Synergistic influence of SiC and C₃N₄ reinforcements on the characteristics of ZrB₂-based composites

Figures & data

Table 1. Coding system and corresponding composition for each sample

Label	Composition
ZS	ZrB2–25 vol% SiC
ZSC	ZrB2–25 vol% SiC–5 wt% C3N4

Figure 1. FE-SEM micrographs of the polished area of (a) ZS and (b) ZSC ceramics by backscattered electrons

Figure 2. Rietveld refinement results (observed, simulated and difference) of SPSed samples: (a) ZS and (b) ZSC

Figure 3. Gibbs free energy of chemical reactions of Eqs. 4(4) $Zr{B}_2+C+N_2\left(g\right)=ZrC+2BN$(4) –6(6) $Zr{O}_2+3C=ZrC+2CO\left(g\right)$(6) versus temperature

Table 2. Quantitative analysis, crystallography data, and lattice parameters of ZS composite estimated through Rietveld refinement technique

Identified phases	Weight fraction (wt%)		Crystal system	Space group	Unit cell dimensions
	Before SPS	After SPS			a = b (nm)	c (nm)	α = β	γ
ZrB2	85.12	82.16	Hexagonal	P6/mmm	0.316911	0.353154	90	120
SiC	14.88	17.84	Cubic	F-43 m	0.435913	0.435913	90	90

Table 3. Quantitative analysis, crystallography data and lattice parameters of ZSC composite estimated through Rietveld refinement technique

Identified phases	Weight fraction (wt%)		Crystal system	Space group	Unit cell dimensions
	Before SPS	After SPS			a = b (nm)	c (nm)	α = β	γ
ZrB2	81.64	78.96	Hexagonal	P6/mmm	0.316803	0.353050	90	120
SiC	14.27	16.86	Cubic	F-43 m	0.435910	0.435910	90	90
C3N4	4.08	0	Hexagonal	-	-	-	-	-
ZrC	0	2.17	Cubic	Fm-3 m	0.467324	0.467324	90	90
BN	0	2.1	Hexagonal	P-3 m1	0.250999	0.668999	90	120

Figure 4. SEM image of ZSC sample revealing the presence of in-situ phases

Table 4. Properties of the spark plasma sintered ZrB₂-based composites

Sample code	Relative density (%)	Fracture toughness (MPa.m^1/2)	Vickers hardness (GPa)	Flexural strength (MPa)	Average Grain size of ZrB2 (µm)	Note
Z	76.5	1.9 ± 0.2	10.1 ± 1.6	187.6 ± 15	8	Previous work [56]
ZS	95.0	4.5 ± 0.3	17.4 ± 2.3	460.2 ± 20	5.5	Present work
ZC	99.8	5.4 ± 0.4	16.2 ± 2.2	516.4 ± 20	4.5	Previous work [56]
ZSC	100.8	6.1 ± 0.4	21.2 ± 2.5	580.2 ± 25	3	Present work

Figure 5. Indentation-induced crack paths in the polished surface of (a, b) ZS and (c, d) ZSC composites

Figure 6. SEM fractographs of (a) ZS and (b) ZSC samples

Ahmadi Z, Zakeri M, Habibi-Yangjeh A, et al.. A novel ZrB2–C3N4 composite with improved mechanical properties. Ceram Int. 2019;45:21512–21519.

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