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In this study, interfacial segregation in Cl−-doped ZnO (0.0, 1.0, 3.0, 4.0, and 6.0 mol%) was explored as a strategy to compensate the space charge layer to decrease the electric potential barrier height at the grain boundaries and increase the overall electrical conductivity of the system. The focus of this work was to evaluate the dopant segregation and provide the first insights into the influence of interfacial segregation on the electrical properties. By using a systematic lixiviation method, we demonstrated that in addition to the bulk solubility, the Cl− anions segregated at both the surface and grain boundaries. Impedance spectroscopy measurements showed a four orders of magnitude reduction in the total electrical resistivity in the Cl−-doped ZnO samples compared to that of undoped ZnO. The calculated value of the electric potential barrier height decreased, as well as the activation energy for conduction, which decreased from 853 meV for undoped ZnO to 168 meV for 1.2 mol% Cl−-doped ZnO.

Simple and cost-effective technologies to produce solid oxide fuel cells layers require control of thickness, homogeneity, and reproducibility. The manufacturing of a SOFC involves significant ceramic processing challenges to obtain layers with controlled microstructure. Currently, possibly the most common technique for large-scale production of SOFCs is the tape casting. In our study, a co-tape casting process was used to avoid delamination and ensure good adhesion between layers. The process consists of casting a thick anode tape of Ni/YSZ (60/40vol%) on top of a thin electrolyte tape of yttria-stabilized zirconia (YSZ). The slurries of both components were prepared using commercial ceramic powders, organic additives, and solvent. The starting materials were processed in a ball mill, to attain the appropriate homogeneity and viscosity for tape casting. A double doctor blade was used to control the thickness. Thermogravimetric and dilatometric analysis were performed to find the optimized heat treatment to remove the organics and densify the electrolyte while keeping a porous anode. The half-cells were then calcined and sintered at 1450°C/1h, with low heating and cooling rates to prevent cracks due to the different thermal expansion of the layers. The LSM cathode was then deposited by spin-coating and attached to the half-cell at 1100°C/1h. To verify the adhesion, thickness, and porosity of the layers, the sample was analyzed by scanning electron microscope. The electrochemical performance was evaluated by impedance spectroscopy and single cell tests under hydrogen and synthetic air. In this study we demonstrate a facile route to SOFC fabrication by co-casting and co-sintering, with relatively mild sintering conditions, with a good control of layer thickness, porosity and adhesion. Figure 1

A2B2O7 compounds have unique properties, such as good thermal stability, oxygen mobility, ionic conductivity, etc. Such compounds with tailored compositions exhibit good catalytic properties in a variety of high-temperature reactions, such as reform and oxidative coupling of methane (OCM). An effective catalyst for OCM must have electrophilic oxygen mobility and alkalinity on its surface. A typical A2B2O7 compound that contains a trivalent rare earth metal at site A, such as La, can provide the necessary surface alkalinity for a good OCM catalyst. Previous studies show that La2Ce2O7 (LCO) catalysts perform well in OCM due to the selective mobile oxygen sites, suitable alkaline sites, and high thermal stability. Doping LCO with Ca increases the alkalinity, which can considerably increase selectivity for ethylene in the OCM reaction. We have studied calcium-doped lanthanum ceria materials as a catalytic layer in solid oxide fuel cells reactors for methane conversion to ethylene. We have explored the combustion synthesis to obtain homogeneous La2-xCaxCe2O7 powders with x = 0, 0.25, and 0.50 (LCO, LCa25, and LCa50, respectively). X-ray diffraction (XRD) showed that the calcium addition in LCO formed a single-phase solid solution. The crystalline structure of the synthesized materials is the disordered fluorite-type, as indicated by both XRD and Raman analysis. Raman spectroscopy data evidenced the presence of surface oxygen vacancies on all materials, which may benefit the OCM reaction. SEM images of as-prepared powders obtained evidenced a similar microstructure composed of porous sponge-like agglomerated particles with irregular shape, expected from the combustion synthesis (Fig. 1). Ca-doping changed the sintering behavior by reducing the onset of shrinkage during the sintering process. Impedance spectroscopy data showed increased ionic conductivity with increasing Ca-doping. Such an increase is more evident at high measuring temperature (800 oC) and indicates enhanced oxygen mobility that are expected to contribute to OCM reaction. Figure 1: Scanning electron microscope micrographs of La2-xCaxCe2O7 (x = 0, 0.25, and 0.50) as-prepared powders obtained by combustion method. Figure 1

The selection of a proper metal for replacement of polycrystalline silicon as the metal gate in future generation transistors has been hampered by pinning of the metal Fermi level at the metal/dielectric interface. Using monoclinic hafnia and zirconia as the gate dielectric we compare three different metal gate/gate dielectric interface structures where the oxygen affinity of the metal gate varies from low to high under normal processing conditions. For each of the metal gate/gate dielectric combination we considered a number of interface stoichiometries and tried to identify the most likely interface composition by comparing the calculated and measured valence band offsets (VBO). Because density functional theory (DFT) underestimates the dielectric band gap, it also underestimates the VBO thus requiring a correction to the band edges, which we accomplished using GW for cubic and monoclinic hafnia. Our GW shift value for monoclinic hafnia (0.3 eV) indicates mostly reduced interfaces in all metal/dielectric combinations considered.

