Microwave-assisted Solution Combustion Synthesis Research Articles

Microwave-Assisted Solution Combustion Synthesis and Characterization of Thermoelectric Ca<sub>3</sub>Co<sub>2</sub>O<sub>6</sub> Powders

The microwave-assisted solution combustion synthesis was applied to the initial synthesizing of Ca3Co2O6powder using glycine as a fuel and nitrate as an oxidant. The as-synthesized powders were calcined at 700-1,000ºC for 4h. Product characterization was performed using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Scanning electron microscope (SEM). The fuel-to-oxidizer molar ratio was found to affect the combustion reaction and character of the powder obtained. The phase composition of powder after calcination at various temperatures has shown that the formation of Ca3Co2O6occurs directly. The calcined powder possesses a rhombohedral crystal structure with an X-ray diffraction pattern that could be matched with the Ca3Co2O6JCPDS: 89-0629. This method is a simple way of synthesizing fine Ca3Co2O6powder with a low calcination temperature.

A microwave-assisted solution combustion synthesis to produce europium-doped calcium phosphate nanowhiskers for bioimaging applications

Biocompatible nanoparticles possessing fluorescent properties offer attractive possibilities for multifunctional bioimaging and/or drug and gene delivery applications. Many of the limitations with current imaging systems center on the properties of the optical probes in relation to equipment technical capabilities. Here we introduce a novel high aspect ratio and highly crystalline europium-doped calcium phosphate nanowhisker produced using a simple microwave-assisted solution combustion synthesis method for use as a multifunctional bioimaging probe. X-ray diffraction confirmed the material phase as europium-doped hydroxyapatite. Fluorescence emission and excitation spectra and their corresponding peaks were identified using spectrofluorimetry and validated with fluorescence, confocal and multiphoton microscopy. The nanowhiskers were found to exhibit red and far red wavelength fluorescence under ultraviolet excitation with an optimal peak emission of 696nm achieved with a 350nm excitation. Relatively narrow emission bands were observed, which may permit their use in multicolor imaging applications. Confocal and multiphoton microscopy confirmed that the nanoparticles provide sufficient intensity to be utilized in imaging applications.

A Facile Microwave-Assisted Solution Combustion Synthesis of Highly Stable Magnesium Oxide for Multicomponent Mannich Reaction

A green and robust solid base MgO has been synthesized by a rapid microwave-assisted solution combustion synthesis method and evaluated for multicomponent Mannich reaction under solvent-free conditions at ambient temperature in the liquid phase. The synthesized catalyst was characterized by various techniques to ascertain its phase composition and thermal stability. Catalyst characterization studies revealed that magnesium oxide synthesized by microwaveassisted solution combustion synthesis method offers stable nanosized MgO crystallites. Good to excellent yields of β-amino carbonyl compounds were achieved with aromatic aldehydes bearing an electron withdrawing group.

A rapid microwave-assisted solution combustion synthesis of CuO promoted CeO2–MxOy (M = Zr, La, Pr and Sm) catalysts for CO oxidation

A series of copper oxide promoted CeO2–MxOy (MxOy=ZrO2, La2O3, Pr2O3 and Sm2O3) mixed oxides were synthesized by microwave-assisted solution combustion method using urea as the fuel and the respective metal nitrates as the precursors. The physico-chemical properties of the synthesized materials were analysed by BET surface area, X-ray diffraction (XRD), Raman spectroscopy, temperature programmed reduction/oxidation (TPR/TPO), X-ray photoelectron spectroscopy (XPS) and oxygen storage capacity (OSC) methods. XRD measurements confirmed the formation of solid solutions between ceria and the doped metal oxides in the presence of copper promoter. Raman measurements suggested defective structure of the mixed oxide solid solutions resulting in the formation of oxygen vacancies. The TPR/TPO studies revealed that the reduction behaviour of ceria depends on the type of metal dopant. XPS studies confirmed the presence of cerium in both Ce3+ and Ce4+ oxidation states in all mixed oxides. All the doped mixed oxides exhibited better CO oxidation activity compared to the undoped copper–ceria catalysts. Among various samples, ZrO2 doped copper–ceria showed a high activity (T1/2∼378K) followed by samarium, praseodymium and lanthanum oxide doped samples, respectively. Significance of the combustion synthesis method has been addressed that include simplicity, flexibility and the control of different favourable factors.

Microwave assisted solution combustion synthesis of alumina–zirconia, ZTA, nanocomposite powder

In the present study, the effect of microwave heating in producing alumina–20 wt% zirconia (ZTA) nanocomposite powder through metal nitrate solution combustion synthesis method, using urea as fuel, was studied. For comparison, ZTA nanocomposite powder is also synthesized using conventional heating method. To characterize the products and evaluate the effect of microwave heating system on them, X-ray diffractometry, TEM, SEM, surface area analysis (BET), and TG/DTA analysis were used. The results showed that, both ZTA powder synthesized in microwave and furnace were nanocrystalline, fine, and brittle, in which zirconia particles were homogeneously dispersed in the alumina matrix. The results also proved that, the powder produced in microwave was finer (<20 nm) with narrower size distribution and had better homogeneity of zirconia particles in alumina matrix, but lower specific surface area, in comparison with the sample which was synthesized in furnace.