Bio
Hi, my name is Luis Estevez and I am currently a 5th year PhD. candidate in Materials Science and Engineering. I’m a non-traditional student who decided to pursue an engineering degree after spending several years managing my family’s restaurant. I attended the University of Maine at Orono and obtained a B.S. in Mechanical Engineering, graduating Magna Cum Laude. For my senior design project, I was an integral part of a four person team that designed, built and tested a long distance dog sled, made to be used in the Alaskan Iditarod.
While pursuing my B.S. at Maine, a summer internship spent at Los Alamos National Laboratory proved pivotal to me. I spent the summer of my junior year participating in the Los Alamos Dynamics Summer Session (LADSS), where I was put into a three member multidisciplinary team and tasked with using non-linear acoustics to detect fatigue cracks in aluminum sheets for structural health monitoring applications. I was completely immersed in advanced research for the first time in my life and found myself immediately smitten. When I asked the research staff at Los Alamos how I could do this for a living, the staff told me I needed a PhD. Thus, I soon started the process of investigating and applying to graduate programs, finally choosing to realize my potential at Cornell University. The summer before starting at Cornell, I married my long time girlfriend, Erin. This was the best part of a busy summer that saw me graduate, proposes, get married and move into Ithaca within a period of three months!
At Cornell, I joined Emmanuel Giannelis’ research group and began working on various organic/inorganic nano-hybrid materials systems, particularly those with Energy applications. Currently, I am exploring the use of ice templating to synthesize porous carbon materials and looking into their potential applications as battery electrodes. As I near the end of my PhD. candidacy, I’m looking forward to continuing my scientific career in the industrial sector, where I hope to synthesize novel materials to solve vexing energy problems. When not engulfed in my research, I find myself working on my newly purchased home and using it for BBQ get-togethers with family and friends. I also enjoys snowboarding, playing guitar and I’ve recently gotten into brewing beer.
Research
There is considerable interest in the development of alternatives to conventional fossil fuel based energy generation. Many promising options, such as solar, wind or tidal power sources, are not available on demand. We need to be able to capture the energy when it is available and save it for later when it is needed. Thus, energy storage is necessarily an important part of any renewable energy solution. Thus, energy storage becomes an important part of any renewable energy solution.
In the Giannelis research group, we typically synthesize inorganic/organic hybrid systems, usually with direct applications such as energy storage systems. These hybrid materials are usually composed of an organic polymer matrix with inorganic nanoparticles that can enhance the polymer’s properties, or imbue the nanocomposite with entirely new properties and functionalities. By synthesizing these novel materials with tailor-made properties, we can target and replace certain convention materials within energy storage devices. Two types of energy storage devices that I have worked on are hydrogen based PEM fuel cells and Li-sulfur batteries.
My initial work focused on PEM fuel cells. In these fuels cells, there is a classic materials science problem where we need a particular material (called the catalyst layer) that can accomplish many different tasks at once. The catalyst layer needs to be able to conduct both ions and electricity. It needs to be able to accommodate the catalyst (usually platinum nanoparticles) and also be porous in order for gases to flow through it. To synthesize a material with all of these properties, we combined our nanocomposite techniques with ice templating. In the method of ice templating, (see scheme below) we take an aqueous suspension of Nafion, graphene oxide (GO) sheets and a platinum salt and then freeze the whole mixture. As the water crystallizes, it expels the non-water constituents around the ice. Next, simple freeze drying removes the ice, leaving behind a porous polymer composite scaffold. A bit more chemistry turns the GO sheets into graphene sheets and the platinum salt into platinum nanoparticles. The resultant material is an interconnected porous scaffold with electrical conductivity (graphene sheets), ionic conductivity (Nafion) and catalytic platinum nanoparticles.
Lately we have shifted gears a bit, and in our current work, we are applying ice templating techniques to carbon systems to achieve high surface area, porous carbon materials. These have potential for use as battery electrodes. The porous carbon scaffolds synthesized (shown below) have hierarchical pore sizes including both tunable mesopores (5-20 nm) and macropores (1-2 microns). We are currently working on using these carbon scaffolds to synthesize carbon-sulfur composites that then can be employed as a cathode in a lithium-sulfur battery cell. This new type of battery has the potential to have high specific energy densities compared to conventional Li-ion systems, and can lead to a whole new generation of Li based batteries to keep up with tomorrow’s electronic devices and energy storage needs.
