Water Uptake Capability Research Articles

Hydrocarbon-based composite membranes containing sulfonated Poly(arylene thioether sulfone)-grafted 2D crown ether framework coordinated with cerium ions for PEMFC applications

We propose a novel strategy to develop sulfonated poly(arylene ether sulfone) (SPAES) composite membranes that can simultaneously improve the physicochemical stability and proton conductivity of hydrocarbon-based membranes for PEMFC applications. This strategy involves the use of a sulfonated poly(arylene thioether sulfone)-grafted 2D crown ether framework coordinated with cerium3+ ions (SATS–C2O–Ce) as a promising filler material. SATS-C2O, a highly sulfonated polymer-grafted 2D framework containing crown ether holes in its skeletal structure, was prepared via self-condensation using halogenated phloroglucinol as a multifunctional building unit to form C2O, followed by condensation using SATS to graft the sulfonated polymer onto its edge. Ce3+ ions were directly coordinated within the crown ether holes of SATS-C2O via a simple doping process using aqueous Ce solution. The SPAES composite membranes containing SATS–C2O–Ce (SPAES/SATS–C2O–Ce) exhibited exceptional dimensional stability and mechanical toughness. The remarkable chemical stability of SPAES/SATS–C2O–Ce compared to that of pristine SPAES and SPAES/Ce (containing the same amount of Ce3+ ions but without SATS-C2O) was attributed to the well-dispersed state of Ce3+ ions within the SPAES matrix. Furthermore, the enhanced proton conductivity of SPAES/SATS–C2O–Ce surpassed those of pristine SPAES, SPAES/C2O, and SPAES/Ce by the formation of additional proton-conducting channels provided by the sulfonic acid groups of SATS–C2O–Ce, along with the improved water uptake capability of SPAES.

Potential Water Collection From Air by Chloride Perovskites.

Directly capturing water from the air has become a compelling strategy to secure water resources. Yet, challenges persist with sorption-based hygroscopic materials, such as inadequate water adsorption efficiency, material degradation post-adsorption, and the need for energy input during water collection. This study introduces an alternative category of sorbent materials potentially for atmospheric water harvesting-metal chloride perovskites-that exhibit spontaneous water vapor adsorption and liquid water collection. This water uptake capability stems from the uncoordinated polar ions that form hydrogen bonds with water molecules, while the cubic lattice imparts a solid framework ensuring structural stability and inhibiting hydrolysis. The methylammonium lead chloride perovskite pellets exhibit efficient water collection performance, with a record absorption rate of 0.841 L m-2 h-1 and a total water collection of 3.675 L m-2 within a 7-h cycle. This initiative attempts to provide a new material class candidate for the potential application of passive atmospheric water harvesting.

Characterization of Decellularized Plant Leaf as an Emerging Biomaterial Platform.

Decellularized plants have emerged as promising biomaterials for cell culture and tissue engineering applications due to their distinct material characteristics. This study explores the biochemical, mechanical, and structural properties of decellularized leaves that make them useful as biomaterials for cell culture. Five monocot leaf species were decellularized via alkali treatment, resulting in the effective removal of DNA and proteins. The Van Soest method was used to quantitatively evaluate the changes in cellulose, hemicellulose, and lignin content during decellularization. Tensile tests revealed considerable variations in mechanical strength depending on the plant species, the decellularization state, and the direction of applied mechanical force. Decellularized monocot leaves exhibited a notable reduction in mechanical strength and anisotropic properties depending on the leaf orientation. Imaging revealed inherent microgrooves on the epidermis of the monocot leaves. Permeability studies, including water uptake and biomolecule transport through decellularized leaves, confirmed excellent water uptake capability but limited biomolecule transport. Lastly, the plants were enzymatically degradable using typical plant enzymes, which were minimally cytotoxic to mammalian cells. Taken together, the features of decellularized plant leaves characterized in this study suggest ways in which they can be useful in cell culture and tissue engineering applications.

Ionic nanoporous membranes from self-assembled liquid crystalline brush-like imidazolium triblock copolymers.

