Laser absorption spectroscopy for plasma-assisted thermochemical treatment. Part II.: Impact of the carbon and water contaminants on a low-pressure N<sub>2</sub>–H<sub>2</sub> discharge

Pipa, A. V.; Puth, Alexander; Böcker, Jan; Jafarpour, Saeed Motaragheb; Dalke, Anke; Biermann, Horst; Roepcke, J.; Helden, J. H. van

doi:10.1088/1361-6595/ace9f8

Cited by 3 publications

(3 citation statements)

References 29 publications

(39 reference statements)

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“…Finally, considering that absorption spectroscopy is a lineof-sight method with an integrating character, local heating in the active plasma region may be expected to induce a temperature gradient, in particular at high plasma powers. If this is the case, the measured absorption profiles, particularly their Doppler width, will respond differently to such a gradient based on whether the probed transitions are from a hot band or a fundamental band, or whether they are for high J or low J transitions [46][47][48]. For instance, higher J and hot band transitions are predicted to include more contribution from the hotter region in the reactor than the low J transitions of the fundamental band, as expected from the dependence of their spectral line intensity on temperature [40].…”

Section: Non-thermal Population Of Rovibrational Levels Of Hcnmentioning

confidence: 99%

Precision spectroscopy of non-thermal molecular plasmas using mid-infrared optical frequency comb Fourier transform spectroscopy

Sadiek,

Puth,

Kowzan

et al. 2024

Plasma Sources Sci. Technol.

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Non-thermal molecular plasmas play a crucial role in numerous industrial processes and hold significant potential for driving essential chemical transformations. Accurate information about the molecular composition of the plasmas and the distribution of populations among quantum states is essential for understanding and optimizing plasma processes. Here, we apply a mid-infrared frequency comb-based Fourier transform spectrometer to measure high-resolution spectra of plasmas containing hydrogen, nitrogen, and a carbon source in the 2800 – 3400 cm–1 range. The spectrally broadband and high-resolution capabilities of this technique enable quantum-state-resolved spectroscopy of multiple plasma-generated species simultaneously, including CH4, C2H2, C2H6, NH3, and HCN, providing detailed information beyond the limitations of current methods. Using a line-by-line fitting approach, we analyzed 548 resolved transitions across five vibrational bands of plasma-generated HCN. The results indicate a significant non-thermal distribution of the populations among the quantum states, with distinct temperatures observed for lower and higher rotational quantum numbers, with a temperature difference of about 62 K. Broadband state-resolved-spectroscopy via comb-based methods provides unprecedented fundamental insights into the non-thermal nature of molecular plasmas – a detailed picture that has never been accomplished before for such complex non-thermal environment.

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Section: Non-thermal Population Of Rovibrational Levels Of Hcnmentioning

confidence: 99%

Precision spectroscopy of non-thermal molecular plasmas using mid-infrared optical frequency comb Fourier transform spectroscopy

Sadiek,

Puth,

Kowzan

et al. 2024

Plasma Sources Sci. Technol.

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“…All data on the obtained densities are available at [48]. In part II [23], only averaged densities will be presented and their behavior on experimental parameters will be discussed.…”

Section: For Cold Lines S(296mentioning

confidence: 99%

“…The current manuscript focusses on the interpretation of the spectroscopic measurements and on obtaining species densities. The second manuscript [23] is devoted to the analysis of the time evolution of the densities for a better understanding of nitrocarburizing processes. Preliminary results of the work were reported in [24].…”

Section: Introductionmentioning

confidence: 99%

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

Pipa¹,

Puth²,

Böcker³

et al. 2023

Plasma Sources Sci. Technol.

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The work is devoted to the development of laser absorption spectroscopy (LAS) of plasma-assisted processes for application under industrial conditions. The interpretation of the LAS measurements was revised by taking into consideration the temperature gradient along the absorption path, which is unavoidable in a reactor for thermochemical treatment. The revision is based on the measurement of HCN, NH3, H2O and CO molecular lines in an industrial-scale, active screen plasma nitrocarburizing (ASPNC) reactor with a steel active screen (AS). It shows that an effective temperature determined from Doppler broadening could be assigned to each measured spectral line. The effective temperature does not only reflect the temperature gradients along the line-of-sight but also the line strength dependence on temperature for the specific spectroscopic transition. Lower limit estimates of the molecular densities are proposed based on the determined effective temperatures under the assumption of a Boltzmann distribution of the population density over the molecular levels at any local volume of the reactor. For a more accurate interpretation of LAS data of plasma-assisted processes, the spatial distribution of the temperature along line-of-sight has to be known and needs to be taken into account to obtain the molecular densities.

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New Approach for Plasma Nitrocarburizing of Stainless Steels by a Modified Reactor Configuration Using a Plasma‐Activated Solid Carbon Precursor

M. Jafarpour,

Dalke,

Biermann

2024

steel research int.

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Stainless steel surfaces can be modified using plasma‐assisted thermochemical treatments to improve properties like hardness, wear, and pitting corrosion resistance. To specifically adjust the desired properties, a precise control of the produced treatment‐relevant gas species with regard to their type and concentration is essential. This requires the adjustment of the parameters for the generation of the gas species, being independent from heating parameters, as well as their real‐time measurement. Therefore, this study presents the use of a plasma‐activated solid carbon precursor in a cold‐wall reactor using active screen technology and in a modified hot‐wall reactor during plasma nitrocarburizing of austenitic stainless steel. In addition, the modified hot‐wall reactor combined with a compact laser‐based absorption spectroscopy sensor for real‐time monitoring and concentration evaluation of in‐site generated gas species. It is shown that implementing a plasma‐activated solid carbon precursor in a modified hot‐wall reactor enables adjustable generation of C‐containing gas species, particularly HCN, with high production yield by an independent power management. Therefore, HCN is produced independent from heating while the limitations arising during active screen technology using a carbon screen are avoided. The presented technological development thus opens up new possibilities for better control of the plasma nitrocarburizing treatments of steels.

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Laser absorption spectroscopy for plasma-assisted thermochemical treatment. Part II.: Impact of the carbon and water contaminants on a low-pressure N₂–H₂ discharge

Cited by 3 publications

References 29 publications

Precision spectroscopy of non-thermal molecular plasmas using mid-infrared optical frequency comb Fourier transform spectroscopy

Precision spectroscopy of non-thermal molecular plasmas using mid-infrared optical frequency comb Fourier transform spectroscopy

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

New Approach for Plasma Nitrocarburizing of Stainless Steels by a Modified Reactor Configuration Using a Plasma‐Activated Solid Carbon Precursor

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Laser absorption spectroscopy for plasma-assisted thermochemical treatment. Part II.: Impact of the carbon and water contaminants on a low-pressure N2–H2 discharge

Cited by 3 publications

References 29 publications

Precision spectroscopy of non-thermal molecular plasmas using mid-infrared optical frequency comb Fourier transform spectroscopy

Precision spectroscopy of non-thermal molecular plasmas using mid-infrared optical frequency comb Fourier transform spectroscopy

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

New Approach for Plasma Nitrocarburizing of Stainless Steels by a Modified Reactor Configuration Using a Plasma‐Activated Solid Carbon Precursor

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Product

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Laser absorption spectroscopy for plasma-assisted thermochemical treatment. Part II.: Impact of the carbon and water contaminants on a low-pressure N₂–H₂ discharge