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A key consideration for the successful operation of hybrid energy systems will be the environmental stability of materials used for their construction, particularly when experiencing service environments containing water vapor at high temperatures. Here, we report results from the characterization of siliconized silicon carbide (Si‐SiC) prepared via binder jet additive manufacturing and reactive silicon melt infiltration after being exposed to environments representative of those in solid oxide fuel cell (SOFC) anodes, and to exhaust gases inside a microturbine operating on natural gas. In both cases, it was found that oxide scales formed on the surface and that these scales were dense, continuous, and well‐bonded to the substrates, although there was evidence of transverse and longitudinal cracking most likely as a result of mismatches in the thermal expansion of the scale and the substrate. Measured values of the thickness of the oxide scale were compared to those predicted by parabolic oxidation kinetics of silicon, but the potential effects of silica volatilization induced by water vapor, and silica reduction when exposed to hydrogen are discussed. The overall results showed that the oxide scale is expected to be protective under the conditions of hybrid power generation systems. [ABSTRACT FROM AUTHOR]

SiC‐fiber–reinforced SiC matrix composite cladding for light water reactor fuel elements must withstand high‐temperature steam oxidation in a loss‐of‐coolant accident scenario (LOCA). Current composite designs include an outer monolithic SiC layer, in part, to increase steam oxidation resistance. However, it is not clear how such a structure would behave under high‐temperature steam in the case when the monolithic layer cracks and carbon interphases and SiC fibers are exposed to the environment. To fill this knowledge gap, stress‐rupture tests of prototypic SiC composite cladding at 1000°C under steam and inert environments were conducted. The applied stress was ∼120 MPa, which was beyond the initial cracking stress. The failure lifetime under steam was 400–1300 s, while 75% of the composite specimens did not fail after 3 h of total exposure under inert gases. Microstructural observations suggest that steam oxidation activated slow crack growth in the fibers, which led to failure of the composite. The results from this study suggest that stress rupture in steam environments could be a limiting factor of the cladding under reactor LOCA conditions. [ABSTRACT FROM AUTHOR]

Abstract: An interlaboratory round robin study was conducted on the tensile strength of SiC‐SiC ceramic matrix composite (CMC) tubular test specimens at room temperature with the objective of expanding the database of mechanical properties of nuclear grade SiC‐SiC and establishing the precision and bias statement for standard test method ASTM C1773. The mechanical properties statistics from the round robin study and the precision statistics and precision statement are presented herein. The data show reasonable consistency across the laboratories, indicating that the current C1773‐13 ASTM standard is adequate for testing ceramic fiber reinforced ceramic matrix composite tubular test specimen. It was found that the distribution of ultimate tensile strength data was best described with a two‐parameter Weibull distribution, while a lognormal distribution provided a good description of the distribution of proportional limit stress data. [ABSTRACT FROM AUTHOR]

The through thickness (interlaminar) shear strength and trans-thickness tensile strength of three different nuclear-grade SiC/SiC composites were evaluated at room temperature by the double-notched shear and diametral compression tests, respectively. With increasing densification of the interlaminar matrix region, a transition in failure locations from interlayer to intrafiber bundle was observed, along with significant increases in the value of the interlaminar shear strength. Under trans-thickness tensile loading, cracks were found to propagate easily in the unidirectional composite. The 2D woven composite had a higher trans-thickness tensile strength (38 MPa) because the failure mode involved debonding, fiber pull-out and fiber failure. [ABSTRACT FROM AUTHOR]

In waste heat recovery applications, thermoelectric (TE) generators are subjected to thermal gradients and thermal transients, creating mechanical stresses in the TE legs. Such stresses are functions of the elastic moduli of the TE material. For SnTe1±x matrices (where x = 0.0 or 0.016) composite specimens with 0-4 vol% SiC nanoparticle (SiCNP) additions, the elastic moduli (Young's modulus, shear modulus, and Poisson's ratio) were measured by resonant ultrasound spectroscopy from room temperature (RT) to 663 K. The effects of matrix composition and the SiCNP additions on the RT intercepts and the slopes of the elastic modulus as a function of temperature are also discussed. [ABSTRACT FROM AUTHOR]

Brazilian disk test is here analyzed as a test method to determine the strength of joined ceramics. The test specimen consisted of two silicon carbide half-disks diametrically bonded with a brittle adhesive (Araldite AV119™). Several tests were performed with different angles of the adhesive layer with respect to the diametral line of loading. An elastic finite element analysis is used to determine the maximum shear stress and the normal compressive stress within the joint. Assuming a failure criterion based on a shear stress condition, this procedure allows evaluating the shear strength of the epoxy adhesive. [ABSTRACT FROM AUTHOR]

The article presents a study which evaluated the mechanical properties of a nuclear-grade silicon carbide (SiC)/SiC composite. It is stated that such ceramics are being considered as a candidate control rod material for a very-high temperature gas-cooled reactor. The materials used for study were satin-woven or biaxially braided Hi-Nicalon Type-S fiber reinforced chemical-vapor-infiltrated SiC matrix composites. The findings showed a disparity between excellent axial and off-axial tensile fracture behaviors for satin-woven and braided composites.