THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Friday, November 15, 2019
in MRDC 4211
will be held the
DISSERTATION PROPOSAL DEFENSE
"Strain-Induced Transformation of Bulk Alloys to Aluminum-Based Metalorganic and Inorganic Nanowires and Their Selected Applications"
Prof. Gleb Yushin, Advisor, MSE
Prof. Zhiqun Lin, MSE
Prof. Faisal Alamgir, MSE
Prof. Joshua Kacher, MSE
Prof. Ting Zhu, ME
Fabrication and applications of lightweight, high loadbearing, thermally stable composite materials would beneﬁt greatly from leveraging the high mechanical strength of ceramic nanofibers (often called nanowires (NWs)) over conventional particles or micrometer-scale ﬁbers. However, most conventional synthesis routes to produce NWs rely on using expensive synthesis tools and employing corrosive or dangerous chemicals and suffer from relatively low production yield and low synthesis throughput, which makes NW use prohibitively expensive for most commercial applications. The breakthrough discovery of the formation of 1-dimensional (1D) metalorganic NWs directly from 3-dimensional (3D) bulk bimetallic alloys at ambient temperature and pressure enabled a new low-cost manufacturing pathway for a broad range of functional ceramic (nano)materials and (nano)composites. This method was first demonstrated by a facile transformation of polycrystalline aluminum-lithium (AlLi) alloy particles to Al alkoxide NWs, which can be further transformed to mechanically robust Al oxide (Al2O3) NWs. However, the transformation mechanisms had not been clearly understood initially.
For this work, I aimed to gain a deeper fundamental understanding of the bulk alloy-to-NW transformation processes, investigate a broader use of suitable organic solvents for metalorganic NW synthesis, explore the formation of ceramics beyond metal oxides and reveal complex processing-structure and structure-property relationships for the formation of ceramic NWs from their metalorganic NW precursors.
In my initial studies, I focused on utilizing advanced materials characterization techniques (such as electron microscopy (SEM and TEM), liquid and solid-state nuclear magnetic resonance (NMR) spectroscopies, among others) to elucidate key physical and chemical mechanisms responsible for the NWs formation. The new mechanistic understanding enabled me to further upgrade the synthesis strategy by reducing Li content in the AlLi alloy. In addition, I was able to accelerate and simplify the synthesis process by using cheaper solvents without compromising the success of the NWs synthesis. After establishing a successful and reproducible synthesis of 1D Al alkoxide NWs, I started to study their further conversion to various Al-based inorganic NWs, such as Al oxyfluoride NWs, Al fluoride NWs, Al oxynitride NWs and Al nitride NWs, among others. Such transformation processes will be investigated systematically in the course of my thesis and the nanomechanical properties of the NWs, including Young’s modulus and tensile strength of individual Al-based inorganic NW will be studied via both atomic force microscope-based and micro-electromechanical systems-based techniques. Some of their potential applications, such as separators for use in batteries, reinforcement additives for advanced concretes, moisture and chemical sensors and others may be additionally explored.