• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.964-968
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• 1996

The demands of size and quality of large steel shaft forgings for ship building, power plant, steel plant, etc. are rapidly increasing, and some of these productions are manufactured from ingot weighing more than 300 tons. For use as rotating components. shafts require toughness, strength and homogeneity, and therefore are produced through a variety of heat treatments. According to the increase of ingot size, micro- and macrosegregation and also mass effect of the product increase. Thus, special care should be paid to the heat treatment of such large shaft forgings. In this paper, the heat treatment of large shaft forgings such as rotor and back-up roll is calculated using the commercial finite element code SYSWELD. Calculated distributions of temperature and phase are compared with experimental data. The continuous cooling transformation diagram, thermal and mechanical properites of each phase are used. The phase proportion, hardness and residual stress during water quenching are discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.164-168
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• 1996

The relation between crystallinity and thermal history in low density polyethylene thin films and their effect on electric conduction phenomena and dielectric breakdown was studied. The low density polythylene thin films obtained by the solution growth method heat-treated at 140[$^{\circ}C$] for 2 h and subsequently cooling to various ways. The degree of crystallinity was estimated by the X-ray diffraction measurement for the specimen of slowly cooling, ICE quenching and liquid nitrogen quenching. The result shows that the crystallinity decreases become faster as the cooling speed increased, and that conduction phenomenon is governed by the space charge limited current in high field. It was found that the dielectric breakdown field increases with an increase in cooling speed and test number in self-healing breakdown method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.157-161
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• 2000

Blue phosphor of Ba-Mg-Al-O:Eu$^{2+}$ phase was fabricated by conventional firing techniques under reducing atmosphere and its photoluminescence properties are studied with varying Eu concentration and phost-annealing temperature under air atmosphere. This phosphors were well crystallized with particle size in the range of 3~5um and emitted a blue light at a dominent wavelength 450nm for 254nm UV irradiation. The concentration quenching wit Eu$^{2+}$ was that with increasing Eu concentration the energy transfer between the activator ions steadily improves, so that the excitation energy is transported over larger distances through the lattice before luminescence can occur. Thermal quenching also occurred in this phosphor means that in a host lattice with the $\beta$-alumina structure the bond of an Eu$^{2+}$ ion with the nearest-neighbour oxygen ion is much stronger than in a lattice with the magnetoplumbite structure.cture.

• Journal of the Korean Society of Combustion
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• v.6 no.1
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• pp.14-19
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• 2001

Interests and importance of down-scale combustor is increasing with the emerging need for miniaturized power source which is now a bottleneck of micro system development. But in down scaled combustor increased heat loss compared to thermal energy generation inhibits the usability and application of the device, so as a preliminary work of down scaled combustor fabrication. Modeling tool for the device should be established, in this study modeling approach of closed vessel combustion phenomena that can express heat loss effect and resulting quenching is proposed and the result is compared with experiment data. From this model heat loss effect following combustor scale down can be further understood, and further more design parameter and analysis tool can be obtained.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.1
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• pp.12-23
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• 1995

In this a set of constitutive equation relevant to the analysis of thermo-elasto-plastic materials with phase transformation during quenching process was presented on the basis of continuum thermo-dynamic. In calculating the transient thermal stresses, temperature between coolant and specimen(SM45C) surface was determined from the heat transfer coefficient. A calculation was made for specimen with 40mm in diameter quenched in coolant from $820^{\circ}C$ and the results are as follow. Stresses at starting point of transformation always show the maximum tensile value. Reverse of stresses takes place after completion of transformation of inner part at specimen.

• Journal of the Korean Ceramic Society
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• v.42 no.8 s.279
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• pp.532-536
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• 2005

Thermal shock resistance of structural ceramics is a property that is difficult to quantity, and as such is usually expressed in terms of a number of empirical resistance parameters. These are dependant on the conditions imposed, but one method that can be used is the examination of density, Young's modulus and thermal expansion retention after quenching. For high temperature applications, long-annealing thermal durability, cycle thermal stability and residual mechanical properties are very important if these materials are to be used between $1000^{\circ}C$ and $1300^{\circ}C$. In this study, an excellent thermal shock-resistant material based on $Al_2TiO_5-mullite$ composites of various compositions was fabricated by sintering reaction from the individual oxides and adjusting the composition of $Al_2O_3TiO_2/SiO_2$ ratios. The characterization of the damage induced by thermal shock was done by measuring the evolution of the Young's modulus using ultrasonic analysis, density and thermal expansion coefficients.

• Journal of Conservation Science
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• v.27 no.4
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• pp.421-430
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• 2011

Thermal conditions in practice at the traditional bronze workshop of the Korean Folk Village in Yongin were examined along with the microstructures of some high tin bronze objects made there. Laboratory experiments approximating the conditions of the workshop were also carried out and the results were compared. The operating temperature of the workshop furnace was measured to range from $750^{\circ}C$ to $850^{\circ}C$ while the surface temperature of an object, upon its removal from the furnace for additional thermo-mechanical treatments, was generally in the range of $600^{\circ}C$ to $685^{\circ}C$. This variation in working temperatures was reflected in varying microstructures developed upon quenching. The products of the Folk Village were found to consist of microstructures where the ${\alpha}$ grains of the Cu-Sn system were distributed in the background of different phases including the ${\beta}$-martensite phase, retained ${\gamma}$ phase, ${\alpha}+{\delta}$ eutectoid or their mixtures. This variability, which is also identified in objects made in ancient times as well as in our laboratory experiments, suggests that the actual thermal conditions given during the quenching treatments are much more complicated than is inferred from the temperature measurements. This paper will present detailed accounts of the thermo-mechanical treatments as observed in the high tin bronze workshop of the Korean Folk Village and discuss the evolution of varying microstructures in terms of the substantial variability involved in the implementation of the traditional forged high tin bronze technology of Korea.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.369-369
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• 2011

In the current work, we demonstrate the gas phase plasma synthesis of ultrafine boron nanoparticles by decomposing boron trichloride (BCl3) gas in an argon-hydrogen thermal plasma and quenching the hot plasma by expansion through a ceramic nozzle, driving the homogeneous nucleation of nanoparticles. It is shown that ultrafine nanoparticles can be produced from the experiments. We also show the characterization results regarding the oxidation of boron nanoparticles at room temperature using X-ray Photoelectron Spectroscopy (XPS) and the combined Scanning Transmission Electron Microscope (STEM) and Electron Energy Loss Spectroscopy (EELS).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.33-34
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• 2008

$Ge_1Se_1Te_2$ chalcogenide amorphous materials was prepared by the conventional melt-quenching method. Samples were prepared by e-beam evaporator system and thermal evaporator technique. The thermal properties were investigated in the temperature range 300K-400K and the electrical properties were studied in the voltage range from 0V to 3V below the corresponding glass trasition temperature. The obtained results agree with the electrothermal model for Phase-Change Random Access Memory.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.167-169
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• 1998

Recently $SF_6$ gas circuit breakers utilizing the thermal-expansion principle are increasingly used in distribution power system. Active researches and developments have been conducted to reduce the size and weight, and to improve the interrupting performance of the circuit breakers. It was first developed a programme which could show the hot gas flowing into the thermal-expansion arc chamber. This programme, using so-called FLIC method basically, adopted 'Simplified Enthalpy Arc Model' which was somewhat modified to estimate the arc quenching process. The computation by it was compared with the measured results of the pressure rise in the chamber, and both showed fairly good agreement.