• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.308-311
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• 2012

A wide range of possible hazards existing in thermal batteries are mainly caused by thermal runaway, which results in overheating or explosion in extreme case. Battery separators ensure the separation between two electrodes and the retention of ion-conductive electrolytes. Thermal runaways in thermal batteries can be significantly reduced by the adoption of these separators. The high operating temperature and the violent reactivity in thermal batteries, however, have limited the introduction of conventional separators. As a substitute for separators, MgO powders have been mostly used as a binder to hold molten salt electrolyte. During recent decades the fabrication technology of ceramic fiber, which has excellent mechanical strength and chemical stability, has undergone significant improvement. In this study we adopted wet-laid nonwoven paper making method instead of the electrospinning method which is costly and troublesome to produce in volume. Polymeric precursor can readily be coated on the surface of wet-laid ceramic paper, and be formed into ceramic film after heat treatment. The mechanical strength and the thermo-chemical stability as well as the wetting behaviors of ceramic separators with various molten salts were investigated to be applicable to thermal batteries. Due to their excellent chemical, mechanical, and electrical properties, wet-laid nonwoven separators made from ceramic fibers have revealed positive possibility as new separators for thermal batteries which operate at high temperature with no conspicuous sign of a short circuit and corrosion.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.294-297
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• 1997

Two kinds of thermo-mechanical treatments(TMT) were applied to two AA3104 alloys. Tensile test, cupping and mesurement were conducted. Height and angular positions of earings in the drawn cups were explained by ODF on the contents of alloying elements. The tensile strengths measured in RD+45$^{\circ}$direction were generally lower than those measured in RD and TD directions. The textures of the experimental alloys were determined as shear texture {100}<011> and Cube texture {100}<001> by ODF's. Some optimum ratio of shear texture {100}<011> and Cube texture {100}<001> for reducing earings was found.

• 한국재료학회지
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• 제26권5호
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• pp.235-240
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• 2016

Appropriate thermo-mechanical properties of nickel-based superalloys are achieved by heat treatment, which induces precipitation and solid solution hardening; thus, information on the temperature ranges of precipitation and dissolution of the precipitates is essential for the determination of the heat treatment condition. In this study, thermal analyses of nickel-based superalloys were performed by differential scanning calorimetry method under conditions of various heating rates of 5, 10, 20, or 40K/min in a temperature range of 298~1573K. Precipitation and dissolution temperatures were determined by measuring peak temperatures, constructing trend lines, and extrapolating those lines to the zero heating rate to find the exact temperature under isothermal condition. Determined temperatures for the precipitation reactions were 813, 952, and 1062K. Determined onset, peak, and offset temperatures of the first dissolution reaction were 1302, 1388, and 1406K, respectively, and those values of the second dissolution reaction were 1405, 1414, and 1462K. Determined solvus temperature was 1462K. The study showed that it was possible to use a simple method to obtain accurate phase transition temperatures under isothermal condition.

• 한국기계가공학회지
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• 제19권7호
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• pp.60-66
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• 2020

In order to improve fatigue life of transmission gear carburizing is normally used. Carburizing is a very good process to achieve low cost and high performance. The machined gears are heated up to carburizing temperature and then cooled rapidly in an oil bath to produce high surface hardness. The gears may undergo excessive thermal distortion during heating and rapid cooling. In order to predict the distortion during heating and rapid cooling, a coupled thermo-mechanical simulation is needed. In the current research, the simulation of heating and cooling was performed. The results show that the thermal distortion and the residual stresses are well predicted by the coupled simulation. In addition, induction heating and rapid cooling simulation is carried out to predict the thermal distortion. The amount of distortion is compared. It is shown that induction heating is very effective to reduce thermal distortion.

• 대한금속재료학회지
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• 제46권1호
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• pp.26-32
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• 2008

Examination of two bronze vessels supposedly from the Koryo dynasty revealed that they consist of bowls and stands that are fixed together using rivet joints made of Cu-Ag alloys. The bowls and stands were forged out of unleaded bronze alloys of approximately 22 weight % Sn before being quenched from the ${\alpha}+{\beta}$ region of the Cu-Sn phase diagram. This specific alloy and the thermo-mechanical treatment constitute two key elements of the unique technical tradition called Bangcha (방짜) that has long been established in Korea. The high Sn content ensures better casting and the thermal treatment causes the brittle ${\delta}$ phase to be avoided in forging as well as in services. The experiment on the laboratory Cu-Ag alloys of varying Ag contents suggested that the Cu-Ag system was the best choice of materials for the rivets at the time in view of their color, availability, ductility and low melting points.

