Preparetion And Photothermal Properties Of Stably Dispersed Graphene Nanofluids

The direct absorption of sunlight and photothermal conversion based on uniformly dispersed nanofluids is an efficient solar-thermal harvesting method.At present,the research on photothermal conversion nanofluids mainly focuses on low temperature water-based nanofluids.In order to improve the efficiency and application range of solar photothermal utilization,it is urgent to develop medium and high temperature solar photothermal nanofluids.However,nanofluids generally have the problem of unstable dispersion.Nanoparticles are prone to agglomeration in fluids.This tendency of agglomeration is more obvious under medium and high temperature conditions,which seriously restricts the development of hightemperature solar-thermal conversion technology.In this paper,graphene was selected as a solar photothermal conversion nanomaterial,and two preparation methods of solar photothermal nanofluids stably dispersed at medium and high temperatures were explored.In this paper,the monolayer graphene oxide wetted by ethanol is used as the starting material,and its surface-rich interaction between oxygen-containing groups and ethylene glycol molecules is used to achieve uniform dispersion in ethylene glycol fluids.The graphene oxide is partially reduced by a onestep heating method to prepare reduced graphene oxide-ethylene glycol fluids,and the obtained fluids can be stably dispersed at 120 ° C for a long time.In order to further improve the use temperature of nanofluids,the crumpled graphene oxide was prepared by spray drying method,and the surface was modified with amino-terminated silicone oil to prepare graphene-dimethylsilicone oil nanofluids.Thanks to the small van der Waals attraction between the crumpled graphene oxide and silicone oil molecules and the steric hindrance effect of the surface-modifying molecules,the prepared fluids can be stably dispersed at 200 ° C for a long time.The two graphene nanofluids prepared in this paper have excellent solar absorption properties,high specific heat and low viscosity,and are very promising medium and high temperature solar collecting materials.At the same time,the stably dispersed graphene nanofluids studied in this paper are also expected to be applied in other fields,and promote the development of research on stably dispersed multi-functional nanofluids.