• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.48 no.4
• /
• pp.357-364
• /
• 2022

In this study, antioxidant efficacy was analyzed to verify the value of use as an antioxidant-related functional cosmetic material using Cheongtaejeon tea extract. Cheongtaejeon tea was extracted, concentrated, and freeze-dried with hot water and 70% ethanol as a solvent to prepare samples, and then ABTS⁺ radical scavenging activity, electron donating ability, SOD-like ability, reducing power, ferric reducing antioxidant power (FRAP), total phenolic, and flavonoid contents were analyzed. In the ABTS⁺ radical scavenging activity experiment, both the Cheongtaejeon hydrothermal extract (CTW) and the Cheongtaejeon 70% ethanol extract (CTE) showed erasure activity of more than 98% at a concentration of 1,000 ㎍/mL, and in the electron donating analysis experiment, CTW and CTE, respectively, 42.20% and 78.82%. As a result of SOD-like activity measurement, activity of 39.73% and 67.39% of CTW and CTE, respectively, was confirmed. In the case of FRAP and reducing power experiments, both CTW and CTE showed high effects, and as a result of analyzing the total phenol and flavonoid contents, both CTW and CTE showed high contents. Based on the results of the experiment, the Cheongtaejeon tea extract is expected to have a highly valuable as a functional cosmetics material related to antioxidants.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.9
• /
• pp.916-922
• /
• 2008

Structures being used in space environment, should be designed to have minimum CTE(coefficient of thermal expansion) for the dimensional stability. Accurate CTE data of the materials are required to design the space structures consisting of various materials. There are uncertainties in the characteristics of materials even though the same manufacturing processes are applied. Therefore, it is needed to measure the thermal deformation of not only the material specimen but also substructures in simulated space environment, such as high vacuum condition. In this research, therefore, precise CTE measurement system using displacement measuring interferometer and vacuum chamber has been designed with uncertainty analysis of the measurements. This system can be used to measure the CTE of the specimen or thermal expansion of the substructure with varying size up to 50cm in length. To measure the low CTE material, overall uncertainty of this system is expected under 0.01ppm/K.

• Journal of Welding and Joining
• /
• v.32 no.3
• /
• pp.68-73
• /
• 2014

Among through silicon via (TSV) technologies, for replacing Cu filling method, the method of molten solder filling has been proposed to reduce filling cost and filling time. However, because Sn alloy which has a high coefficient of thermal expansion (CTE) than Cu, CTE mismatch between Si and molten solder induced higher thermal stress than Cu filling method. This thermal stress can deteriorate reliability of TSV by forming defects like void, crack and so on. Therefore, we fabricated SiC composite filling material which had a low CTE for reducing thermal stress in TSV. To add SiC nano particles to molten solder, ball-typed SiC clusters, which were formed with Sn powders and SiC nano particles by ball mill process, put into molten Sn and then, nano particle-dispersed SiC composite filling material was produced. In the case of 1 wt.% of SiC particle, the CTE showed a lowest value which was a $14.8ppm/^{\circ}C$ and this value was lower than CTE of Cu. Up to 1 wt.% of SiC particle, Young's modulus increased as wt.% of SiC particle increased. And also, we observed cross-sectioned TSV which was filled with 1 wt.% of SiC particle and we confirmed a possibility of SiC composite material as a TSV filling material.

• Polymer(Korea)
• /
• v.37 no.6
• /
• pp.711-716
• /
• 2013

The effect of chain orientation and relaxation on the characteristics of poly(ethylene naphthalate) (PEN) flexible substrate has been studied. It was found that the coefficient of thermal expansion (CTE) of PEN under $100^{\circ}C$ decreased as low as $20ppm/^{\circ}C$ due to the lowering of chain mobility by chain orientation. The thermal shrinkage was found to appear near glass transition temperature because of chain relaxation. It could be minimized by thermal annealing but CTE increased again up to $70ppm/^{\circ}C$ which was 65% of intrinsic CTE of PEN. Unstrained thermal annealing made possible to avoid the thermal shrinkage with maintaining low CTE obtained by chain orientation. Chain orientation did not affect the optical transmittance; however, thermal annealing caused the decrease of optical transmittance up to 5%. This was understood by the minor crystallization due to the thermal annealing near glass transition temperature.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.04a
• /
• pp.190-194
• /
• 2000

