Provided is a method for producing nickel powder, wherein fine nickel powder serving as seed crystals needed for production of nickel powder is produced from a solution containing a nickel ammine sulfate complex according to the amount needed for the production of the nickel powder. The method for producing nickel powder is characterized in that: the solution containing the nickel ammine sulfate complex, an insoluble solid, and a dispersant are continuously fed into a reaction vessel, followed by stirring to prepare a solution containing a nickel complex ion; hydrogen gas is blown into the prepared solution to reduce the nickel complex ion in the solution containing the nickel complex ion, thereby forming a precipitate of nickel particles on the surface of the insoluble solid; and thereafter the post-reduction solution is extracted from the reaction vessel.

To provide a metal-based structure or nanoparticles whose homogeneity is not deteriorated and whose sticking formation is easy, and a production method thereof with a high safety. A metal-based structure comprises a hydrogen compound, cluster, or an aggregate thereof, represented by the general formula: M.sub.mH. The M is a metal-based atom. The m is an integer of 3 or more and 300 or less. H is a hydrogen atom.

To provide a metal-based structure or nanoparticles whose homogeneity is not deteriorated and whose sticking formation is easy, and a production method thereof with a high safety. A metal-based structure comprises a hydrogen compound, cluster, or an aggregate thereof, represented by the general formula: M.sub.mH. The M is a metal-based atom. The m is an integer of 3 or more and 300 or less. H is a hydrogen atom.

Provided is a method for producing nickel powder from a nickel ammine sulfate complex solution, comprising treatment steps of: (1) a seed crystal production step of producing nickel powder having an average particle size of 0.1 to 5 m; (2) a seed crystal addition step of adding the nickel powder obtained in the step (1) as seed crystals to form a mixed slurry; (3) a reduction step of forming a reduced slurry containing nickel powder formed by precipitation of a nickel component in the mixed slurry on the seed crystals; and (4) a growth step of performing solid-liquid separation to separate and recover the nickel powder as a solid phase component and then blowing hydrogen gas into a solution prepared by adding the nickel ammine sulfate complex solution to the recovered nickel powder to grow the nickel powder to form high purity nickel powder.

Provided is a method for producing nickel powder from a nickel ammine sulfate complex solution, comprising treatment steps of: (1) a seed crystal production step of producing nickel powder having an average particle size of 0.1 to 5 m; (2) a seed crystal addition step of adding the nickel powder obtained in the step (1) as seed crystals to form a mixed slurry; (3) a reduction step of forming a reduced slurry containing nickel powder formed by precipitation of a nickel component in the mixed slurry on the seed crystals; and (4) a growth step of performing solid-liquid separation to separate and recover the nickel powder as a solid phase component and then blowing hydrogen gas into a solution prepared by adding the nickel ammine sulfate complex solution to the recovered nickel powder to grow the nickel powder to form high purity nickel powder.

Provided is a method for producing nickel powder from a nickel ammine sulfate complex solution, comprising treatment steps of: (1) a seed crystal production step of producing nickel powder having an average particle size of 0.1 to 5 m; (2) a seed crystal addition step of adding the nickel powder obtained in the step (1) as seed crystals to form a mixed slurry; (3) a reduction step of forming a reduced slurry containing nickel powder formed by precipitation of a nickel component in the mixed slurry on the seed crystals; and (4) a growth step of performing solid-liquid separation to separate and recover the nickel powder as a solid phase component and then blowing hydrogen gas into a solution prepared by adding the nickel ammine sulfate complex solution to the recovered nickel powder to grow the nickel powder to form high purity nickel powder.

Provided is a method for producing fine nickel powder used as suitable seed crystals for producing nickel powder from a solution containing a nickel ammine sulfate complex. The method for producing nickel powder sequentially includes: a mixing step of adding, to a solution containing a nickel ammine sulfate complex, a dispersant containing a sulfonate and an insoluble solid which is insoluble in the solution to form a mixed slurry; a reduction and precipitation step of charging a reaction vessel with the mixed slurry and then blowing hydrogen gas into the mixed slurry in the reaction vessel to reduce nickel complex ions contained in the mixed slurry to form nickel precipitate on a surface of the insoluble solid; and a separation step of separating the nickel precipitate on the surface of the insoluble solid from the surface of the insoluble solid to form nickel powder.

Provided is a method for producing fine nickel powder used as suitable seed crystals for producing nickel powder from a solution containing a nickel ammine sulfate complex. The method for producing nickel powder sequentially includes: a mixing step of adding, to a solution containing a nickel ammine sulfate complex, a dispersant containing a sulfonate and an insoluble solid which is insoluble in the solution to form a mixed slurry; a reduction and precipitation step of charging a reaction vessel with the mixed slurry and then blowing hydrogen gas into the mixed slurry in the reaction vessel to reduce nickel complex ions contained in the mixed slurry to form nickel precipitate on a surface of the insoluble solid; and a separation step of separating the nickel precipitate on the surface of the insoluble solid from the surface of the insoluble solid to form nickel powder.

Provided is a method for producing fine nickel powder used as suitable seed crystals for producing nickel powder from a solution containing a nickel ammine sulfate complex. The method for producing nickel powder sequentially includes: a mixing step of adding, to a solution containing a nickel ammine sulfate complex, a dispersant containing a sulfonate and an insoluble solid which is insoluble in the solution to form a mixed slurry; a reduction and precipitation step of charging a reaction vessel with the mixed slurry and then blowing hydrogen gas into the mixed slurry in the reaction vessel to reduce nickel complex ions contained in the mixed slurry to form nickel precipitate on a surface of the insoluble solid; and a separation step of separating the nickel precipitate on the surface of the insoluble solid from the surface of the insoluble solid to form nickel powder.

A method for manufacturing nickel powder whereby a reduction in production efficiency due to abrasion of a flash vessel connected to a pressurized container can be suppressed when nickel powder is generated using the pressurized container and subsequently recovered. The method for manufacturing nickel powder comprises charging a pressurized container with a nickel sulfate ammine complex solution and seed crystals, adding hydrogen gas to the pressurized container, and reducing the nickel included in the nickel sulfate ammine complex solution, wherein, when a nickel powder slurry obtained in the pressurized container is extracted to a flash vessel connected to the pressurized container, the slurry is extracted to the flash vessel while the supply rate of the nickel ammine complex solution to the pressurized container and/or the extraction rate of the nickel slurry from the pressurized container is controlled so the liquid level in the pressurized container is in a fixed range.