Abstract: A process for joining ceramic parts comprises autoclaving a powdered ceramic composition to increase its hydrogen form contents to a concentration that serves to increase the composition's absorption of microwave energy during subsequent heating of the ceramic parts; coating the autoclaved ceramic composition on the surfaces of the parts to be joined together; and placing the coated surfaces of the parts to be joined together and focusing microwave energy at the joint between the parts in order to seal the joint by refiring and rereacting the parts, the microwave energy being of sufficient power and being uniformly applied to the joint for a sufficient period of time to seal the joint.

Abstract: A process for the preparation of ceramic articles having a thickness of at least about 2.5 cm, which comprises:a) selecting the ceramic composition from the group consisting of silicate material, metal oxides, nitrides and carbides, and mixtures thereof, optionally adding ceramic fibers, such as boron nitride or silicon carbide fibers, to the ceramic composition,b) autoclaving the ceramic composition to increase its hydrogen form contents, which increases the composition's microwave absorptivity,c) forming the ceramic composition into the desired shape, andd) subjecting the composition so shaped to microwave energy to internally heat and thereby dry and sinter the composition, optionally with external heat applied by means of electrical resistance or gas fired heating. Novel apparatuses for the extrusion and vibrocompaction of ceramic compositions, the drying of ceramic masses, kilns for microwave-assisted firing of the ceramic articles, cars, and a hydraulic air handling system for tunnel kilns.