Enhancing Mechanical Property of SiC Fiber by Decreasing Fiber Diameter through a Modified Melt-spinning Process

doi:10.15541/jim20170512

Abstract

Abstract:

Strength, modulus and flexibility as three important mechanical properties for silicon carbide (SiC) fibers can be affected by diameter of SiC fiber, which is controled by specific melt-spinning process. In this study, effects of spinning temperature (T), spinning pressure (P) and winding speed (V) on diameter of polycarbosilane (PCS) fiber were studied. Mechanisms for the fiber breakage during spinning process was explored, and relationship between diameter and mechanical properties of SiC fiber was also analyzed. The results show that diameter of the PCS fiber is significantly reduced either by decreasing spinning temperature, or decreasing spinning pressure or increasing winding speed. The finest diameter of PCS fiber is 13.5 μm with the optimized spinning parameter T=337℃, P=0.2 MPa and V=240 m/min. After high-temperature pyrolysism, diameter of the obtained PCS fiber can be reduced from 13.8 μm to 9.5 μm. Meanwhile, tensile strength of SiC fibers increases from 1.7 GPa to 2.9 GPa, and Young’s modulus increases from 181 GPa to 233 Gpa, respectively, with less dispersed strength distnbution and enhanced flexibility.

Key words: polycarbosilane, melt-spinning, SiC fiber, diameter

CLC Number:

TQ174

WANG Guo-Dong, SONG Yong-Cai. Enhancing Mechanical Property of SiC Fiber by Decreasing Fiber Diameter through a Modified Melt-spinning Process[J]. Journal of Inorganic Materials, 2018, 33(7): 721-727.

Figures/Tables 13

Fig. 1 GPC and FT-IR spectrum of PCS-1

Fig. 2 Relationship between temperature and melt viscosity of PCS-1

Fig. 3 Influence of temperature on diameter of PCS fiber

Fig. 4 Influence of spinning pressure on diameter of PCS fiber

Fig. 5 Influence of winding speed on diameter of PCS fiber

Table 1 Melting spinning conditions and result of spinning

Samples	Spinning temperature/℃	Winding speed /(m•min^-1)	Pressure /MPa	Continue spinning time/min	Diameter /μm
PCS_f-1	336	240	0.25	35.0	14.7
PCS_f-2	336	240	0.20	10.0	12.5
PCS_f-3	336	213	0.20	27.0	13.0
PCS_f-4	337	267	0.25	14.0	14.5
PCS_f-5	337	267	0.20	3.0	11.8
PCS_f-6	337	240	0.20	32.0	13.5
PCS_f-7	337	240	0.30	35.0	17.4
PCS_f-8	337	240	0.15	0.5	12.4
PCS_f-9	338	267	0.20	34.0	13.9
PCS_f-10	338	240	0.15	16.0	12.7

Fig. 6 Optical photos of PCSf-6 and PCSf-7

Fig. 7 Illustrated process and photos of fiber breaking(a) Ductile drawing and curing zone; (b) Transient stable zone; (c) Brittle fracture zone

Fig. 8 Schematic diagram of breaking pattern

Table 2 Mechanical properties of SiC fibers with different diameters

Samples	PCS fiber diameter/μm	SiC fiber diameter/μm	Strength /GPa	Modulus /GPa
SiC-1	13.5	9.5	2.9	233
SiC-2	16.0	10.7	2.4	210
SiC-3	17.4	12.1	1.8	191
SiC-4	18.3	13.8	1.7	181

Fig. 9 SEM image of SiC-1

Fig. 10 Weibull statistics of tensile strength of SiC fibers with different diameters

Table 3 Weibull parameters of SiC fibers with different diameters

Samples	SiC fiber diameter/μm	Weibull modulus	Scale parameter, σ₀/GPa	Related coefficient, R²
SiC-1	9.5	0.26	0.011	0.95
SiC-2	10.7	0.25	0.019	0.97
SiC-3	12.1	0.22	0.034	0.95
SiC-4	13.8	0.16	0.017	0.97

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