Porous co-continuous mullite structures obtained from sintered aluminum hydroxide and synthetic amorphous silica

Porous materials produced from sintered Al(OH)3 show a potentially useful α-Al2O3-based coral-like co-continuous microstructure of high porosity (above 70%) and chemical resistance. However, due to the lack of efficient connections among the particles of the solid phase, their poor mechanical properties limit their use in biomechanical and thermo-mechanical applications, as scaffolds for bone tissue and hot air filters, respectively. In this study, authors improved these connections reinforcing the structure with a sintering aid (synthetic amorphous silica, SAS). Al(OH)3 particles (previously sintered at 1500 °C, 5 h) were imbibed with SAS particles, compacted and sintered at 1300 °C, which generated a coral-like mullite-based porous structure. The porosity levels of the material (47%) were similar to those of the initial green state (50%) and achieved high levels of mechanical properties (flexural strength of 50.29 MPa, elastic modulus of 26.00 GPa), with small linear thermal shrinkage (lower than 6% at 1500 °C).