Controlled Orientation and Actuation of High Performance Polyimide Nanocomposites Using Magnetic Nanoparticles Tethered Graphene

Many new technologies require control of thermal and electrical transport direction in lightweight advanced composites. Polyimide is a high performance polymer with superior properties such as high glass transition temperature, excellent thermal stability, high modulus, low dielectric constant, low coefficient of thermal expansion, and radiation resistance. Hybrid nickel graphene nanoparticles with magnetic and high electrical, thermal and mechanical properties were prepared using the thermal decomposition method. The nickel nanoparticles were covered with an amorphous carbon layer to protect from oxidation. Ultra-small angle X-ray scattering (USAXS) of the Ni-graphene polyimide nanocomposites revealed a dual size distribution of nickel nanoparticles when estimated as spheres, which was in agreement with HR-TEM and detailed magnetic hysteresis measurements. The Ni-graphene nanoparticles were dispersed in the polyimide in the presence of magnetic field yielding a high degree of nanoparticle orientation in the polyimide matrix. This orientation resulted in high in-plane electrical and mechanical properties of polyimide nanocomposites. The nanoparticle orientation was confirmed by changes to saturation magnetization as the sample was rotated in the magnetic field, as well as by transmission electron microscopy.  The saturation magnetization of Ni-graphene polyimide nanocomposites containing randomly oriented nanoparticles increased with increasing magnetic nanoparticle content. The nanocomposites exhibited actuation in the presence of a magnetic field.