructures have a lot of interest for decades due to its varied applications such as light-emitting devices, power generators, solar cells, and sensing devices etc. To get the high performance of these devices, the factors of nanostructure geometry, spacing, and alignment are important. So, Patterning of vertically- aligned ZnO nanowires are currently attractive. However, many of ZnO nanowire or nanorod fabrication methods are needs high temperature, such vapor phase transport process, metal-organic chemical vapor deposition (MOCVD), metal-organic vapor phase epitaxy, thermal evaporation, pulse laser deposition and thermal chemical vapor deposition. While hydrothermal process has great advantages-low temperature (less than $100^{\circ}C$), simple steps, short time consuming, without catalyst, and relatively ease to control than as mentioned various methods. In this work, we investigate the dependence of ZnO nanowire alignment and morphology on si substrate using of nanosphere template with various precursor concentration and components via hydrothermal process. The brief experimental scheme is as follow. First synthesized ZnO seed solution was spun coated on to cleaned Si substrate, and then annealed $350^{\circ}C$ for 1h in the furnace. Second, 200nm sized close-packed nanospheres were formed on the seed layer-coated substrate by using of gas-liquid-solid interfacial self-assembly method and drying in vaccum desicator for about a day to enhance the adhesion between seed layer and nanospheres. After that, zinc oxide nanowires were synthesized using a low temperature hydrothermal method based on alkali solution. The specimens were immersed upside down in the autoclave bath to prevent some precipitates which formed and covered on the surface. The hydrothermal conditions such as growth temperature, growth time, solution concentration, and additives are variously performed to optimize the morphologies of nanowire. To characterize the crystal structure of seed layer and nanowires, morphology, and optical properties, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and photoluminescence (PL) studies were investigated.

• Journal of the Korean institute of surface engineering
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• v.46 no.6
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• pp.258-263
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• 2013

4 mol% Yttria-stabilized zirconia (4YSZ) coatings are fabricated by Air Plasma Spray (APS) and Electron Beam Physical Vapor Deposition (EB-PVD) with top coating of thermal barrier coating (TBC). NiCrAlY based bond coat is prepared as 150 ${\mu}m$ thickness by conventional APS (Air Plasma Spray) method on the NiCrCoAl alloy substrate before deposition of top coating. Each 4YSZ top coating shows different tribological behaviors based on the inherent layer structures. 4YSZ by APS which has splat-stacked structure shows lower friction coefficient but higher wear rate than 4YSZ by EB-PVD which has columnar structure. For 4YSZ by APS, such results are expected due to the sliding wear accompanied with local delamination of splats.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.362-362
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• 2012

Graphene-based materials have been gaining the unprecedented academic and industrial applications, due to the unique charge transport as a new kind of 2-dimensional materials. The applications incorporate electronic devices, nonvolatile memories, batteries, chemical sensors, etc. based on the electrical, mechanical, structural, optical, and chemical features newly reported. The current work employs thermal chemical vapor deposition involving H2 and CH4, in order to synthesize the 2-dimensional graphene materials. The qualitative/quantitative characterizations of the synthesized graphene materials are evaluated using Raman spectroscopy and Hall Measurements, In particular, the effect of processing variables is systematically investigated on the formation of graphene materials through statistical design of experiments. The optimized graphene materials will be attempted towards the potential applications to flat-panel displays.

• Journal of the Korean institute of surface engineering
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• v.46 no.4
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• pp.175-180
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• 2013

Carbon nanofilaments (CNFs) could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under thermal chemical vapor deposition system. Ni powders were used as the catalyst for the formation of the CNFs. During the initial deposition stage, the initiation of the CNFs on the Ni catalyst was investigated. The geometries of the as-grown CNFs on Ni catalyst were strongly dependent on the size and/or the shape of Ni catalyst. Small size catalyst (<150 nm in diameter) gives rise to the unidirectional growth of the CNFs. On the other hand, large size catalyst (150~500 nm), the bidirectional growth of the CNFs could be observed. Particularly, the well faceted parallelogram-shaped Ni catalyst could give rise to the bidirectional growth of the CNFs having the symmetrically opposite direction. Eventually, these bidirectional growths of CNFs were understood to form the well-developed carbon microcoils (CMCs). Based on these results, the optimal shape and the size of the Ni catalyst to form the CMCs were discussed.