Competition between intermolecular forces of adhesion and cohesion in the presence of graphene nanoparticles: Investigation of graphene nanosheets/ethylene glycol surface tension

摘要

Literature overview has affirmed that the presence of nanoparticles causes conflicting behaviors in surface tension, thereby, further studies are necessary to investigate the surface tension behavior. In this research, the base fluid surface tension behavior in the presence of graphene nanosheets is examined. The surface tension of the prepared samples at concentrations of 0-5 wt% was measured by SITA dynotester (SITA Process Solutions, Germany) at temperatures of 25-70 degrees C. Based on the results, incorporation of graphene nanosheets into ethylene glycol weakens the cohesion between the ethylene glycol (EG) molecules. In other words, a part of the cohesive is replaced by the van der Waals force correspond to the nanoparticles presence as well as adhesive force between the EG and nanoparticle molecules. However, the effects of the increase in adhesive force were not able to counteract the cohesive force reduction efficacy, hence the presence of nanoparticles reduced the surface tension up to 13.9%. As the temperature raised from 25 to 70 degrees C, the base fluid surface tension diminished by 8.3%, while for nanofluid at 5 wt%, this figure was 3.86%. Therefore, by using nanoparticles, the sensitivity of surface tension to temperature diminished. (C) 2020 Elsevier B.V. All rights reserved.