[SMP44-P06] In situ hot/cool-stage AFM study on crystal growth of barite at 10 - 40°C
Keywords:Barite, Crystal Growth, AFM
The mechanism of crystal growth of barite was characterized by the spiral growth mechanism where rhombic growth spirals elongated along the  direction were formed and the two-dimensional (2D) nucleation mechanism in which circular sector-shaped two-dimensional (2D) nuclei were formed and developed. In addition, the adhesive growth mechanism was observed only at 10°C.
The kinetic laws of the crystal growth on the barite (001) surface differed among crystallographic directions and crystal growth mechanisms. The advance rates of the two steps of 2D nuclei were proportional to the SI. In contrast, the advance rates of the parallel steps with extremely short step spacing on growth spirals were proportional to SI2, indicating that the lateral growth rates of growth spirals were directly proportional to the step separations. This dependence of the advance rate of every step on the growth spirals on the step separations predicts that the growth rates along the  direction of the growth spirals were proportional to SI for higher supersaturations. The nucleation and growth rates of the 2D nuclei increased sharply for higher supersaturations using exponential functions. Only at 10°C, these rates changed to be proportional to SI for higher supersaturateions, indicating a change in main crystal growth mechanism from the 2D nucleation to the adhesive growth one. Two critical supersaturation points corresponding to the changes in main crystal growth mechanisms from the spiral growth, via 2D nucleation, to adhesive growth tended to decrease with decreasing of solution temperature.