Preparation And Photothermal Conversion Properties Of Semiconductor@carbon Nanomaterials

There is ever increasing demand for renewable and clean energy because of the fossil energy crisis and environmental pollution.Solar thermal conversion is a technique which converts solar energy into heat by using photothermal conversion materials.The solar spectrum is a broad spectrum containing UV-visible-infrared light.It is critical to prepare broad-band absorption materials in order to reach high solar energy utilization efficiency.In this thesis,tin oxide antimony?ATO?@C and Fe₃O₄@C nanomaterials were prepared and their optical and photothermal conversion properties were studied.The ATO@C/DEG nanofluids were prepared by high temperature reflux method using glucose as carbon source and diethylene glycol?DEG?as solvent.The influences of glucose concentration,ATO concentration and reaction time on the morphology and dispersion of ATO@C nanostructures and the optical properties of ATO@C/DEG nanofluids were studied.The results show that the ATO@C/DEG nanofluids possess the best dispersibility and broad-band absorption effect when the concentration ratio of ATO and glucose is 5:3.The solar weighted absorption fraction?Am?of the ATO@C/DEG nanofluids increases with the increase of the nanofluids concentration under this ratio.The Am can reach a maximum value of 99.3% under 1 cm penetration distance and a concentration of 3 mg/m L.The solar utilization efficiency of the nanofluids can reach the highest value of 97.0% at this concentration.It demonstrated that most of the solar energy absorpted by the nanofluids has been converted into heat.Fe₃O₄@C nanoparticles were synthesized by a solvothermal method with ferrocene as iron source,H₂O₂ as oxidant and acetone as solvent.Fe₃O₄@C/EG nanofluids were prepared by dispersing Fe₃O₄@C nanoparticles into ethylene glycol?EG?.The influences of the amount of ferrocene and H₂O₂,the reaction time,the reaction temperature on the morphology of Fe₃O₄@C nanoparticles and the optical absorption and photothermal conversion properties of Fe₃O₄@C/EG nanofluids were studied.The results show that the Fe₃O₄@C/EG nanofluids possess regular morphology and broad-band absorption after treated at 180 oC for 72 h,when the amount of ferrocene and H₂O₂ are 0.15 g and 2.5 m L.The Am of Fe₃O₄@C/EG nanofluids increases with the increase of the nanofluids concentration under this reaction condition.The Am can reach a maximum value of 99.8% at 1 cm penetration distance and a concentration of 0.4 mg/m L.The solar utilization efficiency of nanofluids can reach the highest value of 83.5% at this concentration.Water evaporation experiments were conducted by loading ATO@C and Fe₃O₄@C nanomaterials onto filter paper as photothermal conversion materials.The influences of particle load on the absorbance,water evaporation rate and thermal efficiency were studied.The water evaporation rate and thermal efficiency increase with the increase of particle load under the irradiation of a xenon lamp(1 KW·m^-2).The maximum water evaporation rates were 1.39 kg·m^-2·h^-1 and 1.22 kg·m^-2·h^-1 for ATO@C and Fe₃O₄@C nanomaterials,0.96 kg·m^-2·h^-1 and 0.79 kg·m^-2·h^-1 higher than the evaporation rate of pure water.The maximum thermal efficiencies were 95.04% and 83.16% respectively,65.82% and 53.94% higher than the thermal efficiency of pure water.The ATO@C and Fe₃O₄@C nanomaterials show excellent properties in water evaporation and are promising in the applications of oil spill treatment and desalination.