A method of making a titanium dioxide nanowire array includes contacting a substrate with a solvent comprising a titanium (III) precursor, an acid, and an oxidant while microwave heating the solvent, thereby forming a hydrogen titanate H2Ti2O5.H2O nanowire array. The hydrogen titanate nanowire array is annealed to form a titanium dioxide nanowire array. The substrate is seeded with titanium dioxide before starting the hydrothermal synthesis of the hydrogen titanate nanowire array. The titanium dioxide nanowire array is loaded with a platinum group metal to form an exhaust gas catalyst. The titanium dioxide nanowire array can be used to catalyze oxidation of combustion exhaust.

The present invention relates to the processing of natural titanium-containing feedstock, mainly ilmenite concentrate, including ilmenite ores with a low TiO.sub.2 content, into products with high added value without generating any liquid or solid waste. The method according to the invention comprises the following stages: digesting ilmenite concentrate, processing the solid residue following ilmenite concentrate digestion, hydrolysis of titanium oxychloride, washing titanium oxides/hydroxides precipitate from impurities, calcination of titanium oxides/hydroxides precipitate, precipitation of iron hydroxides to obtain black, red and yellow iron oxide pigments, processing the mother liquor containing calcium chloride, regeneration of hydrogen chloride from ammonium chloride solution, obtaining ammonium sulfate and ammonium sulfate crystallization, obtaining crystalline ammonium chloride. The resulting products are pigments, pigment fillers, mineral fertilizers, construction materials, raw materials for the production of metals, and other products; they are used in various fields of application such as paint and coatings industry, pulp and paper industry, in the production of plastics, in metallurgy, in agricultural, construction industries and others.

The present invention manufactures titanium oxide particles that have a small degree of aggregation (size of aggregate particle diameter relative to primary particle diameter) and are not readily sintered by heating. The present invention has: a step in which an alkali and a solution including a carboxylic acid and a titanium (oxy)chloride are mixed, and the titanium (oxy)chloride is hydrolyzed by neutralization; and a step in which, after the hydrolysis by neutralization, the solution is heated to a temperature of 80 C. or more and 110 C. or less, and the titanium (oxy)chloride remaining in the solution is hydrolyzed by heating. It is thus possible to obtain titanium oxide particles that have a small degree of aggregation and a range of 1-35 for the ratio (D90/BET diameter) between the 90% cumulative mass particle size distribution diameter (D90) (nm) as measured by a dynamic light-scattering particle diameter distribution measurement device and the BET diameter (nm) as calculated from the specific surface area of the titanium oxide particles.

A method of making a titanium dioxide nanowire array includes contacting a substrate with a solvent comprising a titanium (III) precursor, an acid, and an oxidant while microwave heating the solvent, thereby forming a hydrogen titanate H2Ti2O5.H2O nanowire array. The hydrogen titanate nanowire array is annealed to form a titanium dioxide nanowire array. The substrate is seeded with titanium dioxide before starting the hydrothermal synthesis of the hydrogen titanate nanowire array. The titanium dioxide nanowire array is loaded with a platinum group metal to form an exhaust gas catalyst. The titanium dioxide nanowire array can be used to catalyze oxidation of combustion exhaust.

The present invention produces titanium oxide particles which have a sufficiently small average aggregate particle diameter (D50), while containing much less amorphous components. According to the present invention, a solution containing titanium (oxy)chloride and a carboxylic acid and/or a salt thereof is heated at a temperature that is not less than 95? C. but not more than the boiling point of the solution (first hydrolysis step); and a solution, which is obtained by mixing a solution that contains a product of the first hydrolysis step with titanium (oxy)chloride and a carboxylic acid and/or a salt thereof, is heated at a temperature that is not less than 95? C. but not more than the boiling point of the solution (second hydrolysis step). In addition, the present invention provides titanium oxide particles which have an average aggregate particle diameter (D50) of 15 nm to 200 nm, while having a content of amorphous components of 7% by mass or less.

The present invention manufactures titanium oxide particles that have a small degree of aggregation (size of aggregate particle diameter relative to primary particle diameter) and are not readily sintered by heating. The present invention has: a step in which an alkali and a solution including a carboxylic acid and a titanium (oxy)chloride are mixed, and the titanium (oxy)chloride is hydrolyzed by neutralization; and a step in which, after the hydrolysis by neutralization, the solution is heated to a temperature of 80 C. or more and 110 C. or less, and the titanium (oxy)chloride remaining in the solution is hydrolyzed by heating. It is thus possible to obtain titanium oxide particles that have a small degree of aggregation and a range of 1-35 for the ratio (D90/BET diameter) between the 90% cumulative mass particle size distribution diameter (D90) (nm) as measured by a dynamic light-scattering particle diameter distribution measurement device and the BET diameter (nm) as calculated from the specific surface area of the titanium oxide particles.

Ordered acicular aggregates of elongated TiO.sub.2 crystallites which resemble nano-sized flower bouquets and/or triangular funnels, and process for their preparation by thermally hydrolyzing a soluble TiO.sub.2 precursor compound in aqueous solution in the presence of a morphology controlling agent selected from carboxylic acids and amino acids.