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Rheooptical determination of aspect ratio and polydispersity of nonspherical particles
Author(s) -
Vermant J.,
Yang H.,
Fuller G. G.
Publication year - 2001
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690470405
Subject(s) - dispersity , aspect ratio (aeronautics) , isotropy , axial ratio , mechanics , materials science , scattering , rheology , rotational symmetry , orientation (vector space) , ellipsoid , particle (ecology) , shear (geology) , particle size , shear flow , polarization (electrochemistry) , diameter ratio , optics , classical mechanics , physics , chemistry , geometry , mathematics , composite material , circular polarization , polymer chemistry , oceanography , astronomy , geology , microstrip
A rheooptical method proposed rapidly determines the aspect ratio and polydispersity of small axisymmetric, nonspherical particles. The time evolution of the average orientation angle of optically isotropic, nonabsorbing particles upon inception of a shear flow was monitored by a polarization modulation method by using dilute suspensions of the particles. Since the orientation angle is a geometric property of the particles, no arbitrary assumptions on the scattering mechanism had to be made to analyze the data. The period of the damped oscillatory response of the orientation angle is related to the average aspect ratio. In the limit of strong flows the damping only depends on dispersion in particle shape. An analytical expression to relate the polydispersity of the equivalent hydrodynamic aspect ratio to the damping function is presented, as well as the applicability of the technique by studying the hydrodynamic aspect ratio and associated polydispersity in a sample containing ellipsoidal hematite particles.