There is a need to generate mechanically and thermally robust ionic nanoporous membranes for separation and fuel cell applications. Herein, we report a general approach to the preparation of ionic nanoporous membranes through custom synthesis, self-assembly, and subsequent chemical manipulations of ionic brush block copolymers. We synthesized polynorbornene-based triblock copolymers containing imidazolium cations balanced by counter anions in the central block, side-chain liquid crystalline units, and sidechain polylactide end blocks. This unique platform comprises: (1) imidazolium/bis(trifluoromethanesulfonyl)imide (TFSI) as the middle block, which has an excellent ion-exchange ability, (2) cyanobiphenyl liquid crystalline end block, a sterically hindered hydrophobic segment, which is chemically stable and immune to hydroxide attack, (3) polylactide brush-like units on the other end block that is easily etched under mild alkaline conditions and (4) a polynorbornene backbone, a lightly crosslinked system that offers mechanical robustness. These membranes retain their morphology before and after backbone crosslinking as well as etching of polylactide sidechains. The ion exchange performance and dimensional stability of these membranes were investigated by water uptake capability and swelling ratio. Moreover, the length of the carbon spacer in the imidazolium/TFSI central block moiety endowed the membrane with improved ionic conductivity. The ionic nanoporous materials are unusual due to their singular thermal, mechanical, alkaline stability and ion transport properties. Applications of these materials include electrochemical actuators, solid-state ionic nanochannel biosensors, and ion-conducting membranes.

Ionically-crosslinked carboxymethyl chitosan scaffolds by additive manufacturing for antimicrobial wound dressing applications

Chitosan chemical functionalization is a powerful tool to provide novel materials for additive manufacturing strategies. The main aim of this study was the employment of computer-aided wet spinning (CAWS) for the first time to design and fabricate carboxymethyl chitosan (CMCS) scaffolds. For this purpose, the synthesis of a chitosan derivative with a high degree of O-substitution (1.07) and water soluble in a large pH range allowed the fabrication of scaffolds with a 3D interconnected porous structure. In particular, the developed scaffolds were composed of CMCS fibers with a small diameter (< 60 μm) and a hollow structure due to a fast non solvent-induced coagulation. Zn2+ ionotropic crosslinking endowed the CMCS scaffolds with stability in aqueous solutions, pH-sensitive water uptake capability, and antimicrobial activity against Escherichia coli and Staphylococcus aureus. In addition, post-printing functionalization through collagen grafting resulted in a decreased stiffness (1.6 ± 0.3 kPa) and a higher elongation at break (101 ± 9 %) of CMCS scaffolds, as well as in their improved ability to support in vitro fibroblast viability and wound healing process. The obtained results encourage therefore further investigation of the developed scaffolds as antimicrobial wound dressing hydrogels for skin regeneration.

Effect of soil conditioners based on geomimetic materials on plant growth in degraded soils: Poly(acrylic acid)/bentonite

Geomimetic materials (GEOMI) are composite materials based on polymer and clays, able to imitate structural and functional properties of soils, including their structure, cationic exchange capability (CEC), water uptake capability (WUC), pH buffering ability, immobilizing of substances, among other. Because they can be used to develop of fertilizer slow-release systems, they have been identified as a novel approach to advance toward a most sustainable agriculture. The aim of this work was to study the effect of GEOMI on the plant growth in degraded soils. For this, GEOMI-1.0 was synthesized using poly(acrylic acid) as model of humic substances and bentonite modified with trichlorovinylsilane as mineral fraction model. Materials were characterized by different techniques. GEOMI-1.0 showed a hybrid, homogeneous, and amorphous structure. In addition, it was thermally stable at below ⁓200 °C with a Tg about 49.3 °C, showed a high WUC (⁓1384 g of water per 100 g of material). Likewise, it was verified that GEOMI-1.0 can decreases the pH values and increases the CEC of degraded soils depending on the added amount of geomaterial; but also, the electric conductivity values showed no dependence on the added amount of GEOMI-1.0. By correlation analysis, an exponential dependence of CEC was observed respect to pH changes, the relative amount added of GEOMI-1.0 and the initial CEC. Finally, using Brachiaria Brizantha cv. Marandú as plant model, the increase in the biomass content of roots and leaves, and the number of germinated seeds, were observed when GEOMI-1.0 was used for restoration of in-lab degraded soils.