Pd/C, PdAu/C, PdCu/C, and PdTiO2/C electrocatalysts were prepared by a sodium borohydride reduction process for methane activation at low temperatures in a PEMFC reactor. These electrocatalysts were characterized by XRD, TEM, XPS, ICP-MS, ATR-FTIR, and cyclic voltammetry. The diffractograms of Pd/C, PdAu(50:50)/C, PdCu(50:50)/C, and PdTiO2(50:50)/C electrocatalysts showed peaks associated with Pd face-centered cubic structure. PdAu(50:50)/C showed a small shift in the peak center when it was compared to Pd/C, while PdCu(50:50)/C showed a shift to higher angles when it was also compared to Pd/C. This effect can be due to the formation of an alloy between Pd and Au, and Pd and Cu. By TEM experiments, a mean nanoparticle size was observed between 6.9 and 8.9 nm for all electrocatalysts. Cyclic voltammograms of Pd/C, PdAu/C, PdCu/C and PdTiO2/C electrocatalysts showed an increase in current density values after the adsorption of methane The ATR-FTIR experiments showed for all electrocatalysts the formation of methanol and formic acidic. Polarization curves at 80 °C acquired in a PEMFC reactor showed that PdAu(50:50)/C and PdTiO2(50:50)/C had superior performance when compared to Pd/C, indicating the beneficial effect of adding the co-catalyst; this behavior has been attributed to the bifunctional mechanism or electronic effect.

We report here density functional theory calculations and molecular dynamics atomistic simulations to determine the total capacitance of graphene-modified supercapacitors. The contributions of quantum capacitance to the total capacitance for boron-, sulfur-, and fluorine-doped graphene electrodes, as well as vacancy-modified electrodes, were examined. All the doped electrodes presented significant variations in quantum capacitance (ranging from 0 to ∼200 μF cm-2) due to changes in the electronic structure of pristine graphene. The graphene-modified supercapacitors show any appreciable effect on double-layer capacitance being virtually the same for all the devices investigated. The total differential capacitance was found to be limited by the quantum capacitance, and for all the systems, it is lower than the quantum capacitance over the entire voltage window. We found that the total capacitance can be optimized by considering an adequate modification to each electrode in the supercapacitor. In addition, we found that an asymmetric supercapacitor assembled with different doped electrodes, i.e. an F doped negative electrode and an N doped positive electrode, is the best choice for a supercapacitor since this combination results in better capacitance over the entire potential window.

At present, small angle X ray scattering SAXS studies of perfluorinated sulfonic acid ionomers PFSAs are unable to fully determine the true shape of their building blocks, as recent SAXS modelling predicts disk and rod like nanoionic domains as being equally possible. This scenario requires evidence based findings to unravel the real shape of PFSA building blocks. Herein, a SAXS pattern signature for a lamellar nanophase separation of the ionic domains of Nafion is presented, backed by mid and far infrared spectroscopy MIR and FIR and wide angle X ray scattering WAXS data of Nafion in different ionic forms, a broad range of ionic phase contents EW amp; 8764; 859 42 amp; 8198;252 g eq amp; 8722;1 and temperatures. The study indicates that the lamellar arrangement of the ionic domains is the most representative morphology that accounts for the physical properties of this ionomer. The lamellar SAXS reflections of Nafion are enhanced in electric and magnetic field aligned membranes, as confirmed by atomic force microscopy AFM . Electric and magnetic field assisted casting of Nafion allowed producing nanostructured and anisotropic films with the lamellas stacked perpendicularly to the field vector, which is the direction of interest for several applications. Such nanostructured Nafion membranes are bestowed with advanced optical and proton transport properties, making them promising materials for solar and fuel cells

Resistive switching (RS) devices are promising forms of non-volatile memory. However, one of the biggest challenges for RS memory applications is the device-to-device (D2D) variability, which is related to the intrinsic stochastic formation and configuration of oxygen vacancy (VO) conductive filaments (CFs). In order to reduce the D2D variability, control over the formation and configuration of oxygen vacancies is paramount. In this study, we report on the Zr doping of TaO x -based RS devices prepared by pulsed-laser deposition as an efficient means of reducing the VO formation energy and increasing the confinement of CFs, thus reducing D2D variability. Our findings were supported by XPS, spectroscopic ellipsometry and electronic transport analysis. Zr-doped films showed increased VO concentration and more localized VOs, due to the interaction with Zr. DC and pulse mode electrical characterization showed that the D2D variability was decreased by a factor of seven, the resistance window was doubled, and a more gradual and monotonic long-term potentiation/depression in pulse switching was achieved in forming-free Zr:TaO x devices, thus displaying promising performance for artificial synapse applications.

We reported herein a systematic investigation on how the nature of the support affected the catalytic performances of Rh nanoparticles. The prepared catalysts were denoted as Rh/MxOy, where M corresponded to Ce, Ti, Si, Zn, and Al, and Rh was Rh3+ reduction to Rh nanoparticles on the surface of oxides. This strategy was performed in a single step using urea as a mediator and in the absence of any other stabilizer or capping agent. The Rh nanoparticles displayed relatively similar sizes, shapes, and uniform distribution over the supports, differing only in terms of the nature of the support. This strongly affected the metal–support interaction between Rh nanoparticles and the respective oxides, leading to significant differences in their catalytic performances toward the ethanol steam reforming. Here, not only the catalytic activity (in terms of ethanol conversion) was affected, but both the selectivity and stability were also influenced by the nature of the oxide support. Interestingly, the reaction paths as well as the deactivation profile were completely changed as function of the employed support. Such differences were associated with differences in the oxygen storage, oxygen mobility, and acidity/basicity of the supports. We believe that our results can contribute to the development and understanding of Rh-supported catalysts for the applications toward gas-phase transformations such as the ethanol steam reforming reaction.

