Particles in a dispersion may stick together and form larger aggregates, which will eventually settle out due to gravity. If the particles are stable, they will not agglomerate at a significant rate. The total aggregate rate, the chance of accidents, and cohesiveness are all determined by the frequency. The stability of a particle in solution is determined by the sum of van der Waals forces. As particles approach one other in Brownian motion, they feel attraction and electrical double layer repulsive forces. The two particles will collide if the attractive force exceeds the repulsive force, and the suspension will become unstable. The suspensions will remain stable if the particles have a sufficiently high repulsion. For nanofluids to remain stable, repulsive forces between particles must be dominant. The primary mechanisms that influence colloidal stability are divided into two categories depending on the types of repulsion: steric and electrostatic (charge) repulsion. Polymers are always present in the suspension system for steric stabilization, and they adsorb onto the particle surface, resulting in an additional steric repulsive force.
One or more of the following techniques will create surface charge for electrostatic stabilization:
(1): Ion preferential adsorption
(2):Surface charged species dissociation
(3):Isomorphic ion substitution
(4):Buildup or depletion of electrons at the surface
(5):Physical adsorption of charged species onto the surface
thank you Mr Muhammad Talha on this information
Allah bless you