Barrier Properties Of Materials Research Articles

Smoothing Methods for Continuous Permeation Data Measured Discretely Designated for Quick Evaluation of Barrier Materials

Information concerning barrier properties of materials used for production of personal protective equipment fundamentally not only affects their useful properties, but also supports the end users’ decisions. Data obtained from measurements by standardized methods have to be processed by appropriate statistical methods. The article deals with numerical and statistical methods of reconstruction of a continuous curve out of discretely measured data. These mathematical models are proposed as an extension to the manual measurement of a conductometric method. Behaviour of these models is demonstrated on two chemical warfare agent simulants, however, the proposed methodology is universal and can be applied also to chemicals which have no conductivity. The parametric and nonparametric models are studied in the curve reconstruction, as well as in the calculation of subsequent characteristics, for example, a lag-time. The nonparametric model shows the best results which are in accordance with an expert’s estimate.

Modification of nonwoven polymer materials for increasing of their filtration and antibacterial properties

AbstractPolytetrafluoroethylene (PTFE), octenidine dihydrochloride (OCT), and zinc oxide (ZnO) were used to modify the polypropylene nonwoven material by the methods of “wet chemistry” and low‐energy electron beam deposition (EBD). The influence of nonwoven material modification on the morphology, chemical composition, filtration, and antibacterial properties was established. The modified material has antibacterial activity against the gram‐positive strain Staphylococcus aureus and against gram‐negative strains of Escherichia coli and Klebsiella pneumoniae (suppression of bacterial growth for materials with OCT was 100%, with ZnO—70%). PTFE application to Aquaspun leads to a significant increase in the contact angle (from 141.3° to 152.7°) and air filtration efficiency (from 78.3% to 83.4%), which provides the barrier properties of the material. It was established that the material obtained using low‐energy EBD demonstrated a more pronounced antimicrobial potential against the tested strains of St. aureus.Highlights The influence of polypropylene nonwoven materials surface modification methods is systematically investigated. Low‐energy electron beam deposition increases antibacterial and filtration properties of nonwoven materials. Surface modification methods increase barrier properties of polypropylene nonwoven materials.

Reactive transport modeling for assessing coupled hydrogeochemical processes at interfaces in deep geological repositories: from the laboratory to the real world

Abstract. Deep geological repositories with a multi-barrier concept are foreseen by various countries for the disposal of high-level radioactive waste. Simulation tools for a close-to-reality description of repository evolution scenarios are required, especially to resolve the challenging task of comparing and assessing the long-term safety of different repository concepts in different host rocks within the German site-selection process. Chemical, thermal, and pressure gradients at the interfaces of the different barriers in a repository can lead to mineral dissolution and precipitation, generating non-linear responses in transport and mechanical properties of barrier materials and host rocks. Reactive transport modeling (RTM) can be applied to investigate these perturbations and processes across temporal and spatial scales to assess subsurface evolution. Nevertheless, implementing RTM at the continuum scale while accounting for pore-scale heterogeneities and geometry evolution remains a challenge. Pore-scale simulations offer the potential to capture the complex evolution of porous media over a broad range of Peclet and Damköhler numbers, and they can be utilized to improve the RTM by using upscaling methods (Prasianakis et al., 2020). In this context, we developed “lab-on-a-chip” experiments, combining time-lapse high-resolution optical microscopy and confocal Raman spectroscopy to test extended constitutive equations to classically employed Archie's law to improve the description of changes in transport properties (e.g., diffusivity) in evolving porous media in RTM. The 3D Raman tomography of the porous media combined with pore-scale modeling enabled the derivation of upscaled transport parameters. Our results highlight the importance of calibrating pore-scale models with quantitative experiments prior to simulations over a wide range of Peclet and Damköhler numbers, whose results can be further used for the derivation of upscaled modeling parameters. The derived and parameterized constitutive equations based on simple systems have been tested in reactive transport models as a sensitivity case study to evaluate uncertainties in the predictions of the evolution of real subsurface systems such as clay–cement interfaces in deep geological repositories.

