Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B5/00—General methods of reducing to metals
  • C22B5/02—Dry methods smelting of sulfides or formation of mattes
  • C22B5/20—Dry methods smelting of sulfides or formation of mattes from metal carbonyls
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
  • B22F9/30—Making metallic powder or suspensions thereof using chemical processes with decomposition of metal compounds, e.g. by pyrolysis
  • B22F9/305—Making metallic powder or suspensions thereof using chemical processes with decomposition of metal compounds, e.g. by pyrolysis of metal carbonyls
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B23/00—Obtaining nickel or cobalt
  • C22B23/06—Refining
  • C22B23/065—Refining carbonyl methods
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S75/00—Specialized metallurgical processes, compositions for use therein, consolidated metal powder compositions, and loose metal particulate mixtures
  • Y10S75/953—Producing spheres

Definitions

• Carbonyl nickel powder with low carbon contents is produced by decomposing nickel carbonyl mixed with ammonia and in the substantial absence of water vapor in a decomposer having inner surfaces of nitrided steel.
• This invention relates to carbonyl nickel powder, that is to say powder made by the thermal decomposition of nickel carbonyl vapour in the hot free space of a decomposer.
• carbonyl nickel powder in this way has been carried out on an industrial scale for many years, and it is well-established that according to the conditions of temperature, the concentration of carbonyl, and the presence or absence of diluent gases, e.g. carbon monoxide, the power produced may assume one of two forms. These are the so-called A carbonyl nickel powder, which consists of discrete particles with an irregular spiky surface, and the so-called B powder, which consists of agglomerates of interlocking filaments or chains of interconnected (aggregated) particles which again are individually irregular. Type B powder has a low bulk density and has a microscopic appearance of small spongy flakes. The size of the aggregates of particles making up the chains can vary widely.
• the powder product from the decomposer ordinarily contains a small amount, e.g. from 0.05 to 0.08% by weight, of carbon. Most of the carbon is present in the nickel particles, either chemically combined with the nickel or as graphite. However, the product is almost always contaminated with a very small proportion, generally less than 0.01% by weight, of particles of very high carbon content, e.g. 50% or more. For many uses of the powder the presence of these carbonaceous particles is most undesirable. Thus when the powder is sintered in thin layers the carbon particles burn away leaving holes.
• the thin layer is a protective coating on steel the protection afforded is thereby reduced, and in the case of a porous product such as a fuel cell electrode, the pore distribution is rendered nonuniform and they must therefore be removed from the powder before it is used.
• the carbonaceous particles are larger than the nickel particles this can be done by screening, but it is not always possible to eliminate all of them in this way.
• Another object of the invention is to produce carbonyl nickel powder of which the particles have a lower carbon content.
• the present invention is based on the discovery that the carbonaceous particles are formed by the thermal decomposition of carbon monoxide at the surfaces of the steel walls and internal fittings of the decomposer, and that their formation can be wholly or partly prevented by nitriding these surfaces.
• the invention consists in producing nickel powder by decomposing nickel carbonyl vapour in the substantial absence of water vapour in the hot free space of a decomposer whose steel inner surface have been nitrided.
• the nitriding of the steel decomposer surfaces may conveniently be performed by beating them in contact with ammonia gas, e.g. by leading ammonia gas into or through the decomposer while the walls and other internal surfaces are heated to a high enough temperature for a surface layer of iron nitride to be formed by reaction with the ammonia.
• a suitable temperature is 500 C., and the heating should be continued for at least 1 hour, e.g. for 3 hours.
• the effectiveness of a nitriding treatment may be assessed by simultaneously treating a test-piece of steel of similar composition in the decomposer and then exposing it at 500 C. to carbon monoxide containing small amounts of nickel carbonyl vapour, for two hours. If no black deposit of carbon is formed on the steel surface, the treatment is eifective.
• nitriding as a separate pre-treatment before introducing the carbonyl into the decomposer, it may if desired be done by passing ammonia into the decomposer while a previous batch of nickel powder is being made and the decomposer walls are therefore heated. It will be appreciated that the full benefit of this treatment in preventing the formation of carbonaceous particles will not be obtained until the decomposer walls have been fully nitrided. In whichever way the treatment is performed, the internal surfaces of the decomposer must of course be initially clean.
• a further slight reduction in the combined carbon content of the powder results if a small proportion of oxygen, e.g. from 0.01 to 0.1% by volume of the gas feed, is introduced during the decomposition as well as the ammonia.
• the ratio of ammonia to oxygen is preferably 4:3 by volume. Whether or not oxygen is introduced, the proportion of ammonia required is very small, as little as 0.01% by volume of the gas feed to the decomposer generally being effective.
• the The invention is applicable to the production of nickel powder product was free from black carbonaceous partipowder by decomposing nickel carbonyl vapour not only cles.
• the carbon contents of the powders made with amin concentrated form but also when it is diluted with carmonia additions were lower than those made under similar bon monoxide, which may be present in excess. It can be conditions without ammonia after the decomposer walls used to make both type A and type B powder.
• the form 20 had been nitrided, and those made in the presence of both of the powder particles is not affected by the presence of ammonia and oxygen are lower still.
• a process in which non spherical nickel powder sub- The features of the process are illustrated by the restantially free from particles of carbon is produced by the sults of a series of experiments in which nickel carbonyl decomposition of nickel carbonyl vapour in the substanvapour diluted with about 11 times its volume of carbon tial absence of water vapour in the hot free space of a monoxide (nickel carbonyl concentration 69% by decomposer having nitrided steel inner surfaces. volume) was fed into an externally-heated 10-inch diam- 2.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Powder Metallurgy (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Catalysts (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Applications Claiming Priority (2)

Publications (1)

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Cited By (3)

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Citations (1)

Family Cites Families (1)

• 0
  • BE BE668506D patent/BE668506A/xx unknown
• 1964
  • 1964-08-19 GB GB33907/64A patent/GB1061579A/en not_active Expired
• 1965
  • 1965-08-13 NL NL6510618A patent/NL6510618A/xx unknown
  • 1965-08-14 DE DE19651483145 patent/DE1483145A1/de not_active Withdrawn
  • 1965-08-16 CH CH1149365A patent/CH442761A/fr unknown
  • 1965-08-16 CH CH1149265A patent/CH427302A/fr unknown
  • 1965-08-16 US US480106A patent/US3367767A/en not_active Expired - Lifetime
  • 1965-08-16 US US481157A patent/US3367768A/en not_active Expired - Lifetime
  • 1965-08-18 SE SE10789/65A patent/SE329009B/xx unknown
  • 1965-08-18 ES ES0316605A patent/ES316605A1/es not_active Expired
  • 1965-08-18 SE SE10790/65A patent/SE329010B/xx unknown
  • 1965-08-19 NL NL656510895A patent/NL144849B/xx unknown
  • 1965-08-19 AT AT763365A patent/AT268699B/de active
  • 1965-08-19 BE BE668505A patent/BE668505A/xx unknown
• 1971
  • 1971-06-22 NL NL7108568A patent/NL7108568A/xx unknown

Patent Citations (1)

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