Kinetics and crystallization studies by in situ X-ray diffraction of the oxidation of chemically vapour deposited SiC

Sibieude, F.; Rodríguez, José Amparo; Clavaguera-Mora, M.T.

doi:10.1016/0040-6090(91)90507-t

Cited by 25 publications

(15 citation statements)

References 14 publications

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“…In Figure , B results for Hi‐Nicalon™‐S (Table ) are compared to bulk SiC for both wet and dry oxidation . B C data for dry air oxidation that were explicitly stated to form crystalline scale are also shown .…”

Section: Resultsmentioning

confidence: 99%

Oxidation kinetics strength of Hi‐Nicalon^TM‐S SiC fiber after oxidation in dry and wet air

2017

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Hi‐Nicalon™‐S SiC fiber strengths and Weibull moduli were measured after oxidation for up to 100 hours between 700°C and 1400°C in wet and dry air. SiO2 scale thickness and crystallization extent were measured by TEM. The effect of furnace environment on trace element levels in the SiO2 scales was characterized by secondary ion mass spectroscopy. Crystallization kinetics and Deal‐Grove oxidation kinetics for glass and crystalline scale, and the transition between them, were modeled and determined. Crystallization retards oxidation kinetics, and scale that formed in the crystalline state was heavily deformed by the growth stress accompanying SiC oxidation volume expansion. Glass scales formed in dry air slightly increased fiber strength. Glass scales formed in wet air did not increase strength, and in some cases significantly decreased strength. Scales more than 200 nm thick were usually partially or completely crystallized, which degraded fiber strength. Contamination of scales by trace impurities such as Al and Ca during heat treatment inhibited crystallization. The oxidation kinetics and the strengths of oxidized Hi‐Nicalon™‐S fibers are compared with previous studies on SiC fibers, bulk SiC, and single‐crystal SiC. Empirical relationships between oxidation temperature, time, scale thickness, and strength are determined and discussed.

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Section: Resultsmentioning

confidence: 99%

Oxidation kinetics strength of Hi‐Nicalon^TM‐S SiC fiber after oxidation in dry and wet air

2017

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“…Crystallization of SiO 2 scales to cristobalite or tridymite reduces oxygen permeability, and is a source of confusion in interpretation of SiC oxidation data that does not distinguish crystalline and amorphous scales . Crystallization of SiO 2 scales on nominally pure SiC is reported to start at temperatures of 1400°C, at temperatures as low as 700°C, and at temperatures in between . Disparity in these results illustrates the extreme sensitivity of silica crystallization to SiC impurities and trace H 2 O and other gases in the environment …”

Section: Introductionmentioning

confidence: 95%

Hi‐Nicalon^TM‐SSiC Fiber Oxidation and Scale Crystallization Kinetics

et al. 2011

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The oxidation and scale crystallization kinetics of Hi‐NicalonTM‐S SiC fibers were measured after oxidation in dry air between 700° and 1400°C. Scale thickness, composition, and crystallization were characterized by TEM with EDS, supplemented by SEM and optical microscopy. TEM was used to distinguish oxidation kinetics of amorphous and crystalline scales. Oxidation initially produces an amorphous silica scale that incorporates some carbon. Growth kinetics of the amorphous scale was analyzed using the flat‐plate Deal‐Grove model. The activation energy for parabolic oxidation was 248 kJ/mol. The scales crystallized to tridymite and cristobalite, starting at 1000°C in under 100 h and 1300°C in under 1 h. Crystallization kinetics had activation energy of 514 kJ/mol with a time growth exponent of 1.5. Crystalline silica nucleated at the scale surface, with more rapid growth parallel to the surface. Crystalline scales cracked from thermal residual stress and phase transformations during cool‐down, and during oxidation from tensile hoop growth stress. High growth shear stress was inferred to cause intense dislocation plasticity near the crystalline SiO2–SiC interphase. Crystalline scales were thinner than amorphous scales, except where growth cracks allowed much more rapid oxidation.

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“…During SiC oxidation SiO 2 crystallization starts between 700 and 1400°C . The wide range in temperature is due to the extreme sensitivity of silica crystallization to impurities, and to H 2 O and other gases in the oxidizing environment .…”

Section: Introductionmentioning

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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Kinetics and crystallization studies by in situ X-ray diffraction of the oxidation of chemically vapour deposited SiC

Cited by 25 publications

References 14 publications

Oxidation kinetics strength of Hi‐Nicalon^TM‐S SiC fiber after oxidation in dry and wet air

Oxidation kinetics strength of Hi‐Nicalon^TM‐S SiC fiber after oxidation in dry and wet air

Hi‐Nicalon^TM‐SSiC Fiber Oxidation and Scale Crystallization Kinetics

Crystallization kinetics for SiO₂ formed during SiC fiber oxidation in steam

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Kinetics and crystallization studies by in situ X-ray diffraction of the oxidation of chemically vapour deposited SiC

Cited by 25 publications

References 14 publications

Oxidation kinetics strength of Hi‐NicalonTM‐S SiC fiber after oxidation in dry and wet air

Oxidation kinetics strength of Hi‐NicalonTM‐S SiC fiber after oxidation in dry and wet air

Hi‐NicalonTM‐SSiC Fiber Oxidation and Scale Crystallization Kinetics

Crystallization kinetics for SiO2 formed during SiC fiber oxidation in steam

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Product

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Oxidation kinetics strength of Hi‐Nicalon^TM‐S SiC fiber after oxidation in dry and wet air

Oxidation kinetics strength of Hi‐Nicalon^TM‐S SiC fiber after oxidation in dry and wet air

Hi‐Nicalon^TM‐SSiC Fiber Oxidation and Scale Crystallization Kinetics

Crystallization kinetics for SiO₂ formed during SiC fiber oxidation in steam