Process for producing fine particulate metals

Details Process for producing fine particulate metals Process for producing fine particulate metals

1989-07-13

1990-06-26

Sheehan, John P.

Specialized metallurgical processes, compositions for use therei

Processes

Producing or purifying free metal powder or producing or...

B22F 918, B22F 924

Patent

active

049369091

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a process for economically producing fine particulate nickel, tin, lead, cobalt, copper or silver having a particle size of not greater than 3.0 .mu.m with reduced amounts of impurities and oxide films.


PRIOR ART

Long-established processes for producing fine particulate metals are based on electrolysis, reduction with a reducing gas, spraying or mechanical pulverization. Fine particulate metals prepared by these processes are widely used in powder metallurgy and as coloring pigments. However, they are frequently unsatisfactory in such applications as conductive pastes, conductive adhesives, materials capable of being sintered at moderately low temperatures, porous electrodes and metallic powders for injection molding, where a demand for fine particulate metals is recently increasing and where nearly spherical finer particulate metals with further reduced impurities and oxide films are desired. To produce fine particulate metals adapted to these applications there have been proposed various processes based on reduction of a aqueous solution of various metal salts, decomposition of organic metal salts and vapor phase precipitation. By these processes, however, it is generally not easy to produce ultra-fine particulate metals having a primary particle size of not greater than 3.0 .mu.m, and for the production of such ultra-fine particulate metals increased installation and manufacturing costs are required, and moreover, the ultra-fine products are liable to be surface-oxidized, leading to a reduction in yield.
On the other hand, although it has become possible to produce ultra-fine particulate metals having a particle size of from several tens .ANG. to 0,5 .mu.m by a hydrogen-plasma or vacuum evaporation methods, there is posed a problem in that the product is too active because of its ultra-fineness and is inflammable in air in addition to the expensive problem involved.


OBJECT OF THE INVENTION

An object of the invention is to provide a commercial process for economically producing substantially spherical fine particulate nickel, tin, lead, cobalt, copper or silver having a particle size of not greater than 3.0 .mu.m with reduced amounts of impurities and oxide films.


SUMMARY OF THE INVENTION

A process for producing fine particulate metals according to the invention comprises the steps of reducing fine powder of at least one iron compound selected from the group consisting of iron oxide, iron sulfate and iron chloride with a reducing gas to provide fine particulate iron having a particle size of from 0.1 to 3.0 .mu.m and a specific surface area of from 2.0 to 4.0 m.sup.2 /g, bringing the fine particulate iron in contact with an aqueous solution containing ions of at least one metal selected from the group consisting of nickel, tin, lead, cobalt, copper and silver thereby forming fine powder of at least one of said metals having a particle size of from 0.1 to 3.0 .mu.m in the aqueous solution, and recovering the so formed fine particulate metals from the aqueous solution.
More specifically, a process for producing fine particulate metals according to the invention comprises the steps of reducing fine powder of at least one iron compound selected from the group consisting of iron oxide, iron sulfate and iron chloride with a reducing gas to provide fine particulate iron having a particle size of from 0.1 to 3.0 .mu.m and a specific surface area of from 2.0 to 4.0 m.sup.2 /g, adding water to the fine particulate iron, and heating and stirring the resultant mixture to provide a slurry, adding to the heated and stirred slurry an aqueous solution containing ions of at least one metal selected from the group consisting of nickel, tin, lead, cobalt, copper and silver, heating the resulting mixture under stirring thereby forming fine powder of at least one of said metals having a particle size of from 0.1 to 3.0 .mu.m in the aqueous solution, and recovering the so formed fine particulate metals from the aqueous solution.


BRIEF DESCRIPTION OF THE DRAWI

REFERENCES:
patent: 2663633 (1953-12-01), Crowley et al.
patent: 3679399 (1972-07-01), Linton et al.
patent: 3694185 (1972-09-01), Kunda et al.
patent: 4191557 (1980-03-01), Kondis
patent: 4659373 (1987-04-01), Bogdanovi
patent: 4713110 (1987-12-01), Bogdanovic

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