On the mechanism of nanoparticle formation in a flame doped by iron pentacarbonyl

Abstract

In this work we have investigated the mechanism of nanoparticle synthesis in a low pressure, premixed, laminar flat flame of CH4-O2, doped with iron pentacarbonyl using a combined quartz-crystal-microbalance-particle-mass-spectrometry apparatus. We have unambiguously demonstrated that the formation of nanoparticles in iron pentacarbonyl-doped flames occurs very early, in close proximity to the burner surface, prior to the flame front. This early rise of nanoparticle mass concentration is followed by a sharp drop in nanoparticle concentration at the high temperature flame front. This "prompt" nanoparticle generation is consistent with kinetic models describing iron cluster formation. The observation of this phenomenon in a quasi-one-dimensional premixed flat flame strengthens our previous findings and points out that the "prompt" nanoparticle formation is a general phenomenon, not limited to diffusion flames. It presents a challenge and a trigger for further development of the existing mechanisms for gas phase synthesis of iron oxide particles in flames.

Initial reaction steps during flame synthesis of iron-oxide nanoparticles

“…This model well reproduces the shape of the nanoparticle mass concentration on the FeIJCO) 5 concentration. 36 2D numerical simulations were used to calculate the mass transport of iron clusters Fe n with n = 2-8 (indicating all iron mass that does not appear as iron atoms or gaseous species) through the probing nozzle with burner-probe distances of 2, 4, 6, 8, and 10 mm, respectively (red line in Fig. 13, left).…”

Decomposition Reactions of Fe(CO)5, Fe(C5H5)2, and TTIP as Precursors for the Spray-Flame Synthesis of Nanoparticles in Partial Spray Evaporation at Low Temperatures

“…Qualitatively, for ethanol and o -xylene solutions, similar decomposition products of Fe­(CO) 5 appear but in the o -xylene spray, the signal of Fe­(CO) 3 is detected. In the gas-phase reaction mechanism, a stepwise loss of the CO ligands from the iron is postulated . The fact that Fe­(CO) 3 can be observed in the spray of the Fe­(CO) 5 / o -xylene solution but not in that of Fe­(CO) 5 /ethanol is another indication that the reactions proceed slower in the presence of o -xylene than ethanol.…”

“…In the gas-phase reaction mechanism, a stepwise loss of the CO ligands from the iron is postulated. 40 The fact that Fe(CO) 3 can be observed in the spray of the Fe(CO) 5 /o-xylene solution but not in that of Fe(CO) 5 /ethanol is another indication that the reactions proceed slower in the presence of o-xylene than ethanol. The signals of all thermal decomposition products show a sharp increase in signal strength near 100 °C below the temperature at which all Fe(CO) 5 is consumed and they persist to the highest temperature that could be reached in the tubular reactor.…”

“…Our investigation focuses on the investigation of the chemical reactions occurring during spray formation using three popular precursors: ferrocene, iron pentacarbonyl, − and titanium tetraisopropoxide ,− using microprobe sampling with time-of-flight (TOF) mass spectrometry . These precursors have been studied before in vapor-phase systems, e.g., iron pentacarbonyl, tetraisopropoxide, and ferrocene, , and gas-phase reaction mechanisms of the precursors exist. Identification of the initial Fe- or Ti-containing intermediates in the gas phase is particularly needed for the creation and verification of chemical mechanisms that can describe reactions of the precursors in the presence of different solvents and are crucially needed to model the spray synthesis process.…”

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

“…The latest progress in the evaluation of the flame structure in the presence of iron compounds was contributed by spatially resolved detection of FeO profiles via intracavity laser absorption spectroscopy (ICLAS; see section 3.2) 12,14 and MBMS observations by Karakaya et al, 41 reporting the impact of iron on radical flame species and temperature, stepwise decomposition of iron pentacarbonyl, formation of gas-phase hydrates of Fe(OH) 2 , Fe(OH) 3 , and Fe 2 O 3 , and inception of solid iron oxide particle formation, manifested by larger clusters with five iron atoms. The particle mass spectrometry− quartz crystal microbalance (PMS−QCM; see section 3.3.1) measurements of the solid particle phase performed by Poliak et al 39 were reproduced and extended by Kluge et al 12 using PMS−QCM in combination with laser spectroscopy, supported by a skeletal version of the reaction scheme proposed by Feroughi et al 50 Very recently, Nanjaiah et al 14 reported measurements and numerical simulations of the temperature and FeO in the Fe(CO) 5 -doped low-pressure flames for a wide range of equivalence ratios. They used a skeletal scheme extended for possible reduction of the Fe 2 O 3 particle monomer under fuel-rich conditions and investigated the impact of iron cluster formation steps on the flame characteristics.…”