Investigation of the combustion of iron pentacarbonyl and the formation of key intermediates in iron oxide synthesis flames

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

“…49 When fragmentation cannot be avoided, the measurements have to be corrected for the ion signal, resulting from ionization-induced fragmentation and/or ion species forming during the sampling process. 41 Sampling and ionization efficiency have to be quantified using calibration approaches, 41,70 to convert the measured ion signal to the mole fraction of the sampled species. MBMS in nanoparticle flame synthesis reactors is associated with additional challenges.…”

“…41 The clogging of the sampling orifice is commonly diminished by limiting the experiments to relatively low precursor loads. 41,142 Protection of the probe orifice from clogging by particles using an automatic cleaning system was demonstrated by Gonchikzhapov and Kasper, 143 who used TOF−MS with microprobe sampling to investigate the chemical interaction between the solvent and Fe(CO) 5 , Fe(C 5 H 5 ) 2 , and Ti(i-OC 3 H 7 ) 4 precursors during partial evaporation of the spray preceding the ignition. Gerasimov et al 49,142 studied an atmospheric pressure H 2 / O 2 /N 2 flame doped with Fe(CO) 5 using EI−MBMS with a quadrupole mass spectrometer.…”

“…This absence was attributed by the authors either to overprediction of the expected FeO concentration by the model or to low detection sensitivity of the mass spectrometer to FeO. 49 An alternative approach, circumventing the MBMS sensitivity limitations associated with the detection of ironcontaining intermediates by the combination of EI− and PI− MBMS with MBMS of ions naturally occurring in the flame, was recently demonstrated by Karakaya et al 41 (see Figure 11). The chemi-ion formation in H 2 /O 2 , flames, doped with Fe(CO) 5 , was enhanced by seeding these flames with ethene, which yielded ions via charge or proton transfer reactions of neutral species with H 3 O + formed by the CH + O → CHO + + e − ↔ H O 2 H 3 O + + CO reaction sequence.…”

“…A relatively limited number of reactions leading to the formation of cations allowed for the use of them as descriptors of their neutral counterparts. Within this approach, 41 the authors deployed a novel ion sampling system coupled to the same TOF spectrometer used with the EI−MBMS setup. This ion sampling system (see Figure 11c) reached higher sample transfer efficiency and improved sensitivity, by increasing the orifice diameter of the sampling nozzle, followed directly (without extracting the core of the molecular beam by a skimmer) by an ion funnel coupled to sequentially arranged octupole and quadrupole ion guides.…”

“…The same is true for FeO(OH) (excluded from the reduced mechanism by Wlokas et al 26 and suggested by ref 41 to link iron hydroxides to Fe 2 O 3 ); it could not be observed in iron-doped flames in either of insofar available MBMS studies. 41,49,142 The reaction pathways leading to the formation of larger Fe 5 O x H y -like species (e.g., m/z 397; see Figure 11d) could not be traced 41 as a result of the complexity of the mass spectra stemming from overlapping isotopic patterns and the formation of water clusters. Nevertheless, the similarity between the Fe 5 O x H y cluster profiles and profiles of iron oxide nanomaterial, previously reported in PMS−QCM studies, 12,13 suggest these clusters for the role of incipient species in solid-phase iron oxide product formation.…”