Enhancement of SiO₂ based nanofluid stability and thermophysical properties using surface active ionic liquids

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Nanotechnology

Background:

• Achieving long-term colloidal stability in silica (SiO2) nanofluids is crucial for their practical application.
• Conventional surfactants often provide limited stability (less than 20 days).

Purpose of the Study:

• To investigate the stabilizing effects of specific surface-active ionic liquids (SAILs) on aqueous SiO2 nanoparticle dispersions.
• To evaluate the performance of (2-hydroxyethyl)ammonium oleate (HEA-Ole), bis(2-hydroxyethyl)ammonium oleate (BHEA-Ole), and tris(2-hydroxyethyl)ammonium oleate (THEA-Ole) in enhancing SiO2 stability.

Main Methods:

• Stability assessment via excess molar volume, viscosity, density, dynamic light scattering (DLS), zeta potential, surface tension, and visual observation over 60 days.
• Modeling of viscosity using Eyring-mNRF and Eyring-NRTL equations.
• Fitting density data with Redlich-Kister, polynomial, Ott, and PC-SAFT models.
• Analysis of interactions using COSMO results and PC-SAFT for average relative deviation (ARD%).

Main Results:

• Tris(2-hydroxyethyl)ammonium oleate (THEA-Ole) demonstrated superior stabilization of SiO2 nanoparticles, especially above the critical micelle concentration (CMC).
• THEA-Ole resulted in minimal sedimentation, optimal dispersity (via DLS), and high zeta potential.
• Viscosity, excess molar volume, and surface tension measurements indicated stable trends for THEA-Ole nanofluids.
• PC-SAFT modeling confirmed strong SiO2 interactions with THEA-Ole, showing the lowest ARD%.

Conclusions:

• THEA-Ole provides exceptional colloidal stability for SiO2 nanofluids, exceeding 60 days.
• This SAIL significantly outperforms conventional surfactants, addressing limitations in nanofluid dispersion for extended applications.
• The findings pave the way for enhanced utilization of SiO2 nanofluids in various technological fields.