Function Of Membrane Thickness Research Articles

Modeling Water Transport in Polymer Electrolyte Membrane Electrolyzers Using a One-Dimensional Transport Model

In this work, we present a water transport model to quantify the movement of water across Nafion® membranes in a proton exchange membrane electrolyzer as a function of varying operating conditions and membrane parameters. This physics-based model is based on the three main water transport mechanisms: diffusion, electro-osmotic drag, and pressure-driven flow. Three sets of equations are obtained to model the movement of water on the cathode side – I. Material balances for hydrogen and water in the flow channel (z-direction), II. Water movement across the membrane in the x-direction, and III. Expressions for variable membrane properties to serve as model inputs. The condensation of water at the cathode is also modeled to understand the respective transport contributions from the vapor and liquid phases. The coupled equation sets are solved numerically with appropriate boundary conditions. An analytical solution is also obtained for the governing differential equation for the mole fraction of water in the vapor phase. This study is perhaps the first effort for a detailed physics-based transport model to predict the water transport in the electrolyzer in one dimension using the actual measured values for the physical parameters of the system. The model results are compared with the experimental data available for water transport, and a good agreement is observed over the wide range of current, temperature and pressure differentials. Further, with the help of this simple transport model, the numerical analysis is performed to delineate the effect of electrolyzer operating conditions on the net water transport across the membrane, water condensation at the cathode, individual contribution of the transport fluxes, and electrolyzer design. Finally, the model is exercised to simulate the dependence of water transport as a function of membrane thickness. This confirms the validity of the current approach of using thin reinforced membranes by electrolyzer fabricators. Figure 1

Modeling water transport in polymer electrolyte membrane electrolyzers using a one-dimensional transport model

In this paper, we present a one-dimensional transport model for water transport across Nafion® membranes in a proton exchange membrane electrolyzer. This physics-based model is based on the three main water transport mechanisms: diffusion, electro-osmotic drag, and pressure-driven flow. A good agreement is obtained between the model predictions using the measured values of the physical parameters as inputs and the previously reported experimental data. Further, with the help of this simple transport model, the numerical analysis is performed to delineate the effect of electrolyzer operating conditions on the net water transport across the membrane, water condensation at the cathode, individual contribution of the transport fluxes, and electrolyzer design. Finally, the model is exercised to simulate the dependence of water transport as a function of membrane thickness. This confirms the validity of the current approach of using thin reinforced membranes by electrolyzer fabricators.

PFSA Membrane Thickness Impact on Chemical Degradation Rates

As the large-scale commercialization of proton exchange membrane fuel cells (PEMFC) for numerous applications, including heavy-duty trucks draws nearer, there is increasing interest in optimizing fuel cell membranes for both improved efficiency and durability. One of the major membrane attributes being considered for optimization is thickness. The current range of (perfluorosulfonic acid) PFSA membrane thicknesses employed for commercial applications range from 8 -25 µm. As with most adjustable materials parameters, there are a host of properties (cost, gas permeability, proton conductivity, etc.) that require co-optimization to provide the overall preferred position. For example, thin membranes will minimize proton resistance, facilitating high power densities, but will simultaneously allow increased gas crossover fluxes that can contribute to both reduced fuel efficiency and increased oxidative stress. On the other end of the spectrum, thick membranes will decrease gas crossover fluxes, offering improved fuel efficiency while simultaneously decreasing power density. A major question surrounding the tradeoffs of membrane thickness involves the chemical durability impact. Here, we report our investigations of PFSA membrane chemical durability as a function of thickness. For the studies reported here, a thickness series (8, 12 and 20 µm) of ePTFE reinforced Nafion®-like PFSA standalone membranes (SAMs) were prepared.A two-pronged approach was taken for this study. The first involves investigation of intrinsic chemical stability of the ionomer as a function of membrane thickness using an ex-situ H2O2 vapor test. The second investigative mode, which targets the oxidative stress generated by crossover gas flux, employs OCV durability tests of full MEAs. In addition to membrane thickness, gas crossover rates are known to be functions of membrane hydration and gas pressures.1,2 Accordingly, a 3(4-1) fractional factorial experimental design was executed to probe the role of membrane thickness as well as the other factors known to affect gas crossover. The fractional factorial design allows all main effects to be determined and further allows estimation of two factor interactions, if present.References T. Sakai, H. Tanenaka, E, Torikai, “Gas Diffusion in Dried and Hydrated Nations” J. Electrochem. Soc., 1986, 133, 88-92R. Jiang, T. Fuller, S. Brawn, C. Gittleman, “Perfluorocyclobutane and poly(vinylidene fluoride) blend membranes for fuel cells” Electrochimica, Acta, 2013, 110, 306-315

