Perm Journal of Petroleum and Mining Engineering (Mar 2019)
The change of adhesion forces on the surface of the montmorillonite clay particles during high pressure processing
Abstract
For the formation of the technological properties of clays, various methods have been developed: thermal, chemical, ultraviolet, mechanical and others. However, the issues of changing the properties of clays and clay particles compacted with high pressures, are not well understood. Therefore, the aim of the work is to study the patterns of change in adhesion forces on the surface of particles of montmorillonite clay treated with stress pressure and shear. The adhesion force on the surface of clay particles and in the space between them was measured by atomic force microscopy on prepared samples of montmorillonite clay, compacted under different pressure (from 25 to 800 MPa). Experimental results showed that with increasing pressure on montmorillonite, adhesion forces change. So, with an increase in compaction pressure from 25 to 200 MPa, adhesion forces increase from 0.32 to 0.70 nN. When exposed to pressures above 200 MPa, adhesion forces decrease (to 0.40 nN at P = 800 MPa). To explain the dependence of the montmorillonite adhesion strength on the compaction pressure, the roughness of the samples and the amount of adsorbed water on their surface were studied. It is revealed that the roughness and thickness of the water film on the surface of the clay particle increases with increasing pressure. An increase in the thickness of the water film is probably due to the defects on the particle surface caused by pressure and shear. The presence of additional defects causes an increase in the charge density on the surface of the particles, increasing the number of adsorbed water molecules and the thickness of the water film, respectively.
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