A general model for welding of ash particles in volcanic systems validated using in situ X-ray tomography
A general model for welding of ash particles in volcanic systems validated using in situ X-ray tomography
复制标题
使用原位 X 射线断层扫描验证火山系统中灰烬颗粒焊接的通用模型
DOI：
10.1016/j.epsl.2019.115726
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发表时间：
2019
影响因子：
5.3
通讯作者：
Dingwell, Donald B.
中科院分区：
文献类型：
--
作者：
Wadsworth, Fabian B.;Vasseur, Jérémie;Schauroth, Jenny;Llewellin, Edward W.;Dobson, Katherine J.;Havard, Tegan;Scheu, Bettina;von Aulock, Felix W.;Gardner, James E.;Dingwell, Donald B.
焊接发生在火山颗粒在各种环境下的运输和沉积过程中，包括火山碎屑密度流、火山导管和喷气发动机。焊接速度影响危害相关的过程，并且对熔体中的水浓度敏感。我们利用原位同步辐射源x射线断层成像技术，对无晶、水过饱和流纹岩玻璃碎片在高温下的焊接进行了表征。连续测量孔隙率和孔隙空间几何形状表明，孔隙率衰减到1-3 vol.%的渗透阈值，此时气泡被隔离，焊接停止。我们建立了一个新的数学模型，将烧结和水扩散相结合，在不需要经验调整参数的情况下拟合实验数据。一个关键的进步是，该模型适用于由围压、表面张力或两者结合驱动焊接的系统。我们使用该模型来约束焊接时间尺度在广泛的火山设置。我们发现火山系统跨越了表面张力重要的毛细管焊接和围压重要的压力焊接的制度划分。我们的模型预测，在自然界中，焊接时间尺度从几秒到几年不等，这主要取决于颗粒粘度或颗粒脱气过程中这种粘度的演变。我们提供用户友好的工具，用Python™和Excel®编写，以解决用户定义的初始条件下焊接过程中孔隙率和溶解水浓度的演变。
Welding occurs during transport and deposition of volcanic particles in diverse settings, including pyroclastic density currents, volcanic conduits, and jet engines. Welding rate influences hazard-relevant processes, and is sensitive to water concentration in the melt. We characterize welding of fragments of crystal-free, water-supersaturated rhyolitic glass at high temperature usingin-situsynchrotron-source X-ray tomography. Continuous measurement of evolving porosity and pore-space geometry reveals that porosity decays to a percolation threshold of 1–3 vol.%, at which bubbles become isolated and welding ceases. We develop a new mathematical model for this process that combines sintering and water diffusion, which fits experimental data without requiring empirically-adjusted parameters. A key advance is that the model is valid for systems in which welding is driven by confining pressure, surface tension, or a combination of the two. We use the model to constrain welding timescales in a wide range of volcanic settings. We find that volcanic systems span the regime divide between capillary welding in which surface tension is important, and pressure welding in which confining pressure is important. Our model predicts that welding timescales in nature span seconds to years and that this is dominantly dependent on the particle viscosity or the evolution of this viscosity during particle degassing. We provide user-friendly tools, written in Python™ and in Excel®, to solve for the evolution of porosity and dissolved water concentration during welding for user-defined initial conditions.
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DOI：
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发表时间：
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