Calcium sulfate hemihydrate powders with a controlled morphology for use as bone cement

Calcium sulfate hemihydrate (CSH) powders were synthesized for use as bone cement by heat treating calcium sulfate dihydrate (CSD) powders in boiling CaCl₂ solutions with various CaCl₂ concentrations, ranging from 23.5 to 35.5 wt%, in order to control their morphology. All of the prepared CSH powders showed X-ray diffraction peaks corresponding to the CSH structure without any secondary phases, implying complete conversion from the CSD phase to the CSH phase. It was also observed that the concentration of CaCl₂ significantly affected the morphology of the CSH powder that was synthesized. In other words, as the CaCl₂ concentration was decreased from 35.5 to 23.5 wt%, the morphology notably changed from long-and-slim hexagonal rods with an aspect ratio of 5.5 to fat-and-short hexagonal columns with an aspect ratio of 1.4. This reduction in the aspect ratio led to a significant improvement in the compressive strength of the CSD cement prepared by mixing the CSH powders with water.