The low temperature fabrication of nanocrystalline MgAl2O4 spinel aerogel by a non-alkoxide sol-gel route

Abstract

A novel nanorod-like spinel aerogel is synthesized by the sol-gel method combined with the supercritical technique. The Mg4Al2(OH)14·3H2O and boehmite is formed in the spinel precursor aerogel and Mg4Al2(OH)14·3H2O transforms into MgO and spinel at 350°C. Structural transition of boehmite to γ-Al2O3 occurs at ca. 400°C, which is favorable to the further solid reaction between MgO and γ-Al2O3 forming spinel aerogel at 500°C. This formation temperature is much lower than the conventional methods. The highly pure nanorod spinel with length of 150–200nm and width of 5–10nm is well crystallized after 800°C. The nanocrystal maintains a large specific surface of 81.87m2/g after calcining at 1200°C.