Self-propagating solid-state precursor combustion synthesis of advanced materials: Methods, characterization and modeling

Previous studies have shown that simple thermodynamic calculations of reaction exothermicities are usually enough to find a self-propagating solid-state metathesis (SSM) route to a desired product. The present work, which generally involves reactions with high activation energy barriers, shows that consideration of other factors such as transport phenomena and chemical kinetics is important in designing an SSM route to a desired product. Such considerations lead to new ideas for precursor selection, rapid synthetic approaches to important non-oxide ceramics and the application of modeling methods to SSM reactions.; In this dissertation, it is shown that the SSM approach provides an effective route to important non-oxide ceramics including boron nitride, boron phosphides, boron arsenide, aluminum nitride, transition metal borides, boride solid solutions and boride-nitride composites. These products are characterized by XRD (with Rietveld analysis), SEM, EDS, ICP-AA, IR, XPS, density measurements and chemical analysis. The most significant example is the rapid formation of crystalline boron nitride (within seconds), which otherwise must be synthesized with long heating times at 1500-2100 {dollar}spcirc{dollar}C. The new ideas which led to the success of these new synthetic methods are presented and discussed in detail.; The investigation of SSM syntheses requiring high activation energy reactions has facilitated the introduction and development of various modeling methods in the present study. These methods include thermodynamic modeling (e.g., the calculation of adiabatic temperature and optimization of reaction conditions based on such calculations), kinetic modeling (e.g., the analysis of activation energy profiles based on possible reaction pathways and correlating this to the observed reaction modes) and thermo-kinetic modeling (the numerical investigation of combustion synthesis with either one of the two most important phenomena involved: phase changes and precursor decomposition). This modeling provides insight into combustion syntheses as well as a theoretical base for the development of new synthetic methods. Through the use of modeling, it is possible to make predictions about the reaction mode and product yield based on the properties of the materials involved. With these results as starting points, a concrete, semi-quantitative description of SSM reactions should be possible in the near future.