High-Throughput Characterization of Surface Segregation in CuxPd1鈥?i>x Alloys

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• 作者：Deepika Priyadarshini ; Petro Kondratyuk ; Yoosuf N. Picard ; Bryan D. Morreale ; Andrew J. Gellman ; James B. Miller
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：May 26, 2011
• 年：2011
• 卷：115
• 期：20
• 页码：10155-10163
• 全文大小：967K
• 年卷期：v.115,no.20(May 26, 2011)
• ISSN：1932-7455

文摘

A high throughput methodology for the study of surface segregation in alloys has been developed and applied to the Cu_xPd_1鈥?i>x system. A novel offset-filament deposition tool was used to prepare Cu_xPd_1鈥?i>x composition spread alloy films (CSAFs), high throughput sample libraries with continuous lateral composition variation spanning the range x = 0.05鈥?.95. Spatially resolved low energy ion scattering spectroscopy (LEISS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the films鈥?top-surface and near-surface compositions, respectively, as functions of alloy composition, x, and temperature. Electron backscatter diffraction (EBSD) was used to identify the bulk phases in the CSAF as a function of alloy composition, x. Films equilibrated by annealing at temperatures 鈮?700 K displayed preferential segregation of Cu to their top-surfaces at all bulk compositions; segregation patterns did not, however, depend on local structure. The Langmuir鈥揗cLean thermodynamic model was applied to segregation measurements made in the temperature range 700鈥?00 K in order to estimate the enthalpy (螖H_seg) and entropy (螖S_seg) of segregation as a function of bulk Cu_xPd_1鈥?i>x composition. Segregation measurements at x = 0.30 on the CSAF compare well with results previously reported for a bulk, polycrystalline Cu_0.30Pd_0.70 alloy, demonstrating the utility of the CSAF as a high throughput library for study of segregation.