• Carbon letters
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• v.5 no.1
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• pp.1-5
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• 2004

The effects of fiber surface-treatment and sizing on the dynamic mechanical properties of unidirectional and 2-directional carbon fiber/nylon 6 composites by means of dynamic mechanical analysis have been investigated in the present study. The interlaminar shear strengths of 2-directional carbon/nylon 6 composites sized with various thermosetting and thermoplastic resins are also measured using a short-beam shear test method. The result suggests that different surface-treatment levels onto carbon fibers may influence the storage modulus and tan ${\delta}$ behavior of carbon/nylon 6 composites, reflecting somewhat change of the stiffness and the interfacial adhesion of the composites. Dynamic mechanical analysis and short-beam shear test results indicate that appropriate use of a sizing material upon carbon fiber composite processing may contribute to enhancing the interfacial and/or interlaminar properties of woven carbon fabric/nylon 6 composites, depending on their resin characteristics and processing temperature.

• Ceramist
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• v.23 no.2
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• pp.114-131
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• 2020

Fracture in the titanium carbonitride-metal composites occurs by crack propagation through the carbonitride grains or in the interfaces. Thus, intrinsic properties of the carbonitride need to be enhanced and the interfaces should be also modified to coherent structure to strengthen the composites. Especially, interfacial structure can be the main factor to determine the mechanical properties of titanium carbonitride-metal composites because the interfaces between carbonitride grains and metallic phase are weak parts due to heterogeneous nature of carbonitride and metallic phase. In this paper, methodologies for improving the interfacial structure of titanium carbonitride-metal composites are suggested. Total area of the interfaces can be reduced using solid solution type carbonitrides as raw materials instead of a mixture of various carbonitrides in the composites. Also, synthesis of titanium carbonitride-metal composite powders and the low-temperature sintering of the composite powders for short time can be the way for formation of coherent interfaces. The sintering of the composite powders for short time at low temperature can reduce the potential of formation of interfaces by dissolution and precipitation of carbonitride in the liquid metal. As a result of formation of coherent boundaries due to low-temperature and short-time sintering, interfaces between titanium carbonitride grains and metallic phase have the favorable structure for the enhanced fracture toughness. It is believed that the low-temperature sintering of solid solution type composite powders for short time can be the way to improve the low toughness of the titanium carbonitride-metal composites.

• Journal of Mechanical Science and Technology
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• v.16 no.11
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• pp.1477-1484
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• 2002

Various characteristics of a thin liquid film in its vapor-phase are investigated using the molecular dynamics technique. Local distributions of the temperature, density, normal and tangential pressure components, and stress are calculated for various film thicknesses and temperature levels. Distributions of local stresses change considerably with respect to film thicknesses, and interracial regions on both sides of the film start to overlap with each other as the film becomes thinner. Integration of the local stresses, i.e., the surface tension, however, does not vary much regardless of the interfacial overlap. The minimum thickness of a liquid film before rupturing is estimated with respect to the calculation domain sizes and is compared with a simple theoretical relation.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.938-940
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• 1998

In order to improve insulating character and ability of insulating system of power apparatus, the interfacial and complex structure is widely used. However, the interface or complex structure of insulation materials is reported as a weak point which causes breakdown. As the interface of insulation system degrades its electrical property and eventually causes a failure, the datailed phenomenon analysis is reported. The object of this paper is to evaluate dielectric property of PET film with the interface. The $tan{\delta}$ increased with the existence of semiconducting layer and showed prominent decrease as a function of temperature. Also, the $tan{\delta}$ showed prominent increase as a function of frequency. The dielectric properties of interfacial were affected by the interface characteristics.

