Enhanced solar photo-thermal conversion performance by Fe3O4 decorated MWCNTs ferrofluid

In this work, water based ferrofluid with Fe3O4 nanoparticles (NPs) decorated multi-walled carbon nanotubes (MWCNTs) nanocomposite (NC) was investigated for solar photo-thermal energy conversion application. The NC was synthesized via the improved co-precipitation method. The thermal and optical properties of NC ferrofluid were also studied in the concentration range of 0.001–0.2 wt%. The results showed that Fe3O4 NPs connect on the outer walls of the MWCNTs uniformly and the saturation magnetization was found to be 31.26 emu/g. The solar photo-thermal energy conversion performance of the MWCNT/Fe3O4 ferrofluids decreases with the solar radiation time and improves with the concentration. Moreover, the extra magnetic field would further enhance the photo-thermal conversion performance due to absorbed heat is effectively transferred by the axially arranged MWCNTs with ultrahigh thermal conductivity. As a result, the solar photo-thermal conversion efficiency of ferrofluid is 58% at the concentration of 0.01 wt%, and it has 30% enhancement in comparison with the water. Another 6% enhancement would be obtained under the action of magnetic field.