Modelling the discharge region of a microwave generated hydrogen plasma

Chen, Chun-Ku; Wei, Ta‐Chin; Collins, Lance R.; Phillips, Jonathan

doi:10.1088/0022-3727/32/6/015

Cited by 53 publications

(74 citation statements)

References 62 publications

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“…This phenomenon is not observed in discharges of pure noble gases [3,5,10,[31][32][33]. In the case of the production of fast H, the intensity may be low due to efficient collisional energy exchange with molecular hydrogen with dissociative excitation [34]. In a glow discharge, fast H is formed and excited predominantly near the electrode surfaces.…”

Section: Discussionmentioning

confidence: 98%

Evidence of catalytic production of hot hydrogen in RF generated hydrogen/argon plasmas

Phillips

Chen

Akhtar

et al. 2007

International Journal of Hydrogen Energy

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This is the third in a series of papers by our team on apparently anomalous Balmer series line broadening in hydrogen containing RF generated, low pressure (< 600 mTorr) plasmas. In this paper the selective broadening of the atomic hydrogen lines in pure H 2 and Ar/H 2 mixtures in a large 'GEC' cell (36 cm length × 14 cm ID) was mapped as a function of position, H 2 /Ar ratio, time, power, and pressure. Several observations regarding the selective line broadening were particularly notable as they are unanticipated on the basis of earlier models. First, the anomalous broadening of the Balmer lines was found to exist throughout the plasma, and not just in the region between the electrodes. Second, the broadening was consistently a complex function of the operating parameters particularly gas composition (highest in pure H 2 ), position, power, time and pressure. Clearly not anticipated by earlier models were the findings that under some conditions the highest concentration of 'hot' (>10 eV) hydrogen was found at the entry end, and not in the high field region between the electrodes and that in other conditions, the hottest H was at the (exit) pump (also grounded electrode) end. Third, excitation and electron temperatures were less than one eV in all regions of the plasma not directly adjacent (>1mm) to the electrodes, a Corresponding author: phone 505-665-2682; fax 505-665-5548 jphillips@LanL.gov 2 providing additional evidence that the energy for broadening, contrary to standard models, is not obtained from the field. Fourth, in contrast to our earlier studies of hydrogen/helium and water plasmas, we found that in some conditions 98% of the atomic hydrogen was in the 'hot' state throughout the GEC-type cell. Virtually every operating parameter studied impacted the character of the hot H atom population, and clearly second and third order effects exist, indicating a need for experimental design. Some non-field mechanisms for generating hot hydrogen atoms, specifically those suggested by Mills' CQM model, are outlined.3

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Section: Discussionmentioning

confidence: 98%

Evidence of catalytic production of hot hydrogen in RF generated hydrogen/argon plasmas

Phillips

Chen

Akhtar

et al. 2007

International Journal of Hydrogen Energy

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“…Bolsig software (Wei et al, 2000;Chen et al, 1999) can find the electron energy distribution function (EEDF) and the energy consumption of unit electrons at different types of collision reactions, as well as the collision frequency at different E/N values.…”

Section: Charged Species Modelmentioning

confidence: 99%

Reaction Mechanism of Ethylene Oxide at Various Oxygen/Ethylene Oxide Ratios in an RF Cold Plasma Environment

Liao

Wei

Hsieh

et al. 2005

Aerosol Air Qual. Res.

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An innovative method was used to simulate ethylene oxide (EO) oxidation in an RF plasma reactor. The objective of this work was to simulate the stable species mole fraction profiles measured in a flowing plasma system at constant temperature and pressure. The mechanism involved participation of 36 species in 140 elementary reactions. Sensitivity analysis was also performed to identify the order of significance of reactions in the mechanism of the model' s predictions. The results show that the main reactions for EO decomposition changed with a varying O 2 /EO ratio in the plasma system. That is to say, the most important reaction to the O 2 /EO ratio of zero was the electron dissociation reaction of EO, C 2 H 4 O + e- CH 3 CHO + e-. While, the most influential reaction for EO decomposition at O 2 /EO ratio of 5.0 was the formation reaction of HO 2 , which forms OH radicals, then enhances the decomposition of C 2 H 4 O by the reaction, C 2 H 4 O + OH = C 2 H 3 O + H 2 O.

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“…Given the rapid cooling this suggests the aerosol particles encounter temperatures greater than 4000 C in the 'hot zone'. Even the best ovens are perhaps able to reach 2500 C. Second, in the microwave plasma there are actually two temperatures, that of the neutral species discussed above, and that of the charged species, which in this system has been measured to be as high as 80,000 C. As discussed elsewhere, these two 'systems' co-exist in the same space, and exchange energy through 'generation terms' [17,18]. Clearly the plasma found in the microwave system is far from equilibrium.…”

Section: Resultsmentioning

confidence: 84%

Production of unique structures using the Aerosol-Through-Plasma (A-T-P) process

Luhrs¹,

Phillips²,

Fanson³

2008

WIT Transactions on the Built Environment

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Nanoparticle applications for batteries, fuel cells, catalysts and specialty solid fuels, etc, require not simply nanoparticles, but highly engineered nanoparticles. The engineering of chemicals, including particles, requires a thorough, mathematical understanding of processes. Yet, the generation of nano-structures often requires novel processes for material generation that cannot be modeled using existing approaches. In our work we have produced a number of novel nano-structured ceramic structures using an atmospheric pressure microwave through which an aerosol containing precursor species is passed, a technique we call 'Aerosol-Through-Plasma' (A-T-P). For example, ceria-alumina particles of a wide variety of structures, from micron sized hollow spheres to nanoparticles, were produced. In many cases structures are produced that are 'impossible' according to aerosol theory. Examples include the production of nanoparticles from dry, micron scale precursor powders, and the formation of hollow particles from dry precursors. These results and others indicate the need for a new model of particle formation using the A-T-P process. An accurate model can accelerate the engineering of the process to commercial scale.

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Modelling the discharge region of a microwave generated hydrogen plasma

Cited by 53 publications

References 62 publications

Evidence of catalytic production of hot hydrogen in RF generated hydrogen/argon plasmas

Evidence of catalytic production of hot hydrogen in RF generated hydrogen/argon plasmas

Reaction Mechanism of Ethylene Oxide at Various Oxygen/Ethylene Oxide Ratios in an RF Cold Plasma Environment

Production of unique structures using the Aerosol-Through-Plasma (A-T-P) process

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