Concentration Polarization Effects Research Articles

Nanoarchitectonics in Advanced Membranes for Enhanced Osmotic Energy Harvesting.

Osmotic energy, often referred to as "blue energy", is the energy generated from the mixing of solutions with different salt concentrations, offering a vast, renewable, and environmentally friendly energy resource. The efficacy of osmotic power production considerably relies on the performance of the transmembrane process, which depends on ionic conductivity and the capability to differentiate between positive and negative ions. Recent advancements have led to the development of membrane materials featuring precisely tailored ion transport nanochannels, enabling high-efficiency osmotic energy harvesting. In this review, ion diffusion in confined nanochannels and the rational design and optimization of membrane architecture are explored. Furthermore, structural optimization of the membrane to mitigate transport resistance and the concentration polarization effect for enhancing osmotic energy harvesting is highlighted. Finally, an outlook on the challenges that lie ahead is provided, and the potential applications of osmotic energy conversion are outlined. This review offers a comprehensive viewpoint on the evolving prospects of osmotic energy conversion.

Influence of pore size distribution and applied cross-flow on ion rejection and separation

To improve the understanding of the separation mechanism of ions through membrane filtration, ion transport through a membrane with non-uniform pore sizes is investigated theoretically by solving the coupled Poisson-Nernst-Planck and Navier-Stokes equations under various conditions. The model focuses on a membrane with pore sizes following a log-normal distribution and considers the flow interaction between pores. The rejection performance for different pore arrangements is addressed for a rational assessment of the best ion rejection and selectivity in membrane filtration processes. In addition to the dead-end setting, a cross-flow is applied on the feed side to alleviate the concentration polarization effect. In the presence of positively charged nanopore surfaces, both the cases of a single salt (NaCl) and mixed salts (NaCl, MgCl2) present in the liquid are considered. We show that the uniform pore system outperforms non-uniform ones in terms of the overall rejection and selectivity between salts. When pore size polydispersity is present, the arrangement among the larger and smaller pores impacts the local rejection and volumetric flux of pores. Moreover, the competitive transport between cationic co-ions makes Mg2+ demonstrate generally higher rejection in all the pore arrangements considered. As uniform pores show lower flow rates, the separation efficiency of ions may be improved by pore size polydispersity at the same concentration and pressure difference.

Surface polarity modulation enables high-performance polyamide membranes for separation of polar/non-polar organic solvent mixtures

Achieving highly selective separation of organic mixtures is crucial to modern fine chemicals and pharmaceutical industries. The membrane-based organic solvent reverse osmosis (OSRO) technology is expected to break through this barrier. The key to achieving the separation of organic mixed liquids is to design the OSRO membrane as needed based on the physical and chemical properties of the target separation solvent. However, this poses a huge challenge to traditional OSRO membranes. In this work, we report composite polyamide (PA) OSRO membranes with ultrahigh polar/non-polar organic mixture selectivity. The surface polarity of the composite PA membrane is increased by coating a layer of Fe3+/tannic acid (Fe3+/TA) layer on the surface of the PA membrane. The enhanced surface polarity increases the interaction difference between polar and non-polar solvents and the membrane. And a polarization layer is formed on the membrane surface, which weakens the concentration polarization effect on the membrane surface. Under high-concentration feed liquid (the mass ratio of methanol/hexane is 7:3), the separation factor of the prepared membrane reaches 218, which is the highest value of all OSRO membranes reported so far. For the first time, we establish a partial flux analysis for the OSRO process. This analysis unravels the pressure, concentration dependence, and sensitivity of separation performance. It provides novel insights into the design of high-performance OSRO membranes.

