Microstructure and high-temperature strength of textured and non-textured ZrB₂ ceramics

Figures & data

Figure 1 XRD patterns of (a) non-textured surface, (b) textured SS and (c) textured TS of ZrB₂ samples after sintering.

Table 1 Sintering temperature, densities, open porosities and ZrB₂ grain sizes of the sintered ZrB₂ ceramics.

	Sintering temperature (°C)	Density (g cm^−3)	Open porosity (%)	ZrB2 grain size (μm)
Non-textured ZrB2	1750 1700	5.79 5.78	0.2 0.1	∼5.8 ∼2.8
Textured ZrB2	1750	5.78	0.1	∼2.5 (TS) ∼2.4 (SS)

Figure 2 SEM image of the starting ZrB₂ powder.

Figure 3 SEM images of polished surfaces for textured ZrB₂ ceramics sintered at 1750 °C: (a) TS, (b) SS; and non-textured ZrB₂ sintered at (c) 1750 °C and (d) 1700 °C.

Figure 4 SEM image (top left) and compositional maps of the polished surface of non-textured ZrB₂ sintered at 1750 °C for 5 min.

Figure 5 TEM pictures of the ZrB₂ ceramics; (a) and (b) matched and mismatched ZrB₂/ZrB₂ grain boundaries; (c) BN flakes and amorphous phase located at the triple point of the matrix; (d) elemental analysis of the amorphous phase in (c).

Table 2 Vickers hardness, Young's modulus and flexural strength at various conditions.

	Sample name	Sintering temperature (°C)/sample direction	Vickers hardness (GPa)	Young's modulus (GPa)	Four point bending strength (MPa)
RT	1500 °C	1600 °C	1650 °C
Non-textured ZrB2	ZB1700	1700	17.3±0.4	463±26	600±97		748±5
	ZB1750	1750			460±59	420±43	428±61	333±20
Textured ZrB2	ZB-TS	1750/⊥ c-plane (TS)	19.1±0.3	463±16	574±31	758±52	810±60	591±64
	ZB-SS	1750/∥ c-plane (SS)	17.5±0.2	505±10	723±61		650±38

Figure 6 Flexural strength of textured and non-textured ZrB₂ ceramics at room and elevated temperatures.

Figure 7 Load–displacement curves of the flexural strength tests of ZrB₂ ceramics from room temperature to 1650 °C.

Figure 8 Tension side fracture surfaces of ZrB₂ ceramics after flexural strength testing at room and high temperature. (a) ZB1750, room temperature (RT), (b) ZB1750, 1600 °C, (c) ZB1700, RT and (d) ZB1700, 1600 °C.

Figure 9 Bright-field TEM images show the successive growth of cavities at adjacent locations and the evolution of dislocations in tension surfaces of ZB1700 tested at different temperature. (a), (b) RT; (c), (d) 1500 °C; (e), (f) 1600 °C; (g), (h) 1650 °C. The white solid arrows indicate dislocations, the dashed arrows indicate sub-grain boundaries and the black solid arrows indicate the cavities formed at the triple points.