• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.27.2-27.2
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• 2009

Grinding characteristics for aluminium and carbon nanotubes (CNTs) powder during traditional and planetary ball milling investigated from the viewpoint of particle behaviour with the aimat developing CNT-dispersed samples ground based on powder metallurgy routes.In this work, a comparison between the pure aluminium and CNT input aluminium grinding was carried out to determine grinding time effect on size reduction.We observed that the use of the curly small-diameter multi-walled carbon nanotubes (MWCNTs) attributed to the beneficial role of the MWCNTs as grinding aids. It is suggested that careful choices of the sizes of CNTs and Al powders would allow fine-grinding of composite particles with uniformly distributed CNT reinforcements thereby ensuring improved properties of the final composites produced by low-temperature compacting.

• Transactions on Electrical and Electronic Materials
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• 제14권3호
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• pp.125-129
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• 2013

Composites of platinum and multiwalled carbon nanotubes (MWNTs) were prepared in various reduction conditions and characterized using cyclic voltammetry. The MWNTs were functionalized with carboxylic acid and/or hydroxyl groups in acidic solutions prior to the formation of MWNT-Pt composites. Platinum nanoparticles were deposited onto the chemically-oxidized MWNTs in 1-propanol and 1,3-propanediol. The reduction of Pt precursors in other solutions could induce differences in their morphologies in composite thin films. The morphologies of MWNTs with Pt deposited were dependent on the reduction solutions, and the electrocatalytic activities on alcohols changed accordingly. The electrochemical activities of the as-prepared MWNT-Pt thin films on common alcohols such as methanol and ethanol were investigated.

• Computers and Concrete
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• 제27권2호
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• pp.111-130
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• 2021

In the present work, an extensive study for predicting efficiency parameters (��i) of various simulated nanocomposites including Polymethyl methacrylate (PMMA) as matrix and different structures including various sizes of graphene platelets (GPLs), single, double, and multi-walled carbon nanotubes (SWCNTs-DWCNTs-MWCNTs), and single and double-walled boron nitride nanotubes (SWBNNTs-DWBNNTs) are investigated. It should be stated that GPLs, carbon and boron nitride nanotubes (CNTs, BNNT) with different chiralities (5, 0), (5, 5), (10, 0), and (10, 10) as reinforcements are considered. In this research, molecular dynamics (MDs) method with Materials studio software is applied to examine the mechanical properties (Young's modulus) of simulated nanocomposite boxes and calculate η1 of each nanocomposite boxes. Then, it is noteworthy that by changing length (6.252, 10.584, and 21.173 nm) and width (7.137, 10.515, and 19.936) of GPLs, ��1, ��2, and ��3 approximately becomes (0.101, 0.114, and 0.124), (1.15, 1.22, and 1.26), (1.04, 1.05, and 1.07) respectively. After that efficiency parameters of SWCNTs, DWCNTs, and MWCNTs are calculated and discussed separately. Finally efficiency parameters of SWBNNTs and DWBNNTs with different chiralities by PMMA as matrix are determined by MD and discussed separately. It is known that the accurate efficiency parameters helps a lot to calculate the properties of nanocomposite analytically. In particular, the obtained results from this research can be used for analytical work based on the extended rule of mixture (ERM) in bending, buckling and vibration analysis of structure in future study.

• Composites Research
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• 제23권3호
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• pp.7-12
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• 2010

탄소섬유 복합재료의 전기전도도와 기계적 강도를 높이기 위하여 음극 및 양극 전기영동법을 이용하여 탄소나노튜브(MWCNT)와 탄소나노섬유(CNF)를 탄소섬유직물에 부착하였다. 양극 전기영동에서는 MWCNT와 CNF의 탄소나노 입자들만이 탄소 섬유에 부착되었으나, 음극 전기영동에서는 MWCNT와 CNF 및 나노 크기의 구리 입자가 동시에 탄소섬유직물에 부착되었고 이에 따라 부착 밀도 및 복합재료 물성의 증대라는 시너지 효과를 거둘 수 있었다. 특히 나노 크기의 탄소나노입자 및 마이크로 크기의 탄소 섬유가 혼합된 멀티스케일 복합재료의 제조를 통해 두께 방향 전기전도도의 높은 향상을 얻었다. 또한 MWCNT와 CNF를 동시에 멀티스케일 복합재료에 적용하였을 경우, 각각을 적용한 경우보다 두께 방향 전기전도도가 높게 나타났다.

• Computers and Concrete
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• 제25권2호
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• pp.133-144
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• 2020

This paper aims to study vibration characteristics of chiral and zigzag double-walled carbon nanotubes entrenched on Donnell shell model. The Eringen's nonlocal elastic equations are being combined with Donnell shell theory to observe small scale response. Wave propagation is proposed technique to establish field equations of model subjected to four distinct end supports. A nonlocal model has been formulated to explore the frequency spectrum of both chiral and zigzag double-walled CNTs along with diversity of indices and nonlocal parameter. The significance of scale effect in relevance of length-to-diameter and thickness- to- radius ratios are discussed and displayed in detail. The numerical solution based on this nonlocal Donnell shell model can be further used to predict other frequency phenomena of double-walled and multi-walled CNTs.

