Georgia Institute of Technology Materials Science and Engineering

Committee Members: 

Prof. Gleb Yushin, Advisor, MSE

Prof. Faisal Alamgir, MSE

Prof. Josh Kacher, MSE

Prof. Zhiqun Lin, MSE

Prof. Ting Zhu, ME

"Transformation of Bulk Alloys to Aluminum-Based Metalorganic and Inorganic Nanowires and Their Selected Applications"

Abstract:

One-dimensional (1D) nanomaterials may offer great benefits by enabling superior thermal, mechanical, and electrical properties compared to the conventional particles of the same composition. Their efficient fabrication has been sought after for many decades. Unfortunately, known routes to synthesize ceramic nanowires or nanofibers rely on elaborate procedures, such as catalyst-assisted chemical vapor deposition, physical vapor deposition, hydrothermal synthesis, and the use of sacrificial templates. The usage of catalysts, corrosive or toxic chemicals, and low production efficiencies of conventional synthesis reactors make these manufacturing processes too expensive for many applications and difficult to scale.

Inspired by the breakthrough discovery of the formation of 1D metalorganic NWs directly from 3-dimensional (3D) bulk bimetallic alloys at ambient temperature and pressure, this thesis systematically investigates the mechanisms of their transformation and then leap a step further to the low-cost, lightweight, mechanically strong, and thermally stable of a broad range of functional materials and composites.

Revealing the physical and chemical mechanisms responsible for NWs formation from bulk AlLi alloys are critically needed for pilot-scale and then industrial production. The roles of Li and Al have been revealed by using advanced characterizations for the intermediate and final reaction products. The new mechanistic understanding enabled me to substantially reduce the Li content in the AlLi alloys used for NWs synthesis, enabling significant savings for high-volume production of such NWs. More importantly, this mechanistic understanding enabled me to propose and develop an alternative water-assisted delithiation method to further increase the NW yield, reduce synthesis time and make the process much more industrially friendly. By leveraging the ability of the intermediate NWs to disperse remarkably well in water, an ultra-low-cost method to produce Al2O3 NWs aerogels was also introduced and developed. A lightweight Al2O3 NW-aerogel with epoxy matrix composite was demonstrated with greatly enhanced thermal conductivity for use as a novel and promising thermal interface material. Benefiting from the high mechanical strength and flexibility of Al2O3 NWs, another promising application of Al2O3 NWs reinforced polymer solid-state electrolyte for lithium battery was demonstrated and discussed. Finally, the conversion from the produced Al-organic NWs to Al-inorganic NWs beyond Al-O compounds was explored. A feasible method to produce AlOxFy NWs was demonstrated for the first time. The promising membrane made by AlOxFy with high F content achieved superior flexibility than any other type of Al-based ceramic membranes.