Structural integrity and characteristics at lattice and nanometre levels of ZrN polycrystalline irradiated by 4 MeV Au ions

We report an as-hot-pressed zirconium nitride polycrystalline with its primary crystal structure maintained no change but lattice defects and features were introduced at nanometre-scale after being irradiated by 4 MeV Au 2+ with a total fluence of 5 × 10 16 /cm 2 . The variation of grey-level seen in backscattered electron images and electron backscattered diffraction maps directly evidenced the structure integrity of the polycrystalline ZrN is well maintained with no crystal structure change of ZrN. The irradiation depth had no relevance to crystal orientation, and Au deposition peaked at a depth of ∼0.58 μm with a near-Gaussian distribution. Within a depth < 0.58 μm, long dislocation lines were developed with a Burgers vector of [01¯] b /2 and density 3.2 × 10 14 1/m 2 ; beyond this depth, dislocation loops were formed with much higher density. In the ionization zone, cubic ZrO 2 crystallites precipitated in a size of ∼5 nm. The irradiation damage processes are discussed based on the observed features

Structural integrity and damage of ZrB₂ ceramics after 4 MeV Au ions irradiation

Ultra-high temperature ceramics have been considered as good candidates for plasma facing materials due to their combination of high melting point, high strength and hardness, high thermal conductivity as well as good chemical inertness. In this study, zirconium diboride has been chosen to investigate its irradiation damage behavior. Irradiated by 4 MeV Au2+ with a total fluence of 2.5 × 1016/cm2, zirconium diboride ceramic shows substantial resilience to irradiation-induced damage with its structural integrity well maintained but mild damage at lattice level. Grazing incident X-ray diffraction evidences no change of the hexagonal structure in the irradiated region but its lattice parameter a increased and c decreased, giving a volume shrinkage of ∼0.46%. Density functional theory calculation shows that such lattice shrinkage corresponds to a non-stoichiometric compound as ZrB1.97. Electron energy-loss spectroscopy in a transmission electron microscope revealed an increase of valence electrons in zirconium, suggesting boron vacancies were indeed developed by the irradiation. Along the irradiation depth, long dislocations were observed inside top layer with a depth of ∼750 nm where the implanted Au ions reached the peak concentration. Underneath the top layer, a high density of Frank dislocations is formed by the cascade collision down to a depth of 1150 nm. All the features show the potential of ZrB2 to be used as structural material in nuclear system

High-entropy silicide ceramics developed from (TiZrNbMoW)Si2 formulation doped with aluminum

We report a success in synthesizing high entropy silicides (HES) compounds and manufacturing well-densified HES ceramics through spark plasma sintering. For a designed chemical formula as (Ti0.2Zr0.2Nb0.2Mo0.2W0.2)Si2, the as-synthesized HES showed a formula as (Ti0.22Zr0.06Nb0.29Mo0.22W0.21)Si2 with zirconium partially oxidized into zirconia. Doping with aluminum resulted in a HES with the same composition, promoted formation of ZrSi2 and Al2O3. XRD analysis of as-synthesized HES is well supported by the calculated diffraction data based on a 2 × 3x1 supercell with HCP crystal structure and experimental chemical composition. The cations in this HES crystal structure can occupy their positions randomly with little change of its lattice parameters and formation enthalpy