Evolution of the magnetization response of magneto-active elastomers made with hard-magnetic M-type barium hexaferrite p
- PDF / 263,517 Bytes
- 5 Pages / 432 x 648 pts Page_size
- 62 Downloads / 161 Views
Evolution of the magnetization response of magneto-active elastomers made with hardmagnetic M-type barium hexaferrite particles Corey Breznak and Paris von Lockette The Pennsylvania State University, 160 Hammond Building, University Park, PA 16802, U.S.A. ABSTRACT Magneto active elastomers (MAE), particulate filled magneto-sensitive composites, were made with increasing volume contents of 325 mesh M-type barium hexaferrite (BAM) particles within a silicone elastomer matrix. The volume contents of BAM ranged from 10% to 35% v/v. Vibrating sample magnetometery measurements showed that the remanence and saturation, both per unit magnetic material, increased by 50% from 10%v/v to 20%v/v before slowing decreasing as v/v increased to 35%. The results clearly show in peak in the effectiveness of the embedded particles to produce bulk magnetization near 20% v/v. One possible means for the increase stems from alignment of the magnetization of the particles and hence of the magnetic domains within particles. To assess this possible alignment, Gaussian probability distribution of magnetization orientations was fit to the experimental data to ascertain the change in the distribution as a function of v/v. Results showed 20% v/v had the highest degree of alignment. The results highlight, at a bulk scale, the possible evolution of microstructure within the composite. Similar results have been seen in image analysis of physical particle distribution of other magneto-sensitive particulate composites. The results suggest that effective processing techniques can be used to greatly enhance the bulk magnetization of these and similar composites, paving the way for decreasing required magnetic content to achieve target response specification and possibly resulting miniaturization. INTRODUCTION Magneto active elastomers (MAEs) are a type of smart material that consist of hardmagnetic particles embedded in an elastomer matrix. Their magneto-mechanical response is generated by the interaction of an external magnetic field with the particles and the resulting action of the particles on the matrix. This interaction results in the development of a distributed magnetic torque within the MAE. Due to this torque, MAE “patches” can be used in a variety of applications including active origami structures and locomotion [1, 2, 3,4,5]. Strategically placed MAE patches, whose torques cause moments along predetermined paths, can cause a structure to bend or fold into proscribed shapes or with proscribed motions. The degree of actuation produced by an MAE patch is related to the amount of magnetic material present and the resulting aggregate magnetization vector of that material. To increase torque, high concentrations of magnetic particles, 30% by volume and beyond, have traditionally been employed [1,2,3,4,5]. It should be noted that thirty percent by volume approaches the percolation threshold for spherical particles. The increased magnetic content in the composite increases the internal magnetization simply through enhanced density of magnetic domai
Data Loading...
