Structure Simulation of Synthesized Nitrogen-Containing Graphite-Like Materials

Abstract

Results are reported about the molecular mechanics simulation of the structures of carbon–nitrogen solid solutions obtained by pyrolysis of a molten mixture of melamine with 50-100 wt.% high-temperature coal-tar pitch upon their slow heating to 500 °C. It is shown experimentally that the electrical conductivity of the solid solutions formed increases by several orders of magnitude with an increase in the nitrogen concentration from 0.4 wt.% to 22 wt.%. Structure simulation is the research stage required for understanding the conductivity mechanism. Starting data for the simulation are elemental, powder X-ray diffraction, pycnometric, simultaneous thermal analysis, infrared (IR) and X-ray photoelectron spectroscopy (XPS) results obtained for the materials under study. Apart from nitrogen and carbon atoms, hydrogen and oxygen atoms are present in the samples, which is explained by the presence of these elements in the initial components. According to XPS and Raman spectroscopy data, the materials have the graphite-like structure with carbon atoms that are mainly in the sp² hybridization state. The occurrence of four nitrogen atoms with different environments is detected by the XPS technique: graphite-, pyridine-, and pyrrole-like, and oxidized. The thermal analysis data support the conclusion about the absence of triazine islands in the samples prepared from mixtures with 80-100 wt.% coal-tar pitch and about their presence in the samples with 50-70 wt.% coal-tar pitch. The IR spectroscopic data confirm the absence of amino and cyano groups in all solid solutions. Based on the available experimental data, structure models are proposed for the materials studied, and common structural patterns are found.