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Photocatalytic treatment of palm oil mill effluent by visible light-active calcium ferrite: Effects of catalyst preparation technique
摘要： Palm oil mill effluent (POME) is a serious and expensive environmental problem in Malaysia. In this paper, CaFe2O4 is introduced as a novel photocatalyst for the degradation of POME under visible light irradiation. Two synthesis routes, auto-combustion and co-precipitation, and two calcination temperatures 550 °C and 700 °C were used to produce four CaFe2O4 catalysts AC550, AC700, CP550 and CP700. CP550 exhibited the greatest photocatalytic degradation at 56% chemical-oxygen-demand (COD) removal after 8 h of irradiation which dropped to 49% after three consecutive cycles indicating reasonable conversion and high recyclability. BET analysis indicated CP550 had the highest SBET (27.28 m2/g) and pore volume (0.077 cm3/g) which dropped precipitously for CP700 upon increasing the calcination temperature to an SBET of 9.73 m2/g and pore volume of 0.025 cm3/g due to annealing which created a smoother surface area as evidenced by the SEM images. UV–Vis DRS indicated CP550 had the highest band-gap (1.52 eV) which is likely due to the presence of a highly crystalline pure CaFe2O4 phase compared to the other products which existed as a mixture of Fe oxidation states evidenced by the XRD data. The PL spectra for all catalysts indicated significantly lower recombination rate for both CP550 and CP700. Introduction of IPA into the reaction mixture to eliminate hydroxyl radicals resulted in a diminishing of COD removal from 56% to 7% proving hydroxyl radicals to be the primary reactive species responsible for photodegradation of POME.
关键词： Co-precipitation,POME,Photocatalysis,Visible light,Calcium ferrite,Auto-combustion
更新于2025-09-23 15:23:52
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Green Synthesis Approach for Nano sized CoFe2O4 through Aloe Vera Mediated Sol-gel Auto Combustion Method for High Frequency Devices
摘要： Nanosized CoFe2O4 was synthesized by Aloe vera-mediated sol-gel auto-combustion method. The yielded nanoparticles were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) to investigate the phase formation and morphology of the obtained powders. FTIR, XRD and Raman spectra revealed the formation of single phase CoFe2O4. FESEM micrographs showed the formation of some bud like structure and the particle size obtained is around 50-65?nm. Investigation of magnetic properties viz. saturation magnetization (Ms), remenant magnetization (Mr) and coercivity (Hc) were studied from the M-H loop and were found to be 72.23 emu/gm, 31.29 emu/gm, 1519 Oe respectively. In addition, the massive dielectric constant, low dielectric loss, and AC conductivity of the CoFe2O4 nanoparticles were dependent on the frequency (100 Hz-1 MHz), method of preparation and grain size. Room temperature ferroelectric measurement reveals a partially unsaturated P-E loop due to the high coercive field and influence of leakage current.
关键词： Aloe vera plant extract,magnetism,nanostructured materials,Dielectric properties,sol-gel auto combustion
更新于2025-09-23 15:21:21
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Hexaferrite multiferroics: from bulk to thick films
摘要： We report studies of the structural and microstructural properties of Sr3Co2Fe24O41 in bulk form and as thick films. The precursor powders for the bulk form were prepared following the sol-gel auto-combustion method. The prepared pellets were synthesized at 1200 oC to produce Sr3Co2Fe24O41. The XRD spectra of the bulks showed the characteristic peaks corresponding to the Z-type hexaferrite structure as a main phase and second phases of CoFe2O4 and Sr3Fe2O7-x. The microstructure analysis of the cross-section of the bulk pellets revealed a hexagonal sheet structure. Large areas were observed of packages of hexagonal sheets where the separate hexagonal particles were ordered along the c axis. Sr3Co2Fe24O41 thick films were deposited from a suspension containing the Sr3Co2Fe24O41 powder. The microstructural analysis of the thick films showed that the particles had the perfect hexagonal shape typical for hexaferrites.
