The Research on the Superconductivity of 5-element Alloys
| Autor: | Yune-Lin Kuo, 郭岳霖 |
|---|---|
| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 Multi-element alloys are new alloys with over five elements.These alloys usually have both high strength and high hardness.This report is first time to research the superconductivity of these new alloys.A series of 5-element alloy of TiVNbMoTa were fabricated by arc melting method.By the analysis of X-ray diffraction(XRD) patterns and electron diffraction patterns,all specimens were BCC-type structure.Both of nano-size grains and micro-size grains can be observed in these alloys by transmission electron microscope(TEM). For these alloys,the superconductivity critical temperature TC(2K~4K) can be recognized by the on-set of the diamagnetic signal.A large diamagnetic signal confirms that the behavior of superconductivity indeed come from TiVNbMoTa alloy.However,the specimens with the same composition have different critical temperature.This exhibits superconductivity of the alloys are very sensitive with composition and micro-structure.The temperature-independent and positive magnetic susceptibility are observed for all specimens above TC.We considered that the paramagnetism is Pauli paramagnetism which is associated with density of states near Fermi level.For these alloys,the higher TC can be predicated on large density of states.We found that the specimens with higher Pauli paramagnetism susceptibility have higher TC in this study.This exhibits that superconductivity in these 5-element alloys can be explained by BCS theory. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|