H trapping and mobility in nanostructured tungsten grain boundaries: a combined experimental and theoretical approach

Abstract

The trapping and mobility of hydrogen in nanostructured tungsten grain boundaries (GBs) have been studied by combining experimental and density functional theory (DFT) data. Experimental results show that nanostructured W coatings with a columnar grain structure and a large number of (1 1 0)/(2 1 1) interfaces retain more H than coarsed grained W samples. To investigate the possible influence of GBs on H retention, a complete energetic analysis of a non-coherent W(1 1 0)/W(1 1 2) interface has been performed employing DFT. Our results show that this kind of non-coherent interface largely attracts point defects (both a H atom and a metallic monovacancy separately) and that the presence of these interfaces contributes to a decrease in the migration energy of the H atoms with respect to the bulk value. When both the W monovacancy and H atom are introduced together into the system, the HV complex becomes the most stable configuration and one of the mechanisms explaining the H retention in the radiation damaged GB observed experimentally.

The Critical Raw Materials in Cutting Tools for Machining Applications: A Review

“…In intimate connection with artificial intelligence concepts, appropriately configured computational programming and access to high-throughput resources allows a machine to extract patterns and learn from pre-existing data bases much faster and more accurately than ever before, iterating the processes until fully satisfying relationships and results have been obtained and, in doing so, reducing human intervention to a minimum. Interatomic potential fitting for ulterior MD modelling (Atomistica [311], Atomicrex [312], Potfit [313], OpenKIM [314]), hybrid DFT(Density Functional Theory)-MD simulations (Gaussian approximation potential (GAP) [315], SNAP [316]) or DFT-KMC [317,318] and finite element [319][320][321] multiscale modelling approaches are paradigmatic examples of advanced materials simulation methodologies that make use of machine learning-related techniques. The scaling up from ab-initio and atomistic time and lengths to mesoscopic and macroscopic scales benefits enormously from these kinds of procedures, as stated in several different recent reviews ( Figure 20).…”

A Review of Dangerous Dust in Fusion Reactors: from Its Creation to Its Resuspension in Case of LOCA and LOVA

“…However, the formation of brittle tungsten silicide may be disadvantageous for the powder metallurgical production of bulk W-Cr-Si alloys if a good workability is needed [49,50]." Several oxidation tests have been made with different W-based alloys at a temperature of 1073 K for 3 hours (see Table 1 taken from [69]). Table 1 shows good results for Tungsten-Chromium-Titanium alloys.…”

Object kinetic Monte Carlo simulations of irradiated tungsten for nuclear fusion reactors

“…The value of formation energy of a vacancy from a GB in W has been published in Refs. [161,162]. This value (E f (V) GB = 1.6 eV) is much lower than the formation energy of a vacancy in bulk tungsten (E f (V) Bulk = 3.23 eV).…”

“…GBs with a migration energy lower than in the bulk [161,162]. Thus, GBs might act as preferential diffusion path for H atoms [163].…”

“…The fact that the formation energy of vacancies in the GB region [161,162] is lower than that in the bulk [66] may facilitate the trapping of H atoms in vacancies formed at the GBs. Thus, the role of vacancies (and in turn, temperature) in the case of the observed H concentration enhancement at the GB region is not clear [164,165].…”