Unveiling trends in soot nucleation and growth: When secondary ion mass spectrometry meets statistical analysis

Abstract

At the present day, ultrafine soot particles have become the object of increasing attention due to their well-documented adverse effects on human health and climate. In particular, understanding soot nucleation is one of the most challenging problems toward a more controlled and cleaner combustion. Detailed information on the chemistry of nascent soot particles (NSPs) is expected to provide clues on the soot formation and growth reaction pathways. Herein, the early steps of soot formation in flames are addressed by investigating the chemical composition of NSPs and their molecular precursors by secondary ion mass spectrometry. The originality of this work lies on the combination of several factors that include: two different approaches to gain access to soot nucleation in premixed flames (analysis of a nucleation flame in which NSPs nucleate all along the reaction coordinate without growing in size) and in diffusion flames (separation of the precursors and soot regions); a sampling procedure that allows a rough separation of the condensable gas phase from soot particles; a large database of collected samples and high mass resolution that enable the use of an improved data reduction protocol based on hierarchical cluster analysis and principal component analysis for the data mining and interpretation.

Dimers of polycyclic aromatic hydrocarbons: the missing pieces in the soot formation process

“…Laser induced incandescence (LII) experiments were performed at 1064 nm using the fundamental of a pulsed Nd:YAG laser (Quantel Brilliant B, 6 ns pulse width, 10 Hz), already reported in a previous paper 33 . Soot particles were heated below the sublimation threshold with a top hat profile at a fluence of 130 mJ cm -2 and a square shape of the laser beam profile (1x1,1 mm).…”

Influence of the dry aerosol particle size distribution and morphology on the cloud condensation nuclei activation. An experimental and theoretical investigation

“…Soot formation in flame combustion is a complex process, strongly affected, among other factors, by the fuel nature, the local fuel-air equivalence ratio and the flame temperature (D'Anna, 2009;Wang, 2011;Karataş and Gülder, 2012). At a short reaction time, equivalently at a low height above the burner (HAB), the oxidation of the fuel generates small radicals that quickly recombine to form larger and larger hydrocarbons, molecular ions and radicals.…”

Authors' response to reviewer's comments

“…We recently showcased the advantages of using advanced statistical techniques (Duca et al, 2019;Irimiea et al, 2018Irimiea et al, , 2019 to highlight subtle differences in the chemical composition of various samples. It is also very useful to confirm initial trends deduced from a descriptive approach of the mass spectra with a more quantitative approach such as that provided by the statistical analyses.…”