Synthesis of Nanoscale Precipitated Calcium Carbonate: Additive-Free Precipitation and Chain-like Structure Evolution

Nanoscale precipitated calcium carbonate (NPCC) is a versatile functional material whose performance is highly governed by particle size, morphology, and dispersion state. Conventional synthesis methods often rely on complex additives or multi-step processing, thereby impeding scalability and precise morphological regulation. Herein, we present a simple and additive-free route for the tunable synthesis of NPCC via the direct reaction of an aqueous Na2CO3 solution with a Ca(OH)2 suspension under ambient conditions. A systematic investigation was conducted to elucidate the influence of key synthetic parameters—namely, reactant concentration, temperature, injection rate, stirring speed, and aging duration—on the resultant particle characteristics. Under optimal conditions, cubic NPCC with a mean particle size of approximately 90 nm, distinct crystalline features, and good dispersion was successfully obtained. Furthermore, integrated analysis employing time-resolved pH and conductivity monitoring, electron microscopy, and diffraction techniques revealed a growth trajectory distinct from the classical crystallization pathway of CaCO3. This observed behavior suggests a mechanistic association with non-classical crystallization. These findings not only furnish a practical and environmentally benign strategy for the production of high-quality NPCC but also offer fundamental insights into the crystallization mechanisms of calcium carbonate, with broader implications for the rational design of advanced inorganic nanomaterials.