Experimental and Simulation Studies on Magnetic Nanoparticle Assembly for Scalable Polymer Nanocomposite Fabrication

摘要

The magnetic assembly of nanoparticles is a promising technique for the scalable manufacturing of tailored polymer nanocomposites. Tailored nanostructure assembly can lead to improvements in thermal, electrical, and mechanical properties of polymer nanocomposites, but it is currently difficult to achieve hierarchical morphologies of the nanoparticles. The usage of magnetic fields is a useful method to control nanoparticle assembly since it allows the bulk processing of polymer nanocomposites, while still retaining nanostructures across the large volume. Further studies are necessary for the control over magnetic nanoparticle assembly due to uncertainties in parametric variations. This work presents continued experimental and new theoretical work on nanoparticle assembly using oscillating magnetic fields. In the last 2016 SciTech/AIAA SDM conference, experimental parametric studies were presented about the effects of the magnetic flux density, frequency, and concentration on the nanoparticle structuring.In this work, the effects of additional parameters of the applied magnetic fields (the waveform type and low frequencies) and the nanoparticles (magnetic properties and size) were investigated. In order to understand the experimentally observed trends, simulations are being performed using COMSOL Multiphysics Modeling Software, particularly on the interactions between particles. Our results demonstrate that frequencies as low as 0.04 Hz can provide significant tailorability to nanoparticle assemblies. In addition, a sinusoidal waveform is found to provide even more tailorability at low frequencies compared to a square waveform. The influence particle size is apparent; larger and more homogenous nanoparticle assemblies are found for increasing particle size. In simulations, a magnetic threshold length was calculated as a function of particle orientation and separation; when the nanoparticles are separated beyond the threshold length, nanoparticle assembly does not occur due to hydrodynamic forces. The understanding of the underlying assembly mechanisms will help evaluation of the scalability of manufacturing a tailored polymer nanocomposite using an oscillating magnetic field. In near-future, fabrication of coupon-sized, thin polymer nanocomposites will be demonstrated using a scaled-up magnetic assembly set-up.