Hoechst Ceramtec Aktiengesellschaft

Hoechst Aktiengesellschaft

Jurgen Heinrich

Rudolf Ganz

Otto Heinz

Jurgen Bottcher

Heinrich Schelter, Deceased

Matthias Simmerl

Gert Lindemann

Friedrich Hessel

Cornelia Boberski

Wolfgang Bocker

Werner Benker

Gunter Riedel

Hartmut Kruner

Ottmar Rosenfelder

Rudiger Herrmann

Jorg Honerlage

Axel Reinhold

Petra Dotsch

Rudiger Herrimann

Matthias Steiner

Reinhard Dillinger

In the permeable structure, which is built up of sheets, continuous channels are arranged in rows and between the rows of channels are formed flow spaces which at opposite sides are bounded bit cover plates. In the flow spaces (4) at least two successive transverse bridges (6) are arranged on the same level, the transverse bridges (6) in at least half of the sheets having a different length (B) and the channels (1) extending essentially perpendicular to the flow spaces (4).

Permeable structure

In the process for producing a homogeneous and finely crystalline silicon nitride ceramic, ceramic powder is milled, mixed with shaping aids, the mixture is shaped into parts and the shaped parts are subsequently sintered in a nitrogen atmosphere. According to the invention, sintering is carried out in a multistage process at temperatures T.sub.max in the range from 1700.degree. to 1900.degree. C. using gas pressures in the range from 0.3 to 50 MPa. In a first temperature stage, a temperature from 0.9 to 0.96.multidot.T.sub.max is maintained over a time period from 10 to 50 minutes at an N.sub.2 pressure from 0.2 to 1.2 MPa, while in a second temperature stage a temperature from 0.97 to 0.985.multidot.T.sub.max is maintained over a time period from 20 to 80 minutes at an N.sub.2 pressure from 3 to 6 MPa. Then the temperature is increased to T.sub.max and the pressure is increased to from 7 to 50 MPa.

Process for producing densely sintered silicon nitride components

In the heat exchanger module, produced by stacking sheet cards provided with openings and subsequently joining the individual cards of the card stack, each sheet card (2) or group of sheet cards of the stack is arranged rotated about a common axis by an angle .alpha. of between 0.degree. and 30.degree. with respect to the preceding sheet card (2) or group of sheet cards, the openings (3) forming helical channels (4).

Heat exchanger module

Silicon slip-casting composition, and process for the preparation thereof A silicon slip-casting composition comprising from 25 to 50% by weight of water and a pulverulent solid component which essentially comprises silicon and inorganic sintering aids is described, where the aqueous phase has a pH in the range from 8 to 9.5. The solid component comprises from 65 to 88% by weight of silicon, from 5 to 24% by weight of Y.sub.2 O.sub.3, from 2 to 9.6% by weight of Al.sub.2 O.sub.3 and from 1 to 5% by weight of SiO.sub.2 on the surface of the Si particles. The mean particle size of the solid component is at most 20 .mu.m, in particular at most 5 .mu.m. The invention also relates to a process for the preparation of the slip-casting composition.

Silicon slip-casting composition, and process for the preparation thereof

For producing a component of silicon-infiltrated silicon carbide, having a porous sliding surface, a component of silicon-infiltrated silicon carbide (composition: 40-95% by weight of SiC, 1-45% by weight of carbon particles of grain size 0.1 to 500 .mu.m and 1-25% by weight of silicon) is machined on parts of the surface, a sliding surface thus being produced. The resulting component is heated in an oxygen-containing atmosphere at temperatures from 700.degree. to 1410.degree. C. until the carbon particles present in the sliding surface have been at least partially oxidized with the formation of pores.

Components of silicon-infiltrated silicon carbide having a porous

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Selb, Germany

Jurgen Heinrich