• 대한기계학회논문집A
• /
• 제28권10호
• /
• pp.1534-1540
• /
• 2004

This study aims to obtain fundamental understandings involving the manufacturing processes of nano-composites with chemically surface-modified multi-walled carbon nanotubes(MWCNTs), and explore the role of functionalized MWCNTs in the epoxy/MWCNT composites. For this purpose, MWCNTs were purified by the thermo-chemical oxidation process, and incorporated into an epoxy matrix by in situ polymerization process, the surface of MWCNTs were functionalized with carboxyl functions which were demonstrated by an infrared spectroscopy. The mechanical properties of epoxy/MWCNT nano-composites were measured to investigate the role of a chemically functionalized carbon nanotubes. To improve the dispersion quality of MWCNTs in the epoxy matrix, methanol and acetone were exploited as dispersion media with sonification. The epoxy/MWCNT nano-composites with 1 or 2 wt.％ addition of functionalized carbon nanotubes show an improved tensile strength and wear resistance in comparison with pure epoxy, which shows the mechanical load transfer improves through chemical bonds between epoxy and functionalized MWCNTs. The tensile strength with 7 wt.％ functionalized MWCNTs increases by 28％ and the wear resistance is dramatically improved by 100 times.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2003년도 생물공학의 동향(XIII)
• /
• pp.494-494
• /
• 2003

• 한국전기화학회:학술대회논문집
• /
• 한국전기화학회 2003년도 춘계총회 및 학술발표회
• /
• pp.24-24
• /
• 2003

• 한국소음진동공학회논문집
• /
• 제20권6호
• /
• pp.593-603
• /
• 2010

In this paper, vibration and flow-induced flutter instability analysis of cantilever multi-wall carbon nanotubes conveying fluid and modelled as a thin-walled beam is investigated. Non-classical effects of transverse shear and rotary inertia and van der Waals forces between two walls are incorporated in this study. The governing equations and the associated boundary conditions are derived through Hamilton's principle. Numerical analysis is performed by using extend Galerkin method which enables us to obtain more exact solutions compared with conventional Galerkin method. Cantilevered carbon nanotubes are damped with decaying amplitude for flow velocity below a certain critical value, however, beyond this critical flow velocity, flutter instability may occur. Variations of critical flow velocity with both radius ratio and length of carbon nanotubes are investigated and pertinent conclusion is outlined.

• Carbon letters
• /
• 제8권3호
• /
• pp.184-190
• /
• 2007

Carbon Nano Tubes could be either metallic or semi-conducting in nature, depending on their diameter. Its photocatalytic behavior has given an impetus to use it as an anti-microbial agent. More than 95% Escherichia coli and Staphylococcus aureus bacteria got killed when exposed to Carbon Nano Tubes for 30 minutes in presence of sunlight. Carbon Nano Tubes are supposed to have smooth surface on to which it accumulates positive charges when exposed to light. The surface that is non illuminated has negative charge. At the cellular level microorganisms produce negative charges on the cell membrane, Therefore damaging effect of multi walled carbon nano tubes (exposed to light) on the microorganisms is possible. In this paper, photo catalytic killing of microbes by multi walled carbon nano tubes is reported. Killing was due to damage in the cell membrane, as seen in SEM micrographs. Moreover biochemical analysis of membrane as well as total cellular proteins by SDS PAGE showed that there was denaturation of membrane proteins as well as total proteins of both the microbes studied. The killed microbes that showed a decrease in number of protein bands (i.e. due to breaking down of proteins) also showed an increase in level of free amino acids in microbes. This further confirmed that proteins got denatured or broken down into shorter units of amino acids. Increased level of free amino acids was recorded in both the microbes treated with multi walled carbon nano tubes and sunlight.

• Advances in nano research
• /
• 제15권2호
• /
• pp.91-104
• /
• 2023

Development of thin carbon nanotubes (CNTs) nanoliquid film over the rough surface of a horizontal rotating disk is investigated by considering symmetric roughness either along the azimuthal or radial directions. The disk surface is either heated or cooled axisymmetrically from below. The effects of single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) are analyzed on the film thinning process with different types of base liquids. Closed form solutions for velocity and temperature field are obtained for small values of Reynolds number whereas the numerical solution is derived for moderate values of Reynolds number. It is found that fluid retention / depletion takes place when the roughness is symmetric along the azimuthal / radial directions. It is also seen that the film thinning rate enhances for MWCNTs compare to SWCNTs. Further it is found that two different heat transfer regions exits within the flow domain depending on the fact that heat is transferred from disk to liquid film and vice-versa.

