Abstract: A ceramic cutting tool configured as multiphase ceramic with an improved resistance to wear of the edge area or edge layer consists of a base ceramic and of a sacrificial phase as well as eventually additives and primary hard material phases and an eventually multilayered edge area or edge layer resistant to wear, hard, not deposited made of at least one hard material phase, whereby the edge area is intimately intergrown with the starting ceramic and which is formed by aging the starting ceramic in a defined atmosphere.

Abstract: A composite ceramic-metal material has an Al2O3 matrix interpenetrated by a network of a ductile metal phase with a higher meltin temperature than aluminum and which makes up 15 to 80 vol. % of its total volume. The Al2O3 matrix forms a coherent network that makes up 20 to 85 vol. %, and the material contains 0.1 to 20 atom % aluminide. To produce this composite material, a green body shaped by powder metallurgy and which contains a finely divided powdery mixture of Al2O3 and optionally other ceramic substances, as well as one or several metals or metal alloys different from aluminum and to which 0.1 to 20 atom % aluminum are added, in relation to the metal proportion, is sintered. The composition is selected in such a way that maximum 15 vol. % aluminide phase can be formed in the finished sintered body.

Abstract: The invention relates to a process for the production of a cerametallic composite part containing a phase rich in Al.sub.2 O.sub.3 which is permeated by a metallic phase consisting predominantly of aluminides, in which process a preform that may have been sintered and comprises at least one oxidic compound reducible by aluminium and maybe also non-oxidic compounds or elements is reacted with molten aluminium or aluminium alloy until aluminide and Al.sub.2 O.sub.3 have formed at least in the surface layer. Composite parts fabricated in this way can serve as wear-resistant or/and high-temperature-resistant components in the construction of machinery, apparatus, engines and turbines, for applications under corrosive or/and oxidizing conditions, as functional elements, especially high-performance brake elements and as electrical or magnetic functional elements.

Abstract: A ceramic formed body containing a) 5 to 70 vol % of at least on intermetallic aluminide phase which additionally may contain aluminum or/and aluminum alloy, and b) 30 to 95 vol % of one or more ceramic phases which form a solid interconnecting skeleton and wherein the intermetallic phase or phases consist of predominantly interconnected areas with average sizes of 0.1 to 10 .mu.m, is obtained by sintering, in a non-oxidizing atmosphere, of a powder metallurgically green body which consists of a mixture of finely dispersed powder of aluminum, one or more ceramic substances and maybe further metals such that the mixture contains at least one oxide ceramic or/and metallic powder which, during sintering, reacts with aluminum thereby forming an aluminide and maybe Al.sub.2 O.sub.3.

Abstract: A reaction-formed moulded ceramic body containing mullite is described which is obtainable by heat treating a body moulded from a finely dispersed powder mixture of aluminium, Al.sub.2 O.sub.3 and a material containing Si in an atmosphere containing oxygen. Due to their properties, in particular their low shrinkage of 0 to 4% on average, the moulded bodies are very well suited for use as wear-resistant and/or high temperature-resistant components in the construction of machines, apparatuses and motors, as a cutting tool, as a component for bearings and/or seals and as a functional part in electronic instruments.

Abstract: A ceramic moulded body containing at least 10 vol. % fine-grained Al.sub.2 O.sub.3, and a process for its production(a) milling aluminium metal in powder form alone or together with Al.sub.2 O.sub.3 or/and if desired further suitable inorganic substances for ceramic formation in a non-aqueous liquid in the presence of oxygen until 10 to 80% of the metallic aluminium powder has reacted to form one or several aluminium oxidation precursors from the group amorphous Al.sub.2 O.sub.3, .gamma.-Al.sub.2 O.sub.3 and aluminium-organic compounds and the powder has a maximum oxidation rate between 510.degree. and 610.degree. C. according to differential thermoanalytical measurement;(b) molding the powder of step (a) into a green body;(c) slowly heating the green body in an atmosphere containing oxygen to a temperature which is below the melting temperature of aluminium until at least 50% of the metallic aluminium powder remaining after the milling has reacted to Al.sub.2 O.sub.

