Characterization and stabilization of nano-metakaolin colloidal suspensions

• Published in: Powder technology Vol. 383; pp. 43 - 55
• Main Authors: Malta, Juliana O., Oliveira, Lucas V.S., Ueki, Marcelo M., Barreto, Ledjane S.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01-05-2021; Elsevier BV
• Subjects: Charge distribution; Colloidal suspensions; Colloids; Dispersants; Electric potential; Isoelectric points; Metakaolin; Nano-metakaolin; Nanoparticles; Potentiometric titration; Rheological properties; Rheology; Stability; Surface charge; Titration; Zeta potential; Dispersants; Colloidal suspensions; Nano-metakaolin; Stability
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2021.01.024

Nanometric powders bear significant problems in the efficiency of dispersion. The ideal situation would be to ensure full nanoparticle separation in suspensions or composites matrix, which is hard to achieve due to the high reactivity and aggregation. This study evaluates the conditions to stabilize nano-metakaolin (NMK) in water suspension by analyzing the influence of solute concentration, pH, type and content of dispersants. Potentiometric titration curves, zeta potential and average particle size measurements were performed, along with rheological measurements, at different times: 0 h, 3 h, 6 h and 24 h. NMK particles showed the same tendency of surface charge distribution, regardless of solute concentration. The dispersed NMK particles presented two isoelectric points, attributed to the multiple arrangements they form when in suspension. Polycarboxylate (PC) was the dispersant that provided greater dispersion stability. Regarding the rheological and zeta potential measurements, the suspensions presented stability up to 24 h.
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•The use of suspensions minimizes the adverse effects of handling ultrafine powders.•Particle size, surface charges, and pH are critical factors to stabilize suspension.•The stability of suspensions was analyzed for zeta potential and rheology over time.•Polycarboxylate promoted the greatest stability of nano-metakaolin suspensions.