Microwave-assisted Solution Combustion Synthesis Research Articles

Rapid fabrication of Ga-doped Li7La3Zr2O12 powder via microwave-assisted solution combustion synthesis

Rapid fabrication of Ga-doped Li7La3Zr2O12 powder via microwave-assisted solution combustion synthesis

Two-dimensional photocatalyst with highly efficient and stable visible light photocatalytic activity

Hex ammonium molybdate (AHM), ammonium nitrate (NH4NO3), and glycine were used as the precursors in a microwave-assisted solution combustion synthesis (WSCS) process to create foam-like MoO2 nanoparticles. Methodically investigated was the effect of the glycine/NH4NO3 ratio (=0.25, 0.50, 0.75, 1.0 and 1.25) on the finished goods. The findings indicate that the final morphologies and phases of the products are virtually influenced by the value of Φ. MoO2 nanoparticles measuring 20 to 30 nm can be successfully composited under the condition of Φ=0.50 to produce a foam-like result. The photocatalytic activity of foam-like MoO2 nanoparticles was tested with several pollutants. The results show that foam-like MoO2 nanoparticles have good degradability and stability. The photocatalytic mechanism and fabrication mechanism of foam-like MoO2 has been presented in detail. Using foam-like MoO2-based photocatalyst materials for energy transfer and environment protection is supported by this research.

Two-dimensional photocatalyst with highly efficient and stable visible light photocatalytic activity

Hex ammonium molybdate (AHM), ammonium nitrate (NH4NO3), and glycine were used as the precursors in a microwave-assisted solution combustion synthesis (WSCS) process to create foam-like MoO2 nanoparticles. Methodically investigated was the effect of the glycine/NH4NO3 ratio (=0.25, 0.50, 0.75, 1.0 and 1.25) on the finished goods. The findings indicate that the final morphologies and phases of the products are virtually influenced by the value of Φ. MoO2 nanoparticles measuring 20 to 30 nm can be successfully composited under the condition of Φ=0.50 to produce a foam-like result. The photocatalytic activity of foam-like MoO2 nanoparticles was tested with several pollutants. The results show that foam-like MoO2 nanoparticles have good degradability and stability. The photocatalytic mechanism and fabrication mechanism of foam-like MoO2 has been presented in detail. Using foam-like MoO2-based photocatalyst materials for energy transfer and environment protection is supported by this research.

Energy transfer mechanism of Eu2+, Mn2+Doped lithium aluminate phosphor: Synthesis, Hirshfeld surface analysis and optical study

The LiAlO2 phosphor doped with Eu2+ sensitizer ions and Mn2+ ions activator were synthesized by employing microwave-assisted solution combustion synthesis method (SCS), and structural correlation investigations were elaborated. The host material was characterized by XRD, FT-IR, SEM, TEM analysis and their spectroscopic studies by photoluminescence study. The structural correlation i.e., 3D Hirshfeld surface analysis and 2D fingerprint plots of the LiAlO2 phosphor were generated using crystal explorer-17 software in order to discuss strength of different bonds and their inter-contacts. The energy transfer from Eu2+ to Mn2+ ions through exchange interactions was explained by Dexter's exchange interactions. The energy transfer interactions are possibly due to dipole-dipole transitions was best demonstrated by linear fitting with n: 6 (R2 = 0.987). The chromaticity diagram explains the nature of the color spectrum of phosphor-based on their particular wavelengths. The energy transfer from Eu2+ ions to Mn2+ ions leads to wavelength tunable ability of the phosphor suitable for the development of warm white light LEDs.

Crystalline phase formation of Na2W2O7 using microwave-assisted solution combustion synthesis for photocatalytic degradation of organic pollutants from aqueous solutions

A novel combustion method, microwave assisted solution combustion (MASC), was first employed to synthesis Na2W2O7 nanoparticles, which were characterized by photoluminescence analysis (PL), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The PL of prepared samples demonstrated a green emission, which was not reported before for this product prepared using the combustion method. Also, to improve the luminescence and photocatalytic properties of these particles, europium element was doped on Na2W2O7 structure that the emission peak of host crystals was shifted to the red-light wavelength. Photocatalytic activities of the Na2W2O7 synthesized crystals were studied and the Genetic Algorithm (GA) method was used to optimize the photodegradation process using the response surface methodology (RSM). To recognize the advanced models adequacy and reveal good agreement between the offered model and the experimental data, statistical analysis of variance (ANOVA) was performed. Based on the results, technologically advanced catalytic treatment and models can be used effectively to remove organic pollutants consisting of AZO bonds from water supplies.

