Contribution à l'étude de la biréfringence d'écoulement à la transition PDF Download

Author: Jean-Paul Decruppe
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Languages : en
Pages : 448

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Book Description
The optical anisotropy gained by numerous solutions as well as by pure liquids when submitted to the action of an orientating field, is capable of bringing valuable pieces of information on the structure of this field as well as on the physical properties of the particles in solutions. The study of the optical properties arising from this anisotropy only requires the use of a lenearly polarized beam of light on which the medium is going to leave this own characteristics by changing the state of polarization of the light. The flow is created in a conventional Couette cell. It is well known that, in this type of geometry, the hydrodynamical flow undergoes several transistions leading at first to more and more complicated periodical flows, and then, to the turbulence as the angular velocity of the inner rotating cylinder is increased. The aim of this work is to study the behaviour of the properties induced by the flow at the first transition, to work out the theoretical laws controlling this properties and to see in which extend, we can deduce the intrinsec characteristics of the particles. The variation of the extinction angle and of the birefringence intensity is studied at the middle point of the annular gap as a function of the shearing gradient and, for different values of the gradient, as function of the position in the gap. The comparison between the experimental and theoretical curves shows a good agreement in the case of flattened particles (bentonite) but less convincing results for rodlike particles (V.M.T.)