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The sintering of zirconium hydride (ZrH 2- x) without hydrogen atmosphere faces the challenge of thermal dehydrogenation problem, which is overcome by the high-pressure spark plasma sintering (HPSPS) technique in this study. The application of high pressure remarkably reduces the initial densification temperature and effectively restrains the thermal dehydrogenation of ZrH 2- x in SPS. Under 500 MPa loading, ε-ZrH 1.72 monolith with high densification (96.62 %) and high hydrogen density (6.04 × 10 22 atoms H/cm3) is sintered at a relatively low temperature of 700 °C for only 5 min. Meanwhile, the grain growth of ZrH 2- x is very limited. The Young's modulus and hardness of the sintered ε-ZrH 1.72 are 58.68 GPa and 2.61 GPa respectively. Compared with the directly hydrided ε-ZrH 2- x , the sintered ε-ZrH 1.72 has a more uniform hardness distribution and improved fracture toughness of 3.19 MPa m1/2. This study provides a valuable reference for the sintering of other easily decomposable materials. [ABSTRACT FROM AUTHOR]

Two strategies have been extensively employed to develop advanced accident tolerant fuels (ATF): improving thermal conductivity and producing large grain sized pellets. However, there are few reports on the simultaneous utilization of both strategies. In this work, we fabricated Mo–Cr alloy reinforced UO 2 (UMC) composite pellet with both high thermal conductivity and large grain size by a simple in-situ alloying method for the first time. The average grain size of UO 2 increased from 6 μm to 113 μm. Thermal conductivity of the UMC pellet (with 2 vol% Mo) at 1200 °C increased by 36.46% compared with pure UO 2. The increase rate of thermal conductivity per 1 vol% dopant reached about 18%. The Mo–Cr alloy formed continuous micro-cell layer around UO 2 particles. Such continuous micro-cell Mo–Cr alloy layer and increase of UO 2 grain size both helped improve the thermal conductivity of UMC composite pellets. Thermal expansion coefficient of the UMC under the operating temperature decreased by 11.90% compared with pure UO 2. The oxidation resistance of the UMC pellet under high temperature steam was also improved. This work provides a new strategy towards fabricating ATF with both high thermal conductivity and large grain size. [ABSTRACT FROM AUTHOR]

SiC matrix microencapsulated composites with particle-free buffer (PB) layer were produced by spark plasma sintering for the first time. Microstructure and thermal physical performance of the composites from room temperature to 1900 °C were investigated. Dense composites with rational layout of tristructural isotropic (TRISO) particles and PB layer were obtained. The TRISO particles in the composites kept intact spherical shell structure. Thermal physical properties of the composites approached those of the SiC materials. The composites with high thermal conductivity and low coefficient of thermal expansion were suitable for nuclear applications. The effect of oxide additives on comprehensive performance of the composites was reappraised. Dissolution and recrystallization of SiC in the eutectic liquid phase revealed a new high temperature failure mechanism for the composites. [ABSTRACT FROM AUTHOR]

Abstract: Uranium dioxide films were deposited on Si (111) substrates by dc magnetron sputtering method at different sputtering parameters. The structure, morphology and chemical state of the films were studied by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy. Influences of film thickness on the microstructure and optical properties were investigated. Experimental results show that the film crystallites are preferentially oriented with the (111) planes. The average grain size increases with increasing film thickness. AFM images show that the root mean square roughness of the films is between 1.2nm and 2.1nm. Optical constants (refractive index, extinction coefficient) of the films in the wavelength range of 350–1000nm are obtained by ellipsometric spectroscopy. The result shows that the refractive index decreases with the increasing film thickness, while extinction coefficient increases with the film thickness. [Copyright &y& Elsevier]