3:00 PM - 3:15 PM
[MIS07-11] Aggregation of silica colloids: From suspension to rock
Keywords:silica colloid, aggregation, packing
We newly carried out the aggregation experiments using colloidal materials focusing on (1) natural silica colloid in the geothermal system and (2) synthetic silica in the various pore spaces. Natural colloidal silica is produced in the circulation system at the geothermal power plant and accumulated as silica scale. Kinetic process of this accumulation was measured by ex-situ interferometry using steel and chalcedony plates to be 0.003 and 0.03 nm/s, respectively. TEM and FESEM observations of these silica aggregates revealed that silica particle has core (<10 nm) and mantling structure (100-1000 nm), and their growth may had continued after aggregation like sintering. Resultant silica scale is porous and lower density (~ 1.55 g/cm3) than homogeneous a-SiO2 (2.196) but hard. Since the porosity of close-packing of equal spheres is 0.260 (packing density, 0.740), porosity of obtained silica scale, 0.296 may reflect that colloidal aggregation of silica scale is randomly formed. Synthetic colloidal silica was used for solidifying experiment with various sandy materials and alkalis. These different experiments suggest that the aggregation of silica particles requires condensation space (supersaturation) and overgrowth (volume increase). We evaluate the observation results of aggregation structures of various colloids in nano-scale. This knowledge is important to consider the solidification process of geomaterials as well as to control the colloidal particles.
Satoh, H., Kimura, Y., and Furukawa, E. (2018) Direct transmission electron microscopy visualization of the cement reaction by colloidal aggregation of fumed silica. Industrial & Engineering Chemistry Research, 57, 79-83.