Preparation And Photothermal Conversion Properties Of HO-BNNS/PANI Composite Nanofluids

Due to their superior thermal conductivity and optical properties,nanofluids have quickly become widely used materials in the field of heat transfer.In recent years,many researchers have developed new heat utilization systems through the development of composite nanofluidic systems,whose characteristics can be designed according to different requirements for fluid composition,and most composite nanofluids have better heat transfer and rheological properties due to the synergy between particles.In this paper,modified hydroxylated boron nitride（HO-BNNS）nanosheets were selected as the substrate,and polyaniline（PANI）was grown on HO-BNNS by redox reaction,which promoted the photothermal conversion effect of nanofluids through the thermal vibration effect of organic molecules.With HO-BNNS/PANI composite nanoparticles as the substrate,the metal oxides are loaded,and the non-radiation relaxation of the metal oxide structure and the synergy between the nanoparticles are used to further improve the stability and photothermal conversion effect of the composite nanofluids.The specific research is as follows:In order to improve the photothermal conversion ability of HO-BNNS/PANI composite nanofluids,a series of composite nanoparticles with different molar proportions were prepared by hydrothermal synthesis by loading the ZnO of CuO with excellent light absorption performance on the HO-BNNS/PANI composite nanoparticles.The composition of composite nanoparticles was determined using infrared spectroscopy（FT-IR）and X-ray powder diffraction（XRD）,and the morphology of composite nanoparticles was explored using scanning electron microscopy（SEM）.Then,the composite nanoparticles were uniformly dispersed in ethylene glycol-water（ethylene glycol content of 60%）base solution to prepare composite nanofluids with different mass concentrations.UV-Vis spectroscopy and sedimentation tests showed that when the molar ratio of HO-BNNS/PANI to CuO was1:0.75,when the molar ratio of HO-BNNS/PANI to ZnO was 1:1,the stability of the obtained composite nanofluids was the best,and its photothermal conversion effect increased with the increase of concentration,among which the maximum temperature rise of HO-BNNS/PANI/CuO composite nanofluids with a mass concentration of0.05 wt%could reach 87.02°C and a mass concentration of 0.05 wt%the maximum temperature rise of HO-BNNS/PANI/ZnO composite nanofluids can reach 85.51°C,which is 21.62°C higher than that of the base solution and 23.13°C higher than that of the ethylene glycol-water base liquid,which has a good photothermal conversion effect.The synergistic effect between binary oxide nanoparticles was used to further improve the light absorption performance and suspension stability of composite nanofluids,broaden the absorption spectrum of sunlight by composite nanofluids,and use hydrothermal method to make HO-BNNS/PANI/CuO/ZnO composite nanoparticles with different molar proportions.The composition of composite nanoparticles was determined by infrared spectroscopy（FT-IR）and X-ray powder diffraction（XRD）,and the SEM results showed that the overlapping composite of sheet CuO and rod-like ZnO were densely distributed and irregular on the surface of HO-BNNS/PANI.The results of UV-Vis spectroscopy and sedimentation experiments show that the composite nanofluids loaded with CuO and ZnO show better suspension stability than only one metal oxide,and the absorption spectrum of sunlight is further broadened by the composite two metal oxides.When the molar ratio of HO-BNNS/PANI to CuO/ZnO(R_Cu:R_Zn=3:1)was 1:1.25,the particle size of the composite nanoparticles was the smallest,and the suspension stability of the composite nanofluids prepared by them was the best.The photothermal conversion test results show that HO-BNNS/PANI/CuO/ZnO composite nanofluids have better photothermal conversion performance than composite nanofluids loaded with only one metal oxide,and the highest temperature rise of composite nanofluids with a mass concentration of 0.05 wt%can reach 89.10°C,which is 25.21°C higher than that of ethylene glycol-water base liquid,and the time is shorter,indicating that the synergy between nanoparticles promotes their stability in the base liquid and increases the photothermal conversion rate.It plays a good role in solar photothermal conversion.