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Plasma Surface Modification and Etching of Polyimides
Published in Malay K. Ghosh, K. L. Mittal, Polyimides Fundamentals and Applications, 2018
Frank D. Egitto, Luis J. Matienzo
Tetrafluoromethane (CF4) is a gas commonly added to oxygen for plasma etching of polymers. Increases in Ο atom concentration [49] and etching rates [49, 136, 165-169], with addition of small concentrations of CF4 or other fluorocarbon gases, are well documented. Plumb and Ryan [170] have discussed the set of reactions occurring in the gas for such mixtures and have proposed rate constants for each of the reactions. For O2/CF4 mixtures, atomic fluorine production is enhanced either by gas-phase chemical reactions with Ο atoms or by changes in the electron energy distribution function. However, only a change in the electron energy distribution function with addition of CF4 to O2 enhances production of atomic oxygen.
Cryogenic buffer gas beams of AlF, CaF, MgF, YbF, Al, Ca, Yb and NO – a comparison
Published in Molecular Physics, 2022
Sidney C. Wright, Maximilian Doppelbauer, Simon Hofsäss, H. Christian Schewe, Boris Sartakov, Gerard Meijer, Stefan Truppe
Sulphur hexafluoride and nitrogen trifluoride are not the only possible fluorine donors. We performed preliminary experiments using tetrafluoromethane () as fluorine donor gas that lead to similar molecule yields as for and , and we therefore did not further pursue this avenue. Solid xenon difluoride (), theoretically predicted to be a good candidate fluorine donor molecule [78], did not prove as a viable option. At room temperature, the compound evaporates quickly into a hazardous gas. Nevertheless, we connected a reservoir containing crystals to the buffer gas cell and adjusted the flow with a needle valve. We observed efficient molecule production, but the relatively high flow rate resulted in a very fast molecular beam.
CF4-n (SO3) n (n = 1–4): a new series of organic superhalogens
Published in Molecular Physics, 2022
Jitendra Kumar Tripathi, Ambrish Kumar Srivastava
It should, however, be noticed that the electronegative atom such as F does not necessarily increase the EA of the system. Gutsev et al. [32,33] investigated the ground-state geometries of carbonfluorides (CFn) clusters for n = 1–4 and calculated their EAs. They noticed that the increase in F atoms does not increase the EA of CFn clusters such that the EA of CF4 is obtained to be negative, −1.94 eV [32] at LSDA and −1.22 eV [33] at the HF/6-31 + G(d) level. This is evidently due to the fact that carbon tertrafluoride or tetrafluoromethane (CF4) is a highly stable compound, which does not react with acids or hydroxides. Therefore, we need to substitute F with some other ligand in order to increase the EA. In this paper, we consider the substitution of sulphur trioxide (SO3) in CF4 and study the resulting CF4-n(SO3)n (n = 1–4) molecules in neutral and anionic forms using density functional theory (DFT). We calculate their EAs and notice that they indeed behave as superhalogens.
Processing trends of silk fibers: Silk degumming, regeneration and physical functionalization
Published in The Journal of The Textile Institute, 2020
Shivani Rastogi, Balasubramanian Kandasubramanian
Plasma is considered as the fourth state of a material having both negatively and positively charged particles along with the neutral atoms and molecules. The equilibrium between positive and negative charged entities in plasma results in their conducting and neutral nature. The plasma treatment is an eco-friendly and efficient approach to modify surface properties of silk fibroins. There are several gases such as oxygen, helium, nitrogen, CO2, argon, tetrafluoromethane (CF4), sulfur tetrafluoride (SF4), and fluorine, which are used to produce plasma. The plasma treatment modifies the surface by forming unsaturated bonds, stable free radicals, and polar groups. The setup for plasma treatment is shown in Figure 11.