Abstract: Cathy Yang
Mentor: Professor May Cheng
The fabrication of nanoporous materials has been of great interest for applications such as biosensors, photonic materials, and energy storage. We develop a template electrochemical deposition technique for fabricating highly ordered and highly porous nanostructured materials. Fabrication process involves the following steps: self-assembly of polystyrene spheres, electrochemical deposition of Ni metal, and sphere removal by dissolution. Pore size of the porous materials can be tuned by using different template polystyrene spheres with diameters ranging from 200nm to 750nm. Scanning electron microscopy (SEM) will be used to image the fabricated nanoporous samples. Furthermore, we propose to characterize magnetic properties of Ni three-dimensional nanoporous structures by using vibrating sample magnetometer (VSM). In specific, magnetization reversal mechanism of the porous materials in an applied magnetic field is studied at different regions of interest by a first-order reversal curve (FORC) technique. A FORC measurement is obtained through the following process: 1) a positive saturation magnetic field is applied; then 2) the field is decreased to a reversal field. 3) Magnetization, M, is measured, as the applied field is increased back to the positive saturation field. This process is repeated as magnetization is measured at different values of reversal fields, resulting in the sequential hysteresis loops of FORC measurements. Analysis on FORC distributions of the nanoporous Ni structures will shed light on the magnetization reversal mechanism of three-dimensional magnetic structures.