Synthesis and characterization of the mechanical behavior of mechanically strong porous nanostructured materials.

摘要

Aerogels are three-dimensional assemblies of nano-particles that are typically synthesized through the sol-gel process and then dried by replacing the pore filling solvent with air. This work presents a robust method to manufacture both organic and inorganic aerogel so that mass production can be done more easily and at a substantially low cost of production. The inherent problems associated with typical aerogel materials such as fragility, hydrophilicity as well as requirement to use supercritical drier are addressed by nano-casting a conformal polymer layer on inorganic templated aerogels, while the microstructure of organic aerogels are refined so that they can be dried in ambient condition. Thus large pieces of aerogels have been synthesized and characterized to ascertain the mechanical properties so that design of components and structures can be done with ease. The first part of this work deals with inorganic templated silica aerogels whose morphology has been optimized to overcome fragility and allow for large samples to be produced. As such a microstructure akin to the naturally occurring honeycomb structure is produced resulting in a material, whose energy absorption is about 187 j/g, indicating that they are far stronger than most manmade materials in production. The second part of this work present a careful synthesis of organic polyurea aerogels whole morphology is varied from nano fibrous at the low density end to nano particulate at the high density end. By so doing we synthesized a nanostructured material which can be dried in ambient conditions at a much lower bulk density (0.2 g/ cm3) that earlier reported. In addition the materials have very high dimensional stability such that they retain their shape and size from the mold even after ambient drying. With that, this work seeks to resolve the inherent problems of aerogel materials, both organic and inorganic that makes them hard to economically mass produce.