The fabrication process and thermal properties of 50∼76vo1% SiCp/Al metal matrix composites (MMCs) were investigated. The 50∼76vo1% SiCp/Al MMCs fabricated by pressure infiltration casting process showed that thermal conductivities were 85∼170W/mK and coefficient of thermal expansion (CTE) were ranged 10∼6ppm/K. Specially, the thermal conductivity and CTE of 71vo1%SiCp/Al MMCs were ranged l15∼156W/mK and 6∼7ppm/K, respectively, which showed a improved thermal properties than the conventional electronic packaging materials such as ceramics and metals.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1346-1348
• /
• 2001

Generally, Invar alloy shows very low thermal expansion characteristics, lower than $2{\times}10^{-6}$/K approximately. To apply Fe-Ni-Co-C Invar alloy as a core material for large ampacity transmission line we studied the effects of magnetic properties on coefficient of thermal expansion. The coefficient of thermal expansion(CTE) suddenly decreases with addition of a little carbon(0.08%), increases with the increasing carbon and has a constant value at the composition over than 1.0%C. The trend of Curie temperature change with carbon is similar with that of CTE. Therefore, the CTE has a linear relationship with Curie temperature. However, the CTE linearly decreases with the ratio of saturation magnetization and Curie temperature(${\sigma}_s/T_c$).

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 1999.11a
• /
• pp.83-87
• /
• 1999

The fabrication process and thermal properties of 50~71vol% SiCp/Al metal matrix composites (MMCs) were investigated. The 50~71vol% SiCp/Al MMCs fabricated by pressure infiltration casting process showed that thermal conductivities were 118~170W/mK and coefficient of thermal expansion (CTE) were 9.5~$6.5{\times}10^{-6}/K$. Specially, the thermal conductivity and CTE of 71vol%SiCp/Al MMCs were 115~156W/mK and 6~$7{\times}10^{-6}/K$. respectively, which showed a improved themal properties than the conventional electronic packaging materials such as ceramics and metals.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.192-197
• /
• 2004

The anisotropy in coefficient of thermal expansion (CTE) between the in-plane and out-of-plane of 3-dimensional thick composite structures induces residual stresses and the large void content due to insufficient compaction of fabric composites, which results in low interlaminar strengths. In order to reduce the through thickness CTE and the void content, in this work, carbon fabric phenolic laminates were compacted by pressure generated by autoclave and a compressive jig, from which the through-thickness CTEs and the void contents were measured. From the measurement, it was found that the through-thickness CTE and the void content had different characteristics from ordinary composites due to gas produced during the cure reaction of phenolic resin.

• Polymer(Korea)
• /
• v.33 no.6
• /
• pp.530-536
• /
• 2009

A cycloaliphatic epoxy/acidic anhydride system incorporating short carbon fibers (SCF) and short glass fibers (SGF) was fabricated and thermal/mechanical properties were characterized. At low filler content both SCF- and SGF-reinforced composites showed a similar decrease in coefficient of thermal expansion (CTE), measured by a thermomechanical analyzer, with increasing loadings, above which SCF became more effective than SGF at reducing the CTE. Experimental CTE data for the SCF-reinforced composites is best described by the rule of mixtures at lower SCF contents and by the Craft-Christensen model at higher SCF contents. Storage modulus (E') at $30^{\circ}C$ and $180^{\circ}C$ was greatly enhanced for short fiber-filled composites compared to unfilled specimens, Scanning electron microscopy of the fracture surfaces indicated that the decreased CTE and the increased E' of the short fiber-reinforced composites resulted from good interfacial adhesion between the fibers and epoxy matrix.

• Progress in Superconductivity and Cryogenics
• /
• v.14 no.4
• /
• pp.24-27
• /
• 2012

The measurement of the coefficient of thermal expansion (CTE) of polypropylene laminated paper (PPLP) as electric insulating material is important for its practical superconducting device application. The thermal strain induced to HTS tapes and its insulating material during cooling from room temperature might largely affect the critical current ($I_c$) of HTS tapes. In this study, the thermal contraction of PPLP material was measured during cooling from 300 K to 77 K using double extensometers. Initially, the CTE of a brass tape was measured and it was compared with a reference data. It was found that the measured thermal expansion data of the brass material approaches that of the reference one. Based on the results, it was then confirmed that the measurement technique could be applied to thin and flexible samples. Therefore, the same measurement procedure was applied to PPLP material using double extensometers. As a result, the linear CTE of the PPLP at 77 K has been measured to be ${\sim}15.3{\times}10^{-6}/K$. Also, it was found that the thermal contraction characteristics of PPLP was dominated by polypropylene on the cross direction (higher thermal contraction) while it was dominated by Kraft paper on the machine direction (lower thermal contraction). Overall, this measurement procedure could be adopted for the determination of CTE of flexible materials such as PPLP.