Microwave-assisted Combustion Method Research Articles

Magnetic properties of LiZnCu ferrite synthesized by the microwave sintering method

Abstract Lithium ferrites have attracted considerable attention because they have been used as replacements for garnets due to their low cost. A series of polycrystalline ferrite samples were prepared with the composition of Li X Zn (0.6−2 X ) Cu 0.4 Fe 2 O 4 ( X =0.05, 0.1, 0.15, 0.2, 0.25, 0.3) at chemical reaction temperature 150 °C by sintering with microwave assisted combustion method. The characterization shows the formation of single phase cubic structure when carried out by using the X-rays technique and I – R technique. Magnetization parameters such as saturation magnetization, coercivity, magnetic moment were calculated by using the Hysteresis graph. The Curie temperature obtained using the susceptibility data are found to be in the range 350–700 °C. Anhysteric remanent magnetization is used for estimating the grain size and domain structure of the composition. An attempt has been made to synthesis the nano-particles at lower reaction temperature by using non-conventional microwave sintering method. The advantage of this method is its lower sintering temperature and time compared to the conventional ceramic technique and direct formation of nano-ferrites without ball-milling.

Co-Doped ZnO Nanoparticles: Structural, Morphological, Optical, Magnetic and Antibacterial Studies

Un-doped and Co-doped ZnO nanoparticles (NPs) with different weight ratios (0.5, 1.0, 1.5, and 2.0 wt% of Co) were synthesized by a facile and rapid microwave-assisted combustion method using urea as a fuel. The prepared NPs were characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). XRD patterns refined by the Rietveld method indicated that Co-doped ZnO had a single pure phase with wurtzite structure suggesting that Co2+ ions would occupy Zn2+ ionic sites within the ZnO crystal lattice. Interestingly, the morphology was found to convert substantially from grains to nanoparticles with close-packed periodic array of hexagonal-like shape and then into randomly distributed spherical NPs with the variation of Co-content. The optical band gap estimated using DRS was found to be red-shifted from 3.22 eV for the un-doped ZnO NPs then decrease up to 2.88 eV with increasing Co-content. PL spectra showed a strong green emission band thus confirming the formation of pure single ZnO phase. Magnetic studies showed that Co-doped ZnO NPs exhibited room temperature ferromagnetism (RTFM) and that the saturation magnetization attained a maximum value of 2.203 × 10−3 emu/g for the highest Co-content. The antibacterial studies performed against a set of bacterial strains showed that the 2.0 wt% Co-doped ZnO NPs possessed a greater antibacterial effect.

Rapid synthesis and room temperature ferromagnetism of Ni doped ZnO DMS nanoflakes

NixZn1−xO (x=0.0, 0.05, 0.1, and 0.2) nanoflakes were successfully synthesized by microwave-assisted combustion method. The structural and morphological characterizations of the as synthesized samples were done by using XRD and SEM. Optical and magnetic properties of NixZn1−xO samples were analyzed by a UV–vis spectrophotometer and VSM magnetometer. XRD patterns indicate the hexagonal wurtzite structure of all samples without any impurity phases. SEM micrographs indicated that all samples have grains mainly in the form of nanoflakes. From UV–vis spectra of the samples, it is observed that pure ZnO sample has an energy band gap of 3.13eV and it is decreased by Ni doping. Magnetic property investigations have revealed that all samples have room-temperature ferromagnetic properties. The saturation magnetizations of the samples were increased by Ni doping. The difference between temperature dependent magnetization curves (the difference between field cooled-FC and zero field cooled-FC magnetization curves) also indicated the ferromagnetic behaviors of the samples at all measuring temperatures with a Curie temperature above the room temperature.

Synthesis of porous adsorbent using microwave assisted combustion method and dye removal

Zinc aluminum hydroxide (ZAH) as a porous adsorbent was synthesized using microwave assisted combustion method and its dye removal ability from single and binary systems was studied. The ZAH characteristics were investigated using XRD, FTIR, and SEM. Acid Blue 92(AB92), Acid Red 14 (AR14), and Direct Red 23 (DR23) were used. The effect of ZAH dosage and initial dye concentration on dye removal was investigated. Adsorption isotherm and kinetic was evaluated. The capacity of ZAH to remove AB92, AR14, and DR23 was 95mg/g, 84mg/g and 75mg/g, respectively. Dye removal fitted with the Langmuir model and pseudo-second order kinetics.

