Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
  • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
  • C22C32/0021—Matrix based on noble metals, Cu or alloys thereof
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
  • C22C1/059—Making alloys comprising less than 5% by weight of dispersed reinforcing phases
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1026—Alloys containing non-metals starting from a solution or a suspension of (a) compound(s) of at least one of the alloy constituents

Definitions

• the invention relates to a method for producing a copper powder which contains at least one substance which is insoluble in copper as a dispersoid, and to a copper powder of this type.
• the object of the invention is to produce a copper powder containing the dispersoids in a simple manner.
• the copper powder grains should contain the dispersoids inside as homogeneously as possible.
• This object is achieved by the process according to the invention, in which copper metal granules in excess with an ammonium salt and / or ammonium hydroxide are stirred together with a metered-in salt solution in aqueous solution with the addition of oxygen-containing gas at a pH of at least 4 in a stirring zone and a copper-containing precipitate generates that the precipitate is separated from the copper metal granulate and at temperatures in the range from 150 to 500 ° C.
• the added salt solution is chosen so that it forms a precipitate in the stirring zone, which precipitates together with the copper-containing precipitate.
• the precipitate generated by the salt solution is also referred to here as the dispersoid precursor compound.
• the conditions for generating the copper-containing precipitate can be selected more or less as described in EP patent 0 235 841 and in the corresponding US patent 4,944,935.
• the temperature in the stirring zone will usually be in the range of 5 to 70 ° C.
• the copper powder produced by the process according to the invention contains the dispersoids in the interior of the copper powder grains in largely homogeneously distributed form, which is due to the common precipitation of copper compounds, e.g. Copper hydroxide, with which dispersoid precursor compound is guaranteed.
• the compound mixture is then thermally treated and reduced.
• the dispersoid content of the copper powder is usually about 0.1 to 5% by weight.
• the stirring zone is given copper metal granules e.g. in the form of copper chips or cable scrap, the stirring zone or the stirring container being an aqueous solution, e.g. from NH4OH and NH4Cl or another ammonium salt.
• An aluminum salt solution e.g. Al formate or AlCl3 too, stirs intensely and additionally introduces air or technically pure oxygen into the solution.
• the pH in the stirring zone is kept largely constant at at least 4 and preferably at least 9.
• the pH, which is checked continuously, is preferably kept largely constant by metering in NH4OH. If the pH changes too much during the reaction, this ultimately leads to changes in the dispersoid concentration in the copper powder.
• part of the metallic copper goes into solution and precipitates out after the solubility limit has been exceeded, the oxy salt, hydroxide and oxides forming, and at the same time Al (OH) 3 precipitates.
• the solubility limit for the copper depends on the pH. It has been shown that the aluminum hydroxide precipitation preferably takes place on the copper oxide or copper hydroxide particles which are already in excess in the solution, so that the precipitates mix intimately.
• the aluminum salt solution (e.g. Al formate HCO2Al) is preferably added continuously to the suspension of the stirring zone, the pH in the stirring zone being kept constant.
• the rate of addition of the Al solution is determined as a function of the desired final concentration of the dispersoid in the copper powder. It is particularly advantageous to keep the pH constant during the reaction in the range between 9 and 12 and preferably at least 10. Higher pH values are possible, but not very cheap, since very large amounts of ammonium hydroxide are required for this.
• the reaction is ended while copper metal granules are still present in the stirring zone.
• the copper metal granules are first separated from the suspension running out of the stirring zone, the remaining copper and aluminum hydroxide-containing precipitate is filtered off, washed and dried. Water is used to wash the precipitate. The drying is carried out gently at temperatures from 30 to 80 ° C and then at higher temperatures up to 250 ° C, with a partial or complete conversion of the Cu (OH) 2 to CuO.
• the precipitate is reduced at temperatures in the range from 150 to 500 ° C in the reduction furnace by means of a reducing gas (e.g. H2).
• a reducing gas e.g. H2
• the pulverulent reduction product consists of metallic copper with embedded Al2O3 particles, it is very fine-grained and oxidizes easily on contact with atmospheric oxygen. That is why the Cooling of the product after the reduction under a reducing or inert protective gas, for example nitrogen.
• a reducing or inert protective gas for example nitrogen.
• the powdery reduction product is already ready-to-use copper powder, even if it cannot be ruled out that a certain amount of aluminum oxide can adhere to the surface of the copper grains.
• the pulverulent reduction product is aftertreated in order to remove the adhering aluminum oxide from the surface of the copper grains.
• the reduction product is placed in a dilute acidic or alkaline solution of water and e.g. NaOH or HCl.
• a solids content of the suspension formed is expedient from 10 to 50% by weight, the temperature of the suspension is kept in the range from 40 to 80 ° C. with gentle stirring.
• the product is then washed with water until the wash water is colorless.
• the copper powder should then be dried at about 30 to 60 ° C under vacuum.
• the hydroxide-containing precipitate is filtered off, washed with water and dried (18 hours at 50 ° C. and 2 hours at 220 ° C.).
• the precipitate is reduced at 250 ° C. for 5 hours under a gas mixture consisting of 40% by volume of H2 and 60% by volume of N2, the reduction product thus formed is practically free of copper oxide.
• the reduction product is aftertreated, which is stirred for 2 hours at 80 ° C. in 3 l of an aqueous solution which contains 20 g of NaOH per liter. Then it is washed with water. The washed, Copper powder containing Al2O3 as a dispersoid is kept for further reduction at a temperature of 550 ° C for 30 min under a gas mixture consisting of 40 vol .-% H2 and 60 vol .-% N2. Cooling under N2 inert gas follows. The copper powder produced contains 0.63 wt .-% Al2O3. A test bar 100 mm long and 6 mm in diameter, pressed from this powder and then sintered at 1000 ° C. for 2 hours, has a tensile strength of 545 N / mm 2. The same rod made of pure copper powder has a tensile strength of only 250 N / mm2.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Dispersion Chemistry (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)

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Citations (7)

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• 1994
  • 1994-09-27 DE DE4434393A patent/DE4434393A1/de not_active Withdrawn
• 1995
  • 1995-09-06 EP EP95113955A patent/EP0704544A1/fr not_active Withdrawn
  • 1995-09-25 JP JP7245821A patent/JPH08170111A/ja active Pending
  • 1995-09-26 US US08/534,038 patent/US5707420A/en not_active Expired - Fee Related
  • 1995-09-27 FI FI954590A patent/FI954590L/fi not_active Application Discontinuation

Patent Citations (9)

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