• 한국환경과학회지
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• 제25권4호
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• pp.505-516
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• 2016

With the development of nanotechnology, nanomaterials are used in various fields. Therefore, the interest regarding the safety of nanomaterial use is increasing and much effort is diverted toward establishment of exposure assessment and management methods. Occupational exposure limits (OELs) are effectively used to protect the health of workers in various industrial workplaces. This study aimed to propose an OEL for domestic multi-walled carbon nanotubes (MWCNTs) based on animal inhalation toxicity test. Basic procedure for development of OELs was examined. For OEL estimation, epidemiological study and quantitative risk assessment are generally performed based on toxicity data. In addition, inhalation toxicity data-based no observed adverse effect level (NOAEL) and benchmark dose (BMD) are estimated to obtain the OEL. Three different estimation processes (NEDO in Japan, NIOSH in USA, and Baytubes in Germany) of OELs for carbon nanotubes (CNTs) were intensively reviewed. From the rat inhalation toxicity test for MWCNTs manufactured in Korea, a NOAEL of $0.98mg/m^3$ was derived. Using the simple equation for estimation of OEL suggested by NEDO, the OEL of $142{\mu}g/m^3$ was estimated for the MWCNT manufacturing workplace. Here, we used test rat and Korean human data and adopted 36 as an uncertainty factor. The OEL for MWCNT estimated in this work is higher than those ($2-80{\mu}g/m^3$) suggested by previous investigators. It may be greatly caused by different physicochemical properties of MWCNT and their dispersion method and test rat data. For setting of regulatory OELs in CNT workplaces, further epidemiological studies in addition to animal studies are needed. More advanced technical methods such as CNT dispersion in air and liquid should be also developed.

• Carbon letters
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• 제12권1호
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• pp.48-52
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• 2011

The conducting polymer-coated multi-walled carbon nanotubes (MWCNTs) were prepared by template polymerization of aniline and pyrrole on the surface of MWCNTs in order to develop the novel electromagnetic interference (EMI) shielding materials. The conducting polymer phases formed on the surface of MWCNTs were confirmed by field emission-scanning electron microscopy and field emission-transmission electron microscopy. Both permittivity and permeability were significantly improved for the conducting polymer-coated MWCNTs due to the intrinsic electrical properties of MWCNTs and the conducting properties of coated polymers. The electromagnetic waves were effectively absorbed based on the permittivity nature of conducting polymer and MWCNTs preventing the secondary interference from reflecting the electromagnetic waves. The highly improved EMI shielding efficiency was also obtained for the conducting polymer-coated MWCNTs showing the synergistic effects by combining MWCNTs and the conducting polymers.

• Carbon letters
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• 제15권1호
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• pp.32-37
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• 2014

Multi-walled carbon nanotube (MWCNT)/epoxy composites are prepared by a vacuum assisted resin transfer molding (VARTM) method. The mechanical properties, fracture surface morphologies, and thermal stabilities of these nanocomposites are evaluated for epoxy resins with various amounts of MWCNTs. Composites consisting of different amounts of MWCNTs displayed an increase of the work of adhesion between the MWCNTs and the matrix, which improved both the tensile and impact strengths of the composites. The tensile and impact strengths of the MWCNT/epoxy composite improved by 59 and 562% with 0.3 phr of MWCNTs, respectively, compared to the epoxy composite without MWCNTs. Thermal stability of the 0.3 phr MWCNT/epoxy composite increased compared to other epoxy composites with MWCNTs. The enhancement of the mechanical and thermal properties of the MWCNT/epoxy nanocomposites is attributed to improved dispersibility and strong interfacial interaction between the MWCNTs and the epoxy in the composites prepared by VARTM.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1137-1144
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• 2013

$TiO_2$ composites with seven different carbon materials (activated carbons, graphite, carbon fibers, single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene oxides, and reduced graphene oxides) that are virgin or treated with nitric acid are prepared through an evaporation method. The photocatalytic activities of the as-prepared samples are evaluated in terms of $H_2$ production from aqueous methanol solution (photo-catalytic reduction: PCR) and degradation of aqueous pollutants (phenol, methylene blue, and rhodamine B) (photocatalytic oxidation: PCO) under AM 1.5-light irradiation. Despite varying effects depending on the kinds of carbon materials and their surface treatment, composites typically show enhanced PCR activity with maximum 50 times higher $H_2$ production as compared to bare $TiO_2$. Conversely, the carbon-induced synergy effects on PCO activities are insignificant for all three substrates. Colorimetric quantification of hydroxyl radicals supports the absence of carbon effects. However, platinum deposition on the binary composites displays the enhanced effect on both PCR and PCO reactions. These differing effects of carbon materials on PCR and PCO reactions of $TiO_2$ are discussed in terms of physicochemical properties of carbon materials, coupling states of $TiO_2$/carbon composites, interfacial charge transfers. Various surface characterizations of composites (UV-Vis diffuse reflectance, SEM, FTIR, surface area, electrical conductivity, and photoluminescence) are performed to gain insight on their photocatalytic redox behaviors.

• 한국정밀공학회지
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• 제24권3호
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• pp.134-139
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• 2007

We report the suspension of individual multi-walled carbon nanotubes (MWNTs) from the bottom substrate using deep trench electrodes that were fabricated using optical lithography. During drying of the solution in dielectrophoretic assembly, the capillary force pulls the MWNT toward the bottom substrate, and it then remains as a deformed structure adhering to the bottom substrate after the solution has dried out. Small-diameter MWNTs cannot be suspended using thin electrodes with large gaps, but large-diameter MWNTs can be suspended using thicker electrodes. We present the statistical experimental results for successful suspension, as well as the feasible conditions for a MWNT suspension based on a theoretical approach.