Date: Friday, Apr 30th
Presenter: Robert O. Ritchie, Chair, Department of Materials Science and Engineering, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory
The structure of materials invariably defines their mechanical behavior. However, in most materials, specific mechanical properties are controlled by structure at widely differing length scales. Nowhere is this more apparent than with natural materials. Bone, dentin and nacre, for example, are sophisticated composites whose unique combination of mechanical properties derives from an architectural design that spans nanoscale to near-macroscopic dimensions; few engineering materials have such hierarchy of structure and properties. Unlike engineering composites where properties are invariably governed by the ?rule of mixtures?, the mechanical properties of many natural composite materials are generally far greater than their constituent phases. However, actually making such materials synthetically has proved to be extremely difficult, particularly in bulk form. Here we describe an approach, involving processing by ice-templating, to developing bulk ceramic-polymer nacre/bone-like structural materials with unprecedented strength/toughness properties. Indeed, we believe that these materials represent the highest toughness ceramics reported to date.