Nano-Scale Microstructure Damage by Neutron Irradiations in a Novel Boron-11 Enriched TiB₂ Ultra-High Temperature Ceramic
Abstract
Ultra-high temperature transition-metal ceramics are potential candidates for fusion reactor structural/plasma-facing components. We reveal the irradiation damage microstructural phenomena in Boron-11 enriched titanium diboride (TiB2) using mixed-spectrum neutron irradiations, combined with state-of-art characterization using transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Irradiations were performed using High Flux Isotope Reactor at ∼220 and 620 °C up to 2.4 x 1025 n.m−2 (E > 0.1 MeV). Total dose including contribution from residual Boron-10 (10B) transmutation recoils, was ∼4.2 displacements per atom. TiB2 is susceptible to irradiation damage in terms of dislocation loop formation, cavities and anisotropic lattice parameter swelling induced micro-cracking. At both 220 and 620 °C, TEM revealed dislocation loops on basal and prism planes, with nearly two orders of magnitude higher number density of prism-plane loops. HRTEM, electron diffraction and relrod imaging revealed additional defects on {101̅0} prism planes, identified as faulted dislocation loops. High defect cluster density on prism planes explains anisotropic a-lattice parameter swelling of TiB2 reported in literature which caused grain boundary micro-cracking, the extent of which decreased with increasing irradiation temperature. Dominance of irradiation-induced defect clusters on prism planes in TiB2 is different than typical hexagonal ceramics where dislocation loops predominantly form on basal planes causing c-lattice parameter swelling, thereby revealing a potential role of c/a ratio on defect formation/aggregation. Helium generation and temperature rise from residual 10B transmutation caused matrix and grain boundary cavities for the irradiation at 620 °C. The study additionally signifies isotopic enrichment as a viable approach to produce transition-metal diborides for potential nuclear structural applications.
Recommended Citation
A. Bhattacharya et al., "Nano-Scale Microstructure Damage by Neutron Irradiations in a Novel Boron-11 Enriched TiB₂ Ultra-High Temperature Ceramic," Acta Materialia, vol. 165, pp. 26 - 39, Acta Materialia Inc, Feb 2019.
The definitive version is available at https://doi.org/10.1016/j.actamat.2018.11.030
Department(s)
Materials Science and Engineering
Keywords and Phrases
CO2 hydrogenation; Cu-ZnO based catalyst; Dimethyl ether (DME); Stability
International Standard Serial Number (ISSN)
1359-6454
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2019 Acta Materialia Inc, All rights reserved.
Publication Date
01 Feb 2019
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Comments
The study was supported by the Office of Fusion Energy Sciences, US DOE and IMR Tohoku University under contract DE-AC05-00OR22725 and NFE-13-04416 with UT-Battelle, LLC, respectively.