Surfactant Modified Nickel-Manganese-Gallium Powder and Silicone Composites

Power supplies are often the limiting factor for operation of many portable electronic devices. Batteries contribute significantly to their weight and impose limitations on operational longevity. Harvesting vibratory energy from the environment for conversion to electrical energy has been proposed as a means to address these problems. Previously, DRDC Atlantic has shown that single crystals of nickel-manganese-gallium (NiMnGa) can produce large reversible stressinduced and magnetic field-induced strains of up to 10%. It has been proposed that NiMnGa magnetic shape memory alloys may be an ideal alloy to harvest mechanical energy. The drawback to monolithic NiMnGa crystals is that they are susceptible to intergranular fracture. To address this issue, a composite of the alloy in a polymer matrix has been examined in the hopes of improving toughness and formability. Good bonding between the polymer and the powder is needed to facilitate optimum transfer of force between the two components. The objective of this study was to understand and optimize the polymer-alloy interactions. The polymer matrix chosen was Dow Corning Sylgard 186. It was determined that the Sylgard 186 prepolymer base interacts with the oxidized surface of the NiMnGa particles. Silane coupling agents were also investigated to examine their effect on the interfacial interactions. No change in properties were observed.