• Textile Coloration and Finishing
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• v.32 no.2
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• pp.103-110
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• 2020

Super engineering plastic(SEP) are applied to high performance and high value industries due to their excellent mechanical properties and high continuous operating temperature. Among them, PES and PEI are amorphous SEPs, and have the advantages of high flexibility, mechanical properties, transparency, and thermal stability. In this study, polyethersulfone(PES) and polyetherimide(PEI) fibers were manufactured to produce flame retardant artificial hair. PES and PEI fibers prepared through a melt-spinning process at a high temperature of 360 to 420℃. They are compared with commercial artificial hair by thermal gravimetric analysis(TGA), linear density, tenacity, and limited oxygen index(LOI) analysis. PES and PEI fibers have similar linear density and tenacity to commercial artificial hair, while their thermal stability and flame retardant are excellent. In particular, flame retardant was analyzed through LOI value and PES was 35.1%, which is superior to commercial artificial hair PET/Br(28.2%) and PET/P(20.2%). Therefore, PES and PEI are suitable as artificial hair for flame retardant.

• Transactions on Electrical and Electronic Materials
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• v.8 no.3
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• pp.110-114
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• 2007

Dependence of the thermal stability of nickel silicide on the film stress of inter layer dielectric (ILD) layer has been investigated in this study and silicon nitride $(Si_3N_4)$ layer is used as an ILD layer. Nickel silicide was formed with a one-step rapid thermal process at $500^{\circ}C$ for 30 sec. $2000{\AA}$ thick $Si_3N_4$ layer was deposited using plasma enhanced chemical vapor deposition after the formation of Ni silicide and its stress was split from compressive stress to tensile stress by controlling the power of power sources. Stress level of each stress type was also split for thorough analysis. It is found that the thermal stability of nickel silicide strongly depends on the stress type as well as the stress level induced by the $Si_3N_4$ layer. In the case of high compressive stress, silicide agglomeration and its phase transformation from the low-resistivity nickel mono-silicide to the high-resistivity nickel di-silicide are retarded, and hence the thermal stability is obviously improved a lot. However, in the case of high tensile stress, the thermal stability shows the worst case among the stressed cases.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.129-136
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• 2005

The demand on thermos furnace of Al molten metal has recently been getting higher and higher according to the increase in use of Al and Al alloys. This study considers the estimation of the thermal and mechanical stability in the thermos furnace for Al casting. It is executed through the analysis of heat transfer on the refractory material and heat stress on each steel shell. Also, the estimation of structural stability was appraised through the strength analysis of the lower structure. In result, the temperature of steel shell rose to 320.15K and its elastic deformation was about 1.5mm. The elastic deformation of the lower structure was about 0.66mm. As a result of it, the data obtain from the analysis in this study are regarded as stable value on considering that the size of the furnace is 2500mm.

• Progress in Superconductivity and Cryogenics
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• v.18 no.1
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• pp.59-63
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• 2016

The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling method using cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than the cryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a 400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS double pancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks and finally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermal and structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load are considered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermal design of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermal contraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each component of the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.

• Advances in nano research
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• v.6 no.4
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• pp.377-397
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• 2018

In the present investigation, thermal buckling and free vibration characteristics of functionally graded (FG) Timoshenko nanobeams subjected to nonlinear thermal loading are carried out by presenting a Navier type solution. The thermal load is assumed to be nonlinear distribution through the thickness of FG nanobeam. Thermo-mechanical properties of FG nanobeam are supposed to vary smoothly and continuously throughout the thickness based on power-law model and the material properties are assumed to be temperature-dependent. Eringen's nonlocal elasticity theory is exploited to describe the size dependency of nanobeam. Using Hamilton's principle, the nonlocal equations of motion together with corresponding boundary conditions based on Timoshenko beam theory are obtained for the thermal buckling and vibration analysis of graded nanobeams including size effect. Moreover, in following a parametric study is accompanied to examine the effects of the several parameters such as nonlocal parameter, thermal effect, power law index and aspect ratio on the critical buckling temperatures and natural frequencies of the size-dependent FG nanobeams in detail. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FG nanobeams as compared some cases in the literature. Also, it is found that the small scale effects and nonlinear thermal loading have a significant effect on thermal stability and vibration characteristics of FG nanobeams.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1294-1295
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• 2006

