Chemical synthesis of nanocrystalline magnesium aluminate spinel via nitrate–citrate combustion route (original) (raw)
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— 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.
Microwave-assisted combustion synthesis of nanocrystalline Mg Al2O4 spinel powder
A stoichiometric MgAl 2 O 4 spinel powder was synthesized by a microwave-assisted combustion synthesis (MWCS) route. For the purpose of comparison, another stoichiometric MgAl 2 O 4 spinel powder was also prepared following the conventional combustion synthesis (CCS) method. The batch size had a strong influence on the specific surface area of the material, which in turn is highly dependent on the preparation method adopted. The surface areas of these synthesized powders were found to decrease from 36.78 to 0.1 m 2 /g for MWCS and 126 to 8.06 m 2 /g for CCS samples, respectively, when the batch size was increased from 2 to 100 g. This could be attributed to sintering of the samples due to high adiabatic temperature generated as a result of increased heat accumulation with bigger batch quantities. Between the two powders synthesized by the two different routes, the powders obtained by MWCS and CCS routes were found to contain grains/crystals in range of 20-50 and 100-250 nm size, respectively. The thermogravimetry/differential thermal analysis (TG-DTA) and X-ray diffraction (XRD) studies reveal that microwave-assisted combustion synthesis route yields materials with higher degree of compositional stability and phase purity as compared to the conventional combustion synthesis method.
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.
A review on magnesium aluminate (MgAl 2 O 4 ) spinel: synthesis, processing and applications
Magnesium aluminate (MgAl 2 O 4) spinel (MAS) is a synthetic material with cubic crystal structure and excellent chemical, thermal, dielectric, mechanical and optical properties. These properties made MAS an indispensable material for optically transparent windows, domes and armours, and for certain refractory applications. High processing cost of dense MAS ceramics is in the main responsible for its limited usage in certain important applications despite its excellent performance in them. The volume expansion (y8%) associated with MAS phase formation from alumina and magnesia does not allow obtaining dense MAS bodies in a single-stage reaction sintering process. Therefore, dense MAS bodies are made by following a double stage firing process, which is expensive. The existing literature suggests that the processing cost of dense MAS ceramics could be reduced to a great extent by decisive selection of starting raw materials, powder processing and densification conditions, and by understanding the underlying mechanisms of MAS formation and densification. Since there is no review article covering the complete comprehensive information of MAS, an attempt is made to write this review article with a main perspective of synthesis, processing and important applications of MAS and its utility for certain future emerging novel and innovative applications.
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.
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.
Characterization of Mg 1− x Ni x Al 2O 4 solid solutions prepared by combustion synthesis
Journal of The European Ceramic Society, 2011
Mg 1−x Ni x Al 2 O 4 (x = 0, 0.25, 0.5, 0.75 and 1) solid solutions have been prepared by combustion synthesis. After annealing the combustion synthesized powders at 1000 • C for 3 h single-phase Mg 1−x Ni x Al 2 O 4 was obtained over the entire range of compositions. The lattice parameter of Mg 1−x Ni x Al 2 O 4 gradually increased from 8.049Å (NiAl 2 O 4 ) to 8.085Å (MgAl 2 O 4 ), which certified the formation of the spinel solid solutions. All samples prepared by combustion synthesis had blue color shades, denoting the inclusion of Ni 2+ in the spinel structure in octahedral and tetrahedral configuration. The crystallite size of Mg 1−x Ni x Al 2 O 4 was in the range of 35-39 nm and the specific surface area varied between 5.8 and 7.0 m 2 /g.
Molten Salt Synthesis of Magnesium Aluminate (MgAl2O4) Spinel Powder
Journal of The American Ceramic Society, 2006
MgAl2O4 (MA) spinel powder was synthesized by heating an equimolar composition of MgO and Al2O3 in LiCl, KCl, or NaCl. The synthesis temperature can be decreased from >1300°C (required by the conventional solid–solid reaction process) to ∼1100°C in LiCl, or to ∼1150°C in KCl or NaCl. The molten salt synthesized MA powder was pseudomorphic and retained, to a large extent, the size and morphology of the original Al2O3 raw material, indicating that a “template formation mechanism” plays an important role in the synthesis process.
Synthesis of magnesium–aluminium spinel from autoignition of citrate–nitrate gel
Materials Letters, 2004
Magnesium -aluminium spinel has been synthesized by citrate -nitrate route using hydrated nitrates of Mg and Al as the precursors with a citrate -nitrate ratio of 1:1. Self-ignition of the gel-like mass yielded a black mass, which crystallized to Mag -Al spinel on calcination at 650 jC for 9 h. The crystallized mass was a mixture of ordered and disordered phases of Mag -Al spinel. Phase pure-ordered spinel could be obtained for powders calcined at 1100 jC and above. The green compacts of the spinel powders could be sintered to near theoretical density at 1150 jC for 30 min. The activation energy for densification was calculated (16.4 kcal/mol) assuming Arrhenius type behaviour. The densification mechanism could be assigned to the ordering of the disordered spinel involving vacancy diffusion through the surface. D