The effect of solution chemistry on the preparation of MgAl{sub 2}O{sub 4} by hydrothermal-assisted sol-gel processing

Journal Article · Thu Mar 22 00:00:00 EDT 2007 · Materials Research Bulletin

DOI:https://doi.org/10.1016/j.materresbull.2006.06.011· OSTI ID:21000610

Amini, M M ^[1]; Mirzaee, M ^[1]; Sepanj, N ^[1]

---

1. Department of Chemistry, Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of)

Preparation of magnesium aluminate spinel powder by hydrothermal-assisted sol-gel processing from MgAl{sub 2}(OCH{sub 2}CH{sub 2}OR){sub 8}, R=CH{sub 3} (1), CH{sub 2}CH{sub 2}OCH{sub 3} (2), MgAl{sub 2}[OCH(CH{sub 3}){sub 2}]{sub 8} (3) and MgAl{sub 2}(O- {sup s}Bu){sub 8} (4) in toluene and parent alcohol has been investigated. Coordination status of aluminum atom in precursors was determined by {sup 27}Al NMR and correlation between coordination number of aluminum and development of spinel phase in hydrothermal-assisted sol-gel processing has been studied. The gels obtained from hydrothermal-assisted hydrolysis of magnesium-aluminum alkoxides that contain six-coordinated aluminum atoms in solution (1 and 2) after calcination at 700 deg. C resulted in the formation of pure spinel phase, whereas in similar hydrolysis and calcination processes of precursors that contain four-coordinated aluminum (3 and 4) spinel phase forms along with some Al{sub 2}O{sub 3} and MgO. Selected powders obtained from hydrothermal-assisted sol-gel processing were characterized by thermal analysis (TGA/DSC), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Results indicate that the coordination status of aluminum in the precursor is very crucial for the formation of pure phase spinel. The morphology of prepared spinels was studied by SEM and the results showed that the solvent in hydrothermal-assisted sol-gel processing has a marked effect on the morphology of the resulting MgAl{sub 2}O{sub 4}. In hydrothermal-assisted sol-gel processing of aluminum-magnesium alkoxides in hydrophobic solvent, spherical particles are formed, while in the parent alcohol, non-spherical powders are formed.

• OSTI ID: 21000610
• Journal Information: Materials Research Bulletin, Vol. 42, Issue 3; Other Information: DOI: 10.1016/j.materresbull.2006.06.011; PII: S0025-5408(06)00253-4; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALKOXIDES
ALUMINATES
ALUMINIUM
ALUMINIUM OXIDES
CALCINATION
CALORIMETRY
CERAMICS
COORDINATION NUMBER
DIMETHYL SULFIDE
GELS
HYDROLYSIS
MAGNESIUM OXIDES
MORPHOLOGY
NUCLEAR MAGNETIC RESONANCE
SCANNING ELECTRON MICROSCOPY
SOL-GEL PROCESS
SPINELS
THERMAL GRAVIMETRIC ANALYSIS
TOLUENE
X-RAY DIFFRACTION