Microwave Combustion Method Research Articles

T58EVALUATION OF POLYGENIC RISK SCORE PERFORMANCE IN AN ADMIXED BRAZILIAN COHORT

Nanocrystalline of ZnAl2O4 spinel was synthesized by employing the microwave combustion method. Different new spinel compositions of formula Zn1-xFexAl2O4, (0.0 ≤ x ≤ 1.0) were prepared by substitution of Zn ions with Fe ions. The as-synthesized resultant material ZnAl2O4 with spinel structure as well as Zn1-xFexAl2O4 compositions were characterized by Energy Dispersive X-ray and X-ray diffraction. Morphology and particle size evaluation of the nanoparticles were characterized by transmission electron microscopy images. The optical absorption spectra and the magnetization were measured at room temperature for each Fe ratio. The substitution effect of Fe ions on the optical and magnetic properties of the original spinel was studied. The optical absorbance showed that the optical band gap decreased with increasing Fe ratio.

Optical, electrochemical and current−voltage characteristics of novel coumarin based 2,4-dinitrophenylhydrazone derivatives

A series of novel 2,4-dinitrophenylhydrazone derivatives of coumarins (DNP1−DNP3) have been synthesized by novel method and characterized by spectroscopic techniques and were used as photosensitizers on zinc nanocones, which were prepared by microwave combustion method. Optical (linear and nonlinear), electrochemical and current−voltage (I–V) characteristics of dyes and dyes sensitized zinc nanocones were evaluated. In addition, the global chemical parameters were calculated. The results revealed that, synthesized dyes possess good light absorbing capability and well matched frontier molecular orbital (FMO) energy levels with conduction band (CB) of zinc nanocones. Among the synthesized coumarin derivatives, DNP3 has smallest band gap of 2.24 eV, highest ɛ value of 1, 00,000 M−1cm−1, larger NLA coefficient of 0.055 (cmW−1), least hardness value of 0.78 eV and highest Voc value of 0.98 V. Moreover, it exhibits better optical power limiting behavior. The enhanced I–V response of the sensitized nanocones in presence of light implies that the synthesized dyes are good photosensitizers.

Magnetically Separable Zinc Ferrite Nanocatalyst for an Effective Biodiesel Production from Waste Cooking Oil

ZnFe2O4 nanocatalysts synthesized by microwave combustion method is employed for biodiesel production from waste cooking oil (WCO). The zinc ferrite samples are prepared by varying the microwave power from 500 to 1500 W. The nanocatalysts are characterized by XRD, FTIR, DRS, HR-SEM and VSM techniques. Transesterification of WCO are investigated and maximum biodiesel yield of 98.6% is achieved with 4 wt% of ZnFe2O4 nanocatalyst (ZF-1500 sample), methanol/oil molar ratio of 21:1, reaction temperature about 60 °C and reaction time 1 h. The nanocatalyst (ZnFe2O4) was reused at least for 10 times. The activation energy (Ea) and frequency factor (A) is calculated to be 59.4 kJ mol−1 and 1.66 × 108 min−1 respectively. The thermodynamic parameters ∆H and ∆S were found to be 88.76 kJ mol−1 and − 0.096 kJ mol−1 K−1. The positive values of ∆G for transesterification process is found to be non-spontaneous and endergonic.

Application of microwave irradiation for fabrication of sulfated ZrO2\u2013Al2O3 nanocomposite via combustion method for esterification reaction: process condition evaluation

