• Journal of Powder Materials
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• v.29 no.6
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• pp.477-484
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• 2022

Thermal protection systems (TPS) are a group of materials that are indispensable for protecting spacecraft from the aerodynamic heating occurring during entry into an atmosphere. Among candidate materials for TPS, ceramic insulation materials are usually considered for reusable TPS. In this study, ceramic insulation materials, such as alumina enhanced thermal barrier (AETB), are fabricated via typical ceramic processing from ceramic fiber and additives. Mixtures of silica and alumina fibers are used as raw materials, with the addition of B4C to bind fibers together. Reaction-cured glass is also added on top of AETB to induce water-proof functionality or high emissivity. Some issues, such as the elimination of clumps in the AETB, and processing difficulties in the production of reusable surface insulation are reported as well.

• Composites Research
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• v.30 no.1
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• pp.1-6
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• 2017

Epoxy resin (EP) is one of the most famous thermoset materials. In general, because EP has three-dimensional random network, it possesses thermal properties like a typical heat insulator. Recently, there has been increasing interest in controlling the network structure for making new functionality from EP. Indeed, the new modified EP represented as liquid crystalline epoxy (LCE) is spotlighted as an enabling technology for producing novel functionalities, which cannot be obtained from the conventional EPs, by replacing the random network structure to oriented one. In this paper, we review current progress in the field of LCEs and their application for the highly thermal conductive composite materials.

• Polymer(Korea)
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• v.35 no.6
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• pp.548-552
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• 2011

Two functionalization methods, i.e., acid treatment and chemical amidation were performed to prepare the functionalized multi-walled carbon nanotubes (MWCNT), and the properties of epoxy/functionalized MWCNT composites were investigated and compared. Fourier transform infrared spectroscopy (FTIR) was used to confirm the surface functionality of the MWCNT obtained by the functionalization methods. The effects of the MWCNT functionalization on the interface and thermal conductivity were studied by zeta potential analyzer, scanning electron microscope and thermal conductivity analyzer. From these results, it was confirmed that the thermal conductivity of the epoxy/MWCNT composites could be increased by grafting with dodecylamine. This could be interpreted by relatively strong dispersion forces of the grafting MWCNT with dodecylamine in DGEBF epoxy resin. These results were in good agreement with the results that the zeta potential value of the grafting MWCNT with dodecylamine has a higher negative value than that of MWCNT with acid treatment.

• Journal of the Korea Fashion and Costume Design Association
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• v.20 no.4
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• pp.163-174
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• 2018

Consumer and property evaluation of wetsuit materials were conducted to obtain useful data for developing competitive products that meet consumer expectations and improving industrial competitiveness. Data were collected through online surveys of 213 domestic consumers who have experienced wearing wetsuit among marine leisure activities. Five types of commercial wet suit materials by brand and four types of commercial wet suit materials with the same quality by thickness were collected. Then, their physical properties, salt water resistance and thermal insulation rate were evaluated and compared. As a result, the most commonly used wetsuit material is 3 to 5 mm thick, and the basic jersey material is bonded on both sides. As a processing for imparting functionality, processing for improving warmth and reducing surface resistance are most frequently used. Consumers often feel uncomfortable when wearing a wetsuit, such as wearing comfort, weight, ease of movement, stretchability, and clothing pressure, which are different from those of casual wear. Also, mechanical strength and warmth were considered to be the most important criteria for selection of wetsuit material for purchase or rental. The mechanical properties of brand A and B were better than those of brand C, D, and E. Resilience and thermal shrinkage were better in brand C, D, and E. On the other hand, there was no significant difference in the physical properties due to the difference in thickness of the material at the same quality. Also, it was found that the thicker the material, the more stable it is in the heat. Brand A and B had superior salt water resistance than brand C, D, and E. In the thermal insulation test, brand A and B showed better insulation characteristics than brand C, D, and E, but the types of bonded fabric and surface finishing of materials were thought to have affected. In comparison of the thickness, the thicker the materials, the better the salt resistance and the thermal insulation.

• Journal of Powder Materials
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• v.23 no.6
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• pp.414-419
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• 2016

Much attention has been paid to thermally conductive materials for efficient heat dissipation of electronic devices to maintain their functionality and to support lifetime span. Hexagonal boron nitride (h-BN), which has a high thermal conductivity, is one of the most suitable materials for thermally conductive composites. In this study, we synthesize h-BN nanocrystals by pyrolysis of cost-effective precursors, boric acid, and melamine. Through pyrolysis at $900^{\circ}C$ and subsequent annealing at $1500^{\circ}C$, h-BN nanoparticles with diameters of ~80 nm are synthesized. We demonstrate that the addition of small amounts of Eu-containing salts during the preparation of melamine borate precursors significantly enhanced the crystallinity of h-BN. In particular, addition of Eu assists the growth of h-BN nanoplatelets with diameters up to ~200 nm. Polymer composites containing both spherical $Al_2O_3$ (70 vol%) and Eu-doped h-BN nanoparticles (4 vol%) show an enhanced thermal conductivity (${\lambda}{\sim}1.72W/mK$), which is larger than the thermal conductivity of polymer composites containing spherical $Al_2O_3$ (70 vol%) as the sole fillers (${\lambda}{\sim}1.48W/mK$).

