Micro-Raman investigations on the formation of in-void graphitic phase during densification of novel amorphous carbon composites for moderator applications

High-density amorphous carbon composites with exceptional material properties and thermal and radiation stability were prepared using a novel processing route and were then subjected to further densification by high pressure impregnation of pores with liquid phenol formaldehyde resin followed by carbonization of the same. It was found that the density of the material improved significantly by this technique. At the same time, the material as a whole was able to retain its isotropicity and amorphous character as is evidenced from the XRD, Raman and polarized microscopic studies on the bulk material. However, an in depth investigation using micro-Raman spectroscopy reveals that a parasitic graphite phase is formed within the pores when impregnated at very high pressures. The study is further supported by careful polarized microscopy of the pores. It is believed that 'stress induced graphitization' during carbonization of the resin has led to the formation of such in-void parasitic phases