The zirconia–alumina nanocatalyst was prepared using microwave combustion method, and the effects of alumina/zirconia ratio, fuel-to-oxidizer ratio, and calcination temperature on its structural and chemical performance were examined. Furthermore, the most suitable synthesized nanocatalyst was impregnated using different dosages of sulfate group to improve the activity of the sample for the esterification reaction. The results revealed that there was a significant improvement in the crystalline structure of alumina and zirconia for the samples having the alumina/zirconia ratio of 2. It was also noted that some amorphous structures were observed for low fuel dosages, while the activity of the sample was reduced with higher fuel consumption than the stoichiometric ratio, which can be attributed to the increase in the crystallite size and formation of different alumina phases. Based on calcination results, non-considerable changes were observed in the morphology and activity of the catalyst. It can be concluded that the solution combustion method is suitable for nanocatalyst preparation without any requirement of further thermal treatment. In addition, the activity of the sample was enhanced by impregnation with H2SO4 where the conversion of 91.6% was achieved. The catalyst showed high reusability at least for seven times as well as high stability of zirconia–alumina as a support.Graphical abstract

Structural, magnetic and electrochemical characterizations of Bi2Mo2O9 nanoparticle for supercapacitor application

In this present work, bismuth molybdate (Bi2Mo2O9) nanoparticles (NPs) were prepared by microwave combustion method using urea as the fuel. The phase formation and purity of the product was identified by powder X-ray diffraction (XRD). Fourier transform-infrared (FT-IR) analysis was adopted to record the functional group of Bi2Mo2O9 NPs. The morphology, purity, size and elemental composition of the sample were confirmed by Scanning electron microscope (SEM), elemental mapping, energy dispersive X-ray (EDX) analysis and High-Resolution transmission electron microscope (HR-TEM) technique respectively. The UV–visible and photoluminescence (PL) spectra were used to examine optical and electronic behavior of the prepared sample at room temperature (RT). The chemical bonding of Bi2Mo2O9 NPs was studied by Raman spectroscopy. The magnetic properties of Bi2Mo2O9 NPs were examined by vibrating sample magnetometer (VSM) at RT. The particle size distribution was examined by X-ray Photoelectron spectroscopy (XPS). The Electrochemical (EC) properties of Bi2Mo2O9 NPs were investigated by Cyclic voltammetry (CV), Galvanostatic charge/discharge (GCD) and Electrochemical impedance spectral (EIS) studies. The specific capacitance (Cs) of prepared Bi2Mo2O9 NPs is 197 F/g at 0.4 A/g with excellent cycle stability of 94% specific capacitance after 1000 cycles. Hence, the results of electrochemical characteristics exhibits excellent performance and have potential application of electrode for energy storage systems.

Syntheses of new spinels Zn1-xFexAl2O4 nanocrystallines structure: Optical and magnetic characteristics

Nanocrystalline of ZnAl2O4 spinel was synthesized by employing the microwave combustion method. Different new spinel compositions of formula Zn1-xFexAl2O4, (0.0 ≤ x ≤ 1.0) were prepared by substitution of Zn ions with Fe ions. The as-synthesized resultant material ZnAl2O4 with spinel structure as well as Zn1-xFexAl2O4 compositions were characterized by Energy Dispersive X-ray and X-ray diffraction. Morphology and particle size evaluation of the nanoparticles were characterized by transmission electron microscopy images. The optical absorption spectra and the magnetization were measured at room temperature for each Fe ratio. The substitution effect of Fe ions on the optical and magnetic properties of the original spinel was studied. The optical absorbance showed that the optical band gap decreased with increasing Fe ratio.

Selectivity and efficient Pb and Cd ions removal by magnetic MFe2O4 (M=Co, Ni, Cu and Zn) nanoparticles

