The simulation of carbon material structure based on polyacrylonitrile obtained under IR heating

Abstract

Since recently an economically efficient method including IR heating has been used for the synthesis of polymer based functional carbon nanocrystalline materials. One of the most widely used polymers having a broadest range of physicochemical properties and various applications is polyacrylonitrile (PAN). Under IR heating PAN undergoes chemical and structural transformations and a polyconjugated system forms with an increase in heating intensity. However, there are still no data on the quantitative and qualitative effects of carbon, nitrogen, hydrogen or metal atoms on the structural stability and configuration of the PAN based carbon material. We have for the first time determined using the MNDO semiempirical quantum chemical model for a carbon material (CM) structure based on heat treated polyacrylonitrile (PAN) that an increase in the N content from 14 to 18 atoms in CM monoatomic layers C46N14H10, C44N16H12, and C42N18H14 and in the H content from 12 to 22 atoms in CM monoatomic layers C44N16H12 and C44N16H22 leads to a decrease in the binding energy (Eb) from 7.40 and 7.12 to 6.88 and 6.25 eV, respectively, and to an increase in the difference between the maximum and minimum bond length (Δl), between the maximum and minimum valence angle (Δθ), and between the maximum and minimum local charge (Δq) from 0.176 Е, 12.0°, and 0.487 to 0.238 Е, 20.8°, and 0.613, respectively, and promotes curving of the CM structure. Quantum chemical simulation results are confirmed by the element analysis of the CM specimens and FeNi3/C nanocomposite. When the IR heating temperature was increased from 30 to 500 °С, the concentrations of N (СN) and H (СH) in the CM and in the FeNi3/C nanocomposite decreased from 27 to 18 and 10 wt% and from 6 to 1 and 0.5 wt%, respectively.

Keywords

• Polyacrylonitrile
• Simulation
• Structure
• Heating
• Nitrogen
• Carbon