Microstructure and Mechanical Property Evolution of Continuous Alumina Fibers during Long-term Exposure at Elevated Temperatures

doi:10.15541/jim20250462

Abstract

Abstract:

Continuous alumina fibers are widely used in fields including aerospace, national defense, military industry and energy resources, due to their exceptional chemical stability, oxidation resistance, structural stability and excellent high-temperature mechanical properties, making them promising engineering fibers with significant research value and market prospects. The long-term service temperature of alumina fibers varies depending on their composition, structure and morphology. In this work, phase composition, microstructure and mechanical property evolution of two commercial fibers (i.e. Nextel^TM 440 and NITIVY ALF^TM), and one lab-synthesized fiber (i.e. SLF72) were investigated after long-term treatment at elevated temperatures. Characterization was performed using different methods. The influence of phase composition and microstructure on mechanical properties was discussed, and the underlying mechanisms were elucidated. Furthermore, the mechanical properties of the fibers after heat treatment at different temperatures were compared. The results indicate that all three fibers undergo a transformation to mullite phase, accompanied by a general decline in single-filament tensile strength with increasing temperature. The formation and growth of mullite phase are identified as the primary reasons for the strength degradation after heat treatment. Compared with Nextel^TM 440 and NITIVY ALF^TM, the lab-synthesized fiber SLF72 demonstrates superior mechanical properties after long-term exposure at elevated temperatures. The long-term service temperature limits of the fibers follow the order: SLF72>NITIVY ALF^TM>Nextel^TM 440.

Key words: alumina fiber, long-term heat treatment, microstructure, single filament mechanical property

CLC Number:

TQ174

HU Juan, XU Di, NIE Huaiwen, LIN Genlian, YAN Jina. Microstructure and Mechanical Property Evolution of Continuous Alumina Fibers during Long-term Exposure at Elevated Temperatures[J]. Journal of Inorganic Materials, 2026, 41(8): 1110-1116.

Figures/Tables 7

Table 1 Room temperature properties of three continuous alumina fibers

Fiber	Composition (in mass)	Crystal structure	Tensile strength/GPa	Diameter/μm
Nextel^TM 440	70% Al₂O₃, 28% SiO₂, 2% B₂O₃	γ-Al₂O₃ + amorphous SiO₂	1.84	10-12
NITIVY ALF^TM	72% Al₂O₃, 28% SiO₂	γ-Al₂O₃ + amorphous SiO₂	1.78	7.0
SLF72	72% Al₂O₃, 28% SiO₂	γ-Al₂O₃ + amorphous SiO₂	1.72	7.6

Fig. 1 XRD patterns of three fibers after heat treatment at different temperatures for 100 h (a) NextelTM 440 fiber; (b) NITIVY ALFTM fiber; (c) SLF72 fiber

Fig. 2 SEM images of NextelTM 440 and NITIVY ALFTM fibers (a) Untreated NextelTM 440; (b) Untreated NITIVY ALFTM; (c) NextelTM 440 fiber after heat-treated at 1100 ℃ for 100 h; (d) NITIVY ALFTM after heat-treated at 1100 ℃ for 100 h; (e) NextelTM 440 after heat-treated at 1200 ℃ for 100 h; (f) NITIVY ALFTM after heat-treated at 1200 ℃ for 100 h; (g) NextelTM 440 after heat-treated at 1300 ℃ for 100 h; (f) NITIVY ALFTM after heat-treated at 1300 ℃ for 100 h

Fig. 3 SEM images of SLF72 fiber heat-treated at different temperatures for 100 h Surface: (a) Untreated, (f) 1300 ℃; Cross section: (b) Untreated, (c) 1100 ℃, (d) 1200 ℃, (e) 1300 ℃

Fig. 4 Strength retention rate of NextelTM 440, NITIVY ALFTM and SLF72 fibers after heat-treated at different temperatures for 100 h

Fig.5 Weibull plots of three fibers before and after heat treatment (a) Untreated NextelTM 440 fiber and treated at 1000 ℃ for 100 h; (b) Untreated NITIVY ALFTM fiber and treated at 1100 ℃ for 100 h; (c) Untreated SLF72 fiber and treated at 1100 ℃ for 100 h

Table 2 Weibull modulus (m) and the scale parameter (σ0) for three fibers untreated and treated at 1100 ℃ for 100 h

Fiber	Weibull modulus, m (untreated/treated at 1100 ℃ for 100 h)	Scale parameter, σ₀/MPa (untreated/ treated at 1100 ℃ for 100 h)
3M Nextel^TM 440	3.24/2.97	2365/1665
NITIVY ALF^TM	6.95/6.78	1771/1642
SLF72	8.86/7.42	1841/2043

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