Development of a gastight sealing material for ceramic components

Within the framework of a cooperation project, ceramic components of alumina, Al2O3, were sealed in a gastight manner for chemical applications using a sealing compound based on ceramic raw materials. The sealing is adapted to the Al2O3 ceramic with respect to expansion coefficient and wettability and it is inert, mechanically stable, chemically resistant and above all gastight at application temperatures of approx. 1000 °C. This was achieved with high reproducibility by a composition in the SiO2–Al2O3–CaO–K2O quaternary system. The ceramic sealing compound is selectively crystallized by adequate temperature control and shows then the required high temperature resistance. The strengths achieved are sufficient for the planned application as a sealing material for a ceramic microreactor. The temperature cycling resistance and the thermal shock resistance are also adapted to Al2O3. Additional tests of commercial glass sealants were carried out to evaluate the results obtained.