Effect of fluorination on the surface texture of zirconia

• Published in: Surface technology 1981-01, Vol.12 (3), p.287-299
• Main Authors: A. Selim, Suzy, Hanafi, Said
• Format: Article
• Language: English
• ISSN: 0376-4583
• DOI: 10.1016/0376-4583(81)90102-3

Surface area measurements were performed on pure and fluorinated zirconia gels and their decomposition products in the temperature range ambient to 1000 °C by nitrogen adsorption at -196 °C and benzene and isopropanol adsorption at 35 °C. Impregnation by NH 4F does not change the amorphous character of the parent gel. A mixture of the tetragonal and monoclinic modifications is produced at 500 °C although the corresponding product of the pure gel is amorphous. At temperatures above 500 °C only the monoclinic zirconia exists. Fluorination increases the nitrogen areas markedly at temperatures of 500 °C and above but decreases the benzene and isopropanol areas at temperatures less than 1000 °C and less than 500 °C respectively. The surface is modified, and the sites that are active for adsorbing benzene molecules also appear to be responsible for adsorbing isopropanol. Pore structure analysis shows that the pure parent material is microporous whereas at higher temperatures mesoporosity predominates. Fluorination of the gel is found to create mesopores in the parent material and to increase mesoporosity in samples produced at higher temperatures as observed from the adsorption of the organic probe molecules. The nitrogen data show that in addition to the creation of mesopores at low temperatures stabilization of the surface texture by fluorination is established at 500 °C and above, giving rise to products with nearly the same specific surface areas, Brunauer-Emmett-Teller c constants and average pore radii.