Weerasinghe Asanka, Wirth Brian D, Maroudas Dimitrios
Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States.
Department of Nuclear Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States.
ACS Appl Mater Interfaces. 2020 May 13;12(19):22287-22297. doi: 10.1021/acsami.0c01381. Epub 2020 Apr 28.
We report results of systematic molecular-dynamics computations of the elastic properties of single-crystalline tungsten containing structural defects, voids and overpressurized He nanobubbles, related to plasma exposure of tungsten serving as a plasma-facing component (PFC) in nuclear fusion devices. Our computations reveal that the empty voids are centers of dilatation resulting in the development of tensile stress in the tungsten matrix, whereas He-filled voids (nanobubbles) introduce compressive stress in the plasma-exposed tungsten. We find that the dependence of the elastic moduli of plasma-exposed tungsten, namely, the bulk, Young, and shear modulus, on its void fraction follows a universal exponential scaling relation. We also find that the elastic moduli of plasma-exposed tungsten soften substantially as a function of He content in the tungsten matrix, following an exponential scaling relation; this He-induced exponential softening is in addition to the softening caused in the matrix with increasing temperature. A systematic characterization of the dependence of the elastic moduli on the He bubble size reveals that He bubble growth significantly affects both the bulk modulus and the Poisson ratio of plasma-exposed tungsten, while its effect on the Young and shear moduli of the plasma-exposed material is weak. Our findings contribute directly to the development of a structure-property database that is required for the predictive modeling of the dynamical response of PFCs in nuclear fusion devices.
我们报告了对含结构缺陷、空洞和超压氦纳米气泡的单晶钨弹性特性进行系统分子动力学计算的结果，这些与用作核聚变装置中等离子体面对部件（PFC）的钨的等离子体暴露有关。我们的计算表明，空的空洞是膨胀中心，导致钨基体中产生拉应力，而充满氦的空洞（纳米气泡）在等离子体暴露的钨中引入压应力。我们发现，等离子体暴露钨的弹性模量，即体模量、杨氏模量和剪切模量，对其空洞率的依赖性遵循普遍的指数标度关系。我们还发现，等离子体暴露钨的弹性模量随着钨基体中氦含量的增加而显著软化，遵循指数标度关系；这种由氦引起的指数软化是除了基体随温度升高而导致的软化之外的。对弹性模量对氦气泡尺寸依赖性的系统表征表明，氦气泡的生长显著影响等离子体暴露钨的体模量和泊松比，而其对等离子体暴露材料的杨氏模量和剪切模量的影响较弱。我们的研究结果直接有助于建立一个结构-性能数据库，这是核聚变装置中PFC动力学响应预测建模所必需的。
