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The permeation of water vapour through a coated polymer gas barrier film is controlled by the defects in the coating. By modelling these defects as a combination of macro-defects (in which the activation energy of permeation is that of the underlying polymer substrate) and nano-defects (in which the activation energy of permeation is something greater than that of the polymer substrate), we are able to understand the mechanisms of permeation in high gas barrier layers. Permeation is controlled by the amounts of such defects, with the observed overall activation energy informing us of the relative permeation through macro- and nano-defects. Three examples of aluminium oxide (AlOx)-coated polymers are given to illustrate this: a comparison of poly (ethylene naphthalate) and polypropylene (OPP) substrates, the role of sputter power in AlOx/OPP films and the role of oxide thickness in AlOx/OPP films. When the amount of permeation through macro-defects is quite low, and hence nano-defect permeation is a significant proportion of the overall water vapour transport, control of each of the two defect types becomes important. Contrary to what has been previously assumed, the activation energy can be observed as greater in some cases in which the overall permeation is also greater, and this can be explained by an increase in the proportion of permeation taking place through nanodefects. This model is evidenced by reference to microstructural and other characterisation, and hence gives rise to understanding of the relationship between process properties, microstructure and permeation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Innovative design for producing skinless polymer foams by gas dissolution foaming. • The gas diffusion barrier maintains high gas concentration in the polymer edges. • Achievement of skinless polymer foams by using the gas diffusion barrier approach. • Thin films with homogenous structures were completely foamed without solid skins. • Porous in the outer layers expose the inner cellular structure to external medium. An innovative approach to reduce and eliminate the non-foamed solid skins of the cellular polymers fabricated by gas dissolution foaming is presented in this work. The incorporation of a flexible gas diffusion barrier on the polymer surfaces during the saturation and foaming processes provided significant reduction or even hindered the appearance of the non-foamed solid skins while enabling appropriate expansions in several polymers (PMMA, PS, PC, and PCL). Besides, this approach has allowed to achieve significant expansions by foaming polymer samples with thicknesses in the order of magnitude of the non-foamed solid skins, i.e., thin films (<100 µm). This paper discusses how the gas diffusion barrier allows reducing the solid skins, the mechanisms involved in the gas diffusion process, and the possibility of interconnecting the inner cellular structure with the external medium. [ABSTRACT FROM AUTHOR]

With a type of capacitatively coupled plasma enhanced chemical vapor deposition (PECVD) technique, where two specially designed electrodes face to each other, the inner surface of hollow 3-dimensional objects such as poly(ethylene terephthalate) (PET) bottles can be coated with diamond-like carbon (DLC) thin film. DLC-coated PET bottles obtained with this technique have an enhanced gas barrier property, and therefore are applicable to industrial use such as for the extension of the shelf-life of contents sensitive to gas permeation. In this paper, the impact of power frequency ranging from 2.5 to 13.56MHz was studied in order to research the behavior of plasma inside PET bottles and resultant properties. Different power frequency turned out to be influential on gas barrier property, the overall and distribution of tint, and adhesion between DLC and PET substrate. In addition, positron annihilation turned out to be powerful tool for the comparison of different coating conditions because it clarifies the homogeneity of DLC thin films through providing information on overall structure and thickness of them. These findings can be used for the optimization not only in the beverage PET bottle application, but also in other capacitatively coupled PECVD devices. [ABSTRACT FROM AUTHOR]

Abstract: A cylindrical plastic scintillator cell, used for radioxenon monitoring within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty, has been coated with 425nm Al2O3 using low temperature Atomic Layer Deposition, and its performance has been evaluated. The motivation is to reduce the memory effect caused by radioxenon diffusing into the plastic scintillator material during measurements, resulting in an elevated detection limit. Measurements with the coated detector show both energy resolution and efficiency comparable to uncoated detectors, and a memory effect reduction of a factor of 1000. Provided that the quality of the detector is maintained for a longer period of time, Al2O3 coatings are believed to be a viable solution to the memory effect problem in question. [Copyright &y& Elsevier]

