Provided is nickel powder obtained by adding seed crystals to a nickel ammine complex solution and performing hydrogen reduction reaction under high temperatures and high pressures, wherein the nickel powder does not produce dust during handling, and a container can be efficiently filled with the nickel powder. The method for producing nickel powder includes: adding seed crystals and a surfactant having a nonionic or anionic functional group to a solution containing a nickel ammine complex to forma mixed slurry; and subjecting the mixed slurry to hydrogen reduction under high temperature and high pressure conditions in a pressure vessel to obtain nickel powder from the mixed slurry.

Provided is nickel powder obtained by adding seed crystals to a nickel ammine complex solution and performing hydrogen reduction reaction under high temperatures and high pressures, wherein the nickel powder does not produce dust during handling, and a container can be efficiently filled with the nickel powder. The method for producing nickel powder includes: adding seed crystals and a surfactant having a nonionic or anionic functional group to a solution containing a nickel ammine complex to forma mixed slurry; and subjecting the mixed slurry to hydrogen reduction under high temperature and high pressure conditions in a pressure vessel to obtain nickel powder from the mixed slurry.

Provided a production method for reducing the content level of sulfur and carbon which are impurities in nickel powder to improve the quality of nickel powder produced by a complexing reduction method. The method of producing nickel powder having low carbon and sulfur concentrations includes: a complexing treatment of adding a complexing agent to a nickel sulfate aqueous solution to form a solution containing nickel complex ions; maintaining the solution containing nickel complex ions at a solution temperature of 150 to 250 C. in a pressure vessel and blowing hydrogen gas into the solution containing nickel complex ions to perform hydrogen reduction to produce nickel powder; washing the nickel powder with water; and then roasting the nickel powder washed with water in a mixed gas atmosphere of nitrogen and hydrogen.

Provided a production method for reducing the content level of sulfur and carbon which are impurities in nickel powder to improve the quality of nickel powder produced by a complexing reduction method. The method of producing nickel powder having low carbon and sulfur concentrations includes: a complexing treatment of adding a complexing agent to a nickel sulfate aqueous solution to form a solution containing nickel complex ions; maintaining the solution containing nickel complex ions at a solution temperature of 150 to 250 C. in a pressure vessel and blowing hydrogen gas into the solution containing nickel complex ions to perform hydrogen reduction to produce nickel powder; washing the nickel powder with water; and then roasting the nickel powder washed with water in a mixed gas atmosphere of nitrogen and hydrogen.

A fine silver particle-containing composition includes a large number of fine silver particles 2 and a coating layer 4 that covers a surface of each silver particle 2. The silver particle 2 is a so-called nano particle. The silver particle 2 has a scale-like shape. The coating layer 4 consists of an organic compound. The organic compound binds to the silver particle 2. The organic compound suppresses aggregation of the silver particle 2. The composition is in a cake form. A weight ratio of the organic compound with regard to the total amount of the composition is not lower than 2% but not higher than 15%.

A fine silver particle-containing composition includes a large number of fine silver particles 2 and a coating layer 4 that covers a surface of each silver particle 2. The silver particle 2 is a so-called nano particle. The silver particle 2 has a scale-like shape. The coating layer 4 consists of an organic compound. The organic compound binds to the silver particle 2. The organic compound suppresses aggregation of the silver particle 2. The composition is in a cake form. A weight ratio of the organic compound with regard to the total amount of the composition is not lower than 2% but not higher than 15%.

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 an efficient method for producing nickel powder from a solution containing a nickel ammine complex, the method including adding seed crystals to a solution containing a nickel ammine complex and subjecting the resulting mixture to hydrogen reduction under high temperatures and high pressures to produce nickel powder, which makes it possible to maintain the quality of the nickel powder produced and reduce the amount of the seed crystals used. The method for producing nickel powder is characterized by adding seed crystals and a dispersant having an anionic functional group to the solution containing a nickel ammine complex to form a mixture slurry, and subjecting the mixture slurry to pressurized hydrogen reduction treatment by blowing hydrogen into the mixture slurry in a high temperature and high pressure atmosphere to cause a reduction reaction, thereby reducing the nickel ammine complex in the mixture slurry to obtain nickel powder.

Provided is an efficient method for producing nickel powder from a solution containing a nickel ammine complex, the method including adding seed crystals to a solution containing a nickel ammine complex and subjecting the resulting mixture to hydrogen reduction under high temperatures and high pressures to produce nickel powder, which makes it possible to maintain the quality of the nickel powder produced and reduce the amount of the seed crystals used. The method for producing nickel powder is characterized by adding seed crystals and a dispersant having an anionic functional group to the solution containing a nickel ammine complex to form a mixture slurry, and subjecting the mixture slurry to pressurized hydrogen reduction treatment by blowing hydrogen into the mixture slurry in a high temperature and high pressure atmosphere to cause a reduction reaction, thereby reducing the nickel ammine complex in the mixture slurry to obtain nickel powder.