Particle-stabilised foams: structure and aging

We show that aqueous foams stabilised by nanoparticles can be easily imaged using an X-ray laboratory source. We have used hydrophobically modified silica nanoparticles that confer to the foam a remarkable stability. The X-ray tomography observations were compared with the information obtained using a multiple light scattering technique. Both techniques confirm that provided the concentration of particles in bulk water is high enough, the bubble size evolves little with time. X-Ray tomography revealed the presence of two populations of bubbles, small bubbles which size tends to decrease with time and large bubbles which number tends to increase with time. This behaviour could arise from an arrested coarsening process. The results demonstrate the great potential of the two techniques and of their combination for foam studies.