Bao-rang Li

Characterization and humidity properties of MgAl2O4 powders synthesized in a mixed salt composed of KOH and KCl

In this paper, we have tried to prepare MgAl2O4 spinel by molten salt synthesis using hydroxide as solvent. By controlling the amount of KCl in KOH, pure flower-like MgAl2O4 nanostructures could be synthesized at 1150 °C. Powder X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy were used to investigate the structures and morphologies of the obtained products. The results showed that the 3D flower-like nanostructures consisted of numerous 2D nanoflakes with a thickness of about several tens of nanometers. Further investigations on the possible formation mechanism revealed that a self-sacrificing template process dominated the formation of MgAl2O4 and the growth of the flower-like products was attributed to the competition between the growth rates along the directions perpendicular and parallel to the Al2O3 particle surfaces. Finally, an impedance-type humidity sensor was fabricated based on the flower-like MgAl2O4 nanostructures and tested for its humidity performance showing that the as-prepared MgAl2O4 nanostructures are suitable for high-performance humidity sensors.