Hard Isotropic Solids from Soft Two-Dimensional Sheets

Unexpected material properties can be obtained by assembling known building blocks to yield unusual microstructures. This proposal aims to advance the knowledge regarding the synthesis, microstructures and properties of a new group of materials made of soft two-dimensional (2D) sheets. While these nanoscale building blocks are soft, flexible and highly anisotropic, very hard solids with isotropic material properties can be generated if the sheets are assembled and densified without generating long range stacking order. The proposal builds on our earlier original discoveries of such bulk “glassy” solids, and aims to achieve higher degree of densification through chemical modification of the 2D units to improve their compliance during densification, as well as mechanical materials processing techniques for more effective isotropic compression. We will then develop protocols for microstructural characterization of such glassy solids, which is difficult through conventional techniques. Knowledge gained about the microstructures will be applied to study the “collective” bulk properties of such solids that may deviate from their 2D structural units, such as their chemical reactivity, and resistance to mechanical and chemical attacks. If successful, new knowledge gained from the proposal can help to develop novel naval engineering materials that are light weight, hard to deform, electrically and thermally conductive, chemically resilient, and yet readily machinable.