Combining innovative experimental approaches and cross-scale reactive transport modelling for assessing coupled hydrogeochemical processes at interfaces in deep geological repositories for radioactive waste

Abstract. Deep geological repositories with a multi-barrier concept are foreseen by various countries for the disposal of high-level radioactive waste. A reliable and consistent assessment of the safety of these repositories over time scales of some hundred thousand years requires an advancement of process understanding. Simulation tools need to be developed for a close-to-reality description of repository evolution scenarios. This is especially required to resolve the challenging task of comparing and assessing the safety of different repository concepts in different host rocks within the German site-selection process. The construction of underground galleries and geotechnical barriers in the host rock formation and the emplacement of nuclear waste packages will create perturbations induced by chemical, thermal and pressure gradients at the interfaces of the different barriers, leading to mineral dissolution and precipitation to achieve re-equilibration. Such coupled hydrogeochemical processes generate non-linear responses in transport and mechanical properties of barrier materials and host rocks, which have to be taken into account for a more rigorous assessment of repository system evolution. Reactive transport modeling (RTM) can be applied to investigate these perturbations and processes across temporal and spatial scales, from the micro-scale at interfaces via the repository near field to the entire repository system – information not accessible through experiments alone. Although RTM is capable of addressing highly complex hydrogeochemical phenomena, the application of RTM codes to real systems is impeded by the often simplified description of coupled processes. To enhance the predictive capabilities of reactive transport models and to gain fundamental insights into the coupling between solute and radionuclide transport properties (e.g., permeability and diffusivity) of porous media and dissolution/precipitation processes, we conducted experiments on “simplified” chemical systems combined with pore-scale and continuum-scale reactive transport modelling to study processes in isolation, with the final aim of improving conceptual approaches for process couplings implemented in reactive transport codes. In this context, we investigated the effects of coupled mineral dissolution and precipitation in porous media on changes in permeability using flow-through experiments conducted in a magnetic resonance imaging scanner, which enabled the in situ investigation of porosity evolution in combination with monitoring changes in permeability and mineralogy. Our observations showed that classical implementations in reactive transport codes such as the Kozeny–Carman equation (Carman, 1937) failed to reproduce the changes in permeability and that more sophisticated approaches are required (Poonoosamy et al., 2020a, b). Moreover, we developed a novel “lab-on-a-chip” setup, i.e., micronized counter diffusion reactors with in operando 3D Raman tomography (Poonoosamy et al., 2019, 2020c), which enables evaluation of the alteration in pore architecture and study of the effect of coupled mineral dissolution and precipitation on the diffusive transport of solutes and radionuclides in porous media. Our approach enables the development of process-based theoretical models which allow for improvements in RTM codes and for predicting the evolution of perturbed interfaces in waste repositories, thus building confidence in the predictive capabilities of reactive transport models and reducing uncertainties with respect to future repository evolution.

Properties of MgAl2O4 doped alumina barrier layers for dielectric barrier discharge

In the current work, we studied the effect of multiphasic dielectric material on coplanar dielectric barrier discharge. To enhance the application potential of standard alumina () ceramic barriers, composite materials composed of immiscible and Mg-spinel () phases were prepared and investigated. The effect on coplanar dielectric barrier discharge was studied in a broad concentration profile of the composite materials ranging from 0 to 100 vol.% in an alumina matrix. The study was mainly focused on the determination of ignition voltage as a crucial parameter for industrial applications. The minimum ignition voltage was found in the ceramic composite with 15 vol.% . We also noticed differences in plasma filament localization on the ceramic surfaces of different composites. This work also brings comprehensive investigation of the electrical and microstructural properties of this biphasic barrier material. Detailed investigation revealed that the ignition voltage was a nontrivial combination of both bulk (phase and chemical compositions) as well as surface (phase distribution, grain size, surface roughness) properties of the barrier materials.

