Microwave-assisted Combustion Research Articles

Fuel aided rapid synthesis and room temperature ferromagnetism of M0.1Co0.1Zn0.8O (M=Mn, Ni, Fe and Cu) DMS nanoparticles

A systematic investigation on the structural and magnetic properties of transition metals (M=Mn, Ni, Fe and Cu) doped Co0.1Zn0.9O (M0.1Co0.1Zn0.8O) nanoparticles synthesized by an easy and inexpensive microwave-assisted combustion method is presented. X-ray diffraction (XRD) and HR-SEM results show single phase nature with hexagonal wurtzite structure, and reveal the incorporation of metal ions into the lattice positions of Zn ions in CoZnO lattice. Size of the nanoparticles was found to vary between 25.3nm and 33.5nm. The magnetization measurements result into ferromagnetic state for all doped samples. Saturation magnetization varies with the type of doped ions indicating the role of interaction between doped ions and Co ions. Ferromagnetic interaction enhances at low temperatures and remains non-zero above room temperature as suggested by magnetization vs. temperature measurements. The room temperature ferromagnetism of the samples was attributed to the exchange interactions between free delocalized carriers (holes from valance band) and the localized d spins of doped transition metal ions.

Eco-friendly and green synthesis of BiVO4 nanoparticle using microwave irradiation as photocatalayst for the degradation of Alizarin Red S

Bismuth vanadate (BiVO4) nanocrystals have been successfully synthesised using microwave-assisted combustion synthesis (MCS), and characterised using Fourier transform infrared (FT-IR) and Raman spectra, surface area analysis (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX), diffused reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. The XRD results confirmed the formation of monoclinic bismuth vanadate. The formations of BiO & VO43−vibrations were ascertained from FT-IR data. The morphology of hallow internal structural micro entities were confirmed by SEM. The optical properties were determined by DRS and PL spectra. Hence, the influence of the preparation methods on the structure, morphology and optical activities of bismuth vanadate was investigated systematically. Photocatalytic degradation (PCD) of Alizarin Red S (ARS), an effective disrupting chemical in aqueous medium was investigated using BiVO4 nanoparticles. The kinetics of PCD was found to follow pseudo first-order.

Sesamum indicum Plant Extracted Microwave Combustion Synthesis and Opto-Magnetic Properties of Spinel MnxCo₁₋xAl₂O₄Nano-Catalysts.

Spine Mn(x)Co₁₋xAl₂O₄ (x = 0, 0.3 and 0.5) nanoparticles were synthesized using Sesamum indicum (S. indicum) plant extracted microwave-assisted combustion method. S. indicum plant extract simplifies the process, provides an alternative process for a simple, economical and environment friendly synthesis. The absence of surfactant/catalysts has led to a simple, cheap and fast method of synthesis of spinel nanoparticles. The as-synthesized spinel nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET) surface area analysis, UV-Visible diffuse reflectance spectroscopy (DRS), Photoluminescence (PL) spectroscopy, and vibrating sample magnetometer. The formation of spinel nanoparticles was confirmed by HR-SEM and HR-TEM and their possible formation mechanisms were also proposed. Powder XRD, FT-IR, SAED and EDX results confirmed the formation of pure and single cubic phase CoAl₂O₄ with well-defined crystalline. The optical property was determined by DRS and PL spectra. VSM measurements revealed that pure and Mn-doped CoAl₂O₄ samples have weak ferromagnetic behavior and the magnetization values increases with increasing the concentration of Mn²⁺ ions in the CoAl₂O₄ lattice. The sample Mn₀.₅Co₀.₅Al₂O₄ possessed higher surface area and smaller crystallite size than other samples, which led to enhance the performance toward the selective oxidation of benzyl alcohol into benzaldehyde.

Comparative Studies of Spinel MnFe2O4 Nanostructures: Structural, Morphological, Optical, Magnetic and Catalytic Properties.

