Poly(ε-caprolactone) (PCL) is a bioresorbable synthetic polyester with numerous biomedical applications. PCL membranes show great potential in guided tissue regeneration because they are ...biocompatible, occlusive and space maintaining, but lack osteoconductivity. Therefore, two different types of mesoporous bioactive glasses (SiO
-CaO-P
O
and SiO
-SrO-P
O
) were synthesized and incorporated in PCL thin membranes by spin coating. To enhance the osteogenic effect of resulting membranes, the bioglasses were loaded with the bisphosphonate drug ibandronate prior to their incorporation in the polymeric matrix. The effect of the composition of the bioglasses as well as the presence of absorbed ibandronate on the physicochemical, cell attachment and differentiation properties of the PCL membranes was evaluated. Both fillers led to a decrease of the crystallinity of PCL, along with an increase in its hydrophilicity and a noticeable increase in its bioactivity. Bioactivity was further increased in the presence of a Sr substituted bioglass loaded with ibandronate. The membranes exhibited excellent biocompatibility upon estimation of their cytotoxicity on Wharton's Jelly Mesenchymal Stromal Cells (WJ-SCs), while they presented higher osteogenic potential in comparison with neat PCL after WJ-SCs induced differentiation towards bone cells, which was enhanced by a possible synergistic effect of Sr and ibandronate.
A novel process-based methodology is proposed for the stochastic reconstruction and accurate characterisation of Carbon fiber-based matrices, which are commonly used as Gas Diffusion Layers in Proton ...Exchange Membrane Fuel Cells. The modeling approach is efficiently complementing standard methods used for the description of the anisotropic deposition of carbon fibers, with a rigorous model simulating the spatial distribution of the graphitized resin that is typically used to enhance the structural properties and thermal/electrical conductivities of the composite Gas Diffusion Layer materials. The model uses as input typical pore and continuum scale properties (average porosity, fiber diameter, resin content and anisotropy) of such composites, which are obtained from X-ray computed microtomography measurements on commercially available carbon papers. This information is then used for the digital reconstruction of realistic composite fibrous matrices. By solving the corresponding conservation equations at the microscale in the obtained digital domains, their effective transport properties, such as Darcy permeabilities, effective diffusivities, thermal/electrical conductivities and void tortuosity, are determined focusing primarily on the effects of medium anisotropy and resin content. The calculated properties are matching very well with those of Toray carbon papers for reasonable values of the model parameters that control the anisotropy of the fibrous skeleton and the materials resin content.
•We propose a novel algorithm for resin deposition in GDLs.•We obtain microscale information using X-ray micro-CT measurements.•We study the transport properties of realistic reconstructed GDLs.•We focus primarily on the effects of resin content and medium anisotropy.•Our numerical calculations compare very good with experimental data.
The efficient storage of energy combined with a minimum carbon footprint is still considered one of the major challenges towards the transition to a progressive, sustainable and environmental ...friendly society on a global scale. The energy storage in pure chemical form using gas carriers with high heating values, including H2 and CH4, as well as via electrochemical means using state-of-the-art devices, such as batteries or supercapacitors, are two of the most attractive alternatives for the combustion of finite, carbon-rich and environmentally harmful fossil fuels, such as diesel and gasoline. A few-step, reproducible and scalable method is presented in this study for the preparation of an ultra-microporous (average pore size around 0.6nm) activated carbon cloth (ACC) with large specific area (> 1200m2/g) and pore volume (~ 0.5cm3/g) upon combining chemical impregnation, carbonization and CO2 activation of a low-cost cellulose-based polymeric fabric. The ACC material shows a versatile character towards three different applications, including H2 storage via cryo-adsorption, separation of energy-dense CO2/CH4 mixtures via selective adsorption and electrochemical energy storage using supercapacitor technology. Fully reversible H2 uptake capacities in excess of 3.1wt% at 77K and ~ 72bar along with a significant heat of adsorption value of up to 8.4kJ/mol for low surface coverage have been found. Upon incorporation of low-pressure sorption data in the ideal adsorbed solution theory model, the ACC is predicted to selectively adsorb about 4.5 times more CO2 than CH4 in ambient conditions and thus represents an appealing adsorbent for the purification of such gaseous mixtures. Finally, an electric double-layer capacitor device was assembled and tested for its electrochemical performance, constructed of binder-free and flexible ACC electrodes and aqueous CsCl electrolyte. The full-cell exhibits a gravimetric capacitance of ~ 121F/g for a specific current of 0.02A/g, which relative to the ACC's specific area, is superior to commercially available activated carbons. A capacitance retention of more than 97% was observed after 10,000 charging/discharging cycles, thus indicating the ACC's suitability for demanding and high-performance energy storage on a commercial scale. The enhanced performance in all tested applications seems to be attributed to the mean ultra-micropore size of the ACC material instead of the available specific area and/or pore volume.