Spinel ferrite MFe2O4, (M = Co, Ni, Cu and Zn) nanoparticles (NPs) were prepared by microwave combustion method using metal nitrates as precursors, in addition to urea as fuel. Rietveld analysis of X-ray diffraction patterns indicates the formation of single phase for NiFe2O4 and ZnFe2O4, while (α-Fe2O3 and CuO) phases precipitate for CoFe2O4 and CuFe2O4, respectively. After annealing 800 °C for 16 h, single cubic CuFe2O4 phase is obtained. SEM images show spherical/undefined shaped particles at the nanoscale with broad particle size distribution and high level of agglomeration. Magnetisation-field (M-H) curves reveal ferromagnetic behaviour for CoFe2O4, NiFe2O4 and CuFe2O4, and superparamagnetic behaviour for ZnFe2O4. Interestingly, after annealing CuFe2O4 shows a superparamagnetic behaviour due phase tetragonal-cubic phase transformation. Saturation magnetization, remanence and coercivity slightly change after annealing, except for CuFe2O4, due to phase transformation from tetragonal to cubic; Ms decreases abruptly from 25.97 to 1.685 emu/g. The as-obtained spinel ferrite nanopowders are tested for two toxic metal ions removal from aqueous solutions; Cadmium (Cd2+) and lead (Pb2+) with different concentration (5, 10, 20 and 30 mg) and pH (2, 12). The maximum adsorption capacities are found at the lowest concentration (5 mg) and at alkaline medium (pH 12). The as-prepared magnetic nanoparticles demonstrate enhanced efficiency for both Cd2+ and Pb2+, with maximum adsorption capacity of 69.4 and 47.1 mg/g, respectively. Interestingly, the nature of metal M has a direct influence on selectivity, CoFe2O4 toward Cd2+ while ZnFe2O4 toward Pb2+.

Structure, optical and varying magnetic properties of insulating MCr2O4 (M= Co, Zn, Mg and Cd) nanospinels

Chromite nanospinels of MCr2O4 (M = Co, Zn, Mg and Cd) have been synthesized using a microwave combustion method. The spinel phase and average particles size have been investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Both XRD and TEM reveal an overall average particle size of about 12 nm. UV–Vis optical absorbance measurements at room temperature indicate common wide optical energy gap of about 3.1–3.4 eV. Magnetization processes have been studied via precise field cooled (FC) and zero-field cooled (ZFC) magnetization measurements. The magnetic transition temperatures found in the nanoparticles are slightly below those of corresponding bulk crystals. Survived spiral spin textures below ∼26 K and coexisting spin-glassy state are observed in the Néel-type ferrimagnetic CoCr2O4 nanocrystals with Curie temperature of 92 K. While the antiferromagnetic state of chromites with nonmagnetic divalent cations is observed in ZnCr2O4 nanocrystals below Néel temperature of 11 K, it is significantly suppressed in MgCr2O4 and CdCr2O4 nanocrystals of identical average particle size. Our results indicate increased surface spins contribution with increasing lattice parameter. ESR linewidth and resonance field of MCr2O4 also show M-cation type dependence. The coexisting spin-glassy-like state in long-range ordered CoCr2O4 and a possible superparamagnetic state in MCr2O4 (M = Zn, Mg and Cd) nanospinels are discussed as finite-size and Cr-Cr separation effects.

A Novel Approach for Fabricating LaMnO3 Thin Films Using Combined Microwave Combustion and Pulsed Electron Deposition Techniques

LaMnO3 (LMO) nanopowder was synthesized by the microwave combustion method using glycine and nitrate salts of La and Mn as precursors. The as-prepared LMO powder was pressed at high pressure and annealed at 1000°C for 8 hours to make a target for thin film deposition. The structural and elemental analysis was obtained by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). Thin films of LMO were fabricated using pulsed electron deposition (PED) at room temperature. The effects of discharge voltage and oxygen/argon flux ratio on the produced thin films were studied. The study shows that stoichiometry and structure of the target was preserved well in the thin films prepared with a discharge voltage from 14 to 15 kV, while the oxygen/nitrogen flux ratio did not show a clear effect on the quality of thin films.

Rapid synthesis of size-tunable transition metal carbide nanodots under ambient conditions

We develop a microwave combustion method for rapid (∼2 min) synthesis of size-tunable transition metal carbide nanodots under ambient conditions.

