Dynamic methods for characterization of mechanical properties of nanomaterials

Knowledge of material properties at the nanoscale is essential for the development of many new materials and devices with applications to various areas of nanotechnology. One of the intrinsic properties of a material is the Young’s modulus; however the elastic modulus of a material at the nanoscale level is expected to be quite different from that of a bulk material. The small size of nanostructures constrains the applications of well-established testing and measurement techniques. Therefore new measurement tools and techniques are required for determining material properties at the nanoscale. The objective of the research in this dissertation is to develop new techniques for the characterization of the mechanical properties of materials at both the micro and nanoscales. First, a method for measuring the Young’s modulus of a single electrospun nanofiber using the vibrations of two microcantilevers coupled with the nanofiber has been developed and used to determine the Young’s modulus of a polyacrylonitrile (PAN) nanofiber. Second, a theoretical model for contact resonance atomic force microscopy for viscoelasticity has been developed that will enable the accurate modeling of the AFM tip-sample interaction in viscoelastic contact. Experimental data is presented to validate and illustrate this technique. The last objective of the research used nanoindentation to determine creep compliance functions of viscoelastic samples and also to determine the effect of thin film thickness on the materials properties measured by nanoindentation. Finally, the modulus mapping technique is used to determine mechanical properties of heterogeneous samples. It is anticipated that the techniques developed will aid in the research and development of nanomaterials for various applications