Processing and characterization of textured mullite ceramics from phyllosilicates
Résumé
Ceramics are obtained from a kaolinite aqueous suspension and are shaped by centrifugation. It favors preferred orientations of particles in the powder compact. Sintered samples at 1410 ◦C were analyzed by QTA and SEM to determine mullite orientation and the important role of process parameters in the organization degree is evidenced. The c-axes of mullite are mainly aligned parallel, but randomly in the sample plane to form a planar texture. A second texture component is seen with b-axes oriented parallel to the centrifugation direction. Mechanical properties are closely related to the organization degree of mullite crystals that is consistent with the development of an interconnected mullite network within the microstructure. At the microscopic scale, Young's modulus values determined by nano-indentation and by ultrasonic immersion techniques in directions parallel and perpendicular to layers evidence an anisotropic behavior of samples. The specific and important role of residual porosity is also shown with the comparison of mechanical behavior of different centrifuged samples.