Flame Spray Synthesis Research Articles

Production of Carbon Black in Turbulent Spray Flames of Coal Tar Distillates

Conventional carbon black production occurs by pyrolysis after heavy aromatic feedstock is injected into the post-combustor region of furnace black reactors. The current work examines the conversion of the coal tar distillate in turbulent spray flames to demonstrate a more compact reactor configuration. Coal tar distillates diluted in toluene is atomized and burned in a standardized flame spray synthesis configuration, known as SpraySyn. Flame conditions are characterized by thermocouple, soot pyrometry and image analysis and product particle properties are examined by TEM and Raman spectroscopy. The measured flame temperature corresponds to the range of temperatures used in the furnace black process, but the current synthesis includes oxidizing conditions and faster residence times. The resulting carbon black particles are aggregates with primary particle sizes on the small end of the carbon black size spectrum, according to analysis of TEM images. Carbon black, formed under a range of flame temperatures, show Raman spectra with features resembling typical carbon black materials. Conversion of coal tar distillate to carbon black by direct flame synthesis may be a scalable method to produce high-surface area grades without a conventional pyrolysis reactor stage.

Enhanced heterogeneous activation of peroxymonosulfate by Ruddlesden-Popper-type La2CoO4+δ nanoparticles for bisphenol A degradation

The scalable synthesis of stable catalysts for environmental remediation applications remains challenging. Nonetheless, metal leaching is a serious environmental issue hindering the practical application of transition-metal based catalysts including Co-based catalysts. Herein, for the first time, we describe a facile one-step and scalable spray-flame synthesis of high surface area La2CoO4+δ nanoparticles containing excess oxygen interstitials (+δ) and use them as a stable and efficient catalyst for activating peroxymonosulfate (PMS) towards the degradation of bisphenol A. Importantly, the La2CoO4+δ catalyst exhibits higher catalytic degradation of bisphenol A (95% in 20 min) and stability than LaCoO3–x nanoparticles (60%) in the peroxymonosulfate activation system. The high content of Co2+ in the structure showed a strong impact on the catalytic performance of the La2CoO4+δ + PMS system. Despite its high specific surface area, our results showed a very low amount of leached cobalt (less than 0.04 mg/L in 30 min), distinguishing it as a material with high chemical stability. According to the radical quenching experiments and the electron paramagnetic resonance technology, SO4–, OH, and 1O2 were generated and SO4– played a dominant role in bisphenol A degradation. Moreover, the La2CoO4+δ + PMS system maintained conspicuous catalytic performance for the degradation of other organic pollutants including methyl orange, rhodamine B, and methylene blue. Overall, our results showed that we developed a new synthesis method for stable La2CoO4+δ nanoparticles that can be used as a highly active heterogeneous catalyst for PMS-assisted oxidation of organic pollutants.

Crystallographic phase formation of iron oxide particles produced from iron nitrate by liquid flame spray with a dual oxygen flow

AbstractWe fabricated iron oxide particles from iron(III) nitrate in a liquid flame spray synthesis. Unlike in most liquid flame spray studies, we implemented a secondary oxygen flow. The effect of the gas flow setup and two additives to the precursor solution, oxalic acid and citric acid, on the resulting particles was studied, with the focus on crystallographic phase composition. The synthesis yielded either pure maghemite or maghemite/hematite mixed phase powders. For solutions without additives, the maghemite fraction was almost linearly dependent on the equivalence ratio. The specific surface area was highest for the smallest equivalence ratios, then decreased, and increased again for the highest values. Some variation was observed between samples with equal equivalence ratios but the total oxygen flow divided differently between the two oxygen channels, a higher atomization flow promoting larger hematite fraction, and higher specific surface area. Both additives reduced the amount of hematite in the powder samples, citric acid being the more efficient one. Citric acid slightly raised the specific surface area, whereas oxalic acid dropped it in half.

Spray Flame Synthesis (SFS) of Lithium Lanthanum Zirconate (LLZO) Solid Electrolyte.

