Microwave-assisted Combustion Route Research Articles

Effect of Mg doping on dielectric properties of ZnO nanoparticles synthesized by microwave-assisted combustion route

The primary aim of this research work is to study the dielectric properties of nanoscale ZnO and Mg-doped ZnO nanoparticles (NPs). The microwave-assisted combustion technique was used to synthesize ZnO and Mg-doped ZnO NPs (2, 4, and 6 atomic % of Mg). XRD (X-ray diffraction), FTIR (Fourier transform infrared) and SEM (Scanning electron microscope) methods were used to characterize the materials. From the XRD pattern, the phase confirmation and crystallite size of ZnO and Mg-doped ZnO NPs were estimated. The study of dielectric properties such as dielectric loss and permittivity, impedance and AC conductivity were observed in the range of frequency (1–106 Hz). The permittivity of ZnO and 6% Mg-doped ZnO showed an enhanced dielectric property than other doped materials at higher frequency. The additional mobile carriers added to the material as a result of raising the percentage of doping resulted in an increase in the material's dielectric loss. The hopping and tunnelling mechanism, which may be attributed to the migration of electrons into the conductive network formed by the crystallites of 6% Mg-doped ZnO and ZnO NPs, caused progressively increase in the values of AC conductivity of doped nanoparticles as the frequency range was increased. The impedance (real and imaginary) was decreased with increase in the amount of Mg (in terms of atomic %).

Microwave-assisted design and fabrication of rare earth doped NiMoO4: An admirable electrode material in redox electrolytes with excellent power density for high-end energy storage systems

In the recent advancement of energy storage, electrode materials delivering high energy density and the capability to deliver noteworthy power compared to batteries are considered to be promising materials. In this study, hierarchical-structured NiMoO4 and various concentrations of Ce rare earth metal doped NiMoO4 materials have been synthesized by microwave-assisted combustion route. Their structural, morphological, and spectroscopical characteristics have been studied using different characterization and analytical techniques. The α to β-NiMoO4 phase transformation with the same crystal structure has been confirmed after the addition of 5% Ce dopant. The crystallite size, cell volume, and particle size of the β-NiMoO4 seems to be minimal with maximum dislocation density compared to the prepared α-NiMoO4 samples. The initial nanospheres are clustered in different orientations to form different morphological structures. All the samples have been evaluated as electrodes for highly efficient electrochemical supercapacitors. The 5%-Ce doped NiMoO4 electrode has revealed an extraordinary supercapacitive performance showing excellent specific capacitance of 3101.12 Fg‐1 at 1 mA current with good retentivity of 97.65% after 5000 cycles in a three-electrode configuration, which is six times higher value than the prepared pristine NiMoO4 (478.78 Fg‐1). Besides, an asymmetric supercabattery device has been fabricated utilizing NiMoO4‐5% Ce electrode and activated carbon as positive and negative electrodes in a two-electrode configuration. It displayed a fascinating energy density of 29.2 W h kg−1 even at high current density of 5 mA. Prominently, the supercabatteries device showed an admirable 80.55% long-lasting cycling performance retained after 10,000 cycles.

Synthesis, Characterizations, and Magnetic Properties of Mixed Spinel Mg1-xZnxFe2O4 Ferrites

Mixed spinel Mg1-xZnxFe2O4 ferrites (where x = 0, 0.2, 0.4, and 0.6) nanoparticles were synthesized by using microwave-assisted combustion route. As-synthesized powdered samples were checked by XRD analysis, field emission-scanning electron microscopy, and vibration sample magnetometer to investigate the structural, morphology, and magnetic properties, respectively. XRD results exhibited that the crystallite size increases with the decrease of Zn+2 ion concentration for series of mixed spinel Mg1-xZnxFe2O4 ferrite expect x=0.2. All the mixed spinel Mg1-xZnxFe2O4 ferrite has different grain sizes with uniform distribution also presence voids in the samples. Pure magnesium ferrite has a lower net magnetization value but when magnesium ions (Mg+2) are replaced by zinc ions (Zn+2) then the value of saturation magnetization increases.