• 한국태양에너지학회 논문집
• /
• 제32권4호
• /
• pp.9-16
• /
• 2012

Nanofluids using Carbon Nanotubes have a excellent thermal characteristic. In this study, for increasing the efficiency of solar collector, the thermal conductivity and viscosity of Ethanol-Oxidized Multi-walled Carbon Nanofluids were measured. Nanofluids were manufactured by ultra-sonic dispersing Oxidized Multi-walled Carbon Nanotubes(OMWCNTs) in ethanol at the rates of 0.0005 ~ 0.1 vol%. The thermal conductivity and viscosity of manufactured nanofluids were measured at the low temperature($10^{\circ}C$), the room temperature($25^{\circ}C$) and the high temperature($70^{\circ}C$). For measuring thermal conductivity and viscosity, we used transient hot-wire method and rotational digital viscometer, respectively. As a result, under given temperature conditions, thermal conductivity of the 0.1 vol% nanofluids improved 33.74% ($10^{\circ}C$), 33.14% ($25^{\circ}C$) and 32.36% ($70^{\circ}C$), and its viscosity increased by 37.93% ($10^{\circ}C$), 31.92% ($25^{\circ}C$) and 29.42% ($70^{\circ}C$) than the base fluids.

• 한국입자에어로졸학회지
• /
• 제9권4호
• /
• pp.231-238
• /
• 2013

Carbon nanotubes (CNTs) are one of the nanomaterials that were discovered by Iijima in 1991 for the first time. CNTs have long cylindrical and axi-symmetric structures. CNTs are made by rolling graphene sheets. Because of their large length-to-diameter ratio, they are called nanotubes. CNTs are categorized as single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) based on the shell structures. CNTs are broadly used in various fields, such as scanning probe microscopy, ultra fine nano balance and medicine, due to their extraordinary thermal conductivity, electrical and mechanical properties. Because long, straight CNTs have the same shape as asbestos, which cause cancer in cells lining the lung, there have been many studies on the effects of MWCNTs on human health that have been conducted. Stable atomization of CNTs is very important for the estimation of inhalation toxicity. In the present study, electro-static assisted axial atomizer (EAAA), which is the instrument that uses MWCNTs and aerosolizes them by transforming the single fiber shape using ultrasonic dispersion and electric field, was invented. EAAA consists of a ultrasonic bath for dispersion of MWCNTs and a particle generator for atomizing single fibers. The performance evaluation was conducted in order to assess the possibilities of 6-hour straight atomization with stability, which is the suggested exposure time in a day for the estimation of inhalation toxicity.

• 한국소음진동공학회논문집
• /
• 제20권9호
• /
• pp.805-815
• /
• 2010

This paper studies the influence of internal moving fluid and flow-induced structural instability of multi-wall carbon nanotubes conveying fluid. Detailed results are demonstrated for the variation of natural frequencies with flow velocity, and the flow-induced divergence and flutter instability characteristics of multi-wall carbon nanotubes conveying fluid and modelled as a thin-walled beam are investigated. Effects of various boundary conditions, Van der Waals forces, and non-classical transverse shear and rotary inertia are incorporated in this study. The governing equations and three different boundary conditions are derived through Hamilton's principle. Numerical analysis is performed by using extended Galerkin's method which enables us to obtain more exact solutions compared with conventional Galerkin's method. This paper also presents the comparison between the characteristics of single-wall and multi-wall carbon nanotubes considering the effect of van der Waals forces. Variations of critical flow velocity for different boundary conditions of two-wall carbon nanotubes are investigated and pertinent conclusion is outlined.

• Advances in nano research
• /
• 제6권2호
• /
• pp.163-182
• /
• 2018

Based on the Reissner mixed variational theorem (RMVT), the authors present a nonlocal Timoshenko beam theory (TBT) for the nonlinear free vibration analysis of multi-walled carbon nanotubes (MWCNT) embedded in an elastic medium. In this formulation, four different edge conditions of the embedded MWCNT are considered, two different models with regard to the van der Waals interaction between each pair of walls constituting the MWCNT are considered, and the interaction between the MWCNT and its surrounding medium is simulated using the Pasternak-type foundation. The motion equations of an individual wall and the associated boundary conditions are derived using Hamilton's principle, in which the von $K{\acute{a}}rm{\acute{a}}n$ geometrical nonlinearity is considered. Eringen's nonlocal elasticity theory is used to account for the effects of the small length scale. Variations of the lowest frequency parameters with the maximum modal deflection of the embedded MWCNT are obtained using the differential quadrature method in conjunction with a direct iterative approach.