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

Definitions

• ABSTRACT [30] Foreign Application Priority Data in the production of B type carbonyl nickel powder.
• decomposer The production of carbonyl nickel powder by thermal decomposition has been carried out on an industrial scale for many years.
• the form of decomposer commonly used consists of a substantially cylindrical vessel with heated walls mounted with its axis vertical, the carbonyl vapour being introduced at the top and the powder falling into the bottom, where it is collected and discharged.
• the powder produced may assume one of two forms. These are the so-called A carbonyl nickel powder, which consists of discrete particles, and the so-called B powder, which consists of agglomerates of interlocking filaments or chains of interconnected (aggregated) particles.
• B powder has a low bulk density, generally less than 1.5 g/ml, and a microscopic appearance of small spongy flakes. The size of the aggregates of particles making up the chains can vary widely.
• the present invention relates only to processes in which B powder is produced.
• B powder of very low bulk density e.g., less than 1 g/ml (grams per millilitre) or even less than 0.8 g/ml
• B powder of very low bulk density e.g., less than 1 g/ml (grams per millilitre) or even less than 0.8 g/ml
• part of the large amount of carbonyl introduced tends to decompose near or even on the walls, so that a layer of fluffy powder builds up on the walls. This interferes with heat transfer through the walls, and the plant must be periodically shut down in order to remove it. This is an inconvenient, dirty and time-consuming procedure.
• B powder having a given low bulk density is obtained with a lower carbonyl input or decomposition temperature, and thus a lower wall temperature, with a carbonyl decomposition process wherein the fine particles suspended in the exit gases from the decomposer are kept separate from the main product.
• the rate of input of nickel carbonyl, the decomposition temperature, and the amount of any diluent gas introduced are correlated to provide that fluffy nickel powder is not deposited on the heated walls of the decomposer, and fine nickel powder suspended in gases leaving the decomposer is recovered separately, c.g., by filter, from the B type nickel powder settling at the bottom of the decomposer.
• the fine particles recovered from the gases have :1 Fisher particle size of less than 2 pm, (microns) e.g., from 1.5 to 1.9 pm, and amount to from 10 to 17%, e.g., about 15%, by weight of the total amount of powder produced.
• the nickel carbonyl vapour fed to the decomposer is advantageously diluted, preferably with carbon monoxide or other inert diluent gas, so that carbonyl concentration is preferably in the range of 10 to by vol ume of the total gas entering the decomposer.
• a diluent a small amount of an agent for promoting solid nuclei formation for the powder, preferably oxygen, for the purpose of reducing the shrinkage on sintering without substantially changing the bulk density, as described in US. Pat. No. 2,844,456.
• oxygen is introduced in an amount of from 0.01 to 0.06% by volume of the total gas entering the decomposer, but larger amounts, up to not more than 0.1%, can be used, though these tend to lower the Fisher value of the powder.
• B nickel powder was produced by the decomposition of nickel carbonyl vapour mixed with carbon monoxide in a decomposer consisting of an upright cylindrical vessel 2m (metres) in diameter and 10m high, the walls of which were externally heated electrically.
• the internal temperatures were measured by means of thermocouples mounted on a vertical axis 20.3 cm from the walls at various levels, and the wall temperature was measured at various levels by thermocouples mounted in the walls, three thermocouples being placed at each level apart around the circumference of the wall.
• the fine powder was recovered separately from the powder settling at the bottom of the decomposer.
• the internal and wall temperatures measured as described above were as set forth in the following Table l, the internal temperatures being the same in the two series of 5 the tests but the wall temperatures in the upper part of the decomposer being lower in the second series.
• Powder produced by the process of the invention is particularly useful for the production of sintered supports for the plates of nickel alkaline batteries. This is due. inter alia, to the fact that separation of the fines according to the invention reduces the linear shrinkage of the powder produced according to the invention, on sintering, resulting in high porosity values and reduced sinterability.
• the fine particles have a remarkably low carbon content, preferably not more than 0.03% by weight and generally about 0.02%. compared with 0.l2 to 0.2% for the balance of the powder.
• the fine powder obtained with the invention has a high shrinkage on sintering typically of about and is particularly useful for making sintered filters.
• the fine particles can be transformed into flake fonn by mechanical treatment and in this form can be used as a selective light reflecting means in graphic displays actuated magnetically to provide visible patterns.
• the rate of nickel carbonyl input is in the range of from 70 to 1 17 m /h (cubic metres per hour), that is to say a total gas input in the range of from 500 to 650 m /h with the concentration of nickel carbonyl in the range of from 14% to l8% by volume of the total gas entering the decomposer, and the temperature of the inner wall of the decomposer is in the range of from 400 to 500C. and advantageously not greater than 470C.
• nickel carbonyl concentration is in the range of l0% to by volume of the total gas entering the decomposer.
• a process according to claim I utilizing a diluent gas comprising an agent for promoting solid nuclei formation for the powder.
• a process according to claim 3 wherein the promoting agent is oxygen in an amount up to 0.1% by volume of the total gas entering the decomposer.
• a process according to claim 1 utilizing diluent gas comprising an inert gas, with or without a promoting agent gas.
• a process as set forth in claim I having a diluent comprising oxygen wherein the nickel carbonyl input rate, the decomposition temperature, the amount of diluent gas and the separate recovery of powder suspended in exit gases are controlled in mutual correlation to provide a fines product characterized by a carbon content up to 0.03%, a Fisher particle size up to L9 microns and a shrinkage on sintering typically about 257:.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Powder Metallurgy (AREA)

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Cited By (3)

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Citations (3)

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• 1973
  • 1973-05-15 GB GB2296173A patent/GB1468001A/en not_active Expired
• 1974
  • 1974-05-06 US US467127A patent/US3918955A/en not_active Expired - Lifetime
  • 1974-05-09 CA CA199,395A patent/CA1016780A/en not_active Expired
  • 1974-05-13 FR FR7416415A patent/FR2229774B1/fr not_active Expired
  • 1974-05-14 DE DE2423309A patent/DE2423309A1/de active Pending
  • 1974-05-14 JP JP49053816A patent/JPS5041757A/ja active Pending

Patent Citations (3)

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