Microwave-assisted combustion synthesis of nanocrystalline Mg Al2O4 spinel powder (original) (raw)
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Effect of Urea Excess on the Properties of the MgAl2O4 Obtained by Microwave-Assisted Combustion
Materials Research, 2017
In this paper, magnesium aluminate spinels were prepared by microwave-assisted combustion, using urea as fuel. In order to evaluate the effect of the urea excess used in the synthesis, its mass was added in a range of 1.0 to 2.5 times the stoichiometric amount required. The materials produced were characterized by TGA, FTIR, XRF, XRD, BET, SEM and TEM. The results demonstrated that magnesium aluminate spinel was formed in all solids, but the crystallinity degree and the specific surface area increased according to the amount of urea that was used in the synthesis. The use of excess fuel in the preparation was therefore advantageous, since it eliminated the need of the calcination step, at high temperatures, in order to stabilize the spinel phase and improve the crystallinity of the solid. The heat generated in the combustion process was sufficient to develop the formation of a nanocrystalline structure and produce high purity materials, with a save of 99.4% in energy.
Journal of Alloys and Compounds, 2008
Nanocrystalline magnesium aluminate spinel (MgAl 2 O 4 ) was synthesized using metal nitrates, citric acid and ammonium solutions. The precursor and the calcined powders at different temperatures were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The combustion mechanism was also studied by a quadrupole mass spectrometer (QMS) which coupled to STA. The generated heat through the combustion of the mixture of ammonium nitrate and citrate based complexes decreased the synthesis temperature of MgAl 2 O 4 spinel. The synthesized MgAl 2 O 4 spinel at 900 • C has faced shape with crystallite size in the range of 18-24 nm.
Materials Letters, 2002
A chemical route, using industrial raw materials, was developed for the synthesis of MgAl 2 O 4 spinel precursor. The asobtained powder was then calcined in air, up to 1200 jC for a period of 1 h. It was found that spinel single phase is formed at several hundred degrees lower than temperatures reported for the conventional powder preparation methods. Moreover, at 500 jC the degree of crystallinity is higher than that reported by other chemical processes at this temperature. The calcined powder reaches 83% of relative density at 1200 jC, indicating reactivity and good sintering behaviour. Scanning electron microscopy images revealed that the product consisted of fine spherical particles of magnesium aluminate spinel.
Mixture of fuels approach for solution combustion synthesis of nanoscale MgAl2O4 powders
Advanced Powder Technology, 2011
Nanoscale MgAl 2 O 4 powders were synthesized via a microwave-assisted solution combustion process using various mixtures of urea, glycine and starch as fuel. The effects of starch addition on characteristics (e.g. specific surface area and crystallite size) of the as-resulted powders were also investigated. The experimental results revealed that the specific surface area of the powders was significantly increased as the starch content rose from 0 to 35.6 wt.%, followed by a slight decrease when it was further raised to 54.7 wt.%. The scanning electron microscope micrographs disclosed that starch addition also affected the morphology of porous nanoparticles' agglomerates and was remarkably beneficial to dissipate the asproduced nanoparticles. Higher degree of dissipation and larger specific surface area of the powders resulted from starch addition were mainly attributed to a larger amount of gases evolved during combustion and/or lower combustion temperature.
— This paper is a study of Nano sized MgAl 2 O 4 (Magnesium Alumminate) spinel powders which were synthesized by muffle furnace assisted Solution Combustion Synthesis using various mixtures of urea, glycine as fuel. It was seen that Mg(NO 3) 2 .6H 2 O and Al(NO 3) 3 .9H 2 O show different behavior with respect to urea and glycine. Also the variation of fuel to oxidizer (F/O) ratio was studied. The study was carried out for leaner to richer fuel ratios. In the case of MgAl 2 O 4 combustion synthesis results were achieved when fuel mixture (urea and glycine) were used. The use of fuel mixtures allowed the formation of pure, nano-crystalline MgAl 2 O 4 directly from the combustion reaction. The effect of fuel mixture ratios was investigated by variation of the ratios in which the fuel was taken. The later product was characterized by XRay-diffraction analysis .The nanoscaled images where taken by SEM (Scanning Electron Microscope) of the powder being produced.
