Polymer bonded textured composites with single crystalline NiMn-based MSM particles for magnetic-field controlled dampers and actuators

磁形状记忆（MSM）合金是一类新型的磁驱动活性材料，在7M调制马氏体结构的单晶Ni2MnGa中表现出高达10%的大应变。磁场诱导的双边界运动可以用于致动器、传感器，并且由于它是一个能量耗散过程，也可以用于减振装置。然而，Ni2MnGa单晶很难制备，并且由于其本身非常脆，因此不易支撑显著的拉伸应力。一种解决方案是使用悬浮在刚度匹配的聚合物基质中的排列的MSM颗粒。在这个项目中，MSM颗粒将由熔融提取的Ni2MnGa纤维生产。该方法通过适当的热处理，简化了单晶马氏体颗粒的制备。然后，将颗粒嵌入聚合物基质中，就可以制成复合材料。材料加工、表征和建模将用于优化磁性和磁塑性性能，这取决于颗粒的排列、大小和形状以及堆积密度，还取决于聚合物的热学和机械性能。该复合材料的另一个优点是，单晶Ni2MnGa的典型阈值行为可以通过调整其磁性、热学和磁机械性能来调节。

Magnetic shape memory (MSM) alloys are a new class of magnetically driven active materials that show large strains of up to 10% in single-crystal Ni2MnGa of 7M modulated martensitic structure. The magnetic field induced movement of twin boundaries can be exploited for actuators, sensors and, as it is an energy dissipating process, also for vibration damping devices. However, single-crystals of Ni2MnGa are difficult to prepare and cannot easily support significant tensile stresses as they are inherently very brittle. One solution is the use of aligned MSM particles suspended in a stiffness-matched polymer matrix. In this project, MSM particles will be produced from melt-extracted Ni2MnGa fibres. This, in the field, unique method simplifies the preparation of single-crystal martensitic particles by an appropriate heat treatment. Composites will then be produced by embedding the particles in a polymer matrix. Materials processing, characterisation and modelling will be used to optimise magnetic and magnetoplastic properties, which depend on particle alignment, size and shape of the particles as well as packing density but also on thermal and mechanical properties of the polymer. One further advantage of the here to be developed composites could be that the typical threshold behaviour of single-crystal Ni2MnGa could be moderated by tailoring their magnetic, thermal and magneto-mechanical properties.