零維奈米鉛粉粒超導偶合強度與粒徑關係探討; Strong-Coupling of The Different Diameter Nano Pb Powders

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题名:	零維奈米鉛粉粒超導偶合強度與粒徑關係探討;Strong-Coupling of The Different Diameter Nano Pb Powders
作者:	周和穆;He-Mo Zhou
贡献者:	物理研究所
关键词:	奈米;耦合強度;超導;鉛;Pb;nano;strong-couping;superconductivity
日期:	2003-06-20
上传时间:	2009-09-22 10:54:45 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	製作奈米鉛粉粒是採用熱蒸鍍法，改變氬氣壓力與鍍源溫度製作出不同粒徑大小的奈米鉛粉粒。加熱電流同為95安培氬氣壓力為0.1torr與0.2torr，製作的奈米鉛粉粒粒徑為4.5nm與13nm，得知壓力越大所成長的奈米粉粒粒徑越大。氬氣壓力為0.3torr加熱電流分別為105安培與110安培，製作的粒徑為6nm與7.5nm，即鍍源溫度越高所成長的奈米粉粒粒徑越大。磁化率實驗，13nm鉛粉粒其 7.10K、 3.13T，9nm鉛粉粒其 7.09K、 4.48T，7.5nm鉛粉粒其 6.8K、 7.49T， 6nm鉛粉粒其 6.6K、 19.79T，因量子效應的關係，粒徑越小其臨界溫度越低。臨界磁場則隨粒徑變小而變大，這可能是只有部分外加磁場能量能影響超導體，需要更高的磁場才能破破壞超導態。對每個樣品作擬合耦合強度值，得知13nm的值為2.22，9nm的值為2.44，7.5nm的值為2.86，6nm的值為3.03，而塊材鉛的的值為2.13，越大超導耦合強度越強，即粒徑越小其表面聲子密度較高，因此超導耦合強度隨粒徑變小而增強。 In this thesis, we use thermal vaper to produce nano Pb powders. By changing Ar pressure and the electric current on the boat to produce different size of nano Pb powders. By the magnetic measure, the critical temperature of 13nm Pb is 7.10K and the critical magnetc field is 3.13 Tesla. The critical temperature of 9nm Pb is 7.09K and The critical magnetic field is 4.48 Tesla.We know the critical temperature is 7.19K and the critical magnetic field is 803 Oe. This means that the diameter of nano Pb powders are smaller the critical temperature is lower but the critical field is higher. It only a little part of applied magnetic field can affect the superconductivity, So it needs more magnetic field to destroy the superconducting state. Bulk Pb is strong- coupling. To simulation every samples, the α value of bulk Pb is 2.13. The α value of 13nm Pb is 2.22. The α value of 9nm Pb is 2.44. The α value of 7.5nm Pb is 2.86. The α value of 6nm Pb is 3.03. So nano powders are smaller the intensity of superconducting coupling are stronger.
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