Mechanosynthesis of metal-silica nanocomposites

A mechanochemistry route has been experimented to synthesise metal-silica nanocomposites with different volume fractions of nickel or iron through oxygen transfer reactions from the corresponding metal oxides to silicon. In nickel containing samples, oxygen transfer occurs in a direct way and Si can be completely transformed into silica, while the stoichiometric quantity of NiO is reduced to Ni(0) nanometer crystallites. When NiO is present in a larger content, the excess, present at the end of the milling process, is reduced by a thermal treatment in H2 flux. This does not produce a significant growth of the nanocrystallites. Similar process conditions applied to Fe containing samples give rise to a more complex reaction path which prevents the complete conversion of Fe(III) to Fe(0).