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a b s t r a c tTwo 5 vol% Ni/Al 2 O 3 composites with the difference in Al 2 O 3 grain size were fabricated by pulsed electric current sintering technique to investigate the influence of Al 2 O 3 grain size on oxidation behavior of the composites. Average Al 2 O 3 grain sizes of two fabricated composites were 1.1 m and 0.5 m after sintering. Oxidation tests were conducted at temperatures ranging from 1100 to 1350 • C for 1-48 h in air. A thin NiAl 2 O 4 layer was observed in exposed surface of samples after oxidation. An oxidized zone that consisted of Al 2 O 3 matrix and NiAl 2 O 4 grains was defined. Growth of the oxidized zone obeyed the parabolic law. Influences of Al 2 O 3 grain size on high-temperature oxidation of the composites were discussed.

Bending strength of 5 vol.% Ni/Al2O3 composites as a function of testing temperature is investigated at temperatures ranging from room temperature to 1200°C. Self‐healing performance at high temperatures of the composites is evaluated by conducting high‐temperature bending tests for as‐sintered, as‐cracked, and as‐healed specimens. Bending strength of as‐sintered specimens dramatically decreases from 995 MPa at room temperature to 205 MPa at 1200°C. Additionally, the plastic deformation of the as‐sintered specimens occurs when the testing temperature reaches to 1200°C. The values of high‐temperature bending strength of as‐healed specimens are comparable with those of as‐sintered specimens. Similar to that of as‐sintered specimens, bending strength of as‐healed specimens degrades when the testing temperature increases. Results of the present study indicate that the recovery of bending strength by the self‐healing function is able to achieve at temperatures as high as 1200°C. Unlike the mechanical behaviors at high temperatures of as‐sintered and as‐healed specimens, the bending strength of as‐cracked specimens slightly increases with the increase of testing temperature. This phenomenon is attributed to the effect of the self‐healing mechanism during high‐temperature bending tests.

Since the nuclear accident at Fukushima Daiichi Nuclear Power Station in 2011, a considerable number of studies have been conducted to develop accident tolerant fuel (ATF) claddings for safety enhancement of light water reactors. Among many potential ATF claddings, silicon carbide is one of the most promising candidates with many superior features suitable for nuclear applications. In spite of many potential benefits of SiC cladding, there are some concerns over the oxidation/corrosion resistance of the cladding, especially at extreme temperatures (up to 2000 °C) in severe accidents. However, the study of SiC steam oxidation in conventional test facilities in water vapor atmospheres at temperatures above 1600 °C is very challenging. In recent years, several efforts have been made to modify existing or to develop new advanced test facilities to perform material oxidation tests in steam environments typical of severe accident conditions. In this article, the authors outline the features of SiC oxidation/corrosion at high temperatures, as well as the developments of advanced test facilities in their laboratories, and, finally, give some of the current advances in understanding based on recent data obtained from those advanced test facilities.

Ni/(ZrO2+Al2O3) nanocomposites have excellent mechanical properties, as well as self-healing function. The powder preparation was conducted by drying slurry consisting of distilled water, Al2O3, 3 mol % Y2O3doped ZrO2and nickel nitrate. After reduction at 600°C in a stream of Ar-1% H2, the powder mixture was consolidated by pulsed electric current sintering (PECS) at 1300°C for 5 min under 50 MPa. Surface cracks were generated by Vickers indentation on the polished surface of the test samples. Ni/(YZ+Al2O3) shows 1200 MPa in bending strength and 6.1 MPa m1/2in facture toughness. Crack-healing and oxidation tests were conducted at temperature ranging from 1100 to 1300°C in air. As a result, crack-disappearance occurred slightly faster than that of Ni/Al2O3.