| AVS 61st International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Monday Sessions |
| Session NS+SE-MoM |
| Session: | Delivering Energy and Mass at the Nanoscale |
| Presenter: | Nancy Burnham, Worcester Polytechnic Institute |
| Authors: | X. Yu, Worcester Polytechnic Institute M. Tao, Worcester Polytechnic Institute N.A. Burnham, Worcester Polytechnic Institute |
| Correspondent: | Click to Email |
Viscoelastic materials are engineered and used in a variety of applications; however, it has been a great challenge to characterize their viscoelasticity at the nanoscale, at which the degradation and failure mechanisms often initiate. For linear viscoelastic materials, an atomic force microscopic (AFM) technique, loss-tangent mode, has been recently developed to fulfill this need [1]. The loss tangent of a material is expressed as the ratio of the lost energy (damping) over the stored energy (stiffness) and is claimed to be independent of the tip-sample contact area. Since this new mode was invented, only a few example materials have been studied. In this project, viscoelasticity of several different materials (i.e., asphalt binders [2], epoxy, silica tire, and graphite) were investigated using loss-tangent mode; the damping and stiffness terms were derived with easily measurable terms for a more detailed understanding of materials’ viscoelasticity.
Results show that both free amplitude and set-point ratio affect the loss-tangent measurement. For all the examined materials, the loss tangent and damping decreased (power laws of -2.4 ± 1.1 and -2.1 ± 1.0, respectively) with increasing free amplitude at constant set-point ratio, while stiffness increased (power law 0.32 ± 0.18). The loss tangent increased (power law 0.8 ± 0.5) with increasing set-point ratio at constant free amplitude; stiffness decreased more rapidly than damping (power laws of -1.75 ± 0.06 and -1.0 ± 0.4, respectively). These trends might indicate that the loss tangent, as measured by AFM, is not independent of the tip-sample contact area. Computer simulation of loss-tangent mode is ongoing for explanation of these observations, in order to advance understanding of nanoscale viscoelastic measurements.
1. R. Proksch and D.G. Yablon, Appl. Phys. Lett. 100, 073106 (2012)
2. X. Yu, N.A. Burnham, R.B. Mallick, M. Tao, Fuel 113, 443 (2013)