Su Z.,Rare Earth Metal Research Institute of Hunan |
Bao X.,Rare Earth Metal Research Institute of Hunan
Xiyou Jinshu/Chinese Journal of Rare Metals | Year: 2015
With Sc2O3, Zr(NO3)4·3H2O and NH3·H2O as starting materials, the precursor of scandia-doped zirconia ceramic powder was prepared by co-precipitation method using a little amount of PEG400 as surfactant, combined with repeatedly washing with de-ionized water and absolute ethanol. The thermal dehydration process and non-isothermal kinetics of the precursor of scandia-doped zirconia (ScSZ) ceramic powder were investigated by differential scanning calorimetry (DSC) and thermo-gravimetric analysis(TG) techniques in air atmosphere. As observed by DSC/TG, the endothermic peak around 390 K was attributed to the desorption of ethanol and water physicsorbed on the surface of the powder, the exothermic peak around 560 K on the DSC curve was caused by the oxidative removal of organic groups coordinated on the surface of the powder, the exothermal peak around 650 K could be attributed to the dehydration of hydroxide, and the endothermic peak around 690 K was connected with the crystal form transformation of the precursor. The activation energies (E) of the dehydration reaction stage were calculated by Kissinger and Doyle-Ozawa methods as 144.053 and 110.008 kJ·mol-1, respectively. The reaction order (n) and pre-exponential factor (A) were also determined by Kissinger method as 1.2 and 2.74×10-11, respectively. The kinetics equation of the dehydration process was deduced as dα/dT=2.74×1011e-127030.456/RT(1-α)1.2. Based on the results of dynamic study, the scandia-doped zirconia ceramic powder was prepared in optimized sintering condition. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results showed that the as-prepared materials were small microspheres and XRD peaks were sharp and corresponded well to the cubic structure. ©, 2015, Editorial Office of Chinese Journal of Rare Metals. All right reserved.