Synthesis and characterization of ZnO nanoparticle synthesized by a microwave-assisted combustion method and catalytic activity for the removal of ortho-nitrophenol

AbstractZnO nanoparticles were manufactured using microwave-assisted combustion. The structural and morphological properties of the nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. Photocatalytic degradation of ortho-nitrophenol (O-NP) in aqueous solution using the synthesized nanoparticles was performed under UV–C irradiation and is reported for the first time. The effect of the initial O-NP concentration, amount of photocatalyst, pH, and salt was investigated during photodegradation. Analysis of the degraded samples using HPLC with UV detection revealed that photocatalysis in the presence of ZnO nanoparticles removed 98% of the O-NP in 5 h. In addition, the photocatalytic degradation kinetics of O-NP were studied, and the results suggest that the data are best fitted to pseudo-first-order kinetic and Langmuir–Hinshelwood models.

Preparation of nano phosphors by Microwave-assisted combustion synthesis

In this review article, we have discussed synthesizing of nano phosphor materials by the Microwave assisted Combustion process. Several literature conclude that efficient synthesis of nano phosphor materials can be achieved only through microwave-assisted combustion method. Also we have discussed about the principle and working process behind the Microwave process. After undergoing literature survey on combustion process we have discussed the preparation process of fuel to oxidizer ratio which plays a major role for obtaining nano powders that are essential in display application.

Mössbauer and magnetization studies of nickel ferrite nanoparticles synthesized by the microwave-combustion method

Nanocrystalline nickel ferrite was synthesized from its stoichiometric metal nitrates and urea mixtures, using a microwave assisted combustion method. The process was a convenient, inexpensive and an efficient method for formation of NiFe2O4 nanomaterials. Effect of urea/metal nitrates ratio on the obtained phases, particle size and magnetic properties has been investigated by various techniques. Saturation magnetization of 50emu/g was observed at room temperature for larger particles, and it decreases with decreasing particle size. The coercivity attains a maximum value of 170Oe when the particle size was ~20nm, and decreases with increasing particle size. Mössbauer spectra measured at RT for some representative samples show a combination of ordered and superparamagnetic behavior, whereas those collected at 20K elucidate the nature of the obtained phases and cation distribution.

Synthesis and Characterization of NiFe2O4 Magnetic Nanoparticles by Combustion Method

Magnetic nanoparticles of nickel ferrite (NiFe2O4) have been successfully synthesized by microwave-assisted combustion method using stable ferric and nickel salts as precursors and glycine as fuel. The as-synthesized samples were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and field emission scanning electron microscopy (FESEM). The effect of different dose of glycine on the structural parameters and magnetic properties of the prepared NiFe2O4 nanoparticles was also investigated. This study revealed that it was possible to produce larger size of nanoparticles with lower saturation magnetization by using higher dose of fuel.

Rapid Synthesis of Nanocrystalline NiFe2O4 and CoFe2O4 Powders by a Microwave-Assisted Combustion Method

A facile and rapid microwave-assisted combustion method was applied to synthesize the nanocrystalline NiFe2O4 and CoFe2O4 powders. The results suggested that application of microwave heating to synthesize the homogeneous porous NiFe2O4 and CoFe2O4 powders was achieved in a few minutes. The structure and morphology of the as-prepared nanocrystalline powders of NiFe2O4 and CoFe2O4 were investigated by means of X-ray diffraction (XRD) and tunneling electron microscopy (TEM). The XRD spectra confirmed the formation of spinel structure with a crystallite size of 30.03 nm for NiFe2O4 and 36.7 nm for CoFe2O4 nanopowders, and TEM results indicated spherical shape of the products. Magnetic measurements revealed that at room temperature while NiFe2O4 is superparamagnetic, CoFe2O4 shows ferromagnetic behavior.

Microwave-Assisted Combustion Synthesis of ZnO Nanoparticles

A new and simple method was applied for the synthesis of ZnO nanoparticles with an average size of 20 nm. In this microwave-assisted combustion method, glycine as a fuel and zinc nitrate as precursor were used. The final product was obtained very fast with high yield and purity. The synthesized nanoscale ZnO was characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FT-IR). The size and morphology of the ZnO nanoparticles have been determined by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. This is a simple and fast method for the preparation of ZnO nanoparticles with no need for expensive materials or complicated treatments.

Effect of complexing agents on the powder characteristics and sinterability of neodymium doped yttria nanoparticles

Abstract We report the synthesis of neodymium doped cubic yttria (Nd:Y 2 O 3 ) nanopowders by microwave assisted combustion method using citric acid, urea and l -alanine as complexing agents as well as fuels. FTIR and XRD of powders calcined at 1000 °C for 3 h in oxygen atmosphere demonstrated formation and phase purity of Nd:Y 2 O 3 respectively. Varied morphologies of as prepared precursor and calcined oxide (from polyhedral to spheroidal) due to different complexing agents were observed by SEM and TEM. Sintering of these nanopowders with different morphologies after compaction by cold isostatic press at 400 MPa at 1700 °C for 10 h under 10 − 5 mbar vacuum gave maximum densification with 32.5% transmission by using l -alanine compared to 20% and 8% transmission obtained for urea and citric acid respectively. Thus l -alanine gave highly sinterable nanopowders with narrow size range of 25–40 nm with close to spherical morphology.

