(116f) Topological Transitions of Spiral Nanocomposites in Extreme Environments
AIChE Annual Meeting
2020
2020 Virtual AIChE Annual Meeting
Materials Engineering and Sciences Division
Characterization and Processing of Nanocomposites
Monday, November 16, 2020 - 9:15am to 9:30am
Here, we investigate the thermal stability of these spiral nanocomposites through continuous isothermal annealing near their eutectic temperature using in situ X-ray nano-tomography (nTXM), and further corroborated by ex situ crystallographic and compositional analyses. Collectively, the results identify that the structure does not evolve self-similarly, with topological breakdowns in both short- and long-term annealing due to reactive and bulk diffusion, respectively: (i) Within minutes, solid-state, reactive diffusion (a high Damkohler number event) leads to phase transition from the metastable to the stable phase, which in turn causes lamellar pinch-off of the thinner portions of the intermetallic phase. (ii) During prolonged annealing (hours), bulk diffusion due to Ostwald coarsening leads to more pinch-off events and thus the formation of a greater number of disjoint components of the intermetallic phase. By unearthing the above solid-state dynamics, this study helps to generate accurate structure-performance relationships that could guide the future application of these spiral in situ composites in extreme environments.
[1] S. Moniri et al., Small 16, 1906146 (2020).