Preparation of C/C-SiC Composites from All-Cellulose Precursors

All-cellulose composites (ACCs) are manufactured from high-performance cellulose fibers and a cellulose-containing ionic liquid (IL) as matrix-forming dope via wet-winding processes, using different concentrations of cellulose in the IL. ACCs are carbonized at 1650 degrees C and then infiltrated with liquid silicon. Application of a carbonization aid (ammonium dihydrogenphosphate, ADHP) substantially improves the carbon yield after carbonization but also results in the depletion of the mechanical properties of the final carbon/carbon silicon carbide (C/C-SiC) material. The microstructure of the porous carbon/carbon preforms strongly depends on both the concentration of cellulose in the IL and the concentration of ADHP. A C/C-SiC composite manufactured from 6 wt% cellulose in the matrix-forming dope, in the absence of ADHP, has a maximum flexural strength of 60MPa. New C/C-SiC composites with different shapes including Z-profiles and tubes are successfully manufactured from pre-shaped ACC precursors. These composites keep their shape during carbonization and the final siliconization process step.