Abstract
In the preparation of nanostructured materials, it is important to optimize synthesis parameters in order to obtain the desired material. This work investigates the role of complexing agents, oxalic acid and tartaric acid, in the production of MgO nanocrystals. Results from simultaneous thermogravimetric analysis (STA) show that the two different synthesis routes yield precursors with different thermal profiles. It is found that the thermal profiles of the precursors can reveal the effects of crystal growth during thermal annealing. X-ray diffraction confirms that the final products are pure, single phase and of cubic shape. It is also found that complexing agents can affect the rate of crystal growth. The structures of the oxalic acid and tartaric acid as well as the complexation sites play very important roles in the formation of the nanocrystals. The complexing agents influence the rate of growth which affects the final crystallite size of the materials. Surprisingly, it is also found that oxalic acid and tartaric acid act as surfactants inhibiting crystal growth even at a high temperature of 950°C and a long annealing time of 36 h. The crystallite formation routes are proposed to be via linear and branched polymer networks due to the different structures of the complexing agents.
Highlights
Magnesium oxide (MgO) is a versatile metal oxide having numerous applications in many fields
A sol-gel method is a promising technique for the formation of magnesium oxalate dihydrate followed by annealing at a suitable temperature to form MgO
The size and morphology of the MgO crystallites were determined using a field emission scanning electron microscope (FESEM; JEOL JSM-7600 F, Tokyo, Japan) and a transmission electron microscope (TEM; JEOL JEM-2100 F, Tokyo, Japan). In this sol-gel method, the metal salt and the complexing agents were dissolved in ethanol to form a mixture of cation (Mg2+) and anion (C2O42− or C4H4O62−)
Summary
Magnesium oxide (MgO) is a versatile metal oxide having numerous applications in many fields. MgO is obtained via thermal decomposition of various magnesium salts [7,8,9] The drawback with this method of obtaining MgO is the large crystallite size with low surface area-to-volume ratio that limits its applications for nanotechnology. Each precursor is annealed at a different temperature to produce highly crystalline and pure MgO Another precursor, magnesium oxalate dihydrate (MgC2O4 · 2H2O), has received considerable interest among researchers [24,25]. A sol-gel method is a promising technique for the formation of magnesium oxalate dihydrate followed by annealing at a suitable temperature to form MgO. The sol-gel reaction of magnesium oxalate dihydrate and annealing of the obtained precursors give various morphologies of MgO nanostructures [29,30,31,32]. The synthetic strategies of tailoring the size and shape of the nanostructures are key issues to be addressed in nanomaterials research
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