Seung Hyun Baek

The effects of sandwich-like catalysts on the vertical growth of multiwalled carbon nanotubes (MWCNTs) are investigated. We achieved the synthesis of 2.2-mm-long MWCNT forests with carefully designed catalyst films by thermal chemical vapor deposition. Two types of sandwich-like catalysts were prepared by electron beam evaporation. Fe and Al2O3 layers were deposited on a SiO2 surface of 300 nm in thickness. Here, Fe and Al2O3 were used for the catalyst and the supporting buffer layer, respective

We presented a feasible framework of studying dynamics of macromolecules by applying elastic network model (ENM) and vibration spectroscopy. We first identified the precise force constants of covalent bonds commonly observed in macromolecules by matching their reported Raman shifts data with predicted wavenumbers determined by normal mode analysis (NMA). Assigning the obtained spring constants to other small chemical compounds such as ethynyl isocyanide (C3HN) and diacetylene (C4H2), we not only

We have investigated quantitative measurement techniques of the degree of dispersion of single-walled carbon nanotubes (SWNTs). SWNTs were suspended in aqueous media using a sodium dodecyl sulfate (SDS) surfactant. SWNTs with different dispersion states were prepared by controlling the intensity and time of sonication and centrifugation. The laser spectroscopic techniques were employed to characterize the dispersion state; i.e., raman fluorescence and absorption spectroscopic techniques. Raman s

Carbon nanotube composite is considered to be a good candidate material for composite material because of its excellent mechanical property and low density under high temperature as well as good wear and frictional properties. In this study, tribological characteristics of carbon nanotube aluminum composite were evaluated using pin-on-disk wear tester. Spark Plasma Sintering method is more effective than Hot Pressing method in terms of wear and friction. The composite with 1% CNT has the lowest

Presently, countries are trying to increase their energy efficiency. Therefore, the operating temperatures of very high temperature reactor (VHTR) and high temperature gas-cooled reactor (HTGR) are increasing in order to increase overall efficiency. A metallic material’s intrinsic creep property is a limitation in this scenario. Inconel 617 alloy is a candidate material used in the intermediate heat exchangers of the VHTR and HTGR. Therefore, in this work, graphene, which is a promising ultra-th

과학기술분야 출연(연)은 기술유형에 따라 기초기술연구회와 산업기술연구회로 관리체계가 구분 운영되었지만, 2014년 7월부터 양 연구회를 통합하여 단일 관리체계가 출범하게 된다. 하지만, 단일 연구회를 통해 기관 경영상의 효율성을 제고하더라도, 출연(연)의 기술유형 특성에 부합하는 성과극대화를 위해 관리 운영방식에서는 차별화가 필요할 것이며, 이를 위해서는 R&D 성과에 영향을 미치는 세부 요인에 대한 분석이 필요하다. 이 연구에서 출연(연) 지배구조를 중심으로 하는 관리체계와 R&D 투입요인을 함께 고려하여 분석한 결과, 관리체계에 따라 R&D 성과의 유형과 그 영향요인들이 다르게 나타났다. 기초기술연구회 소관기관은 SCI 논문실적이, 산업기술연구회 소관기관은 특허출원 기술료수입에서 더 많은 성과가 나타나고 있었다. R&D 성과 영향요인으로서 관리체계가 갖는 영향력도 매우 크게 나타났으며, Chow 검정을 통해서 R&D 성과에 영향을 미치는 요인들이 관리체계에 따라 구조적인 차이가

This study investigated the phonological awareness of two groups of eighty-six Korean EFL/ESL kindergarteners in terms of semivowel placement differences between Korean and English and moreover, examined the relationship of their phonological representations to their vocabulary knowledge across the two languages. Children were assessed in Korean/English on an experimental task of production of semivowels (i.e., /j/ and /w/) in real/non-real words spoken to them and a test of lexical knowledge. A

가스절연개폐장치 (Gas-insulated switchgear, GIS)의 내부에는 절연에 관한 이상 여부를 감시하고 판단할 수 있는 시스템이 요구된다. 부분방전에 의해 발생되는 SF6 분해생성물에 관한 단일벽 탄소나노튜브 (Single-walled carbon nanotube, SWNT)가 지닌 우수한 검출기능 때문에 SWNT를 이용한 가스센서 개발이 활발히 진행되고 있다. 하지만 아직까지 부분방전에 의해 발생된 분해생성물의 확산현상에 관한 해석적 연구는 미흡한 실정이다. 본 논문에서는 실험 데이터 및 상용 CFD (Computational Fluid Dynamics) 프로그램을 이용하여 SWNT 가스센서에 포획되는 분해생성물의 코로나 방전에 의한 발생과정과 챔버 내부에서의 확산과정을 모델링하여 부분방전 발생 시 챔버 내부의 온도, 압력, 그리고 분해생성물의 농도 등을 수치계산하였다. 분해생성물의 시간당 질량생성율과 발생온도는 각각 5.04×10-10 [g/s]와 773 K이라 가

An advancement can be seen in ultra-thin coatings used for the enhancement of material durability and lifespan. Among candidate materials, copper is used in various applications, such as micro sensors, nuclear fuel waste deposition canisters, and International Thermonuclear Experimental Reactor first walls. However, it is easily susceptible to metal creep, due to its exposure to harsh environments. In this study, graphene, a promising ultra-thin material, is tested as a single-layer coating subs

The present study explored the stress placement processing of sixty-four ninth-graders learning to speak and read in Korean as a first language (L1) and English as a second language (L2) concurrently. Students’ productive stress processing abilities were assessed in reading Korean real words, English unfamiliar real words, and English pseudo-words. Results unveiled that the Korean-speaking English language learners (ELLs) performed differently in terms of language, number of syllables and syllab

Dielectrophoresis has received considerable attention for separating nanotubes according to electronic types. Here we examine the effects of surface conductivity of semiconducting single-walled carbon nanotubes (SWNT), induced by ionic surfactants, on the sign of dielectrophoretic force. The crossover frequency of semiconducting SWNT increases rapidly as the conductivity ratio between the particle and medium increases, leading to an incomplete separation of ionic surfactant suspended SWNT at an

Carbon nanotubes have attracted much attention as future mechanical and electronic materials. However, manipulating techniques are not well developed yet. Here we propose to use electrostatic drop-on-demand devices to eject micro-droplets containing micelle-suspended single-walled carbon nanotubes. A simple electrostatic force analysis and photographic studies of droplet ejection process are presented. The analytical analysis shows that semiconducting species have higher electrostatic force dens