Concentrated Suspension Characteristics Of The Brownian Motion Of Particle Dispersion Liquid

The measurement about particle dynamics is a very interesting study field at present. Dynamic light scattering based on the Mie scattering theory, as a non-contact, non-destructive optical detection method, it has greatly promoted the research and development of nano-science with its unique advantages. Dynamic light scattering through measuring scattering light's small frequency shifts generated by Brownian motion particles, from which can obtain the translational diffusion coefficients and then acquire the hydrodynamic of particles.According to the deficiency about measurement lower limit of traditional measurement technique and the draw-backs of DLS in concentrated colloidal suspensions. We establish a low-coherence dynamic scattering device suit for dense suspension detection which based on low coherence interferometer, principle of the device is described in detail. And then the discussion about how to select the acquisition card, collection frequency, preprocessing signal, acquire scattered light spectrum, as well as the experimental distribution of the scattered light spectrum are given in detail based on the LabVIEW signal acquisition program.The diffusion properties of Brownian motion particles in concentrated colloidal suspensions are concerned. Based on the single scattering theory, consider the refractive index of suspensions varies with the volume fraction, the effective diffusion coefficients are obtained by analyze the single scattering spectra that measured using low-coherence dynamic light scattering. The effective coefficients for three different particles are investigated as a function of volume fraction. As a result, the diffusion properties of Brownian particles are influenced by hydrodynamics interactions and statistical structure factor of particles, the diffusive coefficient decreasing with the volume fraction increasing. In the volume fraction range from 0.01 to 0.2, the measured effective diffusive coefficients are good agreement with that of considering the Percus-Yevick and Cohen-de Schepper approximations. It is confirmed that the low- coherence dynamic light scattering technique can be used to measure the diffusion properties of Brownian particles with different volume fractions, thus provide a new method for particles detection in concentrated suspension.