Using PyC modified 3D carbon fiber to reinforce UHTC under low temperature sintering without pressure

Abstract

Finding the optimum balance between strength and toughness, as well as acquiring reliable thermal shock resistance and oxidation resistance, has always been the most concerned topic in the discussion of ultra-high temperature ceramic composites. Herein, PyC modified 3D carbon fiber is used to reinforce ultra-high temperature ceramic (UHTC). The macroscopic block composite with large size is successfully fabricated through low temperature sintering at 1300 °C without pressure. The prepared PyC modified 3D Cf/ZrC-SiC composites simultaneously possess excellent physical and chemical stability under the synergistic effect of PyC interface layer and low temperature sintering without pressure. The fracture toughness is increased in magnitude to 13.05 ± 1.72 MPa·m1/2 accompanied by reliable flexural strength of 251 ± 27 MPa. After rapid thermal shock spanning from room temperature (RT) to 1200 °C, there are no visible surface penetrating cracks, spalling, or structural fragmentation. The maximum critical temperature difference reaches 875 °C, which is nearly three times higher than that of traditional monolithic ceramics. The haunting puzzle of intrinsic brittleness and low damage tolerance are resolved fundamentally. Under the protection of PyC interface layer, the carbon fibers around oxide layer and matrix remain structure intact after static oxidation at 1500 °C for 30 min. The oxide layer has reliable physical and chemical stability and resists the erosion from fierce oxidizing atmosphere, ensuring the excellent oxidation resistance of the composites. In a sense, the present work provides promising universality in designability and achievement of 3D carbon fiber reinforced ceramic composites.

Improved damage tolerance and oxidation resistance of (Ti 0.2Zr 0.2Hf 0.2Nb 0.2Ta 0.2)B 2–SiC by introducing chopped carbon fibers

“…The fracture toughness for the (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B 2 ceramics could be increased by about 30% after adding 20 vol% SiC particles [17]. Similar improvements in the fracture toughness of (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B 2 -SiC were achieved by Liu et al [16] and Zhang et al [18]. Although SiC can significantly promote the densification and improve the intrinsic strength of HEBs, the flaw tolerance and capacity of energy dissipation of HEBs cannot be effectively improved by the introduction of SiC [19,20].…”

Additive manufacturing of continuous carbon fiber–reinforced silicon carbide ceramic composites

“…Figure 13 shows the schematic diagram of the crack extension of the C f /SiC composite during the three‐point bending test. The bending strength and fracture toughness of C f /SiC composites are mainly improved by the pullout, debonding, and breakage of C f to enable the material to absorb more energy 31,38 . Figure 14 shows the bending strength, porosity, and density of the green bodies with different C f contents.…”

High damage tolerant Al2O3 composite ceramics constructed with short Al2O3 fibers

“…Lots of effort has been made to alleviate the brittle failure of ceramic materials. Such as phase change toughening, [3][4][5] particle dispersion toughening, 6,7 whisker toughening, [8][9][10] long fiber toughening, 11,12 and bionic structure toughening 2,13,14 developed to overcome the sensitivity to defect. Among them, the long fiber toughening and bionic structure composite ceramics achieve the optimal nonbrittle failure manner with high toughness and work of fracture together with considerable strength.…”