Spinel MnFe2O4 nanostructures with two different morphologies such as nanoflakes (NFs) and nanoparticles (NPs) were synthesized by a simple microwave-assisted combustion (MACM) and conventional combustion (CCM) methods respectively. Powder X-ray diffraction (XRD) study showed that the samples have pure cubic spinel phase and the average crystallite size is found to be 15.13 ± 2 nm and 24.38 ± 13 nm for NFs and NPs respectively. The calculated lattice parameter values of the samples NFs and NPs are 8.476 and 8.474 Å respectively. The morphology of the samples was recorded using high resolution scanning electron microscope (HR-SEM) analysis and was found that nanoflakes and nanoparticles morphologies by MACM and CCM methods respectively. Energy dispersive X-ray (EDX) results showed that the composition of the elements was relevant as expected from these combustion methods. The optical properties of the as-prepared nanostructures were also investigated by UV-Visible Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence (PL) Spectroscopy. The energy band gap (E(g)) of the sample NFs is 1.78 eV, whereas the sample NPs has 1.75 eV. The magnetic properties were investigated using the Vibrating Sample Magnetometer (VSM) at room temperature and the hysteresis loops confirmed the super-paramagnetic behavior for both samples with saturation magnetization (M(s)) values in the range of 59.29 ± 11 and 66.78 ± 06 emu/g for the samples NFs and NPs respectively. The oxidation of benzyl alcohol into benzaldehyde reached a maximum of 87.65% for MnFe2O4 NFs, whereas for MnFe2O4 NPs, the conversion was only 69.43% with 100% selectivity.

Synthesis of BSCF perovskites using a microwave-assisted combustion method

Ba0.5Sr0.5Co0.8Fe0.2O3−Δ (BSCF) perovskite-type oxide was synthesized using a microwave-assisted combustion method. Following about 10min of exposure to microwave, the combustion reaction was self-ignited and it produced a porous powder. For comparison, BSCF perovskite powders were also synthesized by conventional heating. Two different fuel types were used in the two heating methods. The crystalline BSCF powders were characterized using scanning calorimetry and thermogravimetry (DSC/TG), X-ray diffraction (XRD), BET surface area measurement, scanning electron microscopy (SEM), and dilatometric analysis. The microwave heating method resulted in a powder with nanometric crystallites, submicrometric particles, and a specific surface area of 9.93m2/g, which corresponds to a BET diameter of approximately 100nm. The dilatometric analysis showed that the microwave-synthesized BSCF powder has the maximum sintering rate at 970°C, but the sintering process initiates at lower temperatures.

MnCrxFe2−xO4 Nanoparticles: Magnetic and Microwave Absorption Properties

Chromium substituted Mn nanospinel ferrites having the formula MnCrxFe2−xO4 (0.0 ≤ x ≤ 1.0) have been synthesized using the microwave-assisted combustion synthesis. The composition, structural, spectroscopic features of the products were studied by X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. XRD investigations indicated the formation of single-phased cubic spinel structure for all products. Lattice parameters of the products represented the continuous decrease with increasing the substitution of Cr3+. The saturation magnetization of undoped sample appeared to be highest and as Cr3+ concentration increases magnetization of the samples decreases. There is one reflection loss minimum in all doped samples at around 13 GHz with magnitude of −12 dB mechanism of which is explained by quarter wave cancellation model.

MnFe2O4 nano spinels as potential sorbent for adsorption of chromium from industrial wastewater

In this study, nanospinels of MnFe2O4 were synthesized by a rapid method of microwave-assisted combustion technique for the removal of total chromium from real industrial wastewater. Nanoparticles of MnFe2O4 were characterized by X-ray diffraction and scanning electron microscopy. The removal of total chromium from real industrial wastewater, which was taken from galvanotechnic industry, using of nanospinel MnFe2O4 was investigated. The effects of adsorbent dosage, contact time, and initial concentrations on total chromium removal from wastewater were studied using the real wastewater. Optimal conditions were found for total chromium removal. Chromium removal and adsorption capacity of MnFe2O4 nanoparticles (NPs) were achieved as 59.35% and 89.18 mg/g, respectively. In addition, other optimum conditions of adsorbent dosage and contact time were found as 1.5 g/L and 120 min in this study, respectively. The removal of total chromium using MnFe2O4 NPs was fitted with Freundlich isotherm and pseudo-second-order kinetic models. The results indicated that MnFe2O4 nanospinels are suitable adsorbents for the removal of total chromium from industrial wastewater.

