• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.199-200
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• 2020

In this study, the effect of porous powders on the dispersibility and strength properties of CNTs was examined.As a result of the experiment, it was found that in the case of incorporation of CNT, the compressive strength property was significantly improved by improving the dispersibility of CNT.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.244-244
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• 2009

Carbon nanotubes (CNTs) have excellent electrical, chemical stability, mechanical and thermal properties. In this paper, networks of Multi-walled carbon nanotube (MWCNT) materials were investigated as transparent electrode. Sensor films were fabricated by air spray method using the multi-walled CNTs solution on glass substrates. The film that was sprayed with the MWCNT dispersion for 60 sec, was 300nm thick. And the electric resistivity and the light transmittance rate are $2{\times}10^2{\Omega}cm$ and 60%, respectively.

• 대한금속재료학회지
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• 제47권1호
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• pp.50-58
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• 2009

In this study, alumina matrix composites reinforced with carbon nanotubes (CNTs) were fabricated by ultrasonic dispersion, ball milling, mixing, compaction, and sintering processes, and their relative density, electrical resistance, hardness, flexure strength, and fracture toughness were evaluated. 0~3 vol.% of CNTs were relatively homogeneously dispersed in the composites in spite of the existence of some pores. The three-point bending test results indicated that the flexure strength increased with increasing volume fraction of CNTs, and reached the maximum when the CNT fraction was 1.5 vol.%. The fracture toughness increased as the CNT fraction increased, and the fracture toughness of the composite containing 3 vol.% of CNTs was higher by 40% than that of the monolithic alumina. According to observation of the crack propagation path after the indentation fracture test, a new toughening mechanism of grain interface bridging-induced CNT bridging was suggested to explain the improvement of fracture toughness in the alumina matrix composites reinforced with CNTs.

• 한국분말재료학회지
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• 제12권6호
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• pp.393-398
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• 2005

In-situ processing route was adopted to disperse carbon nanotubes (CNTs) into $Al_2O_3$ powders homogeneously. The $Al_2O_3$ composite powders with homogeneous dispersion of CNTs could be synthesized by a catalytic route for in-situ formation of CNTs on nano-sized Fe dispersed $Al_2O_3$ powders. CNTs/Fe/$Al_2O_3$ nanopowders were densified by spark plasma sintering (SPS). The hardness and bending strength as well as electrical conductivity increased with increasing sintering temperature. However, the electrical conductivity of the composites sintered at above $1500^{\circ}C$ showed decreased value with increasing sintering temperature due to the oxidation of CNTs.

• 한국분말재료학회지
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• 제20권5호
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• pp.345-349
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• 2013

Carbon nanotube-dispersed bismuth telluride matrix (CNT/$Bi_2Te_3$) nanopowders were synthesized by chemical routes followed by a ball-milling process. The microstructures of the synthesized CNT/$Bi_2Te_3$ nanopowders showed the characteristic microstructure of CNTs dispersed among disc-shaped $Bi_2Te_3$ nanopowders with as an average size of 500 nm in-plane and a few tens of nm in thickness. The prepared nanopowders were sintered into composites with a homogeneous dispersion of CNTs in a $Bi_2Te_3$ matrix. The dimensionless figure-of-merit of the composite showed an enhanced value compared to that of pure $Bi_2Te_3$ at the room temperature due to the reduced thermal conductivity and increased electrical conductivity with the addition of CNTs.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.426-429
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• 2006

We investigated the electrooptical properties of a carbon nanotube (CNT)-doped nematic liquid crystal (LC) cell. Experimental results reveal that the doped CNTs influence the elastic constant of LC-CNT dispersion. Using a small amount of CNT dopant, the rise time of the LC cell is nearly invariant; the threshold voltage of the cell increases due to the increase in the elastic constant of LC-CNT dispersion. At a higher CNT concentration, the marked increase in the dielectric anisotropy of LC-CNT dispersion markedly decreases the rise time and threshold voltage of the LC cell. The fall time of this cell decreases with increasing CNT concentration due to the increase in elastic constant and the slight increase in viscosity of LC-CNT dispersion. The rise time and the fall time of the LC cell are decreased simultaneously when the LC host is doped with a moderate amount of CNT dopant.

