Molecule synthesis in an Ar–CH₄–O₂–N₂microwave plasma

Abstract

The formation of new molecules in a microwave plasma, created from a mixture of Ar, CH 4 , N 2 and O 2 , is investigated by means of an in-depth study of the molecular abundance in the plasma. The molecules are detected by means of tunable diode laser absorption spectroscopy and by absolute mass spectrometry. Three groups of molecules can be discerned in terms of molecular abundance: CO is predominantly formed, together with H 2 O, N 2 and H 2 . The molecules CH 4 and O 2 are significantly depleted, but still abundant in a finite quantity. The third group is formed by several other species like NH 3 , NO, HCN etc. This tendency is expected to occur in every low temperature plasma containing C, O, H and N atoms. Furthermore, the combination of both techniques also allows us to make a clear distinction between the etching mode and deposition mode of the microwave reactor. Etching mainly occurs when the ratio of admixed gas flows (O 2 )/ (CH 4 ) > 0.5.

Recent Progress of Plasma-Assisted Nitrogen Fixation Research: A Review

“…The optical emission spectra also indicated an increase in N + , which is possibly a result of the reaction between Ar + and N 2 . The authors stated that noble gases can be seen as an additional source of N atoms that contribute to the increase in NH 3 production [123]. De Castro et al investigated the effect of helium addition in their research with DC glow discharge plasma [124,125].…”

Surface characterization of hydrophilic coating obtained by low‐pressure CH4O2 plasma treatment on a polypropylene film

“…We can also observe that nitrogen surface content remains almost constant with values around 3.8% for both untreated and plasma‐treated samples susbtrates. These results show that the deposited plasma‐polymerized organic nanolayer is functionalized with oxygen‐based species because of the presence of oxygen in the mixture gas for the plasma generation 22, 24. Nevertheless, the real oxidation level of the outermost layers must be expressed not only in terms of the oxygen atomic percentage (%) but also through the use of the O/C ratio, which is much representative of the oxidation state of the plasma‐polymerized layer.…”

Durability of the wettability properties of a polypropylene film with a low‐pressure CH4–O2 plasma treatment

“…The increase is higher at low exposure times; as the exposure time increases, the weight gain is lower. In this case, the weight loss associated with the etching mechanism of plasma is counterbalanced by the deposition of a plasma product typical of the plasma polymerization process due to the nature of the plasma gas with the mixture of an organic gas (CH 4 ) and a highly reactive gas (O 2 ) 20–22…”