Partial Discharge Imaging Correlated with Phase-Resolved Patterns in Non-Uniform Electric Fields with Various Dielectric Barrier Materials

This paper describes a correlation of partial discharge phase-resolved patterns with an optical imaging performed in a non-uniform electric field configuration. The influence of different dielectric barrier materials, placed on the plane electrode, on the discharge propagation and surface landing was investigated. The investigations were focused on the corona at positive polarity of AC high voltage. It was found that the initial positive corona stage is similar for all cases whereas the discharge propagation and surface landing strongly depends on the barrier material properties. The observed streamer discharge modes have been described by the geometrical measures such as stem length, stretch of a discharge profile on the dielectric barrier surface and an hemispherical envelope of discharge filaments. Since various dielectrics reveal different properties of charge accumulation and surface neutralization, the charge memory effect may be visible and can be related to the ability to create and sustain of additional electric field component. It may refer to subsequent discharges as well as to conditions faced at the voltage polarity reversal. The correspondence between different forms of phase-resolved patterns have been associated with the modes of streamer discharges observed by optical imaging. Presented methodology poses huge potential for both scientific investigations on underlying discharge phenomena as well as on the application in future diagnostic systems of HV insulation.

ESS 절연성능 향상을 위한 절연배리어 AC 절연파괴특성 분석

The importance of ESS (Energy Storage System) protection system is increasing due to the recent ESS fire events. It is necessary to achieve the insulation performance for AC voltage components caused by faults during operation. In this study, AC electrical reakdown(BD) voltage was analyzed varying with the insulation barrier design factors to improve the insulation safety of ESS. First of all, the correlation between the air breakdown path and AC breakdown voltage was experimentally investigated owing to the insulation barrier shape. Moreover, the effects of dielectric constant and the thickness on insulation performance were examined. Finally, the equivalence between the air breakdown propagation distance and the air gap distance was compared, and the design criteria for the insulation barrier was presented. Through the results, it was found that AC breakdown voltage increased with the air breakdown propagation distance. Moreover, AC breakdown was not influenced by the thickness but by the barrier material properties. It was verified that AC breakdown voltage could be estimated, based on the average breakdown propagation field and the air breakdown propagaion distance.

Visualization of Delamination in Encapsulated Flexible Electronics Fabricated using Slot Die Coating

A major challenge in the flexible electronics industry is the inability to quickly and accurately assess the mechanical properties of barrier materials used to encapsulate various devices. The feasibility of using a low-cost approach, digital photoelasticity (DP), to determine stress formation in barrier film is analyzed so that inherent weak areas cannot only be identified, but also reinforced. In this experimental study, ethylene vinyl acetate (EVA) is slot die coated onto untreated polyethylene terephthalate (PET) or onto PET treated with indium tin oxide (ITO) or poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). An axial stress is imposed on each sample using a universal test machine, and DP was used to obtain the stress and grab profiles. It has been shown that highly concentrated and multilayer EVA coatings withstand higher stress. Also, it has been shown that the locations of delamination happen at the side edge of the encapsulation when EVA was coated on a homogenous surface, but for heterogeneous surfaces, the delamination occurred at the boundary between the PEDOT:PSS and ITO. All these data were depicted using DP in very quick fashion. Therefore, DP is a viable method for quickly and accurately determining stress in barrier films.

Barrier properties of anti-gas military garments, considering exposure to gas organic compounds

The problems of determining the protective properties of barrier materials used for the production of body surface protection products of an isolative type are very actual. These garments are expected to have long-term resistance against permeation of toxic substances. The paper deals with the study of the effect of organic solvent vapours on the changes in protective properties of selected anti-gas protective garments commonly used by the North Atlantic Treaty Organization armed forces. Permeation measurements of selected gases with integral permeameter were performed to verify their barrier properties, surface changes after exposure to selected solvents by using a 3D optical profilometer, permeation measurements for vapours of these solvents with differential permeameter, and experimental simulating the possible influence of barrier properties of garments within permeation of air. It has been shown that in the case of gases, the permeability of the studied materials increases with decreasing kinetic diameter of the penetrant molecule used. In the case of acetonitrile and isooctane vapours, permeability increased with increasing vapour concentration due to interactions between polymeric materials and molecules of organic compounds. The permeation measurements of pure vapours and air/vapour mixtures indicate that the level of interactions between the molecules of the penetrant and the material of the protective garment is not strong enough to degrade the material of the garment in such a way as to allow a greater penetration of the pollutants through it. The results of permeation experiments for gases and organic vapours showed very good barrier properties of studied chemical isolated garments.

