Effect of thermal treatment on the textural properties and thermal stability of surface modified zirconia aerogel powders

In the present investigation, surface modified zirconia aerogel powders were heated at various temperatures to study the effect of thermal treatment on their textural properties and thermal stability. Zirconia aerogel powders were prepared using a sol-gel technique and ambient pressure drying method followed by thermal treatment at various temperatures ranging between 300-800°C under an air atmosphere for 1 h. The synthesised zirconia aerogel powders were characterised by N2 adsorption-desorption analysis, X-ray diffraction (XRD), field-emission scanning electron microscopy, Fourier-transform infra-red spectroscopy, and thermogravimetric differential scanning calorimetry. Thermal treatment causes phase transformation, crystallite growth and agglomeration in zirconia, strongly affecting the pore structure and surface area of zirconia aerogels. From N2 adsorption-desorption analysis, it was observed that the surface area of zirconia aerogel powder suddenly decreased until 500°C, was maintained to 600°C, and decreased again with increasing temperature up to 800°C. The results of XRD plots revealed the amorphous nature of zirconia up to 500°C, which then transformed to a tetragonal phase (at about 600°C), which has large surface area and fairly high thermal stability. The observed surface area of 153 m²/g for the 600°C-annealed zirconia aerogel powder with a tetragonal structure is high enough for catalysis applications.