Experimental simulation of silica melting and amorphization under extreme shock conditions

极端冲击条件下二氧化硅熔化和非晶化的实验模拟

• 批准号: 405932909
• 负责人: Professor Dr. Falko Langenhorst, since 10/2023
• 金额: --
• 依托单位: Institut für Geowissenschaften
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/405932909?language=en
• 关键词: Experimental; simulation; silica; melting; amorphization

The proposed research project focuses on the characterization of the structures of silica glasses formed under extreme high-pressure conditions recorded during hypervelocity impacts of planetary bodies. Temperature, pressure, and shock duration can affect the mechanisms of formation of silica glasses – rapid quenching of a silica melt or solid-state transformation of quartz – and their short- and intermediate-range order, namely, the coordination number of silicon and the size of the polyhedral rings, respectively. Thus, constraining both the mechanisms of formation and the structures of silica glasses will be possible to shed light on the impact cratering process. In order to reach this goal, three types of high-pressure experiments, which differ mainly in terms of shock duration, will be performed on quartz: laser irradiation (a few nanoseconds), high explosive (around one microsecond), and diamond anvil cell (up to a few minutes). The characterization of the short- and intermediate-range order of the newly formed glasses will be pursued by the combined use of several analytical methods: Raman, electron energy loss spectroscopy, X-ray absorption spectroscopy, electron diffraction, and X-ray diffraction. For the interpretation of the diffraction data, pair distribution functions will be calculated and compared with theoretical models of silica glasses. After the first experiments and the acquisition of the first structural data, selected natural silica impact glasses from craters of different sizes (i.e., different shock duration) will be investigated through the same analytical methods and procedures. The comparison with natural samples will be the key to relate the experimental approaches to nature, and then, to gain a better understanding of the melting and amorphization processes under extreme high-pressure conditions induced by extraterrestrial impacts. Thanks to the combination of different experimental and analytical techniques and the parallel study of natural samples, this project will be the first comprehensive work entirely devoted to understanding the mechanisms of formation and the structures of silica impact glasses.

拟议的研究项目重点是在行星体超高速撞击期间记录的极端高压条件下形成的二氧化硅玻璃的结构特征，温度、压力和冲击持续时间会影响二氧化硅玻璃的形成机制——快速淬火。二氧化硅熔体或石英的固态转变 - 及其短程和中程有序，即硅的配位数和多面体环的尺寸，从而分别限制了这两种机制。二氧化硅玻璃的形成和结构将有可能揭示撞击坑过程。为了实现这一目标，将在石英上进行三种类型的高压实验，主要区别在于冲击持续时间：激光。辐射（几纳秒）、高爆炸药（大约一微秒）和金刚石砧室（长达几分钟）将通过组合使用来表征新形成的玻璃的短程和中程有序。几个分析的方法：拉曼、电子能量损失光谱、X射线吸收光谱、电子衍射和X射线衍射，首先计算对分布函数并与石英玻璃的理论模型进行比较。通过实验和获得第一批结构数据，将通过相同的分析方法和程序对来自不同尺寸（即不同冲击持续时间）的陨石坑中选定的天然二氧化硅冲击玻璃进行研究，与天然样品的比较将是相关的关键。通过结合不同的实验和分析技术以及对自然样品的并行研究，可以更好地了解地外撞击引起的极端高压条件下的熔化和非晶化过程。该项目将是第一个完全致力于了解二氧化硅冲击玻璃的形成机制和结构的综合性工作。