Abstract:

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Metal oxides are a promising class of materials for solar thermal applications due to their excellent light absorption, thermal stability, and ease of synthesis. When produced in nano size, metal oxides have been recognized as suitable materials for improving thermo-physical properties of working fluids or coatings in solar thermal applications. In this research, earth metal oxides of Aluminium oxide (Al2O3), Nickel oxide (NiO) and Antimony oxide (Sb2O3) nanoparticles were synthesized using suitable precursors which include Aluminium nitrate, Al(NO3)3.9H2O, Nickel Chloride, NiCl2.6H2O, Antimony chloride (SbCl3) and Urea, CO(NH2)2 respectively, in de-ionized water as based fluid by Hydrothermal method. The synthesized Al2O3 nanoparticles was obtained by calcination of the intermediate product, Aluminium hydroxide, (AlOOH) precipitate from the hydrothermal process at 1000ᵒC for 4 hours. NiO nanoparticles was obtained by annealing Nickel hydroxide, Ni(OH) of the synthesized product at 400ᵒC for 3 hours and Sb2O3 nanoparticles was obtained by heating Antimony oxychloride, (SbOCl) from the hydrothermal process at 60ᵒC for 4 hours. Their crystal structure and surface morphology were characterized by employing X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) techniques to ascertain their purity. From the XRD results of the analysis of Al2O3 nanoparticles showed the main diffraction peaks at 2θ = 32.783ᵒ, 67.418ᵒ, 36.684ᵒ, 31.207ᵒ, 32.783ᵒ and 44.796ᵒ which is in agreement with the International center for Diffraction Data (ICDD) standard pattern Ref. card no. 98-003-7392 and monoclinic in nature as seen from the crystallographic parameter, with crystallite size evaluated as 14.2nm (Debye Scherrer method). For NiO nanoparticles, the results of the analysis described the main diffraction peaks at 2θ = 43.254ᵒ, 37.227ᵒ, 62.829ᵒ, 75.352ᵒ and 79.341ᵒ respectively, this is also in agreement with the International center for Diffraction Data (ICDD) standard pattern Ref. card no. 98-000-8170 and cubic in nature as describe by the crystallographic parameter, its crystallite size was calculated as 9.5nm (Debye Scherrer method). The XRD results of the analysis of Sb2O3 nanoparticles indicate the main diffraction peaks at 2θ = 27.718ᵒ, 46.053ᵒ, 54.603ᵒ, and 32.112ᵒ respectively which is equally in agreement with the International center for Diffraction Data (ICDD) standard pattern Ref. card no. 98-001-7507 and cubic in nature as obtained from the crystallographic parameter, with crystallite size determined as 32.22nm (Debye Scherrer method). The FESEM surface morphology for the samples revealed the distribution peaks as unimodal, having one main peak suggesting all samples are relatively uniform in size having a diameter of 64.2nm, 50.1nm, and 8.8nm for Al2O3, NiO and Sb2O3 respectively. The Crystal structure, crystallite size and surface morphology give rise to greater surface area and can greatly influence heat capacity and absorption by nanoparticles in a based fluid, hence the results shows that the synthesized nanoparticles can offer high thermal conductivity and excellent thermal stability, making them promising candidates for efficient solar energy absorption suitable for solar thermal application.

Keyward(s): Earth Metal Oxides, Nanoparticles, Solar energy, Solar thermal collector

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