(Invited) Electrochemical Gas Separation

Electrochemical gas separators are electrically powered systems that selectively remove a targeted gas species from a mixture of gases by virtue of electrochemical reactions. Electrochemical separation is an attractive option owing to its higher efficiency and lower cost compared to incumbent technologies like pressure swing adsorption, cryogenic processes, and selective permeation. This work focuses on two specific electrochemical separation processes – (1) separation of hydrogen from a mixture of gases to help develop the hydrogen distribution infrastructure, and (2) nitrogen separation from air for aircraft fuel tank inerting.Reductions in CO2 emission since the beginning of this century by the US electric power sector are mainly attributed to the replacement of coal by natural gas in power plants. Nevertheless, the combustion of natural gas still contributes heavily to global warming and climate change. It is imperative to find alternatives to combustion-based energy technologies and nurture the growth of renewable energy systems. In this scenario, hydrogen is a leading candidate as a carbon-free fuel with high energy density and is expected to play a key role in future energy systems. However, hydrogen faces serious obstacles in its distribution due to the lack of a nationwide hydrogen pipeline network. Developing a dedicated hydrogen pipeline network will be quite expensive, therefore, it is worthwhile to examine whether existing natural gas pipelines could be effectively deployed for hydrogen distribution. This would be accomplished by directly injecting a prescribed amount of hydrogen at the point of production into a natural gas pipeline. Such a mixture of hydrogen and methane is labeled as hythane. While this enables the convenient transport of hydrogen across large distances, the process can only be completed by separating hydrogen from methane at the destination point. Electrochemical hydrogen separation (ECHS) systems built around proton-selective polymer electrolyte membranes (PEMs) represent an effective platform to separate and simultaneously compress hydrogen in a continuous operation. Furthermore, ECHS ensures that the resulting gas is not contaminated by lubrication oil as observed in conventional systems. In ECHS, the hythane mixture enters the anode compartment wherein the hydrogen is selectively dissociated to protons and electrons. The protons are then driven across the PEM by an externally applied voltage to recover hydrogen at the cathode.The first part of this study demonstrates hydrogen purification using low-temperature PEM-based ECHS from various gas mixtures including methane/hydrogen, carbon dioxide/hydrogen, water gas shift effluent, and hythane. ECHS performance is first investigated for pure hydrogen as a function of membrane thickness, cell temperature, and relative humidity of the anode stream. In the second set of experiments, various ratios of methane/hydrogen and carbon dioxide/hydrogen are introduced to examine the effect of hydrogen concentration in the feed gas mixture on ECHS performance. Finally, experiments are performed for hydrogen purification from a water gas shift (WGS) effluent mixture as well as a practical hythane gas feed. ECHS performance for all gas mixtures was benchmarked against the pure hydrogen case. The purity of the separated hydrogen gas was measured to confirm the effectiveness of the method. The results show that ECHS represents a good solution to separate hydrogen from the hythane mixture at the downstream end of the pipeline.Pertinent to the second electrochemical separation process examined here, after the TWA flight 800 disaster due to a fuel tank explosion in 1996, inerting of aircraft fuel tanks became a priority. During fuel tank inerting, an inert gas like nitrogen is supplied to the tank to reduce its flammability. An electrochemical gas separation and inerting system (EGSIS) is a device that generates nitrogen enriched air (NEA) from ambient air by the application of electrical power. EGSIS combines a PEM electrolyzer anode wherein water is dissociated to release oxygen, and a PEM fuel cell cathode where atmospheric air is converted to NEA. Aircraft tank inerting requires varying NEA flowrates (low during takeoff and ascent, and high during descent). In conventional hollow fiber membrane air separation modules typically used in current aircraft, the total membrane surface area is determined by the maximum required NEA flow rate which results in large and expensive modules. On the other hand, the NEA flow rate can be easily controlled in EGSIS by simply adjusting the applied voltage. This portion of the study focuses on results for a single EGSIS cell and its optimization. Various EGSIS stack configurations are also described in order to develop a practical system. Finally, a techno-economic analysis of EGSIS is presented to show that EGSIS can compete favorably with incumbent technologies in terms of fuel usage and cost.

