X-ray diffraction, transmission electron microscopy, X-ray absorption spectroscopy, and magnetic measurements were used to investigate highly porous silica aerogels containing iron and cobalt or iron and nickel, calcined at 450 °C, which are intermediates in the formation of CoFe2O4-SiO2 and NiFe2O4-SiO2 aerogel nanocomposites. Aerogels without iron and pure Co and Ni silicate hydroxides w…