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
• • A—HUMAN NECESSITIES
  • A44—HABERDASHERY; JEWELLERY
  • A44C—PERSONAL ADORNMENTS, e.g. JEWELLERY; COINS
  • A44C17/00—Gems or the like
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/71—Ceramic products containing macroscopic reinforcing agents

Definitions

• such a material is obtained by distribution of a precious metal within a matrix or base of ceramic material having a hardness exceeding 6 Mohs, the precious metal occupying 7.5 to 70% of the volume of a body made of the material.
• This invention also relates to a method for producing a hard precious material as defined above, this method broadly comprising thoroughly mixing 30 to 92.5 volume-% of ceramic material having a Mohs hardness exceeding 6 with 7.5 to 70 volume-% of a precious metal, adding to this mixture a small percentage of mineral oxides for assisting sintering and of organic binding agents for facilitating pressing, the mixture in powder form is pressed into the desired shape, the dimensions of this shape exceeding the nominal final dimensions for compensating shrinkage during the following sintering operation, the objects obtained in this way are heated to 100 to 200 C for eliminating said organic binding agents, and then sintering at temperatures ex- .ceeding 1400 C is effected, whereafter the objects are polished in order to obtain the required brilliancy for use.
• the degree of shrinkage varies considerably. It depends particularly on the percentage of precious metal used, but also on the type of the ceramic base or matrix material used.
• the degree of shrinkage may vary from 5 to 25%. Usually it has to be determined by experiment for any type of composition of the material and manufacturing method, in that samples of the material are made and the degree of shrinkage is measured.
• the hard precious material obtained by this method is preferably used for making jewelry. All kindsofjewelry may be made such as rings, chains, bracelets, brooches, long neck chains and bracelets for wrist watches.
• the material may also be used as a sliding body or bearing portion, the precious metal imparting to the composed material its low friction coefficient and the ceramic matrix or base imparting to the material its high resistance to wear.
• the material may particularly well be used for making watch cases.
• the objects After sintering, the objects are polished in order to obtain the necessary brilliancy for their use in jewelry.
• the gold is uniformly distributed in a skeleton of hard ceramic material, namely in corundum when alumina powder is used as a base material as set out above.
• EXAMPLE 1 7.7 volume-% of gold powder are thoroughly mixed with 92.3 volume% of highly pure alumina powder. 1 volume-% of MgO and Ga O is added to this mixture for assisting compaction during sintering.
• An organic binding agent for instance 1 weight-% of polyvinyl alcohol or 0.5 weigth-% of stearic acid are further added for facilitating pressing of the mixture.
• the mixture is now pressed into the desired shape and size, taking care of selecting the dimensions such that after shinkage of the formed object during sintering the required dimensions are obtained.
• the objects are now heated to 100 to 200 C for eliminating the organic binding agents.
• the objects are then sintered at 1600 C, whereafter they are polished as explained above.
• the hardness is of 1250 to 16S0 Knoop this corresponding to 7 to 8 in the scale of Mohs.
• the degree of shrinkage to be taken into consideration is in the order of 14%.
• EXAMPLE 2 14.2 volume-% of gold is thoroughly mixed with 85.8 volume-% of highly pure powder of alumina. The mineral oxides and binding agents of example 1 are added. The mixture is pressed and the objects thus obtained are calcined at a termperature between 100 and 200 C for eliminating the organic binding agents. The objects are then sintered at 1650 C. The Knoop hardness is comprised between 1250 and 1450, this corresponding to a hardness of Mohs of 7 to 7.5. The shrinkage to be considered is in the order of 13%.
• EXAMPLE 3 25,0 volume-% of gold are mixed with 75.0 volumeof highly pure alumina powder. The method then proceeds according to example 1.
• the sintering temperature is 1650 C.
• the Knoop hardness is between 1150' and 1250, this corresponding to a Mohs hardness of 7.
• the shrinkage is in the order of 10%.
• EXAMPLE 4 35.0 volume-% of gold are carefully mixed with 65.0 volume-% of highly pure alumina powder. The method is then carried out according to example 1. Sintering is effected at 1650 C. The Knoop hardness is 920, this corresponding to a Mohs hardness of 6.5. The shrinkage is about 8%.
• EXAMPLE 15.0 volume-% of gold are carefully mixed with 85.0 volume-% of a mixture composed of one mole of NiO and one mole of Ta O
• the same organic binding agents are added as in example 1.
• the objects are pressed and shaped as set out in example 1 and they are then calcined at a temperature between 100 and 200 C for eliminating the organic binding agents.
• the objects are then sintered at 1450 C.
• the Knoop hardness is of 890, this corresponding to a Mobs-hardness of 6.5. A shrinkage of about 15% has to be taken into consideration.
• Ceramic materials having suitable hardness such as for instance BeO (9 Mohs), ZrO with 10% of CaO or of Y O (6.5 to 8 Mohs) or spine] (MgOAl O 8 Mohs). It is also possible to use further ceramic materials such as particularly ceramic glasses (Pyroceram).
• the novel material according to this invention may easily be polished by means of diamond paste similar to the paste used in lapidary mills. In view of its relatively high percentage of precious metal, this percentage being of 28 weight-% in the case of 7.5 volume-% and of 80 weight-% in the case of 45 volume-%, the material may be considered as being a precious material.
• the gold may be recovered by solving it by means of potassium cyanide (KCN). Platinum may be recovered by chemical solution or by melting. Silver may also be recovered by melting.
• An article of jewelry comprising a hard precious material having a hardness exceeding 6 Mohs, said material comprising a precious metal selected from the group consisting of gold, platinum and silver distrib-,

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Manufacturing & Machinery (AREA)
• Structural Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Powder Metallurgy (AREA)
• Adornments (AREA)

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Cited By (21)

Citations (10)

• 1971
  • 1971-12-10 CH CH1801571A patent/CH559018A5/xx not_active IP Right Cessation
• 1972
  • 1972-12-05 US US312346A patent/US3901717A/en not_active Expired - Lifetime

Patent Citations (10)

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