A spray-flame reaction step followed by a short 1-h sintering step under O2 atmosphere was used to synthesize nanocrystalline cubic Al-doped Li7La3Zr2O12 (LLZO). The as-synthesized nanoparticles from spray-flame synthesis consisted of the crystalline La2Zr2O7 (LZO) pyrochlore phase while Li was present on the nanoparticles’ surface as amorphous carbonate. However, a short annealing step was sufficient to obtain phase pure cubic LLZO. To investigate whether the initial mixing of all cations is mandatory for synthesizing nanoparticulate cubic LLZO, we also synthesized Li free LZO and subsequently added different solid Li precursors before the annealing step. The resulting materials were all tetragonal LLZO (I41/acd) instead of the intended cubic phase, suggesting that an intimate intermixing of the Li precursor during the spray-flame synthesis is mandatory to form a nanoscale product. Based on these results, we propose a model to describe the spray-flame based synthesis process, considering the precipitation of LZO and the subsequent condensation of lithium carbonate on the particles’ surface.

Atmospheric-pressure particle mass spectrometer for investigating particle growth in spray flames

In this work, we introduce a new particle mass spectrometer (AP-PMS) that is able to detect particle-size distributions at ambient pressure using a three-stage pumping design. This device is demonstrated for direct sampling from the particle formation in spray-flame synthesis of iron oxide nanoparticles. Aerosol sampling is performed by a probe with integrated dilution that has been characterized and configured by computational fluid dynamics simulations and the chamber-skimmer system has been investigated by schlieren imaging. The system was validated by detailed characterization of a standardized sooting flame and by iron oxide nanoparticles generated in the SpraySyn burner from iron nitrate dissolved in a mixture of ethanol and 2-ethylhexanoic acid. The PMS results are compared to additional inline measurements with SMPS and ELPI + as well as with TEM measurements of thermophoretically sampled materials from the same location in the spray flame.

Characterization of tracers for two-color laser-induced fluorescence thermometry of liquid-phase temperature in ethanol, 2-ethylhexanoic-acid/ethanol mixtures, 1-butanol, and o-xylene.

The fluorescence spectra of dye solutions change their spectral signature with temperature. This effect is frequently used for temperature imaging in liquids and sprays based on two-color laser-induced fluorescence (2cLIF) measurements by simultaneously detecting the fluorescence intensity in two separate wavelength channels resulting in a temperature-sensitive ratio. In this work, we recorded temperature-dependent absorption and fluorescence spectra of solutions of five laser dyes (coumarin 152, coumarin 153, rhodamine B, pyrromethene 597, and DCM) dissolved in ethanol, a 35/65 vol.% mixture of ethanol/2-ethylhexanoic acid, ethanol/hexamethylsiloxane, o-xylene, and 1-butanol to investigate their potential as temperature tracers in evaporating and burning sprays. The dissolved tracers were excited at either 266, 355, and 532 nm (depending on the tracer) for temperatures between 296 and 393 K (depending on the solvent) and for concentrations ranging between 0.1 and 10 mg/l. Absorption and fluorescence spectra of the tracers were investigated for their temperature dependence, the magnitude of signal re-absorption, the impact of different solvents, and varying two-component solvent compositions. Based on the measured fluorescence spectra, the tracers were analyzed for their 2cLIF temperature sensitivity in the respective solvents. Coumarin 152 showed for single-component solvents the overall best spectroscopic properties for our specific measurement situation related to temperature imaging measurements in spray-flame synthesis of nanoparticles as demonstrated previously in ethanol spray flames [Exp. Fluids61, 77 (2020)10.1007/s00348-020-2909-9].

Scalable Synthesis of Ultrasmall Metal Oxide Radio-Enhancers Outperforming Gold

Nanoparticle-based radio-enhancement has the potential to improve cancer cell eradication by augmenting the photoelectric cross-section of targeted cancer cells relative to the healthy surroundings. Encouraging results have been reported for various nanomaterials, including gold and hafnia. However, the lack of scalable synthesis methods and comparative studies is prohibitive to rationalized material design and hampers translation of this promising cancer management strategy. Here, we present a scalable (>100 g day–1) and sterile alternative to conventional batch synthesis of group IV metal oxides (TiO2, ZrO2, and HfO2), which yields near-monodisperse ultrasmall metal oxide nanoparticles with radio-enhancement properties. Access to group IV oxide nanoparticles, which solely differ in atomic number but otherwise exhibit comparable morphologies, sizes, and surface chemistries, enables the direct comparison of their radio-enhancement properties to rationally guide material selection for optimal radio-enhancement performance. We show that the metal oxide nanoparticles exhibit atomic-number-dependent radio-enhancement in cancer cells (HT1080 and HeLa), which is attenuated to baseline levels in normal fibroblasts (normal human dermal fibroblasts). The observed radio-enhancement effects show excellent agreement with physical dose enhancement and nanoparticle dosimetry calculations. Direct benchmarking against gold nanoparticles, the current gold standard in the field, rationalizes the use of hafnia nanoparticles based on their radio-enhancement performance, which is superior to equi-sized gold nanoparticles. Taken together, the competitive radio-enhancement properties for near-monodisperse nanoparticles produced by scalable and sterile flame spray synthesis offer a route to overcoming key roadblocks in the translation of nanoparticle-based radio-enhancers.

