Determination of Particle Size Distributions based onSpace and Time Resolved Extinction Profiles in Centrifugal Field

摘要

The particle size distributions of dispersions of fine particles were determined by an analyticalphotocentrifuge, which allows to measure extinction profiles (STEP-Technology) during thecentrifugation of up to 12 samples simultaneously. This type of centrifuge provides a powerful toolfor the characterization and quality control of dispersions. While the variation of the lightextinction curves caused by centrifugal segregation allows a qualitative description, a rigorousformulation can give access to detailed quantitative characterization. The particle size distributionmay be derived by two procedures: analyzing the variation of the extinction at any point of thesample over centrifugation time or analyzing the extinction variation over the entire sample lengthat any time of centrifugation. The advantage of the second analytical procedure is its potential tosave time. Measurements of dispersions, with monomodal, multimodal and broad particle sizedistributions in the nanometer and micrometer range show a good agreement between bothanalytical procedures. Also, analytical centrifugation has a great potential to measure dispersionswithout dilution. Therefore in addition two effects will be discussed, hindered settling and multiplescattering. Experimental results from concentrated suspensions and emulsions show theapplicability of this new measurement principle. Results will be compared with those of othermeasurement techniques (SEM, PCS, Laser diffraction).