  Formation mechanism of speed-dependent ice bandings in freezing colloidal
suspensions, of significance in frost heaving and materials science, remains a
mystery. With quantitative experiments, we propose a possible mechanism of
speed-dependent ice bandings by focusing on the particle packing density and
dynamic interface undercooling. The particle packing density ahead of the
freezing interface decreases with increasing pulling speeds, attributed to the
speed-dependent packing of particles. Through affecting the curvature
undercooling of pore ices, the speed-dependent packing of particles can be used
to explain speed-dependent thicknesses of ice bandings. The dynamic interface
undercooling was obtained to explore curvature undercooling of pore ices and
quantitative details of transient interface positions, speeds and undercooling
were given. All the evidences imply that the speed-dependent particle packing
and dynamic interface undercooling are responsible for speed-dependent ice
bandings.
