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Movie 1. The time-lapse movie shows the solidification of a 23
wt%
solution of aqueous NH4Cl. The pulling speed is
initially 2 microns per second
(point b in figure 4) and the mushy layer is relatively uniform.
Eventually the
speed is decreased to 0.5 microns per second
(point a in figure 4) and several chimneys form. Plumes of buoyant
fluid can be seen emanating from the chimneys. The speed is then
increased back to 2 microns per second and the chimneys disappear. The
entire movie represents
1 hour and 10 minutes of real time. The width of the Hele-Shaw cell is
12 centimetres.
Movie 2. In this movie a 25 wt% NH4Cl solution is
being translated at 6 microns per second (point c in figure 4).
Secondary crystals can be seen in the supercooled melt above the mushy
layer. The entire time-lapse movie represents 1 hour
and 10 minutes of real time.
Movie 3. This movie illustrates the disappearance of the mushy
layer
during the solidification of a 21 wt% solution translated at 2 microns
per second (point d in figure 4). Although the initial concentration
was above the eutectic concentration of 19.7 wt% the growing solid is
the pure composite eutectic and no mushy layer appeared. The entire
time-lapse movie represents 2 hours and 20 minutes of real time.
Movie 4. This final movie shows a "breathing mode" which
occurred during the solidification of a 23 wt% solution. This system
has the same initial
concentration as in Movie 1, but the pulling speed is intermediate
between the speeds used there. Here the pulling speed is 1 micron per
second, which is near to the chimney-extinction boundary (figure 4),
and
the chimneys form and die out and then form again in phase. The
entire time-lapse movie represents 12 hours of real time.
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