Influence of angled dispersion gas on coaxial atomization, spray and flame formation in the context of spray-flame synthesis of nanoparticles

Liquid atomization determines the initial conditions for flame formation and particle synthesis. Without a stable flame, high droplet velocities and thus short droplet residence time in the flame may lead to droplets being injected into an extinguished flame, which influences synthesis and final particle output. An experimental investigation of spray formation and flame stability is performed through high-speed visualization. Targeted variation of nozzle geometry is applied to improve spray-flame interaction and compared to a standardized burner. Timescales of spray density and flame fluctuations are quantified and compared, where the latter were significantly larger and hence not correlated. Instead, dispersion gas forms a barrier between spray phase and pilot flame; hence, ignition depends on large liquid lumps with high radial momentum to break through the dispersion gas for spray ignition. Angling of dispersion gas flow increases radial shear and turbulence and leads to refined atomization and improved flame stability. To investigate the nozzle influence on particle formation, particle characteristics are examined by online and offline analytics with focus on particle structures and product purity. The modified nozzle produced smaller primary particle sizes, thus indicating a sensitivity of sintering dominance on the nozzle geometry. Impurities impact the examination of particle structures and general particle functionality. Carbon contamination was apparent in synthesized particles and also indicated sensitivity to nozzle geometry. Discrepancies to literature data are discussed regarding differences in flame activity and droplet characteristics. The report highlights, how product characteristics can differ crucially due to changes in nozzle geometry despite comparable operating conditions.Graphic abstract

Solid-liquid equilibria in mixtures of iron(III) nitrate nonahydrate and ethanol or 1-propanol

Solutions of iron(III) nitrate nonahydrate (INN) in ethanol and 1-propanol are interesting starting materials for producing iron oxide nanoparticles by spray flame synthesis. For the design of these processes, it is important to have information on solid-liquid equilibria (SLE) in these solutions. As corresponding data were not available in the literature, we have studied the SLE of solutions of INN in ethanol and 1-propanol experimentally at temperatures between 288.15 and 308.15 K at 101.3 kPa. Unexpected phenomena occur in these solutions: one would expect an increasing amount of precipitate upon increasing the concentration of the salt INN, but the reverse behavior is observed for a wide range of states. This is caused by chemical reactions in the solutions: not INN, but iron(III) hydroxide (IH) precipitates from the solution, leading also to a strong acidity of the mixture. These chemical effects are taken into account in a physico-chemical model that was developed for describing the SLE in the studied systems. In that model, the physical non-ideality is described with the extended Pitzer model.

Thermophysical Properties of Mixtures of Titanium(IV) Isopropoxide (TTIP) and 2-Propanol (iPOH)

The present work provides thermophysical data on binary mixtures of titanium(IV) isopropoxide (TTIP) and 2-propanol (iPOH), which are important precursor solutions in spray flame synthesis of nanoparticles. The specific density, viscosity, thermal conductivity, and molar isobaric heat capacity were measured at 101.3 kPa and temperatures ranging from 293.15 to 333.15 K. The vapor–liquid equilibrium (VLE) was measured at pressures ranging from 20 to 80 kPa. Furthermore, self-diffusion coefficients of pure iPOH were measured at 101.3 kPa and temperatures ranging from 293.15 to 333.15 K. A qualitative study using 1H NMR spectroscopy provides evidence for a cross-association between TTIP and iPOH in the mixture. Correlations for all studied thermophysical properties are provided. The results establish a rational basis for the design of spray flame synthesis processes.

Spray-Flame Synthesis of LaMnO3+δ Nanoparticles for Selective CO Oxidation (SELOX)

LaMnO3+δ nanoperovskites were prepared via the continuous and scalable spray-flame synthesis (SFS) technique from metal nitrate-based solutions by using either ethanol (EtOH) as solvent or a mixtur...

