The purpose of this study is to demonstrate the capability of a single process, heterogenous sonochemistry, as a tool to produce two very different nanocomposites with tunable properties: a superconductor, MgB₂ with nano-inclusions, and iron/iron oxide (Fe/Fe₂O₃) in an alumina (Al₂O₃) matrix. By modifying the sonochemical parameters, one is able to tune the magnetic properties and enhance the superconducting properties of MgB₂ and the superparamagnetic (SPM) properties of the Fe/Al₂O₃ system. This tuning is done through the ability of sonochemical irradiation, “)))” or the exposure to high intensity ultrasound (HIU), to produce extreme environments where chemical and physical processes can occur due to acoustic cavitation. ))) has been shown to reduce particle size, increase reactivity, act as a catalyst, and improve powder homogeneity. These are the effects of ))) which are exploited in this study.

For the MgB₂ study, B powder (both with and without dopants/inclusions) is exposed to HIU in a decane solution before reaction with Mg to form MgB₂ nanocomposites. MgB₂ is produced by encapsulation of stoichiometric amounts of B and Mg in a Ta pouch, which is then reacted and pressed using hot isostatic press (HIP). The result is a dense MgB₂ pellet that is then cut, polished, and measured using a SQUID MPMS magnetometer. Critical current, J_c, values are calculated using the Bean critical state and compared at 25K and 30K. Samples, post-))), show an increase in grain connectivity, as seen by SEM, leading to an enhancement of J_c.

The SPM study utilized ))) to create SPM nanocomposites through the irradiation with HIU of the carrier matrix material, Al₂O₃ in the presence of a volatile organometallic precursor, Fe(CO)₅. ))) results in nanosized Fe and Fe₂O₃ being uniformly dispersed throughout the Al₂O₃ matrix. Magnetic properties of these materials are measured using the SQUID MPMS magnetometer and the nanosized Fe and Fe₂O₃ can be seen in SEM images. Analysis of the data shows a SPM component and a general trend of the data with the adjustment of slurry loading, V% of sample to medium, and mass percentage, M% of Fe to Fe+Al₂O₃. The trends suggest that an increase in M% results in an increased number of SPM particles, but the V% has a optimized value where the magnetization peaks, corresponding to a peak in the moment per SPM particle.