Near cathode optical emission spectroscopy in N2–H2 glow discharge plasma

Suraj, K.S.; Bharathi, P.; Prahlad, V.; Mukherjee, S.

doi:10.1016/j.surfcoat.2007.05.063

Cited by 38 publications

(17 citation statements)

References 31 publications

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“…Sufficiently energized electrons collide with N 2(g) and H 2(g) to dissociate them into gas phase atomic N and H species, respectively (Reactions A−B). Given the relative N≡N and H−H bond energies, and our 1 : 4N 2 : H 2 ratio for the reactor feed, we expect atomic H to be much more abundant than atomic N. Other collisions may lead to ionic and excited molecular species, which have been reported in literature for both radiofrequency and glow discharge

true N_{2 ((), g)} + e^{-} \to 2 N_{(g)} + e^{-}

true H_{2 ((), g)} + e^{-} \to 2 H_{(g)} + e^{-}

…”

Section: Resultsmentioning

confidence: 55%

Enhancement of the Yield of Ammonia by Hydrogen‐Sink Effect during Plasma Catalysis

et al. 2019

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Plasma‐catalytic ammonia synthesis has been known since the early 1900s, but only until now efforts to optimize catalysts for this purpose are emerging. Here, we investigate various transition metals, low‐melting‐point metals, and gallium‐rich alloy catalysts for their activity towards ammonia production under a plasma environment. The best three pure metal catalysts were Ni, Sn and Au, which are not traditional catalysts for the current industrial ammonia synthesis. The ammonia yields for these catalysts were 34 %, 29 %, and 19 %, respectively. Synergistic effects were detected when employing alloys, as some alloys presented ∼25–50 % higher yields than their constituent metals. The employed metals were classified into two categories. Category I metals (Cu, Ag, Au and Fe), which are nitrophobic (excluding Fe, the Haber‐Bosch catalyst) and poor hydrogen sinks. For these metals, the measured concentration of Hα in the gas phase tended to correlate inversely with ammonia yield and directly with the H binding strength on the catalyst surface. Category II metals (Ga, In, Sn and Ni), which are good hydrogen sinks, tend to have a lower concentration of Hα in the gas phase than that of category I metals, which is consistent with their expected sink behavior. For these metals, the concentration of Hα correlates with ammonia yield. Plasma characterization experiments and DFT calculations suggest that the higher performance of Ni and Sn is related to the benefit of dissolving hydrogen to slow down H recombination, which is a feature that could be potentially optimized in future studies by rationally altering the catalyst composition.

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true N_{2 ((), g)} + e^{-} \to 2 N_{(g)} + e^{-}

true H_{2 ((), g)} + e^{-} \to 2 H_{(g)} + e^{-}

…”

Section: Resultsmentioning

confidence: 55%

Enhancement of the Yield of Ammonia by Hydrogen‐Sink Effect during Plasma Catalysis

et al. 2019

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“…Thus, the differences in the observed spectra at different locations are only due to different governing mechanisms occurring at different regions. 35 When the MOP is positioned very near to the cathode, i.e., inside the cathode fall, it collects emissions coming from the vicinity of the cathode and excludes the emissions from negative glow and positive column. For our discharge parameters, the approximate sheath thickness is ϳ10 mm.…”

Section: A Experimental Setupmentioning

confidence: 99%

“…Barbeu and Jolly 3 used these experimentally observed ion distributions obtained by Dexter et al for calculating the number of excited neutrals in n = 3 state ͓N H ͑n =3͔͒. Our approach here is to use a recently proposed and experimentally verified model by Suraj et al 26,35,36 for the nitrogen discharges and extend the same to the hydrogen discharge for estimating the mean energies, mean velocities, and ion concentrations for our dis-charge conditions. In what follows, a brief description of the model is given and all the calculations are presented.…”

Section: A Velocity Distribution Of H + H 2 + and H 3 +mentioning

confidence: 99%

Signature of fast H atoms from cathode glow region of a dc discharge

et al. 2009

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Asymmetric broadening of H ␣ line from cathode glow region has been studied. In the cathode glow, mean energy and fractional population of very fast hydrogen atoms were found to be ϳ130 eV and ϳ55%, respectively. These values reduced to ϳ90 eV and ϳ20% when measured at negative glow region. The observed asymmetry was attributed to the presence of the fast hydrogen atoms near the cathode surface. The mean energy and number density of excited fast hydrogen atoms were estimated from the velocity distribution of H + , H 2 + , and H 3 + considering collisions inside the cathode sheath. The reduction in the mean energy and number density of the excited fast hydrogen atoms, at the other locations of the discharge, was explained by energy relaxation and thermalization of the neutrals with the background gas.

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“…This fact was confirmed by different research groups dealing with plasma diagnostics. 15 An increase in the bias power leads to a decreasing shift of the I-V curve. The application of bias power or change of the process temperature at a fixed H 2 /N 2 gas ratio leads immediately to a self-adjustment of the AS power (see Figs.…”

Section: Resultsmentioning

confidence: 99%

Progress in control of nitriding potential in ASPN process

Burlacov

Börner

Spies

et al. 2014

International Heat Treatment and Surface Engineering

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A novel active screen plasma nitriding (ASPN) process provided excellent temperature homogeneity in the load and showed further progress in the control of nitriding potential. In addition to a variation of the nitrogen partial pressure in the process gas commonly used in the conventional plasma nitriding, the applied bias power strongly impacted the nitriding results. In the present work, an application of both methods for the control of nitriding potential in the ASPN process was systematically investigated for a wide range of process parameters to meet the treatment requirements for different types of engineering steel. A two-stage technique based on proper choice of process temperature and required nitriding potential in each stage has been applied in the ASPN process to avoid unnecessary compromises between sufficient thickness of the compound layer, the maximum case hardness and the acceptable nitriding hardness depth.

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Near cathode optical emission spectroscopy in N2–H2 glow discharge plasma

Cited by 38 publications

References 31 publications

Enhancement of the Yield of Ammonia by Hydrogen‐Sink Effect during Plasma Catalysis

Enhancement of the Yield of Ammonia by Hydrogen‐Sink Effect during Plasma Catalysis

Signature of fast H atoms from cathode glow region of a dc discharge

Progress in control of nitriding potential in ASPN process

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