Prof. Paul V. Braun
University of Illinois at Urbana-Champaign
Host: Dr. Tan Wui Siew, Polymeric Department, IMRE
Electrochemical formation strategies offer unique capabilities for forming materials as diverse as lithium-ion battery electrodes and microphotonic elements. Through our understandings of electrochemistry in confined environments, considerable advances in both energy storage and photonics have been made. For example, in the direct electrodeposition at modest temperatures of high performance tin-based Li-ion anodes and LiCoO2, LiMn2O4, and Al-doped LiCoO2-based Li-ion cathodes. The electrolytically active materials were formed either as solid films, or where significant volume changes upon cycling are present, via a templating process, as a 3D mesostructured film. The capacities are near-theoretical, and in the case of the electroplated oxides, the crystallinities and electrochemical capacities of the oxides are comparable to powders synthesized at much higher temperatures (700 ~ 1000°C). The electrodeposition method significantly broadens the scope of battery form factors and functionalities, enabling a variety of highly desirable battery properties including microbatteries, and high energy, high power, and flexible designs.
In the area of photonics, via electrochemical etching of silicon, followed by materials conversion, 3D gradient refractive index micro-optics including flat lenses, Bragg mirrors, polarisation sensitive optical splitters and structures with nearly arbitrary refractive index distributions were formed with a particular focus on micro-optics important for solar energy harvesting. The conversion from silicon to silica and titania enabled the optics to operate in the visible with minimal loss, something particularly important for solar energy harvesting applications. In this seminar, the speaker will present a developed detailed model which enabled tight control over optical properties based only on the electrochemical etch conditions.
ABOUT THE SPEAKER
Prof. Paul V. Braun received his B.S. degree with distinction from Cornell University, and his PhD in Materials Science and Engineering from Illinois. Following a postdoctoral appointment at Bell Labs, Lucent Technologies, he joined the faculty at Illinois. Prof. Braun’s research focuses on the synthesis and properties of 3D architectures with a focus on materials with unique optical, electrochemical, thermal, and mechanical properties. He is the recipient of the Young Alumnus Award (2011), the Friedrich Wilhelm Bessel Research Award (2010), the Stanley H. Pierce Faculty Award (2010), Beckman Young Investigator Award (2001), a 3M Nontenured Faculty Award, the 2002 Robert Lansing Hardy Award from TMS, the Xerox Award for Faculty Research (2004, 2009), and multiple teaching awards. In 2006, he was named a University Scholar by the University of Illinois, and in 2011 was named the Ivan Racheff Professor of Materials Science and Engineering.
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