Zirconia by the gel route

Combined SANS and SAXS study of the action of ultrasound on the structure of amorphous zirconia gels

“…2A), and this is in a good agreement with observations made by Ayral et al [69]. Table 2 evidence that ultrasonication leads to a dramatic increase in the surface fractal dimension of zirconia xerogels synthesized both in acidic and basic conditions:…”

“…In all the cases, r c lies within a range of 2.4-2.6 nm. Primary clusters of similar sizes were obtained by Ayral et al [69] for zirconia hydrogels synthesized from acidic media, and by Savii et al [26] for silica gels obtained in US-assisted synthesis. Thus we can conclude that sonication does not affect the size of monomer hydrous zirconia particles, but results in substantial changes in their aggregation patterns.…”

Zirconia: A Review of a Super Ceramic

“…These products are important from the structural viewpoint because they may involve both "condensation polymerization" (giving Zr -O-Zr systems) and "coordination polymerization". Ayral et al 95 recently suggested that the gelation could be regarded as resulting from a phenomenon of an aggregation of primary clusters produced just after the alkoxides and water react. This gelation is linked to both physical and chemical mechanisms, where the xerogel is probably an amorphous zirconium hydroxide.…”

“…This gelation is linked to both physical and chemical mechanisms, where the xerogel is probably an amorphous zirconium hydroxide. 95 Bradley et al,96 through ebulliometric studies, showed that zirconium alkoxides ZrO X (OR)4-2x' where R = Et, Pr n , Bu l and Bun, exhibit low number average molecular weights in solutions in their progenitive alcohols at the boiling points. It has also been suggested that hydrolysis of zirconium alkoxides Zr(OR)4' where R = Pr i , Bu i , Bd, leads to the formation of polymeric zirconyl alkoxides having low number-average degrees of polymerization, and there was no evidence of the formation of zirconyl compounds.…”

“…These in turn affect the sintering, and the phase transformation of Zr0 2 • For example, zirconium n-propoxide (Zr(OC 3 H 7 )4) is claimed to yield an oxide morphology which is more resistant to the t -+ m transformation, whereas zirconium ethoxide (Zr(OC 2 HJJ tends to produce the finest texture and highest compaction density. 95 It is possible to isolate the intermediate oxide alkoxides ZrO X (OR)4-2x under controlled conditions. These products are important from the structural viewpoint because they may involve both "condensation polymerization" (giving Zr -O-Zr systems) and "coordination polymerization".…”