Degussa Aktiengesellschaft

Hans-Hermann Beyer

Wolfgang Weber

Kurt Eiermann

Peter Biberbach

Walter Diehl

Hans-Martin Ringelstein

Klaus Zimmermann

Ulrich Baudis

Karlheinz Eckert

Karl-Anton Starz

Roland Gerner

A precious-metal material for articles of jewelry and having low specific weight, high resistance to corrosion, in spite of a low content of precious metals, and free from toxic constituents which consists of 33 to 99 wt. % precious metal powder, 1 to 67 wt. % of a thermosetting organic plastics and 0 to 10% filler.

Precious-metal material for articles of jewelry and a method of

Hard and scratch-proof objects of platinum and palladium or their alloys comprise a boron-containing surface layer which is 20 to 500 .mu.m thick and contains 0.3 to 1.5% by weight boron embedded in the metal lattice.

Surface-hardened objects of alloys of platinum and palladium and method

Wear-resistant hard material layers are prepared on a metal support by applying onto said support a mixture of hard material particles, solder particles and organic binding agents and thereafter soldering the layer by heating. The mixture thus obtained can be applied by means of immersing, screen printing, brushing, spraying or spreading. The stable suspension required for the above steps is prepared by homogeneously grinding the particles together to a particle size from 1 to 20 .mu.m and adding an organic solvent to the binding agent.

Process for the preparation of wear-resistant hard material layers on

Gold powder is inserted in a cavity for the production of fillings in teeth by means of filled gold and this is subsequently hardened mechanically. The moisture sensitivity of this process can be avoided by using a paste made of platelet shaped gold powder with a plastic, organic binder which liquifies at 20.degree. to 45.degree. C. and the mechanical hardening is carried out with ultrasonic.

Process and apparatus for the production of fillings in teeth

Powder of a ductile, mouth resistant metal such as silver, platinum, palladium, aluminum, or titanium, or an alloy thereof, or a cold weldable, mouth resistant synthetic resin, such as a polyacrylate or methacrylate, polycarbonate or polysulfone is worked to a paste with a plastic organic binder which liquifies at 20.degree. to 45.degree. C. This paste is hardened in the tooth cavity by ultrasonic action.

Process for the production of fillings for teeth

There is described a salt bath based on an alkali and/or alkaline earth metal halide with which there can be produced without the use of current adherent and wear resistant boride coatings on metallic workpieces. This bath contains gaseous boron monofluoride or a compound from which there is formed intermediately boron monofluoride. Advantageous there is used a salt bath containing 30-60% BaCl.sub.2, 10-25% NaCl, 1-20% boron oxide or borate, 10-30% NaF, and 1-15% B.sub.4 C.

Salt bath for the currentless production of wear resistant boride layers

It is known to regenerate salt baths for nitriding parts of iron and steel with polymers of organic materials, which polymers, however, could not be used in carburizing salt baths since with them there only are formed slight amounts of carburizing active cyanide, the baths foam, and carbon residues are formed. An excellent regeneration agent for carburizing salt baths is obtained by using polymeric organic compounds of the overall composition [C.sub.6 H.sub.x N.sub.y ].sub.z where x is 3 to 5, y is 5 to 8, and z is 10 to 10,000. These compounds are obtained by reacting formaldehyde with cyanamide and/or dicyandiamide and/or melamine and pyrolytically decomposing the reaction product at 300.degree. to 600.degree. C.

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Kahl, Germany

Hans-Hermann Beyer