Download (4Mb) - Etheses - Saurashtra University

Chapter II Solution Growth….
2.23 Critical Theory of Homogeneous Crystal Nucleation
The classical homogeneous nucleation theory has been successfully
tested for the nucleation of liquid droplets from vapor and from liquid solutions
and for crystal formation in melts [104 - 108]. Experimentally observed
induction period can be used to evaluate the interfacial tension , energy of
formation ΔG and radius of the critical nuclei r. With the help of the following
theoretical consideration the basic relation of the equilibrium between solid
and its solution which links the solubility expressed as the chemical potential
to the particle size in the Thomson equation as suggested by Volmer [109].
Where, r =Chemical potential of nuclei of radius r
= Chemical potential of nuclei of infinite radius
=Volume per molecule in solid phase
=Interfacial tension of crystal
102
(2.12)
When the crystal attains a radius r, it will be in equilibrium with the
solution and under these conditions the chemical potential of two coexisting
phases are equal. While, equation (2.12) is written for the equilibrium between
macroscopic particles and a particle of radius r with their respective solutions,
the energy of formation of the nucleus of the new phase of radius r in
equilibrium with in solution is expressed as,
(2.13)