(Zr, Hf, Nb, Ta, W)C-SiC Composite Ceramics: Preparation via Precursor Route and Properties

doi:10.15541/jim20240385

Abstract

Abstract:

High-entropy carbide (HEC) ceramics are distinguished by their high hardness, oxidation resistance, corrosion resistance, wear resistance, and high thermal conductivity, positioning them as promising candidates for application in extreme environments. However, inherent brittleness of these high-entropy ceramics limits their further application. In order to enhance the toughness of HEC ceramics, polycarbosilane (PCS), a precursor of silicon carbide (SiC), was added into the precursor of (Zr, Hf, Nb, Ta, W)C high-entropy ceramic. The in-situ formed SiC (SiC_i) by pyrolysis of PCS can serve as reinforcement for HEC ceramics. The results demonstrate that the volume fraction of SiC in the ceramics obtained from the pyrolysis of PCS is 23.38%. The SiC phases, with an average grain size of 1.19 μm, are evenly distributed in the high-entropy ceramic matrix. The pyrolysis process of ceramic precursors was investigated, revealing that the pyrolysis products of PCS exit as amorphous O_x-Si-C_y at low pyrolysis temperature, while a crystalline SiC phase emerges when the pyrolysis temperature exceeds 1500 ℃. Bulk (Zr, Hf, Nb, Ta, W)C-SiC_i ceramic was prepared by hot-pressing of precursor-derived ceramic powders obtained through pyrolysis at 1600 ℃. Mechanical properties of (Zr, Hf, Nb, Ta, W)C-SiC_i ceramic bulk were investigated, and composite ceramic bulks toughened by commercial silicon carbide nanopowders or silicon carbide whiskers were also prepared for comparison. Compared with (Zr, Hf, Nb, Ta, W)C ceramic, all composite ceramic bulks exhibit enhanced flexural strength and toughness. Notably, the in-situ generated SiC_i via precursor-derived method shows the most significant toughening effect. Flexural strength and fracture toughness of (Zr, Hf, Nb, Ta, W)C-SiC_i ceramic are (698±9) MPa and (7.9±0.6) MPa·m^1/2, respectively, representing improvements of 17.71% and 41.07% compared to that of (Zr, Hf, Nb, Ta, W)C ceramic bulk. Taking all above data into comprehensive account, the improvement is mainly due to the small grain size and uniform distribution of SiC in the composite ceramics prepared via precursor-derived method, which enhance energy consumption and hinder crack propagation under external stress.

Key words: precursor-derived method, high-entropy carbide, silicon carbide, mechanical property

CLC Number:

TB383

LI Ziwei, GONG Weilu, CUI Haifeng, YE Li, HAN Weijian, ZHAO Tong. (Zr, Hf, Nb, Ta, W)C-SiC Composite Ceramics: Preparation via Precursor Route and Properties[J]. Journal of Inorganic Materials, 2025, 40(3): 271-280.

Figures/Tables 18

Fig. 1 (a) TG-DTG curves of cured PHEC-PCS and (b-e) MS spectra of gases released during pyrolysis of cured PHEC-PCS

Fig. 2 XPS spectra of HEC-W5-SiCi obtained at different pyrolysis temperatures (a, b) Nb3d and Ta4f of HEC-W5-SiCi-1000; (c, d) Hf4f and W4f of HEC-W5-SiCi-1200; (e, f) Zr3d and Si2p of HEC-W5-SiCi-1400. Colorful figures are available on website

Fig. 3 XRD patterns of PHEC-PCS pyrolyzed in the range of 600-1800 ℃

Fig. 4 SEM images of HEC-W5-SiCi powder pyrolyzed in the range of 600-1800 ℃

Fig. 5 SEM image and EDS mappings of HEC-W5-SiCi powder pyrolyzed at 1600 ℃

Fig. 6 (a-c) Surface SEM images and (d-f) grain size statistics of SiC in (a, d) HEC-W5-SiCi, (b, e) HEC-W5-SiCp, and (c, f) HEC-W5-SiCw bulk ceramics

Fig. 7 Mechanical properties of HEC-W5, HEC-W5-SiCp, HEC-W5-SiCw, and HEC-W5-SiCi ceramics (a) Vickers hardness; (b) Elasticity modulus; (c) Flexural strength; (d) Fracture toughness

Fig. 8 Morphologies of crack extension of ceramics after Vickers hardness test (a) HEC-W5; (b) HEC-W5-SiCp; (c) HEC-W5-SiCw; (d) HEC-W5-SiCi

Fig. 9 Flexural strength and fracture toughness of HEC-W5- SiCi ceramics of this work and data in literature[11,14,22⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓ -34] *This literature only has fracture toughness data.