On the formation of Mo2C nanocrystals by a novel system through microwave assisted combustion synthesis

This research is devoted to microwave assisted combustion synthesis of Mo2C nanoparticles. The ternary system of MoO3–Zn–C was used as a novel approach for the in-situ synthesis of Mo2C in which the zincothermic reduction of MoO3 was responsible for the combustion to take place. Results showed that the formation of Mo2C was assisted by the zincothermic reaction, although further microwave heating up to 6min was necessary to complete the reaction. The effects of the microwave heating and mechanical activation on the reaction progress were investigated. X-ray powder diffraction was used to examine the synthesis progress. Final products (Mo2C and ZnO) were successfully separated from each other and the synthesized carbide was characterized by transmission electron microscopy (TEM), showing the formation of Mo2C hexagonal nanocrystals during combustion process.

Structural and Magnetic Properties of NiCr x Fe2−x O4 Nanoparticles Synthesized via Microwave Method

The nanocrystalline NiCr x Fe3−x O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) have been synthesized by microwave-assisted combustion method, and the effect of Cr3+ substitution on the structural and magnetic properties of NiFe2O4 was studied. Phase formation was identified by X-ray powder diffraction (XRD), which confirmed the formation of a cubic spinel structure for all the compositions. The lattice “a” of all samples decreases with the increase in Cr contents in the compositions. The elemental analysis by scanning electron microscopy-energy dispersive X-ray was in close agreement with the expected composition from the stoichiometry of the starting composition used for the synthesis. NiFe2O4 and NiCr0.2Fe1.8O4 nanoparticles (NPs) show features of superparamagnetin NPs, namely reduced and unsaturated magnetization together with the absence of coercivity.

Effect of CeO2 coupling on the structural, optical and photocatalytic properties of ZnO nanoparticle

This research work presents the microwave assisted combustion synthesis, characterization and photocatalytic applications of ZnO–CeO2 coupled nano metal oxide. ZnO, CeO2 and the coupled oxides ZnCe, Zn2Ce and ZnCe2 with ZnO and CeO2 in the molar ratio 1:1, 2:1 and 1:2 respectively were fabricated by microwave assisted metal nitrate-urea solution combustion synthesis, without using any organic solvent or surfactant. As-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy(PL). The experiments of photocatalytic activity indicate that Zn2Ce nanoparticles exhibit excellent photocatalytic performance in the degradation of 2,4-dichlorophenol (2,4-DCP). 95% of 2,4-DCP molecules were decomposed by Zn2Ce in 240 min. The better photocatalytic degradation ability of Zn2Ce compared to ZnCe, ZnCe2 or single component ZnO and CeO2 nanoparticles is attributed to the improved separation of photogenerated electron–hole pairs.

Rapid synthesis of room temperature ferromagnetic Fe and Co co-doped ZnO DMS nanoparticles

Rapid production and characterization of Fe and Co co-doped ZnO nanoparticles are reported. FexCo0.1Zn0.9−xO (0.0≤x≤0.2) nanoparticles have been synthesized by a simple microwave-assisted combustion method. X-ray diffraction spectra of FexCo0.1Zn0.9−xO (0.0≤x≤0.2) nanoparticles confirmed the hexagonal wurtzite structure without any secondary phase formation. SEM micrographs indicated that all samples have grains mainly in the form of nanoparticles. Magnetic property investigations have been done by VSM and the results revealed that all samples have M–H curves with a small coercivity and remanence indicating room-temperature ferromagnetic properties. The saturation magnetization and coercivity of the samples were increased by Fe doping.

A three-step synthesis process of submicron boron carbide powders using microwave energy

In this study, a three-step synthesis process is proposed for the production of submicron B4C powders. The initial step is the mechanical activation of a Mg–C–B2O3 mixture, which is carried out by using a high-energy planetary ball mill. The second phase is the microwave-assisted combustion synthesis, used to fabricate the MgO–B4C composite powders. The final stage is an acid leaching for removing the MgO phase. The results of DSC, XRD, and SEM analyses indicated that mechanical activation was a vital process for microwave synthesis and that no starting powders were remained unreacted after microwave heating. A considerable reduction in reaction temperature was obtained from DSC analysis after mechanical activation process. TG results indicated that separated milling of Mg with B2O3 powders would avoid the formation of gases during exothermic reactions. Finally, it was found that submicron boron carbide powders with an average crystallite size about 114 nm were produced with a high purity after acid leaching.