The current research reports for the first time the use of blends of poly(e-caprolactone) (PCL) and poly(ester amide) (PEA) for the fabrication of 3D additive manufactured scaffolds. Tailor made PEA was synthesized to afford fully miscible blends of PCL and PEA using different percentages (5, 10, 15 and 20% w/w). Stability, characteristic temperatures and material's compatibility were studied through thermal analyses (i.e., TGA, DSC). Even though DMTA and static compression tests demonstrated the possibility to improve the storage modulus, Young's modulus and maximum stress by increasing the amount of PEA, a decrease of hardness was found beyond a threshold concentration of PEA as the lowest values were achieved for PCL/PEA (20% w/w) scaffolds (from 0.39 ± 0.03 GPa to 0.21 ± 0.02 GPa in the analysed load range). The scaffolds presented a controlled morphology and a fully interconnected network of internal channels. The water contact angle measurements showed a clear increase of hydrophilicity resulting from the addition of PEA. This result was further corroborated with the improved adhesion and proliferation of human mesenchymal stem cells (hMSCs). The presence of PEA also influenced the cell morphology. Better cell spreading and a much higher and homogenous number of cells were observed for PCL/PEA scaffolds when compared to PCL ones.

We reported herein the synthesis in high yields (>97%) of Ce0.9Sm0.1O2-δ nanowires displaying well-defined shape, size, and composition by a simple, fast, and low-cost two-step hydrothermal method. The Ce0.9Sm0.1O2-δ nanowires synthesis was followed by the wet impregnation of Ni without the utilization of any stabilizing agent. The Ni/Ce0.9Sm0.1O2-δ nanowires showed higher surface area, high concentration of oxygen vacancies at surface, and finely dispersed Ni particles with significantly higher metallic surface area as compared with catalysts prepared from commercial materials with similar compositions. Such unique and improved properties are reflected on the catalytic performance of the Ni/Ce0.9Sm0.1O2-δ nanowires towards ethanol steam reforming. The nanowires exhibited high yields for hydrogen production (∼60% of selectivity) and an exceptional stability with no loss of activity after 192 h of reaction at 550 °C. The reported results provide insights and can inspire high-yield production of nanostructured catalysts displaying controlled and superior properties that enable practical applications in heterogeneous catalysis.

Made available in DSpace on 2021-06-25T11:12:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-06 The advancement of direct ethanol fuel cell (DEFC) represents a real challenge to electrochemical science because ethanol changes significantly the triple phase boundary properties such as the redox reactions and the proton transport. Ethanol molecules promote poor fuel cell performance due to their slow oxidation rate, reduction of the proton transport due to high affinity of ethanol by the membrane, and due to mixed potential when the ethanol molecules reach the cathode by crossover. DEFC performance has been improved by advances in the membranes, e.g., low ethanol crossover polymer composites, or electrode materials, e.g., binary/ternary catalysts. Herein, high temperature (130 °C) DEFC tests were systematically investigated by using optimized electrode and electrolyte materials: Nafion-SiO2 hybrid electrolyte and well-alloyed PtSn/C electrocatalyst. By optimizing both the electrode and the electrolyte in conjunction, DEFCs operating at 130 °C exhibited a threefold increase on performance as compared to standard commercially available materials. Instituto de Pesquisas Energéticas e Nucleares IPEN/CNEN-SP, Av. Prof. Lineu Prestes, 2242 Instituto de Química Universidade Estadual Paulista UNESP, Rua Prof. Francisco Degni, 55 Instituto de Química Universidade Estadual Paulista UNESP, Rua Prof. Francisco Degni, 55

The effect of ceria dopant aiming at stability in Ni/doped-ceria anodic layers for direct ethanol solid oxide fuel cells (SOFC) was studied. Solid solutions of ceria doped with Y, Gd, Zr, or Nb (10 mol%) impregnated with NiO were tested in a fixed bed reactor for ethanol conversion reactions and for direct (dry) ethanol SOFC. The ceria dopant showed a marked effect on both the catalytic and the electrical transport properties of the ceramic support. Catalytic activity data revealed that the studied materials deactivate in ethanol decomposition reaction but are stable for ethanol steam reforming. Thus, feeding dry ethanol to the SOFC with a Ni/doped-ceria anodic catalytic layer evidenced that water produced from the electrochemical hydrogen oxidation provides steam for the internal reforming resulting in great stability of the fuel cells tested during ~100 h. The combined catalysis and SOFC results demonstrate Ni/doped-ceria is as candidate anode layer for stable SOFC running on bioethanol.

Metal 3D printing has many potential uses within prototyping and manufacturing. Selective laser melting (SLM) is a process that uses metal powders in the micrometer range as printing material. The particle release from the entire SLM printing process is not well-studied. While the 3D printing itself often occurs in a sealed chamber, activities related to the process can potentially release harmful metal particles to the indoor working environment through resuspension of the printing powder or via incident nanoparticles generated during printing. The objective of this study was to improve the understanding of particle exposure in work processes associated with 3D printing and potential needs for interventions by a case study conducted in a 3D printing facility. In this setting, direct release and dispersion of particles throughout the workspace from processes related to metal 3D printing was investigated. The release from five activities were studied in detail. The activities included post-printing cleaning, object annealing, and preparation of new base substrate for the next printing was. Three of the five measured activities caused particles number concentrations in the working environment to increase above background levels which were found to be 8·102 cm−3. Concentrations during chamber emptying and the open powder removal system (PRS) cleaning processes increased to 104 and 5·103 cm−3, respectively, whereas grinding activity increased number concentrations to 2.5·105 cm−3. Size distributions showed that particles were mainly smaller than 200 nm. Respirable mass concentrations were 50.4 μg m−3, collected on filters. This was corroborated by respirable mass measured with a DustTrak of 58.4 μg m−3. Respirable mass concentrations were below the occupational exposure limits in Denmark for an 8 h time-weighted average.