Rapid synthesis of nanocrystalline ZnO by a microwave-assisted combustion method

A facile and rapid microwave-assisted combustion method (MWAC) was developed to synthesis to produce nanocrystalline ZnO powder using dissolution of zinc nitrate (as the oxidant) and urea (as fuel) as the starting materials and water as solvent, then heating the resulting solution in a microwave oven. The study suggested that application of microwave heating to produce the homogeneous porous ZnO was achieved in a few minutes. The structure and morphology of the as-prepared combustion products were investigated by means of X-ray powder diffraction (XRD), Fourier transform infrared spectra (FTIR), Raman spectra, UV–Vis absorbance spectra and Scanning electron microscopy (SEM). The XRD, FTIR and Raman spectra confirmed the formation of hexagonal wurtzite structural ZnO and the SEM results indicated the porous surface characteristic of the products. The as-prepared powders have larger band gap energy (3.06eV) and are described here.

Characterization and Magnetic Properties of Nanoparticle Ni1−x Zn x Fe2O4 Ferrites Prepared Using Microwave Assisted Combustion Method

Nanoparticle Ni1−xZnx Fe2O4 (x=0.35,0.45) samples were prepared successfully via microwave assisted combustion method. Synthesis of nanosize materials at a low temperature using a domestic microwave oven is the unique feature of this method and is being tried for the first time to produce NiZn ferrites. Single-phase formation of the samples was confirmed from X-ray analysis and IR spectrum. XRD data reveals that lattice parameter increases with Zn content ‘x’. Particle sizes calculated from XRD analysis are in good agreement with TEM results. Extent of spin canting at octahedral B-site is deduced from Yafet–Kittel angles. Surface properties and reduced particle size affects the Curie temperature.

Microwave assisted combustion synthesis of CdFe2O4: Magnetic and electrical properties

CdFe2O4 particles were synthesized by the microwave assisted combustion method using two different fuels—glycine and urea. Microwave heating provides higher chemical yield within a minute. The synthesized particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), ac impedance spectroscopy, vibrating sample magnetometry (VSM) and electron spin resonance (ESR) methods. XRD analysis shows the cubic structure of CdFe2O4. The high and low frequency absorption bands of CdFe2O4 were found using FTIR analysis. Spherical morphology was revealed from the SEM images. ESR and VSM measurements reveal the antiferromagnetic behavior of CdFe2O4. The electrical conductivities of CdFe2O4 synthesized using glycine and urea are 6.5×10−7Scm−1 and 4.7×10−8Scm−1 respectively at 240oC. At elevated temperatures an occurrence of increase in conductivity was observed, which indicates the semiconducting behavior of CdFe2O4. The dielectric spectral analysis reveals that dielectric constant of CdFe2O4 decreases with frequency and increases with temperature.

Synthesis and characterization of Mo-doped SrFeO 3− δ as cathode materials for solid oxide fuel cells

This paper demonstrates the potential application of Mo-doped SrFeO 3− δ perovskites as new cathode materials for solid oxide fuel cells (SOFCs). SrFe 1− x Mo x O 3− δ ( x = 0, 0.05, 0.1, 0.2 and 0.25) perovskite materials have been synthesized by a microwave-assisted combustion method. By doping with Mo, the electrical conductivity of the doped SrFeO 3− δ in air is reduced with increasing amounts of Mo. At 800 °C, the conductivity drops from about 62 to 22 S cm −1 when the doping level is increased to 25%. According to X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR) results, a decrease in the concentration of charge carrier Fe 4+ ions may account for the decrease in electrical conductivity. In contrast, the resistance to sintering and tolerance to reduction of SrFeO 3− δ are improved by Mo-doping. Additionally, the thermal expansion coefficient at 800 °C drops from 40.8 × 10 −6 K −1 for SrFeO 3− δ to 25.7 × 10 −6 K −1 for SrFe 0.8Mo 0.2O 3− δ and 20.9 × 10 −6 K −1 for SrFe 0.75Mo 0.25O 3− δ . This significant decrease in the thermal expansion coefficient makes Mo-doped SrFeO 3− δ materials attractive as cathode candidates for SOFCs. Finally, a relatively low polarization resistance of 0.074 Ω cm 2 is obtained for SrFe 0.8Mo 0.2O 3− δ at 800 °C in air.