Parametric investigation and optimization of phase change material-based thermal energy storage integrated desiccant coated energy exchanger through physics informed neural networks oriented deep learning approach

To improve the energy exchange abilities, and to enhance indoor air quality, a desiccant-coated energy exchanger (DCEE) is a capable substitute compared to conventional energy exchangers such as fixed beds and desiccant wheels. Thus, accurately predicting the DCEE's physical characteristics is crucial for enhancing the system's performance. Therefore, in the current study, a novel data-driven modeling methodology utilizing physics-informed neural networks (PINNs) is developed to predict the exit parameters of DCEE, like the outlet temperature of cooling water, the outlet temperature of the air, and the outlet-specific humidity of the air. The performance characteristics of DCEE are evaluated using PINN by considering different input parameters. The performance parameters selected for the DCEE performance assessment are dehumidification capacity, thermal coefficient of performance, and heat recovery efficiency. The coated desiccant material chosen for the present study is silica gel. Good agreement is obtained between the PINN and experimental results for both the steady-state and transient cases, proving the PINN method's capability in solving multiple physics-based partial differential equations (PDEs) on a single domain with a maximum discrepancy of ±7.8 %. The developed model is used to obtain the optimal inlet conditions for a given operating condition. Adsorption kinetics of the coated desiccant silica gel revealed that the maximum water uptake capability for the given operating range is 0.345 g.g−1. A case study has been carried out by integrating an industrial waste heat-driven DCEE with a thermal energy storage module (TES) to analyze the energy storage ability during regeneration. A parametric study has been conducted to examine the transfer characteristics of the TES module. Further, the effectiveness of the TES module for five different phase change materials (PCMs) has been assessed. Finally, the seasonal energy efficacy ratio (SEER) of five different PCMs was investigated for 365 days to evaluate year-round performance. The effectiveness of thermal energy storage is maximum for Palmitic acid and minimum for Climsel C48, with corresponding values of 0.73 and 0.37. SEER is the largest for Palmitic acid and lowest for Climsel C48. The values of SEER for Palmitic acid during the summer and winter seasons are 5.489 and 3.31, whereas the values of SEER for Climsel C48 during the summer and winter seasons are 5 and 2.89, respectively.

New Advances in Graded PEMFC Catalyst Layers

Ohmic and mass transport overpotentials remain investigation and optimization areas for Proton Exchange Membrane Fuel Cell (PEMFC) applications. One potential optimization approach involves the preferential distribution of the chemical substituents spatially in the catalyst layer. This would ultimately result in graded catalyst layers (GCLs). The spatial grading directions can thereby be in the in plane and/or through plane direction(s). Chemical constituents often graded in both directions include the binder and the catalyst[1, 2]. The ionomer, an essential constituent for PEMFC applications has also been a key focus area for many research institutes and groups. Novel optimization approaches include finding new ionomers with low equivalent weights (EWs).Typically, in a PEMFC, the highest proton conduction rate is at the membrane interface and decreases towards the GDL[3, 4]. Hence, previous studies with gradients containing high ionomer contents close to the membrane and lower ones at the GDL interface resulted in improved performances. The higher ionomer content at the membrane interface resulted in better protonic conductions, and the bigger void spaces in the GDL interface resulted in improved mass transport properties[1, 5]. Though precise electrochemical analysis is lacking, it is commonly agreed that the graded layers have lower mass transport and ohmic resistances. However, the studies encountered in the literature are almost exclusively based on high EW ionomers, such as Nafion. In contrast, low EW ionomers, which have higher protonic conductivity and water uptake capabilities have not yet been a focus of researchers. Additionally, the few reports encountered in the literature focus solely on GCLs while often disregarding other contributing effects to the overall cell voltage such as the equivalent weight.Low EW ionomers offer a wider operation range for PEMFCs in terms of relative humidities. By combining the low EW ionomers with graded catalyst layers, the operation range becomes even more flexible, and the limits are further stretched. In this study, we push the operating range limits of low EW graded catalyst layers and compare them to non-graded ones. We investigate different manufacturing techniques and use suitable scalable coating methods for the manufacturing of the electrodes. Afterwards, suitable in situ and ex situ analysis techniques are used in detail to trace down the improvements for the gradients. Among the key findings, we notice that potential improvements for low EW ionomer graded catalyst layers become apparent at considerable low relative humidities. The improvements are visible in the kinetic, ohmic, and mass transport regions.

Title High Solar-Thermal Conversion Aerogel for Efficient Atmospheric Water Harvesting.

