Micorstructural and magnetic characterisation of a new kind of magnetic hybrid materials

经典的磁杂化材料包含磁软或磁硬颗粒。因此，在磁性硬颗粒磁化后，它们表现出主动磁流变效应或被动磁流变特性。在研究协会中，在弹性体基质中混合磁性硬颗粒和磁性软颗粒有望提供主动和被动磁流变特性的组合。在这种情况下，研究协会的中心目标是基于对材料特性的详细微观理解，为传感器应用合成量身定制的磁性混合材料。在这里描述的子项目中，微观结构研究以及磁性粒子间相互作用的实验分析将是工作计划的重点。微观结构研究将使用x射线显微断层扫描测量，允许对单粒子分辨率的粒子分布进行三维评估。为此目的，必须首先开发能够有效确定不同粒子种类的数字图像分析工具。然后分析粒子分布及其在磁场和机械载荷等外界刺激下的变化。有关的数据将作为研究协会内理论工作组进行模拟的基准，并作为投入。由于微观结构的重组在很大程度上取决于不同粒子之间的磁性粒子间相互作用，子项目的第二部分将侧重于通过改变磁性杂化材料的组成来改变这些相互作用的实验方法。因此，一阶反转曲线（FORCs），即部分迟滞回线将被记录下来。初步研究表明，这些数据对磁性杂化材料的组成是敏感的，并提供了颗粒内部磁相互作用的清晰指纹。对数据的详细解释需要对曲线有更深的理论理解，这将由理论工作组提供。总而言之，我们期望该项目将为磁性杂化材料的微观结构变化与宏观性能之间的关系提供详细的信息。这些信息将为预测某些材料特性提供基础，这些特性可以通过材料成分的各自变化来实现。

Classical magnetic hybrid materials contain either magnetically soft or magnetically hard particles. Thus, they show either an active magnetorheological effect or exhibit passive magnetorheological properties after magnetization of the magnetically hard particles. Within the research association a mixture of magnetically hard and soft particles in an elastomeric matrix is expected to provide a combination of active and passive magnetorheological properties. In this context, it will be the central goal of the research association to synthesize tailored magnetic hybrid materials for sensor applications based on a detailed microscopic understanding of the material properties. Within the subproject described here, microstructural investigations as well as the experimental analysis of the magnetic interparticle interactions will be in focus of the working program. The microstructural investigations will use X-ray microtomography measurements allowing a three-dimensional evaluation of the particle distribution with single particle resolution. For this purpose tools for digital image analysis enabling an effective determination of the different particle species will have to be developed first. Afterwards the particle distribution and their change under influence of external stimuli like magnetic field and mechanical load will be analysed. The respective data will serve as well as an input as as a benchmark for the simulations undertaken by the theoretically working groups within the research association. Since the reorganisation of the microstructure is significantly determined by the magnetic interparticle interaction between the different particles, the second part of the subproject will focus on an experimental approach to the change of these interactions by changes of the composition of the magnetic hybrid material. Therefore First Order Reversal Curves (FORCs), i.e. partial hysteresis loops will be recorded. Preliminary investigations have shown that these data are sensitive for the composition of the magnetic hybrid materials and provide clear fingerprints of the internal magnetic interaction of the particles. A detailed interpretation of the data requires a deeper theoretical understanding of the curves, which will be provided by the theoretically working groups. In total, we expect that the project will provide detailed information about the relation between microstructural changes and macroscopic properties of the magnetic hybrid materials. This information will provide the basis for a prediction of certain material properties, which can be achieved by respective changes in composition of the material.