Hollow and Solid Spherical Magnetostrictive Particulate Composites

Abstract

Nickel microspheres were produced by the spark erosion technique under both liquid nitrogen and water conditions. Density measurements and Scanning electron microscope analysis revealed that a significant portion of the Ni particles produced under the liquid nitrogen conditions are hollow spheres with a density of 6.67(4)g/cm(3) while the particles produced in water are primarily solid spheres with a density of 8.40(1)g/cm(3), close to the bulk nickel value of 8.90 g/cm(3). Nickel/polymer composites incorporating the hollow and solid nickel microspheres were manufactured with volume fractions of 25% and 36%, respectively. The hollow and solid nickel composites exhibited saturation magnetostrictions of -24 and -28 ppm, respectively. In addition, small quantities of Terfenol-D (Tb0.3Dy0.7Fe2) were spark eroded under liquid argon conditions with similar to10% by volume of the spark eroded particles being solid microspheres. Calculations indicate that aligned composites that incorporate these Terfenol-D microspheres could reach a strain value of 2000 ppm.