• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.430.1-430.1
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• 2014

According to advanced nanotechnology in the field of biomedical engineering, many studies of the interaction between topography of surfaces and cellular responses have been focused on nanostructure. In order to investigate this interaction, it is essential to make well-controlled nanostructures. Electron beam lithography (EBL) have been considered the most typical processes to fabricate and control nano-scale patterns. In this work, $TiO_2$ nanowire array was fabricated with hybrid process (top-down and bottom-up processes). Nanodot arrays were patterned on the substrate by EBL process (top-down). In order to control the spacing between nanodots, we optimized the EBL process using Poly(methyl methacrylate) (PMMA) as an electron beam resist. Metal lift-off was used to transfer the spacing-controlled nanodots as a seed pattern of $TiO_2$ nanowire array. Au or Sn nanodots which play an important role for catalyst using Vapor-Liquid-Solid (VLS) method were patterned on the substrate through the lift-off process. Then, the sample was placed in the tube furnace and heated at the synthesis temperature. After heat treatment, $TiO_2$ nanowire array was fabricated from the nanodots through VLS method (bottom-up). These results of spacing-controlled nanowire arrays will be used to study the interaction between nanostructures and cellular responses in our next steps.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.171-171
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• 2011

Co and Fe doped multi-wall carbon nano-tubes (MWCNTs) synthesized by microwave plasma enhanced chemical vapor deposition (PECVD) technique are investigated with synchrotron radiations at Pohang Light Source (PAL) and European Synchrotron Radiation Facility (ESRF). Near edge x-ray absorption spectroscopy (NEXAFS) measurement at C K, Co $L_{3,2}$ and Fe $L_{3,2}$-edges, and x-ray magnetic circular dichroism (XMCD) at Co and Fe $L_{3,2}$-edges have been carried at 7B1 XAS KIST and 2A MS beamline, respectively, to understand the electronic structure and responsible magnetic interactions at room temperature. X-ray absorption spectroscopy (XAS) at C K-edge shows significant p-bonding and Co and Fe L-edges proves the presence of $Co^{2+}$ and $Fe^{2+}$ in octahedral symmetry. Co and Fe doped MWCNTs show good XMCD spectra at 300K. The effect on the magnetism is also studied through swift heavy ion (SHI) radiations and magnetism is found enhanced and change in the electronic structure in Co-CNTs is investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.327-327
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• 2011

A nonthermal bioplasma source was developed for application to human liquid fluids by making use of nano-size tungsten tips. Characteristics of the plasma source are investigated. Here we have used the AC voltage system. The bioplasma source generated by a tungsten tip with quartz tube and ground electrode is a low-temperature plasma without making any noticeable damage to cells at a low power operation. The breakdown voltage and current signals are measured by high voltage probe (Tektronix P6015A) and current probe (P6021). Variation of breakdown temperature near the tip electrode is larger than that in the neighborhood of ground electrode. Bubble formation during discharge has been recorded and investigated by using the high speed camera. The existence and behavior of hydroxyl and superoxide radicals are detected and measured by spectrometers. The electrical and optical properties of breakdown characteristics are also investigated.

• KSBB Journal
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• v.17 no.6
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• pp.577-581
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• 2002

In an attempt to produce recombinant proteins using the pollen enriched in some plant species, a 1.7 kb DNA encoding urease subunit B (UreB) amplified by PCR from Helicobacter pylori urease gene cluster in pH808 plasmid was cloned to be expressed under CaMV35S promoter in lily (Lilium longiflorum) pollen tubes elongated in vitro. Lily pollen at early germinating stage was transformed with the ureB DNA using Agrobacterium via vacuum infiltration and, incubated for a full pollen tube growth 16 - 24 h in the dark in the presence of kanamycin. DNA integration and expression in the transgenic pollen were analyzed by the standard molecular techniques and the results suggest that the pollen in vitro may be employed as a protein factory in a disposable fashion.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.242-242
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• 2013

현재 크라이오펌프의 주요 관심기술은 생산성 향상을 위한 급속 재생기술의 확보와 극저온 냉동기의 효율 향상 기술 및 저진동 기술의 확보이다. 크라이오펌프는 크게 냉동기 모듈과 펌프모듈로 구성되고, 냉동기 모듈은 주로 G-M 극저온 냉동기, Stirling 극저온 냉동기 또는 맥동관 극저온 냉동기 등을 사용하는데, 이것은 주로 압축기, 왕복기, 재생기, 구동장치 등으로 펌프모듈은 cryoarray와 펌프 body로 구성된다. 최근에 구조가 간단하고 장수명 및 저진동의 장점을 가진 맥동관 극저온 냉동기의 효율이 급속히 증가함에 따라 초전도, 액화 등의 분야에서 기존의 G-M 극저온 냉동기를 대체하는 추세이다. 본 연구에서는 지식경제부 제조기반산업원 천기술사업 "급속재생형 저진동 크라이오펌프 개발" 사업을 통해 급속 재생, 저진동, 고신뢰성 확보를 위해 기존의 G-M 극저온 냉동기를 맥동관 극저온 냉동기로 대체 적용 개발 및 국산화를 도모하고자 한다. 또한 상용화에 따른 공정 개발을 소개하고자 한다.

