High Aspect Ratio Magnetostrictive Particles for Structurally Integrated Sensors and Transducers

Magnetostriction is a property of many magnetic materials whereby they exhibit a deformation in response to a change in magnetization, which is thus applicable to various sensor, actuators and transducer applications. Terfenol-D, Tb_xDy_1-xFe₂ (x ≈ 0.3), exhibits the largest known room temperature magnetostriction of &gt;2000 ppm, followed by Galfenol, Fe_1-xGa_x (x ≈ 0.2), with magnetostriction values of up to 400 ppm.<br/> <br/>The use of these alloys in particulate form is particularly advantageous, as the combination with a supporting matrix allows the production of active devices of complex geometries with tailorable properties. Notably, the use of a non-conductive polymer matrix drastically reduces eddy current losses in produced composites, allowing for operational use at high frequencies. This has enabled the exploitation of these alloys in various strain-coupled magnetoelectric applications through use of a piezoelectric matrix. Tailoring of the polymer and magnetostrictive phases can also yield improvements in mechanical properties, which is particularly useful for structurally integrated sensor and transducer applications.<br/> <br/>Through the use of flake-shaped particulates, shape anisotropy can be exploited to bring about enhancements in the specific strain of these magnetostrictive phase/polymer composite systems. To further these efforts, in this work we explore the production of these flake-shaped geometries using high-energy ball milling and quantify the effects this technique has on the crystal structure of polymer embedded Galfenol and Terfenol-D particulates. The work provides useful insights into the material processing requirements to optimize the performance of these alloys in multi-functional composite applications such as structurally integrated sensors and transducers.