Preparation of YTZP/SiC/SiO2 materials by colloidal processing and SPS

Reference	Presenter	Authors (Institution)	Abstract
13-049	Rodrigo Moreno	Navarro Lopez, L.(Instituto de Tecnología de Materiales, Universitat Politècnica de València); Borrell, A.(Universitat Politècnica de València); Gutiérrez-González, C.F.(Universitat Politècnica de València); Salvador, M.D.(Universitat Politècnica de València); Moreno, R.(Instituto de cerámica y vidrio);	Tetragonal zirconia polycrystals doped with yttria (YTZP) have excellent properties such as high strength and fracture toughness. Better performance can be achieved when combining it with other reinforcing phase, one of the most popular being silicon carbide (SiC) that acts as an effective reinforcing material. In particular, SiC particles play an important role in the zirconia matrix acting as a self-sealing crack agent at high temperature. This is of great importance in the design and fabrication of thermal barrier coatings and structural bulk composites. However, there is a risk of SiC evaporation and hence the presence of a protective material such as SiO2 may be useful. This work deals with the preparation of SiC reinforced zirconia bulk materials with enhanced crack healing properties through aqueous colloidal processing and further spark plasma sintering. Aqueous suspension of submicron sized YTZP/SiC and YTZP/SiC/SiO2 powders were prepared using different contents of SiC and a total solids loading of 30 vol.%. The stability was optimised controlling the zeta potential and the rheological behaviour of the suspensions as a function of deflocculant content and homogenisation time. The optimised suspensions were freeze dried to obtain homogeneous mixtures of the powders with different composition. These powders were successfully sintered by Spark Plasma Sintering (SPS). The resulting bulk materials were characterised in terms of microstructure and mechanical properties like flexural strength, hardness and elastic modulus, which were studied by nanoindentation. Thermal fatigue tests have been carried out at different conditions in order to determine the crack-healing ability of these materials.
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