Preparation of Nearly Stoichiometric SiC(Ti) Fibers with Highly Crystalline Microstructure from Polytitanocarbosilane

doi:10.15541/jim20240243

Abstract

Abstract:

Due to high tensile strength, excellent high-temperature and oxidation resistance, SiC fibers could be applied in many important fields such as aerospace and high-tech equipment. However, the current preparation temperature of domestically produced titanium-containing SiC fibers is relatively low, while the fibers are still full of excess oxygen and free carbon, which seriously affects their high-temperature resistance. In this work, the polytitanocarbosilane (PTCS) precursor was synthesized by using low-softening-point polycarbosilane (LPCS) and tetrabutyl titanate (Ti(OBu)₄). Mass fraction of titaniumin in the precursor was in the range of 0.36%-1.81%. The nearly stoichiometric polycrystalline SiC(Ti) fibers were successfully prepared through PTCS melt spinning, air curing, pyrolysis, and high-temperature sintering. Mass fractions of carbon and oxygen in SiC(Ti) fibers were 30.45% and <1.0%, respectively, with a C/Si ratio of approximately 1.05 and β-SiC grain size of 100-200 nm. The titanium element in SiC(Ti) fibers mainly existed in the form of TiC phase, which was beneficial to densification of the fibers during the sintering process. The SiC(Ti) fibers showed smooth and dense surface, exhibiting obvious transgranular fracture. Average tensile strength of the SiC(Ti) fibers was 2.04 GPa, and elastic modulus was 308 GPa. All results of this work provide important reference for the development of high-performance continuous SiC fibers.

Key words: polytitanocarbosilane, melt spinning, SiC fiber, precursor-derived ceramic, high-temperature sintering

CLC Number:

TQ343

GOU Yanzi, KANG Weifeng, ZHANG Qingyu. Preparation of Nearly Stoichiometric SiC(Ti) Fibers with Highly Crystalline Microstructure from Polytitanocarbosilane[J]. Journal of Inorganic Materials, 2024, 39(12): 1377-1383.

Figures/Tables 7

Fig. 1 FT-IR spectra of LPCS*, PTCS* precursors (a) and PTCS*-AC fibers (b)[4]

Table 1 Analytic results of LPCS*, PTCS-2*, PTCS-6*, and PTCS-10*

Polymer	LPCS*	PTCS-2*	PTCS-6*	PTCS-10*
A₂₁₀₀/A₁₂₅₀	1.01	0.98	0.95	0.85
Silicon content/ (%, in mass)	43.34	43.78	43.48	42.07
Carbon content/ (%, in mass)	40.44	40.71	41.28	40.87
Oxygen content/ (%, in mass)	1.32	1.58	2.52	3.11
Titanium content/ (%, in mass)	-	0.36	1.00	1.81
M_n	1126	1152	1249	1140
PDI	2.32	2.33	2.25	2.21
Ceramic yield/ (%, in mass)	49.9	61.6	64.2	67.5

Fig. 2 TG curves of LPCS*, PTCS* precursors (a) and PTCS*-AC fibers (b)[4]

Fig. 3 SEM images of surface (a, b) and cross section (c, d) of Si-C-Ti-O fibers

Fig. 4 XRD patterns of Si-C-Ti-O fibers (a) and SiC(Ti) fibers (b)

Fig. 5 SEM images of surface (a, b) and cross section (c, d) of Si-C-Ti intermediate fibers

Fig. 6 SEM images of surface (a, b) and cross section (c, d) of SiC(Ti) fibers

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