A physical approach to boundary conditions for the characterization of 1-D nanomaterials


Gangadean, Devananda.. (2009). A physical approach to boundary conditions for the characterization of 1-D nanomaterials. Theses and Dissertations Collection, University of Idaho Library Digital Collections.

A physical approach to boundary conditions for the characterization of 1-D nanomaterials
Gangadean, Devananda.
Nanostructured materials
The production of sub-micron structures has created a need for techniques to characterize these structures. This is especially true since many of the materials composing these structures do not behave as would be predicted by traditional meso-scale equations. This paper considers both experimental and theoretical aspects of the three-point bending method for measuring the elastic modulus of 1-D nanostructures such as wires, tubes, and belts. Three-point bending tests were performed using an atomic force microscope (AFM) on silica nanowires suspended over micro-channels. Detailed consideration was given to AFM calibration, measurement uncertainty, and the importance of the boundary conditions existing where the wires are anchored to the test structure. Correct representation of the boundary conditions is critical for the use of models with the observed data to estimate the elastic modulus. The standard fixed and simple beam models have been used exclusively for estimating the elastic modulus, despite their unrealistic representation of boundary conditions. The Winkler model is applied here to represent an elastic bond between the nanowires and the polymer film anchoring them to the test structure. The application of this model requires measurement of the elastic modulus of the polymer, which was accomplished in this study via indentation testing with an AFM probe. The results clearly indicate that the silica nanowires in this study, with diameters between 50 and 130 nm, have an apparent elastic modulus greater than bulk. The results suggest that the apparent elastic modulus increases with smaller diameters in a way consistent with predictions made through the consideration of energy stored in the nanowires in the form of surface tension.
Thesis (Ph. D., Physics)--University of Idaho, May 11, 2009.
Major Professor:
David N. McIlroy.
Defense Date:
May 11, 2009.
Format Original:
xvii, 212 leaves :ill. ;29 cm.

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