Combustion-formed nanoparticles

D’Anna, Andrea

doi:10.1016/j.proci.2008.09.005

Cited by 326 publications

(122 citation statements)

References 118 publications

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“…7 PAH formation and properties in flames are of great importance, because PAHs are generally considered to be molecular precursors to soot particles. [8][9][10][11] Mass spectrometry is a commonly used method for measuring samples extracted from flames because it enables simultaneous or nearly simultaneous detection of multiple species. In addition to mass analysis, molecular-beam mass spectrometry studies using vacuum ultraviolet (VUV) radiation for photoionization have shown that identification of isomers of small gas-phase hydrocarbons in flames can be accomplished using photoionization-efficiency (PIE) analysis, i.e., analysis of the photon-energy dependence of a peak in a mass spectrum.…”

Section: Introductionmentioning

confidence: 99%

Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species

et al. 2017

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We present a critical evaluation of photoionization efficiency (PIE) measurements coupled with aerosol mass spectrometry for the identification of condensed soot-precursor species extracted from a premixed atmospheric-pressure ethylene/oxygen/nitrogen flame. Definitive identification of isomers by any means is complicated by the large number of potential isomers at masses likely to comprise particles at flame temperatures. This problem is compounded using PIE measurements by the similarity in ionization energies and PIE-curve shapes among many of these isomers. Nevertheless, PIE analysis can provide important chemical information. For example, our PIE curves show that neither pyrene nor fluoranthene alone can describe the signal from C16H10 isomers and that coronene alone cannot describe the PIE signal from C24H12 species.A linear combination of the reference PIE curves for pyrene and fluoranthene yields good agreement with flame-PIE curves measured at 202 u, which is consistent with pyrene and fluoranthene being the two major C16H10 isomers in the flame samples, but does not provide definite proof. The suggested ratio between fluoranthene and pyrene depends on the sampling conditions. We calculated the values of the adiabatic-ionization energy (AIE) of twenty-four C16H10 isomers. Despite the small number of isomers considered, the calculations show that the differences in AIEs between several of the isomers can be smaller than the average thermal energy at room temperature. The calculations also show that PIE analysis can sometimes be used to separate hydrocarbon species into those that contain mainly aromatic rings and those that contain significant aliphatic content for species sizes investigated in this study. Our calculations suggest an inverse relationship between AIE and the number of aromatic rings. We have demonstrated that further characterization of precursors can be facilitated by measurements that test species volatility.3

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Section: Introductionmentioning

confidence: 99%

Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species

et al. 2017

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“…Modeling and experimental activities have demonstrated that fuel-rich flame conditions produce particles with a wide size range roughly grouped in two classes of nanoparticles on the basis of the bimodal shape of the size distribution function (Bockhorn 1994;Wang 2001;Sgro et al 2003;D'Anna 2009;Echavarria et al 2009;Commodo et al 2013). In addition to their sizes, these two classes of particles differentiate by chemical structure, morphology, and optical and spectroscopy behaviors.…”

Section: Introductionmentioning

confidence: 99%

Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Falco

Commodo

Minutolo

et al. 2015

Aerosol Science and Technology

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Interaction forces acting between combustion-generated carbon particles were studied by using atomic force microscopy (AFM). To this aim, carbon nanoparticles were produced in fuelrich ethylene/air laminar premixed flames with different equivalent ratios F, and analyzed at a fixed residence time in the flame. Particles were collected on mica substrates by means of a thermophoretic sampling system and then analyzed by AFM. A characterization of particle dimension and morphology were performed operating AFM in semicontact mode, showing that the shape of the particles collected on a sampling plate is never spherical. Increasing the flame-equivalent ratio, particle shape moves from an almost atomically thick object to thicker compounds, indicating the transformation from particles made of small, defective graphene-like sheets to particles containing stacked aromatic layers. Attractive and adhesive forces between a titanium nitride probe and sampled particles were calculated from force-distance curves acquired in AFM force spectroscopy mode. Assuming that van der Walls forces are the main contribution to attractive forces, the measurement of attractive forces allowed the evaluation of the Hamaker constant for the carbon particles as a function of the flame-equivalent ratio. The comparison of the measured Hamaker constants with the values for benzene and HOPG, suggests a continuous increase of the aromatic domains and the three-dimensional order within the particles when the flame-equivalent ratio increases.

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“…Particle nucleation, i.e., the transition from gas-phase compounds to solid particles, is the first, though more complex, step in the soot formation process and is still an object of ongoing studies [6][7][8][9]. Several mechanisms have been proposed and are currently being debated for particle inception.…”

Section: Introductionmentioning

confidence: 99%

“…Several mechanisms have been proposed and are currently being debated for particle inception. These include physical clustering of pericondensed aromatic hydrocarbons or oligomers of aromatic hydrocarbons (i.e., compounds with high molecular mass characterized by aromatic functionalities linked by aliphatic bonds) through van der Walls' forces or even the formation of curved fullerenic-like structures [6,7].…”

Section: Introductionmentioning

confidence: 99%

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Exploring Soot Particle Concentration and Emissivity by Transient Thermocouples Measurements in Laminar Partially Premixed Coflow Flames

et al. 2017

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Soot formation in combustion represents a complex phenomenon that strongly depends on several factors such as pressure, temperature, fuel chemical composition, and the extent of premixing. The effect of partial premixing on soot formation is of relevance also for real combustion devices and still needs to be fully understood. An improved version of the thermophoretic particle densitometry (TPD) method has been used in this work with the aim to obtain both quantitative and qualitative information of soot particles generated in a set of laminar partially-premixed co-flow flames characterized by different equivalence ratios. To this aim, the transient thermocouple temperature response has been analyzed to infer particle concentration and emissivity. A variety of thermal emissivity values have been measured for flame-formed carbonaceous particles, ranging from 0.4 to 0.5 for the early nucleated soot particles up to the value of 0.95, representing the typical value commonly attributed to mature soot particles, indicating that the correct determination of the thermal emissivity is necessary to accurately evaluate the particle volume fraction. This is particularly true at the early stage of the soot formation, when particle concentration measurement is indeed particularly challenging as in the central region of the diffusion flames. With increasing premixing, an initial increase of particles is detected both in the maximum radial soot volume fraction region and in the central region of the flame, while the further addition of primary air determines the particle volume fraction drop. Finally, a modeling analysis based on a sectional approach has been performed to corroborate the experimental findings.

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Combustion-formed nanoparticles

Cited by 326 publications

References 118 publications

Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species

Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species

Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Exploring Soot Particle Concentration and Emissivity by Transient Thermocouples Measurements in Laminar Partially Premixed Coflow Flames

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