Rapid microwave-assisted combustion route for production of MFe2O4 (M = Zn, Ni, Co) nanoferrites for gas sensors view point

Nanocrystalline ZnFe2O4, NiFe2O4 and CoFe2O4 were prepared using rapid microwave assisted combustion technique. Single phase Nanocrystalline structure of ferrites confirmed by X-ray diffraction and Rietveld refinement. Fine powder of Nanocrystalline Zn, Ni and Co ferrites resulted from rapid synthesis route were used for gas sensor fabrication in the form of thick film by screen printing method. Scanning electron microscopy was used to study surface of the sensing element and to study the surface morphology of the sensor. The gas sensing responses of the indigenously built sensor were analyzed by measuring the resistance of sensing element in presence and in absence of LPG. Amongst the studied sensors, NiFe2O4 thick film sensor showed superior response.

Role of Glycine-to-Nitrate Ratio in Physical and Magnetic Properties of Zn-Ferrite Powder

We report the influence of different glycine-to-nitrate ratios on the physical and magnetic properties for synthesized zinc-ferrite by microwave-assisted combustion route. Phase impurity and surface morphology investigated with XRD analysis and field emission- scanning electron microscopy, indicated that spinel structure were formed.Average particles size increased with the decrease of glycine to nitrate ratio. Magnetic measurement results indicated that high values of saturation magnetization were produced with low glycine/nitrate ratio. Optical properties of the investigated ferrites exhibited photo absorption from UV to visible region with energy gap values that decreased with the decrease of glycine-to-nitrate ratio. Mainly two broad metal-oxygen bands for zinc-ferrite were seen in FT-IR spectra.

Effect of Zn doping on dielectric properties of MgO nanoparticles synthesized by microwave-assisted combustion route

The composite insulating materials are major parts of various electrical devices because of their synergetic effect. The primary aim is to study the dielectric properties of nanoscale MgO and Zn-doped MgO nanoparticles (NPs). MgO and a series of (2, 4 and 6%) Zn-doped MgO NPs were synthesized by microwave-assisted combustion route. The samples were characterized through various techniques and the confirmation of phases and crystallite sizes of MgO and Zn-doped MgO NPs were calculated from XRD pattern. The study of dielectric permittivity, dielctric loss, AC conductivity and impedance were investigated in the frequency range of 1–106 Hz at room temperature. The dielectric permittivity and dielectric loss of the materials increased with increase in the doping of Zn into MgO NPs at lower frequency. The AC conductivity values of doped nanoparticles increased gradually with increase in the frequency range due to the hopping and tunneling mechanism. The real and imaginary impedance were found to decrease with increase in the Zn doping percentage.

Investigations on structural, optical, dielectric, electronic polarizability, Z-scan and antibacterial properties of Ni/Zn/Fe2O4 nanoparticles fabricated by microwave-assisted combustion method

In this article, Ni0.5Zn0.5Fe2O4 nanoparticles (NPs) were synthesized by differing concentrations of fuel (lean, stoichiometric, and rich) via microwave-assisted combustion route. The effect of fuel content was used to explore their chemical, electrical, and nonlinear optical properties along with their antibacterial activity of the as-prepared Ni/Zn/ferrite NPs were studied. The XRD assures the cubic crystal structure of prepared NPs with no secondary phase. It is also clear that as lattice parameters increases, the mean crystallite size decreases as a change in fuel ratio. The optical energy bandgap values are estimated as 2.88, 3.28, and 3.0 eV, respectively. From the luminescence spectra, the Ni/Zn ferrite NPs exhibits strong green emission and weak violet emission color. The fuel ratio has a significant influence on the electronic polarizability properties of synthesized NPs. Closed and open aperture Z-scan technique reveals that the Ni/Zn ferrites NPs have self-defocusing nature, and reverse saturable absorption. The calculated values are NLA coefficients (10-5 cmW−1), NLR index (10−9 cm2W−1), and third-order NLO susceptibility χ(3) values of fuel lean (1.408 × 10−5esu), stoichiometric (2.75 × 10−6esu), and rich (2.634 × 10−5esu). Several identified microorganisms such as gram + Ve (S. aureus, B. cereus), and gram -Ve (P. aeruginosa, V. cholerae, and E. coli) have been tested for antibacterial activity against Ni/Zn ferrite nanoparticles. The ZOI values are 27 (lean), 24 (stoichiometric), and 25 mm (rich) which suggest great antibacterial activity against Pseudomonas aeruginosa gram-negative bacterium. However, this study shows excellent feasibility of applying prepared ferrite nanoparticles for optoelectronic devices and pharmaceutical processing applications.

