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As a simulation of surface solidification of materials,quasi-two dimensional dendritic deposition ofammonium chloride(NH_4Cl)crystals from an aqueous solution film with free surface byvapourization was investigated by the in- situ observation technique.The depositing morphologiesof NH_4Cl crystals are faceted and of growth laws differing from the three-dimensional case.Underlow supersaturation,faceted dendrites formed,whereas the anisotropy in growth kinetics decreaseswith the increase of supersaturation.When vapourizing rate(supersaturation)is not very low,oscillations of growth rate.tip-radius and second arm spacing of the dendrites were observed.It issuggested that this dynamic phenomenon is attributed to the correlation between theconvection-transfer effect induced by the surface tension gradient of solution film.and the drivingforce for deposition.
As a simulation of surface solidification of materials, quasi-two dimensional dendritic deposition of ammonium chloride (NH4Cl) crystals from an aqueous solution film with free surface byvapourization was investigated by the in- situ observation technique. The depositing morphologies of NH4Cl crystals are faceted and of growth laws differing from the three-dimensional case. Underslow supersaturation, faceted dendrites formed, but the anisotropy in growth kinetics decreases with the increase of supersaturation. Temperature vapourizing rate (supersaturation) is not very low, oscillations of growth rate .tip-radius and second arm spacing of the dendrites were observed. It issuggested that this dynamic phenomenon is attributed to the correlation between the correlation between theconvection-transfer effect induced by the surface tension gradient of solution film.and the drivingforce for deposition.