The shortage of freshwater is a global problem, however, the gel that can be used for atmospheric water harvesting (AWH) in recent years studying, suffer from salt leakage, agglomeration, and slow water evaporation efficiency. Herein, a solar-driven atmospheric water harvesting (SAWH) aerogel is prepared by UV polymerization and freeze-drying technique, using poly(N-isopropylacrylamide) (PNIPAm), hydroxypropyl cellulose (HPC), ethanolamine-decorate LiCl (E-LiCl) and polyaniline (PANI) as raw materials. The PNIPAm and HPC formed aerogel networks makes the E-LiCl stably and efficiently loaded, improving the water adsorption-desorption kinetics, and PANI achieves rapid water vapor evaporation. The aerogel has low density ≈0.12-0.15gcm-3, but can sustain a weight of 1000 times of its own weight. The synergist of elements and structure gives the aerogel has 0.46-2.95gg-1 water uptake capability at 30-90% relative humidity, and evaporation rate reaches 1.98kgm-2h-1 under 1 sun illumination. In outdoor experiments, 88% of the water is harvesting under natural light irradiation, and an average water harvesting rate of 0.80gwater gsorbent -1day-1. Therefore, the aerogel can be used in arid and semi-arid areas to collect water for plants and animals.

Effects of polycaprolactone viscosity on morphology, mechanical properties, water uptake, and cellular viability in poly(3‐hydroxybutyrate)/polycaprolactone blends for tissue engineering

AbstractIn this study, two polycaprolactones (PCLs) with different molar masses were evaluated regarding their influence on the melt processability, morphology viscoelastic and mechanical properties, water uptake, and fibroblast and pre‐osteoblast viability of poly(3‐hydroxybutyrate)/polycaprolactone (PHB/PCL) blends. PHB/PCL blends were prepared in a mixing chamber following 90/10 and 70/30 ratios and later compression molded. The torque rheometry results show that the blends' processability is influenced by the ratio and molar mass of the PCL used in its obtaining, those being more strongly affected by the PCL with lower molar mass. The results indicate that the polymeric blend was immiscible in any proportion and molar mass of PCL used. The blends showed a sea‐island morphology in which the diameter of the dispersed phase depended on the composition. In general, even though the molar mass of PCL differed, the blends showed similar behaviors. However, a great difference was observed in the fracture mechanism for the blend with PCL of lower molar mass, which did not present the ability to fibrillate before rupture, due to its low mechanical resistance. The blends showed greater water uptake capabilities when compared to the pure polymers due to the diffusion of water through the gaps in between the phases. The blends showed high cell viability when tested in fibroblast cells of the L929 lineage and pre‐osteoblast cells of the MCT3‐E1 lineage, indicating that these materials are promising for application in bone tissue engineering.

Microwave Treatments and Their Effects on Selected Properties of Portuguese Pinus pinaster Aiton. and Eucalyptus globulus Labill. Wood

The most widespread wood species in the Portuguese forest and the most widely utilized are maritime pine (Pinus pinaster) and eucalyptus (Eucalyptus globulus Labill). In the case of eucalyptus, except for the pulping sector, it might have limited usage due to drying issues and low permeability. Microwave (MW) treatment is a technology that has been used to improve wood species’ permeability. Therefore, the present paper aimed to evaluate the MW treatment of both Portuguese wood species and to investigate the effects of different MW treatments on wood’s density, water uptake capability, modulus of rupture (MOR), and modulus of elasticity (MOE). Using small clear wood specimens, two MW powers were used, 700 and 1200 W, and the samples were submitted to successive MW cycles of 2 min till they reached the required dryness. The results showed that each wood species had a different behavior during the MW drying in terms of drying rate, supply, and consumption of energy. In general, with the increase in MW power, the densities of both species decreased and the water uptake increased, as a possible indicator that a certain level of microstructural damage might have occurred. Regarding the mechanical properties of MW-treated maritime pine and eucalyptus wood specimens, under the harshest conditions (MW power of 1200 W), MOR and MOE were reduced compared with the wood sample without MW treatment.

