Browsing by Author "Bouziani, Asmae"
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Article Citation Count: 11Effects of fluorination and thermal shock on the photocatalytic activity of Bi2O3 nanopowders(Elsevier, 2021) Park, Jongee; Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials EngineeringFluorinated Bi2O3 (F-Bi2O3) nanopowder was prepared via fluorination followed by thermal shock of alpha-Bi2O3 nanopowder. The XRD, FTIR, SEM, and DRS characterization techniques were employed to investigate the effects of fluorine (F) insertion into the alpha-Bi2O3 host and the thermal shock from different temperatures. The crystal structure, optical and photocatalytic properties of the F-Bi2O3 nanopowders prepared were researched. The XRD results confirmed the substitution of O2- with F-. The FTIR results revealed that the coordination of Bi atoms changed upon F- substitution. The incorporation of F into the alpha-Bi2O3 host and thermal shock did not influence the morphology but modified the band structure of alpha-Bi2O3, leading to a red-shift in the optical absorption edge. Also, the bandgap narrowed from 2.8 eV to 2.6 eV. The density functional theory calculation proved that the F 2p orbitals were positioned in the valence band (VB), resulting in broader and more spread bands for F-Bi2O3. The results suggested that the photoexcited charge carrier mobility in the valence band (VB) and conduction band (CB) are enhanced upon F insertion into alpha-Bi2O3. The photocatalytic efficiency of the synthesized nanopowders was assessed by the degradation of Bromocresol Green (BG) under visible light illumination. Photocatalytic activity improved upon fluorination. The F-Bi2O3 nanopowders thermally shocked from higher temperatures showed negligible photocatalytic performance. The best photocatalytic performance of 70% BG degradation was realized after 180 min visible irradiation for the F-Bi2O3 nanopowder thermal shocked from 500 degrees C.Article Citation Count: 17Synthesis and enhanced photocatalytic activity of nitrogen-doped triphasic TiO2 nanoparticles(Elsevier Science Sa, 2019) Park, Jongee; Bouziani, Asmae; Park, Jongee; Micusik, Matej; Kim, Soo Young; Majkova, Eva; Ozturk, Abdullah; Metallurgical and Materials EngineeringTiO2 nanoparticles of the single anatase phase, binary anatase-brookite phases, and ternary anatase-brookite-rutile phases were synthesized using an HNO3-catalyzed hydrothermal process. The types and amounts of phases varied depending on the hydrothermal synthesis conditions. The results revealed that N dissolves in different amounts and chemical states, depending on the phases present and their proportions in the nano particles. Brookite and rutile nanoparticles oriented through one direction were found to be crystallized by the surface transformation from anatase. Photocatalytic activity tests, evaluated by degradation of methylene blue (MB) under ultraviolet (UV) and visible light illumination, revealed that the N-doped TiO2 nanoparticles containing a ternary-phase mixture had the best photocatalytic activity. The MB degradation of the visible light-active nanoparticles was three times better than that of a commercially available well-known TiO2 powder, P25 under UV illumination. The enhanced photoactivity was attributed to the following: i) a high surface area, ii) suppression of the recombination of electron-hole pairs with ternary-phase mixture crystallized in heterojunctions, iii) larger anatase phase content, and iv) narrower band gap and facilitation of charge separation by dissolved N atoms.Article Citation Count: 33Synthesis of α-Fe2O3/TiO2 heterogeneous composites by the sol-gel process and their photocatalytic activity(Elsevier Science Sa, 2020) Park, Jongee; Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials Engineeringalpha-Fe2O3/TiO2 heterogeneous composites were synthesized by the sol-gel process to increase the photocatalytic activity of TiO2. The structural, morphological, and optical characteristics of the composites were determined by X-ray diffraction, scanning electron microscope, and UV-vis diffuse reflectance spectroscopy. Results revealed that the incorporation of alpha-Fe2O3 to TiO2 widened the visible light absorption ability of TiO2. It was realized that the calcination temperature plays a crucial role in morphology development hence photocatalytic activity of the alpha-Fe2O3/TiO2 heterogeneous composites. The photocatalytic activity of the composites calcined at various temperatures was evaluated for the degradation of Methylene Blue (MB) and Phenol (Ph) in aqueous medium under UV and sun-like illuminations. The alpha-Fe2O3-TiO2 composites exhibits superior photocatalytic efficiency to degrade both MB and Ph as compared to both pristine TiO2 and pristine alpha-Fe2O3 under sun-like illumination. The alpha-Fe2O3/TiO2 composite degraded approximately 90 % of MB and 50 % of Ph in 180 min sun-like illumination. Improvement in photocatalytic activity is attributed to the separation of photogenerated electron/hole pairs through the interaction of alpha-Fe(2)O(3 )and TiO2.