Doctor of Philosophy (PhD)
Department of Chemistry
Silica nanoparticles are widely used as additives in polymer manufacturing to increase the strength and mechanical properties of the polymer. Silica nanoparticles typically exhibit a hierarchy of particle size distributions, whose structures are of critical importance to this reinforcement effect. Therefore, this work examines these distributions and structures using small angle x-ray scattering, which allows for characterization of several orders of length scales. First, silica nanoparticles are extensively studied as pure powder and as dispersions. Nanocomposites composed of silica nanoparticles and polydimethylsiloxane are also investigated to characterize their morphology in the undeformed state. Raster scans of the nanocomposite sheets showed negligible changes in the scattering at small length scales, but experiments using ultra small angle x-ray scattering, expanding the measured region to larger length scales of the agglomerates, showed inhomogeneity between different positions on the same sample. Further experiments were completed using in-situ tensile testing combined with X-ray scattering to see how external deformations at the macroscopic length scale affect the internal, microscopic structure of the nanocomposites. Additionally, the transmission of X-rays and visible light, from a laser source, through these samples were measured simultaneously with deformation to examine the relationship between them.
Van Leeuwen, Christopher John, "Influence of Mechanical Stress on Silica Particle Distributions in Polymers" (2023). LSU Doctoral Dissertations. 6174.
Schneider, Gerald J.
Available for download on Tuesday, May 21, 2030