Effects of size on water vapour absorption and regeneration in lithium chloride nanocrystals

Ionic salts have received tremendous attention for applications such as electrolytes, solar energy, and desiccants. In particular, the high surface area of desiccant materials enhanced moisture absorption capacity, making it suitable for humidity control in various environments. However, lithium chloride (LiCl) salt properties remain largely unexplored in nanocrystalline form (at a high surface to volume ratio) due to difficulty preparing and stabilising nanoparticles, despite the high tide of expectations for energy applications. In the present investigation, for the first time, nanocrystalline LiCl was prepared by a top-down approach - successive cryomilling under an inert atmosphere. Systematic investigation shows nanocrystalline LiCl undergoes rapid dissolution in the presence of moisture. The experimental results were further corroborated with Molecular Dynamics (MD) simulations using LAMMPS. The combined use of milling at room temperature (RT) and cryomilling resulted in a crystallite size of approximately 60 nm. The nanocrystalline LiCl exhibited a water uptake capability eight times faster than that of the bulk LiCl crystal. The simulations revealed that smaller crystals are more reactive because they (i) readily deform in water and (ii) have a larger fraction of atoms with lower stability. The reasons behind the high reactivity of nanocrystalline LiCl, which has not been reported in the literature, have been discussed in detail.

Probing proton diffusion as a guide to environmental stability in powder-engineered FAPbI3 and CsFAPbI3 perovskites

Formamidinium lead iodide-based solar cells show promising device reliability. The grain imperfection can be further suppressed by developing powder methodology. The water uptake capability is critical for the stability of α-formamidinium lead triiodide (FAPbI3) thin films, and elucidating the migration of hydrogen species is challenging using routine techniques such as imaging or mass spectroscopy. Here, we decipher the proton diffusion to quantify indirect monitoring of H migration by following the N-D vibration using transmission infrared spectroscopy. The technique allows a direct assessment of the perovskite degradation associated with moisture. The inclusion of Cs in FAPbI3, reveals significant differences in proton diffusion rates, attesting to its impact. CsFAPbI3's ability to block the active layer access by water molecules is five times higher than α-FAPbI3, which is significantly higher than methylammonium lead triiodide (MAPbI3). Our protocol directly probes the local environment of the material to identify its intrinsic degradation mechanisms and stability, a key requirement for optoelectronic applications.

Improved anti-corrosion and mechanical aspects of reinforced cementitious composites with bio-inspired strategies

The device of self-healing cementitious composites is a most anticipated approach for repair of unavoidable cracks through biological intrusions. The bio-inspired self-healing composites systematically heal the cracks and control the penetration of corrosive ions towards the embedded steel. However, the effect of bacterial additions on the electrochemical performance of embedded steel holds several questions and needed to be explored further. Therefore, this research was carried out to assess the effect of a calcifying bacterial strain “Bacillus safensis” and its carrier media, biochar, on mechanical and transport properties along with the corrosion performance of embedded steel in cementitious composites. The boosted strain energy storing potential with 25.5% and 38.18% enhanced flexural and compressive strength than control sample, respectively was observed. Additionally, about 89% gain in compressive strength was observed after 28 days of cracking at 85% of ultimate compressive strength. Moreover, a significant increase in relative healing degree was seen during ultrasonic pulse velocity measurements of uncracked and cracked samples. Furthermore, the healing precipitate was recognized as calcite through scanning electron microscopy and Fourier transform infrared spectroscopy. The lower sorptivity trends also indicated the denser microstructure with minimum water uptake capability and porosity which lead towards minimum corrosion damage in the embedded steel. Besides, the corrosion inhibition efficiency was noted as 95.18% compared to the control sample. Thus, the proposed combination of biotic and abiotic materials would be a good solution for recycling waste and enhancing mechanical and durability prospects of reinforced cementitious composites.

Complex Dose Rate Calculations in Luminescence Dating of Lacustrine and Palustrine Sediments from Niederweningen, Northern Switzerland

This study focusses on dose rate determination in complex settings in two drill cores from the site of Niederweningen, northern Switzerland. A crosscheck with a certified standard material and neutron activation analyses (NAA) reveals an overall good performance of high-resolution gamma spectrometry (HR-GS) when determining dose rate-relevant elements. A second focus is on average water content during burial, by comparing measured sediment moisture with water uptake capability. Furthermore, layer models are used to investigate the impact of inhomogeneous stratification on dose rate. Finally, different scenarios to correct for radioactive disequilibrium in the uranium decay chain are investigated. While most of the applied corrections appear to have only a minor to moderate effect on age calculation, the results for one core are contradictory. Possibly, some of the applied correction scenarios are not reflecting the complex natural setting sufficiently, in particular average sediment moisture during burial and the timing of radioactive disequilibrium might be incorrectly estimated. While deposition in one core can be quite securely attributed to the period 100–70 ka, assigning the sediment sequence in the other core to the time between ca. 130 ka and 90 ka remains to some extent insecure.

