Novel Approaches to the Surface Modification of Glass by Thermo-electric Poling

Open Access
Author:
Smith, Nicholas J
Graduate Program:
Materials Science and Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
April 04, 2011
Committee Members:
  • Carlo G Pantano, Dissertation Advisor
  • Carlo G Pantano, Committee Chair
  • Venkatraman Gopalan, Committee Member
  • Michael T Lanagan, Committee Member
  • Seong H Kim, Committee Member
Keywords:
  • thermal poling
  • surface
  • glass
Abstract:
Many new and emerging applications of glass rely critically on surface properties, and have led to an ever-increasing demand for methods to controllably modify glass surfaces as a pathway to enhanced properties. The genesis of this thesis arose from such pursuits, wherein the thermo-electric poling of glass—encompassing treatment with high voltage and blocking electrodes at moderate temperatures—was found to provide a fertile research area. Versatile in its application to a variety of glasses, as well as the diversity of phenomena it produces, several novel approaches to the thermo-electric treatments of multicomponent glass are carried out in this work. This included (1) poling to produce normally-forbidden, second-order nonlinearity in high breakdown strength glasses as a potential avenue to greater nonlinear coefficients; (2) capitalizing on poling-induced modifications toward the novel end of manipulating the observed breakdown strength of glass; and (3) venturing outside the “typical” parameter space of poling treatments in order to realize even greater modifications to surface composition and structure by electrolyzing the glass network. The primary outcome for the first study indicates that, contrary to the usual assumption, the stored internal field from poling is limited to a substantial fraction of the intrinsic breakdown strength, and seemingly in a broad range of glass systems. This is most likely due to nonlinear conduction effects at the high poling temperatures. Meanwhile, the results of the second study indicate that the observed breakdown strength of glass is minimally influenced by the presence of a stored space charge field, and is likely attributable to the presence of the modified surface layer concentrating the applied voltage. The results of the last study provide the most intriguing possibilities for extensive and stable surface modification. Applied to a model alkali-free glass, a nanoscale layer is formed adjacent to the anodic surface composed of essentially only network-forming elements, and whose formation is attributed to the electrolytic migration of both cationic and anionic species within the glass network. This technique has significant potential for creating novel surface structures and compositions, anticipated applicability to a wide variety of glass compositions, and extensively modified transport and corrosion-resistance properties.