This study focuses on the effects of combustion conditions, various additives, and pre-processing steps on the formation of fully dense, graded, and random porous structures derived from nanopowdered reactants. The investigation covers the effects of particle size, mixing procedure, and the topology of the resulting particles in the reacting mixture on reaction kinetics and the microstructure of products. Several exothermic reactions have been selected for these studies including aluminum/titania, aluminum/niobia, aluminum/nickel, and aluminum/silicon/nitrogen. Both thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) and nonisothermal techniques are used to evaluate reaction kinetics of these reactions. In addition, a new combustion diagnostic method using a gated, intensified CCD camera and a laser-induced breakdown spectroscopy (LIBS) instrument is used to analyze dynamic temperature profiles. Simultaneous combustion synthesis and uniaxial densification in systems consisting of reactive nanopowders, such as aluminum, silicon, nickel oxide, or niobia, is investigated. Comprehensive studies of the effect of protective coatings and other particle surface treatments on their reactivity, combustion wave characteristics, and the morphology of resulting products are performed. Also done are fundamental studies of the formation of nanostructural materials with graded composition and/or porosity. The dynamics of combustion processes in both volume combustion (VC) and self-propagating high-temperature synthesis (SHS) regimes in the presence of external forces and/or internal gasification of additives are modeled mathematically.
Broader impact Experimental research studies, by development of new and faster response techniques, should lead to better understanding of reaction kinetics in condensed phase systems. In addition, the research should enhance the knowledge of the formation of structural materials under strongly non-isothermal conditions. Findings from these research studies should be beneficial to materials science, combustion, and reaction engineering communities. This project provides research opportunities for an existing REU Sites program that serves tribal colleges. It also underlies cooperative efforts with Germany and Poland.
