• 한국주조공학회지
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• 제43권5호
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• pp.223-229
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• 2023

In this study, STS316L produced by a double-melting process involving vacuum induction melting (VIM) and vacuum arc remelting (VAR) was subjected to extrusion and drawing to form a tube and was subsequently electrolytic polished (EP). The grain size of the obtained STS316L without EP was approximately 55 ㎛, with no difference found after EP. The thickness of the EP layer was measured by AES and TEM, showing values of approximately 10 nm and 15 nm, respectively. After EP, the Cr/Fe and CrO/FeO ratios of the passive layer increased from 1.48 to 1.62 and from 2.15 to 2.26, respectively, while the surface roughness decreased significantly from 0.255 to 0.024 ㎛. Consequently, the corrosion rate decreased in both NaCl and HCl solutions after the EP process. Additionally, the amounts of eluted Cr and Fe ions were reduced from 1.2 to 0.8 ppb and 10.3 to 0.8 ppb, respectively. Furthermore, polarization tests revealed that STS316L treated with EP required a lower current density to reach a passive state, indicating that corrosion behavior was retarded.

• Macromolecular Research
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• 제13권2호
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• pp.156-161
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• 2005

The thermal transitions of a nylon 6/layered silicate nanocomposite were studied by differential scanning calorimetry and in-situ synchrotron X-ray diffraction. The drawn film of the nylon 6/layered silicate nanocomposite typically showed three endotherms in the DSC thermogram; a very broad endotherm at $\sim120^{\circ}C(T_{1})$, a double-melting endotherm at $\sim215^{\circ}C(T_{2})$, and a high temperature endotherm at $\sim240^{\circ}C(T_{3})$. The drawn film of the nylon 6/ layered silicate nanocomposite was comprised of a mixture of the $\alpha and \gamma$ forms, with $the \alpha form$ being generated by drawing the pressed film having $the \gamma form$. The melting and crystallization of the crystals were observed at the above thermal transitions during the heating experiment performed at the Pohang X-ray synchrotron radiation source (4C2). The newly generated form was meta-stable and melted $at {\sim}T_{1}$. The double-melting $at {\sim}T_{2}$ was due to the exothermic crystallization of $the \alpha form$ during the main endothermic melting of $the \gamma form$. $The \alpha form$ crystallized $at {\sim}T_{2}$ and melted $at {\sim}T_{3}$.

• 한국의류산업학회지
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• 제11권3호
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• pp.474-480
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• 2009

The purpose of this study is to prepare the hardness of polyester(PET) fabric by thermal bonding with low melting component of bicomponent fiber and to describe the change of physical properties of thermal bonded PET fabrics. The PET fabrics were prepared with regular PET fiber as warp and bicomponent fiber as weft. The bicomponent fiber of sheath-core type were composed with a regular PET core and low melting PET sheath. The thermal bonding of PET fabric was carried out in pin tenter from 120 to $195^{\circ}C$ temperature range for 60 seconds. In this study, we investigated the physical properties and melting behavior of PET fiber and the effect of the temperature of the pin tenter on the thermal bonding, mechanical properties. Melting peak of warp showed the thermal behavior of general PET fiber. However, melting peak of weft fiber(bicomponent fiber) showed the double melting peak. The thermal bonding of the PET fabric formed at about temperature of lower melting peak. The optimum thermal bonding conditions for PET fabrics was applied at $190{\sim}195^{\circ}C$ for 60seconds by pin tenter. On the other hand, the tensile strength of the PET fabric decreased with an increasing temperature of thermal bonding.

• 한국의류학회지
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• 제13권1호
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• pp.43-47
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• 1989

The microstructural changes of nylon 6 UDY, POY and FDY were compared after free-annealing through crystallinity, birefringence, and melting behavior analyses. Free-annealing was done at various temperatures $(120^{\circ}C\;,140^{\circ}C,\;160^{\circ}C,\;180^{\circ}C,\;200^{\circ}C)$ and times (15 min., 30 min., 60 min.) using vaccum oven. Crystallinity was measured by the density gradient column technique and birefringence was measured using a Nikon polarizing microscope with a quartz wedge and Senarmont compensator. Melting behavior was investigated on the basis of DSC melting corves. Crystallinites of specimens increased as the treatment temperature and time increased. Birefringence of UDY increased after annealing and increased as the treatment temperature increased. On the other hand, those of POY and FDY decreased after annealing. Especially, the changes of crystallinity and birefringence of treated POY were particularly lower than those of treated UDY and FDY. Melting peaks of untreated UDY, POY and FDY were different in the position and the shape, but little change was seen in melting peaks in spite of increasing the annealing temperature and time. UDY and FDY showed single melting peaks in all the specimens. But POY showed double melting peaks, which means the coexistences of crystals with different thermal properties.

