Synthetic approaches to nanoscale shape memory alloys (SMAs) and adhesion properties of composites derived from surface-modified SMAs.

摘要

Chapter 1: Introduction. Shape memory alloys (SMAs) are a unique type of material that can "remember" their shape upon deformation. A decrease in the physical size of these materials down to the nanoscale offers an opportunity to observe new and different behaviors. An introduction to the behaviors associated with SMAs, such as shape-memory an pseudoelasticity, is discussed using primarily nickel-titanium as an example. Additionally, Cuand Fe-based alloys exhibiting shape memory are discussed with the intent of introducing these systems as candidates for nanoscale work. Composite materials that include shape memory constituents are introduced.; Chapter 2: Copper-Tin SMAs. There are many Cu-based SMAs, including Cu-Al-Ni, Cu-Zn and Cu-Sn. Cu-Sn alloys were synthesized by different routes, with the intent of manufacturing the shape memory phase. While no shape memory behavior was observed, some interesting kinetic behavior was found, as well as a unique heterogeneous duplex structure associated with mixed Cu-Sn phases.; Chapter 3: Iron-Platinum SMAs. The Fe-Pt system exhibits shape memory behavior comparable to NiTi. It is not amenable to many of the applications currently employing NiTi because this system exhibits shape-memory behavior at sub-ambient temperatures. It does offer a good opportunity to synthesize nanoscale SMAs because there is a well-documented synthetic routine for nanoscale Fe-Pt compounds, which can potentially be modified to produce the shape memory phase.; Chapter 4: Adhesion for composite materials. Part 1: Adhesion Control. NiTi wires were functionalized with silane coupling agents to improve interfacial adhesion between a constituent and a matrix for composite applications. Surface derivatization was characterized by X-ray Photoelectron Spectroscopy (XPS), and mechanical pullout tests were performed to quantify the increase in adhesion between the NiTi shape memory alloy wires and polymer matrix. Improvements of roughly 100% in the adhesion was realized as compared to unfunctionalized samples or to samples functionalized with an unreactive silane coupling agent. Part 2: Nanocomposites. A composite material comprised of NiTi nanoparticles and a PMMA matrix was manufactured using the techniques described in part 1 of chapter 4. This type of composite has the possibility of exhibiting extreme vibrational damping properties.