High-Temperature Oxidation of Carbon-Carbon Composite Materials in Air

Shemet, V. Zh.; Помыткин, А. П.; Protsenko, T. G.; Zoikin, P. I.; Lavrenko, V. A.

doi:10.1007/978-94-011-3676-1_120

Cited by 9 publications

(13 citation statements)

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“…Carbon has been observed to oxidize at temperatures as low as 500-550°C [6,12,13]. Stressed oxidation of C/SiC at 550°C did show strength degradation due to oxidation.…”

Section: Constant Loadmentioning

confidence: 99%

Degradation of Continuous Fiber Ceramic Matrix Composites under Constant Load Conditions

Halbig

Brewer

Eckel

2000

Mechanical, Thermal and Environmental Testing and Performance of Ceramic Composites and Components

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Ten different ceramic matrix composite (CMC) materials were subjected to a constant load and temperature in an air environment. Tests conducted under these conditions are often referred to as stressed oxidation or creep rupture tests. The stressed oxidation tests were conducted at a temperature of 1454°C at stresses of 69 MPa, 172 MPa and 50% of each material's ultimate tensile strength. The ten materials included such CMCs as C/SiC, SiC/C, SiC/SiC, SiC/SiNC and C/C. The time to failure results of the stressed oxidation tests will be presented. Much of the discussion regarding material degradation under stressed oxidation conditions will focus on C/SiC composites. Thermogravimetric analysis of the oxidation of fully exposed carbon fiber (T300) and of C/SiC coupons will be presented as well as a model that predicts the oxidation patterns and kinetics of carbon fiber tows oxidizing in a nonreactive matrix.

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“…Carbon has been observed to oxidize at temperatures as low as 500-550°C [6,12,13]. Stressed oxidation of C/SiC at 550°C did show strength degradation due to oxidation.…”

Section: Constant Loadmentioning

confidence: 99%

Degradation of Continuous Fiber Ceramic Matrix Composites under Constant Load Conditions

Halbig

Brewer

Eckel

2000

Mechanical, Thermal and Environmental Testing and Performance of Ceramic Composites and Components

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“…These can be significant and can thoroughly mix the values reported for the oxidation of bulk carbon in the literagas at the sample surface. Eckel et al 6 concluded gas mixing ture, 9,10 although they are somewhat on the low side of this caused solely by thermal convection in static experiments was range. Two explanations for the low values are possible: either sufficient to eliminate the effect of boundary layer diffusion.…”

Section: Introductionmentioning

confidence: 96%

“…activation energy, Q, for the process: In conclusion, considering all the sources of error that could be estimated numerically and in light of the numerous assump-Q ϭ Ϫ2.303R (slope) (2) tions used in this analysis, the agreement between the two approaches to determining the recession rates appears adequate, where R is the gas constant. oxidation of C above 1073 K is under diffusion control, [10][11][12][13][14] and diffusion may play a role in our study as well. Since the recession and TGA mass loss data are linear, however, the ratelimiting diffusion step cannot be within the channels created by the oxidation of the C interface.…”

Section: Introductionmentioning

confidence: 99%

“…However, this does not rule out reacthickness should be somewhere between the two results. tion control, because it is well known that the type of C, [10][11][12] The boundary layer thickness was calculated to be 5.2 ϫ impurities, 13 and surface morphology 14 strongly influence the 10 Ϫ3 m using the length of the entire sample (4.0 ϫ 10 Ϫ3 m) and measured activation parameters.…”

Section: Introductionmentioning

confidence: 99%

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Oxidation of the Carbon Interface in Nicalon‐Fiber‐Reinforced Silicon Carbide Composite

