Nano-scale microstructure damage by neutron irradiations in a novel Boron-11 enriched TiB2 ultra-high temperature ceramic. (15th February 2019)

• Record Type: Journal Article
• Authors: Bhattacharya, A.; Parish, C.M.; Koyanagi, T.; Petrie, C.M.; King, D.; Hilmas, G.; Fahrenholtz, W.G.; Zinkle, S.J.; Katoh, Y.
• Is Part Of: Acta materialia. Volume 165(2019)
• Page Start: 26
• Page End: 39
• Publication Date: 2019-02-15
• Subjects: Titanium diboride (TiB2) -- Implantation/irradiation -- Transmission electron microscopy -- High resolution TEM -- Ultra-high temperature ceramics; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2018.11.030
• Languages: English
• ISSNs: 1359-6454

Abstract

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 × 10 25 n.m −2 (E > 0.1 MeV). Total dose including contribution from residual Boron-10 ( 10 B) 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 { 10 1 ¯ 0 } 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 10 B 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. Graphical abstract: Image 1