Response surface optimization of pitch phase change densification using composite phenolic resin co-carbonization to prepare high performance carbon refractories

The response surface method was used to successfully predict the optimal addition amounts of phenolic resin and bitumen binding system for cold isostatic pressing carbon blocks as 14 wt% and 2 wt%, respectively, and ultrahigh performance carbon blocks with a compressive strength of 104.25 MPa and pore sizes below 1 mu m accounted for 90.8 % were predicted and prepared. We proposed the phase change densification theory for pitch successfully explaining the secondary densification of carbon blocks by pitch powder during shaping and curing. Besides, In the carbonization stage with the carbon block firing schedule, we determined that the carbon structure of pitch after carbonization with the participation of the phenolic resin matrix and organic small molecules of phenolic resin volatilization and pyrolysis consisted of lamellar carbon with a greater number of defects, and proposed that the interface between the non-graphitizable carbon after the carbonization of the phenolic resin and graphitizable carbon after the carbonization of pitch is the carbon binding mode and mechanism of the nucleation and growth of domain structures at the defects of lamellar carbon. Therefore, We determined that the mosaic and fine mosaic binding between the high strength and high brittleness nongraphitizable carbon carbonization of phenolic resin and the low strength and high ductility graphitizable carbon carbonization of pitch as well as the aforementioned carbon binding mechanism based on domain structure also were the important reasons for the performance enhancement of pitch composite phenolic resin bonded carbon blocks.