Synthesis of Carbon Materials via the Cold Compression of Aromatic Molecules and Carbon Nanostructures

Open Access
Author:
Fitzgibbons, Thomas Christopher
Graduate Program:
Chemistry
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 10, 2014
Committee Members:
  • John V Badding, Dissertation Advisor
  • John V Badding, Committee Chair
  • Ayusman Sen, Committee Member
  • Albert Welford Castleman Jr., Committee Member
  • William Blaine White, Special Member
Keywords:
  • Chemistry
  • Carbon
  • High Pressure
  • Solid-State
  • Aromatic
Abstract:
Carbon’s ability for catenation makes it a remarkable element and allows for many interesting and surprising properties and structures. Carbon can exist in one of its two thermodynamically stable bulk crystals, graphite or diamond, one of its several nanostructures: fullerene, nanotube, or graphene, or as an amorphous material with a mixed bonding pattern. Carbon also has an ability to bond heteroatoms such as hydrogen which can increase its properties and structures even further. Pressure has been shown to be able to drastically change the bonding in and structure of carbon based materials. In this dissertation I will present how pressure can be used to synthesize new amorphous hydrogenated carbons and how a battery of analytical techniques can be used to elicit the microstructure of the carbon networks. This microstructure can then be related back to the reaction conditions and more importantly the starting small molecule. This work has been expanded to looking for a molecular analogue to the cold compressed graphite system by investigating the high pressure stability and reactivity of 2-D polycyclic aromatic hydrocarbons. This work was followed by discovering the failure of Single Walled Carbon Nanotubes at high static pressures. When the tubes fail they transform into nano-graphitic polyhedra. It has been found that metallic tubes preferentially collapse, leaving the semiconducting tubes intact for the most part. Finally, the most influential work performed in my dissertation has been related to the kinetically controlled solid state reaction of molecular benzene to form diamond nanothreads. These nanothreads pack into hexagonal bundles without axial order. A combination of Raman spectroscopy, x-ray and neutron scattering, transmission electron microscopy, and first principles calculations were performed to confirm their existence. The three data chapters in this dissertation are enhanced by an introduction to carbon based materials and high pressure chemistry in chapter 1, an overview of the advanced and sometimes unconventional characterization techniques used throughout the dissertation in chapter 2, and some concluding remarks and future directions for this research in chapter 6.