EAGER: Collaborative Research: Positron annihilation spectroscopy of Earth materials: A combined materials characterization approach

EAGER：合作研究：地球材料的正电子湮灭光谱：一种组合材料表征方法

• 批准号: 2001388
• 负责人: Heather Watson
• 金额: $ 5.1万
• 依托单位: Union College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-12-01 至 2021-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2001388&HistoricalAwards=false
• 关键词: EAGER; Collaborative; Research; Positron; annihilation

Our knowledge of the Earth and its history strongly depends on our understanding of the materials that make up the bulk of the planet. Laboratory measurements of Earth materials (e.g., rocks, minerals, and magmas) are used in conjuction with direct observations of the planet and numerical models to help build the rich and complex view of the Earth and its inner workings that we have today. In this project, the investigators seek to further our understanding of the atomic-scale physical properties of several relevant Earth materials through the development of a very high resolution materials characterization technique called positron annihilation spectroscopy. The benefit of this technique is that it allows for direct investigation of crystalline solids at an atomic level, which is not routinely done with other conventional methods used in the geosciences. This project aims to build a new positron annihilation lifetime spectroscopy apparatus, test and calibrate the instrument, and characterize the atomic scale defect populations in several important Earth materials including metals, oxides, and silicate minerals. The undertaking will involve interdisciplinary collaborations between nuclear physicists and experts in the area of materials characterization and geoscience. The project will also support two female faculty, undergraduate curriculum development, and advanced student research at a liberal arts college. Understanding defects in crystalline solids is important for our general understanding of Earth materials because of their relationship to atomic mobility (diffusion) within crystals, nucleation of crystals and formation of new phases as well as electrical and heat transfer properties. When a significant population of defects are included in the crystal structure, it may affect transport properties of the crystal significantly. Many crystals in natural systems may have been exposed to defect creating events including radiation damage and deformation. To accurately apply experimentally determined diffusion parameters to natural systems, a thorough understanding of the relationship between defects and diffusion is crucial. Direct measurements of defect populations in natural and synthetic Earth materials is generally lacking. Positron annihilation spectroscopy is a non-destructive technique used to characterize defects and voids in materials at a sub nm to atomic scale. The technique has been used extensively in the materials science and nuclear materials communities for decades to examine defect properties and the effects of radiation damage on synthetic and industrial materials, but has not yet gained popularity in the Earth sciences community. The goal of this project is to develop a methodology that will enable further investigation into the relationship between diffusion and defect populations by direct measurement of defects in a variety of Earth relevant materials using positron annihilation spectroscopy. The project will also contribute to the education and research training of undergraduate students and provide opportunities for interdisciplinary work between mineral physics, nuclear physics, materials science, and geochemistry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

我们对地球及其历史的了解在很大程度上取决于我们对构成地球主体的物质的理解。对地球物质(如岩石、矿物和岩浆)的实验室测量与对地球的直接观测和数字模型相结合，有助于建立我们今天所拥有的丰富而复杂的地球及其内部工作原理的视图。在这个项目中，研究人员试图通过开发一种名为正电子湮没光谱的非常高分辨率的材料表征技术来加深我们对几种相关地球材料的原子尺度物理性质的理解。这项技术的好处是，它允许在原子水平上直接研究晶体固体，这是地球科学中使用的其他常规方法所不具备的。该项目旨在建立一台新的正电子湮没寿命谱装置，测试和校准该装置，并表征包括金属、氧化物和硅酸盐矿物在内的几种重要地球材料中的原子尺度缺陷群体。这项工作将涉及核物理学家和材料表征和地球科学领域的专家之间的跨学科合作。该项目还将支持一所文理学院的两名女性教员、本科课程开发和高级学生研究。了解晶体固体中的缺陷对于我们对地球材料的一般理解很重要，因为它们与晶体内原子的迁移(扩散)、晶体的成核和新相的形成以及电和热传输性质有关。当晶体结构中包含大量缺陷时，可能会显著影响晶体的输运性质。自然系统中的许多晶体可能已经暴露在缺陷中，产生了包括辐射损伤和变形在内的事件。为了准确地将实验确定的扩散参数应用于自然系统，彻底了解缺陷和扩散之间的关系是至关重要的。通常缺乏对天然和合成地球材料中缺陷人口的直接测量。正电子湮没光谱是一种非破坏性的技术，用于表征材料中亚纳米级的缺陷和空洞。几十年来，这项技术在材料科学和核材料界被广泛使用，以检查合成材料和工业材料上的缺陷性质和辐射损伤的影响，但尚未在地球科学界流行起来。该项目的目标是开发一种方法，通过使用正电子湮没光谱直接测量各种与地球有关的材料中的缺陷，从而进一步研究扩散和缺陷群体之间的关系。该项目还将有助于本科生的教育和研究培训，并为矿物物理、核物理、材料科学和地球化学之间的跨学科工作提供机会。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。