Suppression of coke formation during reverse water-gas shift reaction for CO2 conversion using highly active Ni/Al2O3-CeO2 catalyst material

The catalytic reduction of CO2 via reverse water-gas shift (RWGS) reaction is the most efficient way of CO2 valorization. In this work, the Ni/Al2O3-CeO2 catalyst was prepared by microwave-assisted solution combustion synthesis. XRD, TEM, N2 physisorption, and H2-TPR results show desired phase formation, small crystalline size, more developed porous structure with high surface area, and high levels of CO2 conversion. The catalyst shows excellent stability at 800°C indicating suppression of coke formation due to the presence of well-dispersed CeAlO3 which prevents carbon deposition on nickel active sites and provides the oxidative environment. The findings of this work will illustrate the potential application of Ni-based catalysts for the catalytic reduction of CO2 to CO with excellent activity and selectivity.

Synthesis, characterization and spectroscopic properties of some rare earth activated LiAlO2 phosphor

The current paper comprises the synthesis of LiAlO 2 phosphor doped with rare-earth elements Tb 3+ , Eu 3+ , and Dy 3+ by microwave-assisted solution combustion synthesis method (SCS) and the spectroscopic properties were examined. The phosphors samples were identified and characterized by XRD, FT-IR, thermo-gravimetric analysis TG-DTA and SEM. All the prepared phosphors show polycrystalline nature with a grain size of about 49 nm as confirmed from XRD and SEM. Photoluminescence excitation and emission spectrum of Tb 3+ , Eu 3+ , and Dy 3+ doped LiAlO 2 with different sintering temperature and concentration of dopants were investigated. The Dy 3+ shows the strongest blue emission peak at 484 nm corresponding to the transition 4 F 9/2 to 6 H 15/2 under UV excitation of 358 nm. The Eu 3+ doped LiAlO 2 phosphor shows emission peak 591 nm to 615 nm for UV excitation of 238 nm which arise due to 5 D 0 to 7 F 1 electric dipole transitions. The Tb 3+ doped phosphor shows a broad excitation peak centered at 238 nm whereas it exhibits an emission peak at 544 nm corresponding to the peak transition 5 D 4 - 7 F 6 under the UV excitation at 238 nm.

Thermoluminescence properties of MgO:Al3+,Li+ prepared by microwave-assisted solution combustion method

In this work, the thermoluminescence (TL) properties of MgO co-doped with Al3+ and Li+ cations, prepared by microwave-assisted solution combustion synthesis, using glycine as a fuel, are presented for the very first time. The X-ray diffractometer pattern confirmed MgO:Al3+,Li+ cubic phase formation and showed minor presence of a secondary phase associated with Al3+ cations. The energy band gap of the sample was approximated to 3.52 eV using the Kubelka-Munk relation. TL spectroscopy equipped with a beta source for sample irradiation was used to investigate electron trapping centres of MgO:Al3+,Li+. The dose-response measurements confirmed the general order kinetics. The depth of these electron trapping centres was approximated to be from 0.70 to 0.81 eV.

Synthesis of NiO nanoparticles loaded fly ash catalyst via microwave assisted solution combustion method and application in hydrogen peroxide decomposition