关键词： hexaferrite,microstructure,sol-gel auto-combustion,thick films,multiferroics
更新于2025-09-23 15:21:01
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Investigation of the structural, optical, elastic and electrical properties of spinel LiZn <sub/>2</sub> Fe <sub/>3</sub> O <sub/>8</sub> nanoparticles annealed at two distinct temperatures
摘要： Nanoparticles of Li0.5ZnFe1.5O4 (LiZn2Fe3O8) with the spinel structure were prepared by a sol–gel auto-combustion method at two different annealing temperatures. X-ray diffractograms and Rietveld refinement confirmed the formation of the spinel structure. The morphology was analyzed by electron microscopy, which showed that the grains were composed of different crystallites. Elastic properties were determined from infrared spectroscopy. It was found that the elastic parameters increased with the increase in annealing temperatures. The band gap depends on the annealing temperature and it decreased on increasing the particle size. The conductivity of the specimen annealed at 500 °C followed either the Jonscher's model or Drude's model depending on the temperature range. This conductivity decreased when the annealing temperature was raised by 600 °C. AC conductivity was found to be controlled by the hopping model. A single relaxation phenomenon was evidenced for each sample from impedance analysis. The Nyquist diagram proved that the samples were simultaneously capacitive and resistive and also supported the presence of multiple relaxation times.
关键词： annealing temperature,spinel,conductivity,LiZn2Fe3O8,impedance analysis,band gap,elastic properties,sol–gel auto-combustion
更新于2025-09-16 10:30:52
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Magneto-structural properties and photocatalytic performance of sol-gel synthesized cobalt substituted Ni Cu ferrites for degradation of methylene blue under sunlight
摘要： In this study, Ni0.5-xCoxCu0.5Fe2O4 (with x varying from 0.0 to 0.5) ferrites have been synthesized by a sol-gel auto-combustion method using urea as fuel. The influence of Cobalt (Co2+) content on the structural, optical and magnetic Ni-Cu ferrites was studied by X-ray diffraction (XRD) patterns, Fourier Transform Infrared Spectroscopy (FT-IR), UV-Vis Spectroscopy (UV-DRS) and vibrating sample magnetometer (VSM). Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX) analysis have been used to determine morphology and compositions respectively. The X-ray diffraction studies have been carried out by considering the distance between adjacent crystal planes, lattice constant and average crystallite size which decrease from 44-35 nm with substitution of Co2+. FT-IR spectra show two major stretching bands around 400-600 cm-1. The magnetic parameters were measured at room temperature where increase in saturation magnetization was observed with increase in concentration of Co2+ in Ni-Cu ferrites. The photocatalytic performance study of Co2+ substituted Ni-Cu ferrites was carried out under visible and direct sunlight on methylene blue (MB) dye. The increase in degradation percentage was observed with Co2+ substitution in both visible and sunlight. The catalyst was found to be more efficient in sunlight with 91% degradation of MB within 120 minutes.
关键词： SEM,VSM,Ni-Co-Cu Ferrites,XRD,Sol-Gel Auto-Combustion,Photocatalyst
更新于2025-09-09 09:28:46
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Tuning the optical properties of ZnO:Cd by doping La and Y
摘要： Zinc oxide doped with Cadmium and rare earth elements synthesized by solgel auto combustion route is reported in this work. The studies have been carried out to analyze the structural, morphological and optical properties of Cd doped ZnO and rare earth doped ZnCdO. The XRD analysis reveals that the addition of rare earth impurity decreases the particle size of ZnCdO. La doped ZnCdO has the least particle size among the samples of ZnCdO and rare earth doped ZnCdO. The morphological changes due to the addition of rare earth impurities have been found. Samples of La doped ZnCdO shows a pillar like morphology. The hexagonal structures are prominently seen in the SEM micrographs of the samples of ZnCdO. The UV-Visible spectral analyses show that the bandgap reduces when ZnCdO is doped with the rare earth impurities. The photoluminescence spectra show the broad spectrum in visible region exhibited by ZnO and a scanty UV emission. The UV emission of rare earth doped samples decreases due to the destruction in the crystal structure. The rare earth doped ZnCdO shows a small peak in green emission that decreases when rare earth impurities are doped. There is a uniform spectral response other than a small Gaussian like green peak. The overall analyses show that the samples can be used in optoelectronic applications to work in the visible region.
关键词： rare earth elements,structural properties,optical properties,UV-Visible spectral analyses,Cadmium,SEM micrographs,photoluminescence spectra,XRD analysis,Zinc oxide,solgel auto combustion,morphological properties
更新于2025-09-09 09:28:46