Low Temperature Magnetic Proterties of Ag-Fe,Ag-Co,Ag-Ni Nanocrystalline Solid Solutions
| Autor: | Wei-Liang Liu, 劉韋良 |
|---|---|
| Rok vydání: | 1999 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 87 The nanocrystalline Ag-Fe, Ag-Co and Ag-Ni solid solutions are prepared by the gas condensation method. The liquid quenching method cannot be used to form a nanocrystalline solid solution, because these systems are immiscible not only in the solid state, but also in the liquid state. In this study evaporate two elements to gas phases by heating source and then quench to liquid nitrogen temperature to form nanocrystalline solid solutions. The particle’s sizes of nanocrystalline solid solutions will be controlling by the chamber pressure. The solubility of nanocrystalline solid solution depends on that controlling the mean particle's sizes and the mole percentage of evaporating source elements. All of these nanocrystallines solid solutions will heating by different thermal treatment. The ferromagnetic materials systems magnetism is depend on the mean particle's sizes and solubility that will be discussed. Also, the temperature dependence of the magnetic properties will be analyzed and related to the microstuuctural changes produced during the thermal treatments. The change of lattice constant with the solubility will be discussion. The nanocrystallines solid solutions were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), differential scanning calorimetry (DSC), superconducting quantum interference devices (SQUID) and extended X-ray Absorption Fine Structure (EXAFS). The average compositions of the NC Ag-M (Fe, Co, Ni) system are analyzed by SEM/EDS is closed to the gross composition of the raw materials. From the data of DSC, we can obtain the temperature of Ag-M system. The NC Ag-Fe system is about 580℃, the NC Ag-Co system is about 400℃ and the NC Ag-Ni system is about 320℃. To realize the change of the magnetization (Ms) from room temperature to 5 k in these three NC solid solution and the change of remanence (Mr) and coercivity (Hc) in room temperature and 5k by SQUID. The data of EXAFS show that there are not different electronic states between NC Ag-Fe soilid solution and Fe. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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