Effect of additives on the morphology of calcium sulfate hemihydrate: Experimental and molecular dynamics simulation studies

• Additives were used to tune the morphology of calcium sulfate hemihydrate.
• The axial growth of the crystal was significantly inhibited by the additives.
• The effects of additives were investigated by molecular dynamics simulation.
• The sequence was obtained: Eb(0 0 2) > Eb(1 1 0) > Eb(2 0 0) > Eb(1 −1 0).
• The results provided a rational explanation to the experimental observations.

The effects of sodium dodecyl sulfonate (SDS) and sodium dodecyl benzene sulfonate (SDBS) on the morphology of calcium sulfate hemihydrate (HH) were studied by experiment and molecular dynamics (MD) simulation. It was observed that the additives significantly inhibited the axial growth of HH crystals. The binding energies (Eb) between the additives above and the (0 0 2) face were much higher than the ones of other faces. The following sequence was obtained: Eb(0 0 2) > Eb(1 1 0) > Eb(2 0 0) > Eb(1 −1 0), which could provide a rational interpretation to the experimental results. In addition to the additives above, the effects of other linear alkyl sulfonates (LAS) and alkyl benzene sulfonates (LABS) on the (0 0 2) face were also investigated and the binding energies were increasing with the number of carbon atoms increase. The results obtained from this study should be helpful to the performance evaluation and selection of the morphology modifiers for HH crystals.