Preparation of nanocomposite materials containing WS2, delta-WN, Fe3O4, or Fe9S10 in a silica aerogel host

Nanocomposite materials based on silica aerogel hosts have been produced using chemical vapour infiltration/decomposition methods and characterized by X-ray diffraction and electron microscopy. Amorphous tungsten in SiO2 aerogel was formed by the decomposition of W(CO)(6) at 250 degrees C. Alternatively, reaction of this material with sulphur at 700 degrees C produced needle-shaped WS2 crystals with lengths ranging from 25-230 nm. Reaction of the W/SiO2 composite with anhydrous NH3 formed crystals of delta-WN with diameters of 1-5 nm. Fe(CO)(5) is readily absorbed into the silica aerogel, forming an amorphous iron oxide/SiO2 composite after slow oxidation in air. Treatment of this material with additional Fe(CO)(5) produced an Fe3O4/SiO2 aerogel composite. Fe3O4 particle sizes were 20-55 nm. After additional heat treatment, this composite exhibited soft ferromagnetic behaviour with a coercivity of similar to 170 Oe. Fe9S10 crystals with diameters of 30-90 nm were formed by the reaction of the amorphous iron oxide/SiO2 composite with H2S at 900 degrees C.