Stationary coprecipitation

The demand for mixed oxide chromatographic-quality stationary phase materials is small and only a few methods that detail their preparation are available in the hterature. There are, however, numerous examples of the preparation of zircon powders and Ref. [4] is an example of such a process. In general, these types of powders are unsuitable for chromatographic stationary phases because their particle sizes are in the submicron range with very broad distributions. The synthesis of mixed oxide supports for chromatographic apphcations can essentially be divided into two types coprecipitation methods and coating methods. 

In comparison, the stationary phases prepared using the coprecipitation process of Zhang, Feng, and Da with... 

In the specific case of zirconia-silica composites, the stationary phase could be prepared through relatively simple processes using either coprecipitation or coating methods. The addition of silica to the zirconia matrix increases the phase transition temperature from the amorphous phase to the tetragonal phase, which in turn stabilizes the tetragonal phase. The pore structure can be controlled through processes similar to those employed in the preparation of zirconia. However, the type of pore structure obtained appears to be dependent on the method of preparation. Calcination in the presence of salts improves the pore shapes. Zirconia-silica phases can also be surface-modified and Cg and ion-exchange media have been prepared. Composite zirconia-silica stationary... 

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