Molecular Dynamics Simulations Based on Polarizable Models Show that Ion Permeation Interconverts between Different Mechanisms as a Function of Membrane Thickness.

Different mechanisms have been proposed to explain the permeation of charged compounds through lipid membranes. Overall, it is expected that an ion-induced defect permeation mechanism, where substantial membrane deformations accompany ion movement, should be dominant in thin membranes but that a solubility-diffusion mechanism, where ions partition into the membrane core with large associated dehydration energy costs, becomes dominant in thicker membranes. However, while this physical picture is intuitively reasonable, capturing the interconversion between these two permeation mechanisms in molecular dynamics (MD) simulations based on atomic models is challenging. In particular, simulations relying on nonpolarizable force fields are artificially unfavorable to the solubility-diffusion mechanism, as induced polarization of the nonpolar hydrocarbon is ignored, causing overestimated free energy costs for charged molecules to enter into this region of the membrane. In this study, all-atom MD simulations based on nonpolarizable and polarizable force fields are used to quantitatively characterize the permeation process for the arginine side chain analog methyl-guanidinium through bilayer membranes of mono-unsaturated phosphatidylcholine lipids with and without cholesterol, resulting in thicknesses spanning from ∼24 to ∼42 Å. With simulations based on a nonpolarizable force field, ion translocation can take place solely through an ion-induced defect mechanism, with free energy barriers increasing linearly from 14 to 40 kcal/mol, depending on the thickness. However, with simulations based on a polarizable force field, ion translocation is predominantly dominated by an ion-induced defect mechanism in thin membranes, which progressively converts to a solubility-diffusion mechanism as the membranes get thicker. The transition between the two mechanisms occurs at a thickness of ∼29 Å, with lipid tails of 22 or more carbon atoms. This situation appears to represent the upper limit for ion-induced defect permeation within the current polarizable models. Beyond this thickness, it becomes energetically preferable for the ion to dehydrate and partition into the membrane core-a phenomenon that cannot be captured using the nonpolarizable models. Induced electronic polarizability therefore leads not just to a shift in permeation energetics but to an interconversion between two strikingly different physical mechanisms. The result highlights the importance of induced polarizability in modeling lipid membranes.

Molecular simulations of phenol and ibuprofen removal from water using multilayered graphene oxide membranes

We present here non-equilibrium molecular dynamic simulations concerning the separation of phenol and ibuprofen as impurities compounds (ICs) in water by novel graphene oxide (GO) membranes. The coupling between water permeability and impurity rejection is studied as a function of membrane thickness and concentration, focusing on the underlying molecular phenomena. Results show that water permeability decreases as the number of layers increases. Moreover, molecular sieving can be achieved by tuning the number of GO layers and the surface chemistry of the sheet: water flow through layers is up to 20% faster than that in graphene layers, because of strong hydrogen bonded interactions with the oxygenated groups. Analysis of the simulation results suggests that upon adsorbing on the GO surface, the translational motion of ICs in water would be supressed. Nevertheless, hydrophilicity affects the permeability for membranes with high O/C ratio, owing to these strong hydrogen bonds. Furthermore, 100% rejection for the ICs can be obtained for most of the GO membranes with four layers. This study elucidates the important role of hydrophilic interactions in GO membranes to become ideal candidates for removal of organic pollutants from water, showing the applicability of molecular simulations to obtain molecular insights into this problem.

