Improved Graphite Materials for High-Temperature Aerospace Use. Volume III. Further Research and Development for Improved Graphite Materials.

摘要

The pyrolysis mechanisms and thermal reactivity of aromatic and heterocyclic compounds are appreciably modified by substitution with nitrogen-, oxygen-, and halogen-containing groups. Aromatic nucleii with strongly activating side groups generally lead to a disordered graphitic structure. The hydrocarbons which yield well-ordered graphites consist largely of fused planar aromatic compounds. The complex mixtures of aromatic compounds that make up the normal raw materials for carbon and graphite form highly-ordered graphites. Pyrolysis studies have been performed for eleven model aromatic hydrocarbons and for two oxygenated aromatics. The planarity of the condensation products of the initial free radical intermediates determines the degree of ordering of the resulting graphite. Electron spin resonance studies indicate that free radical intermediates may play an important role in the acid catalyzed rearrangements of methyl benzenes. Aromatic hydrocarbons and related heterocyclic compounds with two to four rings which produce no residue at atmospheric pressure have been thermally polymerized at super-atmospheric pressures. Graphite bodies have been fabricated using coke filler material prepared by pyrolysis of selected model aromatic compounds. The physical properties of the fabricated bodies are stongly influenced by the molecular structure of the starting compounds.