Dresden 2006 – scientific programme

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MA: Magnetismus

MA 4: Magnetic Materials I

MA 4.9: Talk

Monday, March 27, 2006, 12:15–12:30, HSZ 401

NiMnGa fibres for use in polymer composites — •Nils Scheerbaum, Dietrich Hinz, Oliver Gutfleisch, and Ludwig Schultz — IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany

Composites made of polymer and magnetic shape memory particles (MSM particles) may be used as actuators or as mechanical energy absorber for damping applications. Ideally, the MSM particles should be, at the operating temperatures, in the martensitic state and single-crystalline when in the austenitic state. Fibres of 51Ni-27Mn-22Ga (at.%) were prepared by crucible melt extraction. Their size is about 60µm in diameter and 1cm in length. The structural and magnetic properties of the fibres are similar to those of bulk material with the same composition. The grain size of the meltextracted fibres was determined by SEM to about 5µm. In order to achieve grain growth, the fibres were annealed at 1000-1100^∘C. After annealing, the grain size is in the order of the diameter of the fibres. Also the martensite start and the Curie temperature are affected by the annnealing (varified by DSC and susceptometry). They increase from 30^∘C to 45^∘C and from 88^∘C to 98^∘C respectively. XRD analyses reveal that the austenite is cubic and that the martensite is tetragonal with the 5M modulation and c/a=0.94. First composites were prepared using different polymers and the fibres applying various magnetic fields to align the MSM particles.