Controllable synthesis of snowflake-like α-calcium sulfate hemihydrate microstructures using Na2EDTA as morphology modifier

Abstract

In this work, snowflake-like α-CaSO₄·0.5H₂O (α-CSH) hierarchical architectures were successfully synthesized by a facile one-pot method in an ethylene glycol-water system using Na₂EDTA as a crystal morphology modifier. Characterization techniques including X-ray diffraction (XRD), thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) confirmed the progressive morphological evolution of α-CSH from rods to snowflake-like structures ultimately to hexagonal plates with increased Na₂EDTA concentrations. The results revealed that Na₂EDTA concentration played a critical role in directing the crystallization and self-assembly of α-CSH, and a mechanism is proposed where Na₂EDTA modulated crystal orientation through preferential adsorption and regulated the driving forces between ion-mediated crystallization and particle-mediated assembly. This work puts forward a simple yet effective strategy for facilely regulating the morphology of α-CSH microstructures, which could potentially expand their applications across diverse fields such as composites, construction, biomedicine, and drug delivery.