Energy absorbing media based upon nanocrystals of complex shape and topology

Paul Alivisatos Professor of Chemistry and Materials Science University of California, Berkeley There are numerous situations in which a light weight composite with high energy absorbing capabilities can be of use in the Air Force mission, for protection against impact of projectiles or laser beams. Advances in nanoscience have created a new opportunity to design such composites, as it is now possible to blend inorganic nanocrystals of controlled geometry and topology inside plastics. We propose to investigate new types of colloidal inorganic nanocrystals of complex shape and topology, which have the potential to act as energy absorbers during a collision , or in the shock wave generated by an intense laser beam. Nanocrystals respond to mechanical deformations in ways that are completely distin~ from bulk materials, and in many cases they exhibit more ideal behavior, with the ability to deform to a higher degree than the bulk material before fracture occurs. Recently we developed new methods to prepare hollow nanocrystals, nested hollow nanocrystals, branched nanocrystals, and hyper-branched nanocrystals. -I t is of considerable interest to try to create new composites that contain these novel colloidal nanocrystals embedded in a soft matrix. This proposal brings together three components for such a program: synthesis of new colloidal nanocrystals with potential energy absorbing properties; tests of mechanical deformation of isolated nanocrystals using a range of experimental techniques (indentation, scanning probe microscopy, hydrostatic pressure, and laser-induced shock waves); creation of composites of the nanocrystals in plastics, suitable for mechanical testing , for instance at Air Force laboratories.