CONICET | Buscador de Institutos y Recursos Humanos

When a coherent beam coming from a laser illuminates a rough object, a typical granular interference pattern named speckle is observed1. Besides, a laser light scattered from diffuse objects produces a similar pattern. If this surface does not remain rigid, but it presents some type of local movement, then the intensity pattern evolves in time. This phenomenon, well known as dynamic speckle, is characteristic of biological samples2. This behavior can also be observed in non-biological industrial processes, including the drying of paint, corrosion and heat exchange. This activity takes place when the sample changes its properties due to movement of the scattering centers, changes in the optical path due to variations of refractive index, configuration changes or combination of these situations3. The study of the temporary evolution of the speckle patterns may provide an interesting tool to characterize the parameters involved in these processes. The present work addresses the implementation of dynamic laser speckle technique to the hydro-adsorption analysis of Silice, alumina and natural alumina-silicates (kaolinite, zeolites, original bentonite clay and chemically modified clays such as PILCs "pillared clays" and PCHs "porous clays heterostructured") with different chemical composition, surface area and pore volume. Experimental results show the temporal evolution of the materials speckle patterns during the process of water adsorption. Studies with commercial silica (SiO2) with different textural properties show the correlation of the speckle activity with the hydro-adsorption process 4. Also we found that it is possible to correlate the dynamic speckle stabilization time of each species with the Si/Al ratio and the Si-OH group availability. This analysis can be considered as a potential new method to study different porous materials of interest such as absorbents or catalysts supports.