Zircon formation from amorphous spherical ZrSiO4particles obtained by hydrolysis of aerosols
✍ Scribed by P. Tartaj; J. Sanz; C. J. Serna; M. Ocaña
- Publisher
- Springer
- Year
- 1994
- Tongue
- English
- Weight
- 978 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0022-2461
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✦ Synopsis
A procedure for the preparation of SiO2"ZrO2 spherical particles, based on the hydrolysis of liquid aerosols is described. A mixture of tetraethylortho-silicate (TEOS) and zirconium n-propoxide with the proper stoichiometry (Zr/Si atomic ratio = 1) was used as a liquid precursor. The alkoxide mixture had to be partially hydrolysed before aerosol generation in order to obtain solids with a zircon composition. The as-prepared powders consisted of particles in the micrometre range with an amorphous character. Energy dispersive X-ray spectroscopy (EDX), infrared (i.r.) and nuclear magnetic resonanee (NMR) analyses indicated the existence of a good compositional homogeneity and a large number of Si-O-Zr bonds in the sample. Calcination of the powder up to 950~ gave rise to the segregation of silica and the crystallization of tetragonal zirconia, which transformed into the monoclinic phase after heating at 1 300 ~ Crystallization of zircon started on calcination at 1450 ~ it was accompanied by the formation of some cristobalite. The complete transformation of the sample into zircon took place after prolonged heating (20 h) at 1500~