Gas-Phase Combustion Synthesis of Metal and Ceramic Nanoparticles

Gas-phase combustion (flame) synthesis has been an essential industrial process for producing large quantities of powder materials such as carbon black, titanium dioxide, and silicon dioxide. Flames typically produce simple oxides, with carbon black being the noted exception because the oxides of carbon are gaseous and are easily separated from the particulate matter that is formed during fuel pyrolysis. The powders produced in flames are usually agglomerated, nanometer-sized particles (nanoparticles). This is an acceptable composition and morphology for many applications. However, recently there has been interest in flames for the synthesis of metal and non-oxide ceramic unagglomerated nanoparticles (2 to 100 nm) for advanced materials applications. For these applications nano-powders are consolidated into bulk materials under high temperature and pressure, yielding a solid part whose grains retain the nanometer size of the starting powder. The final nanostructured materials often possess unique mechanical, electrical or magnetic properties compared to their coarse-grained counterparts. The economics of powder processing can also be enhanced with nano-powders vis-a-vis low temperature consolidation and superplastic forming.