Mechanism for orientation dependence of blisters on W surface exposed to D plasma at low temperature

Jia, Y.Z.; Liu, W.; Xu, Bo; Luo, Guang–Nan; Qu, S.; Morgan, T.W.; Temmerman, G. De

doi:10.1016/j.jnucmat.2016.05.011

Cited by 46 publications

(25 citation statements)

References 26 publications

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“…Despite more than one order of magnitude variation of the incident fluence, the appearance of blisters and protrusions, namely their number density and average size, barely changed with increasing fluence. Furthermore, grains without any blister and protrusion were also present, which is consistent with previously reported results [19,29]. It should be noted, however, that the method of surface preparation could potentially influence the appearance of the observed surface modifications [8].…”

Section: Low Temperaturessupporting

confidence: 91%

Deuterium trapping and surface modification of polycrystalline tungsten exposed to a high-flux plasma at high fluences

et al. 2017

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Deuterium (D) retention and surface modifications of hot-rolled polycrystalline tungsten (W) exposed to a low-energy (40 eV/D), high-flux (2-5×10 23 D/m 2 s) D plasma at temperatures of 380 K and 1140 K to fluences up to 1.2×10 28 D/m 2 have been examined by using nuclear reaction analysis, thermal desorption spectroscopy, and scanning electron microscopy. The samples exposed at 380 K exhibited various types of surface modifications: dome-shaped blister-like structures, stepped flat-topped protrusions, and various types of nanostructures. It was observed that a large fraction of the surface was covered with blisters and protrusions, but their average size and the number density showed almost no fluence dependence. The D depth distributions and total D inventories also barely changed with increasing fluence at 380 K. A substantial amount of D was retained in the subsurface region, which thickness correlated with the depth where the cavities of blisters and protrusions were located. It is therefore suggested that defects appearing during creation of blisters and protrusions govern the D trapping in the investigated fluence range. In addition, a large number of small cracks was observed on the exposed surfaces, which can serve as fast D release channels towards the surface, resulting in a reduction of the effective D influx into the W bulk. On the samples exposed at 1140 K no blisters and protrusions were found.However, wave-like and faceted terrace-like structures were formed instead. The concentrations of trapped D were very low (<10 5 at. fr.) after the exposure at 1140 K.

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Section: Low Temperaturessupporting

confidence: 91%

Deuterium trapping and surface modification of polycrystalline tungsten exposed to a high-flux plasma at high fluences

et al. 2017

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“…The resultant supersaturated H isotopes within W may cause severe blistering and surface modification even when the incident energy is below the threshold for displacement damage [2,3]. Such blistering causes dramatic degradation in the mechanical properties (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…For H plasma exposure, blister means the dome-shape structure observable on the surface, usually associated with an underlying subsurface cavity that could be confirmed by SEM views of the cross section prepared by focused ion beam (FIB) [2,8,9]. The surface blistering of W is generally linked to the cavity formation as a result of plastic deformation [3,6,10], dislocation loop punching [6,11], agglomeration of H-vacancy complexes [12], and solute H isotope distribution [13]. Among them, plastic deformation and dislocation loop punching are widely regarded as the most common and trustworthy growth mechanisms of the sub-surface cavities (i.e.…”

Section: Introductionmentioning

confidence: 99%

Growth mechanism of subsurface hydrogen cavities in tungsten exposed to low-energy high-flux hydrogen plasma

et al. 2020

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Due to a lack of direct experimental results, the detailed mechanisms that govern the blistering behavior of tungsten (W) exposed to ITER-relevant condition in nuclear fusion remain unclear. The growth mechanism of hydrogen (H) blisters is one example. In this work, recrystallized W was exposed to H plasma at 50 eV, , and 573 K. Transmission electron microscopy (TEM) samples were prepared using plasma-focused ion beam (FIB) followed by flash-polishing to effectively remove surface damages induced by FIB. The TEM images revealed that the general blisters observed on the exposed surface are associated with underlying cavities. A considerable amount of dislocations were found in the vicinity of the cavities. Prismatic dislocation loop arrays were observed, including small size 'coffee-bean' prismatic loops and large size prismatic loops. Near the tip of surfaces cavities, evidences for the emission of shear loops were also found. Based on the experimental findings, a multi-stage growth mechanism of H cavities was proposed.The loop-punching mechanism is operative for both very small cavities and cavities with sizes larger than several hundreds of nanometers. Whereas at intermediate sizes, cavities grow by emitting shear loops from the cavity tip.

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“…Grains with directions <111> // ND are prone to blister formation when exposed to high-flux deuterium plasma, while directions <001> // ND are the most resistant ones [13,20,21]. This dependence on crystallographic orientation is very relevant for PFCs and it is also related to surface finish and hydrogen absorption and diffusion [22,23].…”

Section: 1-ebsdmentioning

confidence: 99%

Nano-hardness, EBSD analysis and mechanical behavior of ultra-fine grain tungsten for fusion applications as plasma facing material

Tanure

Bakaeva

Lapeire

et al. 2018

Surface and Coatings Technology

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Tungsten and its alloys have been extensively studied in order to be used in plasma facing components for future fusion nuclear reactors such as ITER and DEMO. In this work, an evaluation of nano-hardness, microstructure/texture and mechanical behavior using nanoindentation, electron backscatter diffraction (EBSD) and tensile test was performed. The investigated materials were ultra-fine grain lab-scale tungsten and ITER-specification commercial tungsten products, taken as reference in the as-received and annealed (at 1300°C for 1 hour) conditions. Three ultra-fine grain (UFG) tungsten grades were produced under different spark plasma sintering conditions, namely at 2000°C and 70MPa, at 1700°C and 80MPa and, finally, at 1800°C and 80MPa. EBSD analysis provides very relevant data as it is known that the crystallographic orientation affects some features of the surface damage caused by fusion-relevant plasma exposure. The present results will serve as a reference for future studies that will be carried out using plasma-exposed samples in order to correlate the observed damage with the microstructural characteristics and mechanical behavior.

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Mechanism for orientation dependence of blisters on W surface exposed to D plasma at low temperature

Cited by 46 publications

References 26 publications

Deuterium trapping and surface modification of polycrystalline tungsten exposed to a high-flux plasma at high fluences

Deuterium trapping and surface modification of polycrystalline tungsten exposed to a high-flux plasma at high fluences

Growth mechanism of subsurface hydrogen cavities in tungsten exposed to low-energy high-flux hydrogen plasma

Nano-hardness, EBSD analysis and mechanical behavior of ultra-fine grain tungsten for fusion applications as plasma facing material

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