Spray-flame synthesis of LaMO3 (M = Mn, Fe, Co) perovskite nanomaterials: Effect of spray droplet size and esterification on particle size distribution

Perovskite nanomaterials such as LaMnO3, LaFeO3, and LaCoO3 were synthesized in a spray flame from metal nitrates dissolved in combustible liquids. The addition of low-boiling solvents such as 2-ethylhexanoic acid (2-EHA) to the ethanol-based solutions supports the formation of phase-pure particles with unimodal particle-size distribution in the 10-nm range attributed to enhanced evaporation through micro-explosions. Nevertheless, in many cases, a second particle mode with sizes of a few hundred nanometers is formed. In this paper, we investigate two possible reasons for the appearance of large particles. Firstly, we analyze the effect of the oxygen dispersion gas flow applied in the two-fluid nozzle on the droplet size distributions of burning sprays using phase Doppler anemometry. We identified that an increase of the dispersion gas flow significantly decreases the number concentration of large droplets (>30 μm), which causes a significant increase of the BET surface area of as-synthesized LaMnO3 and LaCoO3 with increasing dispersion gas flow from 60 m2/g (5 slm dispersion gas) to 100 m2/g (8 slm). Secondly, the esterification in the mixture of solvents towards ethyl-2-ethylhexanoate, which is associated with the release of water as a byproduct, was analyzed by GC/MS. The ester concentration in the iron-containing solution was found to be up to nine times higher than in cobalt or manganese precursor solutions. Simultaneously, the produced LaFeO3 materials show lower BET surface areas and the increasing dispersion gas flow has a minor effect on this material than on the cobalt and manganese perovskite cases. We attribute this to the fact that water formed during esterification forces the hydrolysis of iron nitrate and the formation of large particles within the droplets.

Tuning the Co Oxidation State in Ba0.5Sr0.5Co0.8Fe0.2O3-δ by Flame Spray Synthesis Towards High Oxygen Evolution Reaction Activity

The perovskite-type oxide Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is known as a highly active and stable oxygen evolution reaction (OER) electrocatalyst composited out of non-noble metals. The possibility of using the scalable flame spray synthesis (FSS) technique for the production of BSCF nanoparticles intensified the interest in this material for a future application in an alkaline water electrolyzer. A possible scale-up would require the optimization of the synthesis parameters to maximize the production rate. To further understand the influence of the synthesis parameters of the tunable FSS on the OER activity of BSCF, a systematic study was carried out by producing BSCF with different total metal concentrations (CTM), flow rates of the precursor solution (FRPS) and of the dispersion gas (FRDG). This study reveals that all three parameters have a direct impact on the OER activity of BSCF—measured in a rotating disc electrode (RDE) setup—due to the controllability of the initial Co and Fe oxidation state—indicated by X-ray absorption spectroscopy (XAS) measurements—and with that also of the oxygen vacancy concentration in the as-synthesized BSCF. This controllability enables the optimization of the OER activity of BSCF and emphasizes the importance of having Co in a lower initial oxidation state for reaching a high electrocatalytic performance.

Investigation of flame spray synthesized La1-xSrxCoO3 perovskites with promotional catalytic performances on CO oxidation

To enhance the activity of catalysts for CO removal, the perovskite-type catalysts La1-xSrxCoO3 (x = 0, 0.2, 0.4, 0.6, and 0.8) with different Sr2+ doping amount were synthesized by flame spray synthesis (FSS) method. The perovskite-type catalyst synthesized by FSS has a much larger specific surface area (SSA) than that prepared by other conventional methods. The SSA of catalyst increases with the increase of Sr2+ doping amount and the SSA of La0.2Sr0.8CoO3 reaches 31.65 m2/g. Compared with other conventional methods, FSS method significantly improves the activity of catalyst and makes it close to the performances of catalysts with surface modification. The substitution of La3+ by Sr2+ promotes the generation of secondary phase Co3O4 and SrCO3. The catalytic activity of La1-xSrxCoO3 increases with the addition of Sr2+, which results from the increasing active sites and oxygen vacancies. Interestingly, La0.4Sr0.6CoO3 performs the highest activity for CO oxidation and the CO conversion reaches 50% at 148.6 °C and 90% at 165.9 °C. The oxidation of CO over La1-xSrxCoO3 catalyst may follow a combination of MvK and L-H mechanisms according to the experimental results of H2-TPR. Moreover, the catalyst exhibits good catalytic activity in consecutive oxidation cycles. In consecutive oxidation experiments with La0.4Sr0.6CoO3, the CO conversion reaches 50% at 168.8 °C and 90% at 197.8 °C in the eighth oxidation cycle. These results prove that FSS method can further improve the activity of catalysts and is suitable for the preparation of efficient catalysts.

