• Journal of Adhesion and Interface
• /
• v.11 no.4
• /
• pp.162-167
• /
• 2010

In the present work, the effect of electron beam irradiation on the chemical and thermal characteristics of cellulose-based jute fibers was explored by means of chemical analysis, electron spin resonance analysis, ATR-FTIR spectroscopy, thermogravimetric analysis and thermomechanical analysis. Jute fiber bundles were uniformly irradiated in the range of 2~100 kGy by a continuous method using a conveyor cartin an electron beam tunnel. Electron beam treatment, which is a physical approach to change the surfaces, more or less changed the chemical composition of jute fibers. It was also found that the radicals on the jute fibers can be increasingly formed with increasing electron beam intensity. However, the electron beam irradiation did not change significantly the chemical functional groups existing on the jute fiber surfaces. The electron beam irradiation influenced the thermal stability and thermal shrinkage/expansion behavior and the behavior depended on the electron beam intensity.

• Korean Journal of Materials Research
• /
• v.10 no.6
• /
• pp.398-402
• /
• 2000

Three kinds of $Al_3Ti-Cr$ alloys, namely, $Al_{67}Ti_{25}Cr_8,\;Al_{66}Ti_{24}Cr_{10}\;and\;Al_{59}Ti_{26}Cr_{15}$, were prepared by induction melting followed by the thermomechanical treatment. The corrosion behavior in 3.5% NaCl solution and the high-temperature oxidation behavior at 1000, 1100 and $1200^{\circ}C$ for the prepared alloys were investigated. Electrochemical results indicated increased resistance to localized corrosion with increasing Cr content. Cr additions were found to prevent passive film from undergoing brittle fracture. XPS results revealed the passive films of $Al_3Ti-Cr$ alloys were composed mainly of $Al_2O_3$ that coexisted with $TiO_2$ and $Cr_2O_3$. The overall oxidation resistance of the prepared alloys were excellent. Specifically, the oxidation resistance increased in the order of $Al_{59}Ti_{26}Cr_{15},\;Al_{66}Ti_{24}Cr_{10}\;and\;Al_{67}Ti_{25}Cr_8$. As the Al content in the base alloys increased, the $Al_2O_3$ formation was facilitated leading to the increased oxidation resistance.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.12
• /
• pp.261-267
• /
• 2020

The demand for faster, lighter, and thinner portable electronic devices has brought about a change in semiconductor packaging technology. In response, a stacked chip-scale package(SCSP) is used widely in the assembly industry. One of the key materials for SCSP is a die-attach film (DAF). Excellent flowability is needed for DAF for successful die attachment without voids. For DAF with high flowability, two-step curing is often required to reduce a cure crack, but one-step curing is needed to reduce the processing time. In this study, DAF composition was categorized into three groups: cure (epoxy resins), soft (rubbers), hard (phenoxy resin, silica) component. The effect of the composition on a cure crack was examined when one-step curing was applied. The die-attach void and flowability were also assessed. The cure crack decreased as the amount of hard components decreased. Die-attach voids also decreased as the amount of hard components decreased. Moreover, the decrease in cure component became important when the amount of hard component was small. The flowability was evaluated using high-temperature storage modulus and bleed-out. A decrease in the amount of hard components was critical for the low storage modulus at 100℃. An increase in cure component and a decrease in hard component were important for the high bleed-out at 120℃(BL-120).

• Journal of the Microelectronics and Packaging Society
• /
• v.29 no.2
• /
• pp.113-119
• /
• 2022

In order to improve the mechanical reliability of next-generation electronic devices including flexible, wearable devices, a high level of mechanical reliability is required at various flexible joints. Organic adhesive materials such as epoxy for bonding existing polymer substrates inevitably have an increase in the thickness of the joint and involve problems of thermodynamic damage due to repeated deformation and high temperature hardening. Therefore, it is required to develop a low-temperature bonding process to minimize the thickness of the joint and prevent thermal damage for flexible bonding. This study developed flexible laser transmission welding (f-LTW) that allows bonding of flexible substrates with flexibility, robustness, and low thermal damage. Carbon nanotube (CNT) is thin-film coated on a flexible substrate to reduce the thickness of the joint, and a local melt bonding process on the surface of a polymer substrate by heating a CNT dispersion beam laser has been developed. The laser process conditions were constructed to minimize the thermal damage of the substrate and the mechanism of forming a CNT junction with the polymer substrate. In addition, lap shear adhesion test, peel test, and repeated bending experiment were conducted to evaluate the strength and flexibility of the flexible bonding joint.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2011.03a
• /
• pp.83-83
• /
• 2011