Windisch

Henager

Springer

et al. 1997

Journal of the American Ceramic Society

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A few recent papers have been published addressing the The recession rates for 10 ؊6 -m-thick C interfaces in chemikinetics of C-interface removal 3-6 from SiC/SiC but under concal vapor infiltrated SiC reinforced with Nicalon fibers were ditions different from those used in our previous studies. In calculated from thermogravimetric data, assuming all of particular, either the C interfaces were generally thinner than the mass losses were due to C oxidation, and found to be the 10 Ϫ6 -m-thick interfaces in samples used in our work, or the consistent with the measured recession distances of the C environment contained significantly more O 2 . Filipuzzi et al. 3,4 interface, which were surprisingly uniform across the commeasured mass gains due to SiO 2 formation coupled with paraposite. Agreement between the two approaches for a microbolic mass-loss kinetics; however, the C interfaces in their structurally complex material indicates thermogravimetric samples were approximately 10 Ϫ7 m thick, and the environment analysis could be an important tool for understanding enviwas flowing pure O 2 . The parabolic behavior suggested that the ronmental effects in ceramic composites with reactive inter-C oxidation was largely controlled by transport of O 2 along faces. Mass losses were linear within the first 1.08 ؋ 10 4 s the interface region. A comprehensive model was developed to 2.16 ؋ 10 4 s between 1073 and 1373 K and between 3.1 ؋ that included the effects of SiO 2 pinching off the channels 10 2 and 2.5 ؋ 10 3 Pa O 2 . Calculated reaction orders with created by interface removal. Similar results were observed by respect to O 2 were between 0.5 and 1.0 at 1373 K, and Tortorelli et al. 5 In contrast, Eckel et al. 6 performed an oxidation activation energies were about 50 kJؒmol ؊1 . Analysis of the study on a C-cored SiC material that simulated the situation in kinetic data and estimates of gas boundary layer thickness an interface and found linear-parabolic kinetics in pure O 2 . A suggest the mechanism for the C-interface oxidation linear rate constant equal to 2.5 ϫ 10 Ϫ6 mиs Ϫ1 was determined involved reaction control, but the possibility of diffusion for the recession of the C core at 1073 K, and it was argued control for some conditions cannot be ruled out.that, under these conditions, the kinetics were controlled by the oxidation reaction. I. IntroductionIn the present study, the rate of C-interface removal from a SiC/SiC composite material, whose mechanical properties were T IME-DEPENDENT crack growth, referred to as subcritical determined, 1 was investigated for a range of environmental crack growth or slow crack growth (SCG), likely controls conditions and sample characteristics not previously studied. the long-term life of ceramic matrix composite (CMC) strucSpecifically, the composite contained 10 Ϫ6 -m-thick C interfaces, tural materials at elevated temperatures when preexisting flaws and experimental temperatures were between 1073 and 1373 K are present. 1 Consequently, using CMCs in systems where longwith ...

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“…In oxygen however graphite forms vapor species such as carbon monoxide at temperatures well below the melting point of silver (12). Carbon monoxide is more stable than many metal oxides.…”

Section: Background -Materials Propertiesmentioning

confidence: 99%

The effects of interrupting elevated currents on the erosion and structure of silver-graphite

Wingert

Electrical Contacts - 1996. Proceedings of the Forty-Second IEEE Holm Conference on Electrical Contacts. Joint With the 18th In

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The surfaces of silver-5% graphite contacts are greatly disrupted when they are subjected to the interruption of arcs of over 1000 amperes. This paper describes the disruption structures observed and proposes mechanisms for their formation. Large masses of silver and layers rich in graphite develop on the contact surfaces. It is suggested that poor wetting of the graphite by molten silver is a major cause of this phase separation. Even if welds form between silver masses on the surfaces of opposing contacts the total weld strength is low due to the lack of metallic continuity between the silver masses and the silver in the bulk contact. It is shown that silver masses of up to .040 grams can be ejected from the arc region to distances of up to 5 mm. The loss of silver in large masses makes the weight loss in consecutive operations erratic. The probability of arcs restriking increases after the initial interruption operations. The greater probability of restriking is thought to be a result of greater carbon concentration on the contact surfaces andlor the mating through the large silver masses on the surface which can break up into the intercontact gap during interruption. Test results for pure silver and pure graphite are presented for comparison with the results for the composite materials.

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High-Temperature Oxidation of Carbon-Carbon Composite Materials in Air

Cited by 9 publications

References 0 publications

Degradation of Continuous Fiber Ceramic Matrix Composites under Constant Load Conditions

Degradation of Continuous Fiber Ceramic Matrix Composites under Constant Load Conditions

Oxidation of the Carbon Interface in Nicalon‐Fiber‐Reinforced Silicon Carbide Composite

The effects of interrupting elevated currents on the erosion and structure of silver-graphite

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