A Study of MAO of TiNiZr Ternary Shape Memory Alloys
| Autor: | Lin, Ching-Heng, 林敬恆 |
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| Rok vydání: | 2016 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 This study aimed to modify surfaces of Ti45.5Ni49.5Zr5 and Ti50Ni50 shape memory alloys (SMAs) to decrease Ni contents of the SMA surfaces. First, grit-blasting and acid-etching were conducted to increase the SMA surface roughness. Then, the SMAs were micro-arc oxidized in phosphoric acid electrolyte at constant voltages. The microstructure of the anodic film was investigated by scanning and transmission electron microscopy. X-ray diffraction and x-ray photoelectron spectroscopy were used to characterize film structure. In addition, the adhesive strength of anodic film was evaluated by pull out tests. The influences of the film structure, surface roughness, wettability, and adhesion on the applied voltage (80, 100, 120, and 140 V) and treat tome (4, 6, 8, 10, 15, and 20 min) were investigated. Results show that thickness, pore size, and interpore distance of the anodic film increased with increasing the applied voltage and time. Pores from micro-arc distributed in the anodic film were observed. The anodic film on Ti45.5Ni49.5Zr5, consisting of TiO2, TiO, NiO, ZrO2, and Ni2P, was amorphous. The Ni content decreased from the outer to inner of the anodic film. Furthermore, the micro-arc oxidized SMA surfaces exhibited hydrophilicity. Additionally, crystals were precipitated on the anodic film after hydrothermal treatment. These crystals on Ti45.5Ni49.5Zr5 comprised TiO2, TiO, NiO, ZrO2, and Ni2P. After hydrothermal treatment, the surface roughness of the anodic film on Ti45.5Ni49.5Zr5 and Ti50Ni50 SMA increased and decreased, respectively. After hydrothermal treatment, the surfaces of the anodic film treaded at low voltages (80 and 100 V) transformed to hydrophobic due to the surface consisted of nano-crystals and micro-pores. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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