SYNTHESIS OF LOW-DENSITY AND HIGH HARDNESS CARBON SPHERES CONTAINING NITROGEN AND OXYGEN

The synthesis of new carbon compounds is of considerable interest in m odern materials science. The recent report by Niu et al. [1] of the ex perimental realization of the beta-C3N4 covalent solid predicted theor etically by Liu and Cohen [2] has opened up the possibility of produci ng a new family of materials with a hardness close to that of a diamon d. In the present work we report the growth for the first time of a ne w all covalent material with contains C, N and O. The material was pro duced by thermal decomposition of an hydrocarbon at high temperatures. Most of the solid has the chemical composition; CxNyOz with x similar or equal to 4, y similar or equal to 1 and z similar or equal to 0.02 5 and is made of filaments forming a web. The material has a density o f 1.59 g cm(-3) which corresponds to that of the low density graphites and hardness of 1929 kg mm(-2) (Vickers). This last value is larger t han that corresponding to the hardest known steels. High resolution el ectron microscopy, electron diffraction and X-ray diffraction indicate that the crystalline nature of the C4NO0.025 corresponds with a cubic lattice with a = 7.38 Angstrom. The results of this work show the pos sibility of producing light materials with a very large hardness which might yield useful applications.