Preceramic polymers for CMC joints: Filler Dispersion Optimization

Ceramic matrix composites are a class of advanced materials with significant potential for various industrial and energy applications. As these sectors push for greater efficiency, leading to higher operational temperatures and, consequently, a need for materials capable of withstanding such extreme conditions. The exceptional properties of CMCs make them ideal for use in such environments where other materials cannot perform reliably. This thesis investigates a strategy for the realization of joints between advanced oxide matrix composites (CMCs) by using a commercial vinyl functionalized polysilazane, Durazane 1800, categorized as a precursor for polymer-derived ceramics (PDCs). The CMCs involved in the study were supplied by the University of Bayreuth, Germany, and consisted in Nextel 610 alumina fibers within an alumina-zirconia matrix. Introducing fillers into the resin is crucial to enhance the strength of the final joint. The goal of this thesis is to create reliable, high-temperature-resistant joints by optimizing the filler dispersion and quantity in the preceramic polymer. The microstructural characterization of the joints, carried out by scanning electron microscopy (SEM), allows the evaluation of the adhesion between the components and the cohesion of the joint material. Two of the fillers' percentages (70wt.% and 80wt.%) showed the best results in term of morphology and mechanical strength of joints. Mechanical tests in a single lap offset configuration were conducted to determine the strength of these joints. A maximum lap-shear strength of about 10 MPa at room temperature was achieved in the 70wt.% filler doped joined samples.