A process for producing metastable nanocrystalline alpha-alumina (-Al.sub.2O.sub.3) having particle sizes smaller than 12 nm. Starting crystallites of -Al.sub.2O.sub.3 having a particle size larger than 12 nm, typically on the order of about 50 nm, are ball-milled at low temperatures to produce a nanocrystalline -Al.sub.2O.sub.3 powder having a particle size of less than 12 nm, i.e., below the theoretical room temperature thermodynamic size limit at which -Al.sub.2O.sub.3 changes phase to -Al.sub.2O.sub.3, wherein the powder remains in the -Al.sub.2O.sub.3 phase at all times.

A process for producing metastable nanocrystalline alpha-alumina (-Al.sub.2O.sub.3) having particle sizes smaller than 12 nm. Starting crystallites of -Al.sub.2O.sub.3 having a particle size larger than 12 nm, typically on the order of about 50 nm, are ball-milled at low temperatures to produce a nanocrystalline -Al.sub.2O.sub.3 powder having a particle size of less than 12 nm, i.e., below the theoretical room temperature thermodynamic size limit at which -Al.sub.2O.sub.3 changes phase to -Al.sub.2O.sub.3, wherein the powder remains in the -Al.sub.2O.sub.3 phase at all times.

An amorphous mesoporous alumina having a connectivity (Z) greater than 2.7 is described. The present invention also relates to the process for preparing the said alumina, comprising at least one precipitation step of at least one aluminum salt, at least one heating step of the suspension obtained, a thermal treatment step to form the alumina gel, a gentle drying step or spray drying step, a moulding step of the powder obtained, and a final thermal treatment step in order to obtain the alumina.

An amorphous mesoporous alumina having a connectivity (Z) greater than 2.7 is described. The present invention also relates to the process for preparing the said alumina, comprising at least one precipitation step of at least one aluminum salt, at least one heating step of the suspension obtained, a thermal treatment step to form the alumina gel, a gentle drying step or spray drying step, a moulding step of the powder obtained, and a final thermal treatment step in order to obtain the alumina.

Disclosed herein are methods of producing alumina trihydrate crystals from an alumina trihydrate recovery process stream wherein an aqueous emulsion comprising a crystal growth modifier, which is at least one of an acyclic anhydride or an alkyl or alkenyl succinic anhydride, is added to the alumina trihydrate recovery process stream, wherein the aqueous emulsion is substantially free of mineral oils. The method provides a decrease in percentage of alumina trihydrate crystals having a volume average diameter of less than about 45 micrometers compared to the percentage of alumina trihydrate crystals produced in the absence of the crystal growth modifier. The process does not require the addition of a defoamer/anti-foam agent in order to control foam generated in the process.

A process for producing metastable nanocrystalline alpha-alumina (-Al.sub.2O.sub.3) having particle sizes smaller than 12 nm. Starting crystallites of -Al.sub.2O.sub.3 having a particle size larger than 12 nm, typically on the order of about 50 nm, are ball-milled at low temperatures to produce a nanocrystalline -Al.sub.2O.sub.3 powder having a particle size of less than 12 nm, i.e., below the theoretical room temperature thermodynamic size limit at which -Al.sub.2O.sub.3 changes phase to -Al.sub.2O.sub.3, wherein the powder remains in the -Al.sub.2O.sub.3 phase at all times.

A process for producing metastable nanocrystalline alpha-alumina (-Al.sub.2O.sub.3) having particle sizes smaller than 12 nm. Starting crystallites of -Al.sub.2O.sub.3 having a particle size larger than 12 nm, typically on the order of about 50 nm, are ball-milled at low temperatures to produce a nanocrystalline -Al.sub.2O.sub.3 powder having a particle size of less than 12 nm, i.e., below the theoretical room temperature thermodynamic size limit at which -Al.sub.2O.sub.3 changes phase to -Al.sub.2O.sub.3, wherein the powder remains in the -Al.sub.2O.sub.3 phase at all times.

A side stream subsystem can be used to remove impurity species from the recirculating alkali metal chloride solution in certain electrolysis systems. Silicon and/or aluminum species can be removed via precipitation after introducing an alkali metal hydroxide and magnesium chloride in a side stream line in the subsystem. The invention can allow for a substantial reduction in raw material and capital costs.

A side stream subsystem can be used to remove impurity species from the recirculating alkali metal chloride solution in certain electrolysis systems. Silicon and/or aluminum species can be removed via precipitation after introducing an alkali metal hydroxide and magnesium chloride in a side stream line in the subsystem. The invention can allow for a substantial reduction in raw material and capital costs.

A positive electrode includes a lithium-based active material, a binder, a conductive filler, and discrete aluminum oxide nanomaterials. The aluminum oxide nanomaterials are mixed, as an additive, throughout the positive electrode with the lithium-based active material, the binder, and the conductive filler. The positive electrode with the discrete aluminum oxide nanomaterials may be incorporated into a lithium ion battery. The aluminum oxide nanomaterials may be formed by the following method. A solution is formed by mixing an aluminum oxide precursor and an acid. A carbon material is added to the solution, thereby forming an aqueous mixture having the carbon material therein. Hydrothermal synthesis is performed using the aqueous mixture, and precursor nanostructures are grown on the carbon material. The precursor nanostructures on the carbon material are annealed so that the carbon material is removed and aluminum oxide nanomaterials are formed.