A preliminary model of water and salt transport in a laboratory scale pressure-retarded osmosis (PRO) module

Nowadays, more and more attention is being paid to the production of green energy. Recently, energy from salinity gradients has also attracted interest. One such process that can generate useful work is the pressure-retarded osmosis (PRO), which uses a semi-permeable membrane to separate the feed and pressurized draw solutions. The semi-permeable membrane allows the transport of solvent (water) from the feed solution (diluted low pressure) side to the draw solution (concentrated high pressure) side, and thus, the excess of pressurized water on the draw side can be used to generate power, i.e., by expansion in the turbine. This work presents a preliminary numerical model developed to study the water and NaCl salt transport through the semi-preamble membrane and in the PRO module designed to perform experimental studies. The model was first verified for simple 2D module geometry. It was then used to study the flow through a simplified 3D module, mimicking the real one used in laboratory-scale experiments. The influence of the hydrodynamic pressure and the NaCl draw solution’s mass flow rate in the module on the energy generation efficiency was examined. The maximum power density obtained for half the osmotic pressure of the NaCl draw solution (i.e., for 28 bar) was found to be equal to approximately 4 W/m2. An increase in the flow rate of the draw solution causes a decrease in the thickness of the boundary layer at the membrane, which reduces the effect of the external concentration polarization. This results in an increase in the concentration difference on either side of the membrane, contributing to a non-linear increase in power density depending on this mass flow rate. Increasing the average velocity from 0.02 m/s to 0.1 m/s increases the power density by up to 80%, from approximately 2.6 to 4.7 W/m2.

Li6.28La3Zr2Al0.24O12-reinforced Single-ion Conducting Composite Polymer Electrolyte for Room-Temperature Li-Metal Batteries

Composite polymer electrolytes composed of inorganic fillers and organic polymers are promising electrolyte candidates for Li metal batteries, with benefits of improved safety and suppressed lithium dendrite growth. However, a severe concentration polarization effect often occurs when using conventional dual-ion electrolytes, and the increase in internal impedance during cycling results in decreased lifespan of the battery. To address this challenge, a plasticized single-ion conducting composite polymer electrolyte (SICE) was designed and fabricated by polymerizing the monomers of lithium (4-styrenesulfonyl) (trifluoromethanesulfonyl) imide (LiSTFSI) and poly(ethylene glycol) methyl ether acrylate (PEGMEA), crosslinker poly(ethylene glycol) diacrylate (PEGDA), silane-modified Li6.28La3Al0.24Zr2O12 nanofibers (s@LLAZO NFs), along with a PEG-based plasticizer tetraethylene glycol dimethyl ether (TEGDME), by heat-initiation. The anions were restrained and delocalized so that only Li cation migration occurred during the charging/discharging process, leading to a superior lithium-ion transference number. The s@LLAZO NFs enabled direct monomer grafting with the polymer matrix, resulting in controlled formation of an organic-inorganic network with increased filler content and improved filler distribution in the SICE system. The SICE membrane exhibited high ionic conductivity at room temperature, reduced activation energy and excellent oxidation stability. Most importantly, the all-solid-state Li-metal batteries assembled with the fabricated SICE demonstrated stable long-term cycling performance and remarkable rate capability at room temperature.

Highly efficient and direct recovery of low-pressure hydrogen isotopes from tritium extraction gas by PdY alloy membrane permeator

Low-pressure hydrogen recovery is crucial for the fusion reactor deuterium-tritium fuel cycle, and the usual treatment is achieved through multiple steps of enrichment and separation, which has the drawbacks of complex processes and high energy consumption. In this work, a membrane permeator including 12 sets of Pd92Y8 at% alloy tubes has been investigated for the permeability and extraction of hydrogen in low-pressure mixtures. The hydrogen permeation through dense Pd-based membrane mechanism and corresponding Sieverts’ exponents have been verified. The concentration polarization effect is deducted from the results. Through pure hydrogen permeation test, the cold-rolling 80 μm thick Pd92Y8 at% membrane has hydrogen permeability at 400 °C of 3.43×10−8 mol∙m−1∙s−1∙Pa−0.5, which is higher than that of PdAg alloy membrane under the same conditions. Highly efficient recovery efficiency has been achieved for low hydrogen pressure mixtures, and the PdY alloy membrane permeator with 678 cm2 effective area could reach around 95% hydrogen extraction recovery for 0.1 mol% hydrogen-helium mixture and 97.74% recovery for 0.33 mol% at the rate of 21 standard liter per minute (SLM). It indicates that the PdY alloy membrane permeation can be an alternative solution for efficiently recovering low-pressure hydrogen isotopes in tritium extraction gas.