• Journal of the Korean Ceramic Society
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• v.37 no.2
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• pp.128-133
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• 2000

In this work, soft carbons produced by pyrolysis of petroleum and coal-tar pitch were used as the negative electrode for Li-ion batteries. We studeid the charge/discharge capacity and the interfacial reaction of these electrodes by constructing a half cell. Charge/discharge property was studied by a constant-current step and the interfacial reaction between the electrolyte and the surface of a carbon electrode was studied by the cyclic voltammetry. The initial charge/discharge capacity for the coal-tar pitch carbon increased exceedingly with the heat treatment temperature. On hte other hand, the capacity of the petroleum pitch carbon increased with temperature up to 1000$^{\circ}C$, thereafter decreased continuously. While the charge capacity decreased with the cycle number, the reversibility increased above 90%. In addition, the thermal stability and crystallization of petroleum and coal-tar pitches were analyzed by TGA and XRD, respectively.

• Transactions of Materials Processing
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• v.8 no.3
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• pp.289-289
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• 1999

This paper describes the investment casting of TiAl alloys. The effects of mold material and mold preheating temperature for the investment casting of TiAl on metal-mold interfacial reaction were investigated by means of optical micrography, hardness profiles and an electron probe microanalyzer. The mold materials examined were colloidal silica bonded ZrO₂, ZrSiO₄, A1₂O₃and CaO stabilized ZrO₂. When compared with conventional titanium a1loy, the high aluminum concentration of TiAl alloys helps to lower their reactivity in the molten state. The A1₂O₃mold is a promising mold material for the investment casting of TiAl in terms of the thermal stability, formability and cost. Special attention need to be paid to thermal stability and mold preheating when developing the investment calling of TiAl alloys.

• Nuclear Engineering and Technology
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• v.32 no.5
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• pp.521-529
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• 2000

A modified interfacial heat transfer correlation between a dispersed water droplet and ambient superheated steam is proposed and compared with available experimental data and other correlations. Modified one overcomes the inherent deficiencies of Lee and Ryley's interfacial heat transfer correlation that ignored the effects of steam superheating which can not be neglected especially in the reflood situation of a loss-of-coolant accident. Modified one is represented by (equation omitted) In the present correlation the effect of possible subcooling of a water droplet is not taken into consideration. Comparison of the above correlation with currently available measurement data for a water droplet in high temperature gas flow shows that the proposed one correlates well with the measurement data where the degree of superheating is negligible and considerable.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.6
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• pp.284-289
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• 2020

Since the dissimilar bonded interface usually consists of intermetallic compounds (IMCs) layer and cracks, their mechanical and electrical properties can be influenced by microstructure at interface between two different metals. In this study, the friction welded Cu-Al busbar, which is widely used to connect a secondary battery and their component, is selected to analyze the influence of interfacial characteristic on their tensile strength and electric conductivity. Then, the electrical characteristics of Cu busbar and Cu-Al busbar were investigated by thermal flow analysis and temperature rise test. In addition, the relationship between the maximum saturation temperature and the electrical conductivity were discussed in terms of interfacial characteristics of the friction welded Cu-Al busbar.

• Korean Journal of Materials Research
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• v.13 no.8
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• pp.497-502
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• 2003

Crystallographic characteristics and interfacial structures of $Al_2$$O_3$and $ZrO_2$dielectric films prepared by atomic layer chemical vapor deposition (ALCVD) were investigated at atomic scale by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS)/electron energy-loss spectroscopy (EELS) coupled with a field-emission transmission electron microscope. The results obtained from cross-sectional and plan-view specimens showed that the $Al_2$$O_3$film was crystallized by annealing at a high temperature and its crystal system might be evaluated as either cubic or tetragonal phase. Whereas the $ZrO_2$film crystallized during deposition at a low temperature of ∼$300^{\circ}C$ was composed of both tetragonal and monoclinic phase. The interfacial thickness in both films was increased with the increased annealing temperature. Further, the interfacial structures of X$ZrO_2$$O_3$and $ZrO_2$films were discussed through analyses of EDS elemental maps and EELS spectra obtained from the annealed films, respectively.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.11a
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• pp.51-51
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• 2004