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

Abstract 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 °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 60 MPa. 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.