Atmospheric plasma study

By simultaneous monitoring of tidal volume and respiratory rate, or minute volume, and the concentration of an inhaled vapor in the bloodstream and the vapor in the exposure atmosphere, pharmacokinetic studies on the C t relationship have shown that the effective dose was nearly proportional to the exposure concentration for vapors such as 1,1,1-trichloroethane (Dallas et al., 1986), which has a saturable metabolism, found that the steady-state plasma concentrations were disproportion-ally greater at higher exposure concentrations. 

The modification of the chemical composition of polymer surfaces, and thus their wettability with chemical substances, can be realized in different ways electric discharges more commonly called Corona effect, oxidation by a flame, plasma treatment, UV irradiation and also UV irradiation under ozone atmosphere. Numerous studies have been devoted to the effects of these different treatments. More recently, Strobel et al. [204] compared the effects of these treatments on polypropylene and polyethylene terephthalate using analytical methods such as E.S.C.A., F.T.I.R., and contact angle measurements. They demonstrated that a flame oxidizes polymers only superficially (2-3 nm) whereas treatment realized by plasma effect or Corona effect permits one to work deeply in the polymer (10 nm). The combination of UV irradiation with ozone flux modifies the chemical composition of the polymers to a depth much greater than 10 nm, introducing oxygenated functions into the core of the polymer. 

Loss of ions occurs via the processes of mutual neutralization, ternary ionic recombination and attachment to aerosol surfaces, processes which urgently need further study in the laboratory. It is an interesting fact that the ion chemistry directly accelerates the loss of ionization from all regions of the atmospheric plasma. Atomic ions are converted into molecular ions, molecular ions into larger cluster ions which recombine more rapidly. The larger ions also act as nucleation sites for the formation of aerosols, thus involving a transition from the molecular to the liquid state. 

A notable exception is a study by Hesse et al. (2008) who investigated the effect of powder grain size and grain size distribution on the spatial distribution of calcium phosphate phases in atmospheric plasma-sprayed hydroxyapatite coatings incubated in r-SBF (SBF-H, Table 7.8). Coatings were mechanically abraded under dry conditions in steps of 40 pm by abrasive SiC paper, and the newly created surfaces analysed by XRD with Rietveld refinement for their quantitative phase composition. The results of this depth profiling are shown in Figure 6.8. 

The surface modification of the ground rubber tire (GRT) powder was found to be suitable for enhancement of its adhesion to nitrile rubber (NBR) vulcanizates (Zhang et al., 2009c). By use of the atmospheric pressure dielectric barrier discharge, the hydrophobic surface of the powder transformed to a hydrophilic one as shown by the water contact angle, ATR-FTIR, and X-ray photoelectron spectroscopic (XPS) studies. After atmospheric plasma treatment, the improvement in the tensile strength and tear strength was observed for the modified tire powder-filled NBR vulcanizates. The latter was attributed to the enhanced interfacial interaction between modified GRT and NBR matrix. 

Tran, H.V. (2004) Investigation into the thermal dehydroxylation and decomposition of hydroj apatite during atmospheric plasma spraying NM R and Raman spectroscopic study of as-sprayed coatings and coatings incubated in simulated body fluid. Unpublished Ph.D. 

If information about a solid surface free energy (SFE) is needed, contact angle measurements and ink tests are two of the most frequently used methods. Here we present a comparative study of contact angle measurements and ink tests on 13 different materials. We observed major differences in the SFE values obtained by these two techniques and explained the differences on the basis of basic theoretical concepts of both methods. We found that test inks fail to monitor the efficiency of atmospheric plasma treatments on low surface energy solids. Moreover, we determined the polar and dispersion contributions to the test inks total surface tension (ST) in order to provide a more detailed understanding of these methods to determine a solid SFE. 

In a recent study [182], an atmospheric plasma (AP) composed of a mixture of hydrogen (1 vol%) and helium was used to activate silicon substrates directly, creating surface-bound radicals that can then initiate the liquid-phase graft polymerization from these anchoring sites (see Fig. 1.14). 

Kim et al. have reported the investigations of surface modification phenomena of different metal surfaces by atmospheric plasma jet treated under the condition of nearly atmospheric pressure. The aims of our study are to obtain the optimum conditions with high surface energy and to understand the surface phenomena for increasing the adhesion property. 

A recent comparison by Sparavigna [4] of ozone with corona and ozone with atmospheric plasma treatment has revealed an interesting opportunity to further optimize the extrusion coating process for flexible packaging structures. In particular, the study involved two experimental runs, which were performed by coating low-density polyethylene onto oriented polypropylene and polyester film. Ordinary heat seal strength techniques were used to quantify the effects of the variables on heat seal strength vs. seal temperature. 

It was evident from post-treatment surface tensions in this study that iiquid adhesives using thermosetting epoxide polymers mixed with catalyzing agents wet significantly in atmospheric plasma-based pretreatments because the differential surface free energies are at a minimum of 20 dynes/cm, twice the benchmark industry requirement. 

The purpose of this study is to examine one promising combinational approach, specifically capitalizing on the particle cleaning advantage of CO2 with the efficient atomic and molecular level cleaning capabilities of atmospheric plasma ionic discharges. The use of combinational treatments is critical for several reasons ... 

In plasma chromatography, molecular ions of the heavy organic material to be analy2ed are produced in an ionizer and pass by means of a shutter electrode into a drift region. The velocity of drift through an inert gas at approximately 101 kPa (1 atm) under the influence of an appHed electric field depends on the molecular weight of the sample. The various sonic species are separated and collected every few milliseconds on an electrode. The technique has been employed for studying upper atmosphere ion molecule reactions and for chemical analysis (100). 

Principles and Characteristics Ion mobility spectrometry (IMS) is an instrumental technique for the detection and characterisation of organic compounds as vapours at atmospheric pressure. Modern analytical IMS was created at the end of the 1960s from studies on ion-molecule chemistry with mass spectrometers and from ionisation detectors for vapour monitoring. An ion mobility spectrometer (or plasma chromatograph in the original termininology) was first produced in 1970 [272],... 

Free radicals are short-lived, highly-reactive transient species that have one or more unpaired electrons. Free radicals are common in a wide range of reactive chemical environments, such as combustion, plasmas, atmosphere, and interstellar environment, and they play important roles in these chemistries. For example, complex atmospheric and combustion chemistries are composed of, and governed by, many elementary processes involving free radicals. Studies of these elementary processes are pivotal to assessing reaction mechanisms in atmospheric and combustion chemistry, and to probing potential energy surfaces (PESs) and chemical reactivity. 

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