Background: Silicon Carbide (SiC) ceramics are promising engineering material due to its
phenomenal properties, such as strong corrosion resistance, high-temperature hardness, wear resistance,
high thermal conductivity and high stability in an aggressive environment. The key problem
of SiC is low fracture toughness due to its brittle nature and to circumvent this, herein high ductile
material like MWCNT was used as reinforcement by different proportions.
Methods: Nanocrystalline powdered Silicon Carbide (SiC) of particle size of 40 nm and x % weight
ratio of SiC (x = 95%, 90% and 85%) + y % weight ratio of multiwalled carbon nanotubes
(MWCNTs) of particle size of 20 nm (y= 5%, 10% and 15%) composites were ball milled and fabricated
using spark plasma sintering process with temperature rate of 100°C/min and external pressure
of 50 MPa. The sintered samples were tested according to ASTM standards to verify the mechanical
properties of the samples. Furthermore, lattice strain and crystalline size was determined by XRD
and the crack bridging mechanism was studied by FESEM.
Results: It was observed that the uniform distributions of MWCNTs were achieved through ultrasonication
and ball milling processes, which play a predominant role in increasing fracture toughness.
The fracture toughness of the composite improves drastically from 3.71 MPa m1/2 (100% SiC) to
10.21 MPa m1/2 (85% SiC-15% MWCNT). The theoretical and relative densities of the materials
were gradually reduced due to the increase in MWCNTs which is due to the lower density of the reinforcement
material and an increase in porosity of the samples.
Conclusion: The MWCNTs act as a bridging aid in sintered samples, FESEM image signifies some
pull-outs and crack branching mechanisms of MWCNTs which is the reason for an increase in the
fracture toughness of SiC.