Study on the effect of Zn2+ doping on optical and electrical properties of CuO nanoparticles

The present work outlines the synthesis of CuO and Zn-CuO nanoparticles via microwave combustion method using urea as a fuel. The structural, optical and electrical properties of the CuO and Zn-CuO nanoparticles were systematically characterized through UV–Visible spectroscopy (UV–Vis), Field-emission scanning electron microscopy (FE-SEM), Photoconductivity technique (I-V study), X-ray diffraction studies (XRD), Transmission electron microscopy (TEM) and Energy dispersive analysis X-rays spectrometer (EDAX). The average crystalline size and micro-strain of pure CuO and Zn-CuO nanoparticles were calculated using Debye-Scherrer and William-Hall (W-H) plot methods. The crystalline size was found to be decreased with increase in the concentration of Zn2+ up to 6 mol% and a further increase in the Zn2+ concentration resulted in the formation impurity phase. Field emission scanning electron micrographs show the monoclinic rod-like structure of CuO and Zn-CuO nanoparticles. Energy dispersive X-ray spectra display the existence of Zn2+ in Zn-CuO nanoparticles. The optical band gap values of CuO and Zn-CuO nanoparticles were determined by optical absorption method and the results show a slight decrease in the optical band gap with Zn2+ doping. Electrical properties of CuO and Zn-CuO films were performed using I-V characterization studies and the results shown that the enhancement of photocurrent is more in UV-light as compared to dark.

Structural and Magnetization Studies of Cobalt Ferrite Nanoparticles Synthesized by the Microwave-Combustion Method

Structural and Magnetization Studies of Cobalt Ferrite Nanoparticles Synthesized by the Microwave-Combustion Method

Synthesis and magnetic properties of spinel Zn1−xNixFe2O4 (0.0 ≤ x ≤ 1.0) nanoparticles synthesized by microwave combustion method

Nanoparticles of Zn1−xNixFe2O4 (x = 0.0–1.0 in step of 0.2) ferrites are synthesized by microwave combustion method using glycine as a fuel. The structure, site occupancy and ferrimagnetic behavior have been characterized by X-ray diffraction (XRD), Mössbauer Spectroscopy (MS) and Vibrating Sample Magnetometer (VSM). Special emphasis is given to the information provided by each of these techniques concerning the impact of the site occupancy on the magnetic properties. The results reveal the formation of single phase cubic spinel with crystallite sizes in the range of 30–42 nm. The lattice constants and the lattice strains decrease gradually with increasing Ni-content. Two well-defined Mössbauer sextets in the spectra at 78 K belong to octahedral [B] and tetrahedral (A) sites, respectively, confirming the formation of Zn1−xNixFe2O4 spinel. The isomer shift (δFe) values were assigned to Fe3+ ions distributed in both A and B sites. The quadrupole splitting (Δ) values showed also that the orientation of the magnetic hyperfine field (Hint) with respect to the principle axes of the electric field gradient (EFG) is random. The nanosize samples In the presence of an externally applied magnetic field prepared exhibit the hysteresis loops of the ferrimagnetic nature. The value of saturation magnetization increases with introducing Ni up to x = 0.8 and then it decreases. The magnetic data parameters of this structure are discussed as a function of the content of Ni ions.

Catalytic studies of NiFe2O4 nanoparticles prepared by conventional and microwave combustion method