Nonmigratory internal plasticization of poly(vinyl chloride) (PVC) is achieved by synthesis of poly(vinyl chloride)-co-poly(4,5-bis(2-ethylhexyl)-1-[6-prop-2-enoyloxy)hexyl]-1H-1,2,3-triazole-4,5-dicarboxylate) [PVC-co-P(DEHT-HA)] copolymers via free radical polymerization (FRP). Optimization of the polymerization temperature, solvent, initiator, and vinyl chloride/acrylate (VC/DEHT-HA) monomer ratio were systematically investigated, and the corresponding glass transition temperatures (Tg) of the resultant copolymers determined. These internally plasticized copolymers were characterized by 1H NMR, FTIR, SEC and DMTA. The Tg values of the PVC-co-P(DEHT-HA) copolymers range from −27 to 78 °C, and the physical properties suggest that the P(DEHT-HA) and PVC segments are miscible. Thermogravimetric analysis shows that increasing the ratio of the monomer DEHT-HA to VC increases the thermal stability. By varying the initial VC/DEHT-HA monomer ratio, one can tune the Tg of the resulting copolymer, making both the strategy and the polymer flexible.

In this work, dextran based membranes with potential to be used as implantable devices in Tissue Engineering and Regenerative Medicine (TERM) were prepared by a straightforward strategy. Briefly, two polymers approved by the Food and Drug Administration, viz. dextran and poly(e-caprolactone) (PCL) were functionalized with methacrylate moieties, and subjected to photocrosslinking. Employing different weight ratios of each polymer in the formulations allowed to obtain transparent membranes with tunable physicochemical properties and low adverse host tissue response. Independently of the material, all formulations have shown to be thermally stable up to 300 °C whilst variations in the polymer ratio resulted in membranes with different glass transition temperatures (Tg) and flexibility. The swelling capacity ranged from 50% to 200%. On the other hand, in vitro hydrolytic degradation did not show to be material-dependent and all membranes maintained their structural integrity for more than 30 days, losing only 8–12% of their initial weight. Preliminary in vitro biological tests did not show any cytotoxic effect on seeded human dental pulp stem cells (hDPSCs), suggesting that, in general, all membranes are capable of supporting cell adhesion and viability. The in vivo biocompatibility of membranes implanted subcutaneously in rats’ dorsum indicate that M100/0 (100%wt dextran) and M25/75 (25 %wt dextran) formulations can be classified as “slight-irritant” and “non-irritant”, respectively. From the histological analysis performed on the main tissue organs it was not possible to detect any signs of fibrosis or necrosis thereby excluding the presence of toxic degradation by-products deposited or accumulated in these tissues. In combination, these results suggest that the newly developed formulations hold great potential as engineered devices for biomedical applications, where the biological response of cells and tissues are greatly dependent on the physical and chemical cues provided by the substrate.

The development of a clean energy production is crucial to a sustainable and renewable energy economy. Emerging two-dimensional (2D) nanomaterials have attracted great attention for use in energy-related applications since the discovery of graphene, especially for these metal oxide nanosheets with the unique merits such as low costs, high flexibility, high active surface area, extraordinary mechanical properties, and tunable electronic properties. In this chapter, the recent advances in 2D metal oxides for energy conversion and storage devices are summarized and the strategies to address some challenges are proposed.

International audience; Partial oxidation of methane is the most attractive route to produce syngas, since it produces H2/CO (molar) = 2, suitable for Fischer-Tropsch and methanol synthesis, besides the low energy consumption and low tendency to coke formation. A promising catalyst for the reaction is based on cobalt which has low cost and low tendency to coke formation. However, it tends to oxidize and then deactivates during reaction. With the goal of preparing alternative and more efficient catalysts, lanthana-supported catalysts derived from perovskites containing lanthanum, iron and cobalt were studied in this work, using titania as support. Perovskites were prepared by the amorphous citrate method and then reduced to produce the catalysts. The samples were characterized by X-ray diffraction, Mössbauer spectroscopy, temperature programmed reduction, acidity measurements using ammonia temperature programmed desorption, transmission electron microscopy, specific surface area measurements and isotopic exchange reaction. The catalysts were evaluated at 1 atm and 800 °C in methane partial oxidation and analyzed by temperature programmed oxidation after reaction. Iron-based perovskite (LaFeO3) was not reduced regardless the support while cobalt-based perovskite (LaCoO3) produced cobalt oxides (Co3O4 and CoO), metallic cobalt and lanthanum oxide (La2O3). It was found that both titania and iron are beneficial to make cobalt reduction easier, producing more active and stable catalysts. At the end of reaction, the catalyst derived from cobalt-based perovskite (LaCoO3/TiO2) was the most active and selective, the activity and selectivity increasing during reaction. However, the supported catalyst based on iron and cobalt (LaFe0.5Co0.5O3/TiO2) is the most promising for industrial applications since it is highly active and selective since the beginning of reaction. The catalysts produced a negligible amount of coke during reaction.

