• Korean Journal of Materials Research
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• v.14 no.5
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• pp.310-314
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• 2004

Mechanical alloying (MA) of Ti-50.0～66.7at%Si powders was carried out in a high-energy ball mill, and in situ thermal analysis was also made during MA. In order to classify the synthesis behavior of the powders with respect to at%Si, the synthesis behavior during MA was investigated by in situ thermal analysis and X-ray diffraction (XRD). In situ thermal analysis curves and XRD patterns of Ti-50.0～59.6at%Si powders showed that there were exothermic peaks during MA, indicating TiSi, $TiS_2$, and $Ti_{5}$ $Si_4$ phase formation by a rapid exothermic reaction of self-propagating high-temperature synthesis (SHS). Those of Ti-59.8～66.7 at%Si powders, however, showed that there were no peaks during MA, indicating any Ti silicide was not synthesised until MA 240 min. For Ti-50.0～59.6at%Si powders, the critical milling times for SHS increased from 34.5 min to 89.5 min and the temperature rise, $\Delta$T (=peak temperature-onset temperature) decreased form $26.2^{\circ}C$ to $17.1^{\circ}C$ as at%Si increased. The critical composition of Si for SHS reaction was found to be 59.6at% and the critical value of the negative heat of formation of Ti-59.6at%Si to be -1.48 kJ/g.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.141-141
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• 2010

The effect of thermal anneal on the characteristics of structural properties and the enhancement of luminescence and photovoltaic (PV) characteristics of silicon-rich silicon-nitride films were investigated. By using an ultra high vacuum ion beam sputtering deposition, B-doped silicon-rich silicon-nitride (SRSN) thin films, with excess silicon content of 15 at. %, on P-doped (n-type) Si substrate was fabricated, sputtering a highly B doped Si wafer with a BN chip by N plasma. In order to examine the influence of thermal anneal, films were then annealed at different temperature up to $1100^{\circ}C$ under $N_2$ environment. Raman, X-ray diffraction, and X-ray photoemission spectroscopy did not show any reliable evidence of amorphous or crystalline Si clusters allowing us concluding that nearly no Si nano-cluster could be formed through the precipitation of excess Si from SRSN matrix during thermal anneal. Instead, results of Fourier transform infrared and X-ray photoemission spectroscopy clearly indicated that defective, amorphous Si-N matrix of films was changed to be well-ordered thanks to high temperature anneal. The measurement of spectral ellipsometry in UV-visible range was carried out and we found that the optical absorption edge of film was shifted to higher energy as the anneal temperature increased as the results of thermal anneal induced formation of $Si_3N_4$-like matrix. These are consistent with the observation that higher visible photoluminescence, which is likely due to the presence of Si-N bonds, from anneals at higher temperature. Based on these films, PV cells were fabricated by the formation of front/back metal electrodes. For all cells, typical I-V characteristic of p-n diode junction was observed. We also tried to measure PV properties using a solar-simulator and confirmed successful operation of PV devices. Carrier transport mechanism depending on anneal temperature and the implication of PV cells based on SRSN films were also discussed.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.987-988
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• 2004

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1339-1346
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• 1996

• Proceedings of the Korean Vacuum Society Conference
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• 1995.06a
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• pp.37-37
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• 1995

• Proceedings of the Korean Fiber Society Conference
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• 2001.04a
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• pp.43-46
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• 2001

• Proceedings of the Korean Vacuum Society Conference
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• 2001.07a
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• pp.74-74
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• 2001

• Bulletin of the Korean Chemical Society
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• v.16 no.2
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• pp.79-81
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• 1995

• Korean Journal of Food Science and Technology
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• v.29 no.5
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• pp.860-868
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• 1997

The effects of oil unsaponifiables (8 species) and methanolic plant extracts (53 species) on the thermal oxidation of oils during 14 or 16 hour heating at $180^{\circ}C$ were studied by analyzing the fatty acid composition of soybean oil or cottonseed oil. All the unsaponifiables tested did not show any antioxidative activities on the thermal oxidation of soybean oil. However, among the 53 species of methanolic plant extracts, some species (Rheum undulatum L., Chelidonium majus L. var. asiaticum and Eugennia caryopyllata T.) showed very strong antioxidative activities on the thermal oxidation of cottonseed oil. The antioxidative activities of methanolic extracts of these 3 species on thermal oxidation of cottonseed oil during an extended heating period were also studied by heating cottonseed oils for 7 hours a day for 8 days at $180^{\circ}C$. The methanolic extracts of Chelidonium majus L. v. asiaticum and Eugennia caryopyllata T. greatly reduced both polymer formation and linoleic acid decomposition after the 8 day heating at $180^{\circ}C$. However, the methanolic extracts of Rheum undulatum L. was effective for the reduction of polymer formation, but not for the reduction of linoleic acid decomposition.

• Polymer(Korea)
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• v.28 no.1
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• pp.35-40
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• 2004

The formation mechanism of void defect which deteriorate composite's property is various according to each composite process. In this paper, void formation and growth mechanism is analyzed by thermal analysis and GC/MS. We made a vacuum chamber for observing pressure effect. Thermal analysis has been done in various condition. Elements of volatiles during resin curing were turned out by GC/MS. The most of volatiles of polyester were composed of styrene (over 80%) and a small quantity of toluene. In case epoxy resin, butyl glycidyl ether was the main element of volatiles (over 90%). We concluded that the original sites of void growth existed in resin and they were eliminated by vacuum and heating process. And the growth of void was influenced by water, diluents, solvent, and reactants in resin.