• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1535-1536
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• 2013

• Carbon letters
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• v.7 no.3
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• pp.196-200
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• 2006

Graphite has hexagonal closed packing structure with two bonding characteristics of van der Waals bonding between the carbon layers at c axis, and covalent bonding in the carbon layer at a and b axis. Graphite has high tolerant to the extreme conditions of high temperature and neutron irradiations rather than any other materials of metals and ceramics. However, carbon elements easily react with oxygen at as low as 400C. Considering the increasing production of today of hydrogen and electricity with a nuclear reactor, study of oxidation characteristics of graphite is very important, and essential for the life evaluation and design of the nuclear reactor. Since the oxidation behaviors of graphite are dependent on the shapes of testing specimen, critical care is required for evaluation of nuclear reactor graphite materials. In this work, oxidation rate and amounts of the isotropic graphite (IG-110, Toyo Carbon), currently being used for the Koran nuclear reactor, are investigated at various temperature. Oxidation process or principle of graphite was figured out by measuring the oxidation rate, and relation between oxidation rate and sample shape are understood. In the oxidation process, shape effect of volume, surface area, and surface to volume ratio are investigated at $600^{\circ}C$, based on the sample of ASTM C 1179-91.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.89-94
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• 2021

The mechanical reliability of flexible devices has become a major concern on their commercialization, where the importance of reliable bonding is highlighted. In terms of component materials' properties, it is important to consider thermal damage of polymer substrates that occupy large area of the flexible device. Therefore, room temperature bonding process is highly advantageous for implementing flexible device assemblies with mechanical reliability. Conventional epoxy resins for the bonding still require curing at high temperatures. Even after the curing procedure, the bonding joint loses flexibility and exhibits poor fatigue durability. To solve this problems, low-temperature and adhesive-free bonding are required. In this work, we develop a room temperature bonding process for polymer substrates using carbon nanotube heated by microwave irradiations. After depositing multiple-wall carbon nanotubes (MWNTs) on PET polymer substrates, they are heated locally with by microwave while the entire bonding specimen maintains room temperature and the heating induces mechanical entanglement of CNT-PET. The room temperature bonding was conducted for a PET/CNT/PET specimen at 600 watt of microwave power for 10 seconds. Thickness of the CNT bonding joint was very thin that it obtains flexibility as well. In order to evaluate the mechanical reliability of the joint specimen, we performed lap shear test, three-point bending test, and dynamic bending test, and confirmed excellent joint strength, flexibility, and bending durability from each test.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.9
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• pp.718-723
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• 2010

In this paper, the following results were obtained from the experiment in which electrification voltage of silicone rubber specimen for thermal bonding were measured under various time, temperature ($10{\sim}40^{\circ}C$), and humidity (30~90%) conditions and different amount of carbon additives (0~15 phr (per hundred resin)). Electrostatics electrification voltage decreased when carbon is up to 10 phr, and there was no electrification voltage in 15 phr condition. The electrostatics electrification voltage did not change over time. When the temperature was constant, electrostatics electrification voltage sharply dropped when the humidity was around 70%. That means, this condition might be appropriate for prevention of charging. The electrification voltage decreased as humidity and amount of carbon increased.

• Tribology and Lubricants
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• v.21 no.6
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• pp.302-305
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• 2005

Various carbon nanotubes (CNTs) are added into the epoxy matrix as reinforcements to investigate the effect on the wear behavior. Effects to the tribological properties of different loading concentrations and types of surface modification are investigated by using a linear reciprocal wear tester. As increasing the concentration of CNTs shows the reduction of the wear loss. Moreover, surface modified CNTs give better tribological property than as produced CNTs. It is due that the functional groups on the surface of CNTs increase the interfacial bonding between CNTs and epoxy matrix through chemical bonding. Changes in worn surface morphology are observed by optical microscope and SEM to investigate the wear behavior. CNTs in the epoxy matrix near the surface are exposed and it becomes the lubricating working film on the worn surface. It reduces the friction and results in the lower surface roughness morphology in the epoxy matrix as increasing the contents of the CNTs.