We reported the organic template-free synthesis of gold (Au) nanoparticles (NPs) supported on TiO2, SiO2, and Al2O3 displaying uniform Au sizes and high dispersions over the supports. The Au-based catalysts were prepared by a deposition–precipitation method using urea as the precipitating agent. In the next step, the solvent-free oxidation of benzyl alcohol was investigated as model reaction using only 0.08–0.05 mol% of Au loadings and oxygen (O2) as the oxidant. Very high catalytic performances (TOF up to 443,624 h−1) could be achieved. Specifically, we investigated their catalytic activities, selectivity, and stabilities as well as the role of metal–support interactions over the performances. The conversion of the substrate was found to be associated with the nature of the employed support as the Au NPs presented similar sizes in all materials. A sub-stoichiometric amount of base was sufficient for the catalyst activation and the observation of the catalysts profile over the time enable insights on their recyclability performances. We believe this reported method represents a facile approach for the synthesis of uniform Au-supported catalysts displaying high performances.

Dense zirconia (8% molar yttria-stabilized ZrO2)-titanium nitride (TiN) composites are fabricated to obtain mixed ionic-electronic conducting ceramic systems with high degree of electronic and thermal conductivity. The composites are consolidated by spark plasma sintering (SPS), starting from pure powders of the pristine phases mixed in different ratios (TiN = 25, 50, 75 wt%). A careful optimization of the SPS conditions allows producing highly dense samples with no reaction between the phases or degradation by oxidation, thus maintaining the chemical integrity of the two phases. For all the composites, high electrical conductivity is attained. Samples exhibit metallic behavior, showing an unexpected percolation of TiN in the YSZ matrix for volume fraction ≤ 25 wt% (27 vol%). Chemical degradation and electrical properties of the compounds were monitored under oxidative (air) and inert (Ar) atmosphere at high temperatures. The oxidation kinetics of the nitride phase was inhibited by the microstructure of the composite. The electrical properties of such composites were explored at high temperature to evaluate its application in electrochemical devices. As results, it is shown that electrical transport properties of the composite can be tuned by both the relative volume fraction of phases and controlled oxidative treatments. Adjusting such parameters different electric behaviors were observed ranging from predominant electronic conductors, to temperature-independent resistivity, and semiconducting.

Halloysite nanotubes (HNTs) are abundant naturally-occurring hollow aluminosilicate clay mineral fibers with a typical diameter 3 and in length > 2 mm. These particles were agglomerated and/or aggregated particles where the longest individual fiber was 2 mm in length. The occupational exposure limits for refractory mineral fibers vary from 0.1 to 2 fibers cm−3. Following standard protocols for fiber analysis, detection of 0.1 fibers cm−3 would require analysis on 4 × 104 images when the filter loading is good. Thus, the fiber sampling and quantification procedures needs to be improved significantly if nanofibers

Ceria-based solid electrolytes exhibit superior electrical conductivity compared to traditional yttria-stabilized zirconia ceramics. However, they require high sintering temperatures to achieve full densification. Transition metal oxides exhibiting low melting points, such as CuO, have been used as additives to lower the sintering temperature of these materials. In this context, the present work is focused on the evaluation of the effects of gadolinium oxide (Gd2O3) content on the structure, densification and electrical properties of ceria co-doped with CuO. Nominal compositions of Ce0.99−xGdxCu0.01O2-δ (0 ≤ x ≤ 0.3) were synthesized by the polymeric precursor method. The precursor powders were characterized by simultaneous thermogravimetry and differential thermal analysis (TG/DTA) and the calcined powders were studied by X-ray diffraction (XRD) and Rietveld refinement to obtain crystallographic parameters. The sinterability of green bodies was evaluated by dilatometry up to 1200 °C. The relative density was determined in samples sintered between 950 and 1050 °C and the microstructural characterization was performed by scanning electron microscopy (SEM). The electrical properties were investigated by impedance spectroscopy (IS). The XRD results confirms the formation of a cubic fluorite type structure in the entire composition range. The lattice parameters obtained by Rietveld refinement showed a reduction in the crystallite size with increasing gadolinium content. Densification was improved with increasing Gd-content up to x = 0.15. The electrical conductivity was enhanced by gadolinium addition, reaching a maximum of 7.81 mS cm−1 at 600 °C for the composition x = 0.15 sintered at a temperature as low as 1050 °C.

We described herein the facile synthesis of sub-15 nm CeO2 nanowires based on a hydrothermal method without the use of any capping/stabilizing agent, in which an oriented attachment mechanism took place during the CeO2 nanowire formation. The synthesis of sub-15 nm CeO2 nanowires could be achieved on relatively large scales (∼2.6 grams of nanowires per batch), in high yields (>94%), and at low cost. To date, there are only a limited number of successful attempts towards the synthesis of CeO2 nanowires with such small diameters, and the reported protocols are typically limited to low amounts. The nanowires displayed uniform shapes and sizes, high surface areas, an increased number of oxygen defects sites, and a high proportion of Ce3+/Ce4+ surface species. These features make them promising candidates for oxidation reactions. To this end, we employed the selective oxidation of aniline as a model transformation. The sub-15 nm CeO2 nanowires catalyzed the selective synthesis of nitrosobenzene (up to 98% selectivity) from aniline at room temperature using H2O2 as the oxidant. The effect of solvent and temperature during the catalytic reaction was investigated. We found that such parameters played an important role in the control of the selectivity. The improved catalytic activities observed for the sub-15 nm nanowires could be explained by: i) the uniform morphology with a typical dimension of 11 ± 2 nm in width, which provides higher specific surface areas relative to those of conventional catalysts; ii) the significant concentration of oxygen vacancies and high proportion of Ce3+/Ce4+ species at the surface that represent highly active sites towards oxidation reactions; iii) the crystal growth along the (110) highly catalytically active crystallographic directions, and iv) the mesoporous surface which is easily accessible by liquid substrates. The results reported herein demonstrated high activities under ambient conditions, provided novel insights into selectivities, and may inspire novel metal oxide-based catalysts with desired performances.

