Morphology and Raman spectra of aerodynamically classified soot samples

Abstract

Abstract. Airborne soot is emitted from combustion processes as aggregates of primary particles. The size of the primary particles and the overall aggregate size control soot transport properties, and prior research shows that these parameters may be related to the soot nanostructure. In this work, a laminar, inverted nonpremixed burner has been used as a source of soot that is almost completely elemental carbon. The inverted burner was connected to an electrical low-pressure impactor, which collected particles on stages according to the aerodynamic diameter, from 0.03 to 10 µm. The morphology was analyzed using a transmission electron microscope followed by image processing to extract projected area and average primary particle size for each aggregate (approximately 1000 aggregates analyzed in total for the nine impactor stages). Carbon nanostructure was analyzed using a Raman spectrometer, and five vibrational bands (D4, D1, D3, G, and D2) were fitted to the spectra to obtain an estimate of the carbon disorder. The average primary particle diameter increases from 15 to 30 nm as the impactor stage aerodynamic diameter increases. The D1, D3, D2, and D4 bands decreased (relative to the G band) with the particle size, suggesting that the larger aggregates have larger graphitic domains.

Size-dependent mass absorption cross-section of soot particles from various sources

“…A size-dependent refractive index implies a size-dependent 𝐸 𝑔 (Equation 9), and a size-dependent 𝐸 𝑔 implies a size-dependent degree of graphitization (maturity) of soot [23]. This conclusion is consistent with previous Raman spectroscopy measurements of a size-dependent soot maturity (degree of graphitization) for inverted-diffusionflame soot [27,34].…”

“…We also report the primary particle diameters in terms of 𝑑 𝑝𝑝,100 (the mean primary particle diameter of 𝑑 𝑚 = 100 nm aggregates) from literature for the Gnome [46] and Argonaut MISG [34] , for example, as produced by the UDAC-CPMA system described below. We note that the UDAC-CPMA system physically classifies particles by mass, not size, but we use the term sizeintegrated to avoid confusion as discussed in Section 3.…”

“…Dastanpour et al also measured a size-dependent soot maturity based on particle mobility diameter dm, for 125 < 𝑑 𝑚 < 300 nm particles using Raman spectroscopy [27,34] and attributed their observed size-dependent MAC to this trend. A quantitative model for the evolution of soot maturity in flames was subsequently described by Kelesidis and Pratsinis [35].…”

Sprayable, Superhydrophobic, Electrically, and Thermally Conductive Coating

“…CNTs or CNFs have been used before for making coatings. [ 7,9,42,58,59 ] Most of the previous works used expensive and complicated procedure; a few of the previous studies used spray drying. Table 1 summarizes the literature for the last decade.…”

Real-time measurements of formaldehyde emissions in a gross anatomy laboratory

“…Formaldehyde can be generated by a broad range of sources, such as biomass combustion, oxidation of volatile organic compounds (VOCs) and reactions between ozone (mainly from outdoors) and alkenes [4,28,37,45,55]. Some indoor sources are smoking, heating, cooking, candle or incense burning, building materials and consumer products [23,25,36,38,43].…”