ABSTRACT
Highly pure BiFeO3 (BFO) powders were prepared by the solution combustion synthesis method using cetyltrimethylammonium bromide (CTAB) and glycine as fuels at various fuel-to-oxidant (φ) ratios. Microstructural characteristics, morphology, optical properties, and thermal analysis were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and differential thermal/thermogravimetry (DTA/TGA), respectively. The combusted powders prepared at different fuel content contained a small amount of impurity phases such as Bi24Fe2O39 and Bi2Fe4O9. During the calcination of BFO powders at 600 °C for 1 h, a nearly pure BFO phase was produced. Combusted powders photodegraded about 80% of methylene blue dye at φ = 2 through 90 min of visible light irradiation.
ABSTRACT
Spongy NiCo2O4 powders were prepared by solution combustion synthesis (SCS) method for lithium ions storage. The effects of combustion parameters including fuel type (L-lysine, glycine, and urea) and fuel amount on the lithium storage performance of NiCo2O4 powders were analyzed by various characterization techniques. Single-phase NiCo2O4 powders with extremely porous microstructure showed a strong drop of initial specific capacity up to 350 mAhg-1 which was recovered up to 666 mAhg-1 following 100 charge/discharge cycles. However, the NiCo2O4 powders prepared by the urea and L-lysine fuels with the compacted microstructure showed the capacity loss without any recovery. The spongy NiCo2O4 powders showed an acceptable capability rate performance (404 mAhg-1 @ 400 mAg-1).
Subject(s)
Lithium , Lysine , Powders , Ions , UreaABSTRACT
α-Fe2O3/Fe3O4/g-C3N4 nanocomposites were prepared in-situ by solution combustion as magnetically separable photocatalysts using ferric nitrate as oxidant, glycine as organic fuel, and g-C3N4. The effects of various amounts of iron oxides, on the magnetic, optical, and photocatalytic properties were explored by different characterization methods. The magnetite (Fe3O4) phase as ferrimagnetic material disappeared with the increase in ferric nitrate contents, leading to the decrease of magnetic properties. The bandgap energy decreased from 2.8 to 1.6 eV with the increase of the hematite (α-Fe2O3) phase.The photocatalytic results showed that the type and amount of iron oxides had a significant effect on the decolorization of methylene blue, rhodamine B and methyl orange dyes under visible-light irradiation. The activity of the nanocomposite sample containing 37 wt. % iron oxides was more effective than that of the pristine g-C3N4 sample to photodegrade the methylene blue, rhodamine B and methyl orange, respectively. Moreover, the nanocomposites exhibited a higher photocurrent density than that of the pristine g-C3N4, mainly due to their lower charge recombination rate.
ABSTRACT
Nickel-zinc ferrite (Ni0.5Zn0.5Fe2O4) powders were prepared by the conventional solid-state route and sintered at 1100 and 1300 °C for utilization as a tile electromagnetic wave absorber. Structural, magnetic, and microwave absorption properties were investigated by characterization techniques of X-ray diffraction, thermogravimetric analysis, Raman spectroscopy, electron microscopy, vibrating sample magnetometry, and vector network analyzer. The samples sintered at 1300 °C showed high magnetic saturation of 87 emu/g and low coercivity of 4 Oe. Electromagnetic investigations exhibit high reflection losses up to - 48.1 dB at certain high and low gigahertz frequencies, as clearly depicted in the 3D contour plot. The optimized condition between reflection loss, thickness, and bandwidth revealed a reflection loss of about - 36.1 dB at the matching thickness of 3.7 mm for the X-band. Furthermore, the effective working bandwidth at - 10 dB was up to ~ 7.1 GHz for the minimum thickness of 4.3 mm, which thoroughly covered the C-band. The microwave absorption performance of the well-sintered Ni-Zn ferrite was attributed to the incorporation of dielectric and magnetic loss mechanisms in which the magnetic part prevails.
ABSTRACT
Herein, BiFeO3/ZnFe2O4 nanocomposites were synthesized via a glyoxylate precursor method using a two-pot approach. Phase evolution is investigated by X-ray diffraction and Raman spectroscopy, which confirm that no impurity phases are formed between BiFeO3 and ZnFe2O4 following calcination at 600 °C. The specific surface area characterized by N2 adsorption-desorption isotherms decreases from 30.56 to 13.13 m2 g-1 with the addition of zinc ferrite. In contrast, the magnetization increases from 0.28 to 1.8 emu g-1 with an increase in the amount of ZnFe2O4. The composites show strong absorption in the visible region with the optical band gap calculated from the Tauc's plot in the range from 2.17 to 2.22 eV, as measured by diffuse reflectance spectroscopy. Furthermore, the maximum efficiency for the photodegradation of methylene blue under visible light is displayed by the composite containing 25 wt% ZnFe2O4 due to the synergic effect between BiFeO3 and ZnFe2O4, as confirmed by photoluminescence spectroscopy.
