Insights into the Mechanism of Combustion Synthesis of Iron Oxide Nanoparticles Gained by Laser Diagnostics, Mass Spectrometry, and Numerical Simulations: A Mini-Review

Abstract

To fully master a scaled-up combustion synthesis of nanoparticles toward a wide library of materials with tailored functionalities, a detailed understanding of the underlying kinetic mechanism is required. In this respect, flame synthesis of iron oxide nanoparticles is a model case, being one of the better understood systems and guiding the way how other material synthesis systems could be advanced. In this mini-review, we highlight, on the example of an iron oxide system, an approach combining laser spectroscopy and mass spectrometry with detailed simulations. The experiments deliver information on time–temperature history and concentration field data for gas-phase species and condensable matter under well-defined conditions. The simulations, which can be considered as in silico experiments, combining detailed kinetic modeling with computational fluid dynamics, serve both for mechanism validation via comparison to experimental observables as well as for shedding light on quantities inaccessible by experiments. This approach shed light on precursor decomposition, initial stages of iron oxide particle formation, and precursor role in flame inhibition and provided insights into the effect of temperature–residence time history on nanoparticle formation, properties, and flame structure.

Combustion, Chemistry, and Carbon Neutrality

“…The color bars map the temperature history of particle formation and growth according to the flame structure . Reproduced with permission from ref . Copyright 2020 American Chemical Society.…”

“…For high precursor concentrations, Figure exhibits a second nucleation zone in the recombination region of the flame, corresponding to iron oxide nanoparticle formation; these are exposed to fresh precursor and gas-phase species and experience further growth . Influences on the process by buoyancy were also seen by comparing the growth process in upward and downward burning flames. , …”

“…669 Fe(CO) 5 decomposes at moderate temperatures in the flame preheat zone, giving rise to iron atoms, clusters, and particles already before the hot reaction zone of the flame, where such structures disappear again, followed by final synthesis product formation in the recombination zone. 669 The process has been followed with an extensive combination of experimental techniques, including LIF, ICLAS, MBMS, and particle mass spectrometry coupled with a quartz microbalance; these were applied to measure temperature, to detect Fe atom, FeO, and larger intermediates, and to characterize incipient Fe 5 O x H y clusters and nanoparticles. 669 Challenges were encountered regarding the in situ spectroscopic detection of species such as FeOH, Fe(OH) 2 , Fe(OH) 3 , Fe 2 CO, FeCO, Fe(CO) 2 , and Fe(CO) 3 ; such measurements could, however, become possible using IR laser spectroscopy.…”

“…669 For high precursor concentrations, Figure 42 exhibits a second nucleation zone in the recombination region of the flame, corresponding to iron oxide nanoparticle formation; these are exposed to fresh precursor and gas-phase species and experience further growth. 669 Influences on the process by buoyancy were also seen by comparing the growth process in upward and downward burning flames. 669,699 A gas-phase reaction mechanism was developed with 31 species and 134 reactions that describes the initial decomposition of Fe(CO) 5 , the formation and decomposition of Fe clusters up to Fe 8 , the oxidation of Fe atoms, the interaction of Fe−O−H intermediates with flame species, the formation of the Fe 2 O 3 particle monomer, and the reduction of this species back to Fe and FeO.…”

Virtual Special Issue of Recent Advances in Gas-Phase Synthesis of Functional Materials for Energy

“…Ouimet et al 4 review vapor-based synthesis and deposition for proton exchange membrane (PEM)-based devices. The review of Rahinov et al 5 provides comprehensive insight in the mechanism of combustion synthesis of iron oxide nanoparticles based on combined laser spectroscopy, mass spectrometry, and detailed simulation.…”