Effect of Fe3+ Doping in the Photocatalytic Properties of BaSnO3 Perovskite

CT-INFRA/FINEP/MCTICCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)In the last ten years, stannates with perovskite structure have been tested as photocatalysts. In spite of the ability of perovskite materials to accommodate different cations in its structure, evaluation of doped stannates is not a common task in the photocatalysis area. In this work, Fe3+ doped BaSnO3 was synthesized by the modified Pechini method, with calcination between 300 and 800 degrees C/4 h. The powder precursor was characterized by thermogravimetry after partial elimination of carbon. Characterization after the second calcination step was done by X-ray diffraction, Raman spectroscopy and UV-visible spectroscopy. Materials were tested in the photocatalytic discoloration of the Remazol Golden Yellow azo dye under UVC irradiation. Higher photocatalytic efficiency was observed under acid media. As no meaningful adsorption was observed at this condition we believe that an indirect mechanism prevails. Fe3+ doping decreased the band gap and favored the photocatalytic reaction, which may be assigned to the formation of intermediate levels inside the band gap

Magnetic and electrochemical properties of nickel oxide microstructures prepared by hydrothermal method

Abstract Nickel oxide microstructures were succesfully synthesized by hydrothermal method. The structure, morphology, surface and porosity of the NiO hexagonal plates indicated the formation of NiO without appearing any secondary phases, occupying the typical cubic structure. The ferromagnetic behaviour was examined by vibrating sample magnetometer (VSM). The sample exhibited ferromagnetic behaviour at room-temperature with the magnetic moment value of ~ 160 memu/g. The cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) anylysis were used to examine the electrochemical capacitance of the sample. The specific capacitance of the sample at a current density of 1 A/g was obtained to be 174.14 F/g. The cycle stability was excellent usability 76.6% after 500 cycles at a current density of 5 A/g.</jats:p

The facile one-step hydrothermal method to prepare MnO₂ nanoparticles: Structural and electrochemical properties

Abstract MnO2 nanoparticles were successfully prepared via one-step hydrothermal method. The surface are properties of the MnO2 nanoparticles were determined by BET nitrogen adsorption-desorption measurement. The XRD analyses confirm the pure phase of γ-MnO2 and α-MnO2, having orthorhombic crystal structure (JCPDS file no.14-0644 and 44-0141). FE-SEM analysis reveals the combination of massively small spherical particles with average particle size 54.8 nm. The electrochemical results revealed that the MnO2 nanoparticles delivered the specific capacitance of 200.83 F/g at a current density of 1A/g. The cycle stability was usability 30% after 500 cycles at a current density of 5 A/g. The MnO2 nanoparticles reveal a energy density of 3.62 Wh/kg under a power density of 43.11 W/kg.</jats:p

Effect of argon annealing method on structural and ferromagnetic properties in Fe-doped SnO₂ powders

Abstract Nanocrystalline powders of Fe-doped SnO2 (Sn1-xFexO2) (x = 0.00, 0.01, 0.03, 0.05) were prepared by a hydrothermal method. The powders were calcined in argon atmosphere at 600 °C for 2 h, causing phase transition from diamagnetic and weak ferromagnetic behavior to a ferromagnetic state. No trace and other magnetic impurity phases was detected in the samples with Fe content up to 3%. The calcined samples of Fe-doped SnO2 revealed the room temperature ferromagnetism with highest magnetization values of 434.07 memu/g at 15 kOe for x = 0.05. The room temperature ferromagnetism of samples originated from oxygen vacancies that occurred in the argon calcination process. In particular, oxygen vacancy shows a significant role in ferromagnetic coupling corresponding to F-center interaction.</jats:p

Effect of high sintering temperature on the cobalt ferrite synthesized via co-precipitation method

Magnetic particle is one of the main elements used in magnetorheological (MR) materials. In this study, the magnetic cobalt ferrite nanoparticles are successfully synthesized via co-precipitation method at different sintering temperatures. The nanoparticles are prepared in neutral condition (pH 7) at different temperatures of 900, 1000 °C for 8 h, individually. The properties of cobalt ferrite related to phase analysis, microstructure and magnetic properties were characterized by particle size analyzer (PSA), field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The result showed that the size of cobalt ferrite powders are 16.72, 17.76 and 37.29 nm correspond to different temperatures of 900, 1000 and 1100 °C, respectively. This indicated that the higher sintering temperature induced to the synthesized cobalt ferrite, greater size of the nanoparticles will be obtained. Meanwhile, the micrograph of cobalt ferrite powders poses a polygonal shape with all exhibit the face centered cubic (FCC) structure. In the meantime, the magnetic saturation, Ms increased with the size of nanoparticles increased from 28.95 to 38.85 emu/g, simultaneously correspond to increasing in the sintering temperatures. The results underlined that the sintering temperature did affect and alter the size of CoFe2O4 nanoparticles that resulted in magnetic properties enhancement