Abstract: The present invention provides a zirconium oxide-containing ceramic formed body, wherein it is also free from amorphous phases on the grain boundaries and triple points, displays a shrinkage of less than 5% in comparison with its green body and is obtainable by reaction sintering of a green body, said ceramic formed body being formed from a mechanically alloyed mixture which contains or consists of at least 1% by volume zirconium metal powder and at least 20% by volume of one or more metallic powders selected from the elements magnesium, aluminum, copper, selenium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, strontium, yttrium, niobium, cerium, hafnium and tantalum, as well as the oxides thereof and zirconium oxide, sodium oxide, potassium oxide and lithium oxide.

Abstract: The instant invention is directed to the production of ceramic bodies of at least one disperse inorganic component embedded in a phase of aluminum oxide by producing a mixture of aluminum powder and optionally an alloying element, and a disperse inorganic component which contains at least 40 vol. % of aluminum oxide, attriting the mixture, forming a body, and sintering the body in an oxidizing atmosphere.

Abstract: A novel method of sintering Si.sub.3 N.sub.4 shaped bodies which method comprises grinding Si.sub.3 N.sub.4 with the use of a grinding material down to a surface area magnitude of 10.5 to 35 m.sup.2 /g and an average particle size from 0.2 to 0.005 .mu.m, shaping the powder obtained, and sintering the compact under inert gas or nitrogen at a temperature from 1700.degree. to 1900.degree. C.

Abstract: The present invention provides a fine-grained ceramic formed body of 0.5 to mole % rare earth oxide and 0.5 to 7 mole % MgO-containing ZrO.sub.2, wherein the cubic granules thereof are coated with Mg-Al spinel particles.The present invention also provides a process for the production of such formed bodies, wherein a ZrO.sub.2 powder alloyed with rare earth oxide, which contains small amounts of Al.sub.2 O.sub.3, is pressed and sintered in the presence of MgO at a temperature of from 1400.degree. to 1600.degree. C. and optionally subsequently tempered at a temperature of from 1200.degree. to 1350.degree. C.

Abstract: Ceramic moldings containing finely crystalline cordierite are described, which are obtainable by the intensive grinding of precrystallized cordierite powder, mixing the powder with second additive phases of higher modulus of elasticity, shaping the mixture, and sintering the greenware thus obtained in a siliceous atmosphere at temperatures between 900.degree. and 1400.degree. C. The moldings according to the invention have not only good mechanical strengths but also outstanding dielectric and thermal properties; they are therefore especially suitable for use as dielectrics and as thermal insulating components.

Abstract: The present invention provides a fibre-strengthened ceramic formed body with improved mechanical strength, wherein it contains at least 15% by volume of zirconium dioxide, hafnium dioxide or zirconium dioxide/hafnium dioxide composition in the form of monoclinic crystals and an amount of inorganic fibres sufficient for increasing the strength, which is obtainable by hot pressing a mixture of ceramic matrix materials, at least 15% by volume of tetragonal zirconium dioxide, hafnium dioxide or zirconium dioxide/hafnium dioxide composition particles and the fibres at a temperature above the tetragonal.fwdarw.monoclinic transition temperature.The present invention also provides a process for the production of such a ceramic formed body.

Abstract: A ceramic body of zirconium dioxide containing, if desired, aluminum oxide, and partially stabilized with yttrium oxide and/or one or more rare earth oxides (e.g., cerium dioxide) and/or magnesium oxide and/or calcium oxide is partially stabilized with 0.5 to 5 mole-% of yttrium oxide and/or 5 to 12 mole-% of magnesium oxide and/or calcium oxide and/or cerium dioxide or one or more rare earth oxides, is 30 to 100% in the tetragonal lattice modification and has in the surface region a content of yttrium oxide, cerium dioxide, magnesium oxide, calcium oxide or rare earth oxide that is 1 to 20 mole-% higher than the average content, such that the body is coated with a thin, PSZ-like layer in a more highly stabilized tetragonal or with a layer that is predominantly in the cubic lattice form.

