Oxidation of Ultrahigh Temperature Ceramics in Water Vapor

Nguyen, QuynhGiao N.; Opila, Elizabeth J.; Robinson, R. Craig

doi:10.1149/1.1786929

Cited by 59 publications

(85 citation statements)

References 7 publications

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“…Among UHTCs, ZrB 2 -SiC composites are reported to have good resistance to thermal shock and oxidation compared to other non-oxide structural ceramics, which makes them attractive for aerospace applications [4][5][6]. However, strong covalent bond imposes low values of self-diffusion within ZrB 2 structure.…”

Section: Introductionmentioning

confidence: 99%

Effects of Y2O3 on microstructure and mechanical properties of ZrB2–SiC ceramics

Zhang

Han

et al. 2008

Journal of Alloys and Compounds

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Section: Introductionmentioning

confidence: 99%

Effects of Y2O3 on microstructure and mechanical properties of ZrB2–SiC ceramics

Zhang

Han

et al. 2008

Journal of Alloys and Compounds

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“…This study was conducted on bars cut from a series of hot pressed billets; variations due to processing differences were not identified. However, the variation in results observed herein are similar to those reported in the literature 11,43,45,80 . Viscous flow of the glass phase is likely to be more important as gas velocities and temperatures rise.…”

Section: Limitationssupporting

confidence: 91%

Oxidation Behavior of Zirconium Diboride Silicone Carbide Based Materials at Ultra-High Temperatures

Shugart

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ZrB 2 -SiC is of high interest for Thermal Protection Systems (TPS) for future hypersonic vehicles. Both ZrB 2 and its oxidation product, ZrO 2 , possess high melting temperatures (T m =3245°C and 2715°C respectively) needed for this application. SiC is added to improve the oxidation resistance. However, the oxidation resistance of ZrB 2 -SiC at ultra-high temperatures is poor and the oxidation mechanisms are not well understood. The aim of this work was to perform a quantitative study of the oxidation behavior in order to improve life prediction.The oxidation behavior of ZrB 2 -30 vol% SiC was studied using two oxidation procedures. A box furnace was used to oxidize specimens for times between 30 seconds and 100 hours at temperatures of 1300°-1550°C in stagnant air. For ultra-high temperature testing, a resistive heating system was designed and built, which allowed oxidation at temperatures of 1300°-1800°C for times between 5 and 70 minutes in controlled oxygen atmospheres. Oxidation was quantified by measuring mass change and oxidation product layer thicknesses. A combination of scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectrometry, and time of flight secondary ion mass spectrometry was used to characterize the oxidation products.Two oxidation regimes were identified; 1) low temperature oxidation below 1627°C and 2) high temperature oxidation at and above 1627°C. Low temperature oxidation exhibited a twolayer oxide, which consisted of a borosilicate glass layer above a ZrO 2 +C layer. Key findings indicate that oxygen transport in both zirconia and borosilicate glass must be considered in modeling the low temperature oxidation behavior of ZrB 2 -30 vol% SiC. In addition composition and thickness variations of the borosilicate glass layer must also be considered. ivThe transition between the low and high temperature oxidation regimes is attributed to a change in the thermodynamically favored oxidation products, considering a locally SiC-rich microstructure. High temperature oxidation, T≥ 1627°C, resulted in formation of three oxidation product layers. A borosilicate glass layer was found above a layer with ZrO 2 and borosilicate glass. Beneath these was a porous layer of ZrB 2 resulting from SiC depletion due to active oxidation to SiO(g). Key findings indicate that the oxidation rate is much more rapid in this oxidation regime, that the SiC depletion layer growth is best explained by parabolic gas phase diffusion in the porous layer, and again, oxygen transport in both zirconia and borosilicate glass must be considered in modeling the high temperature oxidation behavior of ZrB 2 -30 vol% SiC.This work provided a quantitative analysis of the oxidation kinetics of ZrB 2 -30 vol% SiC.The thermodynamic and kinetic analyses of the two distinct oxidation regimes of ZrB 2 -30 vol% SiC enable improved life prediction.v

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“…However, higher gas velocities accelerated recession of the materials and led the authors to the conclusion that these UHTCs are not appropriate for long-term use in aeropropulsion applications [100].…”

Section: ( 18 )mentioning

confidence: 99%

Creep and Oxidation of Hafnium Diboride Based Ultra High Temperature Ceramics at 1500C

DeGregoria¹

2015

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Ultra high temperature ceramics (UHTCs) are leading candidates for aerospace structural applications in high temperature environments, including the leading edges of hypersonic aircraft and thermal protection systems for atmospheric re-entry vehicles.Before UHTCs can be used in such applications, their structural integrity and environmental durability must be assured, which requires a thorough understanding and characterization of their creep and oxidation behavior at relevant service temperatures.Creep, or the progressive, time-dependent deformation of material under constant load, is a critical criterion in these applications, but not much is known with regard to UHTCs or whether there are interactions with oxidation processes. Thus, a facility for high temperature, mechanical testing in air was augmented for testing in argon. Then, the compressive creep of a popular UHTC, HfB 2 , was examined at 1500°C in argon and compared to results in air. HfB 2 specimens with 0, 10, 20, and 30% additions of SiC were tested, which enabled assessments of the effects of grain size and SiC content on creep behavior. Boundary mechanisms accommodated by diffusion through grains dominated the creep rates. The results also suggest that SiC formed a network of pointto-point contacts and increased creep resistance.A unique stressed oxidation test was devised in order to further investigate the interaction of creep and oxidation. The results indicate that up to 75 MPa of compressive stress, models of creep and oxidation in HfB 2 -based UHTCs can be decoupled.

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Oxidation of Ultrahigh Temperature Ceramics in Water Vapor

Cited by 59 publications

References 7 publications

Effects of Y2O3 on microstructure and mechanical properties of ZrB2–SiC ceramics

Effects of Y2O3 on microstructure and mechanical properties of ZrB2–SiC ceramics

Oxidation Behavior of Zirconium Diboride Silicone Carbide Based Materials at Ultra-High Temperatures

Creep and Oxidation of Hafnium Diboride Based Ultra High Temperature Ceramics at 1500C

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