• 한국분말재료학회지
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• 제19권4호
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• pp.253-258
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• 2012

The characteristics of $Al_2TiO_5$ ceramics were influenced by the additives and the heat treatment that controls the microcrack behavior at grain boundaries. The effect of additives on $Al_2TiO_5$ ceramics were investigated in terms of mechanical properties and thermal expansion at high temperature. The $Al_2TiO_5$ were synthesized at $1500^{\circ}C$, $1550^{\circ}C$ and $1600^{\circ}C$ for 2h by reaction sintering. The formation of $Al_2TiO_5$ phase was increased by additives that enhanced the volume of the microcrack that can lead to low thermal expansion. The mechanical properties of the stabilized $Al_2TiO_5$ ceramics were increased remarkably at $1100^{\circ}C$, $1200^{\circ}C$ and $1300^{\circ}C$ due to the oneset of mechanical healing of grain-bondary microcracks at a high temperature. The amount of microcrack was decreased at lower sintering temperature that causes the increase of mechanical properties at high temperature.

• 폴리머
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• 제31권1호
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• pp.31-36
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• 2007

플라스마 표면처리는 전체적인 물성은 유지하고 표면의 특성만을 변화시킨다고 전해지고 있다. 이번 연구에서는 플라스마 처리에 의해 높은 발수성을 나타내는 나일론 6 섬유로의 개질을 시도하였다. 발수성을 나타내는 나일론 섬유는 가스 종류, 처리시간, 인가 파워를 변수로 하여 RF 진공 플라스마 시스템에서 처리되었다. 플라스마 처리된 섬유의 표면을 scanning electron microscopy(SEM)과 atomic force microscopy(AFM)으로 모폴로지 변화를 살펴보았으며, 기계적 특성과 고분자 고유의 특성을 인장강도와 Differential scanning calorimetry(DSC), thermo-gravimetric analysis (TGA)로 각각 분석하였다. 또한 나일론 섬유의 발수성 평가는 물방울 흡수시간으로 테스트를 실시하였다. 이러한 결과들은 플라스마 표면처리로 인해서 나일론 섬유의 발수성이 향상됨을 나타내었다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.3-9
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• 1999

The grain morphology, the changes in morphology and Jc with the thermo-mechanical treatment (TMT) history, the field dependence of Jc and the nature of intergranular bonding were studied in $T_{10.8}$$Pb_{.2}$$Bi_{0.2}$$Sr_{1.8}$$Ba_{0.2}$$Ca_{2.2}$$Cu_{3}$$O_{z}$/Ag tapes. As a result, incorporation of intermediate rolling during the final heat-treatment resulted in of plate-like TI-1223 grains, and thus enhanced Jc. Jc's near 2.5$\times$104 A/cm2 at 77 K and 0 T were obtained in just rolled tapes with an excellent reproducibility. The high Jc's seem to grain-connectivity easy recovery of excellent grain-connectivity during final heat-treatment after inter -mediate rolling, probably due to retarded T1 evaporation and excessive Ca content in the present composition. The strong field dependence of Jc even in low fields, however, indicated that there still existed significant weak-links and the degree of directional grain-alignment was far from the desired one. The intergranular binding in the tapes seemed to be mainly dominated by SIS junctions.

• Nuclear Engineering and Technology
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• 제46권1호
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• pp.117-124
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• 2014

The effect of various process variables on the powder properties of recycled $U_3O_8$ from MnO-$Al_2O_3$ doped large grain $UO_2$ pellets and the effect of those recycled $U_3O_8$ powders on the sintered density and grain size of MnO-$Al_2O_3$ doped large grain $UO_2$ pellets have been investigated. The evolution of morphology, size, and BET surface area of the recycled $U_3O_8$ powders according to the respective variation of the thermo-mechanical treatment variables of oxidation temperature, powder milling, and sequential cyclic heat treatment of oxidation and then reduction was examined. The correlation between the BET surface area of recycled $U_3O_8$ powder and the sintered pellet properties of MnO-$Al_2O_3$ doped pellets showed that the pellet density and grain size of doped pellets were increased and then saturated by increasing the BET surface area of the recycled $U_3O_8$ powder. The density and grain size of the pellets were maximized when the BET surface area of the recycled $U_3O_8$ powder was in the vicinity of $3m^2/g$. Among the process variables applied in this study, the cyclic heat treatment followed by low temperature oxidation was a potential process combination to obtain the sinter-active $U_3O_8$ powder.

• 분석과학
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• 제14권1호
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• pp.50-58
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• 2001

압연판재의 결정립 미세화를 위해 새롭게 도입된 극저온 강압연법을 극저온 압연법, 상온 강압연법과 비교 분석하였다. EBSD를 이용하여 결정립 구조를 분석하였으며, 결정립 크기를 측정하였다. 극저온 압연법과 상온 강압연법은 각각 39%와 87%의 결정립 크기 감소효과를 보였으며, 극저온 강압연법은 상온 강압연법과 비슷한 결정립 감소효과를 갖고 있었다. 따라서 강압연법이 극저온 압연법보다 결정립 미세화에 훨씬 더 효과적임을 알 수 있었다.