Colloidal Particles In Suspension, Reunification Process Research

Nano material as the21st century most promising materials, caused the scientific community and the industry’s extensive interest, but because the size of nanoparticles is tiny, particle surface activity is extremely high, making it extremely easy aggregation, so it is significant to study the aggregation process of nanoparticles. At present, the main method used to study aggregation kinetics is dynamic light scattering method, but the traditional dynamic light scattering method applies only to dilute solution, for dense media, multiple scattering effects become dominant, single scattering theory no longer apply. We establish a low-coherence fiber optic dynamic scattering device suit for dense suspension detection which based on low coherence interferometer, principle of the device is described in detail.The path-length resolved amplitude power spectra of backscattering lights from different radius particles of colloidal suspensions were measured by use of low-coherence dynamic light scattering. The line-width of the measured amplitude power spectra were compared with the predict results calculated from the corresponding theories. The results show that in short path-length region, the measured line-widths are good agreement with that of single scattering after considering the influences of wall-drag effect close to the interface. For different radius particles, about5times of mean free path-length can be regarded as a single scattering region. The propagated path-length larger than225μm can be regarded as a diffusing region. It is demonstrated that the low-coherence dynamic light scattering can performance the path-length resolved amplitude power spectra measurement from single scattering to diffusive scattering regions for dense suspensions.The aggregation kinetics of particles in dense polystyrene latex suspensions is studied by low-coherence fiber optic dynamic light scattering. In certain single scattering area, aggregation kinetics, as quantified by the change in hydrodynamic particle size. Experimental results show that the aggregation rate is related to electrolyte and particle concentration. Aggregation rate is increased with the electrolyte concentration increases and all the dates are well fitted with exponential growth function, which is the characteristics of slow aggregation of colloidal suspensions. For different particle concentrations, variation of the mean aggregate size with time are measured. Experimental results show that as the particle concentration is increased, the rate of aggregation is more rapid. The dates show the exponential growth behavior of RLA. The experimental results can be explained by use of the DLVO theory.