• Journal of Environmental Health Sciences
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• v.30 no.4
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• pp.314-319
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• 2004

Glycinin of more than $97\%$ purity was modified using maleic anhydride. Glycinin samples of $0\%,\;65\%,\;and\;95\%$ lysine residue modifications were used to determine the changes in turbidimetric characteristics of the protein due to maleylation. The solubility behavior of the protein as a function of pH was changed with maleylation. The isoelectric point of $65\%\;and\;95\%$ modified glycinin shifted to pH 4.0 and pH 3.5-4.0, respectively, as compared to pH 4.6 for native glycinin. Maleylated glycinins exhibited increased solubility at pH above 4.6. Turbidity of native glycinin decreased substantially by the addition of NaCl, but the stabilizing effect of NaCl decreased when the protein was chemically modified. The effect of NaCl on $65\%$ modified glycinin was intermediate between native glycinin and $95\%$ modified sample. Thermal aggregation of native glycinin was completed within 5 min of heating at $80^{\circ}C$. Maleylation contributed significantly to the thermostability of the protein at pH of 7.0 and 9.0, exhibiting little turbidity. Addition of NaCl suppressed thermal aggregation of native glycinin, but turbidity actually increased for the samples of $65\%\;and\;95\%$ modification.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.595-599
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• 2011

ALC(Autoclaved Lightweight Concrete) is produced using quartz sand, lime and cement and water. And aluminum powder is used for blowing agent. ALC is manufactured by autoclave chamber under high-temperature and high-pressure. Generally, ALC is 1/4 levels lighter than concrete and mortar, because it has a lot of pores. So density of ALC is about 0.45~0.65 g/$cm^3$. But, ALC has a weakness, typically low strength, with its porous structure. So, it is necessary to excellent strength properties for extensive apply of ALC materials in high porosity. In this study, melamine resin was used to improve the strength characteristics of ALC materials. We performed compressive and bending strength measurements. Compressive strength of ALC with 2% melamine resin increased 26.88% than 'melamine-free' ALC. Also we performed functionality evaluation such as thermal conductivity, sound absorption, and flame-resistance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.428-436
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• 2006

The assessment of an urban site depends on the way whether it responds to multiple needs such as functionality, aesthetic and complex comfort of acoustic, thermal, lighting and air quality etc. This study aims to investigate the assessment of various urban soundscapes in the sense of acoustic amenity by the questionnaires. As a result, acoustic amenity assessment was influenced by the non-acoustic factors such as environment assessment of visual, thermal, air quality etc. In the sense of sound quality, urban environmental sound was interpreted as 3 factors of strength, evolution of time, spacial localization. So these factors would be considered in the new assessment method for acoustic amenity. And it was shown that the subjects tend to perceive the noise level less than $3{\sim}5dB\;L_{eqA}$ according to the urban landscapes under the similar noise exposure level.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.363-366
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• 2005

A micro flow sensor on silicon substrate allows the fabrication of small components where many different functions can be integrated so that the functionality of the sensors can be increased. Further more, due to the small size of the elements the sensors can be quite fast. A thermal mass flow sensor measures the asymmetry of temperature profile around the heater which is modulated by the fluid flow. In normal, a mass flow sensor is composed of a central heater and a pair of temperature sensing elements around the heater. A new 2-D wide range micro flow sensor structure with three pairs of temperature sensors and a central heater was proposed and numerically simulated by the Finite difference formulation to confirm the feasibility of the flow sensor structure.

• Journal of the Korean institute of surface engineering
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• v.56 no.1
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• pp.55-61
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• 2023

As a preliminary study to produce functional nanocomposites in a heat dissipation device, we performed the direct synthesis of carbon nanotubes (CNTs) on the surface of alumina (Al₂O₃) powders. A thermal chemical vapor deposition (TCVD) system was used to grow CNTs directly on the Al₂O₃ surface. In order to investigate the growth behavior of CNTs, we varied both furnace temperature of the TCVD ranging from 700 to 850 ℃ and concentration of the ferritin-dissolved DI solution from 0.1 to 2.0 mg/mL. From the previous results, the gas composition and duration time for CNT growth were fixed as C₂H₄ : H₂ = 30 : 500 (vol. %) and 10 min, respectively. Based on the analysis results, the optimized growth temperature and ferritin concentration were found to be 825 ℃ and 0.5 mg/mL, respectively. The obtained results could be adopted to achieve mass production of nanocomposites with heat dissipation functionality.