• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.224-224
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• 2012

위성체가 작동하는 우주환경인 고진공상태에서는 위성체의 부품에서 발생 할 수 있는 outgassing으로 인해 위성체가 오염되어 위성체의 성능이 저하될 수 있으며, 특히 이차면경(second surface mirror) 및 광학렌즈 등을 오염시킴으로써 위성체 본연의 임무수행 실패라는 결과를 초래할 수도 있다. 따라서 지상에서 위성체의 부품에 대해 고온($85^{\circ}C$ 이상)과 고진공($5.0{\times}10-3Pa$ 이하)의 상태를 모사하여 오염물질을 제거함으로써 outgassing의 발생을 막고, 아울러 오염근원을 검출할 수 있는 vacuum bake-out 시험이 필수적이라 할 수 있다. 이를 위해서 한국항공우주연구원 위성시험동에는 전용 bake-out 챔버가 설치되어 있으며 저진공용 dry pump와 booster pump를 이용하여 5.0 Pa의 저진공을 형성하고, 2대의 cryopump를 이용하여 $5.0{\times}10-3Pa$ 이하의 고진공을 생성하게 되는데, Bake-out 챔버의 진공 배기시스템에 대하여 자세히 알아보고자 한다.

• Nuclear Engineering and Technology
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• v.34 no.3
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• pp.211-217
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• 2002

A 1-MW vacuum feedthrough for the KSTAR ICRF antenna is fabricated and high power RF test is performed. It is designed to have two alumina $(Al_2O_3)$ ceramic cylinders and O-ring seal instead of a brazed seal for good mechanical and thermal strength, which is important in long pulse or steady state operation. For cooling of the ceramics, dry air is circulated in a space between the two cylinders and the outer conductor. Independent cooling water channels are installed to cool the inner conductor of the feedthrough. RF high voltage test is performed using two kinds of ceramics with the purities of 99.7% and 97%. Stable operation is possible with the RF voltage of 30 kVp at long pulse of 300 sec without any severe damage.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.257-261
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• 1999

The claw pump, one of oil-less dry pumps developed to solve problems found in vacuum systems pumped by oil-sealed rotary pumps, has been widely used separately or as a part of compound structure with a roots pump. The claw pump has some merits such as a high pumping speed, a high compression ratio, and relatively little heat generation. The high compression ratio of the claw pump is compression ratio, and relatively little heat generation. The high compression ratio of the claw pump is based on efficient sweeping action of the special type rotor and an intrinsic self-valving mechanism. The contour of the rotor with claw-type blade is designed basically to make two rotors revolve smoothly without touching with each other, and related dimensions are determined by required pumping speed, compression ratio, power demand and diameter of the rotor axis. In this paper the procedure of designing the rotor of the claw pump is described and factors influencing the pump performance are analyzed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.291-291
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• 2013

The wettability of TiO2 layers is controlled by forming highly ordered arrays of nanocones using nanopatterning, based on self-assembly and dry etching. Nanopatterning of TiO2 layers is achieved via formation of self-assembled monolayers of SiO2 spheres fabricated using the Langmuir-Blodgett technique, followed by dry etching. Compared to a thin film TiO2 layer, the nanopatterned TiO2 samples show a smaller static water contact angle, where the water contact angle decreases as the etching time increases, which is attributed to the Wenzel equation. When TiO2 layers are coated by 1H,1H,2H,2H-perfluorooctyltrichlorosilane, we observed the opposite behavior, exhibiting superhydrophobicity (up to contact angle of $155^{\circ}$) on the nanopatterned TiO2 layers. Self-assembled nanopatterning of the TiO2 layer may provide an advanced method for producing multifunctional transparent layers with self-cleaning properties.

• Journal of the Korea Furniture Society
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• v.18 no.1
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• pp.13-19
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• 2007

The influences of coating on oak veneer overlaid Medium Density Fiberboard (MDF) were evaluated. The hardness of 9mm-MDF by hardness test were increased about 28% with coating on MDF and the more increased hardness of 31% with oak veneer overlaid MDF. The hardness of veneer overlaid MDF increased with increment of the veneer thickness and that of overlaid MDF showed the higher hardness compared to non-overlaid MDF. The optimum moisture content in terms of the hardness of panels MDF was in the range of 7% to 10% and the hardness was decreased with increasing of the moisture content. Any cracks were not overlaid coated on the MDF but the cracks were observed on the overlaid MDF after Soak under Vacuum Dry 10-cycle. The thicker veneer-overlaid MDF showed more cracks.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.159.1-159.1
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• 2014

We report a simple method for preparing hydrophobic mesoporous silica and its use as a pre-concentrating agent of gas analytes. Hydrophobic mesoporous silica was prepared by coating PDMS (polydimethylsiloxane) thin layer on commercial mesoporous silica with thermal deposition method in a sealed chamber. By using this method, we were able to coat PDMS layer on inner-walls of pores larger than 15 nm. Also, contact angle measured on a surface consisting of PDMS-coated mesoporous silica exceeded $150^{\circ}$, implying that the surface has high water repellency. Pre-concentration ability of PDMS-coated mesoporous silica and baremesoporous silica was tested under dry and humid conditions. Adsorption and molecular desorption of gas analytes was much enhanced by PDMS-coating on mesoporous silica under both dry and humid conditions. Therefore we suggest that PDMS-coated mesoporous silica can be an efficient pre-concentration agent in order to enhance sensitivity of various detectors.

