Iron-silica and nickel-silica nanocomposites prepared by high energy ball milling

Metal-silica nanocomposites with different metal volume fractions have been prepared via solid state exchange reactions induced by ball milling followed by a reduction treatment in H2 flux. In nickel-containing mixtures oxygen transfers directly from NiO to Si while NiO is reduced to Ni. When NiO is present in a large ratio, its excess can be reduced by a thermal treatment in H2 flux. Nickel crystallites are obtained with nanometer size in the milling process and there is no significant growth during thermal treatment. Similar process conditions applied to Fe-containing mixtures give rise to a more complex reaction path which prevents the complete conversion of Fe(III) to Fe. Nickel-silica and iron-silica nanocomposites are also produced by ball milling mixtures of either nickel or iron with amorphous silica.