• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.332-335
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• 2012

A molded transformer is maintenance-free, which makes it unnecessary to replace the insulating material, like in an oil-filled transformer, because the epoxy, which is a molded insulating resin, does not suffer variations in its insulating performance for heat cycles over a long time, as compared to insulating oil. In spite of these advantages, a molded transformer may still be accessed by the user, which is not good in regards to reliability or noise compared to the oil transformers. In particular, a distrust exists regarding reliability due to the long-term insulating performance. These properties have been studied in regards to the improvement of epoxy composites and molded transformer insulation. There have nevertheless been insufficient investigations into the insulation properties of epoxy composites. In this study, it is a researching of the epoxy for insulating material. In order to prepare the specimens, a main resin, a hardener, an accelerator, and a nano/micro filler were used. Varying amounts of TiO2 and ZnO nano fillers were added to the epoxy mixture along with a fixed amount of micro silica. This paper presents the DC insulation breakdown test, thermal expansion coefficient, and thermal conductivity results for the manufactured specimens. From these results, it has been found that the insulating performance of nano/micro epoxy composites is improved as compared to plain molded transformer insulation, and that nano/micro epoxy composites contribute to the reliability and compactness of molded transformers.

• Carbon letters
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• v.8 no.2
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• pp.115-119
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• 2007

Properties of carbon blacks and carbon black/SBR rubber composites filled by surface modified carbon blacks were examined. Although the specific surface area of carbon blacks increased after the surface modifications with heat, acid, and base, there were no obvious changes in resistivity. The composites filled by heat treated carbon blacks showed a higher tensile strength and elongation than those filled by raw blacks. The acid and base treated carbon blacks filled composites also showed higher tensile strength but similar elongation values with those filled by raw blacks. With increasing loading ratio, both tensile strength and elongation increased, and appeared a maximum value at 30-40 phr. Modulus at 300% strain remained increasing with further loading of carbon blacks. At the same loading, the heat treated black filled composites showed similar modulus values with composites filled by raw blacks but for base and acid treated black filled composites much higher values were obtained. After the surface modification, the functional groups which played an important role in reinforcement action were changed.

• Transactions on Electrical and Electronic Materials
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• v.13 no.3
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• pp.116-120
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• 2012

In this paper, ZnO-Epoxy nanocomposites (NEP) were prepared and epoxy composites that contain 5 wt% micro ZnO (MEP) and deliberately not well dispersed nano ZnO (NDNEP) were also prepared for purpose of comparison. The effects of the particle size and dispersion of ZnO on dielectric properties of epoxy resin were chiefly studied. Test results showed that: at a loading of 5 wt%, the three epoxy composites seem to have no significant difference on resistivity compared to epoxy resin; Dielectric constants of all the epoxy composites are also basically the same but they are bigger compared to that of the pure epoxy resin (unfilled); Dielectric dissipation factors ($tan{\delta}$) of NDNEP is greater than that of NEP and MEP. NEP has the minimum dielectric loss factor, whereas dielectric loss factors of the three epoxy composites are larger than that of the pure epoxy resin. The decreasing order of electrical breakdown strength for the three epoxy composites and for the pure epoxy resin is as follows: NEP>MEP>NDNEP>EP. Finally, in order to explain the experimental results the aggregation interface phase was proposed. Furthermore, addition of well dispersed nano filler has proved to have a positive effect on the improvement of the dielectric properties of epoxy resin.

• Composites Research
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• v.26 no.6
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• pp.337-342
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• 2013

The good dispersion of nano-materials in epoxy matrix was important parameter for the reinforcement effect, and the evaluation of dispersion degree was to prove it. This work was studied to predict the dispersion condition of nano-SiC powders in SiC/epoxy composites using capacitance measurement. Capacitance was defined to be the electric capacity in proportional to electron charge of the measuring section. In case of nano-SiC powders, the electron charge of SiC/epoxy composites was higher than that of neat epoxy resin. Capacitance was evaluated for each section of SiC/epoxy composites. The prediction of dispersion condition was verified by using capacitance measurement. Dispersion condition of nano-SiC powders in epoxy matrix was evaluated with two different dispersion methods, i.e., sonication and stirring methods. The dispersion degree was also verified with the tensile strength correlating to capacitance.

