Contribution to the Understanding of the Microstructure of First Generation Si‐C‐O Fibers

Teyssandier, F.; Puyoo, Géraldine; Mazerat, Stéphane; Chollon, Georges; Pailler, R.; Babonneau, Florence

doi:10.1002/9781118217528.ch1

Cited by 5 publications

(9 citation statements)

References 23 publications

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“… 45 Some statistics on flaw location were extracted. Past studies on as received fibers revealed that 0%, 30%, and 80% of the defects are internal on TS, NL, and HNL, respectively 70 . The present observations indicate the defects of TS are systematically located at the scale‐fiber interface.…”

Section: Resultssupporting

confidence: 51%

“…The mirror constant A m was previously reported for non‐oxidized fibers 70 considering Δ σ = 0 MPa as a convention 90 . At intermediate temperatures, the microstructure of SiC fibers is considered to be stable.…”

Section: Resultsmentioning

confidence: 99%

“…As mentioned above, three different types of fibers were used for this work: Tyranno Grade S (UBE Industries Ltd.), Nicalon, and Hi‐Nicalon (NGS Advanced Fibers Co. Ltd.), respectively, named TS, NL, and HNL afterward. Their chemical composition and physical properties are gathered in Table 1 70–72 . Two types of oxidation tests were performed in ambient atmosphere (P H2O ranging from 0.35 to 1.35 KPa, averaging to 0.70 KPa at 22°C).…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Oxidation under stress of SiC‐based fibers at intermediate temperature and ambient air

Mazerat,

El‐Morsli,

Sarrazin

et al. 2024

J Am Ceram Soc.

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If the temperature and environment effects on the oxidation of SiC fibers have been extensively documented, the impact of external stresses (stress‐oxidation coupling effect) remains questioned. Therefore, interrupted static fatigue tests were conducted on filaments. Surviving specimens (>60%) were subsequently tensile tested and fracture surfaces recovered for analysis. The external stress was found to have no impact on the oxidation regime (linear or parabolic) nor on its rate, which is comparable to literature data. As long as the slow crack growth (SCG) incubates (negligible growth rate), the oxidation was shown to govern the embrittlement. Fracture surface analysis revealed tensile residual stresses, attributed to a wedge effect when specimens were unloaded. Rare tests (<2%) were interrupted while the crack had significantly grown highlighting the successive crack fronts. Sources of residual stresses and differences between fiber types (flaw position inducing a bias on lifetime prediction) are discussed. In these circumstances, a coupling effect between the oxidation embrittlement and the SCG could be assumed for moderate stress levels, which is pertinent for most of ceramic matrix composite applications.

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Section: Resultssupporting

confidence: 51%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Oxidation under stress of SiC‐based fibers at intermediate temperature and ambient air

Mazerat,

El‐Morsli,

Sarrazin

et al. 2024

J Am Ceram Soc.

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show abstract

“…Three generations of SiC-based fibers are commercially available, synthesized by the conversion of polycarbosilane (Nippon Carbon Co. Ltd. under the trade name Nicalon ® ), or derivate containing a small amount of organometallic (UBE Industries Ltd. named Tyranno ® ). The first-generation fibers are composed of SiC grains in nanometer range embedded in a silicon oxycarbide phase (SiCO) and free aromatic carbon (Cfree) as basic structural units [23,24]. Second generation fibers are however electron beam cured, hence oxygen free, and contain excess of carbon inhibiting SiC grain growth, also in nanometer range.…”

Section: Methodsmentioning

confidence: 99%

Effect of microstructure and chemical composition on subcritical crack growth in SiC-based fiber tows

Mazerat¹,

Pailler²

2021

Ceramics International

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“…The carbon structure is poorly organized in both SiC-C materials considered. In the fibers, the carbon domains are short and stacked in 2-3 polyaromatic layers inserted between the SiC grains of the continuum [20,26], giving rise to a highly disordered (as shown by the Raman spectra, in Fig. 1) and isotropic microstructure.…”

Section: Preliminary Analyses and Behavior Of The Various Carbon Specimensmentioning

confidence: 99%

The high temperature reaction of ammonia with carbon and SiC–C ceramics

Chollon

2021

Journal of the European Ceramic Society

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This contribution aimed at developing a treatment under ammonia in order to eliminate free carbon from the surface of SiC-based fine ceramics like fibers or coatings. The reaction of NH3 with graphitic and non-graphitic carbon was first investigated through kinetic measurements, in situ gas phase analysis and physicochemical investigations of the solid. The carbon etching rate is controlled by heterogeneous reactions involving active sites arising from bulk structural defects and the formation of HCN. A selection of SiC-based fibers and coatings with various carbon contents and (micro)structures was treated in ammonia in favorable conditions. The analyses of the tested SiC-C specimens revealed a reduction of the free carbon content and, simultaneously, a nitridation of the initial Si-C-(O) continuum over a reaction layer. The growth rate, composition and the volume change of this layer vary with the initial microstructure. The ammonia treatment is able to restore the adhesion of carbon-contaminated surfaces.

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Contribution to the Understanding of the Microstructure of First Generation Si‐C‐O Fibers

Cited by 5 publications

References 23 publications

Oxidation under stress of SiC‐based fibers at intermediate temperature and ambient air

Oxidation under stress of SiC‐based fibers at intermediate temperature and ambient air

Effect of microstructure and chemical composition on subcritical crack growth in SiC-based fiber tows

The high temperature reaction of ammonia with carbon and SiC–C ceramics

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