Abstract: The present invention is concerned with a ceramic formed body comprising a ceramic matrix and at least one phase of ceramic incorporation material dispersed therein, characterized by a dense, microcrack-free ceramic base matrix and compressive zones incorporated therein which consist of a mixture of the base matrix material with unstabilized zirconium dioxide particles which are predominantly monoclinic at ambient temperature.The present invention is also concerned with a process for the production of such ceramic formed bodies and with the use thereof as constructional elements in the hot region of heat engines.

Abstract: A ceramic formed body having high temperature change resistance and stren and being composed of a ceramic matrix with dispersed particles of ZrO.sub.2, HfO.sub.2, or mixture thereof, is formed of a powdered ceramic material which is a precursor to the matrix material of the ceramic matrix, mixed with a compound which can form ZrO.sub.2, HfO.sub.2 or mixture thereof upon reaction with the ceramic material, and thereafter densely sintered below the reaction temperature. The sintered body is then heat treated above the reaction temperature to convert the precursor ceramic material into the matrix material and form the ceramic body with in situ formation of the dispersed particles.

Abstract: A method of preparing a ceramic body of high toughness from an aluminum oxide matrix forming ceramic material by using a ceramic embedment material to generate tensile stresses for the formation of controlled microfissures, is provided. The ceramic embedment material comprises 4 to 25% of the volume of the body to be formed, of unstabilized zirconium dioxide and/or hafnium dioxide with a particle size of 0.3 to 1.25 um. This is mixed with the aluminum oxide material and the mixture is sintered by hot-pressing in a mold at a temperature of 1400.degree. C. to 1500.degree. C.

Abstract: A high-strength ceramic laminated tube comprising an inner tube of ceramic material and at least one outer tube of a metal or ceramic material shrunken onto the inner tube is provided, e.g., a ceramic tube capable of withstanding the mechanical stresses which occur in, e.g., a gun barrel, or in a bearing subjected to great stress.

Abstract: In a process for the production of dispersion ceramics by sintering or hot pressing of a mixture of a matrix-forming ceramic material and of at least one ceramic embedment material dispersible therein which at the sintering temperature of the ceramic and at room temperature is present in different enantiotropic solid modifications of different densities, a ceramic embedment material is employed which is divided into at least two groups of different, substantially uniform particle sizes, each group having different lower phase-transition temperatures.

Abstract: A sintered ceramic body of high toughness, consisting of an isotropic ceramic matrix (e.g. Al.sub.2 O.sub.3) and at least one therein-dispersed phase (ZrO.sub.2, HzO.sub.2) of ceramic embedment material formed from a powder consisting of particles having an average diameter from 0.3 to 1.25 .mu.m, wherein the ceramic embedment material is present in different enantiotropic solid modifications at the firing temperature of the ceramic body and below the firing temperature, whose densities are substantially different, and the ceramic body is shot through with extremely fine microfractures in high density.

Abstract: A ceramic body of zirconium dioxide containing, if desired, aluminum oxide, nd partially stabilized with yttrium oxide and/or one or more rare earth oxides (e.g., cerium dioxide) and/or magnesium oxide and/or calcium oxide is partially stabilized with 0.5 to 5 mole-% of yttrium oxide and/or 5 to 12 mole-% of magnesium oxide and/or calcium oxide and/or cerium dioxide or one or more rare earth oxides, is 30 to 100% in the tetragonal lattice modification and has in the surface region a content of yttrium oxide, cerium dioxide, magnesium oxide, calcium oxide or rare earth oxide that is 1 to 20 mole-% higher than the average content, such that the body is coated with a thin, PSZ-like layer in a more highly stabilized tetragonal or with a layer that is predominantly in the cubic lattice form.