Anion-exchange membranes (AEM) are envisioned as the enabling materials for the widespread use of cost-effective and efficient polymeric fuel cells. Advancing the understanding of the effect of radiation-induced grafting (RIG) method on the final properties of AEMs is crucial to boost the performance of anion-exchange membrane fuel cells (AEMFCs). The present study provides a systematic investigation of the effect of RIG methods on physicochemical properties of LDPE-based AEMs with similar degree of grafting (DoG) and ion exchange capacity (IEC). Samples grafted by two methods − pre-irradiation (PIM) and simultaneous (SM) − have the same molecular structure, but distinct physicochemical properties due to markedly differences in the degree of crosslinking. Detailed characterization of AEMs showed that RIG method determines the mechanical properties, water transport, and the distribution of ionic groups, which have a direct impact on fuel cell performance and durability. The discussed results show that grafting step directly influences the internal structure and morphology. Controlling the synthesis parameters during RIG is a key feature to design AEMs with enhanced properties that lead to high AEMFC performance and stability.

Direct ethanol SOFC have gained increasing attention in the last decade due to a series of attractive characteristic of such renewable fuel. Ethanol is possibly the most successful example of biofuel with well-developed industries in different continents. Countries with large production, such as Brazil and USA, have a wide distribution infrastructure that makes ethanol a readily available fuel. Ethanol SOFC has a great potential for several applications, including as a range extender for electric vehicles as recently demonstrated by Nissan. Nevertheless, to reduce the complexity and cost of fuel cell systems, several studies have aimed at internal reforming taking advantage of the SOFC operating temperature. Nonetheless, critical issues such as the stability of the anodes and thermal stress arising from the endothermic reforming reactions still impose great challenge for the internal reforming in SOFC. Previous studies have demonstrated direct ethanol SOFCs operating with great stability for more than 600 hours at 850 °C [1]. On the other hand, relatively few studies have investigated direct ethanol SOFCs at T< 800 °C. Intermediate operating temperatures facilitate material selection, inhibit thermally activated degradation processes, and allow a fast start of the system. However, critical issues such as the stability of the anode require careful development for stable operation at intermediate temperature (600 - 700 °C). Usually, ethanol steam reforming in this temperature range demands specific catalysts to avoid the formation of carbon deposits. Therefore, it is necessary to develop stable catalysts that are resistant to carbon formation at intermediate temperature to facilitate the commercialization of the direct ethanol SOFC technology. The aim of this study is to evaluate catalytic materials in the active layer deposited in commercial anode-supported SOFC at intermediate temperature (600 - 700 °C). Steam reforming reactions were combined with electrochemical single cell testing with different active layers containing ceria-based catalysts. The starting point was to evaluate the commercial fuel cells without an active layer under ethanol at intermediate temperature. The as-received fuel cell has reasonable stability under dry ethanol if enough water is produced by the electrochemical polarization of the fuel cell, as shown in Fig. 1. However, the Ni-based anode develops carbon deposits under operation on dry ethanol. The Ir/doped-ceria catalyst previously studied at 850 °C showing excellent durability was investigated at reduced temperature. The steam reforming results revealed that the studied catalyst deactivate at 600 °C. Increasing the measuring temperature to 700 °C revealed that the catalyst remains active, but displays small carbon deposits after the catalytic reaction, as inferred by Raman spectroscopy and thermal gravimetry analyses. The main results have shown that the catalytic layer has no significant effect on the performance of the fuel cell under hydrogen, as long the microstructural properties of the catalytic layer, such as porosity and good adhesion to the anode, are ensured. The use of a ceria-based catalytic layer has enhanced the stability of the fuel cell under dry ethanol, but small carbon deposits were still detected after ~150 hours of continuous operation. [1] Steil, M.C.; Nobrega, S.D.; Georges, S.; Gelin, P.; Uhlenbruck, S.; Fonseca, F.C. Durable direct ethanol anode-supported solid oxide fuel cell. Applied Energy, 199, 2017, p. 180-186. Figure 1

In this work, we aim at achieving the most accurate quantitative determination of the composition of exoskeletons of bivalves from Tagus estuary with Energy Dispersive X-ray Fluorescence. Samples from the shells of clams ranging from the Bronze Ages to the 16th century A.D. belonging to the Museu Arqueologico de Almada, and also from the shells of clams collected recently in the same region, were analyzed for comparison of the trace element composition and detection of heavy metals. The analysis was performed with 2 Energy Dispersive X-ray Fluorescence setups, one with triaxial geometry and another with a conventional geometry and vacuum capabilities. Samples were pressed as pellets, and the spectra collected with both setups were evaluated using standardless fundamental parameter based software's implemented in each setup, and by comparing with standard reference materials of similar matrix. The comparison of the results obtained with different methods lead to the conclusion that the most realistic results were obtained with calibration curves obtained with external standards and correction the fluorescent intensities with the Compton scattering peak. When comparing the obtained concentrations for all the analyzed periods, results showed a decrease of Fe in the 12th Century. Regarding the environmental current state of the Tagus estuary, there were no heavy metals detected above the safety regulations.