High-Performance SOFC Electrodes Synthesized By Novel One-Step Chemical Routes

The next generation of hydrogen-operated solid oxide fuel cells (SOFCs) will most certainly rely on high-performance ceramic and composite electrode materials manufactured from optimized routes. La0.6Sr0.4Co0.2Fe0.8O3-Ce0.8Sm0.2O1.9 (LSCF-SDC, 50 wt.% SDC) and NiO-CGO (50 wt.% NiO) composite powders, usually employed to prepare SOFC electrodes, were synthesized by two novel one-step synthetic routes, namely microwave-assisted combustion and a modified polymeric precursor method, respectively. Powder characterization was carried out by XRD and TEM. Screen-printed electrodes with different microstructures, evaluated by scanning electron microscopy, were obtained on CGO pellets. The electrochemical performances for the hydrogen oxidation and oxygen reduction reactions were investigated by impedance spectroscopy in the temperature range of 650-750 °C using flowing humidified 10% H2 + 90% N2 gas mixtures for the anodes and pure oxygen for the cathodes. By using a three-electrode configuration cell, dc polarization measurements were also performed on selected electrodes. The results of the electrochemical characterization indicated a significant dependence of the area specific resistance (ASR) on the electrode microstructure, highlighting that the electrode resistance can be manipulated by microstructural design. The best ASR values obtained at 750 °C in pure oxygen (cathode) and hydrogen atmosphere (anode) were found to be 0.18 and 0.15 ohm.cm2, respectively. The one-step Ni-CGO electrode with improved microstructure showed an anodic overpotential of 91 mV at 750 °C for a current density of 322 mA/cm2, which is amongst the best results mentioned in the literature, demonstrating that the novel one-step synthesis routes are innovative chemical ways to prepare promising SOFC electrodes.

Microwave-assisted combustion synthesis of Fe3Al bulk nanocrystalline intermetallic matrix composites

Fe3Al bulk nanocrystalline intermetallic composites were prepared by microwave-assisted combustion synthesis technology under air atmosphere. The bulk Fe3Al intermetallic composites mainly consist of nanocrystalline matrix and inclusions of micro-scale acicular and granular Fe3Al phases. The acicular Fe3Al phases are presented at the grain boundary of original α-Fe solid solution phase, while the granular phases surround the intragranular Al2O3 particles. The formation of nanocrystalline matrix composites is mainly attributed to the high superheat in the process of microwave-assisted combustion synthesis and the rapid cooling effects of copper mold.

Synthesis of Superparamagnetic Ni0.40Zn0.60Fe2O4 Nanoparticles Using a Microwave-Assisted Combustion Method

The powder of Ni 0.40Zn 0.60Fe 2 O 4 nanoparticles is synthesized using a microwave-assisted combustion method. X-ray diffraction and IR spectrum analysis show that the sample has a single-phase spinel structure. Debye–Scherrer formula reveals a crystallize size of 49 nm ±5 %, whereas transmission electron microscopy (TEM) results show particle sizes in the range of 10 to 60 nm. Superparamagnetic nature of the sample was confirmed from a close hysteresis loop. The Curie temperature (T C) was found to be 422 ∘C and 30 K as a blocking temperature.

Microwave-assisted combustion synthesis of nanocrystalline Sm-doped La2Mo2O9 oxide-ion conductors for SOFC application

The synthesis of nanocrystalline La2−xSmxMo2O9 (0≤x≤0.6) oxide-ion conductors by a microwave assisted-combustion method using aspartic acid as a combustion fuel is presented. A single-phase Sm-doped La2Mo2O9 nanopowders (∼25nm) were produced within 45min. The Sm-doping (x≥0.2) effectively suppressed the α→β phase transition of pure La2Mo2O9 and maintained the high temperature cubic phase at room temperature. The synthesized nanocrystalline Sm-doped samples had good sinterabilty and relatively a low sintering temperature of 800°C for 5h was sufficient to reach ∼98% of its theoretical density. Sm-doping effectively improved the oxide ion conductivity of La2Mo2O9 and the maximum oxide-ion conductivity of 0.196Scm−1 was attained at 750°C for of La1.7Sm0.3Mo2O9.

