• 열처리공학회지
• /
• 제23권6호
• /
• pp.344-349
• /
• 2010

Silicon carbide nanowires were grown by heat treatment of the films at $1200^{\circ}C$ after amorphous SiC thin films were deposited on graphite substrate by radio frequency magnetron sputtering at $600^{\circ}C$. It was confirmed that SiC nanowires with the diameter of 20-60 nm and length of about 50nm were grown from Field Emission Scanning Election Microscope (FE-SEM) and Transmission Election Microscope (TEM) observation. The diameter of nanowires was increased as heat treatment time is increased. The nanowires were identified to ${\beta}$-SiC single crystalline from X-Ray Diffraction(XRD) analysis. It was observed from this study that deposition temperature of samples was critical to the crystallization of nanowires. On the other hand, the effect of deposition time was insignificant.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
• /
• pp.692-693
• /
• 2002

Well-aligned multi-wall carbon nanotubes (MWNTs) were fabricated by utilizing a radio frequency plasma-enhanced chemical vapor deposition (rf-PECVD) system from Ni particles at the bottom of anodic alumina nanoholes (AAN). To remove the amorphous graphite layers on the AAN surface and to eliminate the protrusion of MWNT tips, the AAN surface with MWNTs were treated by external rf plasma source. As a result, the AAN surface almost became flat without having any protrusion of MWNT tips. The diameter, length of MWNTs and AAN were investigated by using a scanning electron microscopy (SEM). Raman spectroscopy was also used to characterize wall structure of the carbon nanotube. And the emission properties of the MWNTs were measured for the application of field emission display (FED) in near future.

• 한국자동차공학회논문집
• /
• 제4권4호
• /
• pp.171-178
• /
• 1996

DCB(pure mode I) and CLS(mixed mode) tests were performed to investigate the effect of fracture mode on the interlaminar fracture of composite laminate. Mode I critical strain energy release rate was found to be $133J/m^2$ from the DCB test and total strain energy release rate decreased from $1, 270J/m^2$ as thickness ratio(tl/t) varied from 0.333 to 0.667 from the crease from the CLS test. Crack length had no effect on the total strain energy release rate and load was almost constant during the crack growth of the specimen which had the specific thickness ratio. Crack initiated when the stress of the strap ply reached constant stress $42kgf/mm^2$ which was found to be independent of the thickness ratio.

• 한국재료학회지
• /
• 제14권2호
• /
• pp.83-89
• /
• 2004

SiC nanotubes were synthesized by SLS growth mechanism using various metal catalysts. Synthesized nanotubes had mean diameters of 20~50 nm and several $\mu\textrm{m}$ length. The kind of catalysts affected microstructures of SiC nanotubes by different diffusion routes. These differences are attributed to catalysts' physical properties and relative activities to the graphite substrate. Fe acted as a good catalyst of SLS growth mechanism. But in case of Ni, SiC nanotubes grew slowly. Optical property was measured by photoluminescence measurement. Relatively broad peak was obtained and mean peak positioned at about 430 nm. This result was the same as other nanocrystalline SiC materials, but was different from the results of bulk SiC probably due to quantum confinement effect and defect in the grown SiC nanotube.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2003년도 암반역학위원회 학술세미나 논문집
• /
• pp.165-193
• /
• 2003

The Han River tunnel connecting Yoido and Mapo was constructed as a part of the Seoul subway line No.5, which is 52 km long, to improve the traffic conditions of Seoul. It is constructed 15.6∼30m below the river floor. It Is the first under-river tunnel in Korea with the length of 1,288m. Geological conditions of the ground under the Han River were more complex and irregular than expected at the design stage, because there were several faults, fracture zones and slickensided joints coated with graphite. It was thus indispensable to estimate the ground condition of the tunnel face to apply proper excavation and reinforcement methods. Advance borings and face mappings were performed before excavation to improve constructional efficiency and excavation stability.

• 대한화학회지
• /
• 제22권5호
• /
• pp.340-355
• /
• 1978

化學反應 수반하는 氣體吸着反應器의 設計에 가장 重要한 氣液界面間의 物質傳達係數와 面積을 測定하는데 자주 모델反應이 利用된다. 本硏究는 그 中에서 wetted wall column 에 sulfite-system을 dldydgkdu 特別히 氣液間의 接觸時間이 氣體吸着速道에 미치는 영향을 硏究 檢討하였다. 反應速道가 매우 빠르거나 늦으면 column의 길이에 따라서, 다시 말하면 接觸時間에 따라서 氣體吸着速道에 差異가 크다는 것을 發見했다. 反應速道恒數 $k_2=5.5{\times}10^6m^3/kmol{\cdot}s$ 近處에서는 이 差異가 없어진다. 換言하면 이런 條件下에서 裝置의 hydrodynamics가 氣體吸着速道에 無關해진다. 金屬 column 代身에 graphite column을 使用할 수 있다는 例證을 題示하였다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제40회 동계학술대회 초록집
• /
• pp.490-490
• /
• 2011

