Dealloying of Al-based alloys and their mechanisms

Song, T 2015, Dealloying of Al-based alloys and their mechanisms, Doctor of Philosophy (PhD), Aerospace, Mechanical and Manufacturing Engineering, RMIT University.

Document type: Thesis
Collection: Theses

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Title Dealloying of Al-based alloys and their mechanisms
Author(s) Song, T
Year 2015
Abstract Metal based anodes, like tin (Sn), are promising candidate anodes for lithium ion batteries (LIBs) due to their higher specific capacities than traditional graphite electrodes. However, their dramatic volume expansion during lithiation and delithiation could lead to pulverization of the material as well as inadequate cycle life. Materials with nano/microporosity hold promise to accommodate the volume change. This thesis focuses on preparing porous metallic materials for batteries through a dealloying approach. Dealloying is a selective dissolution process, during which one or more active components dissolve from a binary or multicomponent alloy, leaving behind a (nano)porous-structured material enriched in the nobler or less active alloy component(s). In this thesis, porous Sn and nanoporous Cu-Sn composites, which can be used as anodes, and bimodal porous Cu, which can be used as current collector, have been fabricated by dealloying immiscible Al-Sn alloys, ternary Al-Cu-Sn alloy and two-phase Al-Cu alloy, respectively. The dealloying mechanisms of these precursor alloys have been systematically investigated by a variety of means including both ex-situ and in-situ synchrotron X-ray diffraction (XRD). The following findings are most notable.

1) Micro-sized porous Sn (anode material) can be fabricated by dealloying of immiscible Al-Sn alloys.

2) Nanoporous Cu-Sn composite structures (anode material) can be fabricated by concurrent dealloying and realloying of a ternary Al-Cu-Sn alloy.

3) Bimodal porous Cu materials (current collector) can be fabricated from annealing-electrochemical dealloying of Al-Cu alloys.

4) The dealloying of Al2Cu (first dealloyed) and AlCu occurred in sequence and resulted in a hierarchical nanoporous structure.

5)The temperature sensitivity of intermetallic formation in the Cu-Sn system was confirmed by synchrotron studies of the Al67Cu18Sn15 alloy subjected to dealloying at different temperatures (55 °C, 70 °C and 90 °C).

The following findings are most notable.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Aerospace, Mechanical and Manufacturing Engineering
Keyword(s) dealloying
nanoporous structure
immiscible alloys
porous tin
lithium ion battery
bimodal porous structure
synchrotron radiation
crystal structure evolution
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