Reinforcement of the Ceramic Matrix of CaO-ZrO₂-MgO with Al₂O₃ Coarse Particles

A thermal protection system is subject to high forces, in particular compression, bending and wear, to aggressive environments of high temperatures, high velocity gases and particle shock. Typically, ceramic materials appear as a first barrier or outer shield over a metallic substrate responsible for the structure. When it comes to a coating due to the small thickness, the particles of the raw material are sub-micron scale, but when a shield with a few centimeters is built its structural and economic viability requires the use of wider particle size distributions. In this work, a ceramic fine-grained matrix of CaO-ZrO2-MgO was reinforced with commercial coarse Al2O3 particles. The results show that for larger size distributions, CZM-4A, replacing 63% of fine-grained matrix by coarse Al2O3 particles, the dimensional stability is obtained (Delta L = 5%) and the good mechanical properties such as flexural strength of 154 MPa, elastic modulus of 286 GPa, and hardness of 8.5 GPa, which allows to propose this ceramic composite for a structural application.