• Journal of the Korean Vacuum Society
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• v.13 no.4
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• pp.175-181
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• 2004

We investigated the stability of the DLC film coated on 304 stainless steel substrate by Radio frequency assisted chemical vapor deposition method. Fracture and spallation behaviour of the coating was observed during micro-tensile test of the fil $m_strate composite. As the tensile deformation progressed, the cracks of the film were observed in the perpendicular direction to the tensile axis. Further deformation resulted in the plastic deformation with $45^{\circ}$ slip bands on the substrate surface. Spallation of the film occurred with the plastic deformation, which was initiated at the cracks of the film and was aligned along the slip directions. We found that both the cracking and the spallation behaviors are strongly dependent on the pre-treatment condition, such as Ar plasma pre-treatment. The spallation of the film was considerably suppressed in an optimized condition of the substrate cleaning by Ar glow discharge. We observed the improved stability with increasing duration of Ar plasma pre-treatment.nt.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.148.2-148.2
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• 2013

We prepared hydrophobic PDMS-coated porous silica as pre-concentration adsorbent for chemical warfare agents (CWAs). Since CWAs can be harmful to human even with a small amount, detecting low-concentration CWAs has been attracting attention in defense development. Porous silica is one of the promising candidates for CWAs pre-concentration adsorbent since it is thermally stable and its surface area is sufficiently high. A drawback of silica is that adsorption of CWAs can be significantly reduced due to competitive adsorption with water molecule in air since silica is quite hydrophilic. In order to solve this problem, hydrophobic polydimethylsiloxane (PDMS) thin film was deposited on silica. Adsorption and desorption of chemical warfare agent (CWA) simulants (Dimethylmethylphosphonate, DMMP and Dipropylene Glycol Methyl Ether, DPGEM) on bare and PDMS-coated silica were studied using temperature programed desorption (TPD) with and without co-exposing of water vapor. Without exposure of water vapor, desorbed amount of DMMP from PDMS-coated silica was twice larger than that from bare silica. When the samples were exposed to DMMP and water vapor at the same time, no DMMP was desorbed from bare silica due to competitive adsorption with water. On the other hand, desorbed DMMP was detected from PDMS-coated silica with reduced amount compared to that from the sample without water vapor exposure. Adsorption and desorption of DPGME with and without water vapor exposing was also investigated. In case of bare silica, all the adsorbed DPGME was decomposed during the heating process whereas molecular DPGME was observed on PDMS-coated silica. In summary, we showed that hydrophobic PDMS-coating can enhance the adsorption selectivity toward DMMP under humid condition and PDMS-coating also can have positive effect on molecular desorption of DPGME. Therefore we propose PDMS-coated silica could be an adequate adsorbent for CWAs pre-concentration under practical condition.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.3
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• pp.274-283
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• 2014

Swelling of the heat-treated netting for gillnet was estimated through the netting height in square acrylic tank. Experimental Nylon netting and PBSAT netting were heat-treated by using the high-degree vacuum method in hot water after net making. Heat-treatment temperatures were conducted with Nylon netting $105^{\circ}C$ and PBSAT netting $62^{\circ}C$, $65^{\circ}C$, $66^{\circ}C$, $67^{\circ}C$. The swelling measurement method of a netting using the square tank was capable of the reduction measurement errors comparing with measurement methods of a mesh inner angle and the shortening rate of a mesh size. In addition, this method was available to comparison evaluation for each netting more easily. Wet type heat-treatment apparatus with high-degree vacuum was shown higher $7{\sim}8^{\circ}C$ inner side temperature than a setting temperature. The tensile strength and elongation of Nylon netting and PBSAT netting were shown higher wet condition than dry condition. The tensile strengths of PBSAT monofilaments in dry and wet condition were sharply decreased at heat-treatment temp. $75^{\circ}C$ than heat-treatment temp. $74^{\circ}C$.

• Tribology and Lubricants
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• v.37 no.6
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• pp.203-207
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• 2021

This study presents the development of dielectric constant sensors to measure lubricant properties. The lubricant oil sensor is used to measure oil properties and machine conditions. Various condition monitoring methods are applied to diagnose machine conditions. Machine condition monitoring using oil sensors has advantage over other machine condition monitoring methods. The fault conditions can be noticed at the early stages by the detection of wear particles using oil sensors. Therefore, it provides an early warning in the failure procedure. A variety of oil sensors are applied to check the machine condition. Among all oil sensors, only one sensor can measure the tendency of several properties such as acidity and water content. A dielectric constant sensor is also used to measure various oil properties; therefore, it is very useful. The dielectric constant is the ratio of the capacitance of a capacitor using that material as a dielectric to that of a similar capacitor using vacuum as its dielectric. The dielectric constant has an effect on water content, contaminants, base oil, additive, and so forth. In this study, the dielectric constant sensor is fabricated using MEMS process. In the fabrication process, the shape, gap of the electrode array, and thickness of the insulation material are considered to improve the sensitivity of the sensor.

• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.62-64
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• 2015

We have investigated zinc tin oxide (ZTO) thin films under various silicon ratios. ZTO TFTs were fabricated by solution processing with the bottom gate structure. Furthermore, annealing process was performed at different temperatures in various annealing conditions, such as air, vacuum and wet ambient. Completed fabrication of ZTO TFT, and the performance of TFT has been compared depending on the annealing conditions by measuring the transfer curve. In addition, structure in ZTO thin films has been investigated by X-ray diffraction spectroscopy (XRD) and Scanning electron microscope (SEM). It is confirmed that the electrical performance of ZTO TFTs are improved by adopting optimized annealing conditions. Optimized annealing condition has been found for obtaining high mobility.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.410-410
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• 2012

The continuous monolayer graphene was synthesized on electro-polished copper foil. Electro-polishing sticks off the coating layer of copper foil, which prevents the continuous graphene growth. The quality of continuous graphene is dependent on roughness of copper foil. Copper foil roughness could be controlled by changing polishing condition. The effects of working voltage (4-6 V) and time (30-70 sec) for electro-polishing were systematically examined. The change of surface roughness was checked with AFM.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.58.2-58.2
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• 2010

This paper deals with the simulation of solid particle coating technology via supersonic nozzle in vacuum environment to devote as an aerosol-deposition device. In order to improve efficiencies of nozzle and coating process, effects of shockwave, nozzle geometry, and substrate location were studied computationally under a fixed chamber pressure of 0.01316 bar which is nearly vacuous. Shockwave is the important factor affect to entire flow because shockwave in the jet flow dissipates the kinetic energy of the flow in the supersonic condition. Results show that various nozzle geometries have significant effect on the supersonic flow and we know that the supersonic nozzle should be optimized to minimize the loss of the flow. Another parameter, the distance between substrate and nozzle tip, shows little effect in this study.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.229-229
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• 2012

Adhesion of Copper film on the aluminum oxide layer formed by anodizing an aluminum plate was enhanced by applying ion beam mixing method. Forming an conductive metal layer on the insulating oxide surface without using adhesive epoxy bonds provide metal-PCB(Printed Circuit Board) better thermal conductivities, which are crucial for high power electric device working condition. IBM (Ion beam mixing) process consists of 3 steps; a preliminary deposition of an film, ion beam bombardment, and additional deposition of film with a proper thickness for the application. For the deposition of the films, e-beam evaporation method was used and 70 KeV N-ions were applied for the ion beam bombardment in this work. Adhesions of the interfaces measured by the adhesive tape test and the pull-off test showed an enhancement with the aid of IBM and the adhesion of the ion-beam-mixed films were commercially acceptable. The mixing feature of the atoms near the interface was studied by scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.287.2-287.2
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• 2016

Silicon has considerably good characteristics on electron, hole mobility and its price. With 2-D sinlge-layer Graphene/n-Si heterojunction solar cell shows that in one sun condition exhibit power conversion efficiency(PCE) of 10.1%. This photovoltaic effect was achieved by applying gate voltage to the Schottky junction of the heterostructure solar cell. Energy band diagram shows that Schottky barrier between Si and graphene can be adjust by the external electric field. because of the fermi level of the graphene can be changed by external gate voltage, we can control the Schottkky barrier of the heterostructure solar cell. The ratio between generated power of solar cell and consumption electrical power is remarkable. Since we use the graphene as the top gate electrode, most of the sun light can penetrate into the active area.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.87.2-87.2
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• 2016

As an era of nano science approaches, the understanding on the shape and optical properties of various materials in a nanoscale range is getting important more seriously than ever. Accordingly the development of high spatial-temporal-spectral resolution measurement tools for characterization of nanomaterials/structures is highly required. Generally, the various properties of sample can be measured independently, e.g. to observe the structural property of sample, we use the scanning electron microscopy or atomic force microscopy, and to observe optical property, we have to use another independent measurement tool such as photoluminescence spectroscopy or Raman spectroscopy. In the case of nano-materials, however, it is very difficult to find out the same position of sample at every different measurement processes, and the condition of sample can be changed by the influence of first measurement. The tip enhanced Raman scattering(TERS), which can simultaneously measure the two or more information of sample with nanoscale spatial resolution, is one of solutions of this problem. In this talk, I will present our recent nano Raman scattering data of graphene that measured by TERS and optimized tip fabrication method for efficient experiment.