Magnetically Anisotropic Nano-Pillars: Micro-Structureing Of Nanocomposites Using Oscillating Magnetic Fields

Nanoparticles (carbon, ceramic, metal, etc.) implementation is a powerful reinforcement option for composites; organization of these nanoparticles within matrices can be tailored for desired functionalities (mechanical, electrical, thermal, thermoelectrical, etc.). When properly implemented, these nanoparticles will reinforce mechanical strength against fracture and erosion, and serve as conductive networks for defect sensing, lightning/EMI shielding, and deicing. Yet, development and application of these multi-functional nanocomposites in bulk have stagnated, because bulk manufacturing methods for nanocomposites with highly organized micro-structures are missing. In this work, we investigated scalable patterning of carbon nanotube (CNT) pillars using oscillating magnetic fields, in order to achieve bulk 1D-patterned nanocomposites in future. Particle structuring within matrices, before curing, using external fields has balanced benefits of scalability and micro-structure quality. Magnetically anisotropic nano-pillars were fabricated by e-beam coating multi-walled CNTs with ferromagnetic metal, iron (Fe). Multi-walled CNTs are a convenient structural component, for their unique, tailorable dimensions, and for multi-functional properties such as high strength and thermal/electrical transport properties. The Fe coatings on CNTs were evaluated for their dimensions and textures using electron microscopy and atomic force microscopy, and for their chemical states using X-ray photoelectron spectroscopy (XPS). Their anisotropic magnetic properties were characterized using alternating gradient force magnetometry. The preliminary assembly of the Fe-coated CNTs was conducted using permanent magnets; the results indicated that CNT alignment along the magnetic fields. In future, this magnetic method to pattern nano-pillars will be evaluated for its capability and scalability in terms of magnetic field strength, assembly time, and maximum sample size. In addition, nanocomposites will be fabricated and characterized using polymer matrices, and CNT micro-structures and nanocomposite properties will be compared to obtain further knowledge on multi-scale structureproperty relationships.