Formation of magnetically anisotropic composite films at low magnetic fields

Abstract

We present a straightforward two-step technique for the fabrication of poly (methyl methacrylate) composites with embedded aligned magnetic chains. First, ferromagnetic microwires are realized in a poly (methyl methacrylate) solution by assembling iron nanoparticles in a methyl methacrylate solution under heat in an external magnetic field of 160 mT. The simultaneous thermal polymerization of the monomer throughout the wires is responsible for their permanent linkage and stability. Next, the polymer solution containing the randomly dispersed microwires is casted on a solid substrate in the presence of a low magnetic field (20–40 mT) which induces the final alignment of the microwires into long magnetic chains upon evaporation of the solvent. We prove that the presence of the nanoparticles assembled in the form of microwires is a key factor for the formation of the anisotropic films under low magnetic fields. In fact, such low fields are not capable of driving and assembling dispersed magnetic nanoparticles in the same type of polymer solutions. Hence, this innovative approach can be utilized for the synthesis of magnetically anisotropic nanocomposite films at low magnetic fields.

Computer-controlled electromagnetic control and image capture system for alignment of magnetic graphene nanofillers in epoxy composites

“…4(a)) was developed since a constant magnetic field was required for the nanofiller alignment process. It has been shown [5] that the desired alignment of GNPs within an epoxy resin would occur with a magnetic field strength of at least 100 mT. An iron C-core with dimensions of 100 × 170 × 30 mm with a 110 mm gap was used with two separate I-cores with dimensions of 100 × 30 × 30 mm.…”

Directed Assembly and Mechanics of Functional Polymer Composites

“…Since the magnetophoretic effect scales volumetrically, strong magnetic fields can induce dipole alignment in both the filler particle and the polymer Low-strength magnetic fields are sometimes used to minimize the complex effects that polymer alignment has on the mechanical properties of the composite [126] and to reduce the possible magnetic effects on components [127] . Fe3O4 magnetic nanoparticles were assembled within PMMA film by magnetophoretic forces using two permanent magnets, one was stationary and the other was manipulated in order to create complex interference-like patterns [128].…”