Iranian Journal of Materials Science and Engineering

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Abstract:

composition of MgO and nano boehmite. The reactant and potassium chloride, as the reaction media, were fired at

800-1000 °C at different dwell times (0.5-5 h) in the ambient atmosphere. After washing and filtration, the spinel nano

powder was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Brunauer-Emmett-

Teller (BET) techniques. It was demonstrated that the formation temperature decreased to 850

particles revealed an average size of 30 nm with a narrow size distribution. The mechanism of MgAl

was found to be a template type where the morphology and size of product were similar to those of alumina formed

from boehmite decomposition. Prolonging the reaction time from 0.5 to 3 h, the reaction was further completed and

crystallinity was improved. However, the increase of temperature was more effective in this regard.

MgAl2O4 (MA) nano powder was synthesized via molten salt technique, by heating stochiometric°C. The nano spinel2O4 formation

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Well crystallized pure calcium zirconate (CaZrO3 ) nanopowder was successfully synthesized using the molten-salt method. CaCl2 , Na 2CO3, micro-ZrO 2and nano-ZrO 2 were used as starting materials. On heating, Na2CO3 reacted with CaCl 2to form NaCl and CaCO 3. Nano CaZrO 3 was formed by reacting equimolar amounts of in situformed CaCO 3 (or CaO) and ZrO 2 in molten Na 2CO3-NaCl eutectic mixture. CaZrO 3 particle size and synthesis temparture was tailored as a function of ZrO 2particle size. Due to the usage of nano-ZrO 2 , the molten salt synthesis (MSS) temperature was decreased and possible impurity phases in the final product were suppressed. The synthesis temperature was lowered to 800°C and soaking time of the optimal synthesis condition was reduced to 3h. After washing with hot-distilled water, the n-ZrO2sample heated at 800°C for 3h, was single phase CaZrO 3with 70-90 nm in particle size, while the m-ZrO 2sample heated at 1000°C for 3h, was single phase CaZrO 3 with 250-400 nm in particle size. Based on the TEM observation and thermodynamic analysis, the synthesized CaZrO 3 grains retained the morphology of the ZrO2 nanopowders, which indicated that a template formation mechanism play a dominant role in synthesis process