Thermal shock behavior of ZrB2–SiC ultra-high temperature ceramics with addition of zirconia

In situ formation of ZrB2–ZrO2 ultra-high-temperature ceramic composites from high-energy ball-milled ZrB2 powders

“…Thus, the combination of the SEM, EDXS, and XRD analyses reveals that The hardness and toughness measured by Vickers testing were 17.6(±0.2) GPa and 3.0(±0.1) MPa m 0.5 for the ZrB 2 -ZrO 2 composite, and 16.2(±0.2) GPa and 1.9(±0.1) MPa m 0.5 for the reference ZrB 2 monolith. The increased toughness of the ZrB 2 -ZrO 2 composite compared to the reference ZrB 2 monolith, which has a grain size more than twice as large, highlights the fundamental role of ZrO 2 in enhancing the ZrB 2 toughness via crack bridging and its transformation toughening in accordance with previous observations [22][23][24]. Furthermore, despite ZrO 2 being softer than ZrB 2 , the ZrB 2 -ZrO 2 composite is harder than the reference ZrB 2 monolith, in part because the former is fully dense whereas the latter is only ∼96% dense (see Figs.…”

“…The incorporation of high aspect ratio reinforcements, such as carbon fibres [10,11] and nanotubes [12], graphite flakes [13][14][15][16], and SiC whiskers [17][18][19][20], fibres [17,18], or platelets [21] further reduces the brittleness of the ZrB 2 -based composites, which is attributed to the combination of debonding, pull-out, and bridging of these reinforcements as well as enhanced crack deflection and crack pinning. Finally, another interesting strategy lies in dispersing within the ZrB 2 matrix a second phase with phase-transformation capability, such as ZrO 2 [22][23][24][25][26]. Thus, it has been demonstrated that the ZrB 2 -ZrO 2 composites exhibit R-curve behaviour while pure ZrB 2 ceramics do not [22][23][24], resulting from crack bridging and the stress-induced martensitic transformation in ZrO 2 .…”

“…Finally, another interesting strategy lies in dispersing within the ZrB 2 matrix a second phase with phase-transformation capability, such as ZrO 2 [22][23][24][25][26]. Thus, it has been demonstrated that the ZrB 2 -ZrO 2 composites exhibit R-curve behaviour while pure ZrB 2 ceramics do not [22][23][24], resulting from crack bridging and the stress-induced martensitic transformation in ZrO 2 . So far, the ZrB 2 -ZrO 2 particulate composites have been fabricated from mixtures of ZrB 2 and ZrO 2 powders (the preparation of which involves comminution, wet homogenization, and slurry drying) that are densified by hot-pressing resulting in a duplex ceramic microstructure.…”

Preparation and characterization of high-performance ZrB2–SiC–Cf composites sintered at 1450 °C

“…Surprisingly, the critical temperature difference of ZSC30 is up to 727 ℃, much higher than the reported values of the ZrB 2 -based UHTCs in previous literatures [47][48][49][50]. In order to further understand the excellent thermal shock resistance of ZrB 2 -SiC-C f composite, the thermal stress damage resistance parameter ( R ) is used to evaluate the thermal shock stress crack propagation of ceramics [51], represented by Eq.…”

Synthesis, microstructure and mechanical properties of (Zr,Ti)B2-(Zr,Ti)N composites prepared by spark plasma sintering

“…About the sintering mechanisms, the additives of B 4 C [6], VC [7], WC [8], ZrN [10,12], and AlN [11] are to remove the surface oxides of ZrB 2 , and the adding of Si 3 N 4 [9] is for forming low melting point ZrSi 2 and B-N-O-Si-Zr glassy phase during sintering. For using ZrN, Monteverde and Bellosi [10] determined that the additive of 4.5 vol.% ZrN contributed to densify ZrB 2 -SiC composites after hot pressing at 1900 • C. Additionally, for enhancing the mechanical properties of ZrB 2 , especially about fracture toughness and thermal shock resistance, SiC particle, SiC whisker, ZrO 2 particle, as well as graphite flake, have been introduced into ZrB 2 matrix [13][14][15][16]. In comparison with these reinforcing phases, ZrN also possesses the superior properties, such as high melting point (2982 • C), high elastic modulus (389 GPa), high hardness (16 GPa), and high thermal conductivity (21.9 W/m K) [17].…”