Zirconium precursor

Pillared zirconium clay modified by sulfate constitutes a new class of materials. Nevertheless, the classical procedure consisting of impregnating these solids with sulfate solutions presents some disadvantages such as low surface area and a poor sulfur thermal stability. In a previous work, we have developed a new in situ sulfation preparation method using zirconyl chloride as zirconium precursor. However, the use of this salt gives an intercalation solution with a very low pH which can affect the clay layers. Furthermore, the addition of sulfate ions to the ZrOz solution is limited by Hauser salt or polymeric phase precipitation. 

Zirconium acetate seems to be a very interesting zirconium precursor for the preparation of zirconium sulfate pillared clay because of its high and stable pH level and its low sensitivity to the precipitation when the sulfate was added. Nevertheless, the progress of the polymerization reaction is very rapid at high Zr concentrations, even at reduced intercalation temperature (15 °C). 

Yogo, T., S. Kodama, and H. Iwahara. 1993. Synthesis of polycrystalline alumina-zirconia fibre using chelated aluminum-zirconium precursor. Journal of Materials Science 28 105-110. ... 

Dose experiments were conducted for each complex. The titanium precursor required a dose of 7.9 J/cm and the zirconium precursor a 32 J/cm dose. The doses for the mixed systems were less than required for the pure precursors. The required dose for the 2 1 1 Pb Zr Ti and the 1 1 Pb Ti mixture was the same (2.6 J/cm ) as that for the titanium precursor alone and 60 times slower than the lead precursor alone. However, the required dose for patterning the 1 1 Pb Zr film was 1.3 J/cm, approximately 26 times lower a dose than when zirconium is patterned alone. This presumably is a result of radical chemistry but may also reflect solubility effects. 

Monitoring of both the photochemistry and the dose requirements indicated that the mixed systems such as PZT may react more efficiently than at least some of the individual components react in pure films. This may be due to the effect of the mixture on the structure of the films or due to a radical chain component to the reaction. If a radical chain component is present then radicals photogenerated by a precursor such as lead which reacts efficiently may serve to initiate the reaction of less photosensitive systems such as the zirconium precursor. This result is consistent with the higher dose requirement for the lead in the presence of the other components. These results indicate that a mixture of precursors may improve the efficiency of photodecomposition. Further enhancements may be available by using additives which are photoradical generators, however, these may also alter the purity of the products obtained. 

For this purpose, different preparation methods (precipitation, electrolysis, sol-gel process, etc.) and zirconium precursors (chloride, oxychloride, nitrate, and alkoxides) have been used. However, it is widely known that supercritical drying (SCD) of zirconia gels is one of the more promising processes allowing the enhancement of textural and structural properties (Chap. 21) of zirconium oxide phases. 

Many researchers noted that independent of the zirconium precursor and the preparation method (precipitation, sol-gel, etc.), obtained zirconia xerogeis, dried at moderate temperature, were X-ray amorphous and crystallized only after calcination, at least, at 300°C, while the high-temperature SCD led to samples exhibiting tetragonal nanocrystallites. 

Zirconia aerogels were prepared by different methods, in particular by the sol-gel process, using different zirconium precursors, alcoholic solvents, and synthesis conditions. The solvents were removed by means of one of two different methods SCD at high-temperature or low-temperature extraction with supercritical C02-... 

Kikuta K., Fukaya A., Takagi K. Preparation of photoreactive zirconium precursor stabilized by aromatic diethanolamines and its application for fine patterning. J. Ceram. Soc. Jpn. 1999b 107 ... 

Stromberg et al. [188] observed after the conversion treatment of hot dip galvanized zinc, a thin film of a zirconium oxyhydroxide with a homogeneous bulk composition during the conversion process. XPS sputter profiles showed that this oxide layer includes small amounts of zinc ( 4 at%) from the base metal and fluorine (<9 at%) from the zirconium precursor. Due to the gradient preparation of the Zr layer via a dip coater, a linear increase of the conversion layer was observed. SKP measurements showed three areas of different Volta potentials. A region of high cathodic Volta potentials with values aroimd -0.8 V with... 

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