Spark plasma sintering (SPS) densified U3Si2 pellets: Microstructure control and enhanced mechanical and oxidation properties

JOURNAL OF ALLOYS AND COMPOUNDS

卷:825

Article

Gong, Bowen¹  Yao, Tiankai^1,2  Lei, Penghui¹  Harp, Jason³  Nelson, Andrew T.³  Lian, Jie¹ 

[1] Rensselaer Polytech Inst, Dept Mech Aerosp & Nucl Engn, Troy, NY 12180 USA

[2] Idaho Natl Lab, Idaho Falls, ID 83415 USA

[3] Oak Ridge Natl Lab, POB 2009, Oak Ridge, TN 37830 USA

关键词: U3Si2;    Accident tolerant fuel;    Spark plasma sintering;    Oxidation;    Strain engineering;   

DOI  :  10.1016/j.jallcom.2020.154022

来源: Elsevier

【 摘 要 】

Dense U3Si2 pellets with controlled grain structure and enhanced thermal-mechanical and oxidation properties are synthesized with spark plasma sintering (SPS). Microstructure and phase composition of the SPS densified pellets are characterized systematically using SEM, EDS, and XRD. Thermal-mechanical properties and oxidation behavior of the sintered silicide fuel pellets are analyzed by laser flash, indentation, and dynamic thermogravimetric analysis. Dense U3Si2 pellets are consolidated by combining high energy ball milling and rapid sintering by SPS, and the microstructure structures are controlled from micron-sized (similar to 5.7 mu m grain size) for conventional silicide to a nanocrystalline matrix with an average grain size of similar to 280 nm. A dominant phase of distorted U3Si2 was identified with lattice expansion due to residual thermal stress upon SPS consolidation and rapid cooling processes. Both micron-sized and nanosized pellets show exceptional thermal transport properties, consistent with monolithic silicides reported in literature. The SPS-densified pellets possess simultaneously high hardness and fracture toughness. The SPS-densified silicide pellets also demonstrate exceptional oxidation performance with extended onset oxidation temperature above 500 degrees C and reduced oxidation kinetics, particularly for nano-sized pellets. A strong strain effect was proposed in which compressive stress in nano-sized pellets enhances the oxidation resistance of silicide fuels, as evidenced by the degradation of oxidation performance upon strain relaxation by isothermal annealing. The correlation among the sintering process microstructure control - physical properties and fuel behavior is established. A new concept of strain engineering is proposed further properties optimization, enabling the development of potential oxidation and corrosion-resistant silicides with extended performance, the key technological challenge of U3Si2 as the leading concept of accident tolerant fuels. (C) 2020 Elsevier B.V. All rights reserved.

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