Microbial oxidation in aerobic soils is the primary biotic sink for atmospheric methane (CH), a powerful greenhouse gas. Although tropical forest soils are estimated to globally account for about 28% of annual soil CH consumption (6.2 Tg CH year), limited data are available on CH exchange from tropical montane forests. We present the results of an extensive study on CH exchange from tropical montane forest soils along an elevation gradient (1,000, 2,000, 3,000 m) at different topographic positions (lower slope, mid-slope, ridge position) in southern Ecuador. All soils were net atmospheric CH sinks, with decreasing annual uptake rates from 5.9 kg CH-C ha year at 1,000 m to 0.6 kg CH-C ha year at 3,000 m. Topography had no effect on soil atmospheric CH uptake. We detected some unexpected factors controlling net methane fluxes: positive correlations between CH uptake rates, mineral nitrogen content of the mineral soil and with CO emissions indicated that the largest CH uptake corresponded with favorable conditions for microbial activity. Furthermore, we found indications that CH uptake was N limited instead of inhibited by NH. Finally, we showed that in contrast to temperate regions, substantial high affinity methane oxidation occurred in the thick organic layers which can influence the CH budget of these tropical montane forest soils. Inclusion of elevation as a co-variable will improve regional estimates of methane exchange in these tropical montane forests. [ABSTRACT FROM AUTHOR]

Abstract: In this work Al2O3 and SiO2 coatings are tested as Xe diffusion barriers on plastic scintillator substrates. The motivation is improved beta–gamma coincidence detection systems, used to measure atmospheric radioxenon within the verification regime of the Comprehensive Nuclear-Test-Ban Treaty. One major drawback with the current setup of these systems is that the radioxenon tends to diffuse into the plastic scintillator material responsible for the beta detection, resulting in an unwanted memory effect. Here, coatings with thicknesses between 20 and 900nm have been deposited onto plastic scintillators, and investigated using two different experimental techniques. The results show that all tested coatings reduce the Xe diffusion into the plastic. The reduction is observed to increase with coating thickness for both coating materials. The 425nm Al2O3 coating is the most successful one, presenting a diffusion reduction of a factor 100, compared to uncoated plastic. In terms of memory effect reduction this coating is thus a viable solution to the problem in question. [Copyright &y& Elsevier]

Abstract: The addition of a coating on the inside walls of a standard polyethylene teraphthalate (PET) bottle provides a gas barrier improvement of the packaging for beer, juice and carbonated soft drinks. Sidel Inc. has developed a plasma-assisted deposition process of hydrogenated amorphous carbon (a-C:H) films, which uses pulsed microwave discharges with acetylene gas precursor. We report here the space- and time-resolved optical diagnostics of this process, aiming to assess the microwave discharge characteristics and behavior during the deposition process. Time-resolved fast imaging of the discharge enables the investigation of plasma ignition, expansion and extinction inside the bottle along the microwave power pulses of 100 Hz frequency. Space- and time-resolved optical emission spectroscopy is used in order to examine the feature of the main radiative species within the plasma and to estimate the gas temperature. Measurements showed that the plasma emission intensity is always higher in the base and around the neck of the bottle, which comes from the discharge spatial inhomogeneity and from the successive phases of plasma development always involving the lower part of the bottle. The spatio-temporal intensity distribution of radiative species, namely H-atom and C2 molecule, is in good agreement with fast imaging, whereas the profile of CH radical is found to be more homogeneous. Rotational temperatures of excited states of C2 molecule and CH radical measured during a microwave pulse were found to be relatively high, between 1700 and 2700 K, and slightly dependent of time and position. A short heating time of only a few hundreds of microseconds is noticed and gives evidence of non equilibrium between the rotational temperatures and the gas temperature. This preliminary plasma diagnostic is a first step towards drawing possible connections between plasma characteristics and a-C:H coating properties and PET bottle post-treatment temperature, aiming at optimizing the deposition process. [Copyright &y& Elsevier]

Abstract: Hybrid ZnO/Al2O3 layers grown by atomic layer deposition (ALD) at extremely low temperature (60 °C) have been investigated as thin film encapsulations (crystalline ZnO and amorphous Al2O3 films) on polymer substrates. All single and laminated film thicknesses are approximately 60 nm. As the thickness of ZnO layer decreased from 60 nm to 0 nm, the physical properties of laminated structures were systematically manipulated such as film crystallinity, surface roughness, density, transmittance and stress. The multi-laminated structure with 10 nm thick ZnO and 10 nm thick Al2O3 layers exhibited very lower crystallinity, smoother surface (root mean square ∼ 0.2 nm), higher transmittance (over 90% at 550 nm wavelength) and similar film stress, to compare with these of a single ZnO film. As a transparent gas barrier layer, the multi-laminated structure with a thinner ZnO and Al2O3 had better barrier property than that of single ZnO and Al2O3 layers, showing that the water vapor transmission ratio of multi-laminated ZnO/Al2O3 layer was 10 times lower than that of the single layer. [Copyright &y& Elsevier]