In a known method for producing a quartz glass component, a crystal formation layer containing a crystallization promoter is produced on a coating surface of a base body of quartz glass. Starting therefrom, to provide a method for producing a quartz glass component of improved thermal strength and long-term stability which displays a comparatively small deformation particularly also in the case of rapid heating-up processes, it is suggested according to one aspect that a porous crystal formation layer containing amorphous SiO.sub.2 particles is produced with a mean thickness in the range of 0.1 to 5 mm, and that a substance which contains cesium and/or rubidium is used as the crystallization promoter.

The invention relates to a continuous sol-gel method for producing quartz glass, comprising the following steps: (a) continuously metering a silicon alkoxide into a first reactor (R1) and carrying out an at least partial hydrolysis process by adding an aqueous mineral acid, thereby obtaining a first product flow (A); (b) continuously producing an aqueous silicic acid dispersion by continuously mixing water and silicic acid in a second reactor, thereby obtaining a second product flow (B); (c) continuously mixing the product flows (A) and (B) in a third reactor (R3) in order to produce a pre-sol, thereby obtaining a third product flow (C); (d) continuously adding an aqueous base to the product flow (C), thereby obtaining a sol; (e) continuously filling the exiting sol into moulds, thereby obtaining an aquagel; (f) drying the aquagel, thereby obtaining xerogels; and (g) sintering the xerogels, thereby obtaining quartz glass, with the proviso that at least one of the steps (a) to (e) additionally includes a degassing process of at least one feed material used in the step.

One aspect relates to a process for the preparation of a quartz glass body, including provision of a silicon dioxide granulate, making a glass melt from the silicon dioxide granulate and making a quartz glass body from at least part of the glass melt. The provision includes making a silicon dioxide powder with at least two particles prepared from a silicon-chlorine compound, bringing the silicon dioxide powder into contact with ammonia to obtain a treated silicon dioxide powder, and granulating the treated silicon dioxide powder to obtain a silicon dioxide granulate. The chlorine content of the silicon dioxide powder is greater than the chlorine content of the silicon dioxide granulate. One aspect relates further to a quartz glass body which is obtainable by this process. One aspect also relates to a process for the preparation of a silicon dioxide granulate.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate I prepared from a pyrogenically produced silicon dioxide powder, treating the silicon dioxide granulate I with a reactant at a temperature in a range from 1000 to 1300 C., and making a glass melt out of the silicon dioxide granulate. A quartz glass body is made out of at least a part of the glass melt. Furthermore, one aspect relates to a quartz glass body obtainable by this process. Furthermore, one aspect relates to a light guide, an illuminant, and a formed body, each of which is obtainable by further processing of the quartz glass body. One aspect additionally relates to a process for the preparation of a silicon dioxide granulate II.

One aspect relates to a process for the preparation of a quartz glass grain, including providing a silicon dioxide granulate from a pyrogenically produced silicon dioxide powder, making a glass melt out of silicon dioxide granulate, making a quartz glass body out of at least part of the glass melt and reducing the size of the quartz glass body to obtain the quartz glass grain. One aspect further relates to a quartz glass grain which is obtainable by this process. One aspect further relates to opaque quartz glass bodies, which are obtainable by further processing of the quartz glass grain.

A crucible structure is adapted for manufacturing a silicon crystal structure. The crucible structure includes a crucible body and a release coating layer. A material of the crucible body includes silicon dioxide. The release coating layer directly covers the crucible body, and a material of the release coating layer includes barium silicate. The barium silicate is a continuous film to contact the silicon crystal structure, and a thickness of the release coating layer is between 35 m and 350 m.

A low cost method for producing a mechanically and thermally stable composite body containing a first layer of a material with a high silicic acid content and an additional component connected to a second layer of a material with a high silicic acid content and an additional component in a second concentration differing from the first concentration is provided. The method involves (a) preparing a first slurry layer having a free surface using a first shirt mass containing SiO.sub.2 particles and an additional component dispersed in a first dispersing agent, (b) providing a second slurry mass containing SiO.sub.2 particles and an additional component in a second concentration dispersed in a second dispersing agent, (c) forming a composite-body intermediate product by applying the second slurry mass to the free surface of the first slurry layer, and (d) heating the composite-body intermediate product while forming the composite body.

A roofing granule includes a glass substrate and a plurality of pores in the glass substrate such that the roofing granule has a minimum total solar reflectance of at least 50%.

A method for producing a component with portions of a rare earth metal-doped quartz glass, an intermediate product containing voids and consisting of a SiO.sub.2 raw material doped with rare earth metal is introduced into a sinter mold the interior of which is bordered by a carbonaceous mold wall, and is melted therein into the component by gas pressure sintering at a maximum temperature above 1500 C. A shield is arranged between the mold wall and the intermediate product. In order to indicate a modified gas pressure sintering method that ensures the production of rare earth metal-doped quartz glass with reproducible properties, a bulk material of amorphous SiO.sub.2 particles with a layer thickness of at least 2 mm is used as the shield, the softening temperature thereof being at least 20 C. higher than the softening temperature of the doped SiO.sub.2 raw material, and the bulk material being gas-permeable at the beginning of the melting of the intermediate product, and the bulk material sintering during melting into an outer layer that is gas-tight to a pressure gas.

A method for manufacturing a linear member reduces changes in the physical properties of a substance serving as a material for the linear member that may be caused when the substance is formed into a linear shape from powder. A manufacturing device usable for the method for manufacturing a linear member is a device for manufacturing a linear member having a predetermined function. The device includes a compressor. The compressor compresses, from an outer periphery of an elongated hollow body (9), the hollow body (9) accommodating powder of a substance having the predetermined function at an inner periphery of the hollow body (9) to compact the powder to allow the powder to substantially show the predetermined function. The linear member can be freely deformed while linearly accommodating the powder and maintaining the powder compacted. This structure can reduce changes in the physical properties of a substance in the linear member having the predetermined function that may be caused when the substance is formed into a linear shape from the powder.