The high pressure synthesis of the graphitic form of C3N4

Basing on "ab-initio" calculations, C3N4 was claimed to be an ultra-hard ma terial with a bulk-modulus close to that of diamond. Five different structu ral varieties were announced: the graphitic form, the zinc blende structure , the alpha and beta forms of Si3N4 and another form, isostructural with th e high pressure variety of Zn2SiO4. Using the same strategy as that developed for diamond or c-BN synthesis. it appears that the graphitic form could be an appropriate precursor for prep aring the 3D varieties. Two main problems characterize the C3N4 synthesis: (-) the temperature should be reduced in order to prevent nitrogen loss, (-) the reactivity of the precursors should be improved. Consequently, we have developed a new process using the solvothermal decomp osition of organic precursors containing carbon and nitrogen in the presenc e of a nitriding solvent. The resulting material, with a composition close to C3N4, has been characterized by different physicochemical techniques.