Experimental and first-principles DFT studies of electronic, optical and magnetic properties of cerium–manganese codoped zinc oxide nanostructures

Syntheses, structural, optical and magnetic characterizations of codoped ZnO nanoparticles have been reported. Nanoparticles of Zn1−2xCexMnxO (x=0.00, 0.01, 0.02, 0.03, 0.04, and 0.05) were synthesized using a microwave-assisted combustion method. Structural, optical and magnetic properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL) and a vibrating sample magnetometer (VSM). The observed shift in XRD peak position, change in peak intensity, cell parameters, volume and stress confirmed the substitution of cerium-manganese (Ce–Mn) dopants within ZnO lattice. The synthesized nanoparticles show different microstructure without changing the parent hexagonal wurtzite structure of zinc oxide (ZnO). The average crystallites size was decreased from 43 to 21nm. Energy dispersive X-ray spectra confirmed the presence of Ce and Mn in ZnO system and the weight percentage was nearly equal to their nominal stoichiometry. DRS analysis showed a decrease in the energy gap with increasing dopants content. The observed luminescence in the green, violet and blue regions strongly depends on the nature of the doping elements and their concentration owing to the formation of different oxygen vacancy, zinc interstitial, and surface morphology. Our results demonstrate that Mn ions doping concentration play an important role in the observed room temperature ferromagnetism (RTFM) of Ce–Mn codoped ZnO nanoparticles. First- principles calculation results indicate that Ce governs the stability, while Mn adjusts the magnetic characteristics in codoped ZnO.

The effect of Sr2+ on the structure and magnetic properties of nanocrystalline cobalt ferrite

We report the effect of Sr2+ on the structure, morphology and magnetic properties of CoFe2O4 synthesized by microwave-assisted combustion method. Results from X-ray diffraction and Mössbauer spectroscopy at 298K suggest the formation of a mixed spinel Sr2+ substituted CoFe2O4. However, secondary phases like CoO, SrCO3 and SrFeO2.96 were also observed. A decrease in the lattice parameter and particle size were observed with the addition of Sr2+. The crystallite size of ferrite phase ranged from 53 to 62nm. Magnetic studies showed a gradual decrease in the saturation magnetization and remanence with the increase of Sr2+ content, and an increasing value of the coercive field.

A 60-Second Microwave-Assisted Synthesis of Nickel Foam and Its Application to the Impregnation of Porous Scaffolds

A rapid and facile method to prepare nickel foam from nickel nitrate and glycine using a conventional microwave oven is presented. The foam, characterized by SEM, XRD-Rietveld, TG, magnetization measurements and BET contains mostly nickel metal (80 w%) and nickel oxide (20 w%); it exhibits pores in the sub micrometric and nanometric scale and consists of particles with an average diameter of 45–47 nm and BET surface of 15.9 gm−2. This microwave-assisted combustion synthesis is used to infiltrate porous ceramic scaffolds with nickel metal as a potential method to accelerate the fabrication of electrodes in solid oxide fuel cells and electrolysers. After repeated impregnation, the scaffolds of Ce0.9Gd0.1O2, saffil (high temperature insulating brick), La0.2Sr0.7TiO3 and BaCe0.5Zr0.3Y0.16Zn0.04O3-δ were black, exhibited electrical continuity and were easily lifted with a magnet. A comparative SEM study of the microstructure of the porous scaffolds with and without nickel is presented.

Experimental and DFT studies of structure, optical and magnetic properties of (Zn1−2xCexCox)O nanopowders

A simple one-step microwave-assisted combustion method using urea as a fuel, was applied to develop the nanophase powders of ((Zn1−2xCexCox) O (x=0.00, 0.01, 0.02, 0.03, 0.04, and 0.05)). The results emphasize that by changing the codopant concentration it is feasible to fine-tune structural, morphological, optical and magnetic properties. The synthesized nanoparticles gave rise to new microstructures without changing the basic hexagonal wurtzite structure. The substitution of Ce and Co into ZnO lattice was confirmed from the shift in XRD peaks position, changes in peaks intensity, and cell parameters. Energy dispersive X-ray spectra confirmed the presence of Ce and Co within ZnO system; the weight percentage was close to their nominal stoichiometry. Ultraviolet–visible (UV–Vis) spectroscopy analysis indicated that the optical band gap decreased with the increase of Ce and Co codoping concentration. It is clear from SEM images that the average particles size decreased from 50nm to 25nm when codoping concentration was increased up to 0.05M. Photoluminescence spectra exhibited the emission bands in ultra-violet and blue–green regions. Magnetization-Field (M–H) hysteresis loops revealed that the codoped nanopowders exhibited room temperature ferromagnetism (RTFM). Using first principles calculations, based on density functional theory, electronic and magnetic properties of codoped ZnO for different dopants concentration, were predicted. It is found that the observed RTFM is originated mainly from spin polarization of Co-d orbital, Ce-f orbital has partial contribution.