PPS/TA-PEI/β-FeOOH membranes with powerful photo-Fenton self-cleaning capability for efficient oil–water emulsion separation

Polyphenylene sulfide (PPS) microporous membranes have garnered extensive research enthusiasm concerning their outstanding permeation performance and separation accuracy in treating oily wastewater. Nevertheless, the inherent hydrophobic chemical structure, along with the noticeable concentration polarization effect, predisposes them to severe membrane contamination during the separation process. Accordingly, it is desirable to design a PPS self-cleaning membrane with superior anti-fouling capability, fast transport, and remarkable flux recovery. This study marks the first combination of PPS membrane materials with the photo-Fenton process. In detail, the polyphenol (tannic acid, TA)-polycation (polyethyleneimine, PEI)-metal ion (Fe3+) double cross-linking coatings were first assembled on the PPS substrate surface. Subsequently, β-FeOOH photocatalysts were synthesized through in-situ mineralization to further strengthen the hydrophilicity of the membranes. The obtained PPS/TA-PEI/β-FeOOH composite membrane achieved exceptional separation of diverse oil-in-water (O/W) emulsions. The PPS/TA-PEI/β-FeOOH membranes exhibited in-air superhydrophilic and under-water superoleophobicity, exhibiting under-water oil contact angles greater than 151° for diverse oil agents. The fabricated composite membranes displayed high permeability (a flux of the petroleum ether-in-water (P/W) emulsion reached 3400.5 L m−2h−1 bar−1 driven by a pressure of 0.05 MPa) along with ideal oil rejection (98.6 %). Significantly, the PPS/TA-PEI/β-FeOOH membrane possessed powerful photo-Fenton self-cleaning capability, and its flux recoveries of the contaminated membrane exceeded 90.3 % for varied O/W emulsions after being cleaned by visible light for 10 min. We believe that our research presents a novel approach for the exploitation of PPS-based photo-Fenton self-cleaning membranes, which also exhibit great applicative potential in oily wastewater treatment.

Hydrogen Flux Inhibition of Pd-Ru Membranes under Exposure to NH3.

The hydrogen flux inhibition of Pd-Ru membranes under exposure to 1-10% NH3 at 673-773 K was investigated. The Pd-Ru membranes were characterized by XRD, SEM, XPS, and hydrogen permeation tests. The results show that when exposed to 1-10% NH3 at 723 K for 6 h, the hydrogen flux of Pd-Ru membranes sharply decreases by 15-33%, and the decline in hydrogen flux becomes more significant with increasing temperatures. After the removal of 1-10% NH3, 100% recovery of hydrogen flux is observed. XPS results show that nitrogenous species appear on the membrane surface after NH3 exposure, and the hydrogen flux inhibition may be related to the competitive adsorption of nitrogenous species. By comparing the hydrogen flux of Pd-Ru membranes exposed to 10% NH3 with 10% N2, it is indicated that the rapid decrease in hydrogen flux is due to the concentration polarization and competitive adsorption of nitrogenous species. The competitive adsorption effect is attenuated, while the concentration polarization effect becomes more pronounced with increasing temperature.

