The synthesis of ZrO2/SiO2 nanocomposites by the two-step CVD of a volatile halogen-free Zr alkoxide in a fluidized-bed reactor
W. Xia, Y. Wang, V. Hagen, A. Heel, G. Kasper, U. Patil, A. Devi, M. Muhler
Chemical Vapor Deposition, 2007, 13, 37-41
ZrO2/SiO2 nanocomposites with Zr loadings in the range 0.88 wt% to 12.2 wt% were prepared by a two-step metal-organic (MO)CVD process in a fluidized-bed reactor with the Zr alkoxide [Zr(OiPr)2(tbaoac)2] as the precursor. The high surface area of silica was hardly diminished by the deposition, and the deposited zirconia species were highly dispersed, as indicated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) investigations. The XPS data reveal a linear increase of the Zr surface concentration with increasing Zr loading. The high degree of dispersion is attributed to a strong interaction between the zirconia species and the support through the formation of Si-O-Zr bonds. Correspondingly, the intensity of the isolated silanol bands detected by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was found to decrease with increasing Zr loading.