title: Temperature-induced gelation in dilute nanofluids.
abstract: We report a temperature-induced gelation in dilute nanofluids containing surfactant capped iron oxide and alumina particles of average diameter ~10 nm. We observe a dramatic enhancement in the elastic modulus, viscous modulus, and viscosity, by 3-6 orders of magnitude for a volume fraction (φ) less than 0.035, above a critical shear rate ( ̇γ(c)) and temperature (T(c)). The T(c) follows a weak power law scaling with φ as T(c) ~ φ(β), where the scaling exponent β is found to be -0.24. The observed gel-like transition at elevated temperature is attributed to strong van der Waals attractions on the kT energy scale due to poor solvent conditions, which is reminiscent of the phase behavior reported in polymer-coated colloids.
authors.affiliation: SMARTS, NDE Division, Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, India.
authors.forename: Vijutha
authors.initials: V
authors.lastname: Sunny
authors.forename: T
authors.initials: T
authors.lastname: Muthukumaran
authors.forename: John
authors.initials: J
authors.lastname: Philip
mesh_terms: D003102:Colloids / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry; D005782:Gels; D053758:Nanoparticles / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D014783:Viscosity
chemical_list: D003102:Colloids; D005290:Ferric Compounds; D005782:Gels; D011108:Polymers; D013501:Surface-Active Agents; C000499:ferric oxide