by Javen Weston, Deepika Venkataramani, Clint Aichele, Brian Grady, Jeffrey Harwell and Daniel Resasco.
Work was performed at: The University of Oklahoma and Oklahoma State University
When dispersed as binary mixtures in aqueous solution, certain metal oxide nanoparticles will heteroaggregate due to electrostatic interactions and cause the solution to form a yield stress gel at concentrations as low as 1.5 vol%.
The gels are highly tunable; the time required for gelation can be controlled by changing salt concentration, gel strength can be controlled by changing solution pH or nanoparticle concentration, and the pH range where gelation occurs can be altered by changing the metal oxide pairing (e.g. using a mixture of SiO2 & TiO2 vs. a mixture of SiO2 & Al2O3). This phenomenon has potential applications in 3-D printing, paints/coatings, consumer products, or in oil reservoir mobility control.
Figure: The effect of pH on gelation and a representative graph of viscosity vs shear stress for a 2.0 vol% silica/alumina gel