Converting stöber silica and mediterranean sand to high surface area silicon by a reaction under autogenic pressure at elevated temperatures

We report on a reaction to convert Stöber silica or Mediterranean sand to high surface area silicon (HSAS). The starting silica and/or the sand are reduced by magnesium under the autogenic pressure of the reactants at 750 °C for 5 h. After the MgO is removed, HSAS is formed. The surface areas are 200 and 86 m²/g for the product obtained from the Stöber silica and sand, respectively. The morphology of the final product is almost identical to that of the precursor silica. The products are stable in air because a thin layer of SiO₂ is present on the surface of the silicon. We have detected luminescence from the HSAS in the wavelength region of 626-640 nm.