Thermal diffusivity degradation and point defect density in self-ion implanted tungsten

Reza, Abdallah; Yu, Hongbing; Mizohata, Kenichiro; Hofmann, Felix

doi:10.1016/j.actamat.2020.03.034

Cited by 65 publications

(52 citation statements)

References 62 publications

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“…Unfortunately, the direct comparison with the 20 MeV implanted sample cannot be easily made, since the micro-beam Laue diffraction technique used to study the 20 MeV sample lacks the spatial resolution required to resolve nano-scale strain heterogeneity. Previous mechanical property [38] and thermal transport studies [39], performed on 20 MeV self-ion implanted tungsten as a function of damage dose, suggest that there is little difference in the damage microstructure of 0.07 dpa and 0.1 dpa damaged tungsten.…”

Section: Ion Implantationmentioning

confidence: 93%

Nanoscale lattice strains in self-ion implanted tungsten

Phillips

Das

et al. 2020

Acta Materialia

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Developing a comprehensive understanding of the modification of material properties by neutron irradiation is important for the design of future fission and fusion power reactors. Self-ion implantation is commonly used to mimic neutron irradiation damage, however an interesting question concerns the effect of ion energy on the resulting damage structures. The reduction in the thickness of the implanted layer as the implantation energy is reduced results in the significant quandary: Does one attempt to match the primary knock-on atom energy produced during neutron irradiation or implant at a much higher energy, such that a thicker damage layer is produced? Here we address this question by measuring the full strain tensor for two ion implantation energies, 2 MeV and 20 MeV in self-ion implanted tungsten, a critical material for the first wall and divertor of fusion reactors. A comparison of 2 MeV and 20 MeV implanted samples is shown to result in similar lattice swelling. Multi-reflection Bragg coherent diffractive imaging (MBCDI) shows that implantation induced strain is in fact heterogeneous at the nanoscale, suggesting that there is a non-uniform distribution of defects, an observation that is not fully captured by micro-beam Laue diffraction. At the surface, MBCDI and high-resolution electron back-scattered diffraction (HR-EBSD) strain measurements agree quite well in terms of this clustering/non-uniformity of the strain distribution. However, MBCDI reveals that the heterogeneity at greater depths in the sample is much larger than at the surface. This combination of techniques provides a powerful 1

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Section: Ion Implantationmentioning

confidence: 93%

Nanoscale lattice strains in self-ion implanted tungsten

Phillips

Das

et al. 2020

Acta Materialia

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“…Further details of the samples, the implantation, and its effects can be found in Ref. 15. Figures 4(a) and 4(b) show that there is no change in the measured value of the thermal diffusivity or the SAW speed over the entire duration of the test for either of the samples.…”

Section: Validation Experimentsmentioning

confidence: 93%

“…This is due to the measurement spot (∼90 μm) being larger than the average grain size ( 20 μm). 15 If laser heating were significant, the measured thermal diffusivity in pristine tungsten would be lower than the room temperature book value. Figure 4(a) does not show this effect.…”

Section: Validation Experimentsmentioning

confidence: 96%

“…4. There are a number of examples for this, 13,15,16,22 with custom routines in MATLAB frequently being used to do the fitting.…”

Section: The Transient Grating Spectroscopy Setupmentioning

confidence: 99%

“…[10][11][12] Thermal diffusivity measurements from TGS have been used to detect the presence of crystal defects and impurities in metals, 13 as well as to monitor irradiation-induced microstructural evolution, for example, in single-crystal niobium 14 and tungsten. 13,15,16 TGS presents several key advantages over other more conventional thermal diffusivity and acoustic property measurement methods: it is non-contact, non-destructive, and quite rapid (<2 s for a spot measurement). The only requirement for the measurement is a flat sample surface polished to a mirror finish.…”

Section: Introductionmentioning

confidence: 99%

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Non-contact, non-destructive mapping of thermal diffusivity and surface acoustic wave speed using transient grating spectroscopy

Reza

Dennett

Short

et al. 2020

Review of Scientific Instruments

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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 the 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.

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Exceptional Performance of Room Temperature Sputtered Flexible Thermoelectric Thin Film Using High Target Utilisation Sputtering Technique

Tao,

Dutson,

Zeng

et al. 2024

Adv Materials Technologies

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The High Target Utilisation Sputtering technique (HiTUS) is of interest for industrial processes, including in roll‐to‐roll manufacturing. This study marks the first application of HiTUS to thermoelectric materials, exemplified by bismuth telluride. The HiTUS technique separates the sputtering power into the plasma power and the target power, with additional kinetic energy in the sputtering particles from the applied electrical field, thus enabling a much wider sputter parameter space to modify the film performance. This study investigates how plasma power, target power, and substrate bias in HiTUS intricately influence crystal orientation/size, elemental composition, surface morphology, and other film properties. These factors subsequently affect carrier density/mobility, and consequently the thermoelectric performance of the bismuth telluride film. These deposited films reach a power factor of 6.5 × 10−4 W m−1 K−2 with a figure of merit ≈0.14 at room temperature, the highest value for room‐temperature sputtered un‐doped bismuth telluride. Subsequent post‐deposition annealing significantly enhances the crystallinity of the film (highly polycrystalline), further improving the power factor to 23.5 × 10−4 W m−1 K‐2, with a figure of merit ≈0.45 at room temperature. The excellent performance of the HiTUS fabricated thermoelectric film opens opportunities for the large‐area manufacture of thin‐film thermoelectric materials and devices.

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Thermal diffusivity degradation and point defect density in self-ion implanted tungsten

Cited by 65 publications

References 62 publications

Nanoscale lattice strains in self-ion implanted tungsten

Nanoscale lattice strains in self-ion implanted tungsten

Non-contact, non-destructive mapping of thermal diffusivity and surface acoustic wave speed using transient grating spectroscopy

Exceptional Performance of Room Temperature Sputtered Flexible Thermoelectric Thin Film Using High Target Utilisation Sputtering Technique

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