Relationships Between Fiber Strength, Passive Oxidation and Scale Crystallization Kinetics of Hi‐Nicalon™‐S SiC Fibers

Hay, Randall S.; Fair, Geoff E.; Bouffioux, R.; Urban, Ed; Morrow, JoDean; Hart, Amelia H. C.; Wilson, Megan

doi:10.1002/9781118095355.ch4

Cited by 19 publications

(96 citation statements)

References 96 publications

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“…Similar strength values at 1200°C were already observed in ZrB 2 ‐based composites . This strength retention or increase could be due to the starting of formation of a SiO 2 glassy layer around the fiber, which is in compression state and exerts a healing effect of eventual cracks . The load–displacement curves of the high‐temperature tests were still linear up to fracture at 1200°C.…”

Section: Discussionsupporting

confidence: 75%

Effect of the Sintering Additive on Microstructure and Mechanical Properties of Hi‐Nicalon^TM SiC Fibers in a HfB₂ Matrix

et al. 2012

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This study is focused on the effect of the sintering additive on the microstructure and properties of HfB 2 composites reinforced with SiC Hi-Nicalon fibers. The materials were spark plasma sintered with addition of 5-10 vol% of Si 3 N 4 or ZrSi 2 . The fibers morphology was examined using scanning and transmission electron microscopy and remarkable differences were observed depending on the additive. Local hardness and Young's modulus were measured by nanoindentation to investigate the fiber mechanical behavior. The introduction of 20 vol% SiC short fibers into the HfB 2 matrix increased the fracture toughness up to 5.4 MPa m 1/2 for the material sintered with ZrSi 2 . The room temperature flexural strength of the materials containing fibers slightly decreased when ZrSi 2 was used, but with the addition of Si 3 N 4 an improvement of more than the 40%, as compared to the unreinforced material was observed.

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Section: Discussionsupporting

confidence: 75%

Effect of the Sintering Additive on Microstructure and Mechanical Properties of Hi‐Nicalon^TM SiC Fibers in a HfB₂ Matrix

et al. 2012

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“…The polyvinyl alcohol Hi‐Nicalon™‐S sizing on was removed by dissolution in boiling distilled deionized water . Five to six 7.5 cm length fiber tows were spread in a fused SiO 2 glass boat in a fused SiO 2 glass tube.…”

Section: Methodsmentioning

confidence: 99%

“…Hi‐Nicalon™‐S scale was characterized by TEM (FEI Talos 200 kV and FEI Titan 300 kV, ThermoFisher Scientific, Hillsboro, OR), using methods described elsewhere . Five to >50 filaments were characterized for each experiment; the number depended on TEM section quality.…”

Section: Methodsmentioning

confidence: 99%

Crystallization kinetics for SiO₂ formed during SiC fiber oxidation in steam

Hay

2019

J Am Ceram Soc

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The crystallization kinetics for SiO2 formed by oxidation of Hi‐Nicalon™‐S SiC fiber between 800 and 1600°C in Si(OH)4(g) saturated steam were determined. Glass SiO2 scale always formed first. Glass scale eventually crystallized to cristobalite, and during further oxidation the scale formed directly as cristobalite. Growth stress relaxed by viscous flow in SiO2 that formed as glass. Cristobalite formed by crystallization of this glass was relatively undeformed. In SiO2 that formed directly as cristobalite, growth stress relaxed by intense plastic deformation accompanied by dynamic recrystallization. There were therefore two layers in cristobalite scale: a heavily deformed inner layer and an undeformed outer layer. These layers were distinguished by TEM. SiO2 crystallization times were determined from the thicknesses of undeformed cristobalite and the SiC oxidation kinetics for glass scale formation. SiO2 crystallization kinetics were determined from the crystallization time distributions at different SiC oxidation temperatures in steam. For all temperatures the crystallization time growth exponent (n) was 1. There was a large decrease in crystallization rate between 1000 and 1100°C. Between 800 and 1000°C the activation energy (Q) for crystallization was 65 kJ/mol, between 1100 and 1500°C it was 110 kJ/mol, and at 1600°C it was ~500 kJ/mol. Analysis methods and results are discussed.

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“…Comparisons of results from the two methods led to the conclusion that the Weibull modulus m obtained using nominal strengths is the same as that obtained using true strengths. That study has since served as the principal basis for justifying continued use of nominal fiber strengths …”

Section: Introductionmentioning

confidence: 99%

Accurate determination of fiber strength distributions

Callaway

Zok

2016

J Am Ceram Soc

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Tensile strengths of small‐diameter ceramic fibers are commonly obtained from measured fracture loads on individual fibers and the average cross‐sectional area of the entire fiber population. The goal of the present article is to provide a critical assessment of the consequences of using the average fiber area in the inferred strength distribution. The issues are addressed through established theorems in convolution and uncertainty propagation as well as Monte Carlo simulations. Systematic errors introduced by using the average area are well‐represented by simple analytical formulae. The formulae are couched in terms of the coefficient of variation in fiber area and the dispersion in fiber strengths, characterized by the Weibull modulus. In turn, the formulae are used to determine the true values of Weibull modulus and reference strength from their nominal values. Random uncertainties associated with a finite number of tests decay slowly with number, in accordance with an inverse root scaling. When systematic errors are conflated with random uncertainties, accurate determination of the true Weibull modulus becomes increasingly challenging, even for seemingly large numbers of strength measurements. The results are used to assess the fidelity of previously‐reported experimental results based on nominal strength data.

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Relationships Between Fiber Strength, Passive Oxidation and Scale Crystallization Kinetics of Hi‐Nicalon™‐S SiC Fibers

Cited by 19 publications

References 96 publications

Effect of the Sintering Additive on Microstructure and Mechanical Properties of Hi‐Nicalon^TM SiC Fibers in a HfB₂ Matrix

Effect of the Sintering Additive on Microstructure and Mechanical Properties of Hi‐Nicalon^TM SiC Fibers in a HfB₂ Matrix

Crystallization kinetics for SiO₂ formed during SiC fiber oxidation in steam

Accurate determination of fiber strength distributions

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Relationships Between Fiber Strength, Passive Oxidation and Scale Crystallization Kinetics of Hi‐Nicalon™‐S SiC Fibers

Cited by 19 publications

References 96 publications

Effect of the Sintering Additive on Microstructure and Mechanical Properties of Hi‐NicalonTM SiC Fibers in a HfB2 Matrix

Effect of the Sintering Additive on Microstructure and Mechanical Properties of Hi‐NicalonTM SiC Fibers in a HfB2 Matrix

Crystallization kinetics for SiO2 formed during SiC fiber oxidation in steam

Accurate determination of fiber strength distributions

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Product

Resources

About

Effect of the Sintering Additive on Microstructure and Mechanical Properties of Hi‐Nicalon^TM SiC Fibers in a HfB₂ Matrix

Effect of the Sintering Additive on Microstructure and Mechanical Properties of Hi‐Nicalon^TM SiC Fibers in a HfB₂ Matrix

Crystallization kinetics for SiO₂ formed during SiC fiber oxidation in steam