Abstract: 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.

Abstract: 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.

Abstract: A process for manufacture of a component made of opaque synthetic quartz glass, and a quartz glass tube manufactured according to said process. The process comprises (i) providing a starting material in the form of granulated material of highly pure, synthetic SiO2 comprising at least partially porous agglomerates of SiO2 primary particles, the granulated material having a compacted bulk density of no less than 0.8 g/cm3, (ii) filling the granulated material into a mold and converting it to an opaque quartz glass preform through a process of melting, and (iii) reshaping the preform in a heat reshaping process to obtain a component made of opaque quartz glass. A quartz glass tube is made of quartz glass consisting of a granulated material of synthetic SiO2 with a lithium content of no more than 100 wt-ppb, and the wall thickness of said component being in the range of 0.5 mm to 15 mm.

Abstract: Composite material with high resistance to temperature changes and a high density, and having an SiO2-containing matrix with quartz glass grains embedded therein is produced by preparing a suspension from a particle mixture of finely divided SiO2 powder having at least two different particle fractions and of the quartz glass grains, forming a green compact and sintering the compact. The matrix has an SiO2 content of at least 99% by wt. and is formed from at least first and second particle fractions, each of which is present as granules of nanoscale, amorphous, synthetically produced SiO2 primary particles having a mean primary particle size of less than 100 nm. The composite material has an SiO2-containing matrix with an SiO2 content of at least 99% by wt. It is particularly suited for applications such as starting material for producing a permanent mold for melting solar silicon.

Abstract: Known is a method of producing a composite material having an SiO2-containing matrix in which quartz glass grains are embedded, wherein a suspension is prepared from a particle mixture of finely divided SiO2 powder having at least two different particle fractions and of the quartz glass grains, a green compact is formed therefrom and said compact is sintered. To permit an inexpensive production of a composite material having a high resistance to temperature changes together with a high density, it is suggested according to the invention that the matrix should have an SiO2 content of at least 99% by wt. and should be formed from at least a first (33) and a second (35) particle fraction, each of the particle fractions being present as granules of nanoscale, amorphous, synthetically produced SiO2 primary particles (2) having a mean primary particle size of less than 100 nm.

Abstract: 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.

Abstract: 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.

Abstract: A process for manufacture of a component made of opaque synthetic quartz glass, and a quartz glass tube manufactured according to said process. The process comprises (i) providing a starting material in the form of granulated material of highly pure, synthetic SiO2 comprising at least partially porous agglomerates of SiO2 primary particles, the granulated material having a compacted bulk density of no less than 0.8 g/cm3, (ii) filling the granulated material into a mold and converting it to an opaque quartz glass preform through a process of melting, and (iii) reshaping the preform in a heat reshaping process to obtain a component made of opaque quartz glass. A quartz glass tube is made of quartz glass consisting of a granulated material of synthetic SiO2 with a lithium content of no more than 100 wt-ppb, and the wall thickness of said component being in the range of 0.5 mm to 15 mm.

Abstract: In a known process for the production of opaque quartz glass a blank is formed from synthetic SiO2 granulate and is heated at a vitrification temperature to form a body of opaque quartz glass. In order to provide on this basis a process for the production of pure opaque quartz glass with a homogenous pore distribution, high density, high viscosity and a low tendency to devitrify, it is proposed according to the invention that the SiO2 granulate to be used is a SiO2 granulate (21; 31) composed of at least partially porous agglomerates of SiO2 primary particles, with a specific BET surface ranging from 1.5 m2/g to 40 m2/g and an apparent density of at least 0.8 g/cm3. A SiO2 granulate (21; 31) suitable for the implementation of the process is distinguished in that it is formed from at least partially porous agglomerates of SiO2 primary particles and in that it has a specific BET surface ranging from 1.5 m2/g to 40 m2/g and an apparent density of at least 0.6 g/cm3.