In-situ diagnostics of metal hydride composites during cyclic hydrogenation by neutron radiography and tomography

来自可再生能源的氢作为未来的能源载体将发挥重要作用。因此，储氢技术在氢基能源循环中至关重要。与高压和低温储氢相比，金属氢化物（MH）提供了以高容量存储密度（高达150 g-H2/l，相比之下，700 bar压力容器的最大储氢容量为150 g-H2/l）储存氢的可能性。39 g-H2/l)，在低压（2-30 bar）下，在中等温度（室温）下无蒸发损失。基于氢化物形成合金和高导热二次相的mh -复合材料（MHC）是高动态氢基存储溶液的优势。由于MH反应区导热系数较差（< 1 W/(mK)），不适合快速加载和卸载动力学，因此后者用于在加氢和脱氢过程中传递反应热。为了了解基于mhc的储氢系统在实际操作条件下的过程，需要进行现场诊断。为了达到这个目的，中子成像是非常合适的，因为氢核对中子辐射有很大的横截面。利用中子成像，可以以一种无损的、原位的和定量的方式可视化氢浓度。加载和卸载可以在几秒钟的时间分辨率结合微米尺度的空间分辨率进行实时研究。中子层析成像是定量解决MHC内氢的三维分布的唯一方法。本DFG项目拟首次利用原位成像技术（中子射线成像和断层扫描）实时研究轻金属基MHC （Mg基和ti基合金）加氢-脱氢过程中相形成的微观过程及其对MHC形貌和微观结构的影响。对于第二阶段，将使用一组不同的高导热石墨改性。MHC的相组成（分散性、各向异性、孔径分布）、制备参数以及气体和传热性质对加氢/脱氢动力学和长期行为的影响将通过系统的参数变化来研究。从氢-固反应过程中MHC的结构变化可以推导出高效、长期稳定的固态储氢系统的有价值的结论。

Hydrogen from renewable energy sources will play an important role as a future energy carrier. Therefore, hydrogen storage technologies are crucial in a hydrogen-based energy cycle. Compared to high pressure and cryogenic hydrogen storage, metal hydrides (MH) offer the possibility to store hydrogen with a high volumetric storage density (up to 150 g-H2/l, cf. 700 bar pressure vessels with max. 39 g-H2/l) under low pressure (2-30 bar) at moderate temperatures (room temperature) without boil-off losses.For high dynamic MH-based storage solutions MH-composites (MHC) based on a hydride forming alloy and a highly heat conducting secondary phase are advantageous. The latter is utilized to transport the reaction heat during hydrogenation and dehydrogenation, since the MH reaction zone offers only poor thermal conductivity (< 1 W/(mK)) which is not suitable for fast loading and unloading dynamics. In-situ diagnostics is needed to understand the processes inside MHC-based hydrogen storage systems under realistic operation conditions. For this purpose, neutron imaging is well suited because of the large cross-section of the hydrogen nuclei towards neutron radiation. With neutron imaging it is possible to visualize hydrogen concentrations in a non-destructive, in-situ and quantitative way. Loading and unloading can be investigated in real-time with a few seconds temporal resolution combined with a spatial resolution at micrometer-scale. Neutron tomography is the only method to resolve the three-dimensional distribution of hydrogen within a MHC quantitatively.In this DFG project it is planned to investigate for the first time the microscopic processes of the phase formation during hydrogenation-dehydrogenation of light-metal-based MHC (Mg- and Ti-base alloys) and its effect on the morphology and the microstructure of the MHC with in-situ imaging methods (neutron radiography and tomography) in real time. For the second phase a set of different highly heat conducting graphite modifications will be used. The influence of the MHC phase composition (dispersity, anisotropy, pore size distribution), the parameters of preparation and the gas and heat transfer properties on the hydriding/dehydriding kinetics and the long-term behavior will be investigated by a systematic variation of the parameters. From the structural changes of the MHC during the hydrogen-solid reactions valuable conclusions for efficient and long-term stable solid-state hydrogen storage systems can be deduced.