An efficient nickel oxide nanoparticles loaded fly ash catalyst (NiFAk) has been synthesized via microwave assisted solution combustion synthesis (MWSCS) method by using urea as a fuel and nickel nitrate as oxidizer. Fly ash was thermally and chemically activated prior to being used as support material for catalyst synthesis to intensify bonding and dispersion of NiO nanoparticles over fly ash surface. The surface characteristics of the chemically activated fly ash (CFAk) indicated that after chemical activation of fly ash, loading of NiO increased due to increase in surface hydroxyl groups (–OH) and the formation of a new calcium silicate hydrate phase. Characterization studies were done using some analytical techniques viz. XRF, BET surface area, X-ray diffraction, FTIR, SEM and SEM-EDX. The X-ray diffraction pattern confirmed that the prepared catalyst (NiFAk) is nanocrystalline with crystallite size 6.4 nm. Catalytic performance of NiFAk catalyst was checked on decomposition reactions of hydrogen peroxide. The reaction parameters were optimized by varying some parameters like as pH, calcination temperature, nature of catalyst etc. Results indicated that microwave irradiation increases the nucleation of nickel oxide over fly ash surface responsible for uniform loading of nanosized NiO particles over fly ash surface. MWSCS using urea as fuel for the synthesis of NiFAk catalyst has been found suitable, eco-friendly and efficient process.

Structural, photoluminescence and thermoluminescence study of novel Li+ co-activated lanthanum oxide activated with Dy3+ and Eu3+ obtained by microwave-assisted solution combustion synthesis

Stimulated luminescence of novel La2O3 nanophosphors doped with Dy3+ and Eu3+ and co-activated with Li+, prepared by microwave-assisted solution combustion synthesis, was investigated for the very first time. X-ray diffraction results indicated hexagonal La2O3 crystalline phase. Lanthanide and Li+ doping did not affect the La2O3 crystal structure. Scanning electron microscopy images showed nanoparticle morphologies such as plates, rods and irregular shapes. Photoluminescence spectra of La2O3:Dy3+, Li+ exhibited blue and green emission bands due to Dy3+ transitions. For La2O3:Eu3+, Li+, sharp emission lines, corresponding to the optical transitions of Eu3+ were observed. Thermoluminescence glow curve of La2O3:Dy3+, Li+ previously exposed to beta radiation exhibited a prominent glow peak located at ∼46 °C, possibly useful for after-glow or persistent luminescence applications, whereas La2O3:Eu3+, Li+ curve, displayed three intense peaks at ∼50, ∼110 and ∼150 °C. Thermoluminescent signal repeatability and decay curve asymptotic behaviour could place La2O3:Eu3+, Li+ as suitable for medium and high-dose radiation dosimetry applications.

Microwave assisted solution combustion synthesis of β-tricalcium phosphate nano-powders

A new approach for synthesis of β-tricalcium phosphate (β-TCP) was investigated by microwave-assisted combustion method. Three different fuels, glycine, urea and citric acid were used and their effects on the β-TCP powders formation were investigated. The morphology of powders, chemical and phase constituent were determined by SEM, FTIR and XRD, respectively. The results indicated that β-TCP powders with high purity could be obtained when citric acid is used as fuel; and in case of glycine and urea small amounts of hydroxyapatite (HA), calcium pyrophosphate and calcium hydrogen phosphate were detected by XRD. The morphology of β-TCP particles was found to be depended on fuel type. More uniform particle size with higher β-TCP purity was obtained by citric acid as fuel.

Microwave-assisted solution combustion synthesis of BiFeO3 powders

Microwave-assisted solution combustion method was used for preparation of bismuth ferrite (BiFeO3) powders at different fuel contents (φ = 0.5, 0.75, 1 and 2). Phase, structure, microstructure, magnetic, and optical properties of BiFeO3 powders were characterized by infrared spectroscopy, thermal analysis, X-ray diffractometry, nitrogen adsorption–desorption, electron microscopy, vibrating sample magnetometry, and diffuse reflectance spectroscopy techniques as a function of ignition method and fuel content. Practically pure BiFeO3 powders were formed at low fuel contents using microwave heating, while the impurity phases of conventionally combusted BiFeO3 powders were only disappeared following calcination at 600 °C. The strong absorption in the visible region of synthesized BiFeO3 powders was due to their narrow optical band gap energy (1.86–2.07 eV), as measured by diffuse reflectance spectrometer. The conventionally combusted BiFeO3 powders with high-specific surface area (37 m2/g) showed the highest visible photocatalytic activity (~60%).