Investigating the factors that influence resistance rise of PIM-1 membranes in nonaqueous electrolytes

As redox active macromolecules are introduced to the materials repertoire of redox flow batteries (RFBs), nanoporous membranes, such as polymers of intrinsic microporosity (PIMs), are emerging as a viable separation strategy. Although their selectivity has been demonstrated, PIM-based membranes suffer from time-dependent resistance rise in nonaqueous electrolytes. Here, we study this phenomenon as a function of membrane thickness, electrolyte flow rate, and solvent washing using a diagnostic flow cell configuration. We find that the rate and magnitude of resistance rise can be significantly reduced through the combination of low electrolyte flow rate and solvent prewash. Further, our results indicate that, since the increase is not associated with irreversible chemical and structural changes, the membrane performance can be recovered via ex-situ or in-situ solvent washes.

Modelling of water transport through mixed‐ion conducting dense ceramics

AbstractThis study develops and demonstrates a model that characterizes defect transports, responsible for water transport within dense ceramics, and calculates the diffusion coefficients for those defects. The multi‐species mass transfer processes within yttrium doped barium cerates are modelled by applying the Nernst‐Planck equation to the system. The Nernst‐Planck equation with suitable boundary conditions is adopted to compute defect diffusion coefficients in COMSOL Multiphysics. All related equations, based on charge and defect conservation, are solved numerically and validated experimentally. The model also predicts the concentration distribution of the defects and potential profiles throughout the membranes. The results provided convenient insights about the water transport and charge distribution as a function of membrane thickness.

Oil–Water Separation Using Superhydrophobic PET Membranes Fabricated Via Simple Dip‐Coating Of PDMS–SiO2 Nanoparticles

AbstractThe surfaces of commercially available polyester (PET) and polypropylene (PP) are superhydrophobically modified via the deposition of polydimethylsiloxane (PDMS)‐coated SiO2 nanoparticles (P‐SiO2) and PDMS binder. The adhesion of P‐SiO2 is stronger on PET than on PP due to a stronger chemical interaction between PET and PDMS, which is attributed to the higher surface energy of PET than PP. The waterproof ability and oil separation rate of the P‐SiO2‐coated PET (dip‐PET) membranes are studied as a function of membrane thickness, and the influence of oil viscosity on the oil separation efficiency is investigated. Optimal membrane thickness should be selected in a given environment for the facile oil–water separation and the dip‐PET membrane is chemically stable and can be used repetitively for oil–water separation. Finally, an automated prototype instrument is introduced for the dip‐coating process. It is suggested that our dip‐PET is a promising solution for oil–water separation in real‐world oil‐spill applications.

Guidelines for selecting coating materials for a high oxygen permeation flux in a fluorite-rich dual-phase membrane

It is necessary to understand the role of surface modification in the oxygen permeation mechanism because the active coating layer on the ceramic membrane is important for dramatically enhancing the oxygen permeation flux. The effect of coating layers on oxygen permeation in a fluorite-rich dual-phase membrane [80vol% Ce0.9Gd0.1O2−δ (GDC): 20vol% La0.6Sr0.4Co0.2Fe0.8O3−δ(LSCF)] has been investigated as a function of membrane thickness and temperature to elucidate the extent of oxygen flux improvement due to surface modification. Various perovskite materials such as La0.6Sr0.4CoO3-δ (LSC), La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), SrTi0.5Fe0.5O3-δ (STF), La0.7Sr0.3MnO3-δ (LSM), as well as the LSM/Ce0.9Gd0.1O2−δ (GDC)composite, have been adopted as the coating layers to enhance the oxygen permeation flux. The role of surface modification in the dual-phase membrane on the enhancement of oxygen flux has been systematically studied from the point of view of oxygen exchange kinetics and bulk diffusion. The oxygen permeation fluxes increased in the order of LSC > STF ≈ LSCF > LSM/GDC > LSM coating materials. The surface exchange kinetics coefficient (k) of the membrane with various coating materials can be calculated based on the characteristic thickness and bulk diffusion coefficient. The k values of the coated dual-phase membrane follow the k values of the coating materials. This result implies that the remarkable enhancement of oxygen flux in the dual-phase membrane with surface modification is closely related to the surface exchange kinetics of the coating materials.

