Síntese e caracterização de pentóxido de nióbio para aplicação como nanofluido em termossifões

Abstract

The energy situation in the world has been in constant change due several factors, such as the global population growth, climatic changes, supply chain problems and the global warming. For that reason, the search for more sustainable and efficient methods of energy generation is increasing, among these methods, the nanofluids and nanoparticles field stands out. The nanofluids has several applications, but it can be emphasized its use in thermosyphons, that are devices that use the latent heat of vaporization of work fluids as a mechanism for heat transfer. Using a nanofluid as a work fluid, the heat performance can be potentially increased. The Niobium (Nb) has been standing out due its good properties and characteristics such as high thermal and electrical conductivities and corrosion resistance, which allow it to be used in metallic structures, vehicle chassis, airplane turbine, among other applications. Therefore, this work aims to synthesize and characterize niobium pentoxide nanoparticles (Nb2O5) using the Sol-Gel Synthesis. Two similar synthesis methodologies were adopted, referred to as Case #1 and Case #2, in which doubledistilled water and aqueous ammonia were used, respectively, to achieve more versatile results and allow for parameter comparison. After the synthesis, the samples were calcined in a kiln for heat treatment. For precise analysis of the samples, advanced microscopy techniques were employed, such as Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), which allowed for the observation of particle surface and shape, and X-Ray Diffraction (XRD) testing was used to identify the present phases in the samples. For the sample synthesized with water, it was observed the formation of spherical agglomerates with different sizes, varying between 0.39 and 0.46µm, on the other hand, the sample synthesized with aqueous ammonia displayed a fragmented morphology. The morphological differences may be due the calcination temperature and synthesis methodology. The EDS analysis suggests that both Sol-Gel methods produced samples with high purity, containing only niobium and oxygen. The XRD analysis demonstrated that the uncalcined powder is amorphous, while the calcined powder at a temperature of 650°C demonstrated the formation of the T phase with orthorhombic structure (T-Nb2O5) in both samples. The results of the synthesis of niobium pentoxide through Sol-Gel Synthesis were satisfactory, demonstrating potential for subsequent use in the production of nanofluids for application in thermosyphons.