• Advances in nano research
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• v.15 no.3
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• pp.253-261
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• 2023

This study investigates the application of nano-composite materials in physical education, specifically focusing on improving the performance of sports hall flooring. The research centers on carbon nanotube reinforced polyvinyl chloride (PVC) composites, which offer enhanced mechanical properties and durability. The incorporation of carbon nanotubes as reinforcements in the PVC matrix provides notable benefits, including increased strength, improved thermal stability, electrical conductivity, and resistance to fatigue. The key parameters examined in this study are the weight percentage of carbon nanotubes and the temperature during the fabrication process. Through careful analysis, it is found that higher weight percentages of carbon nanotubes contribute to a more uniform dispersion within the PVC matrix, resulting in improved mechanical properties. Additionally, higher fabrication temperatures aid in repairing macroscopic defects, leading to enhanced overall performance. The findings of this study indicate that the utilization of carbon nanotube reinforced PVC composites can significantly enhance the strength and durability of sports hall flooring. By employing these advanced materials, the safety and suitability of physical education environments can be greatly improved. Furthermore, the insights gained from this research can contribute to the optimization of composite material design and fabrication techniques, not only in the field of physical education but also in various industries where composite materials find applications.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.454-460
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• 2015

The present study is undertaken to evaluate the effect of volume fraction on the results of Charpy impact test for the rubber matrix filled with nano sized silica particles composites. The Charpy impact tests are conducted in the temperature range $0^{\circ}C$ and $-10^{\circ}C$. The range of volume fraction of silica particles tested are between 11% to 25%. The critical energy release rate $G_{IC}$ of the rubber matrix composites filled with nano sized silica particles is affected by silica volume fraction and it is shown that the value of $G_{IC}$ decreases as volume fraction increases. In regions close to the initial crack tip, fracture processes such as matrix deformation, silica particle debonding and delamination, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact fracture surfaces.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.561-566
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• 2015

In this study, the effect of temperature effect of the rubber matrix filled with nano sized silica particles composites with silica volume fraction of 19-25% was investigated by the Charpy impact test. The Charpy impact test was conducted in the temperature range from $-40^{\circ}C$ to $0^{\circ}C$. The critical energy release rate GIC of the rubber matrix composites filled with nano sized silica particles was considerably affected by temperature and it was shown that the maximum value was appeared at higher temperature between temperature tested and it was shown that the value of GIC increases as temperature tested increases. The major fracture mechanisms were matrix deformation, silica particle debonding and delamination, microcrack between particles and matrix, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact surfaces fracture.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.155-155
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• 2009

This paper introduces the findings of a detailed study on breakdown voltage strength under DC voltage and the development of HVDC cable. Recently, Nano-fillers are attracting attentions of many researchers and engineers, since they seem to bring higher potentials for advancement of electrical insulating properties as nano-composites. Additives and fillers are often adopted to polymeric materials for improving insulating and machanical properties. We have improved the polymer composition and developed a new insulation material for HVDC cable. Each specimen blended at LDPE1 to antioxidant, LDPE2 to antioxidant, pure XLPE was manufactured respectively. The insulation performances of the proposed insulator were compared with specimens blended at nano powders. DC breakdown strength of LDPE1 specimen at 90[$^{\circ}C$] was higher than other specimens. The experimental results show that polar groups intorduced in moleculars chains of blended specimen plays an important role in enhancement of thermal conductivity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1136-1139
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• 2005

As alternative materials for bipolar plate of PEM Fuel Cells, carbon composites were fabricated by compression molding. In this study, four types of nano particles, such as Carbon nanotubes, Carbon black, GX-15 and P-15 were mixed with epoxy resin to provide electric conductivity and structural properties. By increasing pressure during molding and volume ratio of nano particles, the physical contact among particles was improved resulting in increased electric conductivity. Surface resistance test showed, P-15 particles have the highest electric conductivity.

• Carbon letters
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• v.10 no.4
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• pp.320-324
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• 2009

We investigated the effect of diameter and content of carbon nanotubes (CNTs) on the physical properties of styrenebutadiene rubber (SBR)/CNTs nanocomposites. CNTs-reinforced SBR nanocomposites were prepared by the melt mixing process. CNTs with different diameters were synthesized by the chemical vapor deposition method (CVD). In this work, the mechanical property and other physical properties of SBR/CNTS nanocomposites were discussed as a function of the content and diameter of CNTs.