The main goal of this work was the development of fully biobased unsaturated polyesters (UPs) that upon crosslinking with unsaturated monomers (UM) could lead to greener unsaturated polyester resins (UPRs) with similar thermomechanical properties to commercial fossil based UPR. After the successful synthesis of the biobased UPs, those were crosslinked with styrene (Sty), the most commonly used monomer, and the influence of the chemical structure of the UPs on the thermomechanical characteristics of UPRs were evaluated. The properties were compared with those of a commercial resin (Resipur 9837©). The BioUPRs presented high gel contents and contact angles that are similar to the commercial resin. The thermomechanical properties were evaluated by dynamic mechanical thermal analysis (DMTA) and it was found that the UPR synthesized using propylene glycol (PG), succinic acid (SuAc) and itaconic acid (ItAc) presented very close thermomechanical properties compared to the commercial resin.

SSCI-VIDE+ATARI+PGE; International audience; Anode-supported solid oxide fuel cells accumulating more than 700 h of stable operation on dry ethanol with high current output are reported. A highly active ceria-based catalytic layer deposited onto the anode efficiently converts the primary fuel into hydrogen using the electrochemically generated steam. On the other hand, standard fuel cells without the catalytic layer collapse because of carbon deposit formation within the initial 5 h of operation with ethanol. The nanostructured ceria-based catalyst forms a continuous porous layer (similar to 25 mu m thick) over the Ni-based anode support that has no apparent influence on the fuel cell operation and prevents carbon deposit formation. Moreover, the catalytic layer promotes overall steam reforming reactions of ethanol that result in similar current outputs in both hydrogen and ethanol fuels. The stability of single cells, with relatively large active area (8 cm(2)), confirms the feasibility of a catalytic layer for internal reforming of biofuels in solid oxide fuel cells. The experimental results provide a significant step towards the practical application of direct ethanol solid oxide fuel cells. (C) 2017 Elsevier Ltd. All rights reserved.

Gadolinium-doped cerium oxide (GDC) is an attractive ceramic material for solid oxide fuel cells (SOFCs) both as the electrolyte or in composite electrodes. The Ni/GDC cermet can be tuned as a catalytic layer, added to the conventional Ni/yttria-stabilized zirconia (YSZ), for the internal steam reforming of different fuels. Such an anode allows the SOFC to operate with hydrocarbon fuels by internal reforming. GDC exhibits high oxygen ion conductivity at a wide range of temperatures and displays a high resistance to carbon deposition. However, an inconvenience of ceria-based oxides is the high sintering temperature needed to obtain a fully dense ceramic body, which can result in undesired reactions with YSZ. In this study, a green chemistry route for the synthesis of 10 mol% GDC nanoparticles is proposed. Such a low temperature synthesis provides control over particle size and sinterability of the material. The aqueous precipitation method starts from the nitrates of both cerium and gadolinium and uses excess hexamethylenetetramine (HMT) to produce crystalline GDC at 80 ºC. As-produced powders were found to be GDC crystalline fluorite-type structure, with crystallite size ≤ 10 nm. Thermalgravimetric analysis show a small mass loss and dilatometry profiles show a total retraction of ˃ 20% up to 1400 °C. The electrical properties of the material were studied by impedance spectroscopy measurements of sintered samples in a controlled atmosphere. The samples sintered for 2 hours at 1400 °C exhibited electrical conductivity comparable to previously reported data for GDC.

We employed self-energy corrected density functional theory (GGA-1/2) to investigate the band alignment between platinum and the layered perovskite Aurivillius ferroelectrics SrBi2Ta2O9 (SBT), Bi4Ti3O12 (BIT), and La-substituted BIT (BLT). The original GGA-1/2 method was found to not give satisfactory band gaps for these layered materials, despite yielding substantially better band gaps than GGA. We show that in such layered materials the cutoff radius for the self-energy potential in GGA-1/2 is strongly inhomogeneous across layers, therefore requiring different cutoff radii assigned to oxygen anions located in bismuth oxide layers and in pseudo-perovskite layers. After a 2D optimization of the oxygen cutoff radii, the calculated band gaps for these materials were found within 0.3 eV of experimental values. Next, we developed stoichiometric interface models for Pt/SBT and Pt/BIT, assuming platinum was connected to bismuth oxide layers as suggested by experiments. The calculated Schottky (hole) barriers for abrupt interfaces are 1.58 eV (2.50 eV) and 2.06 eV (1.41 eV) for SBT and BIT, respectively. For Pt(Bi) alloyed interfaces, where according to experiments some Bi diffuses inside the metal, we calculated a downshift of the Fermi level, lowering the barrier for holes. Because the barrier height for holes is lower in Pt/BIT than in Pt/SBT, a higher space-charge-limited-conduction hole current is expected to leak through metal alloyed Pt(Bi)/BIT/Pt(Bi) capacitors than to the corresponding SBT capacitors. Finally, replacing some Bi in the pseudo-perovskite layers with La significantly increased the barrier for holes. Based on the results above, we propose a phenomenological model for ferroelectric fatigue in Pt/BIT/Pt, whereby the formation of a non-ferroelectric Bi-deficient phase is the main reason for fatigue, which is accelerated by the lowered barrier for holes promoting the accumulation of Bi vacancies. The fatigue-free nature of Pt/SBT/Pt and Pt/BLT/Pt, on the other hand, stems from large barriers for both electrons and holes, which prevent the neutralization and further accumulation of charged defects. Our conclusions are consistent with the available experimental data.

