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Understanding microstructural and strain evolutions induced by noble gas production in the nuclear fuel matrix or plasma-facing materials is crucial for designing next generation nuclear reactors, as they are responsible for volumetric swelling and catastrophic failure. We describe a multimodal approach combining synchrotron-based nanoscale X-ray imaging techniques with atomic-scale electron microscopy techniques for mapping chemical composition, morphology and lattice distortion in a single crystal W induced by Kr irradiation. We report that Kr-irradiated single crystal W undergoes surface deformation, forming Kr containing cavities. Furthermore, positive strain fields are observed in Kr-irradiated regions, which lead to compression of underlying W matrix.

We report the formation of tetragonal gas bubble superlattice in bulk molybdenum under helium ion implantation at 573 K. The transmission electron microscopy study shows that the helium bubble lattice constant measured from the in-plane d-spacing is ~4.5 nm, while it is ~3.9 nm from the out-of-plane measurement. The results of synchrotron-based small-angle x-ray scattering agree well with the transmission electron microscopy results in terms of the measurement of bubble lattice constant and bubble size. The coupling of transmission electron microscopy and synchrotron high-energy X-ray scattering provides an effective approach to study defect superlattices in irradiated materials.

This work utilizes electron energy loss spectroscopy (EELS) to identify oxidation state of alloying elements in Ni-based alloys after exposure to molten chloride salt systems. Pure Ni and Ni-20Cr model alloy were corroded in molten ZnCl2 and KCl-MgCl2 under argon atmosphere at various temperatures. Oxidation states of Cr (Cr3+) and Ni (Ni2+) in the molten salt after corrosion were determined by monitoring changes in the L2,3 edges of corresponding EELS spectra. Oxidation state mapping technique using principal component analysis and multiple linear least squares fitting in HyperSpy Python package was developed.

The mechanical properties of Y2Ti2O7 ceramics have been systematically characterized. Y2Ti2O7 shows higher hardness (12.1 GPa) than Y2O3 and TiO2. The Young’s modulus of Y2Ti2O7 (262 GPa) is close to that of TiO2 and 50% higher than that of Y2O3. The fracture toughness (1.9 MPa m1/2) and bending strength (206 MPa) are comparable with those of Y2O3 but half those of TiO2. The indentation size effect on the hardness in nanoindentation tests is discussed based on the Nix–Gao model.

Predominantly single-phase Hf(2)[Al(Si)(4)]C(5) ceramic hits been fabricated by an Ill Situ reaction/hot-pressing method using Al. Si and graphite its starting materials Hf(2)[Al(Si)](4)C(5) Shows comparable mechanical properties to Zr(2)[Al(Si)](4)C(5), and lower hardness and stiffness but higher strength and toughness than HfC The stiffness decreases slowly with temperature and at 1600 degrees C it remains 83% of that at ambient temperature Compared to Zr(2)[Al(Si)](4)C(5) and HfC, however, Hf(2)[Al(Si)(4)C(5) exhibits it relatively higher coefficient of thermal expansion,. all intermediate specific heat capacity and it lower thermal conductivity (C) 2009 Acta Materialia Inc Published by Elsevier Ltd. All rights reserved

The temperature dependence of internal friction, stiffness and strength of Zr-Al(Si)-C ceramics was studied. For glass-free Zr-Al(Si)-C ceramics, the internal friction curve followed an exponential-like background. For liquid-phase-sintered Zr(3)Al(3)C(5), an internal peak present at 1590 K revealed the grain-boundary sliding due to wetting of glass phase at grain boundaries and triple junctions. Zr-Al(Si)-C ceramics exhibited high degrees of stiffness and strength at high temperatures up to 1600 and 1400 degrees C, respectively, which render them good high-temperature structural materials. (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A new copper matrix composite reinforced with Zr(2)Al(3)C(4) particulates was successfully fabricated by powder metallurgy method. In the whole reinforcing range, Cu/Zr(2)Al(3)C(4) Composite possesses comparable electrical conductivity and better mechanical properties than those of Cu/graphite composite, which was widely accepted as the electro-contacting material. The high conductivity was attributed to the formation of a continuous copper network in the composite, while the high strength and modulus of Zr(2)Al(3)C(4) ceramic led to a notable improvement in the mechanical properties of the composite. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The oxidation behavior of Zr 2 Al 3 C 4 at 1600 and 1750 °C was studied by means of induction heating. The oxidation kinetics follows a linear law and the interfacial reaction between Zr 2 Al 3 C 4 and O 2 is the rate-limiting step for scale growth. The microstructure of oxide scales gradually changes from intragranular (small ZrO 2 particles embedded in large Al 2 O 3 grains) to an interpenetrating dual-phase form as the exposure time increases, which is ascribed to the temperature decay of the top scale surface with scale growth.

Two new ternary aluminum carbides, Hf3Al4C6 and Hf2Al4C5, were identified and their crystal structure was determined by a combination of X-ray diffraction, Z-contrast scanning transmission electron microscopy and density-function calculations. Theoretical second-order elastic constants, bulk modulus, shear modulus and Young’s modulus of Hf3Al4C6 and Hf2Al4C5, as well as Hf3Al3C5, Hf2Al3C4, HfC and Al4C3, were calculated and compared. These new carbides show promisingly high elastic stiffness.