On Designing of Membrane Thickness and Thermal Conductivity for Large Scale Membrane Distillation Modules

Membrane distillation has the potential to concentrate solutions to their saturation level, thus offering the possibility to recover valuable salts from the solutions. The process performance and stability, however, is strongly dependent upon the features of membranes applied. In addition, several other parameters, membrane thickness and thermal conductivity significantly affect the process performance. These parameters are of fundamental importance in the selection of optimum module length due to their influence on temperature and flux profiles along the fiber. In the current study, the experimental data from a lab-scale membrane distillation plant has been modeled to analyze the interrelated effect of membrane thickness, thermal conductivity and module length on process performance. It has been observed that flux initially improves by decreasing the membrane thickness followed by a decrease and ultimately negative value. For any given fiber length and thickness, the flux can be greatly improved by decreasing the membrane-conductivity. The length that corresponds to the highest flux and the maximum fiber length ensuring a positive flux have been identified as a function of membrane thickness and thermal conductivity.

Water transport through short side chain perfluorosulfonic acid ionomer membranes

Liquid and water vapour transport through short side chain (SSC) perfluorosulfonic acid (PFSA) ionomer membranes are measured as a function of membrane thickness (24–96µm) and temperature (25–85°C). Three types of water permeation techniques are used in this work and are based on applied chemical potential gradients across a membrane. These are: liquid-liquid permeation (LLP) in which both sides of membrane are in contact with liquid water; liquid-vapour permeation (LVP) where one side of the membrane is exposed to liquid and the other is exposed to vapour; and vapour-vapour permeation (VVP) where both sides of the membrane are exposed to water vapour. Within the SSC series, the increase in permeance for VVP upon decreasing membrane thickness is not as significant as compared to LLP due to the larger interfacial water transport resistance (Rinterfacial) observed for membranes exposed to vapour. The study of LVP and VVP transport resistances indicates that Rinterfacial plays dominate role in determining the overall membrane resistance, even for a thick SSC membrane. It is speculated that Rinterfacial is the result of water depletion layer caused by membrane dehydration at the membrane interface. The LVP interfacial resistance for SSC membranes is similar to that found for long side chain PFSA ionomer membranes such as, Nafion®, even though SSC membranes possess significant lower internal LVP permeation resistance. Water permeance determined by LLP, LVP and VVP measurements are all found to increase with temperature, due to the increased water volume fraction (Xv) and an increase in the effective hydrophilic pore size. The activation energy of LLP, LVP and VVP water permeation are calculated to be 16.3, 40.2 and 43.1kJmol−1 respectively, which is lower than that of Nafion under similar conditions.

Effect of microstructure and thickness on oxygen permeation of La2NiO4+δ membranes

Lanthanum nickelate, La2NiO4 (LNO) powders were synthesized by a sol–gel method. These powders were compacted to obtain LNO membranes. The grain size effect on the permeation of LNO membranes was examined by variation of the sintering time of membranes from 5 to 48h. The microstructure of membranes was analyzed using scanning electron microscopy (SEM) and the grain size was determined using a statistical approach. The grain size was observed to increase with the dwell time following a power law. The permeation of the membranes increased with increasing dwell time up to 15h. For dwell time of 48h, the permeability decreased sharply. The oxygen permeation of LNO membranes was also measured as a function of membrane thickness in the same temperature range. With the aim of looking at the effects of bulk diffusion and kinetics of surface-exchange, the membrane thickness was varied from 0.8 to 1.3mm. The characteristic critical thickness (LC) of the membrane, at which the surface exchange kinetics becomes dominant, was found to be 1.0mm in the temperature range of 700–1000°C.