Dual-Wavelength Excited Intense Red Upconversion Luminescence from Er3+-Sensitized Y2O3 Nanocrystals Fabricated by Spray Flame Synthesis.

Er3+-sensitized upconversion nanoparticles (UCNPs) have attracted great attention due to their tunable upconversion (UC) emissions, low cytotoxicity, high resistance to photobleaching and especially multiple effective excitation wavelengths. However, detailed energy conversion between Er3+ and Tm3+ ions in Y2O3 UCNPs is still a problem, especially under multi-wavelength and variable pulse width excitation. In this work, we successfully fabricated a series of Er3+-sensitized Y2O3 nanocrystals by a spray flame synthesis method with a production rate of 40.5 g h−1. The as-prepared UCNPs are a pure cubic phase with a mean size of 14 nm. Excited by both 980 and 808 nm lasers, the tunable upconversion luminescence (UCL) from Er3+ ions was achieved by increasing the Er3+ doping concentration, co-doping Tm3+ ions and extending excitation pulse-width. The investigations of the lifetimes and the laser power dependence of UC emissions further support the proposed mechanism, which provides guidance for achieving effective color control in anticounterfeiting and multiplexed labeling applications. In addition, the red UC emission at about 5 mm beneath the tissue surface was observed in an ex vivo imaging experiment under the excitation of 808 nm laser, indicating that the Y2O3:Er3+/Tm3+ UCNPs have great prospects in further biological applications.

Uncovering Atomic‐Scale Stability and Reactivity in Engineered Zinc Oxide Electrocatalysts for Controllable Syngas Production

AbstractIn this study, scalable, flame spray synthesis is utilized to develop defective ZnO nanomaterials for the concurrent generation of H2 and CO during electrochemical CO2 reduction reactions (CO2RR). The designed ZnO achieves an H2/CO ratio of ≈1 with a large current density (j) of 40 mA cm−2 during long‐term continuous reaction at a cell voltage of 2.6 V. Through in situ atomic pair distribution function analysis, the remarkable stability of these ZnO structures is explored, addressing the knowledge gap in understanding the dynamics of oxide catalysts during CO2RR. Through optimization of synthesis conditions, ZnO facets are modulated which are shown to affect reaction selectivity, in agreement with theoretical calculations. These findings and insights on synthetic manipulation of active sites in defective metal‐oxides can be used as guidelines to develop active catalysts for syngas production for renewable power‐to‐X to generate a range of fuels and chemicals.

Thermophysical Properties of Solutions of Iron(III) Nitrate-Nonahydrate in Mixtures of Ethanol and Water

The quality of nanoparticles that are obtained by spray flame synthesis depends strongly on the thermophysical properties of the precursor solutions. Solutions of iron(III) nitrate-nonahydrate (INN...

