Influence of Sampling and Storage Protocol on Fractal Morphology of Soot Studied by Transmission Electron Microscopy

Figures & data

FIG. 1 The burner and the experimental setup used to sample soot particles in the ethylene diffusion flame.

TABLE 1 Gaussian fit parameters for the four sampling protocols TPP, TPS, IPS, and NFS, with standard deviation in parentheses

Sampling method	Number of primary particles	Dpp (nm)	Number of pairs of overlapped primary particles	Overlap coefficient Cov
TPP	814	24.4 (5.2)	111	0.18 (0.05)
TPS	764	26.9 (5.9)	113	0.20 (0.04)
IPS	958	26.8 (5.8)	90	0.17 (0.05)
NFS	904	37.1 (6.6)	229	0.23 (0.03)

FIG. 2 TEM micrographs of samples collected by TPP, TPS, IPS, and NFS and stored in a N₂ atmosphere in the dark.

FIG. 3 Probability density function of the gyration diameter obtained for the four sampling protocols (Number of aggregates analyzed: 211 for TPP, 141 for TPS, 202 for IPS, and 225 for NFS).

FIG. 4 The number of primary particles in the aggregates as a function of the ratio between gyration and primary particle diameters.

TABLE 2 Influence of the NFS transfer procedure on morphological parameters. This influence is analyzed by applying carbon deposition (C) to TPP and TPS grids (standard deviation for D_pp and geometric standard for D_g in parentheses)

Protocol	Treatment	Df	kf	Cov	Dpp (nm)	(nm)	(nm)
TPP	Before C	1.7 (0.22)	2.37 (1.38)	0.16 (0.04)	26.5 (5.0)	19.0 (4.4)	100.1 (2.2)
	After C	1.82 (0.22)	2.33 (1.34)	0.18 (0.05)	38.6 (6.1)	25.9 (5.6)	128.4 (2.0)
TPS	Before C	1.76 (0.16)	2.28 (1.08)	0.17 (0.06)	33.4 (6.1)	22.7 (6.3)	122.9 (2.2)
	After C	1.82 (0.21)	2.43 (1.42)	0.23 (0.06)	42.9 (8.0)	26.3 (6.5)	151.6 (2.0)
	After CHCl3	1.77 (0.19)	2.45 (1.08)	0.28 (0.04)	44.6 (9.7)	25.4 (7.2)	139.5 (1.8)

TABLE 3 Evolution of morphological parameters as a function of storage duration in air and nitrogen; with standard deviation for D_pp and geometric standard deviation for D_g in parentheses. The initial values for TPP with nitrogen correspond to results analyzed in the previous section (Table 1; Figure 4)

Protocol	Storage duration (days)	Df	kf	Cov	Dpp (nm)	(nm)
TPP (air)	33	1.68 (0.18)	2.69 (1.39)	0.16 (0.05)	28.2 (4.8)	154 (1.9)
	109	1.70 (0.18)	2.54 (1.42)	0.18 (0.07)	22.9 (3.7)	149 (1.9)
	211	1.70 (0.20)	2.70 (1.41)	0.23 (0.03)	27.1 (4.5)	132 (1.9)
	336	1.65 (0.24)	2.88 (1.48)	0.27 (0.03)	29.0 (4.7)	126 (1.7)
TPP (nitrogen)	110	1.76 (0.09)	2.09 (1.14)	0.18 (0.05)	24.4 (5.2)	79 (2.1)
	372	1.83 (0.14)	2.07 (1.07)	0.21 (0.04)	26.4 (4.7)	97 (2.4)
TPS (nitrogen)	81	1.76 (0.10)	2.17 (1.18)	0.20 (0.04)	26.9 (5.9)	123 (2.3)
	372	1.76 (0.16)	2.28 (1.08)	0.17 (0.06)	33.4 (6.1)	123 (2.2)
IPS (nitrogen)	60	1.80 (0.09)	2.23 (1.13)	0.17 (0.05)	26.8 (5.8)	86 (2.4)
	348	1.84 (0.12)	2.17 (1.07)	0.22 (0.02)	27.7 (6.2)	80 (2.3)
NFS (air)	39	1.74 (0.12)	2.32 (1.25)	0.20 (0.03)	36.0 (6.5)	221 (2.4)
	110	1.74 (0.16)	2.66 (1.30)	0.24 (0.04)	35.1 (5.8)	171 (2.1)
	214	1.79 (0.18)	2.51 (1.31)	0.28 (0.06)	42.7 (6.9)	174 (1.8)
	337	1.76 (0.19)	2.52 (1.34)	0.30 (0.04)	40.6 (7.1)	167 (1.8)

FIG. 5 Evolution of the overlap coefficient as a function of the storage duration in air and nitrogen (three TEM micrographs are shown as an illustration of the increase in the overlap coefficient).