Assessing fire-blocking effectiveness of barrier fabrics in the cone calorimeter

Cone calorimetry experiments of on flexible polyurethane foam and flexible polyurethane foam covered with a variety of fire-blocking barrier fabrics were used to characterize and rank the effectiveness of barrier fabrics with the ultimate goal being an ability to predict the effectiveness of barrier fabrics for reducing the flammability of residential upholstered furniture. The primary measure used to characterize the burning behavior was heat release rate. The effect of the underlying sample substrate was shown to have a large effect on the burning behavior of flexible polyurethane foam samples, and a thermally insulating substrate was used during composite experiments. At times, rapid heat release rate fluctuations were observed, and in such cases approximate corrections were applied to correct for finite cone calorimeter time response. Measurements using thermocouples placed within the flexible polyurethane foam provided insights on flexible polyurethane foam pyrolysis behavior, the collapse rate of flexible polyurethane foam, and the thermal protective properties of barrier materials. Heat release rate temporal profiles for flexible polyurethane foam showed two distinct burning stages with peak values which have been attributed to sequential burning of species (primarily) derived from the diamine ( PHRR1) and polyol components ( PHRR2) used to manufacture the flexible polyurethane foam. When a barrier fabric was added, many of the composites displayed a three-stage burning behavior which was attributed to an initial short, intense burning (termed flash burning) stage associated with the barrier fabric covering followed by the two flexible polyurethane foam stages. Seven out of 16 flexible polyurethane foam/barrier fabric composites exhibited flame extinction prior to fuel burn out. Five out of the seven composites reignited when the spark ignition source was reapplied. Reignition allowed barrier fabric effectiveness to be assessed even for cases with flame extinction. Barrier fabric performance was shown to be consistent with four properties that were previously identified as important barrier fabric properties: barrier fabric flammability, gas permeability, thermal protection, and physical integrity. In addition, the current experiments indicate the presence and effectiveness of gas-phase active flame retardants in the barrier fabric can also play an important role. A limited number of tests were conducted to de-couple the effects of flame-retardant chemicals and physical effects of barrier fabrics on flexible polyurethane foam burning behavior. These tests showed that while flame-retardant chemicals can be effective in quenching and extinguishing the flames, the presence of effective barrier fabric shells is also very important in lowering the heat release rate of burning flexible polyurethane foam. In general, the presence of a barrier fabric was shown to reduce the heat release rate peak values during both flexible polyurethane foam burning stages. The magnitude of the peak associated with second-stage flexible polyurethane foam burning was deemed the most appropriate for characterizing the thermal protection provided by a barrier fabric. Since the times for PHRR2also varied between composites, a measurement referred to as the peak fire growth rate (PFIGRA) parameter was calculated by dividing the heat release rate by time since time to ignition and PFIGRA2was also considered for characterizing the barrier fabrics. Three possible classification schemes, each consisting of three classes, were introduced based on composite flame extinction and reignition behavior, PHRR2values, and PFIGRA2values. Each scheme provided differentiation between barrier fabric effectiveness. While the schemes were able to assess whether the barrier fabrics were particularly effective or ineffective, there were variations among classes of barrier fabrics having intermediate levels of effectiveness. Further work will be required to assess which, if any, of the classification schemes are most appropriate for predicting barrier fabric performance in residential upholstered furniture.

