Zhang, L., Pejakovic, D., Marschall, J., & Fletcher, D. (2009). Laboratory investigation of active graphite nitridation by atomic nitrogen. In 41st AIAA Thermophysics Conference (p. 4251).
The reaction efficiency for the active nitration of graphite by atomic nitrogen was investigated using a furnace-heated quartz flow tube coupled to a microwave discharge. Experiments were performed in N/N2 mixtures with gas pressures ranging from about 1 to 5 Torr and furnace temperatures from 873 to 1273K. The N-atom concentrations entering and exiting the furnace were determined using a chemical titration technique based on the rapid reaction N +NO –>O+N2. Emission spectroscopy and mass spectrometry were used to identify the titration endpoints, and the N-atom concentration at the graphite sample location was interpolated using a simple reactive-flow model. The reaction efficiency for graphite nitration was determined from the interpolated N-atom concentration and the measured graphite mass loss for a given test time. The reaction efficiency( defined as the fraction of N-atom collisions with the surface that result in the title reaction) was found to increase from ~0.2×10-3 at 873 K to ~ 9.8×10-3 at 1373 K.