Aerosol routes to synthesis of nanoparticles and its application to energetic materials.

摘要

Mixtures of fuel and oxidizers with particle sizes in the nanometer range have been widely used for energy intensive applications like propellants and explosives. Nano-Al is invariably used as fuel, while a host of metal oxide nanoparticles are used as oxidizers, such as: Fe2O 3, CuO, MoO3, depending on the thermodynamics and kinetics of the reaction. This work describes synthetic procedures for oxidizer nanoparticles via aerosol routes with a fine control on the morphology and oxidative characteristics of the nanoparticles. An aero-sol-gel method has been used for the synthesis of nanoporous Iron oxide nanoparticles with a controlled surface area ranging from 3--200 m2/g. A new super-reactive formulation of Al/KMnO 4 has been developed which is a few orders of magnitude more reactive than the traditional formulations of Al/Fe2O3, Al/MoO 3 and Al/CuO. The nanoenergetic materials were subjected to confined combustion in a pressure vessel and the reactivity was measured in terms of pressurization rate (psi/mus). Difference in characteristic temperature of two components of a composite nanoparticle has been employed to synthesize particles with a core-shell nanostructure. By manipulating, the interfacial area between the fuel and oxidizer particles we have developed methods both to enhance as well as moderate the reactivity of energetic materials in a large dynamic range.; The second part of this work describes a simple aerosol model for synthesis of nanoparticles by evaporation/condensation method. A new approach to the solution of the General Dynamic Equation (GDE) based on a nodal method has been used. The model solution described is suitable for problems involving gas to particle conversion due to homogeneous nucleation, coagulation, and surface growth of particles via evaporation/condensation of monomers. The important features of the model is that it is simple to comprehend, the software which we call Nodal GDE Solver (NGDE) is relatively compact, and the code is well documented internally, so that users may apply it to their specific needs or make modifications as required. The solution presented here describes the solution of the problem and our approach for both constant and size-dependent surface tension.