UNDERSTANDING AND TAILORING THE REACTIVE CHARACTERISTICS OF NANOENERGETIC COMPOSITES VIA STRUCTURAL AND CHEMICAL MODIFICATIONS

Abstract

Nanoenergetic composites are nanostructured fuel and oxidizer mixtures that store a large amount of chemical energy and release it, typically in the form of heat, upon ignition. They are promising candidates for energy intensive applications such as propellants and pyrotechnics, due to their high energy density. The overall reaction kinetics of the heterogenous nanoenergetic system is controlled by mass transfer. The use of nanoparticles is to reduce diffusion length and thus increase energy release rate. The objective of the proposed research is to understand how intrinsic properties of fuel and oxidizer affect the reaction of nanoenergetic composites, and to develop novel, multifunctional nanoenergetic materials with tunable ignition threshold and energy release rate. Experiments were conducted utilizing primarily a time resolved Temperature-Jump time-of-flight mass spectrometer (T-Jump TOFMS) to analyze gas phase reaction intermediatespecies and products at a high heating rate (~105 K/s), along with a combustion cell for reactivity evaluation. New fuels including hydrogenated amorphous silicon, and oxidizers including oxygen deficient Co3O4-x and ferroelectric Bi2WO6 were investigated. The role of surface chemistry in the energetic characteristics of silicon nanoparticles was investigated, leading to the uncovering of a new reaction mechanism. Modulating the initiation temperature of aluminothermic reaction via defect engineered metal oxide was demonstrated. A study of piezoelectric oxidizers reveals the superior reactivity of a complex metal oxide. Moreover, tuning the energy release rate of I2O5 based biocidal nanoenergetic composites via a ternary system was studied. These results indicate that by modifying the chemistry or structure of fuels and oxidizers, the combustion characteristics of nanoenergetic composites can be tailored.