Facile preparation of monolithic magnesium titanates with hierarchical porosity

In this study, we for the first time came up with a facile approach to fabricate hierarchically porous nano-crystalline monolithic magnesium titanates (MgTi₂O₅/MgTiO₃) by impregnating magnesium chloride into hierarchically porous TiO₂ monolith in a solution containing urea followed by appropriate heat-treatment. The formation of porous MgTi₂O₅/MgTiO₃ monolithic materials took place by the solid-state reaction between original TiO₂ networks and precipitated MgCO₃. The MgCO₃ is precipitated within the TiO₂ wet gel by the reaction between impregnated Mg²⁺ and CO₂, which is produced by hydrolysis and decarbonation of chelating agent in the TiO₂ wet gels and by the hydrolysis of urea at 60°C. The resultant porous magnesium titanates retained narrow macropore size distribution centered at the diameter ̃1 μm. These porous monoliths produced by impregnation, a facile and the low-cost method, are expected to open various engineering applications owing to the low thermal expansion coefficients and high chemical and physical stabilities.