The Oxidation Behavior of Pd-based Amorphous Alloys in Dry Air

• Main Authors: I-Fei Jen, 任一飛
• Other Authors: Wu Kai
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/68193260839388678016

碩士 === 國立臺灣海洋大學 === 材料工程研究所 === 96 === The purpose of this thesis is to study the oxidation and crystallization behaviors of Pd40Ni40P20 (Pd3-BMG) and two different Pd43Cu?27????Ni10P20 glassy alloys, containing 0 (Pd4-BMG) and 45% porosity (Pd4-AMF), over the temperature range of 250~450oC in dry air. In general, the oxidation kinetics of the Pd3-BMG and Pd4-amorphous alloys followed the three-stage and two-stage parabolic rate law, respectively. In addition, the oxidation kinetics of the three Pd-based BMGs increased with increasing temperature. Based on the results of short-term oxidation, the Pd3-BMG underwent a pre-crystallization and then, oxidation reaction, while the reverse situation was observed for the Pd4-based alloys. According to the XRD analyses, the scale formed on the Pd3-BMG was exclusive NiO, and its oxidation rates were faster those that of pure nickel. On the other hand, the scale formed on the two Pd4-based amorphous alloys was exclusive CuO, and their oxidation rates were slower than those of pure copper. Moreover, the Pd3-BMG substrate transformed to form the Pd3P and Ni3P phases, while the Pd3P, Cu3P and Ni2Pd2P phases were detected for the Pd4-based substrates after the oxidation. The Pd-enriched layer of the (Pd3P) was observed beneath the NiO scale in the Pd3-BMG, however, no enriched layer was found in the Pd4-based BMG. In addition, it was found that the oxidation rates of the Pd4-BMG were slightly faster than those of Pd4-AMF, indicating that the porosity present in the amorphous alloy provided a beneficial effect in reducing the oxidation reaction. In summary, the Pd4-AMF amorphous alloy had a better thermal stability, while the Pd3-BMG had a better oxidation resistance.