A Counterflow Diffusion Flame (CDF) reactor was used to produce iron oxide nanoparticles. The experimental work was performed to study synthesis conditions and characterize the iron oxide nanoparticles. The parameters studied are those that control the flame structure, namely, gas flow rates and vacuum; other parameters include the precursor volume flow rate, and the relative location and temperature of the collecting probe inside the flame. Hexagonal nanoparticles were the most commonly observed shape. Hexagonal-shaped nanoparticles are mainly formed under stoichiometric conditions and with a high temperature profile in the flame. Cubic nanoparticles were also observed. The main parameter for the formation of cubic-shaped nanoparticles was found to be the equivalence ratio. A minimum value of less than one percentage of cubic nanoparticles was observed at equivalence ratios ranging between 0.7488 and 0.9283. The main effect on particle size was observed to be from the hydrogen flow rate, which was found that the higher the hydrogen flow rate is, the smaller the average nanoparticle size. A secondary minor effect was observed from variations of vacuum flow rate. This effect could be associated with changes in the total mass or volumetric flow rate balance. Adjusting N₂ in H₂ stream allowed the synthesis of samples with approximately 95% hexagonal nanoparticles without agglomerates --Abstract, page iii
