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What happens when nanoparticles collide?

When there is a significant amount of particles, the Brownian motion brings them collide. The phenomenon of coagulation forms aggregates maintaining particles to each other by forces of attraction (Van der Waals). This leads to an instability of aerosol (composed of small particles), an overall increase in the size of aggregates associated with a decrease in the concentration of particles in the air.


Evolution of an aerosol type (50 nm) with a high concentration (108part/cm³).

Let us imagine an atmosphere of significant initial concentration, like 107 part.cm-3, with an average diameter of 50 nm.

How fast will the particles "coagulate“, form aggregates and agglomerates? The downward arrow noted on the opposite abacus expresses that this atmosphere is transformed into 4 mn (240 sec) in an aerosol of an average diameter 230 nm. The width of the smallest "bell-curve" centered on 230 nm indicates that no more particle smaller than 70 nm exists.

In high concentrations, the stability of nanoparticles is very fragile. It is very likely that aggregation and agglomeration phenomenon's occur.