Growth kinetics and texture formation of pyroxene reaction rims in thin films settings

温度驱动扩散控制反应层的生长是实验室测量多晶体中反应扩散的既定方法。将实验结果应用于地壳中的扩散时，由于时间尺度不同而产生的问题将通过在薄膜内的设置来解决。主要研究了橄榄石与方镁石之间的尖晶石反应层以及橄榄石与石英之间的斜方辉石层中的结构和残余应变。我们将研究两种不同的设置：一个由衬底和种子层组成的2层系统和一个由衬底，种子层和反应物层组成的3层系统。该项目的目的是作为一个补充，在实验和分析方面的项目6，目的是在差应力对织构形成的影响。在这个FOR 741 D-A-CH提案“纳米级工艺和地质材料特性”-项目2号项目中，应力将不会从外部施加到反应样品上，但我们将检测和量化由内部衍生应力引起的晶格应变。该项目的标志是使用原位方法来观察应变和纹理，不仅在其最终状态，而且在它们出现的方式。由于层（衬底，种子层以及反应物）的结晶度在退火过程中的变化，我们建议进行原位能量色散同步X射线衍射（EDXRD）实验，以遵循在生长过程中的反应环的发展。对于这个实验，薄膜设置将在一个特殊的反应室中退火，该反应室可以安装在柏林同步加速器设施Bessy的EDDI光束线上。这种特殊的实验装置能够真实的实时监测微观结构和织构的演变，并将该项目提高到一个突出的分析水平。为了研究反应层的微观结构、织构和非原位残余应变，该项目强烈依赖于最新的X射线衍射方法。这些方法原则上是批量方法，而不是高空间分辨率方法。然而，由于我们打算应用的薄膜研究的专门应用（掠入射X射线衍射）以及同步加速器光束的高分辨率，我们实际上解决了反应边缘的结构特征，其尺度为10到100纳米，即微米和纳米级之间的范围，有时称为中尺度。这个区域是特别感兴趣的纹理和微观结构的演变的理解，因为通常在这里的净转移反应的能量预算变得明显占主导地位的应变和界面能的贡献。

The temperature driven diffusion controlled growth of reaction layers is an established method for laboratory measurements of reactive diffusion in polycrystals. The problem arising when applying the experimental results to diffusion in the earth crust due to different timescales will be solved by miniaturising the settings within thin films. The proposed work focuses on texture and residual strain in spinel reaction layers between corundum and periclase as well as orthopyroxene layers between olivine and quartz. We will investigate two different kinds of settings: a 2-layer system consisting of substrate and seed layer and a 3-layer system consisting of substrate, seed layer and reactant layer. The proposed project is designed as a complement both in experimental and in analytical aspects to project 6, that aims at the effect of differential stress on texture formation. In this FOR 741 D-A-CH Proposal “Nanoscale Processes and Geomaterials Properties” - Project No. 2 project stress will not be externally applied to the reacting samples, but we will detect and quantify the lattice strain that is induced by internally derived stress. The trade mark of this project is the use of use in-situ methods to observe strain and texture not only in their final states but also the way they emerge. Because the crystallinity of the layers (substrate, seed layer as well as reactant) changes during the annealing process we propose to perform in-situ energy dispersive synchrotron X-ray diffraction (EDXRD) experiments to follow the development of the reaction rim during the growth process. For this experiment the thin film setting will be annealed within a special reaction chamber, which can be installed at the EDDI beam line of the Berlin synchrotron facility Bessy. This special experimental setup enables a real time monitoring of microstructure and texture evolution and will raise the project to an outstanding analytical level. To investigate the microstructure, texture and residual strain of the reaction layers ex-situ, the project bears strongly on up-to-date X-ray diffraction methods. These are in principle bulk methods as opposed to high spatial resolution methods. However due to the specialised applications for thin film investigations that we intend to apply (grazing incidence X-ray diffraction) as well as the high resolution of synchrotron beams we actually address structural features in reaction rims that are on a scale of 10s to 100s of nanometers, that is the range between micro- and nanoscale that is sometimes referred to as mesoscale. This region is of special interest for the understanding of texture and microstructure evolution, because typically here the energy budget of net-transfer reactions becomes clearly dominated by the contributions of strain and interface energy.