| Effect of Nanocrystalline Magnesium Aluminate Precursor
and Powder Granulometry on Spinellization and Densification
to Develop Magnesium Aluminate Spinel Aggregates |
Theerthagiri Viswanathan,a,# Soumen Pal,a,*,# Ariful Rahamana and Panchu Gopal Palb
Pages : 174-185
DOI : 10.1080/0371750X.2021.1915873 |
| Abstract |
| Nanocrystalline spinel forming precursor spinel hydrate (PSH), prepared by
co-precipitation technique with controlled concentration of mixed salt, pH, temperature
and time, was used as additive in calcined alumina-dead burnt magnesia (DBM)
admixture to develop spinel (MgAl2O4) aggregates. Powder granulometry, mixing and
dispersion of additive PSH were controlled during milling. Three batches of varying
particle size distribution with same proportion of additive were used for body making.
Firing was conducted in 1500o-1650oC temperature range. True specific gravity (TSG)
of alumina, DBM, spinel and individual fired pellets were used to estimate wt% spinel
formation based on the derived mass balance equation and subsequently verified by
X-ray diffraction (XRD) analysis. Fired properties, i.e. bulk density, apparent porosity,
closed porosity, %linear shrinkage and densification rate were measured. XRD was
conducted for phase analysis. SEM and HR-TEM were performed to study the grain/
pore morphology and elemental analysis was done to calculate the spinel
stoichiometry. PSH was found to have positive effect both in spinellization and
densification; the effect gradually decreased with finer particle size distribution and
increasing firing temperatures. The maximum fired density achieved for three batches
were 89.21, 92.84 and 96.2% th, respectively. Based on the requirements of specific
powder granulometry, addition of PSH and firing schedule can be used for bulk
production of spinel aggregates.
[Keywords: Magnesium aluminate spinel, Stoichiometric aggregate, Milling,
Densification, True specific gravity] |
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