Bayer Aktiengesellschaft

Lothar Schonfelder

Gerhard Franz

Holger Ohst

Stefan Roth

Rolf Dhein

Heinrich Heine

Gerhard Leimer

A process for the production of dense silicon nitride materials by the nitriding of moulded bodies of silicon powder, silicon nitride powder and sintering additives under normal pressure and sintering of the moulded bodies at normal nitrogen pressure as well as silicon nitride materials produced correspondingly.

Process for the production of dense silicon nitride materials

A molding compound is disclosed which is useful in producing inorganic sintered moldings, which contains, in addition to an inorganic powder, a binder system containing a thermoplastically processable, partially crystalline polyester and an additional low molecular weight compound which may react with the polyester. A process is disclosed for preparing a sintered molding by injection molding of the molding compound, removal of the binder system, and sintering.

Thermoplastic molding compounds for the production of inorganic sintered

A moulding compound is described which contains an inorganic powder together with a binder system. The binder system contains a thermoplast having a melting temperature greater than 180.degree. C. A process is also described for making a sintered molding from the molding compound, which process includes the steps of injection moulding, removal of the binder by heating, and sintering.

Moulding compounds for the production of inorganic sintered mouldings

The process of preparing silicon nitride is improved by reacting silicon-oxygen compounds and a carbon-containing material in an ammonia or ammonia/nitrogen atmosphere at 1300.degree. to 1600.degree. C.

Process for the preparation of silicon nitride

An improved process for preparation of silicon nitride powder having a low carbon content comprises treating silicon nitride powder with an atmosphere containing chlorine gas at temperatures from 600.degree. to 1050.degree. C. and then with an atmosphere containing gaseous oxygen.

Process for the preparation of silicon nitride low in carbon content

In the production of an .alpha.-iron oxide pigment by the hydrothermal treatment of a trivalent iron-containing solution or suspension, the improvement which comprises adding to the solution or suspension prior to the hydrothermal treatment active .alpha.-iron oxide seeds with lamellar or disc-like crystal form and a specific surface of at least 10 m.sup.2 /g, whereby the resulting pigment is lamellar with an Fe.sub.2 O.sub.3 content of at least 88%, an average particle diameter of from 0.5 to 20 .mu.m, an average ratio of diameter to thickness of from 20 to 100, and an almost normally distributed particle size distribution, the relative standard deviation of which, based on the average value of the normal distribution, is less than 0.3. The product has superior coloring properties and is used as a precursor compound for the production of lamellar magnetic pigments with superior magnetic properties.

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Coburg, Germany

Lothar Schonfelder