Calcium carbonate chain-like nanoparticles: Synthesis, structural characterization, and dewaterability

Synthesis of Tunable-Aspect-Ratio Calcite Nanoparticles via Mg2+ Doping

“…Soon after the carbonation reactions began (0–10 min), the pH temporarily decreased and subsequently recovered in case of all the reactions. This can be attributed to the initial suppression of the dissolution rate of the Ca­(OH) 2 particles (Figure S1a) because of ACC generation from their surfaces and its consequent recovery owing to ACC disappearance, as previously reported. , Short-time ACC nucleation is a common phenomenon during the initial crystallization stages for all three anhydrous calcium carbonate polymorphs. − After ∼50 min of carbonation, the pH curves rapidly decreased when the pH became ∼12.6, which corresponded to the disappearance of the Ca­(OH) 2 colloidal particles from the aqueous slurry. This also corresponded to the conclusion of the carbonation process of the Ca­(OH) 2 aqueous slurry and the beginning of the carbonation process of the Ca­(OH) 2 aqueous solution.…”

“…Spheroidal nanoparticles (aspect ratio: ∼1) were observed in the pristine calcite sample, whereas high aspect ratio chainlike nanoparticles were observed in all the Mg 2+ -doped samples. Anisotropic 1D nanoparticles were successfully fabricated by adding Mg­(OH) 2 to lime milk before the carbonation reaction without the requirement of complex procedures, which were previously proposed by our group (i.e., the repeated addition of lime milk during the carbonation reaction) . The average aspect ratio, length, and width of the samples, determined by TEM image analysis, are presented in Table , confirming that the nanoparticle length and breadth increased and decreased, respectively, with the Mg 2+ -doping amount; thus, the average aspect ratio also increased.…”

“…The number-based aspect-ratio distributions of the Mg 2+ -doped chainlike nanoparticles are presented in Figure S3. The average aspect ratios of the nanoparticles doped with 5000 and 10 000 ppm of Mg 2+ (i.e., 4.9 and 6.1, respectively) were larger than that of the nanoparticles fabricated using the aforementioned lime milk addition method (i.e., 4.3) …”

“…The evolution of particle morphology during the synthesis of calcite nanoparticles has been previously investigated in detail, and the presence of chainlike calcite nanoparticles exhibiting high aspect ratios has been confirmed as an intermediate before the final formation of the spheroidal particles. Recently, a technique has been developed to synthesize chainlike calcite nanoparticles as final products via the repeated addition of small amounts of lime milk during synthesis (lime milk addition method) . However, even though ensuring control over particle morphology is important in the pigment-extender industry, the aspect ratio of the resulting particles cannot be easily tuned via this technique.…”

Fracture Strength Evaluation of Agglomerates of Fatty Acid-Coated CaCO3 Nanoparticles by Nano-Indentation

“…Synthesized calcite nanoparticles [16,17] are relatively uniformly-shaped rhombohedral particles (aspect ratio~1) with narrow particle size distributions, so the effects of the primary particle morphology could be minimized in this study. It is reported that agglomerates of calcite nanoparticles have relatively spherical shapes [18]. CaCO 3 nanoparticles are widely used as filler materials in several industries, including rubber, plastics, sealants, paints, printing inks, and paper [19].…”