Microwave-assisted solution combustion synthesis of Fe3O4 powders

Abstract Magnetite (Fe 3 O 4 ) powders were synthesized by solution combustion method at different fuel to oxidant ratios (ϕ = 0.5, 0.75, 1 and 1.5) using conventional and microwave ignition. The ignition method and fuel content affected the phase evolution, microstructure and magnetic properties of Fe 3 O 4 powders as characterized by X-ray diffractometry, infrared spectroscopy, N 2 adsorption–desorption, electron microscopy and vibrating sample magnetometry techniques. Single phase Fe 3 O 4 powders were only obtained using conventional ignition at ϕ value of 1, while the impurity phases such as α-Fe 2 O 3 and FeO together with Fe 3 O 4 phase were formed by microwave ignition. The bulky microstructure of conventionally combusted powders with specific surface area of 71.5 m 2 /g was transformed to disintegrated structure (76.5 m 2 /g) by microwave heating. The microwave combusted powders showed the highest saturation magnetization of 86.5 emu/g at ϕ value of 0.5 and the lower coercivity than that of conventionally combusted powders at all ϕ values, due to their larger particles.

Microwave-Assisted Solution Combustion Synthesis of Spinel-Type Mixed Oxides for Esterification Reaction

Environmentally benign production of biodiesel using heterogeneous catalysts is an important issue that requires the preparation of catalysts with high activity and reusability by a simple procedure. In this study, pure alumina and zinc oxide- and copper oxide-modified alumina were tested for the esterification of oleic acid to its methyl ester. The microwave-assisted solution combustion (MSC) method was used to prepare the catalyst samples that were characterized by X-ray diffraction (XRD), Fourier transform infra-red (FTIR), Brunauer–Emmett–Teller (BET) surface area measurement, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The spinel-type zinc aluminate was successfully synthesized, but CuO-modified alumina particles were clearly observed. Whereas in the alumina, much lower activity was observed than the doped alumina, zinc aluminate showed higher activity than copper oxide-alumina due to its smaller particle size, higher BET surface area, larger average pore size, and higher acidity. Finally, after the reaction conditions for the conversion of oleic acid were optimized for the case of spinel ZnAl2O4 as nanocatalyst, a yield of higher than 94% was obtained at 180°C, 9 methanol/oleic acid molar ratio, 3 wt% of catalyst for 6 h. Furthermore, the catalyst deactivation was not observed after four reaction cycles at the optimal reaction conditions, indicating the feasibility of the proposed method for the preparation of industrial catalysts.

Fluorescein-labeled fluoroapatite nanocrystals codoped with Yb(III) and Ho(III) for trimodal (downconversion, upconversion and magnetic resonance) imaging of cancer cells

The authors report on upconversion nanocrystals (NCs) based on a fluoroapatite (FAp) support that was engineered to enable multimodal imaging by fluorescence imaging (FI), magnetic resonance imaging (MRI), and upconversion luminescence imaging. A fluorescein based fluorophore (FITC) was incorporated into the FAp nanocrystals and then doped with Yb(III) and Ho(III) by microwave-assisted solution combustion synthesis. The hexagonal phase nanocrystals (FITC-FAp:Yb/Ho) exhibit spindle like morphology with an average diameter and length of 15 nm and 196 nm, respectively. The doping concentration of the Yb (5 %) and Ho (0.6 %) was determined by ICP-MS. The nanocrystals exhibit upconversion luminescence when irradiated with NIR light of wavelength 980 nm. The emission spectrum consists of two bands centered at 542 nm (green emission) and 654 nm (red emission) corresponding to two transitions of Ho(III). The pump power dependence of upconversion luminescence intensity confirmed the 2-photon process. The presence of FITC in the nanocrystal imparts green fluorescence (peaking at 521 nm) by a conventional downconversion process. The presence of Ho(III) endows the NCs with paramagnetism. The magnetization is 21.063 emu∙g−1 at room temperature. The NCs exhibit a longitudinal relaxivity (r1) of 0.12 s−1∙mM−1, and a transverse relaxivity (r2) of 29 s−1∙mM−1, which makes the system suitable for developing T2 MRI contrast agents. The nanocrystals are surface aminized using polyethyleneimine (PEI) and covalently conjugated to folic acid (FA) in order to target the folate receptors that are overexpressed in many cancer cells. The FA-conjugated nanocrystals have been tested for their applicability in fluorescence imaging of HeLa cells. Their biocompatibility, upconversion and downconversion luminescence, and magnetism render these NCs potentially powerful nanoprobes for trimodal imaging.