Size Effect in Nanostructured SnO2/TiO2 Gas Sensors

Introduction Size effect in resistive-type responses to gases has been demonstrated for the first time in the case of SnO2 polycrystalline sensors [1]. Since then it is believed that the smallest the grain size, the higher change in the electrical resistivity of metal oxide nanomaterials can be expected upon interaction with oxidizing or reducing gases. This belief is based on the argument that the surface-to-volume ration increases with a decrease in the grain diameter and as a gas adsorption is a surface process this in consequence leads to an increased density of active sites available for gas-solid interaction [2-3].Therefore, the size reduction has been considered as a fundamental strategy for nanosensors, justifying an enormous effort towards application of nanotechnology in gas sensing devices.A closer look at this issue reveals that such simplified reasoning is not always true. Geometrical decrease in the grain size below 10 nm for SnO2 does not necessarily mean to be a good solution for other oxides such as TiO2. In fact, the most important is a comparison between the grain diameter d and the Debye length λD defined as: λD={(ε ε0φS)/(eND)}1/2 where ε and ε0 denote relative permittivity of the material and vacuum permittivity, respectively, φ S is the surface potential, e represents electron charge and ND stands for donor concentration.When the condition d << λD is fulfilled, the size effect should play a substantial role in gas sensing. Therefore, the aim of this work is to investigate the size effect in the electrical resistivity of SnO2/TiO2 upon interaction with oxidizing/reducing gases by intentional modification of λD by influencing: the electrical properties through donor concentration ND the structural properties through anatase to rutile ratio thus affecting relative permittivity, εmorphology through its impact on the surface potential, φ S Technology TiO2/SnO2 bi-layer nanoheterostructures have been synthesized in a two-step process: (i) magnetron sputtering, MS, followed by (ii) Langmuir-Blodgett, LB technique [4]. Mixed TiO2/SnO2 composites have been obtained by means of Flame Spray Synthesis, FSS [5], sol-gel [6] and by mechanical mixing of commercial Sigma-Aldrich nanopowders [7]. Experimental Methods Crystallographic structure of the nanocomposites was studied by X-ray diffraction in Bragg-Brentano geometry while that of thin films was determined by X-ray diffraction in grazing incidence GID geometry using Philips X’pert Pro diffractometer. Scanning electron microscopy SEM investigations were carried out with the use of FEI Nova Nano SEM 200 microscope. Transmission electron microscopy TEM was employed to study the morphology of the nanopowders. FEI Tecnai TF 20 X-TWIN microscope was used. Gas sensing properties were established by measuring resistive-type responses to hydrogen, and NO2 vs. time, within a temperature range of 200-400oC both in dc and ac mode. The experimental setup for sensor characterization was already described in [8]. Sensitivity of the sensors to the reducing gas was defined as R0/R while that to the oxidizing as R/R0, where R0 is the baseline resistance in the reference gas, i.e. in air. Results and Conclusions Nanopowders of TiO2 with different crystallite size, grown by FSS, demonstrate a size effect in the electrical conductivity (Fig.1a) which can be attributed to the activation energy decreasing with the particle size. No grain size effect in hydrogen sensing has been observed.Bi-layered heterostructures synthesized on special gas sensor substrates with precisely defined interdigital electrodes were tested towards NO2 detection over the low concentration range from 200 ppb to 20 ppm.High response to low concentration of NO2 (Fig. 1b) could be accounted for by two factors: particular morphology of SnO2 base layer with small, well-dispersed grains indicating possibility of a grain size effectwell-developed, rough surface of TiO2 overlayer grown by the LB technique. Acknowledgement National Science Center NCN, Poland project no. 2016/23/B/ST7/00894 is acknowledged.

Droplet sizing in spray flame synthesis using wide-angle light scattering (WALS)

In spray flame synthesis the processes of spray formation and evaporation of the single droplets greatly affect the morphology and size of particles formed. An in situ measurement of these parameters is thus essential for process control and development. In this work, wide-angle light scattering (WALS) is applied to measure droplet sizes in a spray flame. The scattering data of the spherical droplets are evaluated by applying Mie-theory. For droplet sizing, the number of characteristic maxima in the scattering pattern and the measured scattering intensities are evaluated. Droplet size distributions and their parameters were determined by repetitive exposures in various heights above the nozzle outlet for two solvents: pure ethanol and a mixture of ethanol and 2-ethylhexanoic acid at a volume ratio of 35/65. While for ethanol the median droplet size decreases with increasing height, it decreases less for the mixture, which in general exhibits increased droplet sizes for all heights compared to pure ethanol. Furthermore, we could show that using air instead of nitrogen as a co-flow barely affects droplet evaporation in the flame.

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

Flame spray pyrolysis is an important method of nanoparticle manufacturing. Reactions of the precursor and the solvent determine which intermediates can contribute to particle formation. To investigate the chemical interaction between the solvent and the precursor during the partial evaporation of the spray preceding ignition, precursor solutions were sprayed into an externally heated flow reactor. The thermal decomposition of the precursors Fe(CO)5, Fe(C5H5)2, and Ti(i-OC3H7)4 in solutions of xylene and ethanol was investigated. Decomposition products were analyzed by mass spectrometry. The relevance of reactions at these low temperatures for the spray-flame process is substantiated by measurements of the spatial temperature distribution of the spray flame. Depending on the relative thermal stabilities of the precursor and the solvent, the less stable component can initiate decomposition of the more stable component, resulting in different reaction patterns of the solutions. The results are discussed with regard to their potential influence on particle formation pathways.