Synthesis of nanocrystalline MgO/MgAl2O4 spinel powders from industrial wastes
Journal of Alloys and Compounds, 2017
This article reports a simple and cost-effective method to prepare ultrafine nanocrystalline MgO/ MgAl 2 O 4 spinel (M-MA) powders from industrial wastes arising from aluminium and magnesium scraps. M-MA precursor powders were calcined at different temperatures (650, 750, 850, 950, 1300e1500 C). The calcined powders were characterized by XRD, FT-IR, DTA, FESEM, and HR-TEM. In particular, ultrafine MgO/MgAl 2 O 3 powder was formed at a temperature of 650 C with crystallite size of 4.8 nm and 7 nm, respectively, as determined by XRD. Optical properties of the M-MA spinel powders revealed that the optical reflectance is highly dependent on the calcination temperature. A simple and cost-effective method to obtain ultrafine MgO/MgAl 2 O 4 nanocrystalline powders with expected unique properties was established. These synthesized spinel powders is a highly promised feedstock for refractory, ceramic and environmental applications.
MgAl2O4 spinel synthesis by combustion and detonation reactions: A thermochemical evaluation
Journal of The European Ceramic Society, 2012
The production of MgAl 2 O 4 spinel is evaluated using a thermochemical program, THOR, which calculates the equilibrium products resulting from the adiabatic combustion (isobaric and isochoric) or detonation of energetic materials. A classic metalized emulsion was used (ammonium nitrate, fuel oil, aluminium, water and glass microballoons), to which MgO was added. The Al/MgO proportion and the reaction regime were varied, the maximum spinel yield being achieved for the detonation of a fuel-rich emulsion with 5Al:3MgO (mol). In parallel, MgAl 2 O 4 was experimentally synthesized by solution combustion of Al and Mg nitrates with various urea contents. The same reactions were simulated with THOR and the results obtained for products type and amounts were found to be in good agreement. Additionally, THOR simulations provided clear explanations for the experimental observations, which can be of invaluable help in the selection of fuel type and content in solution combustion synthesis of any given mixed oxide.
Sintering behavior of magnesium aluminate spinel MgAl2 O4 synthesized by different methods
International Journal of Applied Ceramic Technology, 2019
This paper is focusing basically on the ceramic technology, of which several methods for the synthesis of MgAl 2 O 4 have been investigated. The synthesis conditions regarding the powders cleanliness, microstructure and sintering parameters of MgAl 2 O 4 were studied. MgAl 2 O 4 powder was synthesized via conventional solid-state route using different milling process: vertical attrition milling, WAB as a high-energy horizontal attrition milling and Pulverisette as a planetary ball miller, and via solution combustion route using Urea, Glycine and a mixture of Urea/Glycine. Urea and Glycine was used as fuel. The white powders was obtained for all solid-state routes and for Urea-combustion technique. The black and gray powders were obtained in the case of combustion technique, respectively, by using a fuel of Glycine and Glycine/Urea mixture. The obtained powders and pellets were characterized by XRD, SEM, and Dilatometry. The results show that, among all the solid-state route processes, wet attrition milling gives the better and clean spinel phase. The WAB milling and Pulverisette miller introduce a contamination by some yttria-stabilized zirconia balls in the corresponding powder. Further, the flash combustion technique permit to have nanoparticles with a dense spinel phase of MgAl 2 O 4 and with lower sintering temperature in less time and with no calcination step.
Rapidly synthesis of nanocrystalline MgIn2O4 spinel using combustion and solid state chemistry
Solid State Sciences, 2011
Nanometric/submicronic powders of magnesium indate spinel MgIn 2 O 4 were prepared with a two-steps process. First, nano-oxides of In 2 O 3 and MgO were obtained by combustion of aqueous solutions of metal nitrates (as an oxidizer) and different fuels (glycine/urea/citric acid). Then, the as-prepared combustion ashes were converted into pure spinels after calcinations at elevated temperature. The as-prepared powders spinels have nanometric or submicronic grain size. This process allows preparing the MgIn 2 O 4 spinel compound in 1 day whilst 10 days were necessary when the classical solid state chemistry is used. In this paper, we compare these two ways and study the effect of different reaction parameters, such as the nature of fuels or the fuel/oxidiser ratio. Crystallites sizes of the synthesized compounds were investigated by powder X-ray diffraction and Scanning Electron Microscopy. (S. Surblé). 1 Tel.: þ33 1 69 08 58 57. 2 Tel. þ33 1 69 08 20 92. 3 Tel.: þ33 1 69 08 29 20. 4 Tel.: þ33 5 62 25 78 48; fax: þ33 5 62 25 79 99. 5 Fax: þ33 1 69 08 71 13.