Using gradient
magnetic fields to suppress convection during crystal growth
Poodt PWG, Heijna MCR, Christianen PCM, van Enckevort WJP, de Grip WJ,
Tsukamoto K, Maan JC, Vlieg E
Cryst. Growth & Design 6 (2006) 2275-2280
Abstract:
Using in situ schlieren microscopy, we have studied the growth process
of nickel sulfate hexahydrate crystals in a gradient magnetic field
under conditions where convection is suppressed, to investigate whether
the features that occur here are the same as those that occur during
microgravity crystal growth. An expansion of the depletion zone with
decreasing effective gravity was observed. If convection is suppressed,
the depletion zone keeps expanding and the crystal growth rate
decreases significantly, reaching a constant value. Although there
remains some residual flow, it is very slow and does not affect the
depletion zone. We find that homogeneity of the effective gravity in
the milligravity range is sufficient to suppress convection. The
results show that crystal growth in gradient magnetic fields is a good
alternative for microgravity crystal growth in space.