Preparation And Property Of Ag,Graphene Nanofluids

Nanofluids are a new type of heat transfer fluids engineered by uniform and stable suspension of nanoparticles (metal or non-metallic nanopowder) into the traditional heat transfer medium (such as water, alcohol, oil at all). This is an innovative research of nanotechnology applied to energy projects in traditional areas. Nnaofluids have great potential application in many industrial sectors, including energy, chemical, automotive, construction, microelectronics, information and other fields, so, it is becoming the hot off the press of material, physical, chemical, heat transfer and many other fields.The main contents researched are as follows:1) Using Sodium citrate, sodium borohydride as reducing agent, Ag-H2O nanofluids were prepared by wet chemical method. Using dispersion method, the Ag- ethylene glycol (EG) nanofluids were successfully prepared by dispering chain-like Ag nanoparticles into EG. The Graphene-H2O nanofluids have been successfully prepared by useing natural flake graphite as raw materials. By Size distribution, Zeta potential, TEM, SEM, AFM, XRD and UV-Vis spectrometer, the influence of fabrication conditions on the structure and morphology of Ag nanopartickes and Graphene were characterized, the rheologic properties and thermal conductivity of the nanofluids were studied in depth.The results and conclusions are as followed:1) The Ag nanoparticles possessed sphere-like structure, the mean dimeter was 60nm, as the concentration of AgNO3 increasing, the Ag nanoparticles assembled into chain-like structure.2) Graphene was a single layer film with a thickness of about 0.344nm, slightly higher than the theoretical value of 0.335nm. The surfaces possessed varying degrees of fold. With the concentration of Graphene-H2O nanofluids increasing, the graphene films were overlapped and stacking phenomenon occursed.3) Ag-H2O and Ag-EG nanofluids showed Newtonian behavior. The Graphene-H2O nanofluids showed non-Newtonian behavior when the Concentrations greater than 1mg·ml-1, otherwise, it had a trend to change into Newtonian nanofluids.4) At the range of 20~60℃, when the volume fraction of Ag nanoparticles was 0.121%, the thermal conductivity of Ag-H2O nanofluid was increased by 8.9%~78.5% compared with the water. For the Ag-EG nanofluid, when the volume fraction increased from 0.03vol% to 0.12vol% at 25℃, its thermal conductivity arised from 1.6% to 7.0%, while, the same volume fraction of changing conditions at 55℃, its thermal conductivity was enhanced from 5.0% to 24.6%. Thermal conductivity of Graphene-H2O nanofluid decreased as the solid content increasesing, but boosted with the increasing of temperature. When the solid content of graphene reached to 0.2mg·ml-1, the thermal conductivity of Graphene-H2O nanofluid increased by 17.7%.Creative points:1) High volume fraction of the Ag-H2O nanofluids were successfully prepared by using a simple wet chemical method; Ag-EG nanofluids with different concentration were prepared by dispersed chain-like Ag nanoparticles into ethylene glycol.2) The Graphene-H2O nanofluids were synthesized by oxidation-reduction for the first time. The prepared Graphene was possessed of single-layer sheet structure, the height of single layer was 0.344nm.