Locational enrichment of low-abundance analytes through force-environment-modulation microsystem with ion concentration polarization

Ion concentration polarization (ICP) effect in micro-nanofluidic devices can concentrate low-concentration molecules. In this paper, we proposed a novel ICP-based enrichment system with horizontal barriers that adjust the force environment of charged particles, to achieve specific locational analytes enrichment. Mechanism of analyte enrichment through force modulation is revealed through numerical simulation using microchannels with varied channels widths, which is further validated through physical experiment. Overall, a specific target-oriented structure and load regulation method was proposed, under which the low-abundance analytes could be locationally concentrated by ∼ 4000 times. This study is expected to develop an innovative method for specifically locational ion enrichment in terms of scientific principles, providing theoretical and technical support for concentration and detection of charged substances in both research and industry such as biology, environment, chemistry studies, etc.

Predicting forward osmosis performance with synthesized polyamide-based membrane: An integrated machine learning (MATLAB and ANN) and economic analysis framework

Forward Osmosis (FO) has emerged as a highly promising membrane-based water treatment process owing to its intrinsic advantages, such as low energy requirements and the potential for high water recovery. The lab-prepared highly efficient thin film composite (TFC) FO membranes that were used in this research work. The resultant polyamide-based FO membrane showed exceptional performance, notably achieving a high-water flux of 60.94 ± 3.5 L/m2.h and a constrained solute flux of 1.52 ± 0.08 g/m2.h. Machine learning methodologies are strategically employed in this study to construct predictive models for FO membrane performance. Notably, the accuracy of the van't Hoff equation's linear assumption is significantly enhanced by introducing an osmotic pressure calculation based on water activity, considering the nuanced effects of external and internal concentration polarization. The research employs MATLAB software alongside an artificial neural network (ANN) to develop predictive models. MATLAB facilitates the creation of a comprehensive theoretical model, offering insights into forecasting water flux through FO membranes by systematically analyzing diverse membrane parameters and their impact on performance. Concurrently, the ANN model was employed to predict the permeate flux for the laboratory-scale FO membrane system, utilizing the input parameters within the network's training range (R2 > 0.91). An economic assessment is also conducted to estimate the projected membrane cost, a pivotal determinant of system viability. Collectively, these investigations yield valuable insights into the intricacies of FO membrane design and optimization, elucidating their performance dynamics in water treatment and allied applications. This research significantly contributes to the ongoing quest to develop more efficient and precise membrane processes.

Theoretical Analysis of the Influence of Spacers on Salt Ion Transport in Electromembrane Systems Considering the Main Coupled Effects.

This article considers a theoretical analysis of the influence of the main coupled effects and spacers on the transfer of salt ions in electromembrane systems (EMS) using a 2D mathematical model of the transfer process in a desalting channel with spacers based on boundary value problems for the coupled system of Nernst-Planck-Poisson and Navier-Stokes equations. The basic patterns of salt ion transport have been established, taking into account diffusion, electromigration, forced convection, electroconvection, dissociation/recombination reactions of water molecules, as well as spacers located inside the desalting channel. It has been shown that spacers and taking into account the dissociation/recombination reaction of water molecules significantly change both the formation and development of electroconvection. This article confirms the fact of the exaltation of the limiting current studied by Harkatz, where it is shown that the current (flux) of salt ions increases when the dissociation reaction begins by a certain value called the exaltation current, which is proportional to the flow of water dissociation products. A significant combined effect of electroconvection and dissociation/recombination reactions as well as the spacer system in the desalting channel on the transport of salt ions are shown. The complex, nonlinear, and non-stationary interaction of all the main effects of concentration polarization and spacers in the desalting channel are also considered in the work.

A finite element model for concentration polarization and osmotic effects in a membrane channel

AbstractIn this article, we study a mathematical model that represents the concentration polarization and osmosis effects in a reverse osmosis cross‐flow channel with dense membranes at some of its boundaries. The fluid is modeled using the Navier–Stokes equations and the solution‐diffusion is used to impose the momentum balance on the membrane. The scheme consist of a conforming finite element method with the velocity–pressure formulation for the Navier–Stokes equations, together with a primal scheme for the convection–diffusion equations. The Nitsche's method is used to impose the permeability condition across the membrane. Several numerical experiments are performed to show the robustness of the method. The resulting model accurately replicates the analytical models and predicts similar results to previous works. It is found that the submerged configuration has the highest permeate production, but also has the greatest pressure loss of all three configurations studied.