Graphene, hexagonal network of carbon atoms forming a one-atom thick planar sheet, has been emerged as a fascinating material for future nanoelectronics. Huge attention has been captured by its extraordinary electronic properties, such as bipolar conductance, half integer quantum Hall effect at room temperature, ballistic transport over ${\sim}0.4{\mu}m$ length and extremely high carrier mobility at room temperature. Several approaches have been developed to produce graphene, such as micromechanical cleavage of highly ordered pyrolytic graphite using adhesive tape, chemical reduction of exfoliated graphite oxide, epitaxial growth of graphene on SiC and single crystalline metal substrate, and chemical vapor deposition (CVD) synthesis. In particular, direct synthesis of graphene using metal catalytic substrate in CVD process provides a new way to large-scale production of graphene film for realization of graphene-based electronics. In this method, metal catalytic substrates including Ni and Cu have been used for CVD synthesis of graphene. There are two proposed mechanism of graphene synthesis: carbon diffusion and precipitation for graphene synthesized on Ni, and surface adsorption for graphene synthesized on Cu, namely, self-limiting growth mechanism, which can be divided by difference of carbon solubility of the metals. Here we present that large area, uniform, and layer controllable graphene synthesized on Cu catalytic substrate is achieved by acetylene-assisted CVD. The number of graphene layer can be simply controlled by adjusting acetylene injection time, verified by Raman spectroscopy. Structural features and full details of mechanism for the growth of layer controllable graphene on Cu were systematically explored by transmission electron microscopy, atomic force microscopy, and secondary ion mass spectroscopy.

• Structural Engineering and Mechanics
• /
• 제54권5호
• /
• pp.855-875
• /
• 2015

Many novel materials exhibit a property of different elastic moduli in tension and compression. One such material is graphene, a wonder material, which has the highest strength yet measured. Investigations on buckling problems for structures with different moduli are scarce. To address this new problem, firstly, the nondimensional expression of the relation between offset of neutral axis and deflection curve is derived based on the phased integration method, and then using the energy method, load-deflection relation of the rod is determined; Secondly, based on the improved constitutive model for different moduli, large deformation finite element formulations are developed and combined with the arc-length method, finite element iterative program for rods with different moduli is established to obtain buckling critical loads; Thirdly, material mechanical properties tests of graphite, which is the raw material of graphene, are performed to measure the tensile and compressive elastic moduli, moreover, buckling tests are also conducted to investigate the buckling behavior of this kind of graphite rod. By comparing the calculation results of the energy method and finite element method with those of laboratory tests, the analytical model and finite element numerical model are demonstrated to be accurate and reliable. The results show that it may lead to unsafe results if the classic theory was still adopted to determine the buckling loads of those rods composed of a material having different moduli. The proposed models could provide a novel approach for further investigation of non-linear mechanical behavior for other structures with different moduli.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.294.2-294.2
• /
• 2016

Graphene, a sigle atomic layered structure of graphite, has drawn many scientific interests for attractive future electronics and optoelectronics beyond silicon-based technology because of its robust physical, optical, and electrical properties. But high metal-graphene contact resistance prevents the successful integration of high speed graphene devices and circuits, although pristine graphene is known to have a novel carrier transport property. Meanwhile, in the recently reported metal-graphene contact studies, there are many attempts to reduce the metal-graphene contact resistance, such as doping and one-dimensional edge contact. However, there is a lack of quantitative analysis of the edge contact scheme through variously designed patterns with different metal contact. We first investigate the effets of edge contact (metal-graphene interface) on the contact resistance in terms of edge pattern design through patterning (photolithography + plasma etching) and electral measurements. Where the contact resistance is determined using the transfer length method (TLM). Finally, we research the role of metal-kind (Palladium, Copper, and Tianium) on the contact resistance through the edge-contacted devices, eventually minimizing contact resistance down to approximately $23{\Omega}{\cdot}{\mu}m$ at room temperature (approximately $19{\Omega}{\cdot}{\mu}m$ at 100 K).

• Carbon letters
• /
• 제11권3호
• /
• pp.184-191
• /
• 2010

Carbon nanotubes are unique tubular structures of nanometer diameter and large length/diameter ratio. The nanotubes may consist of one up to tens and hundreds of concentric shells of carbons with adjacent shells separation of ~0.34 nm. Multiwalled carbon nanotubes were synthesized by arc-discharge technique. MWCNTs were formed at the cathode deposit along with other carbonaceous materials like amorphous carbon, graphite etc. However, to get the best advantage of carbon nanotubes in various advanced applications, these undesired carbonaceous materials to be removed which is a challenging task. In the present study, various techniques were tried out for purifying MWCNTs such as physical filtration, chemical treatment and thermal annealing. SEM, FTIR, TGA and BET techniques were used to characterize the CNTs at various stages. Results shows that suitable chemical treatment followed by thermal annealing under controlled flow of oxygen gives the better route for purification of carbon nanotubes.