Hydrometallurgical Production of Metallic Powders (Patent No: 527062)

Inventor: Schaufelberger, Felix A.

Location: Stanford, USA

Comments: N/A

Description: 527,062

Issued July 3, 1956

Hydrometallurgical Production of Metallic Powders

Sydney Nashner, Fort Saskatchewan, Alberta,
Canada, and Felix A. Schaufelberger, Stamford,
Connecticut, U.S.A.

Application November 5. 1953, Serial No. 656,402

15 Claims

1. In chemical precipitation of elemental metal powder, with concomitant liberation of acid, from aqueous solutions of salts of an inorganic acid and at least one non-ferrous metal of interest selected from the group consisting of cadmium, cobalt, copper, nickel and silver, by reduction with a sulfur-free reducing gas at elevated temperature and superatmospheric pressure; the method of improving the physical properties of so-precipitated metal powder which comprises: subjecting such solution containing dissolved salt of the metal of interest to a nucleation reduction in which a part of the dissolved metal is reduced to a fine seeding precipitate under one set of reducing conditions and using precipitate so-obtained as seeding material in a densification reduction carried out under different reducing conditions, whereby substantially complete precipitation of the dissolved metal as discrete dense particles is obtained.

2. In chemical precipitation of elemental nickel powder, with concomitant liberation of acid, from aqueous solutions of salts of nickel and an inorganic acid by reduction with a sulfur-free reducing gas at elevated temperature and superatmospheric pressure; the method of improving the physical properties of so-precipitated nickel powder which comprises: subjecting such a solution to a nucleation reduction whereby dissolved nickel is reduced to a fine seeding metal precipitate under one set of reducing conditions and using precipitate so-obtained as seeding material in a densification reduction carried out under different reducing conditions, whereby substantially complete precipitation of the dissolved nickel as discrete dense particles is obtained.

6. In chemical precipitation of elemental metal powder, with concomitant liberation of acid, from aqueous solutions of salts of an inorganic acid and at least one non-ferrous metal of interest selected from the group consisting of cadmium, cobalt, copper, nickel and silver, by reduction with a non-sulndizing reducing gas at elevated temperatures and superatmospheric pressure; the method of improving the physical properties of so-precipitated metal powder which comprises: subjecting such solution containing dissolved salt of the metal of interest to a nucleation reduction in which a part of the dissolved metal of interest is reduced to a fine seeding metal precipitate under one set of reducing conditions and using precipitate so-obtained as seeding material in a densification reduction carried out under different reducing conditions; said nucleation reduction being carried out by, providing in said solution a hydrogen ion concentration below that limiting concentration at which reduction of the metal of interest ceases, applying said one set of reducing conditions to said solution without seeding, whereby dissolved metal of interest is precipitated as fine seeding precipitate, maintaining said reducing conditions until a minor proportion of the dissolved metal of interest is precipitated and then stopping said nucleation reduction; and said densification reduction being carried out by applying reducing conditions to a slurry of said seed powder in a solution of dissolved salt of the metal of interest, said slurry having an initial hydrogen ion concentration which is (a) lower than that at which nucleation reduction was initiated (b) at which nucleation without seeding is impracticable but (c) reduction proceeds readily in the presence of said powder; maintaining said slurry under reducing conditions, whereby reduction proceeds by metal deposition on said seed powder with further liberation of acid; providing in said slurry sufficient neutralizing agent to prevent said further liberation from producing, said limiting hydrogen ion concentration before reduction is sufficiently complete, and continuing said conditions until reduction is sufficiently complete.

14. In the chemical precipitation of elemental nickel with concomitant liberation of sulfuric acid from a solution comprising dissolved nickel sulfate by the action of a non-sulfidizing reducing gas.. at elevated temperature and pressure; the combination therewith of the method of densifying precipitated nickel which comprises the steps of: first, subjecting solution to a nucleation reduction initiated at an acid concentration between that for a pH of about 6.7 and 5.0% free sulfuric acid and stopping reduction after precipitating only a minor proportion of the nickel as fine nuclear seed; then providing in a slurry comprising said seed in a solution comprising nickel sulfate, sufficient ammonia to produce a basic pH and convert dissolved nickel to a nickel amine; subjecting said resultant slurry to densification reduction with said reducing gas, whereby reduction occurs by deposition of nickel on said seed with further liberation of sulfuric acid; maintaining said reducing conditions and providing any necessary ammonia to keep the free sulfuric acid concentration below about 1.5% until nickel reduction is sufficiently complete; terminating said reduction at a sulfuric acid concentration between those at about pH 1.5 and about 5.0% free acid and collecting resultant dense, discrete nickel metal powder.