Abstract: An aqueous gellable composition capable of producing gels resistant to syneresis in the presence of divalent ions, contains:a water-soluble acrylamide polymer or copolymer,a crosslinking agent formed by a water-soluble aldehyde, or a water-soluble aldehyde and a water-soluble phenol,a water-soluble anti-syneresis agent selected from: organic carboxy acids, organic hydroxy acids and aminoacids, or among aminophosphonic acids and their alkali-metal or ammonium salts.When malonic acid is used, a delay in aqueous composition gelation is additionally obtained.

Abstract: Aqueous drilling muds effective at high temperature containing complexes, preformed or formed in situ, of tetravalent zirconium with one or more organic acids, or relative salts, of general formula (I) ##STR1## where R.sub.1 and R.sub.2, which can be the same or different, represent --H, --COOH, --CH.sub.3, --CH.sub.2 COOH or --CH(OH)COOH, or R.sub.1 and R.sub.2 jointly represent an oxo group (.dbd.O).

Abstract: An aqueous gellable composition having a delayed gelling time presettable within wide time and temperature ranges, contains a water-soluble organic polymer crosslinkable with chrome ion and a crosslinking/retardant system definable by the formula:Cr(L).sub.m.nL'wherein:Cr is a trivalent chrome ion;L is an organic ligand consisting of a monocarboxylate or dicarboxylate ion, optionally bearing one or more amino or hydroxy functional group(s), in form complexed with chrome ion;L' is an organic ligand consisting of a monocarboxy or dicarboxy acid, optionally bearing one or more amino or hydroxy functional group(s), in form not complexed with chrome ion;m has a value comprised within the range of from 1 to 3, depending on the nature of the ligand L;n has a value comprised within the range of from 0.5 to 100;with the proviso that in the crosslinking/retardant system, the ligand L is different from the ligand L'.

Abstract: A nickel cermet contains 35-70% by weight of a metal nickel phase and 65-30% by weight of a zirconia phase stabilized in the cubic form with yttria, with, on X-ray diffraction analysis, said phases appearing as distinct and homogeneously distributed at a level lower than 1 .mu.m.This nickel cermet is obtained by preparing an aqueous solution containing a heat-decomposable zirconyl, yttrium and nickel salt, and an organic hydroxyacid or aminoacid, or a poly(acrylic acid); removing water from the resulting solution, under conditions of absence, or substantial absence, of decomposition phenomena, in order to separate a porous solid; calcining the porous solid, and reducing with hydrogen the product from calcination.The nickel cermet obtained in this way is useful as an anodic material for a solid oxide fuel cell (SOFC).

Abstract: Gellable compositions containing:(a) water;(b) a water-soluble organic polymer bearing special chelating functional groups;(c) a multi-valent metal ion capable of causing the polymer to crosslink,are useful to recover oil from a oil field.Said compositions make it possible gels to be obtained which are endowed with improved physical properties and show a higher stability under the conditions prevailing in the oil field.

Abstract: The permeability of high-permeability zones in a oil reservoir can be reduced by using a gellable aqueous composition with delayed gelation. The composition comprises:a) water;b) a high-molecular weight natural or synthetic water-soluble polymer cross-linkable by means of Cr.sup.3+ ions;c) a water-soluble inorganic Cr.sup.

Abstract: An aqueous gellable composition having a delayed gelling time is disclosed, which contains a water-soluble polymer crosslinkable with Cr.sup.3+ and a crosslinking/retardant system containing a Cr.sup.3+ ion and a salicylic acid ligand, wherein said ligand can be in free form, or in the form of a complex with Cr.sup.3+, or partially in free form and partially in complexed form.Such a composition is useful for modifying the permeability in petroleum reservoirs, within a wide range of temperatures, of from about 60.degree. C. to 120.degree. C., or higher temperatures.

Abstract: The permeability of high-permeability zones in a oil reservoir can be reduced by using a gellable aqueous composition with delayed gelation.The composition comprises:a) water;b) a high-molecular weight natural or synthetic water-soluble polymer cross-linkable by means of Cr.sup.3+ ions;c) a water-soluble inorganic Cr.sup.

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: A gellable aqueous compositions able to reduce the permeability of high-permeability zones in an oil reservoir is a aqueous solution containing metered quantities of:a) a water-soluble organic polymer cross-linkable by the effect of a polyvalent metal ion cross-linking agent;b) a Cr(III) ion cross-linking agent; andc) a ligand for the cross-linking agent chosen from water-soluble organic alpha-hydroxy acids and alpha-amino acids.

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: New acrylamide copolymers formed by (meth)acrylamide benzene dicarboxylic monomer units in accordance with the following formula: ##STR1## wherein R is H or CH.sub.3 ; X is H or an alkaline metal or NH.sub.4 ; and wherein the COOX groups may be in ortho-, meta- or para- position in relation to each other, preferably being in ortho- position to each other; and of (meth)acrylamide monomer (II) units.

Abstract: A gellable aqueous composition particularly suitable for reducing the permeability of high-permeability zones in an oil reservoir is an aqueous solution comprising:a) a water-soluble organic polymer cross-linkable by the effect of a polyvalent metal ion cross-linking agent;b) a Cr(III) ion cross-linking agent;c) a buffer agent free or subtantially free of ligand characteristics towards the cross-linking agent, and chosen from organic bases and aromatic carboxylic or sulphonic acids;the solution pH being adjusted to a value within the range of about 2 to about 7.

Abstract: New homopolymers formed by malonic (meth)acrylamide monomer units according to the following formula: ##STR1## wherein R is H or CH.sub.3 ; X is H or an alkaline metal or NH.sub.4.sup.+ ; and copolymers formed by (meth)acrylamide monomer units (I) and monomer units (II).

Abstract: When used as occlusion agents or to cause fractures in a petroleum reservoir, polymer gels crosslinked with polyvalent metal ions can be removed by the use of special complexing agents.

Abstract: Room temperature vulcanizable organopolysiloxane compositions are provided based on the use of a silanol or alkoxy terminated organopolysiloxane and an effective amount of a diorganotin dicarboxylate and an amine accelerator.

Abstract: Room temperature vulcanizable organopolysiloxane compositions are provided based on the use of a silanol or alkoxy terminated organopolysiloxane and an effective amount of a diorganotinbis(chelate) catalyst.

Abstract: Stable, substantially acid-free, one package moisture curable alkoxy-terminated organopolysiloxane compositions are provided having a condensation catalyst and a stabilizer or scavenger for materials having chemically combined hydroxy radicals in the form of a molecular sieve.

Abstract: Stable, substantially acid-free, one-package moisture curable alkoxy terminated organopolysiloxane compositions are provided. These room temperature vulcanizable alkoxy terminated organopolysiloxane compositions use a condensation catalyst, a stabilizer, or scavenger for materials having chemically combined hydroxy radicals and diorganosulfoxide, such as dimethylsulfoxide which functions as a cure rate accelerator.

Abstract: Stable, substantially acid-free, one package moisture curable alkoxy-terminated organopolysiloxane compositions are provided having a condensation catalyst such as a tin compound, a silicon containing or silicon free organic scavenger for materials having chemically combined hydroxy radicals and certain organo nitrogen accelerators to effect a substantial enhancement in cure rate.