Enhancing the tensile properties of SiC composites by a two-dimensional CNT film

Tensile properties of silicon carbide (SiC) ceramics were improved by introducing a two-dimensional carbon nanotube film (CNT_f) with excellent mechanical properties. CNT_f was first assembled by floating catalyst chemical vapor deposition (CCVD); then CNT_f with the pyrolytic carbon interfacial layer (CNT_f/PyC) was prepared by chemical vapor infiltration (CVI). Afterwards, SiC was infiltrated into the CNT_f and CNT_f/PyC preforms by the CVI process, to prevent the uneven dispersion and agglomeration of CNT and damage caused by high temperature sintering. Two composites (CNT_f/SiC, CNT_f/PyC/SiC) were ultimately prepared, and their microstructures and tensile properties were studied. The results show that the tensile strengths of CNT_f/PyC, CNT_f/SiC and CNT_f/PyC/SiC are 716 ± 60, 153 ± 11, and 155 ± 12 MPa, respectively, which illustrates that SiC ceramic reinforced by CNT_f exhibits excellent tensile properties. Besides, the porosities of CNT_f/SiC and CNT_f/PyC/SiC are 17.4% and 22.6%, respectively. CNT_f/PyC/SiC shows higher porosity but better tensile properties, indicating that the PyC interfacial layer enhances the tensile properties of CNT_f/SiC composite. In addition, the strengthening and toughening mechanisms are also discussed.