Understanding Heterogeneity of Energetic Materials
The materials used in this work will be based on sol-gel chemistry. Sol-gels consist of an interconnected framework/backbone with a 3-dimensional structure. The backbone can be made from a wide variety of materials such as carbon, silica, metals and even explosives. Because of the wide variety of materials available, the z number of the material can be finely tuned. In addition, the overall density can be controlled by the method of drying. Density ranges of sol-gel materials can be from ~5 g/cc (bulk density of the back bone) to 0.0001 g/cc for supercritical drying. The density and effective z can be further controlled by backfilling the void space. In addition, controlled voids can also be constructed through an inverse opal synthetic method. The materials will be used for X-ray CT imaging to determine limits of resolution. X-ray images can be directly compared to SEM images for reconstruction studies.
The second aspect of this work will be to investigate how heterogeneity influences sensitivity, thermodynamic and kinetic parameters. It has been proposed that by engineering the micro/nano structure of explosives, energy density and energy on target may be increased by a factor of three or more. The energy release rate and the reaction propagation rate of explosives are strongly dependent on particle size distribution, surface area of the constituents, and void volume and shapes. The variations are important to impact initiation as recognized by Apin and Bobolev in the late 1940s. However, a systematic study on the nano-microstructure of explosives has not been performed. In this work we seek to determine how both controlled and random heterogeneity influences properties of energetic materials.