Heraeus Quarzglas Gmbh & Co Kg

Siltronic Ag

Martin Arndt

Walter Lehmann

Udo Gertig

Hilmar Laudahn

Gabriele Korus

Heinz Fabian

Michael Hünermann

Thomas Kayser

Matthias Otter

Boris Gromann

Nigel Robert Whippey

Wolfgang Englisch

Johann Leist

Achim Hofmann

Nils Christian Nielsen

Abdoul-Gafar Kpebane

Manfred Schwarzbauer

The invention relates to a process for the preparation of a quartz glass grain comprising the process steps i.) Providing a silicon dioxide granulate from a pyrogenically produced silicon dioxide powder, ii.) Making a glass melt out of silicon dioxide granulate, iii.) Making a quartz glass body out of at least part of the glass melt and iv.) Reducing the size of the quartz glass body to obtain the quartz glass grain. The invention further relates to a quartz glass grain which is obtainable by this process. The invention further relates to opaque quartz glass bodies, which are obtainable by further processing of the quartz glass grain.

Preparation of a synthetic quartz glass grain

The production of a quartz glass grit comprises the granulation of pyrogenetically produced silicic acid, and the formation of a SiOgranulate and the vitrification of the SiOgranulate using a treatment gas, which contains at least 30% by volume of helium and/or hydrogen. Said process is time consuming and cost intensive. In order to provide a method which makes it possible, starting from a porous SiOgranulate, to manufacture, in a cost effective manner, a dense, synthetic quartz glass grit, which is suitable for melting bubble-free components made of quartz glass, according to the invention the vitrification of the SiOgranulate occurs in a rotary kiln having a mullite-containing ceramic rotary kiln, for the manufacture of which a starting powder, which contains a molar proportion of at least 45% SiOand AlOis applied by means of a thermal powder spraying method, forming a mullite-containing layer on a mold core, and the mold core is subsequently removed, and wherein the ceramic rotary kiln is flooded with a treatment gas or rinsed with a treatment gas, and wherein the ceramic rotary kiln is flooded with a treatment gas or rinsed with a treatment gas, which contains at least 30% by volume of helium and/or hydrogen.

Method for producing synthetic quartz glass granules

A known quartz glass crucible for crystal pulling consists of a crucible wall, having an outer layer which is provided in an external area thereof with a crystallisation promoter which results in crystallisation of quartz glass, forming cristobalite when the quartz glass crucible is heated according to specified use in crystal pulling. The aim of the invention is to provide a quartz glass crucible which has a long service life. As a result, the crystallisation promoter contains, in addition to a silicon, a first component which acts as a reticulating agent in quartz glass and a second component which is free of alkali metals and which acts as an agent forming separating points in quartz glass. The above mentioned components are contained and incorporated into a doping area () of the outer layer () having a layer thickness of more than 0.2 mm.

Quartz glass crucible and method for the production thereof

Known is a method of producing a quartz glass crucible in which a crucible base body is provided at least in part with an inner layer in which the formation of cristobalite is induced by using a crystallization promoter. On the basis thereof, in order to provide an inexpensive method of producing a quartz glass crucible with reproducible characteristics for long service lives, it is suggested according to the invention that the crystallization promoter and a reducing substance are introduced into the inner layer.

Method of producing a quartz glass crucible

To facilitate the start of a process using a quartz glass crucible with a crucible body and an inner layer of quartz glass a quartz glass crucible is provided with an inner surface roughened at least in the starting zone region by multiple depressions disposed at a maximum distance of 5 mm from one another. Furthermore, a simple and inexpensive process for the manufacture of such a quartz glass crucible is described, by providing a crucible body with a smooth inner surface of quartz glass and subsequently roughening the inner layer in the starting zone region by multiple depressions disposed at a maximum of 5 mm from one another.

Quartz glass crucible and process for the manufacture of the crucible

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Bitterfeld, Germany

Martin Arndt