Synthesis and rheological properties of mesoporous nanocrystalline CeO2 via sol–gel process

Cubic-phase CeO2 with high surface area was prepared using sol–gel process. The effect of sol–gel parameters, viz. HCl:alkoxide and water:alkoxide molar ratios, indicated that the gelation time increased with acid concentration and the lowest gelation time was found at 55 water:alkoxide molar ratio. The XRD patterns of cerium dioxide at different calcination temperature (300–800 °C) and times (1–7 h) showed increasing crystallinity as a function of temperature and time, while the scanning electron microscope (SEM) micrographs showed the agglomeration of crystallites to form large particle cerium dioxide at higher calcination temperatures. The Brunauer–Emmett–Teller (BET) specific surface area increased with decreasing the HCl:alkoxide and water:alkoxide molar ratios, calcination temperature and time. The highest surface area was obtained at 0.8:1:55 HCl:alkoxide:water molar ratio and 400 °C calcination for 1 h (180 m2/g). The viscoelastic properties of different HCl:alkoxide ratio solutions were studied using oscillatory shear. The fractal dimension determined from the frequency-scaling exponent of the modulus at the gel point indicated a dense critical gel structure at high HCl ratio and tight structure at low amount of acid. The gel strength increased as a function of acid molar ratio and the 0.8 molar ratio gave the highest gel strength.