Ta-Ni- and Ti-Al-braze-alloys for high temperature stable ceramic - ceramic junctions

Scientific talk introducing to the CNR-ICMATE staff the Fraunhofer IKTS current fields of research as well as latest results of my PhD topic Ni-Ta brazes. Homogeneous samples of Ni-Ta alloys are prepared via arc-melting. The samples phase composition are characterized by XRD, SEM/EDX. High temperature stable phases of Ni-Ta system are identified. Further characterization of the Ta-Ni alloys provides material parameters like coefficient of thermal expansion, hardness and electrical conductivity. The knowledge of these material parameters is crucial to design optimized braze alloys. Adapting the coefficient of thermal expansion for the braze alloys will reduce the mechanical stress in the joint ceramics after brazing and during temperature cycling in application. This knowledge can be the key to increased bending strength and cycle lifetime. Furthermore sufficient electrical and thermal conductivity are necessary to design joints for applications as ceramic heat exchangers and ceramic heating conductors. The third part shows the motivation and first results of the KMM-VIN Titanium-Aluminium project.