13 research outputs found
Thermal diffusivity recovery and defect annealing kinetics of self-ion implanted tungsten prob e d by insitu transient grating spectroscopy
Tungsten is a promising candidate material for plasma-facing armour components in future fusion reactors. A key concern is irradiation-induced degradation of its normally excellent thermal transport properties. In this comprehensive study, thermal diffusivity degradation in ion-implanted tungsten and its evolution from room temperature (RT) to 1073 K is considered. Five samples were exposed to 20 MeV self-ions at RT to achieve damage levels ranging from 3.2 x 10(-4) to 3.2 displacements per atom (dpa). Transient grating spectroscopy with insitu heating was then used to study thermal diffusivity evolution as a function of temperature. Using a kinetic theory model, an equivalent point defect density is estimated from the measured thermal diffusivity. The results showed a prominent recovery of thermal diffusivity between 450 K and 650 K, which coincides with the onset of mono-vacancy mobility. After 1073 K annealing samples with initial damage of 3.2 x 10(-3) dpa or less recover close to the pristine value of thermal diffusivity. For doses of 3.2 x 10(-2) dpa or higher, on the other hand, a residual reduction in thermal diffusivity remains even after 1073 K annealing. Transmission electron microscopy reveals that this is associated with extended, irradiation-induced dislocation structures that are retained after annealing. A sensitivity analysis shows that thermal diffusivity provides an efficient tool for assessing total defect content in tungsten up to 10 0 0 K. (c) 2022 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc.Peer reviewe
Non-contact, non-destructive mapping of thermal diffusivity and surface acoustic wave speed using transient grating spectroscopy
We present new developments of the laser-induced transient grating
spectroscopy (TGS) technique that enable the measurement of large area 2D maps
of thermal diffusivity and surface acoustic wave speed. Additional capabilities
include targeted measurements and the ability to accommodate samples with
increased surface roughness. These new capabilities are demonstrated by
recording large TGS maps of deuterium implanted tungsten, linear friction
welded aerospace alloys and high entropy alloys with a range of grain sizes.
The results illustrate the ability to view grain microstructure in elastically
anisotropic samples, and to detect anomalies in samples, for example due to
irradiation and previous measurements. They also point to the possibility of
using TGS to quantify grain size at the surface of polycrystalline materials.Comment: The following article has been submitted to Review of Scientific
Instruments. After it is published, it will be found at
https://aip.scitation.org/journal/rs
Bridging the gap to mesoscale radiation materials science with transient grating spectroscopy
Validating First-Principles Phonon Lifetimes via Inelastic Neutron Scattering
Phonon lifetimes are a key component of quasiparticle theories of transport,
yet first-principles lifetimes are rarely directly compared to inelastic
neutron scattering (INS) results. Existing comparisons show discrepancies even
at temperatures where perturbation theory is expected to be reliable. In this
work, we demonstrate that the reciprocal space voxel (-voxel), which is the
finite region in reciprocal space required in INS data analysis, must be
explicitly accounted for within theory in order to draw a meaningful
comparison. We demonstrate accurate predictions of peak widths of the
scattering function when accounting for the -voxel in CaF and ThO.
Passing this test implies high fidelity of the phonon interactions and the
approximations used to compute the Green's function, serving as critical
benchmark of theory, and indicating that other material properties should be
accurately predicted; which we demonstrate for thermal conductivity
Towards quantitative inference of nanoscale defects in irradiated metals and alloys
Quantifying the population of nanoscale defects that are formed in metals and
alloys exposed to extreme radiation environments remains a pressing challenge
in materials science. These defects both fundamentally alter material
properties and seed long-timescale performance degradation, which often limits
the lifespan of engineering systems. Unlike ceramic and semiconducting
materials, these defects in metals and alloys are not spectroscopically active,
forcing characterization to rely on indirect measurements from which the
distribution of nanoscale defects may be inferred. In this mini-review,
different experimental methodologies which have been employed for defect
inference are highlighted to capture the current state of the art. Future
directions in this area are proposed, which, by combining data streams from
multiple and complementary characterization methods in concert with multi-scale
modeling and simulation, will enable the ultimate goal of quantifying the full
spectrum of defects in irradiated metals and alloys.Comment: 10 pages, 2 figure
Irradiation-Induced Void Swelling In Pure Copper Characterized Using Transient Grating Spectroscopy
Advances in Actinide Thin Films: Synthesis, Properties, and Future Directions
Actinide-based compounds exhibit unique physics due to the presence of 5f electrons, and serve in many cases as important technological materials. Targeted thin film synthesis of actinide materials has been successful in generating high-purity specimens in which to study individual physical phenomena. These films have enabled the study of the unique electron configuration, strong mass renormalization, and nuclear decay in actinide metals and compounds. The growth of these films, as well as their thermophysical, magnetic, and topological properties, have been studied in a range of chemistries, albeit far fewer than most classes of thin film systems. This relative scarcity is the result of limited source material availability and safety constraints associated with the handling of radioactive materials. Here, we review recent work on the synthesis and characterization of actinide-based thin films in detail, describing both synthesis methods and modeling techniques for these materials. We review reports on pyrometallurgical, solution-based, and vapor deposition methods. We highlight the current state-of-the-art in order to construct a path forward to higher quality actinide thin films and heterostructure devices