In the Romanian natural reservation “Portile de Fier”, by the Danube, there are various dumps, which contain mostly serpentinite (magnesium silicate). The dump serpentinite has few utilisations. A solution for the valorisation of this ore could be the transformation in porous silica, which can serve as raw material for the production of hybrid polymeric inorganic-organic composites. The work presents, first, an advanced structural analyse of the silica, obtained by the attack of the serpenitinite with inorganic acids. At the beginning of the study, differential thermal analyse (DTA) and combined thermogravimetry (TG/DTG) of the silica in the range 20-1000 oC was performed. The first method showed an endothermic effect at about 58 oC, which was confirmed also by the second method, which revealed a weight loss at the same temperature (58 oC). This asserts the elimination at this temperature of volatile substances, especially water. The abatement of the water boiling temperature is a first evidence for the existence of pores in silica. The BET method assessed a considerable specific surface, ranging between 200-270 m2/g. The silica structure was additionally examined by X rays diffraction (XRD), finding its preponderantly amorphous character. The porous silica was used as matrix for the radical polymerisation of acrylonitrile, initiated with azoisobutirodinitrile (AIBN). A study, concerning the influence of the kind of inorganic acid used in the attack of the serpentinite on the polymer hybrid inorganic-organic nano composite characteristics, was achieved. FTIR and DSC evidenced the formation of hybrid composites. The optic microscopy attested finally the pores extinguishment by filling with polyacrylonitrile. Also a study concerning the influence of the reaction time on the proprieties of the polyacrylonitrile was performed. The polymer composites went trough a cyclisation process, heating at 250-300 oC, and then went trough a graphitisation process at temperature about 500 oC. Hereby, an intimate mixture between the silica and carbon was obtained, which was used for the silicon nitride generation. For that, the graphitized composite was heated in nitrogen atmosphere to temperatures between 1400 and 1500 oC. The silicon nitride is a ceramic material well known for its very high physico- mechanical, electrical and thermal characteristics that render it useful in different applications.