Structural and spectroscopic studies of nanocrystalline Ni1−xMgxFe2O4 ferrites synthesized by a microwave-assisted combustion route

In this work, the synthesis of Ni1−xMgxFe2O4 (0 ≤ x ≤ 1.0) nanoparticles by a facile microwave-assisted combustion method is reported with detailed study of the structural and optical properties. By employing techniques of x-ray diffraction (XRD) with Rietveld refinement, transmission electron microscope (TEM, HRTEM, TEM-EDX), Fourier transform infrared spectroscopy (FTIR) and UV-Visible spectroscopy, the synthesized nanoparticles are characterized and introduced for further study of size-confined properties. Nanocrystals of a pure cubic spinel structured phase with average particle size of 20–40 nm were successfully synthesized in the whole range of x. In consistence with Vegard’s law for a solid solution lattice, the lattice constant increases linearly with the substitution for Ni2+ with the relatively larger Mg2+ cations. The Rietveld analysis of the observed XRD patterns reveals an inversed spinel structure in NiFe2O4 nanoparticles with a decreased inversion factor by Mg-substitution. The results of UV-Visible absorbance indicate a wide energy gap of about 3.6 eV for NiFe2O4 nanoparticles thatmonotonically tuned towards a narrow band gap by Mg-doping.

Microwave assisted combustion synthesis of photolumiescent ZnAl2O4:Eu nano powders

In the present study, ZnAl2O4:Eu nano particles were synthesized via microwave assisted combustion route using aluminium nitrate nonahydrate, and zinc nitrate hexahydrate as starting materials, and ethylene glycol, glycine, glucose and citric acid as fuels. Effect of different parameters such as calcination temperature, fuel type, oxidizer to fuel (O:F) ratio and Eu dopant concentration on the structure, microstructure, photoluminescence and optical properties was studied. Results showed that these parameters can strongly affect structure, microstructure, and consequently photoluminescent properties. As-synthesized samples were amorphous and must be post-heated up to 900 °C to form crystalline phase. Moreover, morphology of nano particles was sponge plate- like with using different fuels. Furthermore, photoluminesce emission at red region was observed by introducing Eu.

Nanoceria: A rare-earth nanoparticle as a promising anti-cancer therapeutic agent in colon cancer

The bioactivity and physical characteristics of CeO2 nanoparticles are significantly dependent on the type of the particle, particle size and defects. Herein, a facile and cost effective microwave-assisted combustion route was used to prepare pure CeO2 nanoparticles (NPs). The samples were thoroughly characterized by various techniques and tested as anti-cancer therapeutic agent in colon cancer. The structural investigations (X-ray Powder Diffraction) revealed the formation of single phase cubic fluorite-type structure of CeO2 with Fm-3m space group. Morphological analysis (FESEM), demonstrated the aggregation of irregular nanoparticles with grain size ~ 20–40 nm. To have more knowledge on the sample morphology, TEM and HRTEM images were taken. TEM image showed ceria NPs with squared shape and particle size in 50–95 nm range. Furthermore, HR-TEM micrographs confirmed the crystallinity of the CeO2 sample, which was explored by calculating the distance between the fringes in the corresponding Fourier transformed images. The BET specific surface area (SSA) of as-synthesized ceria nanoparticles, was observed to be 25 m2/g. UV–vis spectral analysis reveals that the direct band gap of CeO2 nanoparticles is about 2.8 eV.It was interesting to observe that, the as prepared NPs exhibit remarkable differential cytotoxicity towards healthy (BHK121, Baby Hamster Kidney cells) and human Colon cancer cells (HCT116). Nuclear fragmentation assay indicated clear DNA fragmentation in HCT116 cells, whereas intact nucleus was observed in normal cells, suggesting ceria induced apoptotic cell death in colon cancer cells. In sum, MACS generated ceria nanoparticles could uncover a new avenue in cancer therapy.

