| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2003: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2002: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
Synthesizing techniques for highly efficiency thermoelectric material NaCo2O4 have been examined. Usual sintering method, hot press method, plasma-sintering method, pressing method at air, melt solidification method were tried. Appropriate amount of Na2Co3 and Co oxide powder were mixed and grind in a boll mill by using methanol. The mixed powder was dried and sintered at 880℃ for 12h or 24 h. The precursor was again grind in the boll mill to make powder. Then the powder was sintered by various techniques. One is hot pressed at various temperatures for various anneal times. One is shaped to 5 mm x 6mm x 20mm size in a pressed mold. The specimens were sintered in a temperature range from 880〜1000℃ for various anneal times. Some of the specimens were pressed in an air atmosphere under 10kgf/cm^2 to make porous specimen to precise specimen. Some of powder is sintered in a plasma sintering machine in the temperature range 700〜850℃ for 5 min〜15min. Some of specimens with 5 mm x 6mm x 20mm i
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n size were heated up to 1100℃ and they were melted and slowly cooled to 950℃.Synthesizing techniques for highly efficiency thermoelectric material NaCo2O4 have been examined. Usual sintering method, hot press method, plasma-sintering method, pressing method at air, melt solidification method were tried. Appropriate amount of Na2Co3 and Co oxide powder were mixed and grind in a boll mill by using methanol. The mixed powder was dried and sintered at 880℃ for 12h or 24 h. The precursor was again grind in the boll mill to make powder. Then the powder was sintered by various techniques. One is hot pressed at various temperatures for various anneal times. One is shaped to 5 mm x 6mm x 20mm size in a pressed mold. The specimens were sintered in a temperature range from 880〜1000℃ for various anneal times. Some of the specimens were pressed in an air atmosphere under 10kgf/cm^2 to make porous specimen to precise specimen. Some of powder is sintered in a plasma sintering machine in the temperature range 700〜850℃ for 5 min〜15min. Some of specimens with 5 mm x 6mm x 20mm in size were heated up to 1100℃ and they were melted and slowly cooled to 950℃.
We could not make porous specimen to precise specimen by any other method such as hot press method, plasma sintering method and melt and solidification method excepting by pressing them at air atmosphere. However, thermoelectric properties of these precise specimens are not so much better than that made from by usual sintering method. They are only 20% better than the usual sintering method. The reasons were expected that Na atoms evaporated from specimens or excess Na atoms were absorbed from Na2Co3 powder, which were put around the specimen to prevent the evaporation of Na atoms. Consequently, the most important problem is how to control the Na concentration at the best condition. Less
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