Islam Mohammed MahbubulRahman SaidurA. HepbasliMuhammad Afifi AmalinaAmalina, M. A.Mahbubul, I. M.Saidur, R.Hepbasli, A.2025-10-062016001793100017-93101879-218910.1016/j.ijheatmasstransfer.2015.10.0462-s2.0-84948402094https://www.scopus.com/inward/record.uri?eid=2-s2.0-84948402094&doi=10.1016%2Fj.ijheatmasstransfer.2015.10.046&partnerID=40&md5=adefd295b250c4c6c733fe5e92f62644https://gcris.yasar.edu.tr/handle/123456789/9812https://doi.org/10.1016/j.ijheatmasstransfer.2015.10.046Nanofluids are the mixtures of solid nanoparticles in liquid. Like most other fluids nanofluids could behave as yield stress fluids which require a certain amount of stress to flow. This flow characteristic may depend on the preparation of nanofluids. This paper investigates the effect of the ultrasonication periods (used during the nanofluid preparation) on the yield stress. The Al<inf>2</inf>O<inf>3</inf> nanoparticle with 0.5 vol.% of solid concentration was added to the distilled water using an ultrasonic horn and applied for different durations from 0 to 5 h. The microstructures of the nanoparticles were observed by transmission electron microscopy. The flow characteristics as the shear stresses at different shear rates (12.23-305.75 s-1) were observed for various temperatures from 10 to 50 °C. The yield stress the flow behavior index and the consistency index were studied using the Herschel-Bulkley rheological model. From this study non-Newtonian flow characteristic was observed. The yield stress decreased with increasing the fluid temperature. At the start of the ultrasonication the yield stress decreased rapidly, however for further ultrasonication it decreased slowly. © 2015 Elsevier B.V. All rights reserved.Englishinfo:eu-repo/semantics/closedAccessColloidal Dispersion, Nanofluid, Rheological Behavior, Ultrasonication Period, Yield Stress, High Resolution Transmission Electron Microscopy, Nanofluidics, Nanoparticles, Non Newtonian Flow, Shear Flow, Shear Stress, Transmission Electron Microscopy, Colloidal Dispersion, Experimental Investigations, Flow Charac-teristics, Nanofluids, Rheological Behaviors, Rheological Modeling, Solid Concentrations, Ultra-sonication, Yield StressHigh resolution transmission electron microscopy, Nanofluidics, Nanoparticles, Non Newtonian flow, Shear flow, Shear stress, Transmission electron microscopy, Colloidal dispersion, Experimental investigations, Flow charac-teristics, Nanofluids, Rheological behaviors, Rheological modeling, Solid concentrations, Ultra-sonication, Yield stressYield StressRheological BehaviorColloidal DispersionUltrasonication PeriodNanofluidArticle