Bridging of Silica Particles

The polysilicic acid globules in silica sols are very small, which does not allow one to conduct the experiments described with single particles. Hence, the experiments were conducted with glass threads (rods) modified with silica particles. These threads were brought into cross-contact in supersaturated silicic acid solutions. 

Physical-Chemical Mechanics of Disperse Systems and Materials 

FIGURE 6.10 Histograms showing the differential distribution of the contact strength, p, between silica-coated rods in supersaturated silicic acid solutions at pH 7, with the compressive strength/= 10 dyn, and for 

Calculations using the same equations as for gypsum can be also carried out for sUica using the experimental data on the dependence of 1Tb o the supersaturation, a, and the time of contact, t. Such calculations indicate that the estimated parameters for the contact nucleus in a silica sol system (ft = 1.2 nm. A,. = 0.3 - 0.8 nm at a = 3.0-1.2) are similar to the parameters obtained for the contact of nucleus of gypsum and that the work of their formation, is significantly lower than the work of 

There are a number of peculiarities associated with the bridging in silica sols. Namely, the bridging probability depends on the polymerization rate of the silanol groups, as indicated by the dependence of Wb values on the pH. 

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The bridging of silica particles with the crystals of quartz, fluorite, periclase, bruscite, white asbestos, anthophyllite, and amorphous quartz (uncoated threads) was also studied. The specimens used in these studies were crystals with size 2x5x5 mm, which were mounted on the manipulator (Figure 1.28) and were cross-contacted with the silica-coated quartz thread. The area of contact was a plane with the dimensions 2x5 mm. The thread was positioned parallel to the short edge of the specimen. 

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