• Journal of Information Display
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• v.2 no.4
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• pp.34-38
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• 2001

We suggested new PDP packaging technology using the direct joint method, which does not need an exhausting hole and tube. The advantages of this method are simple process, short process time and time panel package. To packaging, we drew the seal line of glass frit by dispenser followed by forming the lump, which provide pumping-out path during the packaging process. And, we have performed a pretreatment of glass frit to reduce the out-gases. After which, both front and rear glass plates were aligned and loaded into vacuum packaging chamber. The 4-inch monochrome AC-PDP was successfully packaged and fully emitted with brightness of 1000 $cd/m^2$. Also, glass frit properties for pretreatment condition was investigated by AES and SEM analyses.

• Journal of the Korean Solar Energy Society
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• v.23 no.3
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• pp.15-22
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• 2003

This study deals with the collection of solar energy and its storage in evacuated tubular collector systems for different types of header design, flow passage and heat transfer devices. In order to elicit the most efficient combination of header design, flow passage, heat transfer hardware and operating conditions, a series of tests were done for the four different types of solar collectors utilizing vacuum tubes. The systems studied here either has the evacuated collector tubes with a metal cap on one end or the all-glass evacuated solar collector tubes These evacuated tubular collectors are known to be more efficient than the flat-plate ones in both direct and diffuse solar radiation. Test results show that the system comprised of the all-glass evacuated tubes with U-shaped copper pipes inside outperforms the other configurations. Especially, a rolled copper sheet tightly placed along the inner surface of each inner tube enhances heat transfer between the heated collector surface and the water contained in the U-shaped copper pipe.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.38-38
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• 2010

Ever since the experimental discovery of graphene exfoiliated from the graphite flakes by Geim et at., this area has drawn a lot of attention for its possible application in IT industry. For the growth of graphene, chemical vapor deposition (CVD) has been widely used to fabricate the large area graphene. The lateral size of this graphene can be easily controlled by the size of the metal substrate though the chemical etching to remove this substrate is somewhat troublesome. Another problem which is hard to avoid is the folding at the grain boundary. We will discuss the origin of the folding first and introduce the way to avoid this folding. To solve this problem, we have used the various types of micro-thin metal foils. The precise control of hydro-carbon and the carrier gas results in the formation of the graphene on top of substrate. The thickness of graphene layers can be controlled with the control of gas flow on top of Cu substrate in contrast to the previously reported self-limiting growth $behavior^1$. Uniformity of this graphene layer has been checked by micro-raman spectroscopy and SEM. The size of grain can be enhanced by thermal treatment or use of other metal substrate. The dependence of grain size on the lattice size of the substrate will be discussed. By selecting the shape of substrate, we can grow various types of graphene. We will introduce the micron size graphene tube and its application.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.99-99
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• 2010

최근 집속이온빔을 이용한 미세회로 교정, MEMS 공정 및 이온 도핑 등에 대한 연구개발이 활발히 이루어지고 있다. 기존에 널리 사용되었던 액체 금속 이온 소스의 경우 비교적 큰 angular divergence 및 Ga 이온 소스에 의한 오염이 문제시 되고 있어 이를 대체할 수 있는 가스 이온 소스에 대한 연구를 진행하였다. 본 연구에서 사용된 가스 이온 소스는 2 turn 안테나(1/4 inch Cu tube)가 감긴 반경 4 cm 석영관 내부에 Ar 가스를 주입 후 RF(13.56MHz)-ICP 타입 방전을 이용하였다. 운전 압력은 $10^{-5}\;Torr$ 범위이며 인가된 RF 전력은 최대 150 W이다. 석영관 내 발생된 플라즈마로부터 Ar 이온을 인출하기 위해 2단 인출 전극 구조가 사용되었으며 상단 전극에 고전압이 인가되고 하단 전극이 접지되는 형태이다. 2단 인출 전극의 최대 인출 전압은 10 kV, 상단 및 하단 전극의 구멍 크기는 각각 0.3 mm, 2 mm이다. 이온빔의 퍼짐을 최소화하기 위해 전극 간 공간 내 이온 거동 전산모사를 통해 전극 구조를 설계하였으며 이를 통해 최대 $30\;mA/cm^2$의 이온 전류 밀도 값을 얻을 수 있었다.

• Journal of Korea Foundry Society
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• v.43 no.5
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• pp.223-229
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• 2023

In this study, STS316L produced by a double-melting process involving vacuum induction melting (VIM) and vacuum arc remelting (VAR) was subjected to extrusion and drawing to form a tube and was subsequently electrolytic polished (EP). The grain size of the obtained STS316L without EP was approximately 55 ㎛, with no difference found after EP. The thickness of the EP layer was measured by AES and TEM, showing values of approximately 10 nm and 15 nm, respectively. After EP, the Cr/Fe and CrO/FeO ratios of the passive layer increased from 1.48 to 1.62 and from 2.15 to 2.26, respectively, while the surface roughness decreased significantly from 0.255 to 0.024 ㎛. Consequently, the corrosion rate decreased in both NaCl and HCl solutions after the EP process. Additionally, the amounts of eluted Cr and Fe ions were reduced from 1.2 to 0.8 ppb and 10.3 to 0.8 ppb, respectively. Furthermore, polarization tests revealed that STS316L treated with EP required a lower current density to reach a passive state, indicating that corrosion behavior was retarded.