• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.139.1-139.1
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• 2013

Graphene and graphene oxide (GO) have been modified with palladium nanoparticles (Pd NPs) to develop high performance catalysts for the Sonogashira cross coupling reaction. To understand catalytic performance of Pd NPs on graphene (Pd/G) and Pd NPs on GO (Pd/GO), we monitored their morphological and electronic structural changes before/after Sonogashira reaction using FT-IR, XRD, XPS, and XAFS. Here, we demonstrate that both Pd/G and Pd/GO show high catalytic efficiency toward the Sonogashira reaction, but only Pd/GO revealed excellent recyclability. The remarkable catalytic efficiency of both catalysts is attributed to the high degree of the Pd NP dispersions on supports and thus smaller Pd NPs can provide highly reactive low coordinated Pd atoms. However, we attributed the excellent recyclability of Pd/GO to the presence of oxygen functionalities on GO, which can provide nucleation sites for the detached Pd atoms during the Sonogashira reaction and prevent agglomeration of the Pd NPs since the oxygen functional groups are very reactive to mobile Pd adatoms.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.263.2-263.2
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• 2013

We report a systematic investigation of a set of macrophotoinitiators for use in polymerization-based signal amplification. To test the dependence of photopolymerization responses on the number of photoinitiators localized per molecular recognition event, we gradually increased the number of photoinitiator molecules coupled to a scaffold macromolecule. Macrophotoinitiators constructed with an average of 7 to 168 photoinitiators per polymer with the goals of quantifying the relationship between the number of initiators per binding event and the degree of amplified colorimetric readout. To evaluate the capacity of the macrophotoinitiators to detect molecular recognition, neutravidin was coupled to these molecules to recognize biotin-labeled DNA immobilized on biochip test surfaces. Fluorescein macroinitiators are found to be useful in detecting molecular recognition above a threshold of initiators per polymer. Above this threshold, increasing the number of initiators per macroinitiator resulted in increased signal strength.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.14 no.1
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• pp.31-38
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• 1985

By using the hollow shaft with $0.5^{\circ}$ internal taper, ball valve and rubber packing, charging the working fluid at engineering vacuum degree (vacuum pressure higher than 1 torr) and carrying out experiments, it was investigated the performance of rotating heat pipe with variant operating conditions. In this experiment, it was shown that it is impossible the internal liquid flow was laminar film flow which agree with the assumption of present theoretical analyses, but the internal vorticity makes the heat transfer increase and for the maximum heat transfer there is optimal mass loading for the given heat pipe geometry and operational conditions.

• Applied Biological Chemistry
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• v.30 no.1
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• pp.65-70
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• 1987

In Girder to measure the pressure and weight decrease of drying sample during the vacuum drying process of food, sensing devices were designed and constructed with strain gauge. Microcomputer based vacuum drying system was made up of these devices interfaced to apple II microcomputer. The electrical output signal from vacuum sensor which constituted with Bourdon tube whereon strain gauge attached were digitalized and input to microcomputer through the MC 6821 interface I.C. chip. The relationship between read-out digital value (D) from microcomputer and readings of vacuum gauge (P, mmHg) was P=-146.136+3.620D'(r=0.9994) The pressure control of vacuum dryer was successfully conducted in the range of $400{\sim}600\;mmHg$ accuracy. The digitalized load cell output (D) could be correlated with the real weight (W, g) as W=-14,000+0.585D (r=0.9998) Drying curves of green red pepper under $64^{\circ}C$, $400{\sim}600\;mmHg$ was similar to those of red pepper and differently affected by the degree of vacuum pressure but was varied according to their shape (cut or whole). Moisture movement of green red pepper during the vacuum drying process was fitted to Page model. The empirical equations obtained were $M-M_e/M_o-M_e={\exp}\;(-0.0673{\theta}^{1.177})$ and $M-M_e/M_o-M_e={\exp}\;(-0.0655\;{\theta}^{1.477})$ for whole and cut green red pepper, respectively.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.105-110
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• 2001

Autoclave curing using the vacuum bagging method is widely used for the manufacture of advanced composite prepreg airframe structures. Due to increasing use of advanced composites, specific techniques have been developed to repair damaged composite structures. In order to repair the damaged part, it is required that the damaged areas be removed, such as skin and/or honeycomb core, by utilizing the proper method and then repairing the area by laying up prepreg (and core) then curing under vacuum using the vacuum bagging materials. It shall be cured either in an oven or autoclave per the original specification requirements. Delamination can be observed in the sound areas during and/or after a couple times exposure to the elevated curing temperature due to the repeated repair condition. This study was conducted for checking the degree of degradation of properties of the cured parts and delamination between skin prepreg and honeycomb core. Specimens with glass honeycomb sandwich construction and glass/epoxy prepreg were prepared. The specimens were cured 1 to 5 times at $260^{circ}F$ in an autoclave and each additionally exposed 50, 100 and 150 hours in the $260^{circ}F$ oven. Each specimen was tested for tensile strength, compressive strength, flatwise tensile strength and interlaminar shear strength. To monitor the characteristics of the resin itself, the cured resin was tested using DMA and DSC. As a results, the decrease of Tg value were observed in the specific specimen which is exposed over 50 hrs at $260^{circ}F$. This means the change or degradative of resin properties is also related to the decrease of flatwise tensile properties. Accordingly, minimal exposure on the curing temperature is recommended for parts in order to prevent the delation and maintain the better condition.

• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.53-58
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• 2013

KSTAR in-vessel cryo-pump has been installed in the vacuum vessel top and bottom side with up-down symmetry for the better plasma density control in the D-shape H-mode. The cryogenic helium lines of the in-vessel cryo-pump are located at the vertical positions from the vacuum vessel torus center 2,000 mm. The inductive electrical potential has been optimized to reduce risk of electrical breakdown during plasma disruption. In-vessel cryo-pump consists of three parts of coaxial circular shape components; cryo-panel, thermal shield and particle shield. The cryo-panel is cooled down to below 4.5 K. The cryo-panel and thermal shields were made by Inconel 625 tube for higher mechanical strength. The thermal shields and their cooling tubes were annealed in air environment to improve the thermal radiation emissivity on the surface. Surface of cryo-panel was electro-polished to minimize the thermal radiation heat load. The in-vessel cryo-pump was pre-assembled on a test bed in 180 degree segment base. The leak test was carried out after the thermal shock between room temperature to $LN_2$ one before installing them into vacuum vessel. Two segments were welded together in the vacuum vessel and final leak test was performed after the thermal shock. Commissioning of the in-vessel cryo-pump was carried out using a temporary liquid helium supply system.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.139.2-139.2
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• 2016

Electrons and phonons in chalcogenide-based materials play are important factors in the performance of an optical data storage media and thermoelectric devices. However, the fundamental kinetics of carriers in chalcogenide materials remains controversial, and active debate continues over the mechanism responsible for carrier relaxation. In this study, we investigated ultrafast carrier dynamics in an multilayered $\{Sb(3{\AA})/Te(9{\AA})\}n$ thin film during the transition from the amorphous to the crystalline phase using optical pump terahertz probe spectroscopy (OPTP), which permits the relationship between structural phase transition and optical property transitions to be examined. Using THz-TDS, we demonstrated that optical conductance and carrier concentration change as a function of annealing temperature with a contact-free optical technique. Moreover, we observed that the topological surface state (TSS) affects the degree of enhancement of carrier lifetime, which is closely related to the degree of spin-orbit coupling (SOC). The combination of an optical technique and a proposed carrier relaxation mechanism provides a powerful tool for monitoring TSS and SOC. Consequently, the response of the amorphous phase is dominated by an electron-phonon coupling effect, while that of the crystalline structure is controlled by a Dirac surface state and SOC effects. These results are important for understanding the fundamental physics of phase change materials and for optimizing and designing materials with better performance in optoelectronic devices.

• Journal of the Korean Vacuum Society
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• v.18 no.3
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• pp.221-228
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• 2009

The purpose of this paper is to discuss the fabrication of $\beta$-PVDF($\beta$-Polyvinylidene fluoride, $\beta$-PVF2) organic thin films through the vapor deposition method and to investigate the ultrasonic response properties of the organic thin films produced. Vapor deposition was performed under the following conditions : the temperature of evaporator, the applied electric field and the pressure of reaction chamber were $270^{\circ}C$, 142.4 kV/cm and $2.0{\times}10^{-5}\;Torr$, respectively. The results showed that the degree of crystallinity increased from 47% to 67.8% with an increase in the substrate temperature. In the case of a sensor response characteristic by varying the distance from 1cm to 100cm, the output voltage decreased from 0.615V to 0.4V.

• Journal of the Korean Vacuum Society
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• v.13 no.2
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• pp.72-78
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• 2004

Cu seed layers deposited by magnetron sputtering onto tantalum nitride barrier films were treated with ECR plasma and then the copper films were electroplated and rapid thermal annealed in an argon or nitrogen atmosphere at various temperatures ranging from 200 to $500^{\circ}C$. Changes in the microstructure and physical properties of the copper films electroplated on the hydrogen ECR plasma cleaned copper seed layers were investigated using X-ray diffraction (XRD), electron back-scattered diffraction (EBSD), and atomic force microscopy (AFM) analyses. It was found that the copper film undergoes complete recrystallization during annealing at a temperature higher than $400^{\circ}C$. The resistivity of the Cu film tends to decrease and the degree of (111) preferred orientation tends to increase as the annealing temperature increases. Theoptimum annealing condition for obtaining the film with the lowest resistivity, the smoothest surface and the highest degree of the (111) preferred orientation is rapid thermal annealing in a nitrogen atmosphere at $400^{\circ}C$ for 120 s. The resistivity and the surface roughness of the electroplated copper film annealed under this condition are 1.98 $\mu$O-cm and 17.77 nm, respectively.

• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.337-345
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• 2009

When the drill hole diameter for the package substrate is under $100{\mu}m$, the smear in the drill hole cannot be eliminated by wet desmear process only. We intended to change the substrate's hydrophobic characteristics to hydrophilic characteristics by adapting the atmospheric pressure plasma prior to the wet desmear process. Atmospheric pressure plasma process was made as the inline type equipment which is adequate for the package substrate's manufacturing process and remote DBD type electrodes were used for the equipment. As the result of atmospheric pressure plasma processing, the contact angle of the substrate was enhanced from 71 degree to 30 degree. Dielectric film thickness, drill hole diameter and surface roughness were measured to evaluated the characteristics of the wet desmear process in case of plasma processing and in case of none. By the measurement, it was analyzed that the process uniformity within the whole panel was largely enhanced. Also, it was verified that the smear in the drill hole was eliminated efficiently which was analyzed by the SEM image of the drill hole.