Abstract: To provide a material for use at high temperatures of several 100° C. which is simple and quick to produce, the invention provides a composite having a layer structure and a process for producing it, which comprises the following steps: a) provision of at least two plates which each have at least one main area of extension, b) stacking of the plates in such a way that a main area of extension of one plate is essentially opposite a main area of extension of the subsequent plate in the stack, c) joining of the stacked plates to form a block using a sinterable composition, d) carrying out a heat treatment on the block so that at least sintering of the sinterable composition occurs and a strong composite body is formed from the block.

Abstract: A process is disclosed for simple and rapid production of a shaped body comprising fused silica and a shaped body which leads to virtually no contamination of a melt in contact with the shaped body even at high temperatures. The disclosed process comprises the steps of: a) provision of fused silica in the form of essentially amorphous SiO2 grains of which not more than 5% have a diameter greater than 15 mm, b) addition of water to the fused silica grains to produce a slip, c) casting of the slip into a mold which comprises a hollow body having the inverse shape of the shaped body to be produced, and d) drying of the slip to give an intermediate body, which is then sintered and cooled. A shaped body producible in accordance with the aforementioned process is also disclosed, which comprises at least 99.0 mol % of SiO2.

Abstract: The method provides an improved quartz glass body, especially an improved quartz glass crucible for melting non-metals, non-ferrous metals, or silicon. The quartz glass body is made by a method in which a quartz glass-water mixture is supplied to a gypsum casting mold comprising an outer part and an inner part, dried in the gypsum mold, and put under an overpressure via a system of ducts in the form of textile tubes embedded in the mold during the drying. Later a resulting green glass body is removed from the mold. At least a portion of the shaping surfaces of the inner part of the gypsum mold are surfaces of a water-impermeable substance. The method provides a cast body with a reduced tendency to crack and with a smaller open porosity.

Abstract: For simple and rapid production of a shaped body comprising fused silica and a shaped body which leads to virtually no contamination of a melt in contact with the shaped body even at high temperatures, the invention provides a process comprising the steps: a) provision of fused silica in the form of essentially amorphous SiO2 grains of which not more than 5% have a diameter greater than 15 mm, b) addition of water to the fused silica grains to produce a slip, c) casting of the slip into a mould which comprises a hollow body having the inverse shape of the shaped body to be produced, d) drying of the slip to give an intermediate body, e) sintering of the intermediate body at a sintering temperature at which at least part of the fused silica is transformed from the amorphous modification into a crystalline modification, f) cooling of the sintered shaped body to a temperature below 300° C., so that a microstructure containing crystalline SiO2 is formed, and also a shaped body which comprises at least 99.

Abstract: To provide a material for use at high temperatures of several 100° C. which is simple and quick to produce, the invention provides a composite having a layer structure and a process for producing it, which comprises the following steps: a) provision of at least two plates which each have at least one main area of extension, b) stacking of the plates in such a way that a main area of extension of one plate is essentially opposite a main area of extension of the subsequent plate in the stack, c) joining of the stacked plates to form a block using a sinterable composition, d) carrying out a heat treatment on the block so that at least sintering of the sinterable composition occurs and a strong composite body is formed from the block.

Abstract: The invention includes an improved quartz glass body, especially an improved quartz glass crucible for melting non-metals, non-ferrous metals, or silicon, and a method and casting mold for making it The quartz glass body is made by a method in which a quartz glass-water mixture is supplied to a casting mold comprising an outer part and an inner part, dried in the mold, and put under an overpressure during the drying. Later a resulting green glass body is removed from the mold. At least a portion of the shaping surfaces of the inner part of the mold are surfaces of a water-impermeable substance. The method provides a cast body with a reduced tendency to crack and with a smaller open porosity.