Nitinol (NiTi) nanoparticles, which are a fifty-fifty metal alloy of nickel and titanium, are valued because of their corrosion resistance and superelasticity. NiTi is best known for its shape memory, as the bulk metal can physically change shape when transitioned by heat or pressure between the austenite and martensite forms. NiTi has potential in biomedical tools, nanofluids, and nickel alkaline batteries. To be able to utilize the NiTi nanoparticles, the surface requires modification, specifically by phosphonic acids. The metal oxide surface readily adheres to these acids, forming self-assembled alkylphosphonate films. In this study, phosphonic acids, including 16-phosphonohexadecanoic acid, octadecylphosphonic acid, and 12-aminododecylphosphonic acid were used to form an ordered self-assembled monolayers on the NiTi nanopowder. These surface modifications could be used in the preparation of nanofluids in order to improve their suspension. NiTi nanofluids have the ability to change electrical and thermal conductivity at the transition temperature, producing a smart nanofluid. The modified NiTi nanoparticles were then characterized using attenuated total reflectance infrared spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, cyclic voltammetry, electrical impedance spectroscopy, and <sup>31</sup>P solid-state nuclear magnetic resonance. Stability testing were performed on the NiTi nanoparticles to examine the effects of solvent rinse, humidity, and temperature over time. Isoelectric point of NiTi was also determined by analyzing zeta potential of NiTi at varying pH values. Based on spectroscopic data, the phosphonic head group is expected to adsorb in a mixed bidentate/monodentate binding motif at the surface of the NiTi nanoparticles. This allows the NiTi nanoparticles to be modified in order to provide the ideal physical and chemical properties for a variety of applications.

Modification of nitinol nanoparticles with self-assembled alkylphosphonate films

253rd National Meeting (2017)

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