Composite membranes for alkaline electrolysis based on polysulfone and mineral fillers

Mineral-based membranes for high temperature alkaline electrolysis were developed by a phase inversion process with polysulfone as binder. The long-term stability of new mineral fillers: wollastonite, forsterite and barite was assessed by 8000 h-long leaching experiments (5.5 M KOH, 85 °C) combined with thermodynamic modelling. Barite has released only 6.22 10–4 M of Ba ions into the electrolyte and was selected as promising filler material, due to its excellent stability. Barite-based membranes, prepared by the phase inversion process, were further studied. The resistivity of these membranes in 5.5 M KOH was investigated as a function of membrane thickness and total porosity, hydrodynamic porosity as well as gas purities determined by conducting electrolysis at ambient conditions. It was found that a dense top layer resulting from the phase inversion process, shows resistivity values up to 451.0 ± 22 Ω cm, which is two orders of magnitude higher than a porous bulk membrane microstructure (3.89 Ω cm). Developed membranes provided hydrogen purity of 99.83 at 200 mA cm−2, which is comparable to previously used chrysotile membranes and higher than commercial state-of-the-art Zirfon 500utp membrane. These cost-effective polysulfone – barite membranes are promising candidates as asbestos replacement for commercial applications.

Dramatically Enhanced Oxygen Fluxes in Fluorite-Rich Dual-Phase Membrane by Surface Modification

Dual-phase ceramic membranes with very high oxygen flux have been designed by taking into account the volume fraction of the fluorite phase, membrane thickness, and surface modification. The oxygen flux of Ce0.9Gd0.1O2−δ–La0.6Sr0.4Co0.2Fe0.8O3−δ (GDC–LSCF) dual-phase membranes has been systematically investigated as a function of membrane thickness and volume fraction of the fluorite phase with or without surface modification. The percolation threshold of the composites for electronic conduction has been determined to be about 20 vol % of LSCF by general effective-medium theory. The oxygen flux of uncoated fluorite phase-rich membrane (80 vol % GDC–20 vol % LSCF) with 30-μm thickness exhibits a low oxygen flux (8.0 × 10–3 mL·cm–2·min–1 at 850 °C) under an air/He gradient, indicating that the permeation is controlled by only the surface-exchange kinetics of GDC. With both sides coated with La0.6Sr0.4CoO3−δ (LSC), the flux of the membrane (3.6 mL·cm–2·min–1 at 850 °C) has been dramatically enhanced by about...

Development of Mixed-Conducting Membranes for Hydrogen Separation

As the clean energy demands of the world continue to increase, so too will the use of hydrogen containing fuels. For harvesting “green” energy, hydrogen of sufficient purity will need to be extracted either from hydrogen-rich fuel sources or post-processing flue gases, requiring efficient separation of hydrogen from the many byproducts that arise from hydrogen production. This pure hydrogen can then be utilized for various power generation processes. While there are many different materials to be chosen as membrane constituents for this separation, proton-conducting ceramics represent a particularly appealing option for purification of hydrogen as a fuel source of solid oxide fuel cells. In these applications, the relatively high operating temperature of the fuel cell allows the integration of ceramic membranes with promising proton conductivity that is higher than or comparable to other hydrogen separation material systems. Additionally, these proton conductors need to attain high permeation rates with low fabrication costs[1]. Recently, a ceramic electrolyte composed of BaZr0.1Ce0.7Y0.1Yb0.1O3-d (BZCYYb) has demonstrated high proton conductivity that has spurred research interest on its application in ceramic electrolyte and hydrogen membrane fields. [2]. In this work, we examine two main features of membrane performance, optimal hydrogen flux of the membrane and improved microstructure through scalable manufacturing techniques.The membrane consists of a Ni-BZCYYb dense layer supported by a porous Ni-BZCYYb. The first part of the work identifies the optimal hydrogen flux through variation of the nickel content in an asymmetric dense Ni-BZCYYb pellet. The determination of the transference number for the ceramic phase allows us to optimize the electrical conductivity brought on by the nickel. The hydrogen flux through the Ni-BZCYYb was determined as a function of membrane thickness and hydrogen partial pressure. The hydrogen flux was determined by using a mass spectrometer, which correlates the measured hydrogen partial pressure to amount of hydrogen present in a known sweeping gas atmosphere. Results have shown a hydrogen flux of 0.714 ml/cm2min under 100% hydrogen at 750˚C.The microstructure also plays an important role in the performance of an asymmetric permeation membrane. For dense ceramic membranes, the ohmic permeation resistance from the proton conduction is inversely proportional to the thickness of the membrane. By using a tape-cast method, the thickness of the dense layer can be tailored down to about 10 microns. The results demonstrate an optimized membrane in terms of nickel content and thickness of asymmetric dense/porous layers. This demonstrates the ability to fabricate a cermet hydrogen permeation membrane using a large-scale, industry method.Further, various catalysts that may enhance hydrogen adsorption, dissociation, and oxidation on the surface of the hydrogen separation membranes are also explored and will discussed in the presentation.