A simple and rapid synthesis has been developed to synthesize NiFe2O4 nanoparticles with tunable optical, magnetic and catalytic properties by using Hibiscus rosa sinensis plant extract in the current study. The crystalline structure of the synthesized NiFe2O4 nanoparticles was confirmed by X-Ray diffraction (XRD) and Rietveld refinement analysis. Morphological, elemental, magnetic and optical properties of the synthesized nanoparticles were interpreted by fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), UV–Visible diffused reflectance spectroscopy (UV-DRS), photoluminescence (PL) studies, and vibrating sample magnetometer (VSM). XRD analysis showed the single phase crystalline nature with average crystallite size of 50–70 nm. SEM and EDX analysis recognize the spherical shape nanoparticles and phase purity of the samples. The optical band gap is determined using UV-DRS spectra and is observed to decrease with increasing the calcination temperature. VSM studies obviously demonstrate the ferromagnetic property of the samples. The value of saturation magnetization has decreased with an increase in the calcination temperature and the coercivity is decreased. Additionally, NiFe2O4 nanoparticles were investigated for the catalytic reduction capability for different dyes like Rhodamine-B (Rh-B), Methylene blue (MB), Rose Bengal (RB), and Congo red (CR). It is found that the dye solution was degraded with increasing irradiation time. Hence, the prepared nanoparticles have been used as high potential catalysts for the reduction of organic dyes in the application of waste water treatment. NiFe2O4 is an active agent in catalyzing the oxidation of glycerol to formic acid with good conversion percentage and high selectivity. This catalytic system in the polar solvents, such as, acetonitrile provides the enhanced conversion results. The very important role played by a variety of reaction parameters in deciding the catalytic effectiveness is well established and every parameter has an optimal value to acquire the maximum catalytic activity.

Relative Role of Particle Size and Shape on the Magnetic and Catalytic Behavior of Nanozinc Chromite

The purpose of this study is to define an effective synthesis for spinel-type zinc chromite (ZnCr2O4) nanoparticles by a simple microwave combustion method. The synthesized material was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and from optical properties. A magnetic property for the material was examined through the vibrating sample magnetism. The distribution of the external magnetic lines of force and the self-generated magnetic field of ferromagnetic materials was taken into account in the presence of an external magnetic field. Zinc chromite showed good performances in catalytic oxidation, and the role of particle size and shape is highlighted.

Sinterability, physico-mechanical, electrical and magnetic properties of CoxMg1-xAl2O4 synthesized by microwave combustion method

The aim of this work is to study the influence of cobalt content on the properties of sintered CoxMg1-xAl2O4 (x = 0–1) spinel synthesized by microwave combustion technique. To optimize the suitable sintering temperature for getting sintered spinel with improved properties, the sinterability was investigated at 1400, 1500 and 1600 °C. Phase composition of sintered spinel was examined by x-ray analysis while bulk density and apparent porosity were determined by water displacement method according to Archimedes principle. Microstructure of spinel sintered at 1600 °C was investigated by scanning electron microscope. Moreover, compressive strength, electrical conductivity, electrical resistivity and magnetic properties of sintered spinel materials were also measured. The results revealed that an improvement in physical, mechanical, electrical and magnetic properties of spinel sintered at 1600 °C was achieved. Co0.2Mg0.8Al2O4 specimen exhibited lower porosity and higher compressive strength as well as higher electrical conductivity among other sintered compositions. The saturation magnetization was increased with increasing the cobalt content in spinel.

Structural, morphological and magneto-optical properties of CuMoO4 electrochemical nanocatalyst as supercapacitor electrode

Copper molybdate (CuMoO4) nanoparticles (NPs) were synthesized by microwave combustion method and urea act as the fuel. The formation of nanocrystalline structure was confirmed by X-ray powder diffraction (XRD). The chemical composition of the CuMoO4 NPs was investigated by Fourier transform infrared (FT-IR) spectroscopy. Scanning electron microscope (SEM) associated with energy dispersive X-ray (EDX) was used to investigate morphological and elemental composition of the prepared sample. The morphology and particle size of sample were investigated by high-resolution transmission electron microscope (HR-TEM) analysis. The optical and electronic defects were confirmed by the UV-Vis absorption and photoluminescence (PL) spectroscopy at room temperature (RT). The magnetic behavior was analyzed by vibrating sample magnetometer (VSM) analysis recorded at RT. The X-ray Photoelectron spectroscopy (XPS) was used to analyze the chemical state of the elements in the prepared sample. The electrochemical behavior was examined by cyclic voltammetry (CV), galvanostatic charge and discharge analysis (GCD) and electrochemical impedance spectroscopy (EIS). The presence of redox pairs is showed in CV curves and along with the EIS data showed the supercapacitor nature. The GCD analysis displayed discharge curves and a high specific capacitance of ~ 127 F/g was acquired at a stable discharge current density (1 mA/cm2). The cyclic stability analysis showed capacitance retention of about 82.5% after 1000 cycles, proposing the potential application of CuMoO4 in energy storage devices.

