Processing, microstructure and mechanical properties of HfB2-ZrB2-SiC composites: Effect of B4C and carbon nanotube reinforcements

Review: Effect on physical, mechanical, and wear performance of ZrB2‐based composites processed with or without additives

“…Fully dense HfB 2 –ZrB 2 –SiC composites were processed with addition of B 4 C and CNT via spark plasma sintering at 1850°C. Though the mechanical properties were enhanced with CNT by suppressing crack formation as discussed in later section, also the augmentation in the mechanical properties established the synergy between solid solution formation (with the equimolar composition of HfB 2 /ZrB 2 ) and reinforcements led to improvement in properties of the composites 74,66,75,60 . It was reported that HfB 2 ‐ZrB 2 system led to full densification and increase in fracture toughness (5.2 to 10.2 MPa.m 1/2 ).…”

“…Optimal percentage of 2.5 wt% carbon fiber and 10 wt% SiC nanoparticles resulted in increase in hardness and fracture toughness from 2100°C to 2150°C. Nisar et al 66 processed densified ZrB 2 –B 4 C and ZrB 2 –SiC–B 4 C composites sintered via SPS at 1850°C for 10 minutes at 30 MPa and found increase in toughness (8.9 to 11.3 MPa.m 1/2 ) of the composite due to toughening effect of B 4 C and SiC.…”

“…Similar result was reported by Yadhukulakrishnan et al 58 Density > 99% was achieved with addition of 4%‐6% CNT addition and indentation fracture toughness was improved due to toughening mechanism. Addition of B 4 C and CNT in HfB 2 –ZrB 2 –SiC composites has not only beneficial for densification, but also increased the indentation fracture toughness three times (13.8 MPa.m 1/2 ) than of monolithic HfB 2 /ZrB 2 (3‐4 MPa.m 1/2 ) suppressing crack formation by deflecting and bridging them 66 . Similar conclusions were drawn by Nisar et al 75 in their work where addition of CNT to ZrB 2 –SiC composite resulted in dense, crack free microstructure.…”

“…CNT embedded in the matrix retaining its structure during sintering at 1850°C. Addition of SiC/CNT/B 4 C in ZrB 2 help in removal of surface oxide from the ceramic during sintering, which inhibited the sintering process 66,75 . Nisar et al 60 in their work enhanced the structural stability and oxidation resistance at extreme thermal temperatures (>2400°C) by reinforcing ZrB 2 with SiC and CNT.…”

Processing of fiber‐reinforced ultra‐high temperature ceramic composites: A review

“…50 Other exploratory reinforcing phases include SiC nanotubes 51 , SiC nanowires grown in situ 52 , carbon black 53 , and carbon nanotubes (CNTs). [54][55][56] CNTs have shown promise by providing fracture toughness as high as 13.8 MPa m 1/2 when used as a reinforcing agent along with SiC and B 4 C in a ZrB 2 -HfB 2 matrix, though providing only a 7% increase from the matrix material (12.9 MPa m 1/2 ). 56 While some CNTs experience partial graphitization, most remain intact even after SPS processing and offer beneficial interfacial compressive residual stresses in the material.…”