Microstructure Of Thin NiTi Films On Carbon Fibre Materials

Coating single carbon fibres with NiTi is an alternative approach for the fabrication of functional materials, in particular when sensor rather than actuator capabilities are of interest. The present study explores how thin NiTi films can be coated on single carbon fibres. We deposited NiTi thin films in the range of 2 to 4 microns on single carbon fibre substrates (diameter 8 microns) using a PVD magnetron sputter process followed by an annealing treatment at 550 °C. The phase transition behavior and microstructures were characterized by X-ray diffraction (XRD), electron microscopy (SEM) and nanoindentation. To improve the metal layer adhesion on carbon fibre materials, we investigated different metallic interlayers in our system. While an electroplated nickel interlayer did not improve the interface stability, we observed good adhesion of the metal layer system after sputter deposition of titanium interlayer. In this study, we also compare the shape memory characteristics of the thin NiTi films with those of NiTi wires of similar size, and we discuss how the different materials and additional processing parameters affect the formation and properties of NiTi thin films.