title: Characterization of electrokinetic properties of nanofluids.
abstract: The effects of pH value, surfactant, and electrolyte concentration on zeta potential, particle agglomeration, and thermal conductivity of nanofluids are investigated. The zeta potential of TiO2 (15 nm) nanoparticles in deionized water of different pH values was measured and the iso-electric point was found to be between 4.9 and 5.2. Addition of surfactant in the base fluid increases the zeta potential and thus increases the effective thermal conductivity of nanofluids. The results show that the higher the electrolyte concentration, the smaller the particle zeta potential, which results in increased agglomeration of particles. The enhanced thermal conductivity of TiO2/deionized water-based nanofluids was found to decrease with increasing pH value or electrolyte concentration. At 0.2 volume percentage of TiO2 nanoparticles, the decrease of thermal conductivity of nanofluids was within 2% when the pH value or electrolyte concentration was increased from 3.4 to 9 or 0.01 mM to 10 mM, respectively. The hydrodynamic diameter of agglomerated nanoparticles in base fluid was also measured and found to increase with increasing electrolyte concentration.
authors.affiliation: School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Republic of Singapore.
authors.forename: S M Sohel
authors.initials: SM
authors.lastname: Murshed
authors.forename: Kai Choong
authors.initials: KC
authors.lastname: Leong
authors.forename: Chun
authors.initials: C
authors.lastname: Yang
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D004553:Electric Conductivity; D004563:Electrochemistry / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D044085:Microfluidics / Q000379:methods; D008956:Models, Chemical; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D012996:Solutions; D013499:Surface Properties; D013814:Thermal Conductivity; D014025:Titanium / Q000737:chemistry*
chemical_list: D003102:Colloids; D046911:Macromolecular Substances; D012996:Solutions; C009495:titanium dioxide; D014025:Titanium