Interface Design for Oxidation‐Resistant Ceramic Composites

Kerans, Ronald J.; Hay, Randall S.; Parthasarathy, Triplicane A.; Cinibulk, Michael K.

doi:10.1111/j.1151-2916.2002.tb00505.x

Cited by 273 publications

(149 citation statements)

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“…It is widely accepted that in order to avoid brittle fracture behavior in CMCs and improve the damage tolerance, a weak fiber/matrix interface is needed, which serves to deflect matrix cracks and to allow subsequent fiber pullout [10][11][12]. It has been demonstrated that similar crack-deflecting behavior can also be achieved by means of a finely distributed porosity in the matrix instead of a separate interface between matrix and fibers [13].…”

Section: Introductionmentioning

confidence: 96%

“…An extensive review of the research on oxide coatings for oxide and non-oxide composites has been given by Kerans et al [12]. The development of oxide-oxide composites that rely on a weak fiber/matrix interface for crack deflection prompted research into oxidation resistant fiber coatings that are chemically stable with the composite constituents.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Steam Environment on Creep Behavior of Nextel™610/Monazite/Alumina Composite at 1,100°C

et al. 2009

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The tensile creep behavior of a N610™/LaPO 4 /Al 2 O 3 composite was investigated at 1,100°C in laboratory air and in steam. The composite consists of a porous alumina matrix reinforced with Nextel 610 fibers woven in an eight-harness satin weave fabric and coated with monazite. The tensile stress-strain behavior was investigated and the tensile properties measured at 1,100°C. The addition of monazite coating resulted in~33% improvement in ultimate tensile strength (UTS) at 1,100°C. Tensile creep behavior was examined for creep stresses in the 32-72 MPa range. Primary and secondary creep regimes were observed in all tests. Minimum creep rate was reached in all tests. In air, creep strains remained below 0.8% and creep strain rates approached 2×10 −8 s −1 . Creep run-out defined as 100 h at creep stress was achieved in all tests conducted in air. The presence of steam accelerated creep rates and significantly reduced creep lifetimes. In steam, creep strain reached 2.25%, and creep strain rate approached 2.6×10 −6 s −1 . In steam, creep run-out was not achieved. The retained strength and modulus of all specimens that achieved run-out were characterized. Comparison with results obtained for N610™/Al 2 O 3 (control) specimens revealed that the use of the monazite coating resulted in considerable improvement in creep resistance at 1,100°C both in air and in steam. Composite microstructure, as well as damage and failure mechanisms were investigated.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Effects of Steam Environment on Creep Behavior of Nextel™610/Monazite/Alumina Composite at 1,100°C

et al. 2009

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“…3) the atomic (elemental), structural, and phase composition of the ceramic material must be chosen so as to create obstacles that deflect cracks; 4) the geometric parameters of the barrier (thickness, ratio of the barrier thickness to the thickness of the silicon carbide layer, the roughness of the outer surface of the inner pyrocarbon layer (substrate) and surface of the barrier, and others), which should make possible internal creep (within the barrier) of cracks in the tangential direction; and 5) the barrier should be thermochemically stable separately with respect to the fission products and in combination with the silicon carbide and pyrocarbon layers, the absorbing ceramic structures must effectively bind carbon monoxide and solid fission products into stable compounds under the operating conditions of microfuel elements; for example, in the process of developing composite materials with a ceramic matrix, composites with a ceramic matrix and fibers, and ceramic composites with a continuous fiber [24], diverse fibers and coatings on them and the matrix are gone through; a large number of variants of composites for analysis of their properties and comparing with respect to the areas and conditions of their application is optimized using at least as many models [25].…”

Section: Of Htgr Fuel Elementsmentioning

confidence: 99%

Formation of multifunctional barriers to increase the radiochemical resistance of the protective coatings of HTGR fuel elements