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•CO2 activation of carbonized viscose rayon leads to ultra-microporous carbon cloth.•Strong interaction with H2 and reversible uptake of 3.12wt% at 77K and 72bar.•Predicted CO2/CH4 gas selectivity factor of 4.5 at 298K and 1bar using IAST model.•Excellent specific area normalized supercapacitor performance using CsCl electrolyte.
In the framework of the European Cooperation in Science and Technology (COST) Action MP1103 Nanostructured Materials for Solid-State Hydrogen Storage were synthesized, characterized and modeled. This ...Action dealt with the state of the art of energy storage and set up a competitive and coordinated network capable to define new and unexplored ways for Solid State Hydrogen Storage by innovative and interdisciplinary research within the European Research Area. An important number of new compounds have been synthesized: metal hydrides, complex hydrides, metal halide ammines and amidoboranes. Tuning the structure from bulk to thin film, nanoparticles and nanoconfined composites improved the hydrogen sorption properties and opened the perspective to new technological applications. Direct imaging of the hydrogenation reactions and in situ measurements under operando conditions have been carried out in these studies. Computational screening methods allowed the prediction of suitable compounds for hydrogen storage and the modeling of the hydrogen sorption reactions on mono-, bi-, and three-dimensional systems. This manuscript presents a review of the main achievements of this Action.
•Review on nanostructured materials for solid-state hydrogen storage of COST Action MP1103.•Synthesis of novel materials and systems for H2 storage.•Characterization methods for novel materials and systems for H2 storage.•Computational methods for novel materials and systems for H2 storage.
Two different types of ordered mesoporous nanoparticles, namely MCM-41 and MCM-48, with similar pore sizes but different pore connectivity, were loaded with aprepitant via a passive diffusion method. ...The percentage of the loaded active agent, along with the encapsulation efficiency, was evaluated using High-performance Liquid Chromatography (HPLC) analysis complemented by Thermogravimetric Analysis (TGA). The determination of the pore properties of the mesoporous particles before and after the drug loading revealed the presence of confined aprepitant in the pore structure of the particles, while Powder X-ray Diffractometry(pXRD), Differential Scanning Calorimetry (DSC), and FTIR experiments indicated that the drug is in an amorphous state. The release profiles of the drug from the two different mesoporous materials were studied in various release media and revealed an aprepitant release up to 45% when sink conditions are applied. The cytocompatibility of the silica nanoparticles was assessed in Caco-2 cell monolayers, in the presence and absence of the active agent, suggesting that they can be used as carriers of aprepitant without presenting any toxicity in vitro.
Poly(ε-caprolactone) (PCL) is a bioresorbable synthetic polyester widely studied as a biomaterial for tissue engineering and controlled release applications, but its low bioactivity and weak ...mechanical performance limits its applications. In this work, nanosized bioglasses with two different compositions (SiO₂⁻CaO and SiO₂⁻CaO⁻P₂O₅) were synthesized with a hydrothermal method, and each one was used as filler in the preparation of PCL nanocomposites via the in situ ring opening polymerization of ε-caprolactone. The effect of the addition of 0.5, 1 and 2.5 wt % of the nanofillers on the molecular weight, structural, mechanical and thermal properties of the polymer nanocomposites, as well as on their enzymatic hydrolysis rate, bioactivity and biocompatibility was systematically investigated. All nanocomposites exhibited higher molecular weight values in comparison with neat PCL, and mechanical properties were enhanced for the 0.5 and 1 wt % filler content, which was attributed to extensive interactions between the filler and the matrix, proving the superiority of in situ polymerization over solution mixing and melt compounding. Both bioglasses accelerated the enzymatic degradation of PCL and induced bioactivity, since apatite was formed on the surface of the nanocomposites after soaking in simulated body fluid. Finally, all samples were biocompatible as Wharton jelly-derived mesenchymal stem cells (WJ-MSCs) attached and proliferated on their surfaces.
