Abstract: A method for discharging particulate building material in a 3D printer to be applied more evenly. A building material curtain of particulate building material and/or an accumulation of building material is optically monitored in a work step of discharging the particulate building material in an area of the building material curtain between the applicator and the construction site and/or a point of impact of the particulate building material on the construction site at which the building material accumulation is created. An image is generated and/or at least one dimension is determined to be compared with an associated reference image and/or a specified reference value. If any deviation is detected, at least one discharge parameter for the discharge of the particulate construction materials is changed.

Abstract: Component bodies of silicon carbide base material, at least in their surface layers, are welded together without the provision of a binder at finely polished joining surfaces by virtue of the fact that at least one of the joint surfaces is of a silicon carbide material containing an excess of silicon (SiSiC). The component bodies are kept closely fitted together especially by an additional pressing force of at least 0.1 kg/cm.sup.2 during a heating stage at atmospheric or lower pressure at a temperature in the range from 1500.degree. C. to 1800.degree. C. for 15 to 100 minutes in an inert atmosphere, the excess of silicon at the boundary making it possible for silicon carbide crystal growth to take place across the boundary.