Detection of combustion formed nanoparticles

Hydrocarbon Nanoparticles Formed in Flames and Diesel Engines

“…Two to four ring PAHs were considered to be the source of the fluorescence displayed by the first soot nuclei whose material densities were estimated to be 1.2 gm/ml. Optical observations and sampling methods followed by atomic force microscopy and differential mobility analysis have been used to identify 2 to 4 nm nanoparticles in flames and from practical combustion systems as well (Sgro et al 2003). This study also showed isolated nanoparticles at Z = 5 mm and a bimodal PSD at Z = 10 mm in the premixed C 2 H 4 flame.…”

“…They have been widely depicted in micrographs obtained by ex-situ sampling from flames where they appear as solitary, sometimes faint particles that are semi-transparent to the electron beam but they may display dark edges or dark internal regions. These nanoparticles have been shown in micrographs of samples from premixed flames (Wersborg et al 1973;Onichuk et al 2003;Sgro et al 2003;Öktem et al 2005), in numerous laminar diffusion flames (Megaridis et al 1989;Dobbins et al 1994Dobbins et al , 1996Dobbins et al , 1998Dobbins, 1997;Vander Wal, 1996Köylü et al 1997;Lee et al 2000); in turbulent flames (Hu et al 2003(Hu et al , 2004Yang et al 2005); in unsteady, flickering flames (Zhang and Megaridis 1998); in bituminous coal flames (Ma et al 1995); in microgravity flames (Konsur et al 1999); in inverse diffusion flames (Blevins et al 2002;Lee et al 2005;Oh et al 2005); in a two meter pool fire (Jensen et al 2005); in a well stirred reactor (Blevins et al 2003); and in an opposed flow flame (Merchan-Merchan et al 2003). Additional details concerning these studies are summarized in Table A1 of Appendix A.…”

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

“…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.…”

“…The mechanism of collision and sticking of small particles can be viewed as due to a balance between the particle kinetic energy and the mutual interaction between the particles (van der Waals forces) (Narsimhan and Ruckenstein 1985); when particles are in the free molecular regime, at high temperature such as that reached in flames, the particle kinetic energy may be higher than the interaction energy, resulting in a thermal rebound effect after collision (Wang and Kasper, 1991). Experimental results (Minutolo et al 1999;Sgro et al 2003;D'Alessio et al 2005) agreed with this simple model showing that flame-formed nanoparticles with 2-5 nm size possess a rate of coagulation lower than that of larger soot particles (20-50 nm) and well below the value predicted by the gas-kinetic theory, thus showing that the coagulation efficiency depends on particle size, morphology, and chemical structure. Moreover, temperature has been demonstrated to play a key role in determining the rate of coagulation of different-sized nanoparticles (Sirignano and D'Anna 2013), also in different temperature regimes.…”

“…However, little is known about the forces, particularly van der Waals interactions, acting between carbon nanoparticles. Also, the Hamaker constants for flame-formed nanoparticles (Minutolo et al 1999;Sgro et al 2003;D'Alessio et al 2005), usually used in the calculation of the particle interaction potential, have been so far mainly assumed on the basis of particle chemical nature, since no direct experimental measurement can be found in the literature.…”