Abstract: The conversion of atmospheric nitrogen into valuable compounds, that is, so-called nitrogen fixation, is gaining increased interest, owing to the essential role in the nitrogen cycle of the biosphere. Plasma technology, and more specifically gliding arc plasma, has great potential in this area, but little is known about the underlying mechanisms. Therefore, we developed a detailed chemical kinetics model for a pulsed-power gliding-arc reactor operating at atmospheric pressure for nitrogen oxide synthesis. Experiments are performed to validate the model and reasonable agreement is reached between the calculated and measured NO and NO2 yields and the corresponding energy efficiency for NOx formation for different N2/O2 ratios, indicating that the model can provide a realistic picture of the plasma chemistry. Therefore, we can use the model to investigate the reaction pathways for the formation and loss of NOx. The results indicate that vibrational excitation of N2 in the gliding arc contributes significantly to activating the N2 molecules, and leads to an energy efficient way of NOx production, compared to the thermal process. Based on the underlying chemistry, the model allows us to propose solutions on how to further improve the NOx formation by gliding arc technology. Although the energy efficiency of the gliding-arc-based nitrogen fixation process at the present stage is not comparable to the world-scale HaberBosch process, we believe our study helps us to come up with more realistic scenarios of entering a cutting-edge innovation in new business cases for the decentralised production of fertilisers for agriculture, in which low-temperature plasma technology might play an important role.

Abstract: Exfoliated graphite samples (EG) with different bulk densities were prepared by the exfoliation of expandable graphite under a thermal shock regime. As a conductive filler, EG has been incorporated successfully into the coal tar pitch matrix by mechanical mixing. The conducting behavior of the composite was interpreted based on the percolation theory. The percolation threshold of the EG/pitch conducting composites at room temperature was as low as 1.5 wt% and did not depend on the bulk density of the EG used. By means of thermogravimetry the improvement of thermal stability of the composites in comparison with pure pitches was detected. The phenomenon was ascribed to heat shielding effect of the EG particles evidenced by matrix-assisted laser desorption/ionization mass spectrometry.