Table S1 Elemental content analysis of HEC-SiCi-1600

Empirical formula	Content/(%, in mass)
Empirical formula	Zr	Hf	Nb	Ta	W	Si	C	O
(Zr_0.238Hf_0.237Nb_0.237Ta_0.237W_0.05)-Si_0.347C_1.405O_0.031	13.1	25.6	13.3	25.9	5.5	5.9	10.2	0.3

Table S2 Mechanical properties of HEC-W5, HEC-W5-SiCp, HEC-W5-SiCw, and HEC-W5-SiCi ceramics

Sample	Vickers hardness/GPa	Elasticity modulus/GPa	Flexural strength/MPa	Fracture toughness/ (MPa·m^1/2)	Shape factor, Y
HEC-W5	23.82±0.49	447.07±3.71	593±15	5.6±0.2	2.537
HEC-W5-SiC_p	21.79±0.78	418.96±5.24	675±12	7.1±0.5	2.535
HEC-W5-SiC_w	21.61±0.35	435.50±4.38	726±18	6.7±0.3	2.533
HEC-W5-SiC_i	23.03±0.63	575.70±8.25	698±9	7.9±0.6	2.534

Table S3 Flexural strength and fracture toughness of HEC-W5-SiCi ceramics and previous studies[11,14,22⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓ -34]

Sample	Flexural strength/MPa	Fracture toughness/(MPa·m^1/2)	Ref.
(Ti_0.25Nb_0.25Hf_0.25Ta_0.25)C_0.3N_0.7	481±56^b	7.17±0.62^c	[22]
(TiZrHfVNbTa)C	473±21^b	3.6±0.2^c	[23]
(Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C	400^b	5.9^c	[24]
(Hf_0.2Zr_0.2Ta_0.2Nb_0.2Ti_0.2)C	450±64^b	4.8±0.2^c	[25]
(Hf_0.2Ta_0.2Zr_0.2Nb_0.2Ti_0.2)C	494^b	2.306^d	[26]
(Hf_0.2Zr_0.2Ti_0.2Ta_0.2Nb_0.2)C	421±27^a	3.5±0.3^d	[27]
(Ti_0.2Hf_0.2Zr_0.2Nb_0.2Ta_0.2)B₂	-	2.83±0.15^e	[28]
(Hf_0.2Nb_0.2Ta_0.2Ti_0.2Zr_0.2)B₂	376±25^b	4.70±0.27^c	[29]
(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂	339±17^a	3.81±0.40^c	[30]
(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂-20SiC_p	447±45^a	4.85±0.33^c	[30]
(NbTaZrW)C-50SiC_P	455^b	6.54^c	[31]
(HfZrTaTiW)C-1.5wt%SiC_nw	626.5^b	6.2^e	[32]
(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂-20SiC_p	750±43^b	4.12±0.20^e	[33]
(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂-20SiC_p	476±42^b	4.63±0.23^c	[34]
(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C-20SiC_p	554±73^a	5.24±0.41^c	[11]
HEC-W5	593±15^b	5.6±0.2^c	[14]
HEC-W5-SiC_p	675±12^b	7.1±0.5^c	This work
HEC-W5-SiC_w	726±18^b	6.7±0.3^c	This work
HEC-W5-SiC_i	698±9^b	7.9±0.6^c	This work

Fig. S1 XPS spectra of HEC-W5-SiCi (a-d) W4f, Zr3d, Hf4f and Si2p of HEC-W5-SiCi-1000; (e, f) Zr3d and Si2p of HEC-W5-SiCi-1200

Fig. S2 SEM images of commercialized SiCp and SiCw

Fig. S3 (a) Relative density of HEC-W5 ceramics and HEC-W5-SiC ceramics, (b) XRD patterns of different EC-W5-SiC ceramics

Fig. S4 SEM image and EDS mappings of HEC-W5-SiCp ceramics surface

Fig. S5 SEM image and EDS mappings of HEC-W5-SiCw ceramics surface

Fig. S6 SEM images and EDS mappings of HEC-W5-SiCi ceramics surface

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