Mössbauer and magnetic studies of nanocrystalline zinc ferrites synthesized by microwave combustion method

Zinc ferrite nano-crystals were synthesized by a microwave assisted combustion route with varying the urea to metal nitrates (U/N) molar ratio The process takes only a few minutes to obtain Zinc ferrite powders. The Effect of U/N ratio on the obtained phases, particle size, magnetization and structural properties has been investigated. The specimens were characterized by XRD, Mossbauer and VSM techniques. The sample prepared with urea/metal nitrate ratio of 1/1 was a poorly crystalline phase with very small crystallite size. A second phase is also detected in the sample. The crystallite size increases while the second phase decrease with increasing the urea ratio. The saturation magnetization and coercivity of the as prepared nano-particles changed with the change of the U/N ratio. The powder with the highest U/N ratio showed the presence of an unusually high saturation magnetization of 16 emu/g at room temperature. The crystallinity of the as prepared powder was developed by annealing the samples at 700 ∘C and 900 ∘C. Both the saturation magnetization (Ms) and the remnant magnetization (Mr) were found to be highly dependent upon the annealing temperature. Mossbauer studies show magnetic ordering in the powder even at room temperature. The Mossbauer and the magnetic parameters of this fraction are different from the standard values for bulk zinc ferrite.

A simple microwave-assisted combustion synthesis and structural, optical and magnetic characterization of ZnO nanoplatelets

A simple microwave-assisted combustion route was used first time for the preparation of nanocrystalline ZnO nanoplatelets using dissolution of zinc nitrate as the oxidant and glycin as fuel. The structure, morphology and composition of the as-prepared samples were investigated by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray spectra (EDX). The XRD results confirmed the formation of single phase hexagonal wurtzite structure of ZnO and SEM pictures indicated that the sample includes the nanostructured nanoplatelets with the porous surface of the products. The optical properties were determined by a UV–vis spectrophotometer and the results showed that the as prepared ZnO nanoplatelets have larger band gap of 3.06eV. Vibrating sample magnetometer (VSM) was used for the magnetic property investigations and ZnO nanoplatelets indicated room temperature ferromagnetism which is intrinsic in nature and attributed to oxygen and/or Zn deficiencies as found in EDX results.

Impact of n-heptane as surfactant in the formation of CdO nanowires through microwave combustion

A microwave-assisted combustion route for the preparation of cadmium oxide (CdO) nanowire is carried and its characterization results are discussed. This method resembles a supportive way in the formation of CdO nanowire which is confirmed with the structure and morphological analysis carried for the prepared sample. Microwave combustion method is a cost effective and less time consumption to achieve CdO nanowires. The controlled shapes and size are attained due to microwave irradiation. Yielded sample is investigated with Fourier transformation infra-red (FTIR) spectra, X-ray diffraction (XRD) pattern, energy dispersive X-ray (EDX) spectra and transmission electron microscopy (TEM) with SAED pattern. The formation of CdO phase with a face centered cubic structure is confirmed from XRD spectra and the presence of CdO metallic bond is also confirmed with FTIR spectra. The formation of CdO nanowires is visualized through the TEM images and presence of elements is also recorded from EDX spectra.

Comparative study of microwave and conventional methods for the preparation and optical properties of novel MgO-micro and nano-structures

Magnesium oxide (MgO) was synthesised by a simple microwave-assisted combustion route without using any template, catalyst or surfactant. For the purpose of comparison, it was also prepared using conventional method. The as-synthesized MgO was characterized by powder X-ray diffraction (XRD), Fourier Transform infrared spectra (FT-IR), high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), Energy Dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. The XRD results confirmed the formation of cubic phase MgO. FT-IR was used to investigate the adsorption of water and CO 2 on MgO surface and confirm the formation of Mg-O phase. The formation of MgO micro cubes structures was confirmed by HR-SEM. The formation of MgO nanosheets was confirmed by HR-SEM and TEM and their possible formation mechanisms were also proposed. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra respectively. An attempt has been made to compare the lattice parameter and the PL intensity.

