Characterization of microporous zirconia gels
Sing, K. S. W.
Theocharis, Charis R.
SourceStudies in Surface Science and Catalysis
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MetadataΕμφάνιση πλήρους εγγραφής
Microporous zirconia gels were prepared from zirconyl chloride by the reaction in aqueous solutions with either ammonium carbonate or bircarbonate. Under conditions of low pH the ammonium bicarbonate precipitated gels tended to develop microporosity and an ill-defined mesoporosity. With the aid of FTIR spectroscopy and thermal analysis, it has been shown that carbonato ligands were present in most of the freshly prepared gels. All the gels were found to be X-ray amorphous when dried at room temperature and when heated for five hours up to 400°C. The exothermal transformation, which generally occurred in the temperature range 420°C− 450°C was associated with the ‘glow phenomenon’ and resulted in the develpment of crystallinity. The presence of residual water ligands and carbonato ligands served to protect the metastable material and delay the onset of the glow phenomenon. © 1994, Elsevier Science B.V.