Mass Spectrometry Study of Ammonia Formed During Plasma Nitrocarburizing and Nitriding Processes

Abstract

In this work, we used mass spectrometry to investigate ammonia (NH 3) formed during the nitrocarburizing and nitriding processes of α-Fe sintered and low alloy steel by using d.c. glow discharges in different N 2 /H 2 /CH 4 gas concentration mixtures. Experiments were conducted using two different configurations: one to collect and analyze species probed primarily in the bulk of the plasma, at a position distant from the heated sample; and the other to collect and analyze species very close to the reactive surface of the heated sample in such a way as to allow the analysis of lower concentration or residence time species, formed at the plasma/sample surface interface. Use of these configurations contributed to the investigation of the physical chemistry involved in the above plasma processes. An exchange the expected stoichiometry in ammonia formation in N 2 /H 2 /CH 4 mixtures, with a shift towards higher nitrogen consumption, is observed and is interpreted an indication of nitrogen removal from the surface associated with ammonia and carbonitrides/nitrides formation. The present results point to the existence of a correlation between the nitrocarburizing and nitriding processes with respect to the formation of non-stoichiometric ammonia as a product.

An approach to study electron and positron scattering from NH3 and PH3 using the analytic static potential

“…In figure 1(a), the atoms N, H1, H2 and H3 are located, respectively at (0, 0, 0.114 49), (0, 0.9377, −0.267 14), (−0.8121, −0.4689, −0.267 14) and (0.8121, −0.4689, −0.267 14), while the respective coordinates of P, H1, H2 and H3 atoms are (0, 0, 0.128 62), (0, 1.1932, −0.6431), (−1.0333, −0.5966, −0.6431), (1.0333, −0.5966, −0.6431). The product of the wave functions of the hydrogen atoms with the atom X (N or P) gives rise to a product vector r P as defined in equation (7). We need to rotate the r P frame through Euler angles (α, β, γ) so that both the r P and molecular frames (x, y, z) coincide.…”

“…Both the molecules have important applications in several areas of science. For example, electron impact scattering cross sections on ammonia are required in chemical industries for plasma catalysis applications [6] where NH 3 is widely used as a source of nitrogen atoms and also to fabricate the nitride films as well as other nitrogen compounds [7]. Besides the plasma applications, ammonia is an important source of nitrogen in living bodies and the basic building blocks of protein.…”

Laser absorption spectroscopy for plasma-assisted thermochemical treatment. Part I.: Applicability of the Beer–Lambert law and interpretation of spectroscopic data

“…Monitoring the composition of the discharge is important for the process control and optimization as well as for understanding of the chemical kinetics. Three approaches are broadly reported: optical emission spectroscopy (OES) [2,10,11], mass spectrometry (MS) [12][13][14] and laser absorption spectroscopy (LAS) [1,3,10,[15][16][17][18][19][20]. OES monitors exclusively electronically excited species and quantitative interpretation of OES data requires complex collisional-radiative models.…”

The Effects of Modifying the Activity of Nitriding Media by Diluting Ammonia with Nitrogen

“…The analysis of the equilibrium in the Fe-N system allows obtaining information regarding the phase composition of the nitrided layers obtained under strict conditions of temperature and nitrogen concentration in the furnace chamber atmosphere [ 1 , 2 , 3 , 4 , 5 ]. The adjustment of the nitrided layer phase composition can be set by altering the nitrogen potential of the atmospheres used: by maintaining it at the level of nitrogen solubility in a certain phase, one is able to control the phase composition of the layer [ 6 , 7 , 8 , 9 , 10 , 11 ].…”