Fabrication of Metal Oxide Nanoparticles by Highly Exothermic Reactions



The development of two methods using highly exothermic oxidation reactions to synthesize nanostructured oxide particles is described. The first method uses solution combustion to produce a high temperature front that moves through the sample and produces the nanoparticles. For example, Bi2O3 nanoparticles are produced using a solution of molten metal nitrates and glycine. The glycine (fuel) is completely combusted during the thermal decomposition of the (oxidizer) nitrates and generates a temperature front that propagates through the sample. The second method produces nanoparticles by a self-propagating high-temperature reaction from stoichiometric powder mixtures of metal oxides (or carbonates) and carbon. The exothermic oxidation of the carbon generates a propagating high-temperature front at a velocity in the range of 0.1–2.5 mm/s that converts the reactants to products. In both cases, the synthesis was completed within a few seconds. In both methods, a higher maximum combustion temperature and larger oxide particle size were obtained following an increase in the fuel concentration. The main advantages of these synthesis methods technologies are simplicity, short reaction time, low reactant costs, and no external energy consumption. The methods can be used to synthesize nanoparticles for various applications including nanoenergetic materials, catalysts and electronic components.