Nanomaterials 2022 , 12 , 790
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fibers in the nanometric scale due to the more intensity of chemical pretreatment than R-CMF. When the velocity gradient is low, R-CNF and R-CMF are not well dispersed in the solvent, as part of the fibrils are positioned together, and if they do not separate with more agitation, they settle as a single particle, forming aggregates or clusters. On the other hand, when the agitation is higher than that performed in the minimum Ø g , the fibrils network is destroyed due to the mechanical forces and the fibrils are compacted in the base of the graduated cylinders as the representation of fibre network disposition shows in Figure 6. Moreover, Table 2 shows statistical parameters of the diameter fibers including the number of samples analyzed in TEM images, the geometric mean with a 95% confidence interval, the median of each sample (to avoid the deviation of the statically tails) and the 95th percentile to evaluate the diameter of the higher fibers discarding values that may be exceptional. Finally, the length of fibrils was calculated from the AR values and the geometric mean diameter.
3s -1
70s -1 125s -1 500s -1 2500s -1
R-CNF
50s -1 500s -1 900s -1 2500s -1
R-CMF R
Figure 6. Representations of fibril network in the deposit of the graduated cylinders at increasing agitation speeds. Table2. Statistical parameters of diameter distribution of CMF/CNF samples from TEM images and estimation of aspect ratio and length of fibers.
Geometric Mean of Diameter (nm)
Length ( μ m)
Diameter D(0.95) (nm)
Number of Samples Measured (Fibers)
Velocity Gradient (s − 1 )
Diameter Median (nm)
95% Confidence Interval
Mean
CN EMT
R-CNF
3
(17.4, 20.3) (14.4, 16.5) (14.0, 15.9) (11.8, 13.6)
18.8 15.4 14.9 12.6 10.7 43.9 32.8 32.4 29.8
18.9 15.3 14.1 11.8 10.9
50.7 38.0 39.0 40.7 27.4 379 145 136 111
261 237 311 366 242 316 259 366 295
1.89 1.72 1.64 1.17
1.67 1.53 1.46 1.02
70
125 500
2500
(9.9, 11.5)
<0.9 *
<0.8 *
R-CMF
50
(39.0, 49.5) (29.5, 36.4) (29.7, 35.3) (27.4, 32.4)
40.0 31.5 33.9 26.8
5.44 4.77 4.34
4.93 4.41 3.98
500 900
2500
<3.2 * <2.9 * * Gel point at 2500 s − 1 was not determined with precision due to the low deposits obtained. Therefore, a minimum value to obtain the maximum length of fibrils at that stirring speed is assumed.
Analyzing both samples separately, R-CNF, with a high homogeneity of the fibrils due to TEMPO pretreatment, show at low velocity gradient (~3 s − 1 ) the initial gel state of the
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