Simple microwave assisted solution combustion synthesis of cerium and nickel doped ZnO nanostructures: Effects on structural, morphological, optical, and magnetic properties

We report the structural, morphological, optical, and magnetic properties of pure and co doped ZnO nanostructures by inexpensive microwave combustion technique. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy EDS, diffuse reflectance spectroscopy (DRS), vibrating sample magnetometer (VSM) and photoluminescence (PL) spectra. X-ray diffraction (XRD) results show a single phase nature with hexagonal wurtzite structure, and reveal the incorporation of Ce and Ni ions into the lattice positions of ZnO lattice. Diffuse reflectance spectroscopy (DRS) showed a decrease in the band gap on increasing the dopant concentration. The photoluminescence (PL) of the samples showed the violet, blue and green peak for the samples. SEM images shows that they are spherical in shape and the size of the particles decrease on increasing the co dopant concentration. The magnetization measurements show the presence of ferromagnetic behavior for all the co-doped samples.

Formation of nanostructured fluorapatite via microwave assisted solution combustion synthesis

Fluorapatite (FA) has potential applications in dentistry and orthopedics, but its synthesis procedures are time consuming. The goal of the present study is to develop a quick microwave assisted solution combustion synthesis method (MASCS) for the production of FA particles. With this new processing, FA particles were successfully synthesized in minutes. Additionally, unique structures including nanotubes, hexagonal crystals, nanowhiskers, and plate agglomerates were prepared by controlling the solution composition and reaction time. In particular, the as-synthesized FA nanotubes presented a “Y” shape inner channel along the crystal axis. It is supposed that the channel formation is caused by the crystal growth and removal of water soluble salts during processing. The as-synthesized FA nanotubes showed good cytocompatibility, the cells cultured with a higher FA concentration demonstrated greater growth rate. With this new and easily applied MASCS processing application, FA nanoparticles have increased potential in dental and orthopedic applications.

Synthesis and Characterization of Thermochromic La0.75Ca0.25MnO3 Perovskite Manganites Nano-powders by Microwave-assisted Solution Combustion Synthesis

The microwave-assisted solution combustion synthesis was developed for application with initially synthesized thermochromic perovskite manganese oxide La0.75Ca0.25MnO3 nano-powders. Dry and very fine powders were obtained after one-step combustion reaction for less than 10 min in a modified domestic microwave oven. The thermal behavior, phase formation and purity of the precursor, and as-synthesized and calcined powders, were investigated by TGA/DTA, X-ray diffraction (XRD) and FT-IR techniques. The morphology of the powder obtained was characterized using a scanning electron microscope (SEM). The XRD pattern and FT-IR results showed that as-synthesized La0.75Ca0.25MnO3 powders were crystalline, and the monophasic perovskite phase occurred with an average crystallite size of 30.46 ± 5.54 nm for 6 h at a relatively low calcination temperature of 900°C. The small particle size obtained by SEM suggested a high specific surface area and high sinterability. This method was found to be simple, rapid and cheap, and an effective way to prepare nano-size perovskite powders.

Microwave-assisted solution combustion synthesis of high aspect ratio calcium phosphate nanoparticles

Abstract

Microwave assisted solution combustion synthesis of strontium phosphate (SrP) whiskers

A rapid microwave assisted solution combustion process is used to synthesize SrCaP and SrP whiskers. It is observed that SrP whiskers composed of Sr2P2O7 and Sr5(PO4)3Cl can be efficiently synthesized. However, co-existence of Ca2+ and Sr2+ ions in the reaction can inhibit one-dimensional crystal growth. The introduction of Cl− ions to the reacting system is the key to induce the crystal formation towards to one-dimensional structure. The as-synthesized SrP whiskers were characterized and evaluated for potential biomedical applications.