Xia, Rogers, and Henry Receive NSF CAREER Awards
Three Woodruff School faculty members recently won NSF CAREER Awards. These faculty members include Shuman Xia, Jonathan Rogers, and Asegun Henry. In addition, Assistant Professor of Aerospace Engineering Wenting Sun, who holds a joint appointment in the Woodruff School, was recently selected for an AFOSR Grant. Below you will find further information on each of these projects that have been awarded.
In Situ Nanomechanics of High-Performance Anode Materials for Sodium-Ion Batteries
As one of the most widespread technologies for energy storage, lithium-ion batteries have been under intense studies over the past two decades. Sodium-ion batteries are being considered as a low-cost alternative because sodium is much more earth abundant and less geographically constrained than lithium. However, the development of advanced sodium-ion batteries has been hindered by a significant unexplored gap in understanding the mechanics of high-performance electrode materials. This project aims to bridge such a gap by characterizing the nanomechanical and electrochemical interactions in sodium-ion battery electrode materials and developing constitutive models to elucidate the morphological and structural evolution in these materials.
Energy storage and release of sodium-ion battery electrodes involves a complex set of mechanical and electrochemical processes, including deformation, stress generation, mass transport, phase transformation, and chemical reaction. A fundamental understanding of the mechanics and its strong coupling with other physical phenomena is required to achieve breakthroughs in the sodium-ion battery technology. The research objective of this award is to develop an in situ nanomechanical testing platform for the constitutive characterizations of sodium-ion battery electrode materials. The experimental framework will be employed to investigate the in situ mechanics of sodiated/desodiated germanium and germanium-tin alloys, which are two promising high-performance anode materials for advanced sodium-ion batteries. The space- and time-resolved constitutive behaviors from experimental measurements will be incorporated into a continuum computational model for predictive simulations of the mechanical degradation and morphological evolution in solid electrode materials.
Causation in Dynamical Systems: Bridging the Gap Between Data Analytics and System Identification
System identification is the process of building a model for a physical system from observed experimental data. System ID processes are used in a wide variety of scientific and engineering applications from weather prediction to aircraft design. While numerous system ID algorithms have been developed to date, many current methods yield poorly performing models when applied to complicated physical systems involving numerous interacting components. However, recent advancements in data analytics (the study of “big data”) have yielded new algorithms that can identify patterns, and specifically causal relationships, in data. This award supports fundamental research exploring how these new data analysis tools can inform the system ID process and enable a new class of system ID algorithms specifically applicable to large-scale, complex systems. The resulting algorithms may be useful in difficult modeling and prediction problems including atmospheric/climate prediction, modeling of biological systems, or financial market analysis. The approaches developed here may lead to better predictive models for many of these complex systems. Furthermore, the program has strong ties to engineering education since undergraduates will have the opportunity to participate in specific experimental aspects of the research.
Engineering Heat Conduction Through Alloys and Interfaces
Professor Asegun Henry’s career proposal centered on the usage of two new methodologies his group developed for studying the phonon contributions to thermal conductivity and thermal interface conductance. The majority of the internal energy of objects in the universe is composed of heat, which manifests itself microscopically as atomic level kinetic energy. In solids, this kinetic energy manifests through the vibrations of atoms, back and forth around their respective average locations and the vibrations can be described through a summation of collective vibrational modes termed phonons. In non-electrically conductive solids, these phonons are responsible for heat conduction as they move vibrational energy from regions of higher temperature (e.g., faster atom speeds) to lower temperature (e.g., slower atom speeds). Over the last ~100 years, a theoretical framework has been developed, where the energy of these collective vibrations is treated by analogy, like it is a particle, and heat conduction is described in the same way as a gas of colliding particles – termed the phonon gas model (PGM).
The PGM was born out of the behaviors observed for perfectly pure crystalline materials, where all of the collective vibrations look like sine waves, and it does a remarkable job at explaining a wide range of experimental measurements for thermal conductivity and thermal interface conductance. However, when a material becomes disordered, i.e., either compositionally (e.g., an alloy) or structurally (e.g., high defect density or an amorphous material), the collective vibrations change from looking like sine waves to vibrations in seemingly randomized directions. As a result, the PGM breaks down and there are a myriad of interesting unanswered scientific questions associated with how heat transfer occurs in collective vibrations that do not look like sine waves.
Professor Henry’s proposal delves deeply into the underlying physics of the collective vibrations that occur in alloys and at interfaces and specifically seeks to illustrate that it may be possible to achieve properties previously unimaginable based on PGM based intuition. Furthermore, the proposal includes several outreach efforts including the development of a mobile app that will allow the general public to interface with the research being conducted. Specifically, the mobile app will allow users to listen to sonified data from the studies being conducted in addition to the sounds of the elements of the periodic table. Since every substance is composed of atoms and atoms are always moving, it is possible to simply treat the time dependent motions of atoms as time varying audio signals (i.e., by scaling the time axis of the vibrations down by ~ 1 billion times). The app will therefore also serve as a teaching tool so users can learn the periodic table of elements by hearing the sounds they make.
See Professor Henry’s website (http://www.ase.gatech.edu/sonification-overview/) for example sounds of semiconductors and a recent gizmodo article (http://gizmodo.com/this-scientist-is-turning-every-element-in-the-periodic-1759423993) about sonifying the periodic table.
Combustion research initiated by Dr. Wenting Sun has been chosen to receive a $360,000 grant from the Air Force Office of Scientific Research (AFOSR) through its Young Investigator Research Program (YIP). The prestigious award will fund "Explosive Ozonolysis Reactions for Combustion Control" - an investigation of new techniques to control combustion in hypersonic vehicles (vehicles traveling between five to eight times the speed of sound).
Sun's research team will focus on both the experimental and numerical investigation of explosive ozonolysis reactions - the spontaneous reactions between ozone and unsaturated hydrocarbons. The goal is to use his findings to control combustion for hypersonic vehicles.
Ultimately, Sun points out, his research will give engine designers a new arsenal of tools to produce hypersonically propelled aircraft - vehicles able to travel at speeds in excess of five times the speed of sound. "The Air Force is interested in this because it will allow them to reach any place on earth in two hours or less. There are lots of reasons why that is an important goal, worth the expense", Sun stated.