Atmospheric water harvesting by osmotic distillation and direct contact membrane distillation using hydrophobic hollow fiber membranes

The use of a liquid desiccant air dehumidifier is an energy-efficient technology that can improve both indoor air temperature and humidity. However, the risk of concentrated liquid desiccant leakage into the air conditioning system during dehumidification can corrode the system, negatively impact indoor air quality, and potentially harm residents. To address this issue, this study investigates the effectiveness of osmotic distillation (OD) and direct contact membrane distillation (DCMD) for dehumidification and regeneration, respectively. The study analyzes the impact of inlet operating parameters, including liquid desiccant concentration, temperature, and flow rate, and air flow rate on the dehumidification performance and stability of the OD process. Calcium chloride was utilized as the liquid desiccant in this study. The results indicated that the dehumidification performance of the OD process improved with a higher desiccant concentration and lower desiccant temperature. However, the desiccant flow rate did not have a significant impact on dehumidification performance. Furthermore, the dehumidification performance decreased with a higher inlet air flow rate, but the moisture removal rate increased. The OD process demonstrated stable operation during the dehumidification process. DCMD was effective for desiccant regeneration, and no scaling occurred due to the deposition of calcium chloride crystals. However, the permeation flux of DCMD decreased as the feed concentration increased due to a decline in the feed vapour pressure and an increase in concentration polarization effect. In conclusion, the experimental results indicated that OD can effectively dehumidify humid air, while DCMD is a viable option for desiccant regeneration.

Investigation of CO2 Absorption Rate in Gas/Liquid Membrane Contactors with Inserting 3D Printing Mini-Channel Turbulence Promoters.

The CO2 absorption by Monoethanolamine (MEA) solutions as chemical absorption was conducted in the membrane gas absorption module with inserting 3D mini-channel turbulence promoters of the present work. A mathematical modeling of CO2 absorption flux was analyzed by using the chemical absorption theory based on mass-transfer resistances in series. The membrane absorption module with embedding 3D mini-channel turbulence promoters in the current study indicated that the CO2 absorption rate improvement is achieved due to the diminishing concentration polarization effect nearby the membrane surfaces. A simplified regression equation of the average Sherwood number was correlated to express the enhanced mass-transfer coefficient of the CO2 absorption. The experimental results and theoretical predictions showed that the absorption flux improvement was significantly improved with implementing 3D mini-channel turbulence promoters. The experimental results of CO2 absorption fluxes were performed in good agreement with the theoretical predictions in aqueous MEA solutions. A further absorption flux enhancement up to 30.56% was accomplished as compared to the results in the previous work, which the module was inserted the promoter without mini channels. The influences of the MEA absorbent flow rates and inlet CO2 concentrations on the absorption flux and absorption flux improvement are also illustrated under both concurrent- and countercurrent-flow operations.

The effect of concentration polarization and chemical interactions on electrochemical hydrogen pump

Electrochemical hydrogen pump is expected to play an important role in, e.g., H2 extraction from natural gas pipelines, by-product hydrogen purification. The influence of typical concomitant CH4 and CO2 on electrochemical hydrogen pump is systematically investigated in this study over a wide range of gas content (CH4 or CO2: 10-80 %) and temperature (26-60 °C), with the focus on two main inhibition effects, i.e., concentration polarization and chemical interaction. An Faradaic efficiency of 86–96 %, i.e., below 100 %, is obtained as to the H2/CH4 mixture separation due to concentration polarization effect, which is even lower in case of H2/CO2, due to additional chemical interactions between CO2 and Pt anode catalysts. The inhibition of concentration polarization is more significant than that of chemical interactions, and the former can be suppressed by increasing the operating temperature and pressure due to enhance catalytic activity and proton conductivity. As to these two gas mixtures, the energy consumption ranged from 0.2 to 2.0 kWh/m3 with the increase of applied current from 125 to 1250 mA. The electrochemical pump exhibits limited H2 purity of 98.6 %–99.7 % due to the existence of nafion membrane defects, which requires to be further improved.

