(420t) Sonolytic Synthesis of Single and Binary, Metal-Based Magnetic Nanostructured Materials

Magnetic nanomaterials were synthesized using sonolytic techniques. Single metal- and binary-based nanostructured materials with various morphologies and magnetic properties were produced via sonochemical reactions with NH₃OH solutions and iron, magnesium and calcium chlorides. All magnetic nanomaterial products were characterized using x-ray diffraction (XRD), elemental analysis, scanning and transmission electron microscopies (SEM and TEM) and superconducting quantum interference device (SQUID) magnetometric analysis. Morphology and crystallite product sizes varied with the metal components, solution composition, and pH level.  Crystallite sizes were observed to range from 5.92 to 72.13 nm. Various nanostructured products were observed to include nanoparticles, nanocrystallites, nanorods, microcubics and microdiscoids. 

Magnetic data for sonolitically altered mixtures and alloyed materials were also measured in this work.  Ultrasonic irradiation provided an effective pathway for the synthesis of the magnetic nanomaterials through redox reaction with metal chlorides and NH₃OH.  The data revealed magnetic properties for all solid systems.  Mg(OH)₂ and CaCO₃-based systems displayed an agreement with properties that coincided with superparamagnetic properties, where the plot of the magnetic field divided by the system temperature collapsed respectively.   Mg(OH)₂ + Fe(OH)₃ system revealed an agreement with paramagnetic properties, meaning that the graph denoted that under applied field the magnetic moment was observed to be linear with a positive slope.  As for, Fe₃O₄ + CaCO₃ mixtures, MgFe₂O₃ and Fe₃O₄ under applied magnetic field indicated a ferromagnetic hysteresis plot, meaning that the particles retained magnetic field after saturation.  A coercivity study was performed to determine the intensity of an applied magnetic field to reduce the magnetization of the particles to zero for the ferromagnetic structures and this study showed a linear decline as temperature increased.  It was also observed that MgFe₂O₃ required the highest magnetic field to reduce magnetization to zero.