Thermal Stability of Nanocrystalline Ag–Cu–Al Alloy Films with Densely Dispersed Alumina Particles Prepared via Reactive Sputtering Using Ar–O2 Mixed Gas.
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| Title: | Thermal Stability of Nanocrystalline Ag–Cu–Al Alloy Films with Densely Dispersed Alumina Particles Prepared via Reactive Sputtering Using Ar–O |
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| Authors: | Ueshima, Yoshiyuki1 (AUTHOR) ueshima.yoshiyuki.b39@kyoto-u.jp, Hasegawa, Masakatsu1 (AUTHOR), Kubota, Naoyoshi2 (AUTHOR), Matamura, Yuya1 (AUTHOR), Matsubara, Eiichiro3 (AUTHOR), Seki, Kazuaki4 (AUTHOR), Hirato, Tetsuji1 (AUTHOR) |
| Source: | Metallurgical & Materials Transactions. Part A. Jul2024, Vol. 55 Issue 7, p2264-2281. 18p. |
| Subjects: | Reactive sputtering, Thermal stability, Flux pinning, Thin films, Ostwald ripening, Young's modulus, Heat resistant alloys, Silver |
| Abstract: | To address the challenges associated with the fabrication of highly O2-permeable Ag membranes suitable for on-site and downsized O2 separators for large-scale industrial applications, we investigated nanocrystalline heat-resistant Ag–Cu–Al alloy thin films. Ag–1 at. pct. Al and Ag–2 at. pct. Cu–1 at. pct. Al alloy thin films with nanocrystalline structures were prepared through a reactive sputtering method employing Ar–O2 mixed gas under the condition of supplying excess O/Al flux ratio above the stoichiometric ratio of Al2O3 (> 3/2). To examine the thermal stability of the nanocrystalline Ag alloy films, heating tests were conducted at 350 °C for 1 hour and 300 °C for 1 to 1000 hours in air, and the Ag crystal grain size, nanoindentation hardness, Young's modulus, and electrical resistivity were measured. The results show that the Ag–2 at. pct. Cu–1 at. pct. Al thin film has excellent thermal stability, maintaining its nanostructure with an average grain size of 30 nm after heating at 300 °C for 1000 hours in air. The effects of the addition of 2 at. pct. Cu and the O2 partial pressures during sputtering on the thermal stability of the Ag nanocrystalline structures were discussed using model calculations. It was found that supplying excess O/Al flux ratio above the stoichiometric ratio of Al2O3 (> 3/2) during sputtering reduced the dissolved Al concentration at the Ag grain boundary to substantially zero, almost completely suppressed the Ostwald ripening of nano-sized Al2O3 particles during sputtering and long-term heating, and allowed the Al2O3 particles to maintain high pinning force. Even under the excess oxygen supply conditions of O/Al > 3/2, the 2 at. pct. Cu addition was preferred for further Ag grain refinement in terms of promoting Al2O3 nucleation at the early stage of the film deposition on the substrate due to the effect of suppressing recrystallization of the Ag matrix. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | To address the challenges associated with the fabrication of highly O2-permeable Ag membranes suitable for on-site and downsized O2 separators for large-scale industrial applications, we investigated nanocrystalline heat-resistant Ag–Cu–Al alloy thin films. Ag–1 at. pct. Al and Ag–2 at. pct. Cu–1 at. pct. Al alloy thin films with nanocrystalline structures were prepared through a reactive sputtering method employing Ar–O2 mixed gas under the condition of supplying excess O/Al flux ratio above the stoichiometric ratio of Al2O3 (> 3/2). To examine the thermal stability of the nanocrystalline Ag alloy films, heating tests were conducted at 350 °C for 1 hour and 300 °C for 1 to 1000 hours in air, and the Ag crystal grain size, nanoindentation hardness, Young's modulus, and electrical resistivity were measured. The results show that the Ag–2 at. pct. Cu–1 at. pct. Al thin film has excellent thermal stability, maintaining its nanostructure with an average grain size of 30 nm after heating at 300 °C for 1000 hours in air. The effects of the addition of 2 at. pct. Cu and the O2 partial pressures during sputtering on the thermal stability of the Ag nanocrystalline structures were discussed using model calculations. It was found that supplying excess O/Al flux ratio above the stoichiometric ratio of Al2O3 (> 3/2) during sputtering reduced the dissolved Al concentration at the Ag grain boundary to substantially zero, almost completely suppressed the Ostwald ripening of nano-sized Al2O3 particles during sputtering and long-term heating, and allowed the Al2O3 particles to maintain high pinning force. Even under the excess oxygen supply conditions of O/Al > 3/2, the 2 at. pct. Cu addition was preferred for further Ag grain refinement in terms of promoting Al2O3 nucleation at the early stage of the film deposition on the substrate due to the effect of suppressing recrystallization of the Ag matrix. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 10735623 |
| DOI: | 10.1007/s11661-024-07392-x |