High permeability PEG/MXene@MOF membrane with stable interlayer spacing and efficient fouling resistance for continuous oily wastewater purification

Unstable interlayer spacing of lamellar membranes would be rapidly compressed and narrowed under normal high flowrates and concentration polarization effect contributes to reduced permeation and fouling resistance. Herein, a large permeability PEG/MXene@MOF membrane with stable interlayer spacing and superior antifouling property was created via facile interface self-assembly strategy. Metal-organic framework (MOF, UiO-66-NH2) nanoparticles as supports constructed an intercalation-induced structure with hierarchical Ti3C2Tx (MXene) nanosheets, which effectively regulated the interlayer spacing and improved permeability. Hydrophilic polyethylene glycol (PEG) further enhanced the stability of intercalation structure via hydrogen bonding, so that the PEG/MXene@MOF membrane demonstrated excellent swelling resistance with an average layer spacing expansion of only 0.05 nm even after immersion in water for 8 days. Moreover, MOF particles increased the lamellar roughness and interlayer water retention capacity, resulting in the PEG/MXene@MOF membrane with remarkable separation selectivity and powerful fouling resistance (UWOCA >156°, UWOSA <5.5°). Regarding the purification of oil-in-water emulsions stabilized by surfactants, the PEG/MXene@MOF membrane exhibited extremely stable high permeability (1246 ± 12 L m−2 h−1 bar−1) and excellent efficiency (>99.7 %), even during continuous separation of high-viscosity crude oil emulsions for 60 min. In addition, the PEG/MXene@MOF membrane also exhibited superior chemical durability and mechanical robustness in strong-corrosiveness and high-salty environments (72 h), ultrasonic treatments (120 min), bending experiments (100 times) and abrasion tests (20 times). Therefore, this work provided a promising strategy to construct highly permeable membrane with stable interlayer spacing and efficient fouling resistance for practical oily wastewater purification.

Chemical modification of reduced graphene oxide membranes: Enhanced desalination performance and structural properties for forward osmosis

Graphene oxide (GO) nanosheets can offer a breakthrough into the development of novel and efficient laminated forward osmosis membranes, with high hydrophilicity and outstanding desalination performance. However, fabrication of desirable GO-based nanocomposite membrane which can overcome the on-going trade-off between forward osmosis (FO) performance and chemical/mechanical stability, remains to be challenging in practical application. In this study, polyethyleneimine (PEI) was used to reduce GO (rGO) and crosslink and surface modify membrane's GO sheets for the performance enhancement. The crosslinked rGO was then deposited on a hydrophilic nylon support layer (modified by polydopamine, pDA, for structural stability) using vacuum filtration method. The resulting PEI:rGO/pDA membrane showed excellent water flux (25.5 LMH), high sodium chloride (NaCl) salt rejection (98.9%), and low reverse solute flux (0.91 gMH) in lab-scale tests. The combination of crosslinking GO with PEI and modifying the support layer with polydopamine (pDA) enhanced the membranes hydrophilicity and structural stability. The incorporation of PEI into GO resulted in compacted nanochannels, improving molecular/ions separation. Moreover, the pDA coating enhanced desalination performance and reduced internal concentration polarisation effects, further improving the membrane durability and integrity through the formation of numerous binding sites for firmly anchoring with the PEI:rGO nanocomposite structure.

