X-RAY PHASE ANALYSIS OF POWDERS NANOSILICA
Experiments were carried out to study the amorphous structure of SiO2 nanopowder samples obtained by vacuum sublimation of sols. The amorphous structure of silica samples obtained by water removal from sols distributed over the solid surface was determined by x-ray phase analysis. Compaction of SiO2 nanopowders at pressures typical for the experiments did not lead to a change in the amorphous structure of nanopowders and the appearance of mineral phases in the x-ray phase analysis spectra; calcination without compaction of nanopowders also did not lead to the formation of mineral phases and a significant change in the amorphous structure, which indicates the effect of contact of the surface of the nanopowder particles on the rate of crystallization at an elevated temperature. The main share of mineral phases arising after compaction and calcination of nanopowders obtained by vacuum sublimation of sols is represented by ?-cristobalite; the share of ?-cristobalite is 70-90 wt. %. The difference between the concentrations of mineral phases (Portland, calcium hydrates silicates) in the samples of nanomodified concrete (with the addition of Sol SiO2) compared with the control sample of concrete, which, in principle, makes it possible to study the mechanism of hydration of calcium silicates, which are part of the cement particles, and the effect on the speed and results of this process of SiO2 nanoparticles.