| Budget Amount *help |
¥4,200,000 (Direct Cost: ¥4,200,000)
Fiscal Year 2001: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2000: ¥3,000,000 (Direct Cost: ¥3,000,000)
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| Research Abstract |
The light emission at the solidification of supercooled liquid material is called recalescence. For instance, an Ag liquid can be cooled far below its melting temperature (960℃) down to 750℃. Such a supercooled liquid shines brightly when it solidifies. Recalescence is generally interpreted in terms of the release of latent heat.
Matsumoto [1] found a sharp peak at the onset of recalescence of Ag droplet floating in the borax. We expect that this signal is related somehow to electronic process occurring at the solid-liquid interfaces in the supercooled metals. To prove this expectation, we have tried to detect such an anomalous emission and to get its spectral information. To clarify the difference between metals and semiconductors, we chose Ag and Ge whose melting points and maximum supercooling temperatures are almost the same.
A specimen, small lump of Ag of about 50 mg, was put into the quartz crucible together with borax (Na4B2O7). The specimen was heated up to 1100℃, and subjected
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to thermal cycle between 1100℃ and 600℃. After several cycles, the solidification temperature began to lower and recalescence was observed. The time evolution of this emission was recorded in the storage oscilloscope. In the case of Ag, the larger the supercooling, the stronger the recalescence intensity. The duration of the recalescence got shorter in accordance with the increase of supercooling ; 150 ms at the maximum supercooling (ΔT=210℃ ). We often observed anomalous onset in the recalescence although it was relatively weak (【less than or equal】10% of the main peak intensity). We are now trying to make spectral analysis of this signal. On the other hand, a Ge liquid solidifies gradually. The recalescence is weaker and its duration is longer than that of Ag. We have not succeeded yet in detecting the onset anomaly of recalescence in the case of Ge. The results will be interpreted by computer simulation of nucleation of solid in the exstremely supercooled liquid taking account of the recent result[2] of crystallization obtained in the space shuttle.
[1] N. Matsumoto ; private communication
[2] Zheng Cheng, P.M. Chaikin, Jixiang Zhu, W.B.Russel and W.V.Meyer, Phys. Rev. Letters, 88, no.1(2002)015501-l. Less
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