A study of the doped zinc-ferrite nanoparticles with bismuth

In this article, the doped zinc-ferrite nanoparticles with bismuth by using glycine as a fuel have been made by using the microwave combustion method. After synthesizing the ZnFe2−xBixO4 samples with x = 0.0, 0.02, 0.04, 0.06, 0.1, 0.15, dielectric properties such as dielectric constant, dielectric loss factor, and also conductivity were measured by using a LCR meter in the frequency range of 0–10 MHz. The results showed that the dielectric constant decreases with increasing the frequency; then its value reaches a constant magnitude. Also we considered the structural, morphological and magnetic properties of nanoparticles by using the x-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM), respectively. The optical properties of the sample were studied by using the visible-ultraviolet light (UV–vis) spectroscopy. The results of the XRD patterns showed no additional peak was observed in the samples, and this revealed that the samples are single-phase. Also these results showed that the lattice parameter increases with increasing the bismuth concentration. SEM results showed an ascending trend in the size of the nanoparticles. Also, considering the VSM results characterized that increasing the bismuth amount leads to lower saturation magnetization, coercivity and remaining magnetization of the samples. The results of UV–vis spectroscopy showed that increasing bismuth amount can increase the sample optical band gap.

A Facile Route to the Synthesis of Zn-Doped CdO Nanostructures and a Comparative Investigation on Humidity-Sensing and Photocatalytic Applications

Pure and zinc-doped CdO nanoparticles were synthesized via a novel microwave combustion method. The structural, morphology, chemical composition and optical properties of the samples were systematically investigated. The powder x-ray diffraction patterns reveal that both pure and doped samples are of a single crystalline nature with a cubic Fm3m CdO structure. Spherical-shaped morphology with an average diameter of around 25–35 nm was observed by field emission scanning electron microscope analysis. Optical studies showed that Zn2+-doped CdO decreases the band gap energy (Eg) from 3.42 eV to 3.12 eV. The sensor was produced via an extremely simple process in which Zn-CdO powders were deposited directly into an interdigital electrode immersed in a chemical bath under ambient conditions. The proposed sensor showed almost linear behavior within a chosen range of humidity (between 10% and 90% RH) and fast response (25 s) and recovery time (20 s). Our reproducible experimental results exhibited that Zn-doped CdO nanoparticles have a great potential for humidity-sensing applications in room temperature operations. The samples were further investigated for their photocatalytic activity by degradation of Rhodamine B and Methyl orange under UV light irradiation. The improved photocatalytic mechanism by Zn doping is also discussed in detail.

Preparation and Characterization of Nanocopper Ferrite and Its Green Catalytic Activity in Alcohol Oxidation Reaction

A new type of magnetic material copper ferrite (CuFe2O4) is successfully manufactured through microwave combustion method. Starch has been tested as a single fuel in this combustion-based synthesis of copper ferrite by using different fuel compositions and equivalence ratios (fuel/oxidant). The formed copper ferrite is characterized by X-ray diffraction analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. Magnetic properties of the prepared copper ferrite are analyzed by vibrating sample magnetometer (VSM). Surface area is measured by the nitrogen adsorption/desorption isotherms. A detailed examination of the morphology of the material in various microwave method-catalyzed processes shows that they provide an optimum catalytic activity due to a combination of lower crystal size and higher activity.