The Role of Acetic Acid and Glycerol in the Synthesis of Amorphous MgO Aerogels

Although sol-gel-derived magnesium-oxide (MgO) aerogels have a wide variety of applications, mostly thin films and powders of brucite, i.e. Mg(OH)(2) aerogels, have been reported. Typically, the brucite structure is converted to the periclase form of MgO upon heat-treatment. We report the role of acetic acid (HAc) and glycerol in the synthesis of amorphous MgO aerogel monoliths through the alkoxide sol-gel method. The two ligands work in concert to retard the nucleophilic substitution with water and decrease the rate of gelation, allowing for Mg-O bond formation while reducing the number of hydroxyl bonds. The amorphous material crystallizes to the periclase (MgO) phase at 400 degrees C without going through the brucite transition, resulting in a novel amorphous MgO aerogel. Specifically, we discuss the modi. cation of the Pechini process to an Mg-alkoxide sol-gel process. The roles of the ligands are investigated in the MgO gelation process through Fourier transform infrared spectroscopy, X-ray diffractometry, and thermogravimetric analysis/DSC. The physical properties of the aerogels are also reported.