Coarsening of precipitation patterns in a moving reaction-diffusion front.
Precipitation patterns emerging in a two-dimensional moving front are investigated on the example of NaOH diffusing into a gel containing AlCl3 . The time evolution of the precipitate Al(OH)_{3} can be observed since the precipitate redissolves in the excess outer electrolyte NaOH and thus it exists only in a narrow optically accessible region of the reaction front. The patterns display self-similar coarsening with a characteristic length xi increasing with time as xi(t) approximately sqrt[t] . A theory based on the Cahn-Hilliard phase-separation dynamics, including redissolution, is shown to yield agreement with the experiments.
Volford
A
A
Department of Physics, University of Technology and Economics, 1521 Budapest, Hungary.
Lagzi
I
I
Molnár
F
F
Rácz
Z
Z