Abstract
A series of nanopillar compression tests were performed on tungsten as a function of temperature using in situ transmission electron microscopy with localized laser heating. Surface oxidation was observed to form on the pillars and grow in thickness with increasing temperature. Deformation between 850 °C and 1120 °C is facilitated by long-range diffusional transport from the tungsten pillar onto adjacent regions of the Y2O3-stabilized ZrO2 indenter. The constraint imposed by the surface oxidation is hypothesized to underly this mechanism for localized plasticity, which is generally the so-called whisker growth mechanism. The results are discussed in context of the tungsten fuzz growth mechanism in He plasma-facing environments. The two processes exhibit similar morphological features and the conditions under which fuzz evolves appear to satisfy the conditions necessary to induce whisker growth.
Highlights
Deformation between 850 ◦ C and 1120 ◦ C is facilitated by long-range diffusional transport from the tungsten pillar onto adjacent regions of the Y2 O3 -stabilized ZrO2 indenter
Our experiments suggest that tungsten is susceptible to the whisker growth at temperatures relevant to their application in plasma-facing environments
Nanopillar compression experiments were performed as a function of temperature up to 1250 ◦ C using a novel method based on laser heating of a metallic film on a thermally insulating substrate
Summary
Deformation between 850 ◦ C and 1120 ◦ C is facilitated by long-range diffusional transport from the tungsten pillar onto adjacent regions of the Y2 O3 -stabilized ZrO2 indenter. Understanding structure and chemistry of the plasma-facing surface, as well as its evolution, is of potential importance He particle fluxes inherent to the reactor wall environment. The fuzz consists of tungsten metal filaments with widths on the order of nanometers that can grow to lengths on the micron to millimeter scale depending on the environmental conditions that produced them [4,5] These features form between approximately 700 ◦ C and 1700 ◦ C and when low energy ions impinge the surface, typically greater than ≈20 eV [2]. Existing models for tungsten fuzz evolution assume that the formation of He bubbles drives a mechanical response that produces the fuzz morphology. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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