Ultrafine-grained graphite prepared from filler of onion-like carbon spheres via a liquid mixing process for using in molten salt reactor

Abstract

Ultrafine-grained graphite (UG) has been prepared via a liquid mixing process using onion-like carbon spheres (OLC) as filler for comparison to a control sample with calcined pitch cokes (PC) as filler. The same coal-tar pitch was used for both. The average particle sizes of both OLC and PC were 7 μm. The graphite derived from filler of OLC exhibited superior properties of higher mechanical strength, more compact structures, higher isotropy and much better barrier property to molten salt than the graphite derived from filler of PC. This suggests that OLC has some advantages over PC as the filler for the preparation of nuclear graphite for using in molten salt reactor. The relevant mechanisms are analyzed and discussed in detail based on the structure and property advantages of OLC over PC such as more compact structure, special concentric lamellar structure and 6 wt% of volatile. Moreover, in terms of UG prepared from filler of OLC, the following issues are required to investigate in the future such as improving its thermal conductivity, reducing its coefficient of thermal expansion and elucidating its irradiation behaviors.