silicon for the chemical and solar industry XIII

Figure 12:

Field emission SEM micrograph of pyrogenic silica agglomerate.

Accurate particle sizing of pyrogenic silica agglomerates is challenging due to shear

sensitivity of the internal structure of the agglomerates. The aggregates within the

agglomerate structure interact by relatively weak dispersion forces. Application of

mechanical shear during sample preparation and measurement are able to overcome the

dispersion forces and will therefore affect the resulting particle size and particle size

distribution [31]. The effect of shear on pyrogenic silica particle size is illustrated in

Fig. 13, which shows the maximum readings of the nm-mode and μm-mode of the

particle size distribution of a laser light diffraction experiment of an aqueous pyrogenic

silica dispersion containing 1 wt% of pyrogenic silica of 300 m

/g SSA with increasing

stirring time.

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