Abstract
The future of many “green” technologies depends on the availability of scarce elements. For instance, each modern wind turbine requires about a ton of rare-earth permanent magnets, made principally of Dy, Sm and Nd. Similarly, solid state lighting requires phosphors containing elements such as Eu and Tb. Current thermoelectrics are based on bismuth telluride and the highest-efficiency, mass-produced solar cells are made of CdTe. Not only are many of these elements extremely expensive but they are scarce in the sense that their natural abundances in the earth’s crust are amongst the lowest of all solid elements.
At Harvard the speaker and his research group have begun a program to explore new approaches to materials sustainability, trying to address the fundamental issues relating to the availability of critical elements, how they may be extracted, all the way to materials recycling. There are tremendous challenges in extracting the rare earth elements from native ores, and separation of the different individual elements is even more difficult to achieve, since they are chemically so similar. In addition, the methods currently used involve toxic chemicals with their own negative impact on the environment. As the speaker will describe, they have unexpectedly found that biogenic approaches based on the selective biosorption/desorption to various bacteria can be particularly effective in separating the rare-earth elements. They believe that this provides radically new opportunities of using biological agents rather than environmentally harsh chemicals to process elements.
In this talk, the speaker will describe why it is so important that they address the availability of scarce elements, what the challenges really are and how nature may provide ideas on biogenic processes that can offer a new scientific paradigm for environmentally-benign materials processing.
About the speaker
Prof David Clarke received his PhD in Physics from the University of Cambridge in 1974. He had been faculty at the University of California at Berkeley, the Massachusetts Institute of Technology and the University of California at Santa Barbara. He joined Harvard University in 2009, and is currently Extended Tarr Family Professor of Materials in the School of Engineering and Applied Sciences. He is also Visiting Professor of Mechanical and Aerospace Engineering and of Physics at HKUST.
Prof Clarke’s research interests in materials range from the fundamentals to the applied, from ceramics to metals to semiconductors and polymers. He has published over 450 papers in areas of materials ranging from thermal barrier coatings, to dielectric elastomers to fundamentals of oxidation to microelectronics reliability and the electrical and optical properties of ZnO and GaN.
Prof Clarke received numerous awards including the Alexander von Humboldt Foundation Senior Scientist Award, the Japanese NIMS Award for Recent Breakthroughs in Materials Science for Energy and Environment, and the Edward C. Henry Award, etc. He is a Member of the US National Academy of Engineering, and a Fellow of the American Physical Society and the American Ceramic Society.
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