Papers by Author: Aleš Dakskobler

Abstract: A design study for ceramic pistons was undertaken in order to address the overheating problems associated with the caliper during aggressive braking using modern C/C-SiC brake discs. The reasoning behind the piston design and the choice of the shaping technology are explained. Zirconia-toughened mullite (ZTM) ceramic was chosen for the pistons, because this material exhibits a low thermal conductivity, sufficiently high mechanical strength and fracture toughness, as well as very good thermal-shock resistance. The manufacturing technology of experimental ceramic brake pistons involved compounding of the selected starting powders to form a high-solids-loadingcontaining feedstock, tooling, shaping of green parts by low-pressure injection molding, extraction of the organic binder, pressure-less sintering in air and final machining. Prototypes brake pistons were fabricated and successfully tested as components of motorcycle brake systems in a test laboratory and on a motorcycle racing track.

Abstract: The repeated-deformation processing technique was used in the preparation of layered tricalcium phosphate (TCP)/yttria partially stabilized tetragonal zirconia (Y-TZP) composites with ribbon-like microstructures. The fabrication technique involved repeated plastic deformation of layered green tapes, which are stacked together to form starting bi-material laminates, burn-out of the organic vehicle, and sintering at 1300°C. At this rather low sintering temperature, which was chosen to prevent the extensive diffusion of the calcium into the Y-TZP, the zirconia layers could not be fully densified. In spite of the relatively low fractional density (about 75% TD) of these layers, flexural strength values exceeding 100 MPa were achieved with these composites, 150% higher than the matrix material. During autoclaving in water at 200oC for 24 hours no t-m transformation of the zirconia phase took place, indicating full stability of the porous zirconia layers in these composites under the hydrothermal conditions used in this study.