HRXRD study of the theoretical densities of novel reactive sintered boride candidate neutron shielding materials

Abstract

Reactive Sintered Borides (RSBs) are novel borocarbide materials derived from FeCr-based cemented tungsten (FeCr-cWCs) show considerable promise as compact radiation armour for proposed spherical tokamak (Humphry-Baker, 2007 [1], [2], [3], [4], [5]. Six candidate compositions (four RSBs, two cWCs) were evaluated by high-resolution X-ray diffraction (XRD), inductively coupled plasma (ICP), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) to determine the atomic composition, phase presence, and theoretical density.RSB compositions were evaluated with initial boron contents equivalent to 25 at%30 at%. All RSB compositions showed delamination and carbon enrichment in the bulk relative to the surface, consistent with non-optimal binder removal and insufficient sintering time. Phase abundance within RSBs derived from powder XRD was dominated by iron tungsten borides (FeWB/FeW2B2), tungsten borides (W2B5/WB) and iron borides. The most optimal RSB composition (B5T522W) with respect to physical properties and highest ρ/ρtheo had ρtheo = 12.59 ± 0.01 g cm−3 for ρ/ρtheo = 99.3% and had the weigh-in and post-sintered W: B: Fe abundance closest to 1: 1: 1. This work indicates that despite their novelty, RSB materials can be optimized and in principle be processed using existing cWC processing routes. Keywords: Radiation shielding, Nuclear fusion, Tungsten borides, Cemented carbides, XRD, Powder metallurgy