Carbonised Human Hair Incorporated in Agar/KGM Bioscaffold for Tissue Engineering Application: Fabrication and Characterisation.

Carbon derived from biomass waste usage is rising in various fields of application due to its availability, cost-effectiveness, and sustainability, but it remains limited in tissue engineering applications. Carbon derived from human hair waste was selected to fabricate a carbon-based bioscaffold (CHAK) due to its ease of collection and inexpensive synthesis procedure. The CHAK was fabricated via gelation, rapid freezing, and ethanol immersion and characterised based on their morphology, porosity, Fourier transforms infrared (FTIR), tensile strength, swelling ability, degradability, electrical conductivity, and biocompatibility using Wharton’s jelly-derived mesenchymal stem cells (WJMSCs). The addition of carbon reduced the porosity of the bioscaffold. Via FTIR analysis, the combination of carbon, agar, and KGM was compatible. Among the CHAK, the 3HC bioscaffold displayed the highest tensile strength (62.35 ± 29.12 kPa). The CHAK also showed excellent swelling and water uptake capability. All bioscaffolds demonstrated a slow degradability rate (<50%) after 28 days of incubation, while the electrical conductivity analysis showed that the 3AHC bioscaffold had the highest conductivity compared to other CHAK bioscaffolds. Our findings also showed that the CHAK bioscaffolds were biocompatible with WJMSCs. These findings showed that the CHAK bioscaffolds have potential as bioscaffolds for tissue engineering applications.

A durable MOF-303-coated stainless steel mesh with robust anti-oil-fouling performance for multifunctional oil/water separation

Durable anti-fouling membranes for the effective and simultaneous removal of insoluble oil droplets and organic dyes from wastewater need to be developed urgently. Metal–organic frameworks (MOFs) are emergent porous organic–inorganic hybrid materials, that have been attracting increasing attention because of wide applications, such as liquid separation, dye adsorption, and catalysis. However, the preparation of a well-intergrown MOF membrane remains challenging, because of poor water stability and low affinity between MOF grains and substrates. Herein, we report the first preparation of a continuous, water-stable MOF-coated mesh with an ordered porous structure by using a simple hydrothermal method to realize array growth of MOF-303 crystals on a layered double-hydroxide modified mesh surface. As the MOF-303 has a high water uptake capability, the prepared MOF-303 @SSM with sufficient surface hydration exhibited superhydrophilicity-underwater superoleophobicity and excellent antifouling performance. This membrane was used for gravity-driven separation of oil/water mixtures at high flux (> 12308 L m−2 h−1) and efficiency (> 99.35%). This membrane simultaneously and efficiently removed an oil-in-water (O/W) emulsion and water-soluble dyes, and exhibited outstanding reusability. More importantly, MOF-303 @SSM is promising for practical applications because of outstanding physical and chemical stability, as well as high thermal stability, under harsh environmental conditions. Therefore, this study provides a promising strategy to develop a functional MOF membrane for purifying hazardous wastewater.

Metal Fluoride Particles to Enhance Durability of Composite Membranes at MT-PEM Fuel Cell Operating Temperatures

Fuel cells, as a local, emission-free and versatile system, promise to overcome our dependence on fossil fuels.[1] Polymer electrolyte membrane fuel cells (PEMFCs) are considered one of the most promising technologies among the various kinds of existing fuel cells and offer an attractive alternative for automotive and stationary energy applications. Especially PEMFCs operating at an increased temperature range (MT-PEM) offer an enhanced performance. Operating temperatures between 100 – 130 °C lead to better reaction kinetics, higher tolerance to fuel impurities and to an improved heat, water and power management of the system.[2] However, some issues regarding durability and performance, such as low proton conductivity of PFSA-based membranes, higher membrane degradation and lower long-term stability at increased temperatures, are still unsolved.[3] In previous works we have shown that various metal fluorides implemented into perfluorosulfonic acid (PFSA)-membranes have a positive impact on performance and mechanical stability at operating temperatures above 100 °C.[4] In this work, we describe the modification of lithium fluoride nanoparticles, their influence on membrane durability in single cell tests at enhanced PEMFC operating temperatures and the morphology of the composite membranes, at different temperatures and degree of hydration, by in-situ small-angle X-ray scattering (SAXS). The lithium fluoride modified membrane showed increased cell performance under both standard and harsher cell conditions as well as in various long-term stability tests, such as accelerated OCV tests, load cycles and on-off cycles.One explanation for the performance boost, in addition to the increased mechanical stability of the membrane, would be an increased water uptake and storage capability, especially at low humidity levels during cell operation. We assume that the nanoparticles adsorb water molecules by hydrogen bond formation, which leads to an enhanced proton conductivity even at high temperatures. To confirm this assumption, we applied in-situ SAXS to analyze the water uptake of the modified membranes at various relative humidity and temperatures to understand the structural changes. In addition, we hope to connect different nanoparticle shapes to their influence on water uptake and retention.[1] I. Staffell, D. Scamman, A. Velazquez Abad, P. Balcombe, P. E. Dodds, P. Ekins, N. Shah, K. R. Ward, Energy Environ. Sci. 2019, 12, 463–491.[2] R. E. Rosli, A. B. Sulong, W. R. W. Daud, M. A. Zulkifley, T. Husaini, M. I. Rosli, E. H. Majlan, M. A. Haque, Int. J. Hydrogen Energy 2017, 42, 9293–9314.[3] L. Mazzapioda, S. Panero, M. A. Navarra, Polymers 2019, 11, 914.[4] A. Moszczynska, H. Wolf, M. A. Willert-Porada, Patent WO/2009/014930, 2009.