Stabilization of intrinsic defects at high temperatures in ZnO nanoparticles by Ag modification

The stabilization of defects in ZnO at high temperatures has been investigated. The properties of unmodified and modified ZnO nanoparticles (NPs) with 2at.% of Ag prepared by microwave assisted combustion method, have been systematically studied using X-ray diffraction (XRD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and photocatalytic activity measurements. Though the XRD data shows a marginal shift in the ZnO peak position upon Ag addition, the amount of shift does not change with annealing temperatures. The PL data reveals that the defect mediated visible emission intensity of unmodified ZnO NPs increases with increase in the annealing temperature, whereas it remains almost unchanged in Ag–ZnO. This study clearly establishes that silver is an efficient stabilizer of intrinsic defects in ZnO at high temperatures. This is further supported by the core and valence band XPS spectra.

Simple and rapid synthesis of Cadmium Oxide (CdO) nanospheres by a microwave-assisted combustion method

A simple and rapid microwave-assisted combustion method was developed to synthesize CdO nanospheres (CNS). The study suggested that the application of microwave heating to produce the homogenous CNS was achieved in a few minutes. The structure and morphology of the as-prepared CNS were investigated by means of X-ray diffraction (XRD), Fourier transforms infrared spectra (FT-IR), high resolution scanning electron microscopy (HR-SEM), Energy Dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), diffused reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. The XRD confirmed the formation of face centered cubic structure of CdO. The formation of CdO phase is also confirmed by FT-IR. The formation of spherical hollow nanospheres was confirmed by HR-SEM and TEM and their possible formation mechanisms were also tentatively proposed. The optical properties were determined by DRS and PL spectra.

Perovskite Sr 2Fe 1.5Mo 0.5O 6− δ as electrode materials for symmetrical solid oxide electrolysis cells

Perovskite Sr 2Fe 1.5Mo 0.5O 6− δ (SFM) has been successfully prepared by a microwave-assisted combustion method in air and employed as both anode and cathode in symmetrical solid oxide electrolysis cells (SOECs) for hydrogen production for the first time in this work. Influence of cell operating temperature, absolute humidity (AH) as well as applied direct current (DC) on the impedance of single cells with the configuration of SFM|La 0.9Sr 0.1Ga 0.8Mg 0.2O 3 (LSGM)|SFM has been evaluated. Under open circuit conditions and 60 vol.% AH, the cell polarization resistance, R P is as low as 0.26 Ω cm 2 at 900 °C. An electrolysis current of 0.88 A cm −2 and a hydrogen production rate as high as 380 mL cm −2 h have been achieved at 900 °C with an electrolysis voltage of 1.3 V and 60 vol.% AH. Further, the cell has demonstrated good stability in the long-term steam electrolysis test. The results showed that the cell electrolysis performance was even better than that of the reported strontium doped lanthanum manganite (LSM) – yttria stabilized zirconia (YSZ)|YSZ|Ni–YSZ cell, indicating that SFM could be a very promising electrode material for the practical application of SOEC technology.

Structural and magnetic properties of Co xZn 1−xFe 2O 4 nanocrystals synthesized by microwave method

Microwave assisted combustion method was used to produce nanocrystalline cobalt doped zinc ferrite, Co x Zn 1− x Fe 2O 4, from stoichiometric mixture of (Co(NO 3) 2·6H 2O), (Fe(NO 3) 3·9H 2O), (Zn(NO 3) 2·6H 2O), and urea (CO(NH 2) 2) as a fuel. The structural, morphological and magnetic properties of the products were determined by X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) respectively. The average crystallite sizes obtained from XRD were between 35 and 39 nm. Magnetization measurements indicate that samples with less Co content have superparamagnetic behavior at room temperature. When the Co substitution increases the saturation magnetization due to the magnetic character of the Co cations substituting the non-magnetic Zn and coercivity also increase due to anisotropic nature of cobalt. The Co x Zn 1− x Fe 2O 4 nanocrystals exhibit typical features of an assembly of magnetic particles with a distribution of blocking temperatures and indicate the spin-glass behavior.

Microwave synthesis and characterization of Zn-doped nickel ferrite nanoparticles

Microwave assisted combustion method was used to synthesize nanocrystalline Zn x Ni 1− x Fe 2O 4 from a stoichiometric mixture of corresponding metal nitrates and urea powders. The structural, chemical and magnetic properties of Ni–Zn ferrite was determined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (FTIR), vibrating sample magnetometry (VSM) and DC conductivity measurements. Results showed that the material was spinel structure with a high purity with an estimated crystallite size of ∼20 nm by X-ray line profile fitting. TEM analysis showed necked near-spherical particles with an average size of ∼20 nm, reflecting highly crystalline nature of these nanoparticles. Magnetic properties showed anomalities as the Zn doping level increased. This has been explained and attributed to the relative positions of Ni, Zn, and Fe ions in the crystal lattice.