Fraunhofer-gesellschaft Zur Foerderung Der Angewandten Forschung E.v.

Koninklijke Philips Corporation N.V.

Andreas Krell

Thomas Hutzler

Paul Blank

Hongwei Ma

Michel Paul Barbara Van Bruggen

Theo Arnold Kop

Rolf Theo Anton Apetz

Dieter Sporn

Elmar Strassburger

Frank Buse

Rolf T A Apetz

Transparent spinel ceramics, as they can be used, for example, as protective ceramics, and to a method for the production thereof. Transparent spinel ceramics which preferably contain no visible defects and which have an in-line transmission of more than 82% in wavelength ranges of infrared light, measured between 1000 nm and 2500 nm, at sample thicknesses&#x2267;3 mm. Spinel ceramics transparent in wavelength ranges of infrared light which are composed of sintered magnesium aluminum spinel having an average structural grain size of &#x2266;10 &#x3bc;m and having maximally 0.5 mass % overall of homogeneously distributed additives of calcium and/or strontium and/or barium which are present in a concentration, expressed respectively as an oxide, of 0.005 to &#x3c;0.2 mass % CaO and/or 0.005 to &#x3c;0.5 mass % SrO and/or 0.005 to &#x3c;0.5 mass % BaO.

Transparent spinel ceramics and method for the production thereof

Transparent composite pane for safety applications. The composite pane is composed of multiple layers which are arranged behind one another. At least one of the layers is composed of, a plate or plates arranged in a mosaic or in series, of monocrystalline magnesium aluminate spinel.

Transparent composite pane for safety applications

The present invention relates to highly dense translucent and transparent aluminium oxide components for applications, e.g. in the lighting industry, where a fine crystal size has to be obtained and stabilized for use at temperatures of 800&#xb0; C. or more. Disclosed are high-strength polycrystalline alumina products which include 0.001-0.5 weight-% ZrOstabilizing a fine crystal size &#x3c;2 &#x3bc;m or, preferably, &#x3c;1 &#x3bc;m if used at temperatures of 800&#xb0; C. or more. The microstructure exhibits an extremely high relative density enabling a high real in-line transmission &#x3e;30% measured over an angular aperture of at most 0.5&#xb0; at a sample thickness of 0.8 mm and with a monochromatic wavelength of light &#x3bb;, preferably, of 645 nm.

Transparent polycrystalline aluminium oxide

Transparent polycrystalline sintered ceramic of cubic crystal structure. The invention relates to the field of technical ceramic and relates to transparent polycrystalline sintered ceramics of cubic crystal structure for applications with increased mechanical stress, e.g., as protective or armoring ceramic. Provided are sintered ceramics that combine a high transmission of RIT&#x3e;75% of the theoretical maximum value with a distinctly improved hardness. Transparent polycrystalline sintered ceramics of cubic crystal structure with a real in-line transmission RIT&#x3e;75% of the theoretical maximum value measured on 0.8 mm-thick polished plates and for light of a wavelength between 600 and 650 nm, and with an average grain size D in the range of 60 nm&#x3c;D&#x3c;10 &#x3bc;m are provided.

Transparent polycrystalline sintered ceramic of cubic crystal structure

The invention relates to oxide ceramic fiber composite materials that, e.g., according to the invention, are used in energy conversion installations. The present invention discloses a fundamentally new concept for the previously incompatible requirements of improved brittle fracture behavior to secure thermal shock stability and damage tolerance in the temperature range of &#x3c;1000&#xb0; C. and of mechanical high-temperature stability to guarantee long-term form stability (creep resistance) of components. This is attained through oxide ceramic fiber composite materials containing fibers with a monocrystalline structure in some areas with an average coherence length of &#x2267;150 &#x3bc;m, with a mesoscopically resistant fiber/matrix interface along the fiber axis at high temperature, which interface on loading above room temperature in a way associated with the propagation of macrocracks shows delaminations that in their extension along the fiber axis are limited microscopically locally to values smaller than the average fiber coherence length and thereby limited to a maximum of 200 &#x3bc;m. The present invention is also directed to the use of the fiber composite materials for components and/or installations for long-term use at high temperatures.

Oxide ceramic fiber composite materials and use thereof

The invention relates to the field of technical ceramics and specifically relates to a method of synthesis for aluminum oxides of different crystalline structure and to the products obtained by the method. The aim of the invention is to provide a method of producing redispersible nanoparticulate corundum and nanoporous AlOsintered products, the method using precursors and being viable on a commercial scale. To this aim, inter alia, a method of producing redispersible nanoparticulate corundum of an average particle size of DOsintered products according to which organic or chlorine-free inorganic precursors are dissolved or processed to a sol and hydrolyzed. The substance is then dried and calcinated at temperatures of between 350 and 750&#xb0; C.

Method of producing aluminum oxides and products obtained on the basis thereof

The present invention relates to a porous aluminum oxide structure comprising Al O and Zr, the structure having an open porosity greater than about 30% and an average pore size from about 20 nm to about 1000 nm, wherein the Zr, expressed as ZrO , has a concentration less than about 5 weight % of the weight of the Al O . The present invention also relates to a process for producing a porous aluminum oxide structure comprising Al O and Zr, the structure having an open porosity greater than about 30% and an average pore size from about 20 to about 1000 nm, through doping alumina or precursors thereof with a doping effective amount of Zr, wherein the Zr, expressed as ZrO , has a concentration less than about 5 weight % of the weight of the Al O , the process comprising: introducing the Zr into the alumina or the precursors thereof, the Zr being selected from at least one ZrO powder, a solution of a Zr precursor, or mixtures thereof, by admixing the Zr with the alumina or the precursors thereof, forming a green body, drying the green body, and sintering the dried body to produce the porous aluminum oxide structure.

Porous aluminum oxide structures and processes for their production

An economical process for the manufacture of a polycrystalline, sintered, ceramic abrasive from a powder raw material is described, which process is characterized by the following process steps: preparation of a slip largely free from polymerizing and/or coagulating additives from the powder raw material; pressureless shallow casting of the slip in a vessel; degassing, drying and crushing of the cast sheet to obtain a fabricated material and sintering of the fabricated material to create the abrasive. This process can be used to manufacture an abrasive that permits extremely high grinding performance due to its extraordinary density and structural integrity.

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Dresden, Germany

Andreas Krell