• 한국염색가공학회지
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• 제25권2호
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• pp.110-117
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• 2013

The purpose of this study is to fabricate the flame retardant polyester fabric by thermal bonding with low melting component of flame retardant bicomponent filament(LMFRPC) and to describe the characteristics of thermal bonded fabrics. The fabrics were prepared with flame retardant polyester filaments(FRP) as warp and blended filaments of FRP and LMFRPC as weft. The LMFRPC have a sheath and a core wherein the core comprises a flame retardant polyester and the sheath comprises a thermoplastic polyester of low-melting point. In this study, we investigated the physical properties, melting behavior of filament, the effect of the component of FRP and LMFRPC on the thermal bonding, mechanical properties. Melting peak of LMFRPC showed the double melting peak. The thermal bonding of the fabric formed at lower melting peak temperature of bicomponent filament of LMFRPC. The optimum thermal bonding conditions for fabrics was applied at about $170^{\circ}C$ for 60 seconds by pin tenter. On the other hand, the tensile strength, elongation, and LOI of the fabric increased with an increasing component of FRP of weft.

• 한국산학기술학회논문지
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• 제14권3호
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• pp.1519-1526
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• 2013

본 연구에서는 현장조사를 통해 주물 제조 사업장의 일부 용해공정에 적용되고 있는 캐노피 후드(canopy hood)의 흡인 성능을 검토하였다. 또한, CFD model을 이용하여 유해대기오염물질 포집 능력을 향상시킬 수 있는 방안들을 대한 유동장 및 압력장을 비교 및 평가하였다. Case-2(플랜지 부착+이중 후드)의 경우 포집 성능 측면에서는 개선이 가능하지만 후드 정압이 기존 구조보다 약 70% 이상 증가할 것으로 예측되어 현장 적용성이 좋지 않을 것으로 나타났다. 흡인효율을 개선하기 위해서는 case-3(플랜지 부착+이중 콘 부착)의 형상이 가장 적합할 것으로 판단된다. 이는 개구부 중앙에 이중 콘(cone)이 설치되어 후드 가장자리로 유량을 집중시킬 수 있으며, 또한 후드 중앙으로 상승되는 흄(hume)은 콘의 기울기에 의해 정압 상승의 요인 없이 제어할 수 있기 때문이다.

• 한국의류학회지
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• 제11권3호
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• pp.33-40
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• 1987

PET FDY was heat set at various temperatures and times and the microstructural changes was investigated through crystallinity, birefringence and melting behavior analyses. Crystallinity of heat set PET increased as the treatment temperature and time increased. Birefringence also increased as temperature and time increased. The melting behavior of heat set PET was as follows: In most cases, PET showed double melting peaks. As temperature and time increased, form II crystal became sharp and increased in size, and form I crystal decreased in size. The slower the heating rate, the higher the programmed heating effect during DSC analysis.

• 한국산학기술학회논문지
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• 제3권2호
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• pp.89-93
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• 2002

PbO 함유 다성분계유리 및 파이버를 제조하였으며, PbO함유 유리는 이중도가니법(double crucible methodo에 의한 높은 개구수를 갖는(high-numerical aperture : N.A.) 광파이버(optical fiber) 제조에 적합하였다. 본 실험에 있어서는 SiO₂, PbO를 주성분으로 하고 K₂O, Na₂O, B₂O₃, A1₂O₃등의 산화물을 적량 배합하였으며, 또한 double crucible method에 의해 제조된 파이버의 광학적, 기계적 및 구조적 특성을 관찰하였다.

• Macromolecular Research
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• 제14권2호
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• pp.146-154
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• 2006

Organic and inorganic hybrid nanocomposites based on poly(ethylene 2,6-naphthalate) (PEN) and silica nanoparticles were prepared by a melt blending process. In particular, polymer nanocomposites consisting mostly of cheap conventional polyesters with very small quantities of inorganic nanoparticles are of great interest from an industrial perspective. The crystallization behavior of PEN/silica hybrid nanocomposites depended significantly on silica content and crystallization temperature. The activation energy of crystallization for PEN/silica hybrid nanocomposites was decreased by incorporating a small quantity of silica nanoparticles. Double melting behavior was observed in PEN/silica hybrid nanocomposites, and the equilibrium melting temperature decreased with increasing silica content. The fold surface free energy of PEN/silica hybrid nanocomposites decreased with increasing silica content. The work of chain folding (q) for PEN was estimated as $7.28{\times}10^{-20}J$ per molecular chain fold, while the q values for the PEN/silica 0.9 hybrid nanocomposite was $3.71{\times}10^{-20}J$, implying that the incorporation of silica nanoparticles lowers the work required to fold the polymer chains.

• 한국자기공명학회논문지
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• 제10권2호
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• pp.175-187
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• 2006

Binding interactions between a positively charged porphyrin derivative TMAP(meso-tetra(p-trimethylanilinium-4-yl)porphyrin) and triple helical $(dT)_{12}{\cdot}(dA)_{12}{\cdot}(dT)_{12}$, as well as double helical $(dA)_{12}{\cdot}(dT)_{12}$ have been studied with NMR, UV and CD spectroscopy to obtain the detailed information about the binding mode and binding site. UV melting studies showed both DNA duplex and triple helix represented very similar UV absorption patterns upon binding TMAP, but the presence of third strand of triple helical $(dT)_{12}{\cdot}(dA)_{12}{\cdot}(dT)_{12}$, inhibited improvement in thermal stability in terms of melting temperature, $T_m$. In addition, the TMAP molecule is thought to bind to the major groove, according to CD and NMR data. But absence of the clear isosbestic point in UV absorption spectra represented that binding of TMAP to DNA duplex as well as DNA triplex did not show a single binding mode, rather complex binding modes.