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.
Keywords: additive-free synthesis; chain-like structures; nano-precipitated calcium carbonate.