Abstract: Mixed zirconium and yttrium oxides (ZrO.sub.2 (Y.sub.2 O.sub.3)) with a yttrium content (evaluated as metal) from about 15 to about 21% by weight, as powders in cubic crystal form, are prepared by:mixing an aqueous solution of zirconium and yttrium carboxylates with an organic solvent in the form of a nitrile or alcohol;from said mixture, precipitating solid particles of the precursors of mixed zirconium and yttrium oxides by operating at a pH between 5 and 7 and at ambient or close to ambient temperature; andcalcining said precipitated solid particles at high temperature to directly transform them from the amorphous state to the cubic crystal form.The mixed zirconium and yttrium oxides obtained in this manner are suitable for use in the ceramics sector.

Abstract: Mixed oxides of zirconium and yttrium [ZrO.sub.2 (Y.sub.2 O.sub.3)], with an yttrium content (as computed as elemental metal) comprised within the range of from about 15 to about 21% by weight, as spherical particles with size comprised within the range of from 0.1 to 2 .mu.m, with an average size of the particles lower than 1 .mu.m, in the cubic crystal form, are obtained by:preparing a mixture by starting from an aqueous solution of zirconium and yttrium carboxylates; an organic solvent selected from the group consisting of nitriles or alcohols; and a non-ionic surfactant;causing solid colloidal particles of the precursor of mixed zirconium/yttrium oxides to precipitate from said mixture, by operating at a pH value comprised within the range of from 5 to 7, at room temperature or at temperature close to room temperature; andcalcining said precipitate of solid particles at a high temperature to cause said solid particles to be directly converted from the amorphous state into the cubic crystal form.

Abstract: A precursor of zirconium dioxide in form of submicronic particles is obtained by:hydrolysing a zirconium alkoxide by bringing said zirconium alkoxide into contact with a microemulsion formed by an external oil phase, an internal aqueous phase, an emulsifier and a co-emulsifier;discontinuing the reaction of hydrolysis in order to control the growth of the particles; andrecovering the precursor of zirconium dioxide from the reaction mixture.Such a precursor can be submitted to treatments of calcination in order to prepare zirconium dioxide for ceramic uses.

Abstract: A precursor of zirconium dioxide in form of submicronic particles is obtained by:dispersing zirconium tetrachloride in an inert, liquid organic vehicle, with a surfactant being used in order to obtain a stable dispersion,adding water to said stable dispersion in order to form an emulsion, or adding water and a co-emulsifier in order to obtain a microemulsion, so as to hydrolyse zirconium tetrachloride and cause the zirconium dioxide precursor to precipitate from the system obtained, andrecovering said precipitated precursor.Such a precursor can be submitted to treatments of calcination in order to prepare zirconium dioxide for ceramic uses.

Abstract: Mixtures of C.sub.12 -C.sub.18 n-paraffins with paraffinsulfonic acids having the same number of carbon atoms, water and sulfuric acid, and obtained by sulfoxidation of said paraffins with sulfur dioxide and oxygen in the presence of water and ultraviolet radiation are stripped of their excess sulfur dioxide and decanted to separate most of the paraffins, and obtain a residual mixture.The residual mixture is fed with sulfuric acid until a two-phase system forms or at least until the mixture becomes turbid, and the turbid mixture or that floating on the heavy water-sulfuric acid phase is extracted with supercritical carbon dioxide, which removes with it the paraffins, which can be reused in the sulfoxidation process.