Laboratory Investigation of Active Graphite Nitridation By Atomic Nitrogen

Abstract

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.