Ultra-low-density magnetic nickel aerogel

Aerogels are the least-dense class of solid material available today, with an enormous surface area relative to their weight and volume due to their porous nature. They also have extraordinary heat and sound insulation properties. These attributes make aerogels attractive in many branches of industry, from Mars exploration to the clean-up of oil spills. In this work we present, for the first time, the creation of nickel aerogel. Nickel aerogels, like other metal aerogels, have potential as catalysts, especially in the renewable energy storage industry. Due to nickel’s immunity to degradation, it can also be suitable for devices meant to be deployed in extreme conditions. The procedure we developed for synthesis of nickel aerogels entails the suspension of the magnetic nickel nanowires (NWs), and their freeze-casting in liquid nitrogen. Instead of freeze drying, which deforms the gel and doesn’t remove the cryoprotectants, we used freeze substitution. This involves exchanging the frozen solvent inside the gels with cold acetone, leaving the gel structure intact. Then, a supercritical drying process was implemented, resulting in a magnetic nickel aerogel with a density of . We discuss the effect of different parameters, such as addition of PVP to NW synthesis, concentration of the NWs and of glycerol, our cryoprotectant. Perhaps most interesting is the effect of magnets on the creation of the gels. Magnets were placed near the liquid nitrogen bowl, and remarkably strengthened the gels in addition to aligning them. Another notable discovery, the result of several failed attempts, is that even light sonication shreds the NWs, and should therefore be avoided in the creation process. This points to the length of the NWs being a determining factor in gel strength. We are currently working on defining further characteristics of the aerogels, such as morphology, conductivity and magnetism. We are also looking into the adaptation of the gels into storage for renewable energy.