Alkali-Grafting Proton Exchange Membranes Based on Co-Grafting of α-Methylstyrene and Acrylonitrile into PVDF.

A novel alkali-induced grafting polymerization was designed to synthesize a PFGPA proton exchange membrane based on the co-grafting of α-methyl styrene (AMS) and acrylonitrile (AN) into the poly(vinylidenedifluoride) (PVDF) membrane. Three kinds of alkali treatments were used: by immersing the PVDF membranes into a 1 M NaOH solution and mixing the PVDF powders with 16% or 20% Na4SiO4. Then, AMS with AN could be co-grafted into the PVDF backbones in two grafting solvents, THF or IPA/water. Finally, the grafted membranes were sulfonated to provide the PFGPA membranes. In the experiments, the Na4SiO4 treatments showed a greater grafting degree than the NaOH treatment. The grafting degree increased with the increasing amount of Na4SiO4. The grafting solvent also influenced the grafting degree. A 40–50 percent grafting degree was obtained in either the THF or IPA/water solvent after the Na4SiO4 treatment and the THF resulted in a greater grafting degree. FTIR and XPS testified that the PFGPA membranes had been prepared and a partial hydrolysis of the cyano group from AN occurred. The PFGPA membranes with the grafting degree of about 40–50 percent showed a better dimensional stability in methanol, greater water uptake capabilities, and lower ion exchange capacities and conductivities than the Nafion 117 membranes. The PFGPA membrane with the 16% Na4SiO4 treatment and THF as the grafting solvent exhibited a better chemical stability. The obtained experimental results will provide a guide for the synthesis of alkali-grafted PFGPA membranes in practical use.

Effect of pore modulating additives-sepiolite and colloidal nano silica-on physical, mechanical and durability properties of lime-based renders

In hot-humid climates, porous external surfaces of the buildings with high water sorption capabilities could contribute to the surface temperatures reduction through the release of latent heat by evaporative cooling. On the other hand, compact and low permeable finishing materials could have mechanical and durability benefits respect to the underlying supports, for example reducing the permeability to degrading agents. In this paper, the properties of lime base coat renders with pore modulating additives (sepiolite and colloidal nano silica) have been surveyed to evaluate their effectiveness in water absorption, thermal performance, and the fulfilment of mechanical requirements for the application on the external side of the walls. A traditional lime–sand formulation was taken as reference. After preliminary tests on workability and shrinkage, the optimal mix designs were selected and the samples were subjected to several mechanical and thermo-hygrometric tests, before and after accelerated aging. The results allowed demonstrating that the use of sepiolite in substitution of sand, enhances the render ductility, thermal resistance and water uptake but worsens its mechanical stability, increasing the shrinkage effects and slightly reducing the ultimate strength values. The addition of colloidal nano silica, either to lime–sepiolite or to lime–sand renders, fails to produce any improvement in their either physical or mechanical behavior. Mixed formulations (lime–sand with sepiolite and nano silica) behave as simple lime–sand solutions, showing optimal compressive and flexural strength but reduced water uptake capabilities. This demonstrates that the presence of sand prevails in the performance of the render, and that the adoption of other additives doesn’t worth the cost for the benefit presented.