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

磁形状记忆(MSM)合金是一种新型的磁驱动活性材料，它在7M调制马氏体结构的单晶Ni2MnGa中表现出高达10%的大应变。磁场诱导的孪晶边界运动可用于执行器、传感器，由于这是一个能量耗散过程，也可用于减振装置。然而，Ni2MnGa单晶很难制备，而且由于其本身的脆性，不容易承受显著的拉应力。一种解决方案是使用定向的MSM颗粒悬浮在刚性匹配的聚合物基质中。在这个项目中，MSM颗粒将从熔融提取的Ni2MnGa纤维中生产出来。在现场，这种独特的方法简化了通过适当的热处理制备单晶马氏体颗粒的方法。然后，通过将颗粒嵌入到聚合物基质中来生成复合材料。材料加工、表征和建模将用于优化磁性和磁塑性，这取决于颗粒排列、颗粒的大小和形状以及堆积密度，但也取决于聚合物的热和机械性能。这里将要开发的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、热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.