• Advances in materials Research
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• v.6 no.3
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• pp.245-255
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• 2017

High energy ball milling is employed to produce iron matrix- multiwall carbon nanotube (MWCNT) reinforced composite. The damage caused to MWCNT due to harsh ball milling condition and its influence on interfacial bonding is studied. Different amount of MWCNT is used to find the optimal percentage of MWCNT for avoidance of the formation of chemical reaction product at the matrix - reinforcement interface. Effect of process control agent is assessed by the use of different materials for the purpose. It is observed that ethanol as a process control agent (PCA) causes degradation of MWCNT reinforcements after milling for two hours whereas solid stearic acid used as process control agent, allows satisfactory conservation of MWCNT structure. It is further noted that at a high MWCNT content (~ 2wt.%), high energy ball milling leads to reaction of iron and carbon and forms iron carbide (cementite) at the iron-MWCNT interface. At low percentage of MWCNT, dissolution of carbon in iron takes place and the amount of reinforcement in iron matrix composite becomes negligibly small. However, under the present ball milling condition (ball to metal ratio~ 6:1 and 200 rpm vial speed) iron-1wt.% MWCNT composite of good interfacial bonding can retain the tubular structure of reinforcing MWCNT.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.913-916
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• 1999

Recent developments of carbon nanotubes are reviewed［1,2,3,4］. We use Tersoff carbon potential for bonded interactions［5］ and Lennard-Jones 12-6 potential for non bonding interactions［6］to describe mechanical properties of the temperature-dependent armchair single wall carbon nanotube. At first we report that through defect number and bonding energy calculation, how single wall carbon nanutube is capped in the constant temperature. (300K, 2000K, 3000K, 4000K) At second, we perform MD simulation, which are performed on the energy optimized structure of carbon nanotube.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.88-91
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• 2004

It is generally known that the bonding strength of RC(Reinforced Concrete) flexural members strengthened by fiber sheet composites are sufficient and the bonding failure does not occur until the sheet failed. However, many researchers have been reported that, before the failure of the sheet, the bonding failure happens even though the bonding length is sufficient. This study was carried out to evaluate the effectiveness of shear key and U strip on flexural behavior of reinforced concrete beam structures. The ply number of CFS(Carbon Fiber Sheet), location of shear key, and existence or not of U strip were selected as the main test variables. Test results show that the behavior of a beam of which shear key is located in the nearby. of support and U strip is not existent, and having CFS of 1 ply is mostly improved.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1092-1095
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• 2005

The effect of the dielectric constant (${\varepsilon}$) of bonding materials in screen-printed carbon nanotube cathode on field enhancement factor was investigated using the ANSYS software for high-efficient CNT-cathodes. The field enhancement factor increased with decreasing the dielectric constant and reaching a maximum value when the dielectric constant is 1, the value for a vacuum. This indicates that the best bonding materials for screen-printing CNT cathodes should have a low dielectric constant and this can be used as criteria for selecting bonding materials for use in CNT pastes for high-efficient CNT-cathodes

• Carbon letters
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• v.15 no.4
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• pp.282-289
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• 2014

Blends of poly(vinyl alcohol) (PVA), polyethyleneimine (PEI), and graphene oxide (GO) were prepared by solution casting method. Calorimetric thermal properties of the blends were investigated. The $T_gs$ of PVA/PEI blends were higher than the $T_gs$ of either of the component polymers at low concentrations of PEI. These abnormal increases of $T_gs$ may be due to the negative entropy of mixing which is associated with strong hydrogen bonding between PVA and PEI. The degree of depression of $T^0_ms$ was not reduced by the negative entropy of mixing, since strong hydrogen bonding also causes an increase in the magnitude of negative ${\chi}$ between PVA and PEI. The $T_g$ of PVA was increased significantly by adding 0.7 wt.% GO into PVA. The magnitude of negative ${\chi}$ was increased by adding GO into the blends of PVA and PEI.