Direct formation of Mg-Al-layered double-hydroxide films on glass substrate by the sol-gel method with hot water treatment

Amorphous Al2O3-MgO thin films with an Mg/Al ratio of unity were prepared on glass substrates by the sol-gel method with a heat treatment at 300 degrees C for 30 min. By immersing the films in water containing sodium hydroxide (pH 10-13) at 100 degrees C, nano-crystals of Mg-Al-layered double hydroxide (LDH) with a hexagonal structure, which is called hydrotalcite and the most basic composition of LDH, were precipitated on the amorphous Al2O3-MgO films. The maximum amount of Mg-Al nanocrystals was obtained when the film was immersed in basic solution of pH 12.