• Elastomers and Composites
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• v.56 no.3
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• pp.179-186
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• 2021

Carbon-based nanofillers, including nanodiamond (ND) and carbon nanotubes (CNTs), have been employed in epoxy matrixes for improving the toughness, using the tow prepreg method, of epoxy compounds for high pressure tanks. The reinforcing performance was compared with those of commercially available toughening fillers, including carboxyl-terminated butadiene acrylonitrile (CTBN) and block copolymers, such as poly(methyl methacrylate)-b-poly(butyl acrylate)-b-poly(methyl methacrylate) (BA-b-MMA). CTNB improved the mechanical performance at a relatively high filler loading of ~5 phr. Nanosized BA-b-MMA showed improved performance at a lower filler loading of ~2 phr. However, the mechanical properties deteriorated at a higher loading of ~5 phr because of the formation of larger aggregates. ND showed no significant improvement in mechanical properties because of aggregate formation. In contrast, surface-treated ND with epoxidized hydroxyl-terminated polybutadiene considerably improved the mechanical properties, notably the impact strength, because of more uniform dispersion of particles in the epoxy matrix. CNTs noticeably improved the flexural strength and impact strength at a filler loading of 0.5 phr. However, the improvements were lost with further addition of fillers because of CNT aggregation.

• Journal of Environmental Science International
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• v.25 no.4
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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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.37-43
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• 2019

This study investigated electrical conductivity, electromagnetic shielding effectiveness, and mechanical property to improve electromagnetic shielding performance of high performance fiber reinforced cementitious composites (HPFRCC). Steel fiber, steel slag and carbon black as a conductive material were incorporated into the HPFRCC mixes. In addition, 2% CNT solution which was produced by dispersing multi-wall carbon nanotube (MWCNT) into water was used as a conductive material. In the test results, electrical conductivity of HPFRCC specimens was very low except for the specimen incorporating 1% carbon black. Micro structure of cement matrix was changed as the curing time increased, which negatively affected the conductive network of HPFRCC. In case of HC1 specimen showing a conductive network (0.083 S/cm), the electrical conductivity of the specimen after being dried at $60^{\circ}C$ for 72 hours to exclude the effect of water on electrical conductivity was significantly reduced to 0.0003 S/cm. The most important parameter of electromagnetic shielding effect was found to be a steel fiber while the effect of carbon black and steel slag was very few. The correlation between electrical conductivity and electromagnetic shielding effect does not seem to be clear.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.303-304
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• 2002

32"-diagonal gated carbon nanotube(CNT) cathodes named under-gate cathodes for large-size display applications have been fabricated and characterized. The emission uniformity looks fine, even without the resistive layer. The emission performance has been improved by scaling down the cathode electrode dimension.

• Journal of the Korean GEO-environmental Society
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• v.18 no.11
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• pp.35-40
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• 2017

The rearside of concrete lining of tunnels constructed in cold region might experience on freezing due to the low temperature. This causes damage of concrete lining resulting in adverse affect on the durability as well as integrity of tunnel structure by causing damage to the concrete lining. In order to prevent the rearside of tunnel lining from freeing, the temperature change inside the concrete lining was measured by attaching a heating element to the tunnel lining surface and generating heat for a certain period of time. A special freezing chamber was developed to conduct the experiments considering in-situ environment. The carbone nanotube (CNT) was used as a heating element in this study. The temperature distribution of the concrete lining was measured by applying the heat to the heating element. The effect of the outside temperature and heating duration were analyzed.

• Composites Research
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• v.30 no.4
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• pp.235-240
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• 2017

Animal glue, a water-soluble adhesive, has been used historically for high-performance traditional furniture despite the disadvantage of weakness against moisture. Many scientists studied the ways to improve water resistance of animal glue. Improvements on the interfacial, thermal, and water resistance properties of wood sandwich composites (WSC) was studied with carbon nanotube (CNT) wt% in animal glue. Real-time temperature of WSC was measured after WSC was heated with increasing CNT wt%. Lap shear test was performed to determine the interfacial properties of wood and animal glue with CNTs. Water resistance properties of animal glue were determined by lap shear test using specimens dipped in water and the results were compared with the dry case. Hydrophobicity of animal glue by static contact angle was correlated with the variation of lap shear test. Interfacial, thermal, and water resistance properties for animal glue were improved with properly added CNTs.

• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.291-297
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• 2007

The field emission properties of CNT-emitters coated with Ag-Cu alloy have been investigated. The vertical aligned multi-walled CNTs were synthesized by dc-plasma enhanced chemical vapor deposition (dc-PECVD) and the Ag-Cu alloy was coated by using dc-magnetron sputter. The morphology of alloy-coated and un-coated CNT-emitters was observed by using SEM and their field emission properties were also measured. Annealing the AgCu-coated CNTs at temperature more than ${\sim}700^{\circ}C$, the Ag-Cu alloy was diffused to and aggregated on the top of the CNT as a Q-tip. A significant progress on the field emission was not observed with coating Ag-Cu alloy on the CNTs, but a certain improvement in a resistance against oxygen gas was made confirmation. It seems to be due to inertness of Ag-Cu alloy on the CNTs.

• Korean Journal of Materials Research
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• v.22 no.3
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• pp.130-135
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• 2012

We present a method of graphene synthesis with high thickness uniformity using the thermal chemical vapor deposition (TCVD) technique; we demonstrate its application to a grid supporting membrane using transmission electron microscope (TEM) observation, particularly for nanomaterials that have smaller dimensions than the pitch of commercial grid mesh. Graphene was synthesized on electron-beam-evaporated Ni catalytic thin films. Methane and hydrogen gases were used as carbon feedstock and dilution gas, respectively. The effects of synthesis temperature and flow rate of feedstock on graphene structures have been investigated. The most effective condition for large area growth synthesis and high thickness uniformity was found to be $1000^{\circ}C$ and 5 sccm of methane. Among the various applications of the synthesized graphenes, their use as a supporting membrane of a TEM grid has been demonstrated; such a grid is useful for high resolution TEM imaging of nanoscale materials because it preserves the same focal plane over the whole grid mesh. After the graphene synthesis, we were able successfully to transfer the graphenes from the Ni substrates to the TEM grid without a polymeric mediator, so that we were able to preserve the clean surface of the as-synthesized graphene. Then, a drop of carbon nanotube (CNT) suspension was deposited onto the graphene-covered TEM grid. Finally, we performed high resolution TEM observation and obtained clear image of the carbon nanotubes, which were deposited on the graphene supporting membrane.

• Journal of Information Display
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• v.9 no.4
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• pp.30-34
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• 2008

Field emitter arrays (FEAs) were developed using carbon nanotubes (CNTs) as electron emission sources. The CNTs were grown using a selective-positioning technique with a resist-protection layer. The light emission properties were studied through the electron emission of the CNTs on patterned islands, which were modulated with island diameter and spacing. The electron emission of CNT arrays with $5{\mu}m$ diameters and $10{\mu}m$ heights increased with increased spacing (from $10{\mu}m$ to $40{\mu}m$). The electron emission current of the $40-{\mu}m$-island-spacing sample showed a current density of 1.33 mA/$cm^2$ at E = 11 V/${\mu}m$, and a turn-on field of 7 V/${\mu}m$ at $1{\mu}A$ emission current. Uniform electron emission current and light emission were achieved with $40{\mu}m$ island spacing and $5{\mu}m$ island diameter.

• Journal of the Korean Ceramic Society
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• v.39 no.5
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• pp.467-472
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• 2002

Long Carbon Nanotubes(CNTs) were cut by diamond lapping film followed by observation using SEM. The paste was prepared by mixing shortened CNT powder, ${\alpha}$-terpineol used as a solvent, and ethylcellulose as a binder. This paste was deposited on glass substrate by screen printing and extruded by syringe. After screen printing, several post-treatments were performed to control the alignment of CNTs perpendicular to the substrate. The deposited CNTs were scratched by sand paper or diamond lapping film. It was also treated by attachment followed by an immediate detachment using the adhesive tape. SEM observation indicates that excellent vertical alignment of CNTs could be achieved by simple post-treatments from the screen printed-CNTs paste. Similar alignment of CNTs is also observed in the as-extruded CNTs paste.