Energy transfer influence on superfast calcium carbonate synthesis: Using microwave heating, ultrasound cavitation and mechanical stirring

Mass and heat energy transfer are critical for crystallization, particularly for unstable polymorphs like calcium carbonate. This study explores how different energy transfer methods affect the rapid synthesis of calcium carbonate particles, emphasizing heat and mass transfer, nucleation site formation, and crystal growth. Methods investigated in this study include ultrasonic agitation, microwave-assisted magnetic stirring, magnetic stirring, and a combination of ultrasonic and magnetic stirring. Key synthesis criteria analyzed include mass yield, morphology, size, phase composition, and porosity. Vaterite is the predominant phase (> 85 %) formed under all methods at room temperature processing for 90 s. Ultrasound agitation produces uniformly distributed tiny bubbles, yielding smaller particles (0.8 μm) than magnetic stirring alone (2.5 μm). Combining ultrasound and magnetic stirring generates the most uniform, smallest elliptical particles (0.7 μm), while microwave-assisted stirring creates big particles (up to 7.8 μm) with broader size distribution and diverse shapes. The ultrasound agitation synthesis scalability is limited due to the ultrasound probe, when the volume beyond its working range, the ultrasound effects weaken. The study further examines phase stability in various solutions (e.g., water, physiological solution, PBS, and cell growth media), drug loading efficiency, and biocompatibility of small (0.7 μm) and big (2.5 μm) particles. The loading efficiency of particles for macromolecular drugs reaches up to 95 %, independent of particle size. Instability of particles in biological fluids facilitates controlled drug release, highlighting their potential as effective drug carriers. Furthermore, co-culturing with preosteoblastic cells demonstrates high cell viability, underscoring their suitability for drug delivery in cellular environments.