Classifications

• • 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
  • B22F9/02—Making metallic powder or suspensions thereof using physical processes
  • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
  • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/02—Contacts characterised by the material thereof
  • H01H1/021—Composite material
  • H01H1/023—Composite material having a noble metal as the basic material
  • H01H1/0237—Composite material having a noble metal as the basic material and containing oxides
  • H01H1/02372—Composite material having a noble metal as the basic material and containing oxides containing as major components one or more oxides of the following elements only: Cd, Sn, Zn, In, Bi, Sb or Te
  • H01H1/02374—Composite material having a noble metal as the basic material and containing oxides containing as major components one or more oxides of the following elements only: Cd, Sn, Zn, In, Bi, Sb or Te containing as major component CdO
• • 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
  • Y10S75/956—Producing particles containing a dispersed phase

Definitions

• the invention relates to silver powder in which an oxidic or metallic phase is dispersed, and to a method for producing this powder.
• materials for electrical switch contacts should have a low tendency to sweat and a high resistance to erosion.
• the tendency to sweat and the erosion resistance of silver contacts can be significantly improved by adding oxidic phases or by adding a metallic phase that is not soluble in silver (e.g. Ni).
• the amount of such additives such as Cadmium oxide is up to 15% by weight. Spark extinguishing behavior or resistance to erosion when the power is switched off are determined by the type and quantity and degree of distribution of the additives.
• composite materials consisting of two components In addition to composite materials consisting of two components, composite materials consisting of three or more components are also used, e.g. Silver metal metal oxide or silver metal oxide (1) metal oxide (2).
• the structural parameters are in particular the corridor size distribution and the porosity.
• oxide-forming metal can be alloyed with silver. Alloy formation occurs with the exclusion of oxygen, which results in a homogeneous distribution of the oxide-forming metal in the silver. The oxide precipitates are then generated by the internal oxidation process. This process takes place e.g. application for silver and cadmium oxide materials.
• the powder metallurgical production of heterogeneous systems is usually carried out by an intimate mixture of the individual powders with subsequent pressing and sintering.
• the individual metal powders are manufactured e.g. by grinding in the solid state or by atomizing melts.
• chemical and electrolytic processes for producing one-component metal powders are known.
• the thermal decomposition of silver carbonate to fine-grain silver powder or the decomposition of nickel carbonyl at elevated temperature to the known carbonyl nickel powder For example, the thermal decomposition of silver carbonate to fine-grain silver powder or the decomposition of nickel carbonyl at elevated temperature to the known carbonyl nickel powder.
• Another method is the reduction of metal compounds, e.g. is also used to extract metal from natural ores.
• Metal powders can be produced electrolytically by a suitable choice of bath composition, bath temperature and current density and concentration of the electrolyte. Silver powder can be produced with high purity.
• a common method used in the manufacture of silver-cadmium oxide composite material is that of internal oxidation.
• the average grain size of Cadmiumoxidausscheidungen amounts to 5 / um with particle sizes of 1 to 10 / um.
• Desired homogeneous and fine-grained cadmium oxide distribution with particle sizes ⁇ 1 / um cannot be achieved with this method.
• the invention has for its object to provide silver powder which is suitable for the production of electrical contacts with low tendency to sweat, good spark suppression and good erosion behavior, and to provide a method for producing this powder.
• a silver powder to consists of particles in the size range of 1 to 10 /, the cadmium oxide as the precipitation with a grain size ⁇ 0.5 / um included, wherein for the preparation of this powder a common aqueous solution of silver and Cadmium salts, for example in a ratio of 9: 1, are atomized into a hot reactor and thermally decomposed at temperatures below the melting point of the individual components.
• the thermal decomposition takes place either in an oxidizing atmosphere (air) or in a reducing atmosphere (hydrogen, forming gas, water vapor-hydrogen mixtures).
• the homogenization of the individual components of the composite material takes place very effectively in the liquid phase.
• the solvent evaporates suddenly, leaving behind the solid constituents, in which the homogeneity of the element distribution from the liquid phase is practically retained.
• these solid particles continue to react with the surrounding gas in the hot reactor either by decomposition of the metal compound into the metal and gaseous fission products of the metal compound, or by absorption of oxygen in the corresponding metal oxide, or in the case of a reducing atmosphere by reduction Metal connections to metal.
• the process according to the invention has the advantage that no further process steps are necessary after the actual powder production. Moreover, the selection of the composite powders that can be produced is not limited by the fact that a common precipitant must be found for the components contained. The method according to the invention is therefore also very well suited for the production of more than two-component composite materials.
• Compressed air is used as the atomizing gas. With a throughput of 10 liters of solution per hour and 10 m 3 of air per hour, 1 kg of silver powder is produced per hour.
• the size of the resulting silver-cadmium oxide powder particles is between approx. 1 and 5 / um. After sintering the powder, the size of the cadmium oxide precipitates in the finished molded part is 0.2-0.5 / um.
• a mixture of 97 g of silver and 12 g of tin in a mixture of nitric acid and acetic acid is diluted to a total volume of 3.4 liters with water.
• the solution is atomized in the reactor under the same conditions as given in Example 1 and the resulting powder particles are separated from the hot exhaust gases in a centrifugal separator.
• the diameter of the silver-tin oxide particles is approximately 1/3 / .mu.m, the dimensions of the tin oxide precipitates in the sintered molded part being approximately 50 nm.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Composite Materials (AREA)
• Materials Engineering (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Powder Metallurgy (AREA)
• Manufacture Of Switches (AREA)
• Contacts (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6076411

Family Applications (1)

Country Status (4)

Cited By (5)

Families Citing this family (20)

Citations (7)

Family Cites Families (20)

• 1979
  • 1979-07-21 DE DE2929630A patent/DE2929630C2/de not_active Expired
• 1980
  • 1980-07-09 EP EP80103900A patent/EP0022980B1/fr not_active Expired
  • 1980-07-21 JP JP9883180A patent/JPS5651501A/ja active Pending
• 1982
  • 1982-02-16 US US06/348,893 patent/US4396420A/en not_active Expired - Fee Related

Patent Citations (7)

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