Facilitating removal efficiency of electrochemical descaling system using confined crystallization membranes

As an environmentally friendly technology, electrochemical descaling has received extensive attention and research. In the traditional electrochemical descaling system, the precipitated scale is affected by several factors and only a portion of these ions can crystallize and grow into the scale layer on the cathode surface. In addition, the alkalinity ions are severely depleted by neutralization reactions, resulting in a decrease in pH value and unfavorable for the crystallization of scale. A confined crystallization membrane (CCM) for inducing scale crystallization is set to the traditional electrochemical descaling system in this paper, which weakens the negative effect of concentration polarization on mass transfer, providing an environment with high pH and low water flow interference for the crystallization of scale. Cyclic electrolysis experiments show that the addition of CCM greatly increases the amount of scale deposition, with a maximum of 60.26 g·h−1·m−2. The scale consumption per unit weight is saved by more than 50 % after adding the CCM, the values of Ryznar Stability Index (RSI) and Langelier Saturation Index (LSI) of the solution can reach the ideal range in a shorter time. The cleaning cycle of CCM is about 144 h, and the scale can be removed by pickling, thus restoring the enhanced descaling function of CCM.

Effect of ceria particle size as intermediate layer for preparation of composite Pd-membranes by electroless pore-plating onto porous stainless-steel supports

The use of H2-selective membranes for ultra-pure H2 production has been assigned as an attractive technology, particularly those based on Pd-films deposited onto porous stainless-steel (PSS) supports. The ability to incorporate thin Pd-films with enough adherence on any internal or external surfaces becomes essential to minimize their complexity and cost while improving their performance. The modification of original PSS substrates with diverse intermediate layers, especially those made of ceria, is presented as a promising alternative. In this context, the current study addresses for the first time the use of different CeO2 particle sizes to generate an intermediate layer and facilitate the subsequent generation of a thin Pd-film by electroless pore-plating (ELP-PP). The membrane containing the smallest CeO2 particle size (membrane S) demonstrated the lowest performance, which was assigned to the high compaction of the material and generation of cracks on its surface during calcination that consequently led to the deposition of a greater amount of Pd. On the other hand, the morphology of membranes M (medium CeO2 particle size) and L (large CeO2 particle size) were very similar, although the first one demonstrated a slightly smaller interparticle porosity, which led to the deposition of a more homogeneous and thinner Pd-film. Therefore, an outstanding performance in terms of H2 permeance (5.98 × 10−4 mol·m−2·s−1·Pa−0.5 at 400 °C) was obtained for this membrane. Permeation tests with binary mixtures (H2-N2, H2-CO2, or H2-CO) revealed a concentration-polarization effect in all cases, as well as a certain inhibition effect in the presence of CO. Finally, it should be highlighted the high stability of the membranes during the entire set of experiments, independently of the considered particle size. Thus, enough mechanical and thermal resistances can be assured for future applications.

A soft piezoelectric elastomer with enhanced piezoelastic response

This work aims to study, develop, and validate a soft piezo-polymer with enhanced piezo-elastic response and easy castable in a free shape through a single and easy process. The work identified a novel formulation for soft piezopolymers based on ambient temperature polymerizable silicone rubber, easily fabricable in 3D printed plastic moulds. Combining polymerizable silicone with a barium titanate (BaTiO3) ceramic powder and defining a detailed fabrication procedure of casting, curing and high voltage poling, we defined how to obtain a promising soft piezoelectric elastomer for countless sensing applications. This study includes information about the mould design used to realize, cure and polarize cylindric elastomeric specimens. This piezopolymer stands out for its flexibility, softness, easy fabrication at ambient temperature and obtainability in multiple shapes and bulky 3D geometries. Finally, we investigated different configurations of the piezopolymer formulation analysing the powder concentration and voltage polarization effects over the mechanical, piezoelectric and morphological characteristics. The specimens exhibit a high induced polarization with values up to 22.5 pC N−1, comparable with poled -phase polyvinylidene difluoride. We finally underlined limits encountered in the most extreme configurations.