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

- Nanorod-like MgAl2O4 spinel aerogel is firstly synthesized.
- This approach is straightforward, inexpensive, and safe.
- The formation temperature of spinel aerogel is as low as 500 °C.
- The BET area of the spinel aerogel is 81.87 m2/g after calcining at 1200 °C.

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 150-200 nm and width of 5-10 nm is well crystallized after 800 °C. The nanocrystal maintains a large specific surface of 81.87 m2/g after calcining at 1200 °C.