Title: Effects of particles on spinodal decomposition: A Phase field study,
Abstract: In this thesis, we study the interplay of phase separation and wetting in
multicomponent systems. For this purpose, we have examined the phase separation
pattern of a binary mixture (AB) in presence of stationary spherical particles
(C) which prefers one of the components of the binary (say, A). Binary AB is
composed of critical composition(50:50) and off-critical compositions(60:40,
40:60). Particle sizes of 8 units and 16 units are used in the simulations. Two
types of particle loading are used, 5\% and 10\%. We have employed a ternary
form of Cahn-Hilliard equation to incorporate immobile fillers in our system.
To elucidate the effect of wetting on phase separation we have designed three
sets of $\chi_{ij}$ and $\kappa_{ij}$ to include the effects of neutral
preference, weak preference and strong preference of the particle for one of
the binary components. If the particles are preferentially wetted by one of the
components then early stage microstructures show transient concentric alternate
layers of preferred and non-preferred phases around the particles. When
particles are neutral to binary components then such a ring pattern does not
form. At late times, neutral preference between particles and binary components
yields a continuous morphology whereas preferential wetting produces isolated
domains of non-preferred phases dispersed in a continuous matrix of preferred
phase. For off-critical compositions, if minor component wets the particle then
a bicontinuous morphology results whereas if major component wets the network a
droplet morphology is seen. When majority component wets the particle, a
possibility of double phase separation is reported. In such alloys phase
separation starts near the particle surface and propagates to the bulk at
intermediate to late times forming spherical or nearly spherical droplets of
the minor component.