Kurbakov

2009

At Energy

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The radiation-size changes of pyrocarbon protective coatings on HTGR microfuel elements are analyzed. It is shown that there is a relationship between the microstructural inner pyrolytic layers and the formation of cracks in these layers as the irradiation dose accumulates. The effect of cracks in the inner pyrocarbon layers on the damage to the silicon carbide layer is examined. It is determined that incorporating into the inner pyrocarbon layer or forming on the inner pyrocarbon-silicon carbide interface compositions, for example, silicon carbide-carbon, Ti 3 SiC 2 , ZrC, TiC, and nitrides of Zr, Ti, and Al creates an obstacle to interior cracks, increasing the radiation-chemical resistance of the carbide layer and the microfuel as a whole.The structure of the microfuel of high-temperature gas-cooled reactors has evolved from particles with a single-layer protective coating consisting of pyrocarbon with a laminar structure through a bilayer pyrocarbon coating with different density to a fuel microsphere with three layers made of, respectively, inner high-density isotropic pyrocarbon and silicon carbide and an outer layer of high-density isotropic pyrocarbon ( Fig. 1) [1].The specifications for the microsphere fuel for HTGR take account of the following essential characteristics: thickness, density, anisotropy of the pyrocarbon coating, contamination of the coatings by fissile materials, defects in the silicon carbide layer, and others [2-6].The operational parameters (temperature, degree of fuel burnup, fluence of fast neutrons, and others) which have been obtained on the experimental stand satisfied the technical requirements for uranium dioxide microspherical fuel based on multilayer coatings (see Fig. 1, position I) and even exceeded the requirements in individual cases (see Fig. 1, positions II and III).In connection with new problems arising in the development of fourth-generation nuclear-energy systems, the requirements for the operational parameters (nuclear fuel burnup, irradiation temperature, hast-neutron fluence, energy release from a fuel microsphere, and others) are increasing substantially. Probably the biggest problem will be due to the realization of deep burnup of fuel at high irradiation temperature -up to 20% h.a. and higher than 1100°C under stationary operating conditions of a very-high-temperature gas-cooled reactor (VHTR, Japan).One of the variants under consideration variant for improving the performance of multilayer coatings is replacing the silicon carbide load-bearing layer by a zirconium carbide layer. However, such a replacement will make it necessary to solve a multitude of materials-engineering problems, develop methods for monitoring the properties of carbide-zirconium coatings and rejecting microfuel based on them, and determine the capability of zirconium carbide to confine solid fission products at elevated irradiation temperatures taking account of the high neutron fluence for VHTR and GFR (see Fig. 1, positions IV, V).Laboratory investigations performed in the USA on micros...

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“…Hier gelten die sog. [10]. Problematisch ist auch hier die thermische Langzeitstabilität der Mikrostruktur.…”

Section: Faserbeschichtungenunclassified

Faserverstärkte oxidkeramische Werkstoffe

Schmücker

2007

Materialwissenschaft Werkst

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Oxide ceramics display excellent thermal and chemical stability up to high temperatures. A suitable way to overcome the inherent brittleness of oxide ceramics is the reinforcement with oxide fibers. Although both constituents, fibers and matrices are brittle, the composites display quasi-ductile deformation behavior, due to mechanisms such as crack deflection, crack bridging or fiber pull-out. A premise for these mechanisms to work is the relatively weak bonding between fibers and the matrix. To achieve a weak fiber/matrix bonding either suitable fiber coatings are employed or, in an alternative approach, highly porous matrices are used. WHIPOX, developed at DLR is a ceramic matrix composite belonging to the porous matrix group. These materials have a high potential for thermal protection systems and liners in gas turbine engines and beyond.

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Interface Design for Oxidation‐Resistant Ceramic Composites

Cited by 273 publications

References 294 publications

Effects of Steam Environment on Creep Behavior of Nextel™610/Monazite/Alumina Composite at 1,100°C

Effects of Steam Environment on Creep Behavior of Nextel™610/Monazite/Alumina Composite at 1,100°C

Formation of multifunctional barriers to increase the radiochemical resistance of the protective coatings of HTGR fuel elements

Faserverstärkte oxidkeramische Werkstoffe

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