Formation and in situ sizing of gamma-Fe2O3 nanoparticles in a microwave flow reactor.

Nanocrystalline gamma-Fe2O3 particles were produced in a microwave flow reactor. The reaction of iron pentacarbonyl [Fe(CO)5] with the plasma gases Ar/O2 to form nanosized particles was followed by in situ particle mass spectrometry. The particle mass spectrometer combines a nonintrusive sampling technique with a calibration-free mass determination. The influence of process parameters like microwave power, precursor concentration, and pressure on the particle size was studied. The results reveal a mean particle diameter in the range of 4-5 nm with a slight dependence on the process parameter. The geometric standard deviation of the measured size distribution was always between 1.1 and 1.2.