Energetics of Reactions in a Dielectric Barrier Discharge with Argon Carrier Gas: III Esters

Abstract

A large research reactor for dielectric barrier discharge (DBD) experiments at atmospheric pressure (AP) has been used with argon (Ar) carrier gas under constant plasma conditions (f = 20 kHz, Va(f) = 8 kVp‐p = 2.8 kVrms). Five esters, acrylates with differing number of unsaturations were used as “monomers”; monomer flows, Fd, were at ‰ concentrations in the F = 10 standard liters per minute (slm) of argon. We earlier perfected and reported a method for measuring Eg, the energy dissipated per cycle of the applied a.c. voltage, and ΔEg, the energy difference with and without monomer in the Ar flow. The latter, combined with Fd enable calculation of Em, the average energy absorbed from the plasma per monomer molecule. Plots of Em versus Fd and 1/Fd yield much valuable information, for example about the role of CC and CC bonds in fragmentation and polymerization reactions. Fourier‐transform infrared (FTIR) spectroscopy, spectroscopic ellipsometry (SE), and scanning electron microscopy (FEG‐SEM) further enhance and complement data interpretation.

Energetics of reactions in a dielectric barrier discharge with argon carrier gas: IV ethyl lactate

“…Figure (a) and (b) respectively show plots of (a) E m versus F d , the flow of monomer vapor (in standard cm 3 per minute, sccm), and (b) versus 1/ F d . One clearly notices three distinct regimes: the ones corresponding to the lowest and high F d values are respectively referred to as monomer‐lean and monomer‐rich , separated by a transition range of F d comprising two peaks and a dip; this latter transition feature has already been reported (and interpreted) in our earlier article dealing with a series of esters . The first peak, E m = 83 eV/molecule, corresponds to the particular condition where maximum transfer of energy from the plasma resulted in total fragmentation, presumably breakage of all covalent bonds in the molecule.…”

Energetics of reactions in a dielectric barrier discharge with argon carrier gas: VI PEG‐like coatings

“…In agreement with previous work, the heavier molecule exhibits a significantly higher value of ; a “monomer‐rich” region spreading over high values, where smoothly decreases with rising . Figure b also shows plots of , this time versus 1/, and it reveals quasi ‐linear behavior in the monomer‐rich region, something that we had already amply discussed in our earlier reports . The initial slopes for 1G and 2G were 8.8 W and 11.1 W, respectively.…”

“…The initial slopes for 1G and 2G were 8.8 W and 11.1 W, respectively. These are closely related to the propensity of a precursor molecule to absorb energy available from the plasma; a higher value in the case of 2G, heavier than 1G but from the same chemical family (here, ethers), is also in agreement with previous observations; a “dip region” separating (i) and (ii) is a transition feature that was already reported (and interpreted) in our earlier article dealing with a series of esters . It is suggested that this region, neighboring and in which drops drastically, results from a marked fragmentation of oxygen‐bearing hydrocarbon groups, dominated by liberation of CO 2 .…”

“…Some of the present authors have recently shown that dielectric barrier discharge (DBD) plasmas with Ar as carrier gas can be used to deposit PP coatings from a wide variety of monomers, with precise knowledge of the energy per precursor molecule, , absorbed from the plasma's “energy reservoir.” In recent joint communications with D. Hegemann, this approach was even shown to permit comparisons between AP and LP PP processes, based on a new “energy conversion efficiency” (ECE) parameter reminiscent of the “Yasuda parameter— W/FM ” concept from the 1970s and 80s …”

Hybrid and Fluid Modeling of Ion Activation Energy and Reactive Fluxes to Particulates Suspended in Air and Residing on Surfaces

“…Among the atmospheric pressure plasma sources, dielectric barrier discharges (DBDs), and plasma jets are the preferred sources that enable scale‐up for industrial and medical processing . For example, Nisol et al built and tested a large reactor for performing dielectric barrier discharges experiments at atmospheric pressure. Akishev et al used a DC plasma jet with various gas mixtures for sterilization of cultivation media surfaces.…”