Evaluation of properties of non-stoichiometric alumina magnesia spinel using thiourea as fuel by varying soaking time

Abstract EN

The present article reports a simple and cost-effective process to prepare the crystalline MgAl2O4 spinel using a non-stoichiometric amount of magnesium nitrate, aluminum nitrate by solution combustion route.

Thiourea was used as a fuel and reducing agent while soaking was carried at 1000ºC with different soaking periods.

After slow drying of mixed solutions at 80ºC for 4-5 h, a gel was formed and got characterized by DTA/TGA (Differential Thermal Analysis and Thermal Gravimetric Analysis) to observe the effect of temperature variation and identify the range of temperature where crystalline nature of the powder was noted.

A powder sample was prepared from the gel after annealing at 1000ºC followed by soaking for 4 h, 5 h, and 6 h to compare the variation of particle size with respect to time.

The calcined powders were characterized by XRD (X-ray powder diffraction) to determine the phases and crystal planes present in the sample.

FT-IR (Fourier-transform infrared spectroscopy) was used to study the types of metal oxide or metal-metal bond present in the sample along with M-O coordination studies.

FESEM (Field emission scanning electron microscopy) was used to observe the morphological structure of the sample.

EDAX (Energy Dispersive X-Ray Analysis) was used to observe the percentage of each element present in the sample.

Bulk densities were estimated from 2.4156 g/cm3 to 2.8571 g/cm3 and the rapid increase in apparent porosity of samples 7.4289%, 10.3630% and 32.51% for 4 hours 5 hours and 6 hours respectively were also noted.

The average crystal size of spinel particles was noted to be about 48nm, 36 nm and 47 nm respectively.

It had been observed that the average crystal size of spinel particles was about 48 nm, 36 nm and 47 nm respectively.

Finally, the hardness of spinel was evaluated by Vicker Hardness test and evaluated to be10.52 GPa (1073 HV), 4.087 GPa (416.7HV) and 5.079 GPa (517.9HV).