나노섬유는 마이크로 섬유에 비해 $10^3$배 정도의 넓은 표면적을 가지며, 다른 섬유와 비교하여 유연성, 투습성과 같은 특성이 우수하다. 나노섬유의 제조방법은 여러 가지가 있으나, 상용화의 가능성, 적용 고분자의 다양성, 제조공정의 단순성, 다양한 제품기술에의 응용성 등을 고려하여 선택하여야 한다. 나노섬유의 제조기술은 방법에 따라 전기방사, 복합방사, 멜트블로운 공정, 에어레이드 공정, 습식 공정 등으로 나눌 수 있다. 전기방사 등 나노섬유를 대량생산하여 상용화하려는 노력을 지속적으로 하고 있으나 나노섬유의 염색가공에 관련되어 기술적 한계로 제품전개에 많은 어려움을 겪고 있다. 그리하여 본 연구에서는 나노섬유 단독으로 제품화하기에는 강도 등의 문제로 PET에 워터펀칭한 복합소재로 개발하여 900nm 이하의 나노섬유에 대한 최적의 날염조건과 현장적용 생산기술을 개발하고자 하였다. 나노섬유 복합소재에 대하여 Brown, Red, Blue, Black 색상의 안료와 Urethane, Rubber, Acrylic, Eco Binder를 사용하여 날염 실험하였으며, 최적의 조건으로 현장생산에 적용하여 생산하였다. 안료의 고착성을 높여 날염성과 염색견뢰도를 증진시키기 위하여 원적외선 열처리기를 개발하여 현장생산에 접목시켰다. 원적외선 열처리기는 벙커C유 또는 가스 등을 사용하는 텐터나 증열기와는 다르게 전기를 에너지원으로 하여 원적외선 램프를 이용한 건열시스템의 형태로 저공해 및 그린 형태의 열처리기 시스템으로, 섬유에 대한 원적외선의 조사거리, 원적외선 램프의 간격, 적용 온도, 원단이송 속도 등에 따른 최적의 원적외선 열처리기 날염조건을 설정하였다. 바인더에 따른 날염성은 우레탄계 바인더를 사용하였을 경우에 가장 선명하고 깊은 색상을 보였으며, 아크릴계 바인더의 경우가 가장 낮은 색상을 보였으며 염색견뢰도는 대체적으로 양호한 결과를 얻었다. 그리고, 최근 환경적인 추세에 맞추어 에코 바인더를 사용하여 날염한 결과 염색성과 내구성 등은 우레탄계와 아크릴계 바인더의 중간 정도의 결과를 보였다.

• Journal of the Korean Vacuum Society
• /
• v.6 no.1
• /
• pp.69-76
• /
• 1997

P-type ($Bi_{0.5}Sb_{1.5}Te_3$) and n-type ($Bi_2Te_{2.4} Se_{0.6}$) thermoelectric thin film were deposited on glass and Teflon substrates by the flash evaporation technique. The changes in thermoelectric properties, such as Seebeck coefficient, electrical conductivity, carrier concentration, carrier mobility, thermal conductivity, and figure of merit, were investigated as a function of film thickness and annealing condition. Figures of merit of the thin films annealed at 473 K for 1 hour were improved to be $1.3{\times}10^{-3}K^{-1}$ for p-type and $0.3{\times}10^{-3}K^{-1}$ for n-type, and they were almost independent of film thickness. Temperature sensors were fabricated from the thin films having the above mentioned properties. And thermo-emf, sensitivity, and time constant of the sensors were measured to evaluate their characteristics for temperature sensors. Thin film sensors deposited on Teflon substrates showed better performance than those on glass substrates, and their sensitivity and time constant were 2.91 V/W and 28.2 sec respectively for the sensor of leg width 1 mm$\times$length 16 mm.

• Applied Chemistry for Engineering
• /
• v.19 no.5
• /
• pp.471-476
• /
• 2008

The thermal and mechanical properties and morphology of epoxy/polyamide/DDS/2E4MZ-CNS reactive blends with various amounts of polyamide were investigated. The amount of polyamide was 10, 20, and 30 phr and 2 phr of catalyst was added to the blend to cure at $180^{\circ}C$ for 30 min. By adding the catalyst, 2E4MZ-CNS, to the blend, the cure reaction occurred at a lower temperature. From the SEM images, it was found that the boundary of separated-phase was unclear and the phase was co-continuous. Without the catalyst, however, the boundary of separated-phase was clear. The control of cure temperature and morphology could be achieved by using a proper catalyst and consequently the mechanical strength increased by 20% compared to the blend without the catalyst due to the strong interaction between epoxy matrix and phase-separated polyamide at the interface.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.1
• /
• pp.56-63
• /
• 2012

In this study, a field applicability of reboiler tube was evaluated by comparing ECT signal with IRIS signal about wall loss rate and remaining wall thickness using worked austenite STS 316L ASME standard calibration tube. In the case of wall-loss rate, as a result, tolerance about $20%{\times}4$ flat bottom hole and 10% O D groove(ECT), 80% defect and 10% O D groove(IRIS) occurred up to ${\pm}15%$. In the case of remaining wall thickness, ECT was satisfied with the both tolerance, but tolerance about 80% defect occurred up to ${\pm}15%$ in IRIS. Therefore, if the IRIS is performed for interpretation of non-relevant indication and measurement of wall-loss rate after ECT, reliability is supposed to be improved.

• 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.

• Journal of the Korean Wood Science and Technology
• /
• v.41 no.3
• /
• pp.234-246
• /
• 2013

It was found that test piece heated rapidly by 3 kW microwave for 5 minutes satisfies the targeted temperature and the percentage of moisture content, and the highest rate of weight increase is obtained in case of 120 minute immersion in the mixture of phosphates and heterocyclic compounds, from the result of such analysis as: kiln drying schedule, flame retardent by flammability test, insect resistance by termites, and permeability of combined penetrant for the wood after assigning multifunctional finish by immersing conifer structural frame, which is used for the frame work of wooden house and indoor/outdoor finishing in flame retardant and insect repellent materials mixture with the remaining heat of microwave. In addition, after a test of flame retardent treated item, it was identified that every mixture of phosphates corresponds with the standards of flame retardent, and upon investigation of moritality of 7 days after putting termites, it was showed that test piece immersed in the mixture of phosphates and heterocyclic compounds has the best characteristics, showing over 96% of high moritality. From the analysis of inward permeability of combined penetrant for the wood, it was decided that excellent performance in the flame retardent and insect resistance of the wood revealed due to full penetration of combined penetrant as it was found that combined penetrant penetrated through the whole inner cells of the wood.