Particle size distribution by space or time dependent extinction profiles obtained by analytical centrifugation concentrated systems
Torsten Detloff¹, Titus Sobisch¹, Dietmar Lerche¹, Powder Technology 174 (2007) 50-55..
Abstract: The particle size distribution of dispersions of fine particles were determined by an analytical photocentrifuge, which allows to measure space and time resolved extinction profiles (STEP-Technology) during the centrifugation of up to 12 samples. This type of centrifuge provides a powerful tool for the characterization and quality control of dispersions. While the variation of the light extinction curves caused by centrifugal segregation allows a qualitative control of dispersions, a rigorous formulation can give access to detailed quantitative characterization. The particle size distribution may be derived by two procedures: analysing the variation of the extinction at any point of the sample over centrifugation time or analyzing the extinction variation over the entire sample length at any time of the centrifugation. The advantage of the second analytical procedure is its potential to save time. Measurements of dispersions, with monomodal and broad particle size distributions in the nanometer and micrometer range show a good agreement between both analytical procedures. Also, analytical centrifugation has a great potential to measure dispersions without dilution. Therefore in addition two effects will be discussed, hindered settling and multiple scattering. Experimental results will be compared with those of other measurement techniques (SEM, PCS, Laser diffraction).
Key words: Particle size analysis • Sedimentation • Hindered sedimentation• analytical centrifugation • Extinction profiles
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