Salt-Assisted Solution Combustion Synthesis

In the process of traditional solution combustion synthesis, the agglomeration and sintering of the resultant oxide nanoparticles widely exists. To inhibit or reduce the phenomena, a novel and facile salt-assisted solution combustion synthesis process was developed, which is to dissolve some soluble inert inorganic salt into the redox mixture solution. Based on the approach, many interesting materials such as mesoporous ceria-zirconia solid solutions, highly dispersed nanoparticles of perovskite NdCoO3 and spinel CoFe2O4, and LaMnO3 and Re2(Zr1-xSnx)2O7 nanocubes, etc. have been fabricated. The chapter reviews the latest developments in microstructure-controlled synthesis of the mixed metal oxides via a salt-assisted solution combustion synthesis process. In the review, the effects of fuel-to-oxidant ratios, type and amount of added salt on the characteristics of the resultants were investigated by powder X-ray diffractometry (XRD), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) surface area analysis. The results show that the salt introdution inhibits the formation of hard agglomerates during the combustion synthesis, results in drastic increase in specific surface areas of the resultants and also has apparent effect on the particle morphology. Finally, a mechanism scheme was proposed to illustrate the possible formation processes of highly dispersed nanoparticles and discuss the role of the salt additives. In view of the large number of salt additives available, the SSCS approach would be expected to offer abundant opportunities in materials research and provide an effective strategy to tailor the microstructures and properties of the materials for the conventional combustion synthesis process.