Thermal properties of engineered barriers for a Canadian deep geological repository

Global energy needs continue to rise along with society’s desire for carbon-reduced energy sources to limit climate change effects. One viable carbon-reduced energy source is nuclear power, which provides more than half the electricity requirements of the province of Ontario. Within Canada there are more than 2.5 million bundles of spent nuclear fuel, which will be stored in a deep geological repository. Efficiency of the repository system depends on dissipation of thermal energy. A comprehensive experimental study is presented on thermal properties of barrier materials. The influence of bentonite type, variability, moisture, and temperature on thermal properties is examined. Results show strong influence of moisture on thermal properties, some influence of temperature on low-density bentonite, minor influence of bentonite type, as well as low variability in the experimental measurements. The extensive database of physical measurements is compared with values from the literature and then used to statistically evaluate thermal property models selected from the literature. Using the base parameters from the literature, thermal property models performed adequately; however, soil-specific calibration of the model inputs improved the fit significantly. These results are now available to perform the numerical models for the proposed Canadian deep geological repository for used nuclear fuel.

Properties of refractory materials for primary aluminum production electrolyzers

Results are provided for a study of changes in the properties of barrier materials during laboratory and industrial tests. Some autopsy results are presented for electrolyzers with a different service life. Directions are indicated for improving barrier layer properties in electrolyzers due to the use of new technology and equipment intended for vibration compaction of materials directly in electrolyzer socles.

Gain and transient photoresponse of quantum well infrared photodetectors: a detailed ensemble Monte Carlo study

We investigate different gain characteristics observed on quantum well infrared photodetectors (QWIPs) fabricated with various material systems, and the effects of barrier material properties on the device characteristics through detailed ensemble Monte Carlo simulations. When the energy spacing between the central and satellite valleys is increased, the improvement in the excited electron lifetime is found to be much stronger than that in the average electron velocity in the device. According to our results, relatively high gain observed in InP/In0.53Ga0.47As QWIPs under large bias is not due to the higher mobility in InP as suggested earlier; it can mainly be attributed to higher excited electron lifetime as a result of relatively large Γ–L energy spacing. We discuss the details of the fast part of the Al0.3Ga0.7As/GaAs QWIP transient photoresponse, which exhibits three regions with different decay characteristics under a short pulse of radiation. The duration of the final region, during which the electrons excited near the emitter are extracted from the collector, is observed to be considerably long due to the dispersion of the photoelectrons. The photoresponse time rapidly decreases with increasing bias under low bias, and nearly saturates at ∼10ps under large bias being ∼40% larger than the average transit time estimated by dividing the device length to the average steady-state electron velocity in device. We also investigate the effects of the interface reflections on the photoresponse time.

The Application of Innovative Materials in Waste Containment Barriers

Barriers are the critical components of waste containment systems such as landfills, slurry walls, grout curtains, permeable walls, and designed covers ~caps!. Examples of such containment systems are illustrated in Fig. 1. For a given set of conditions, the long-term performance of well-constructed, multicomponent containment systems depends on three principal factors: barrier material properties, component dimensions, and system configurations. Barrier layers of waste containment systems serve one or

Integrated electroless metallization for ULSI

In this paper, we present a novel copper interconnect scheme where conducting, barrier and capping layers are deposited by electroless methods. Electroless copper deposition has been demonstrated for sub-0.25 μm metallization on large silicon wafers. In this paper, we extend the use of electroless deposition for the layers under and above the copper. After a short overview of electroless copper and barriers deposition we describe some of the current process modules and the properties of the thin films. Next we review the individual layer properties, describe their integration, and discuss the highlights and problems of the integration of copper, barriers, and capping layers, all deposited by electroless methods. The integrated process features deposition from an aqueous solution of copper and CoW alloys. The metals deposition is due to an electrochemical oxidation-reduction reaction that takes place on the liquid-solid interface. Electroless deposition is autocatalytic and the interconnect materials themselves can serve as seeds for some deposition solutions. In some cases, surface activation is required to initiate the autocatalytic process. We will discuss the issues of the seed layer and will present both ‘wet’ and ‘dry’ seeding methods. The deposition of both copper and the barrier layers is very conformal and we assume that the deposition rate is surface-reaction limited. In addition, we present recent results of the barrier material properties and experimental results of the fully integrated structure with and inlaid-copper technology.