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- Characterization of a Functionally Gradient Ceramic Based on CaZrO3 – MgOPublication . Babo, Débora Rafaela Telha de; Nunes-Pereira, João; Silva, Pedro D.; Pena, Pilar; Baudin, Carmen; Pereira Silva, AIn the case, where the structure is exposed to severe conditions of operation, such as high strength, wear and high-temperature gradients (e.g. engine components, insulation system, thermal barrier and thermal shield) must be applied. In this work, it was developed and characterized a functional gradient ceramic coating. A ceramic composite based in CaZrO3 – MgO was used in order to design a material with successive layers of molar composition 2:3, 1:1 and 1:3 of CaZrO3:MgO, respectively. A dense material was obtained by sintering assisted reaction (Figure 1). Thermal conductivity at room temperature, hardness, fracture toughness, surface energy, and microstructure were characterized.The results show for monolithic specimens of 2:3 CZ, 1:1 CZ and 1:3 CZ a H of 9,9 GPa, 9,8 GPa and 10,1GPa; a Kc of 1,6 MPa.m1/2, 1,7 MPa.m1/ and 2,1 MPa.m1/2; a k of 0,59 W/mK; 0,76 W/mK and 0,79 W/mK; and a surface energy (SE) of 43,27 mN/m, 51,39 mN/m and 46,55 mN/m, respectively. The functional gradient ceramic shows a H of 10,7 GPa, a Kc of 1,97 MPa.m1/2; a k of 0,82 W/mK and SE of 53,98 mN/m. The individual composition and the functional gradient ceramic show a similar relative density of 4,3 g/cm3 and a porosity of 0,2%. This design methodology has the advantage of allowing the properties of the same material to suit different substrates.
- Design and Thermal Conductivity Characterization of a Functionally Gradient Ceramic Based on CaZrO3 – MgO CompositionPublication . Babo, Débora Rafaela Telha de; Nunes-Pereira, João; Pereira Silva, A; Pena, Pilar; Baudin, CarmenSpace exploration involves the use of state-of-the-art technologies such as satellite production, propulsion systems, avionics, aerodynamics, research and development of materials, etc. In the particular case of human spaceflight, the insulation system of the spacecraft is also required in order to ensure crew safety in re-entry of the atmosphere and, if possible, the spacecraft re-use. In the case, where the structure is exposed to high temperature gradients, among other systems a thermal barrier must be used for the structure in order to protect it from critical damage. Based on this concept, in this work it was developed and characterized a design of a functional gradient ceramic coating. Recently, several studies have proposed the stoichiometric composition of calcium zirconate (CaZrO3) as a viable alternative for harsh environments subjected to high temperatures, corrosion and wear, and the mechanical properties of this compound can be improved through a solid solution ion order to obtain a CaZrO3-MgO multiphase ceramic composites. In this work, a functional gradient material was produced with successive layers with variation in its molar composition (1:3, 1:1 and 2:3 of CaZrO3:MgO) and its thermal conductivity characterized.