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In metallurgic applications of thermal plasmas the presence of metal vapour, even in small proportion tends to increase the electron number density and to modify some basic properties such as the electrical conductivity and the radiation emission. In this paper we focus on the influence of these vapours on the radiation properties. After the definition of some necessary and basic functions and laws we briefly present the mechanisms responsible for emission and absorption of radiation in thermal plasmas. Then an important section is devoted to the role of metal vapours on the net emission coefficient which is the most popular parameter used to evaluate the radiation power losses in general models. It is shown that metal vapours increase the emission especially at low and intermediate temperatures (T < 12,000 K) and that their relative influence depends on the nature of the initial gas and of the metal itself. We list a rather important number of references presenting calculation of net emission in various gas–metal mixtures. Finally we show in a last section the influence of metal radiation on general plasma properties such as the energy transfer (other methods than the net emission coefficient), the cooling effect, the global energy balance and the heating of particulates injected in the plasma. The most spectacular effects are the increase of radiation losses in the energy balance and the complex role of the metal in the local cooling of the plasma. 相似文献
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Wang Fei Cressault Yann Teulet Philippe Li Huan Yang Ke 《Plasma Chemistry and Plasma Processing》2019,39(4):1049-1069
Plasma Chemistry and Plasma Processing - Gas tungsten arc welding (GTAW), a widely used industrial process, is one of the most intense artificial sources of optical radiation. This paper presents a... 相似文献
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R. Hannachi S. Boussaïdi P. Teulet G. Taieb Y. Cressault A. Gleizes Zohra Ben Lakhdar 《Applied Physics A: Materials Science & Processing》2008,92(4):933-937
A spectroscopic study of the plasma plume created by a laser beam on the surface of NaCl aqueous solution is presented. Optical
emission spectra are recorded and temporally analyzed; electron number density is determined from the Stark broadening of
the NI nitrogen line, and temperature is obtained from relative intensity of OI oxygen lines. The intensity of an atomic line
from sodium was used to quantitate its molar percentage in the Oceanic and Mediterranean sea, and calibration curves have
been constructed for concentrations ranging up to 1.5%. 相似文献
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R. Riahi P. Teulet Y. Cressault A. Gleizes Z. Ben Lakhdar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(2):185-192
A method is presented to calculate the radiative transition probabilities and the radiative recombination rate coefficients
between electronic molecular states. Total transition probabilities are determined from vibrational transition probabilities
without considering the detailed rotational structure of the molecular electronic states. Radiative recombination rate coefficients
are obtained from the computation of vibrational photo-ionisation cross sections. Concerning spontaneous emission, Lyman (B
→ X) and Werner (C → X) band systems of H2 and Meinel (A → X), (B → A) and (B → X) band systems of OH are investigated. For radiative recombination, transitions between
H2+ (X) and H2(X), and between OH+(X, a, A, b, and c) and OH(X) are considered. Transition probabilities and recombination rate coefficients are calculated
as a function of temperature in the range 1500–15 000 K. 相似文献
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R. Hannachi Y. Cressault Ph. Teulet A. Gleizes Z. Ben Lakhdar 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
The resonance escape factors for the lines emitted by a neutral calcium atom Ca I at 4226.73 Å and of ionic calcium Ca II at 3933.66 Å and at 3968.47 Å are calculated assuming a Voigt profile and in the case of CaCl2–water plasma. The dependence of the escape factor on the optical thickness ?0 from the line center which itself depends on the two main spectral line shape broadening mechanisms (pressure and Doppler effects) are considered. The variation of the resonance escape factors with the temperature, the CaCl2 molar proportion and the size of the plasma are also investigated. This calculation is useful for the application of Laser-Induced Breakdown Spectroscopy in the quantitative analysis of elemental composition. Its application allows us to reduce the non-linearities in the relation between resonance lines intensities of calcium in our case and its concentration. 相似文献
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