Various reactions and the in-situ formation of new phases can occur during the mechanical alloying process. In the present study, Al powders were strengthened by AlN, using the in-situ processing technique during mechanical alloying. Differential thermal analysis and X-ray diffraction studies were carried out in order to examine the formation behavior of AlN. It was found that the precursors of AlN were formed in the Al powders and transformed to AlN at temperatures above $600^{\circ}C$. The hot extrusion process was utilized to consolidate the composite powders. The microstructure of the extrusions was examined by SEM and TEM. In order to investigate the mechanical properties of the extrusions, compression tests and hardness measurements were carried out. It was found that the mechanical properties and the thermal stability of the Al/AlN composites were significantly greater than those of conventional Al matrix composites.

• Journal of the Korean Wood Science and Technology
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• v.43 no.6
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• pp.740-745
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• 2015

Hydroxypropyl cellulose (HPC) composite films filled with TEMPO-oxidized cellulose nanofibrils (TOCN) were prepared in this study. In order to investigate mechanical and thermal properties of HPC/TOCN composite films, tensile strength and thermogravimetric analysis (TGA) wer performed. As the loading level of TOCN increased, the tensile strength and modulus increased significantly. However, thermal stability of HPC/TOCN composite films was not related to the loading levels of the TOCN.

• Journal of the Korean Applied Science and Technology
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• v.24 no.4
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• pp.416-426
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• 2007

Polypropylene (PP) composites with wood flour/wax/coupling agent were manufactured by melt compounding and injection molding. The influence of wood flour(WF), wax, and coupling agent on the mechanical and thermal properties of the composites was investigated. The addition of wood flour to neat PP has the higher tensile modulus and strength compared with neat PP. The presence of wax also improved the tensile modulus. At the same loading of PP and WF, the addition of coupling agent highly decreased the tensile modulus, and increased the tensile strength. From thermogravimetric analysis (TGA), the addition of wax improved the thermal stability of the composites in the later stages of degradation. The presence of MAPP and wood flour in turn decreased thermal stabilities of composites. From differential scanning calorimetry analysis (DSC), neither the loading of wax. nor the presence of MAPP has shown significant effect on the thermal transition of composites.

• Composites Research
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• v.28 no.5
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• pp.316-321
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• 2015

This study investigated the effects of microcapsules on mechanical properties and thermal stability of the composite material containing self-healing microcapsules. To this end, tensile specimens and flexural specimens containing melamine-urea-formaldehyde (M-U-F) shell walled microcapsules with diameters of $70{\sim}130{\mu}m$ were manufactured. Varying amount of microcapsules in the specimens was considered: 0 wt%, 0.5 wt%, and 1.0 wt%. The tensile and flexural tests were conducted to evaluate mechanical properties of the specimens containing the microcapsules and the thermogravimetric analysis test was performed to evaluate the thermal stability of the specimens containing the microcapsules. The results show that the tensile strength of the specimens was sensitive to the amount of the microcapsules compared to the tensile modulus even though the tensile modulus of the specimens was not significantly affected by the amount of the microcapsules. However, reduction of the tensile strength was not linearly proportional to the amount of microcapsules; similar results were observed in the flexural test. The weight changes of the specimens containing the microcapsules, as a function of temperature, were similar to those specimens without microcapsules. The thermal stability of the specimens was not affected significantly by the microcapsules embedded in the specimens.

• Structural Engineering and Mechanics
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• v.75 no.6
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• pp.659-674
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• 2020

The present paper employs nonlocal strain gradient theory (NSGT) to study buckling behavior of functionally graded magneto-electro-thermo-elastic (FG-METE) nanoshells under various physical fields. NSGT modeling of the nanoshell contains two size parameters, one related to nonlocal stress field and another related to strain gradients. It is considered that mechanical, thermal, electrical and magnetic loads are exerted to the nanoshell. Temperature field has uniform and linear variation in nanoshell thickness. According to a power-law function, piezo-magnetic, thermal and mechanical properties of the nanoshell are considered to be graded in thickness direction. Five coupled governing equations have been obtained by using Hamilton's principle and then solved implementing Galerkin's method. Influences of temperature field, electric voltage, magnetic potential, nonlocality, strain gradient parameter and FG material exponent on buckling loads of the FG-METE nanoshell have been studied in detail.