We study the thermal coupling potential between a Sodium Alanate tank and a High-Temperature PEM fuel cell using a heat transfer fluid to redirect a fraction of the thermal power produced during ...normal fuel cell operation towards the walls of the metal hydride tank in order to maintain hydrogen desorption. The remaining thermal power is then rejected to the environment by introducing an appropriately adjusted excess of air directly to the fuel cell cathode. Assuming a typical tubular geometry for both the metal hydride tank and the fuel cell, we propose a generic physical model that accounts for heat transfer in all the components of the integrated system (fuel cell, metal hydride tank and heating jacket), as well as H2 desorption kinetics and flow in the tank. Based on this model we study the dynamics of the coupled storage/usage system in terms of H2 pressure in the tank and temperatures in the tank and the fuel cell. Focus is primarily placed on the parameters that lead to steady-state operating conditions (i.e. the flow rate of air towards the fuel cell and the velocity of the heat transfer fluid in the heating jacket), with respect to the electrical power of the fuel cell.
•We study the thermal coupling potential of HT-PEMFCs with sodium alanate tanks.•We propose a physical model that accounts for heat transfer and desorption kinetics.•We study the dynamics of the integrated system assuming a simplified design.•Modeling results compare quite favorably with experimental data from the literature.•Design optimization for enhanced heat transfer can be performed with the model.
Both LiBH4 and NaBH4 are well known for having high hydrogen contents, but also high decomposition temperatures and slow hydrogen absorption–desorption kinetics, preventing their use for hydrogen ...storage applications. The low melting temperature (219 °C) of their eutectic mixture 0.71 LiBH4–0.29 NaBH4 allowed the synthesis of a new composite material through the melt infiltration of the hydrides into the ~5 nm diameter pores of a CMK-3 type carbon. A composite of 0.71 LiBH4–0.29 NaBH4 and non-porous graphitic carbon discs was also prepared by similar methods for comparison. Both composites showed improved kinetics and a partial reversibility of the dehydrogenation/rehydrogenation reactions. However, the best results were observed for the CMK-3 nanoconfined hydrides; a consistent uptake of about 3.5 wt.% H2 was recorded after five hydrogenation/dehydrogenation cycles for an otherwise non-reversible system. The improved hydrogen release kinetics are attributed to carbon–hydride surface interactions rather than nanoconfinement, while enhanced heat transfer due to the carbon support may also play a role. Likewise, the carbon–hydride contact proved beneficial in terms of reversibility, without, however, ruling out the potential positive effect of pore confinement.
Poly(ethylene 2,5-furandicarboxylate) (PEF)-based nanocomposites containing Ce-bioglass, ZnO, and ZrO
nanoparticles were synthesized via in situ polymerization, targeting food packaging applications. ...The nanocomposites were thoroughly characterized, combining a range of techniques. The successful polymerization was confirmed using attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, and the molecular weight values were determined indirectly by applying intrinsic viscosity measurements. The nanocomposites' structure was investigated by depth profiling using time-of-flight secondary ion mass spectrometry (ToF-SIMS), while color measurements showed a low-to-moderate increase in the color concentration of all the nanocomposites compared to neat PEF. The thermal properties and crystallinity behavior of the synthesized materials were also examined. The neat PEF and PEF-based nanocomposites show a crystalline fraction of 0-5%, and annealed samples of both PEF and PEF-based nanocomposites exhibit a crystallinity above 20%. Furthermore, scanning electron microscopy (SEM) micrographs revealed that active agent nanoparticles are well dispersed in the PEF matrix. Contact angle measurements showed that incorporating nanoparticles into the PEF matrix significantly reduces the wetting angle due to increased roughness and introduction of the polar -OH groups. Antimicrobial studies indicated a significant increase in inhibition of bacterial strains of about 9-22% for Gram-positive bacterial strains and 5-16% for Gram-negative bacterial strains in PEF nanocomposite films, respectively. Finally, nanoindentation tests showed that the ZnO-based nanocomposite exhibits improved hardness and elastic modulus values compared to neat PEF.
Structural and transport properties of lipid bilayers consisting of pure ceramides are investigated through molecular dynamics simulations. Two different initial configurations are used: one where ...the lipids already form a pre-constructed bilayer and one obtained from the self-assemblage of lipids randomly distributed in an aqueous phase. The latter is created using the MARTINI coarse-grained forcefield followed by back-mapping to atomistic description using the CHARMM forcefield. It is found that the pre-constructed and the self-assembled bilayers have in general comparable structural properties. Nevertheless they exhibit certain differences with respect to the packing and conformation of the aliphatic chains, leading to a different energy barrier that a drug molecule such as ibuprofen must overcome in order to move along the bilayer normal. These results show that the choice of the initial lipids setup for molecular dynamics simulations of a lipid bilayer may have a significant impact on the simulation outcome and thus, the respective calculated structure and transport properties.
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