| Effect of Reaction Time on the Synthesis and Sintering of
Magnesium-Aluminium Spinel by Microwave Hydrothermal
Synthesis |
Runping Lia and Jianhua Liua, b, *
Pages : 265-269
DOI : 10.1080/0371750X.2021.2014637 |
| Abstract |
| In this study, microwave hydrothermal synthesis of magnesium-aluminium spinel from
pseudo-boehmite (AlOOH.nH2O) (n=0.62) and magnesium hydroxide (Mg(OH)2) for
different reaction times is researched. X-ray diffraction (XRD) and Fourier transform
infrared (FT-IR) are used to find out how the reaction time affects the synthesis of
magnesium aluminium spinel precursors. The superficial properties of magnesium
aluminium spinel precursors are investigated with scanning electron microscopy
(SEM). According to XRD analysis, magnesium hydroxide reacts with pseudo-boehmite
to form magnesium aluminium hydroxide hydrate. The median diameter of the samples
obtained at 200 min was 5.958 m. The agglomeration phenomenon was very serious
especially when the synthesis time is greater than 200 min. The sintered sample
obtained at 150oC for 200 min had more dense structure and smaller average grain
size. The average grain size of the sintered sample was 0.527 m. The best reaction
time for microwave isothermal synthesis and sintering of magnesium aluminium spinel
is 200 min.
[Keywords: Microwave heating, Magnesium aluminium spinel, Sintering, Densification,
Reaction time]
Introduction
Magnesium-aluminium spinel (MAS) has the
characteristics of high melting point (2135oC), low thermal
expansion coefficient, good thermal conductivity, good
thermal shock resistance and strong alkali corrosion
resistance. Therefore, it is widely used in steel, cement,
glass and ceramics and other fields.1–3 Magnesiumaluminium
spinel used for refractory materials is artificially
synthesized, and the synthesis temperature is relatively
high. Usually, the temperature of high-purity sintered
synthetic spinel is above 1700oC. During the synthesis
process, it is usually accompanied by volume expansion
of 5~8%, which limits the further densification of
magnesium aluminium spinel.4–8
In order to prepare highly dense MAS powders, this
study will use microwave hydrothermal synthesis to
prepare MAS powders. Microwave hydrothermal synthesis
is a relatively new method of material preparation. The
effective use of microwave offers the possibility to produce
high purity, ultra-fine and multi-component powders.
Compared to traditional methods of solid phase synthesis,
co-precipitati |
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