Low-temperature Magnesiothermic Synthesis of Mesoporous Silicon Carbide from an MCM-48/Polyacrylamide Nanocomposite Precursor

Mesoporous silicon carbide with high specific surface area was successfully synthesized from an MCM-48/ polyacrylamide nanocomposite precursor in the temperature range of 550-600 ℃ （below the melting point of Mg） by means of a magnesiothermic reduction process. The MCM-48/polyacrylamide precursor nanocomposite was prepared by in-situ polymerization of acrylamide monomer in the presence of mesoporous MCM-48 synthesized by sol-gel method. The physicochemical properties and microstructures of the nanocomposite precursor and the low-temperature SiC product were characterized by X-ray diffraction （XRD）, differential scanning calorimetry-thermo gravimetric analysis （DSC-TGA）, transmission electron microscopy （TEM） and N2 adsorption-desorption. TEM micrographs and Brunauer-Emmett-Teller （BET） gas adsorption studies showed that the SiC powder was nanocrystalline and had a specific surface area of 330 m2/g and a mesoporosity in the range of 2-10 nm. The presence of an exothermic peak in the DSC trace corresponds to the self-combustion process of the SiC magnesiothermic synthesis. The results also show that the carbon in excess to that required to produce SiC plays a role in the reduction of the SiO2. The mechanism of magnesiothermic synthesis of mesoporous SiC is discussed.