Radiative properties of argon–helium–nitrogen–carbon–cobalt–nickel plasmas used in CNT synthesis

Visualisation of alternating shielding gas flow in GTAW

“…The nozzle has been delineated in the first frame to distinguish it from a large dark region in the schlieren image. The net emission coefficient of helium is an order of magnitude lower than that of argon [24]. Therefore, in the 'hot' flow visualisations for helium, light from the bell-shaped plasma beneath the tungsten electrode was eliminated by the band pass and neutral density filters.…”

“…This cylindrical feature does not extend fully to the anode and extends only slightly beyond the electrode, suggesting that a body force is acting heavily on the flow close to the anode. Based on numerical magneto-hydrodynamic models [24][25][26][27], the plasma jet is indeed expected to decelerate, as the axial Lorentz forces are expected to change magnitude and direction locally due to increased electromagnetic activity close to the anode. This observation is also supported by previous measurements which show that helium produces a lower arc stagnation pressure than argon [27].…”

Thermodynamic properties of He/Ar/N2/C/Ni/Co thermal plasmas used in carbon nanotube synthesis

“…However, to the best of our knowledge, there is no published work to date concerning theoretically determined basic data devoted to characterize any plasma mixture used in carbon materials synthesis through arc discharge method. Therefore, our two previous papers [37,38] can be considered as the first theoretical sources to consult in this context. These two papers, considered as the first part of a series, deal with the evaluation of radiative properties of Ar/N 2 /He/C/Co/ Ni thermal plasmas using two distinct but complementary methods that are the net emission coefficient (NEC) concept [37] and the mean absorption coefficient (MAC) approach [38].…”

“…Therefore, our two previous papers [37,38] can be considered as the first theoretical sources to consult in this context. These two papers, considered as the first part of a series, deal with the evaluation of radiative properties of Ar/N 2 /He/C/Co/ Ni thermal plasmas using two distinct but complementary methods that are the net emission coefficient (NEC) concept [37] and the mean absorption coefficient (MAC) approach [38]. The next part of the series, including this paper, is devoted to provide some thermo-physical properties for plasmas containing the same elements.…”

“…The calculation results of thermodynamic properties for the temper ature range 1000-30 000 K have been presented and discussed in section 4. The first part of the fourth section is devoted to the same condition as in [37,38], which was deduced from various configurations typically used in CNT synthesis by arc discharge. The rest of the fourth section will deal with other conditions of reactor volume, pressure and mixture proportion in order to assess the influence of these parameters on the thermodynamic properties.…”