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Title: Colloidal mixtures of spheres and plates
Author: Doshi, Nisha
ISNI:       0000 0004 2724 3600
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2011
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In this thesis we report on a system of colloidal plates and spheres developed to model the key particles found in paint and other industrial formulations. From theories of mixtures of particles of different shapes and sizes one would expect entropic phase sep- aration to occur at sufficiently high volume fractions, due to the gains in free volume. An aqueous system consisting of synthetic nano-gibbsite Al(OHh plates and alumina coated silica nano-spheres were sterically stabilized with a commercial stabiliser in wa- ter to create near-hard particle interactions. The stabilizer was chosen, by using in the first instance an NMR spin-spin relaxation technique. This gave a pseudo-adsorption isotherm. This technique was complemented with electrophoresis and elemental anal- ysis. The addition of the stabilizer to the suspension of plates modified the kinetics of the isotropic-nematic phase formation, with larger domains forming than in a surfac- tant free system. Colloidal plate-sphere mixtures were investigated using small-angle neutron scattering (SANS), optical microscopy (polarising and differential interference contrast). In SANS,' for dilute suspensions using contrast matching, the addition of colloidal plates to colloidal spheres showed an increase in density fluctuations of the spheres, which agreed well with theoretical predictions. The birefringence of the sys- tems was also observed in order to study the isotropic-nematic (I-N) transition. On adding spheres, the I-N transition occurs at a lower platelet concentration. The impact of the plate __ ~(Ls
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available