المصدر
Journal of Engineering Research, v. 18, no. 1, p. 44-51.
الملخص الإنجليزي
The present article reports a simple and cost-effective process to prepare the crystalline MgAl₂O₄ spinel using a non-stoichiometric amount of magnesium nitrate and aluminum nitrate via the solution combustion route. Thiourea was used as a fuel and reducing agent, while soaking was carried at 1000ºC for different soaking periods. After slow drying of mixed solutions at 80ºC for 4-5 hours, a gel was formed and characterized by DTA/TGA to observe the effect of temperature variation and identify the temperature range where crystallinity appeared. Powder samples were prepared from the gel after annealing at 1000ºC, followed by soaking for 4, 5, and 6 hours to compare the variation of particle size with respect to time. The calcined powders were characterized by XRD to determine the phases and crystal planes, FT-IR for studying the types of metal oxide bonds, FESEM for morphological analysis, and EDAX to observe the percentage of each element present. Bulk densities ranged from 2.4156 to 2.8571 g/cm³, and a rapid increase in apparent porosity was noted from 7.4289% to 32.51% as the soaking time increased from 4 to 6 hours. The average crystal size of spinel particles was observed to be 48 nm, 36 nm, and 47 nm, respectively. Finally, the hardness of spinel was evaluated using the Vickers Hardness test, yielding values of 10.52 GPa (1073 HV), 4.087 GPa (416.7 HV), and 5.079 GPa (517.9 HV).