Synthesis and Characterization of Nanosized Dy-Doped of Ceria Developed by Microwave Assisted Combustion Route

Nanosized Ce1-xDyxO2-x/2 (DDC, x = 0.05—0.25 mol%) were synthesized by combustion routes induced by microwaves (MS) and compared with the same composition prepared by conventional (CS) method. The conventional and microwave sintering routes were also used to consolidate the pellets. The samples were characterized by X-ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and AC impedance spectroscopy. The as-combusted powders prepared by microwaves were found to be pure oxides with low crystallinity, and exhibited excellent sintering behavior. Highly dense DDC pellets with fine and homogeneously grown grains (400 nm) were achieved by microwave, while conventionally densified pellets had average grain size of 1100 −1400 nm. The ionic conductivity measured for pellet sintered by MS at 1050°C for 1 h is, σ550°C = 7.42 × 10−2 S/cm, Ea = 0.86 eV, and for CS at 1300°C for 5 h, is σ550°C = 9.79 × 10−3 S/cm, Ea = 1.05 eV.

Synthesis and magnetic characterization of Zn0.7Ni0.3Fe2O4 nanoparticles via microwave-assisted combustion route

We report on the synthesis of Zn0.7Ni0.3Fe2O4 nanoparticles via microwave assisted combustion route by using urea as fuel. XRD and FT-IR analyses confirm the composition and structure as spinel ferrite. The crystallite size estimated from XRD (16.4nm) and the magnetic core size (15.04nm) estimated from VSM agree well, while a slightly smaller magnetic diameter reflects a very thin magnetically dead layer on the surface of the nanoparticles. Morphological investigation of the products was done by TEM which revealed the existence of irregular shapes such spherical, spherodial and polygon. Magnetization measurements performed on Zn0.7Ni0.3Fe2O4 nanoparticles showed that saturation was not attained at even in the high magnetic field. The sample shows superparamagnetic behavior at around the room temperature and ferromagnetic behavior below the blocking temperature which is measured as 284K.

Structural and photo luminescent properties of uncapped nanocrystalline Cd 1− xZn xS solid solutions

Uncapped nanocrystalline Cd 1− x Zn x S (0.0 ⩽ x ⩾ 0.5) solid solution prepared by microwave assisted combustion route shows hexagonal to cubic phase transformation for even low doping of zinc up to 5 at.% as evident from the X-ray diffraction patterns and the selected area electron diffraction patterns. The solid solutions show a considerable shift in the optical absorption edge from ∼2.43 eV (CdS) to ∼2.73 eV for the equi-atomic composition (Cd 0.5Zn 0.5S). The blue emission in CdS shows effect of quantum confinement. The photo luminescence spectra of Zn lean compositions (up to 5 at.%) show emergence of a peak at λ ∼ 530 nm along with the blue emission features of CdS. However, solid solutions with higher zinc content (up to 50 at.%), show a systematic increase in the intensity of peak at 530 nm with a blue shift up to 30 at.% of zinc doping. Beyond 30%, a broad blue–green emission with full width at half maxima of ∼100 nm for Cd 0.5Zn 0.5S is observed.

Microwave assisted synthesis, characterization and humidity dependent electrical conductivity studies of perovskite oxides, Sm 1− xSr xCrO 3 (0 ≤ x ≤ 0.1)

The perovskite oxides, Sm 1− x Sr x CrO 3 (0≤ x≤0.1) were synthesized by a microwave assisted combustion route from the constituent metal nitrates and urea. The single-phase oxides were characterized by X-ray diffraction (XRD) and the lattice parameters were evaluated. The perovskite oxides were subjected to DC conductance measurements over the temperature range 100–300 °C in air atmosphere from which activation energies were determined. The current was found to increase linearly with the applied field and exponentially against temperature indicating the ohmic nature of the electrode contacts. The activation energy values for DC conductance were found to be in the range of 0.38–0.56 eV. DC resistance measurements as a function of relative humidity in the range of 5–98% RH were carried out on sintered discs at 25 °C under static conditions from which the sensitivity factor, S f ( R 5%/ R 98%) for SmCrO 3, Sm 0.95Sr 0.05CrO 3 and Sm 0.90Sr 0.10CrO 3 were calculated to be 2198, 2971, 4510, respectively. The response and recovery characteristics were studied for Sm 0.90Sr 0.10CrO 3, which exhibited good linearity and very narrow hysteresis loop.