Nanoparticle alignment using oscillating magnetic fields for scalable nanocomposite manufacturing

Magnetic assembly is a promising, scalable nanomanufacturing method to organize nanofillers within polymer nanocomposites. Nanocomposites, tailorable multifunctional materials, are critical for the advancement of aerospace technologies because nanocomposites can be potentially engineered to function for long operation endurance with light-weight, structural integrity, high thermal and radiation stability, and even with actuation/morphing capabilities. However, nanocomposite application is currently limited due to poor scalability; bulk fabrication of nanocomposites with high-quality nanostructures leading to high performance characteristics is missing. Here an active assembly of nanofillers using oscillating magnetic fields is studied to evaluate its effectiveness of organizing nanofillers throughout large-size nanocomposites. The approach taken is to parametrically study how the frequency and the flux density of the applied magnetic field influence the alignment of superparamagnetic iron oxide particles. In this parametric study, the capability to control particle alignment geometry, including the alignment line separation, is demonstrated; the effectiveness of oscillating magnetic fields to align particles is confirmed even with weak fields or 10-100 G, and particularly with small frequencies of 0.1-5 Hz. The alignment line separation increases by an average 50% when the frequency is increased from 0 Hz (DC) to 1.0 Hz with a magnetic flux density of 50-100 G. The width of the alignment lines shows an ~20% increase with low frequency ranges up to 0.1 Hz, but plateaued beyond 1 Hz. The length of the alignment lines between 50-100 G increases by an average 60% for low frequencies at or below 0.1 Hz, but show a decreasing trend for frequencies greater than 0.1 Hz. Knowledge obtained based on this study is expected to lead to a better understanding of nanoparticle alignment with the goal of coupon-sized nanocomposites with tailored and consistent nanoparticle structures in the future.