Simple Auto-combustion Method Research Articles

Influence of Exfoliated Boron Nitride for Fabrication of a Lightweight Wideband Microwave Absorbing Material

The study of electromagnetic (EM) wave absorbing materials is a natural response to ever-worsening EM wave pollution in modern days. Several nanomaterials have been explored as wideband, low-thickness, and lightweight microwave absorbing materials (MAMs) for use in both military and civilian realms but require significant improvement. This work presents the synthesis and charcaterization of in situ exfoliated boron nitride coated nickel ferrite (NiFBN) with excellent porous microstructure, using a simple auto-combustion method as well as the fabrication of a NiFBN-multiwalled carbon nanotube (MWCNT)-epoxy-based lightweight, thin nanocomposite for wideband microwave absorption (X-band). With a 2 mm thick sample, the 15-NiFBN-0.75_2mm nanocomposite exhibits effective absorption bandwidth (EAB) of 3.9 GHz and −59.38 dB reflection loss minima (RLmin). Several percentages of boron nitride with nickel ferrite were synthesized using the sol–gel auto-combustion process, and the MWCNT percentage was adjusted for enhanced microwave absorption.

Albumen-assisted Synthesis of Nanocrystalline Nickel Ferrite Photocatalyst

Abstract: As a simple step to remove the polluting dyes in aqua ecosystem, NiFe2O4 nanoparticles well known for their ferromagnetic properties, low conductivity and high electrochemical stability were prepared by simple auto combustion method using egg white as fuel via green synthesis route. The structural, morphological and magnetic properties of prepared NiFe2O4 was analyzed. The desirable phase purity of the prepared spinel ferrite was deliberated by X-ray Diffractometer (XRD), Fourier Transform Infrared Spectrometer (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive and Vibrating Sample Magnetometer (VSM). XRD predicts the phase formation, particle size and lattice parameter of the spinel ferrite. The FTIR spectrum confirms the ferrite structure. The morphological and elemental analysis was made using SEM and EDAX. The hysteresis curve reveals the magnetic properties, such as remanence magnetization (Mr), coercivity (Hc) and saturation magnetization (Ms). The photocatalytic efficiency of the synthesized samples was determined from degradation of methylene blue dye. The whole process was monitored using spectrophotometer at regular intervals of time. The maximum photocatalytic degradation efficiency for NiFe2O4 is around 95.6 %. Keywords: NiFe2O4, Ferrite, Green synthesis, Egg white, Combustion, Photocatalyst.

Enhanced multiferroics properties of strontium substituted bismuth ferrite prepared by auto combustion method

A low cost and simple auto combustion method was used to prepare the Bi1-xSrxFeO3 (x=0.0, 0.04, 0.08, 0.12, 0.16) multiferroics samples. X-ray diffraction patterns confirms the integration of BFO pure phase nanoparticles with a perovskite structure of ABO3 type having space group R3c. Spherical structure with little agglomeration was observed during the morphological studies of the prepared samples. Sr2+ substituted at the A-site produces expansion in Raman modes and increased variations in cation site occupancy. Impedance analyzer was used to examine the frequency dependent dielectric parameters (ε´, tanδ), electric conductivity (σac), impedance (Z) and electric modulus (Mʹ and M″) of the samples in frequency between 20 Hz and 20 MHz). Maximum value of dielectric constant was observed at very low frequency for x=0.0 samples and it decreases by increasing concentration. Resonance peak was observed in tangent loss for high content of strontium. Maximum value of Impedance was observed at low frequency and it decreases by increasing frequency which is due to the grain and grain boundary contributions. It is observed that ac conductivity of the samples is found to be frequency dependent and it varies with doping of Sr in BFO. Improved polarization was examined in P-E loop of Sr doped BFO nanoparticles.

Structure and magnetic properties of the porous Al-substituted barium hexaferrites

Ion substitution is considered to be one of the efficient approaches to improve the magnetic properties of the barium hexaferrites. In this work, we fabricated BaFe12−xAlxO19 (x = 0, 1, 2, 4, 6) via a simple auto-combustion method and investigated their structures, morphologies and magnetic properties. The coercivity is greatly affected by annealing temperature and Al3+ content. In addition, the Al3+ substitution sites in BaFe12−xAlxO19 were further investigated by the Mössbauer spectroscopy and the superparamagnetic components were found in the BaFe8Al4O19 and BaFe6Al6O19. The highest coercivity of 13.7 kOe was achieved in the BaFe8Al4O19, which increases by 168.6% compared with that of BaFe12O19. This work opens up a new and meaningful insight for the understanding of microstructure and coercivity mechanism towards the Al3+ substituted barium hexaferrites.

Tailoring the Ca-doped bismuth ferrite for electrochemical oxygen evolution reaction and photocatalytic activity

The development of perovskite-based materials with a narrow bandgap for oxygen evolution reactions (OER) and wastewater treatment have much attention in recent years. Herein, a narrow bandgap of Ca-doped BiFeO3 (BCFO) is synthesized by a simple auto combustion method. To create oxygen vacancies by doping Ca2+ the place of Bi3+, the amount of Fe3+ valence state is changed as well. 0.15% of Ca doped BiFeO3 (BCFO-15) indicate a high content of Fe4+ state with a conduction band and valence band located at 0.615 V and 2.46 V vs. NHE, respectively. The electrochemical OER of BCFO-15 observed a lower onset potential of 2.13 V vs. RHE, in acidic with a current density of 25.64 mA cm−2. In alkaline electrolyte, onset potential was observed at 2.10 V vs. RHE, with a current density of 65.87 mA cm−2. Furthermore, the photocatalytic performance of the perovskites in aqueous solution was demonstrated through photocatalytic reduction of Cr(VI) as a model pollutant, resulting in an 89.92% reduction of 50 ppm of Cr(VI) in 210 min under the irradiation of a 35 W Xe arc lamp. These findings suggest that simple divalent doping of Ca into pure BiFeO3 results in excellent photocatalytic and electrocatalytic perovskites.

