Abstract: The effects of two dispersant, polyacrylic acid (PAA) and 2-phosphonobutane-1,2, 4-tricarboxylic acid (PBTCA), on the calcium carbonate microstructure were studied
by using SEM and AFM. XRD analysis demonstrates that the content of vaterite increases with the increase in inhibition effects. The metastable crystal forms
of vaterite and aragonite are stabilized kinetically in the presence of dispersants. The fractal analysis result shows that the fractal dimension is higher in the presence
of dispersants. The better the inhibition effect, the higher the fractal dimension. The step morphology observed by AFM images shows that the step space on the CaCO₃
surface increases in the presence of dispersants. Moreover, with the increase of inhibition effect, both the step space and fractal dimension increase. Step bunching
was found on the CaCO₃ crystal surfaces by AFM and discussed.

Key words: dispersant, calcium carbonate, fractal, AFM