• Applied Science and Convergence Technology
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• v.24 no.2
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• pp.27-32
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• 2015

We analyzed the destruction patterns of a turbo-molecular pump (TMP) resulting from its sudden exposure of a foreline to the atmospheric pressure due to a destruction of the foreline connecting clamp of an ICP dry etcher for 300 mm wafers during high-vacuum operation ($5{\times}10^{-6}$ Torr). Unlike in the case of view port's breakage, the TMP's rotor module was crashed inside the chamber. The primary damage resulted from the collision of the blades and stators, and the secondary damage resulted from the breaking of the rotor - driving shaft assembly. The fixing screws of the rotor and axial shaft were bent and broken when the TMP controller output the maximum current even after the crash event. Electrical power consumption analysis of the TMP power controller confirmed it. The stress distributions were analyzed by a finite element method using CFD-ACE+ multi physics software. Rotating inertia of each parts and kinetic energies were calculated as well. 68% of the rotational kinetic energy is deposited by the rotor - shaft module.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.268-268
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• 2012

Adsorption and desorption of toluene from bare and $TiO_2$-coated silica with a mean pore size of 15 nm was studied using breakthrough curves and temperature programmed desorption. Thicknesses of $TiO_2$ films prepared by atomic layer deposition on silica were < 2 nm, and ~ 5 nm, respectively. For toluene adsorption, both dry and humid conditions were used. $TiO_2$-thin film significantly improved toluene adsorption capacity of silica under dry condition, whereas desorption of toluene from the surface as a consequence of displacement by water vapor was more pronounced for $TiO_2$-coated samples with respect to the result of bare ones. In the TPD experiments, silica with a thinner $TiO_2$ film (thickness < 2 nm) showed the highest reactivity for toluene oxidation to $CO_2$ in the absence and presence of water. We show that the toluene adsorption and oxidation reactivity of silica can be controlled by varying thickness of $TiO_2$ thin films.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.509-509
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• 2011

Superhydrophobic surfaces on alloyed steels were fabricated with a non-conventional method of plasma etching and subsequent water immersion procedure. High aspect ratio nanopatterns of nanoflake or nano-needle were created on the steels with various Cr content in its composition. With CF4 plasma treatment in radio-frequence chemical vapor deposition (r.-f. CVD) method, steel surfaces were etched and fluorinated by CF4 plasma, which induced the nanopattern evolution through the water immersion process. It was found that fluorine ion played a role as a catalyst to form nanopatterns in water elucidated with XPS and TEM analysis. The hierarchical patterns in micro- and nano scale leads to superhydrophobic properties on the surfaces by deposition of a hydrophobic coating with a-C:H:Si:O film deposited with a gas precursor of hexamethlydisiloxane (HMDSO) with its lower surface energy of 24.2 mN/m, similar to that of curticular wax covering lotus surfaces. Since this method is based on plasma dry etching & coating, precise patterning of surface texturing would be potential on steel or metal surfaces. Patterned hydrophobic steel surfaces were demonstrated by mimicking the Robinia pseudoacacia or acacia leaf, on which water was collected from the humid air using a patterned hydrophobicity on the steels. It is expected that this facile, non-toxic and fast technique would accelerate the large-scale production of superhydrophobic engineering materials with industrial applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.432-432
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• 2011

Dry adhesion caused by Nanoscale contact comes up to important scientific issue. Herein, we introduce bendable nanohairy locking fastener system with high shear strength and mechanically flexible backing. The polymeric patches like velcro are composed of an array of straight nanohairs with 100 nm diameter and $1{\mu}m$ height. To fabricate high aspect vertical nanohairs, we used UV molding method with appropriately flexible and rigid polyurethane acrylate material on PET substrate. Two identical nanohairy patches are easily merged and locked each other induced by van der Waals force. Because nanohairs can be arrayed with high density ${\sim}4{\times}10^8/cm^2$, we can obtain high shear adhesion force on flat surface (~22 N/$cm^2$). Furthermore, we can obtian nanohairy locking system with maximum shear adhesion ~48 N/$cm^2$ of curved surface due to flexibility of PET substrate. We confirm the tendency that shear adhesion force increases, as radius of curvature increases.