MICRO-FINITE ELEMENT MODELING OF WRINKLE FORMATION FOR CELL LOCOMOTION APPLICATIONS

We developed a generic numerical procedure using the finite element method (FEM) for modeling wrinkles on an elastic thin membrane. The geometric characterization of wrinkles formed in an elastic membrane, which is caused by a crawling cell, may help in understanding the forces acting between a cell and its compliant substrate. In this study, the equivalent nodal forces, obtained from the virtual changes in the element internal energy, were differentiated to calculate the stiffness matrix. Micro-wrinkles can be computed as a function of membrane thickness which affects the stiffness matrix. This model may be used for applications in cell mechanobiology.

Preparation, electrochemical characterization and antibacterial study of polystyrene-based magnesium–strontium phosphate composite membrane

The electrochemical characterizations of polystyrene-based magnesium–strontium phosphate (MSP) composite membrane have been worked on, as a function of membrane thickness, porosity and moisture content etc. Polystyrene-based magnesium–strontium phosphate composite membrane was characterized by XRD, FTIR, SEM, and antibacterial studies. The membrane was found to be crystalline in nature with uniform arrangement of particles, no sign of visible cracks and shows excellent inhibitory results against Escherichia coli and Pseudomonas aeruginosa bacteria. The membrane potentials of inorganic membrane were measured with uni-univalent electrolytes solution using saturated calomel electrodes and followed the order LiCl>NaCl>KCl, thus, the membrane was found to be cation selective. Membrane potential data have been used to calculate transport number, mobility ratio, distribution coefficient, charge effectiveness, and also to derive the fixed-charge density which is a central parameter governing the membrane phenomena by utilizing the Teorell, Meyer, and Sievers method. The order of surface charge density for uni-univalent electrolytes solution was found to be LiCl<NaCl<KCl.

A Prototype of Electrochemical Sensor for Measurements of Carbonyl Compounds in Air

AbstractThe paper presents the results of investigation on a prototype sensor for measurements of benzaldehyde and formaldehyde in air. Sensitivity, limit of quantification and coefficient of selectivity of the sensor have been determined as a function of membrane thickness and electrode type using square wave voltammetry (SWV) technique. The working and counter electrodes were made of platinum and gold. Ionic liquids 1‐hexyl, 3‐methylimidazolium bis(trifluoromethanesulfonyl)imide constituted an internal electrolyte. Polydimethylsiloxane (PDMS) membrane separated gaseous medium from the electrolyte.

Synthesis, characterization and electrochemical study of calcium phosphate ion-exchange membrane

The transport properties of polystyrene-based calcium phosphate membrane have been studied as a function of membrane thickness, porosity and moisture content etc. All these properties were observed to decrease with the increase in applied pressure. Polystyrene-based calcium phosphate membrane was characterized by XRD, FTIR and SEM studies. The membrane was found to be crystalline in nature with uniform arrangement of particles and no sign of visible cracks. Membrane potential, which is a reliable and measurable parameter, was used to characterize the charge property of membrane. The membrane potential values of the composite membrane for various electrolytes followed the order LiCl > NaCl > KCl, and the membrane was found to be cation-selective. The Teorell, Meyer, and Sievers method was used to investigate the transport number of ions, mobility ratio, distribution coefficient, and charge density of the membrane. The order of surface charge density for uni-univalent electrolytes solution was found to be LiCl < NaCl < KCl.