Realizing alkaline all-pseudocapacitive supercapacitors based on highly stable nanospinel oxide coatings

For the first time, an all-pseudocapacitve supercapacitor based on Co and Fe nanospinel oxide coatings was developed for application in alkaline solution. The Co3O4 nanoflakes and the Fe3O4 nanospheres are coated on Ni foam by a simple autocombustion method without a binder. They exhibit pseudocapacitive behavior with high areal capacitances of 691 m F cm−2 and 404 m F cm−2, respectively that originates from multiple electron transfer reactions. Furthermore, systematic studies of the two electrodes during 4000 charge-discharge cycles by cyclic voltammetry, field emission scanning electron microscopy, and electrochemical impedance spectroscopy reveal high performance stability that are due to the multiple reversible redox reactions. Finally, the practical application of the electrodes was investigated in an asymmetric supercapacitor. The supercapacitor showed a capacitance of 191.6 m F cm−2, and average energy and power densities of 52.5 μWh cm−2 and 1.2 mW cm−2. This performance for a supercapacitor that is developed by a low-cost and sustainable process is highly appealing for practical applications.

Synthesis and characterization of BaFe2O4 nano-ferrites for gas sensor applications

BaFe2O4 spinel-type ferrite is synthesized by a simple auto-combustion method. The ferrites are based on spinel structure. The ideal spinel structure consists of the cubic close packing of oxygen anions with the tetrahedral (A site) and octahedral (B site) holes available for metal cation occupancy. Spinel ferrites have combined the both interesting magnetic properties and high electrical resistivity. The barium nitrate and ferric nitrate are taken as raw material, and combustion process is adopted for synthesis. The resultant ash was collected after combustion, and it is annealed at 700 and 900 °C. The synthesized products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrum and vibrating sample magnetometer. BaFe2O4 nanoparticles exhibit good magnetic property and also possess gas sensing ability. This material is more suitable for high-temperature gas sensor to support for clean environment.

Facile synthesis and characterization of Mn3O4 nanoparticles by auto-combustion method

Mn3O4 nanoparticles of different sizes were synthesized at low-temperature by a facile and simple auto-combustion method. Homogeneous potato-shaped grains with an average diameter of about 30, 60 and 90nm were obtained. The ignition temperature has a significant influence on the particle size of the product. Magnetization of the Mn3O4 nanoparticles shows a ferrimagnetic behavior at low temperature. The coercivity is approximately four times larger than that of bulk Mn3O4 due likely to the particle size effect, which may also be responsible for the observed complex hysteresis that exhibits at least two different magnetic behaviors. This work offers an environmental friendly and industrially robust route towards tailored, uniform and high-quality Mn3O4 nanoparticles.

Effect of Mn doping on microstructural and optical behavior of Zn(1−x)MnxO nanorod by simple auto-combustion method

Mn doped ZnO nanorods with different doping concentrations (0, 0.02, 0.05, 0.1, 0.15, and 0.2) were synthesized by simple auto-combustion method. The structural, morphological and optical behaviors of Zn(1−x)MnxO were investigated by X-ray diffraction (XRD), field-emission microscopy (FE-SEM) and diffuse reflectance spectroscopy (DRS). The structural properties of un-doped and Mn doped ZnO nanorods exhibit hexagonal wurtzite structure with no secondary phase. From scanning electron micrographs results it can be evidenced that, both crystallite size and surface morphology are significantly affected by Mn doping concentrations. From the optical studies, the reflectance in UV region of doped samples was decreased in comparison to undoped one and the optical band gap varies between 3.33 and 2.81eV. Photoluminescence spectra shows large emission band originated at 388nm and a weak band centered on 495nm. The present study reveals about the influence of Mn2+ ions on morphological and optical properties of Zn(1−x)MnxO.

Synthesis and magnetic properties of Mn doped ZnO nanowires

Mn doped ZnO nanowires have been synthesized using a simple autocombustion method. The as-synthesized Mn doped ZnO nanowires were characterized by X-ray diffraction and transmission electron microscopy. An increase in the hexagonal lattice parameters of ZnO is observed on increasing the Mn concentration. Optical absorption studies show an increment in the band gap with increasing Mn content, and also give evidence for the presence of Mn 2+ ions in tetrahedral sites. All Zn 1− x Mn x O ( 0 ≤ x ≤ 0.25 ) samples are paramagnetic at room temperature. However, a large increase in the magnetization is observed below 50 K. This behavior, along with the negative value of the Weiss constant obtained from the linear fit to the susceptibility data below room temperature, indicate ferrimagnetic behavior. The origin of ferrimagnetism is likely to be either the intrinsic characteristics of the Mn doped samples, or due to some spinel-type impurity phases present in the samples that could not be detected.