• Composites Research
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• 제29권5호
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• pp.269-275
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• 2016

Multiscale hybrid composites, which consist of polymeric resins, microscale fibers and nanoscale reinforcements, have drawn significant attention in the field of advanced, high-performance materials. Despite their advantages, multiscale hybrid composites show challenges associated with nanomaterial dispersion, viscosity, interfacial bonding and load transfer, and orientation control. In this paper, carbon nanotube(CNT)/carbon fiber(CF)/polycarbonate(PC) multiscale hybrid composite were fabricated by a solution process to overcome the difficulties associated with controlling the melt viscosity of thermoplastic resins. The dependence of CNT loading was studied by varying the method to add CNTs, i.e., impregnation of CF with CNT/PC/solvent solution and impregnation of CNT-coated CF with PC/solvent solution. In addition, hybrid composites were fabricated through surfactant-aided CNT dispersion followed by vacuum filtration. The morphologies of the surfaces of hybrid composites, as analyzed by scanning electron microscopy, revealed the quality of PC impregnation depends on the processing method. Dynamic mechanical analysis was performed to evaluate their mechanical performance. It was analyzed that if the position of the value of tan ${\delta}$ is closer to the ideal line, the adhesion between polymer and carbon fiber is stronger. The effect of mechanical interlocking has a great influence on the dynamic mechanical properties of the composites with CNT-coated CF, which indicates that coating CF with CNTs is a suitable method to fabricate CNT/CF/PC hybrid composites.

• Macromolecular Research
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• 제15권6호
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• pp.498-505
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• 2007

This study demonstrated the in-situ functionalization with polymers of multi-walled carbon nanotubes (MWNTs) via emulsion polymerization. Polystyrene-functionalized MWNTs were prepared in an aqueous solution containing styrene monomer, non-ionic surfactant and a cationic coupling agent ([2-(methacryloyloxy)ethyl]trime-thylammonium chloride (MATMAC)). This process produced an interesting morphology in which the MWNTs, consisting of bead-string shapes or MWNTs embedded in the beads, when polymer beads were sufficiently large, produced nanohybrid material. This morphology was attributed to the interaction between the cationic coupling agent and the nanotube surface which induced polymerization within the hemimicellar or hemicylindrical structures of surfactant micelles on the surface of the nanotubes. In a solution containing MATMAC alone without surfactant, carbon nanotubes (CNTs) were not well-dispersed, and in a solution containing only surfactant without MATMAC, polymeric beads were synthesized in isolation from CNTs and continued to exist separately. The incorporation of MATMAC and surfactant together enabled large amounts of CNTs (> 0.05 wt%) to be well-dispersed in water and very effectively encapsulated by polymer chains. This method could be applied to other well-dispersed CNT solutions containing amphiphilic molecules, regardless of the type (i.e., anionic, cationic or nonionic). In this way, the solubility and dispersion of nanotubes could be increased in a solvent or polymer matrix. By enhancing the interfacial adhesion, this method might also contribute to the improved dispersion of nanotubes in a polymer matrix and thus the creation of superior polymer nanocomposites.

• 한국전기전자재료학회논문지
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• 제24권8호
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• pp.682-685
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• 2011

An engine oil sensor based on multiwall carbon nanotubes was fabricated with screen printing method. Since carbon nanotubes are generally intertwined, dispersion of the carbon nanotubes in the binding agent (ethyl cellulose, a-terpineol, frit) is a key factor for large yield of engine oil sensor. By conventional dispersion method, a hand-mill method, the maximum yield was 80% at most. However, we used the hand ultrasonic, in order to increase the yield of the sensors. As a results, our engine oil sensor fabricated by the screen printing method shows excellent yield rate of 97%, when we dispersed a paste by the hand ultrasonic method.

• 한국태양에너지학회 논문집
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• 제29권5호
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• pp.35-44
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• 2009

In this study, boiling heat transfer coefficients(HTCs) and critical heat flux(CHF) are measured on a smooth square flat copper heater in a pool of pure water with and without carbon nano tubes(CNTs) dispersed at $60^{\circ}C$. Tested aqueous nanofluids are prepared using multi-walled CNTs whose volume concentrations are 0.0001, 0.001, 0.01, and 0.05%. For dispersion of CNTs, polyvinyl pyrrolidone(PVP) is used in distilled water. Pool boiling HTCs are taken from $10kW/m^2$ to critical heat flux for all nanofluids. Test results show that the pool boiling HTCs of the nanofluids are lower than those of pure water in entire nucleate boiling regime. On the other hand, critical heat flux is enhanced greatly showing up to 200% increase at volume concentration of 0.001% CNTs as compared to that of pure water. This is related to the change of surface characteristics by the deposition of CNTs. This deposition makes a thin CNT layer on the surface and the active nucleation sites of heat transfer surface are decreased due to this layer. The thin layer acts as the thermal resistance and also decreases the bubble generation rate resulting in a decrease in pool boiling HTCs. The same layer, however, maintains the nucleate boiling even at very high heat fluxes and reduces the formation of large vapor canopy at near CHF resulting in a significant increase in CHF.