Evonik Degussa Gmbh

Degussa Aktiengesellschaft

Monika Oswald

Klaus Deller

Gerrit Schneider

Kai Schumacher

Helmut Mangold

Rolf Clasen

Jürgen Meyer

Markus Hornfeck

Juergen Meyer

Stipan Katusic

Heinz Lach

Martin Moerters

Wolfgang Kollenberg

Roland Weiss

Matthias Rochnia

Horst Miess

Andreas Lauer

Dieter Nikolay

Yi Deng

Georg Fehringer

Corinna Kissner

Martin MÖRTERS

Rolf Prof Clasen

Stable, aqueous dispersion containing silicon dioxide powder having a hydroxyl group density of 2.5 to 4.7 OH/nm, which is obtained from a silicon dioxide powder produced by a flame hydrolysis process under acid conditions. The dispersion is produced by incorporating the silicon dioxide powder into an aqueous solution by means of a dispersing device. The dispersion can be used to produce glass articles.

Silicon dioxide dispersion

Plasma-sprayed layers of aluminium oxide on a substrate are produced by using a pyrogenically produced aluminium oxide, for example selected from the group consisting of borosilicate and steel, as starting powder.

Plasma-sprayed layers of aluminium oxide

Granules based on silicon dioxide and having the properties:  They are prepared by dispersing silicon dioxide in water, spray drying, optionally heating and/or silanizing. Whereas a pyrogenic silicon dioxide powder with a BET surface area of 30 to 90 m/g, a DBP index of 80 or less, a mean aggregate area of less than 25000 nmand a mean aggregate circumference of less than 1000 nm, wherein at least 70% of the aggregates have a circumference of less than 1300 nm or a high-purity pyrogenically prepared silicon dioxide having metal contents of less than 0.2 &#x3bc;g/g is prepared by reacting a silicon tetrachloride having a metal content of less than 30 ppb by means of flame hydrolysis is used.

Granules based on pyrogenically prepared silicon dioxide, method for their preparation and use thereof

Mixed oxide powder consisting of particles with the components zirconium dioxide, aluminium oxide and at least a third component selected from the group including yttrium oxide, magnesium oxide or calcium oxide, wherein mixed oxide powder has an aluminium oxide content 0.01 to 10 wt. % and is homogeneously distributed in the mixed oxide particles, the content of aluminium oxide, zirconium dioxide and yttrium oxide is at least 99.5 wt. %, based on the total quantity of the powder, and the BET surface area is 20 to 80 m2/g. It is obtained by atomising a solution containing at least one starting compound for each of aluminium oxide, zirconium dioxide and the third component, allowing the atomised solution to react with oxygen in a reaction chamber at a reaction temperature 700 to 15000&#xb0; C., cooling the hot gases and the solid products and then separating the solid product from the gases. It can be used as a dental material.

Stabilised aluminium zirconium mixed oxide powder

Pyrogenic silicon dioxide powder with a BET surface area of 30 to 90 m/g, a DBP index of 80 or less, a mean aggregate area of less than 25000 nmand a mean aggregate circumference of less than 1000 nm, wherein at least 70% of the aggregates have a circumference of less than 1300 nm. It is prepared by mixing at least one silicon compound in vapor form, a free-oxygen-containing gas and a combustible gas in a burner of known construction, igniting this gas mixture at the mouth of the burner and burning it in the flame tube of the burner, separating the solid obtained from the gas mixture and optionally purifying, wherein the oxygen content of the free-oxygen-containing gas is adjusted so that the lambda value is greater than or equal to 1, the gamma value is between 1.2 and 1.8, the throughput is between 0.1 and 0.3 kg SiO/mof core gas mixture and the mean normalized rate of flow of gas in the flame tube at the level of the mouth of the burner is at least 5 m/s. The powder can be used as a filler. A dispersion containing the powder according to the invention. The powder can be used as a filler in rubber, silicone rubber and plastics. The dispersion can be used to prepare glass items.

Pyrogenic silicon dioxide and a dispersion thereof

Aqueous dispersion containing a metal oxide powder with a fine fraction and a coarse fraction, in which&#x2014;the metal oxide powder is silicon dioxide, aluminum oxide, titanium dioxide, zirconium dioxide, cerium oxide or a mixed oxide of two or more of the aforementioned metal oxides,&#x2014;the fine fraction is present in aggregated form and has a mean aggregate diameter in the dispersion of less than 200 nm,&#x2014;the coarse fraction consists of particles with a mean diameter of 1 to 20 &#x3bc;m, &#x2014;the ratio of fine fraction to coarse fraction is 2:98 to 30:70, and&#x2014;the content of metal oxide powder is 50 to 85 wt. %, referred to the total amount of the dispersion. The aqueous dispersion is produced by a process comprising the steps:&#x2014;production of a fine fraction dispersion by dispersing the pulverulent fine fraction in water by means of an energy input of at least 200 KJ/m3?, and&#x2014;introducing the coarse fraction in the form of a powder into the fine fraction dispersion under dispersing conditions at a low energy input. Process for the production of molded articles using the dispersion.

Highly-filled, aqueous metal oxide dispersion

Slip containing at least one aluminium oxide powder and at least one unstabilized zirconium dioxide powder, wherein

Slip containing zirconium dioxide and aluminum oxide and shaped body obtainable therefrom

A layer which is obtained by thermal treatment from an aqueous dispersion applied to a substrate, the dispersion containing silicon/titanium mixed oxide powder prepared by flame hydrolysis. It is prepared by applying a dispersion which contains the silicon/titanium mixed oxide powder to a substrate and then sintering by using a thermal treatment. It can be used, for example, on materials with very low coefficients of expansion.

Layer obtained from an aqueous dispersion containing a silicon/titanium mixed oxide powder prepared by flame-hydrolysis

A method for producing ultra-high purity, optical quality, glass articles is disclosed which involves:

Method for producing ultra-high purity, optical quality glass articles

Pyrogenically prepared silicon dioxide with the following physicochemical properties:

Glass prepared from pyrogenically prepared silicon dioxide

Aqueous dispersion comprising silicon/titanium mixed oxide powder with a BET surface area of 5 to 500 m/g which has been prepared by flame hydrolysis and has a titanium dioxide content of 0.5 to 20 wt. %, based on the powder, water and at least one pH-regulating substance which can be removed completely from the reaction mixture on heating, the aqueous dispersion having a solids content of between 40 and 80 wt. %. A green body produced therefrom with a green density of between 40 and 85%. A shaped glass article of optical quality with a coefficient of thermal expansion of not more than 0.5&#xd7;10/K produced from the green body.

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Hanau, Germany

Monika Oswald