The improvement of flexural properties of polypropylene (PP) could be achieved by blending it with a stiffer polymer like poly(ethylene terephthalate) (PET). The main problem is the compatibilization between a saturated, apolar structure with a polar polyester. Copolymers of glycidyl methacrylate (GMA) and 2-ethylhexyl acrylate (EHA) were prepared, characterized and used as compatibilizers in PP/PET (70/30 wt%) blends at different feed ratios. The effects of compatibilization of these polymers were analyzed by SEM, which shows reduction of the size of PET granules, and by TGA, with an increase in the thermal stability of the compatibilized blends. Thermal properties corresponding to melting and crystallization events were also changed by the introduction of the compatibilizers. The DMTA shows that the Tg of the PET domain is affected by compatibilization, contrary to the Tg of PP domain. The compatibilization efficiency was further confirmed by an increase in flexural strain at flexural strength (eFM).

SLM accuracy for fabricating porous materials is a noteworthy hindrance when aiming to obtain biomaterial cellular structures owing precise geometry, porosity, open-cells dimension and mechanical properties as outcomes. This study provides a comprehensive characterization of seventeen biomaterial Ti6Al4V-based structures in which experimental and numerical investigations (compression stress-strain tests) were carried out. Mono-material Ti6Al4V cellular structures and multi-material Ti6Al4V-PEEK cellular structures were designed, produced by SLM and characterized targeting orthopedic implants. In this work, the differences between the CAD design and the as-produced Ti6Al4V-based structures were obtained from image analysis and were used to develop predictive models. The results showed that dimensional deviations inherent to SLM fabrication are systematically found for different dimensional ranges. The present study proposes several mathematical models, having high coefficients of determination, that estimate the real dimensions, porosity and elastic modulus of Ti6Al4V-based cellular structures as function of the CAD model. Moreover, numerical analysis was performed to estimate the octahedral shear strain for correlating with bone mechanostat theory limits. The developed models can help engineers to design and obtain near-net shape SLM biomaterials matching the desired geometry, open-cells dimensions, porosity and elastic modulus. The obtained results show that by using these AM structures design it is possible to fabricate components exhibiting a strain and elastic modulus that complies with that of bone, thus being suitable for orthopedic implants., This work was supported by FCT (Fundacao para a Ciencia e a Tecnologia) through the grant SFRH/BD/128657/2017, the projects PTDC/EMS-TEC/5422/2014ADAPTPROSTHESIS, POCI-01-0145-FEDER-030353 (SMARTCUT), NORTE 010145_FEDER-000018-HAMaBICo and UID/EEA/04436/2019.

Mass diffusion controls material structuring from the atomic to the macro-scale defining properties and functionalities. We show here that surface energy in Ce0.9Gd0.1O3-d shaped nanocrystals, i.e. nanocubes, nanorods and spherical nanoparticles, can control solid state diffusion mechanisms over a long range, leading to extreme microstructural diversity.

In situ and ex situ spatially-resolved techniques are employed to investigate reactant distribution and its impacts in a polymer electrolyte fuel cell. Temperature distribution data provides further evidence for secondary flows inferred from reactant imaging data, highlighting the contribution of convection in heat as well as reactant distribution. Water build-up from neutron tomography is linked to component degradation, matching the pattern seen in the reactant distribution and thus suggesting that high, non-uniform local current densities shape degradation patterns in fuel cells. The correlations shown between different techniques confirm the use of the versatile reactant imaging technique, which is used to compare commonly used flow field designs. Among serpentine-type designs, the single serpentine is superior in both equivalent current density and reactant distribution, showing large contributions from convective flow. On the other hand, the interdigitated design is shown to produce larger equivalent current densities, while showing a somewhat poorer reactant distribution. Considering the correlations drawn between the techniques, this suggests that the interdigitated design compromises durability in favour of power output. The results highlight how established techniques provide a robust background for the use of a new and flexible imaging technique toward designing advanced flow fields for practical fuel cell applications.

Unsaturated polyester composites (UPCs) were prepared from biobased unsaturated polyester resins (UPRs) and nanoprecipitated calcium carbonate (NPCC). The UPRs were obtained from the crosslinking reaction of an unsaturated polyester (UP) made from renewable monomers and styrene (St) or a mixture of St with a designed lactic acid-based crosslinker (BPPC). The UPCs were obtained by adding the NPCC to the formulations. Aspects of the composition of the UPs and of the BPPC were confirmed by FTIR and 1H NMR spectroscopies. Different UPCs were prepared and the influences of the addition of NPCC and of the amount of BPPC on their thermomechanical properties were evaluated. The BPPC has a major influence on the properties of the UPCs, namely a significant improvement of mechanical properties and of the thermal stability of UPCs. Both results suggest that the BPPC may be acting as a compatibilizer between the polymer matrix and the filler.

The manganes(III) complex functionalised with 2,3-dihydropyridazine has been encapsulated in the supercages of the NaY zeolite using two different procedures, flexible ligand and in situ complex. The parent zeolite and the encapsulated manganese(III) complexes were screened as catalysts for styrene oxidation by using t-BOOH as the oxygen source in acetonitrile. Under the optimized conditions, the catalysts exhibited moderate activity with high selectivity to benzaldehyde, IKB thanks to Foundation for the Science and Technology (FCT, Portugal), for the contract under 'Programa Ciencia 2007 and for the contract under the project "n-STeP - Nanostructured systems for Tail" (NORTE-07-0124-FEDER-000039, supported by Norte (ON.2). FCT and FEDER (European Fund for Regional Development)-COMPETE-QREN-EU for financial support to the Research Centres, CQ/UM [PEst-C/QUI/UI0686/2013 (F-COMP-01-0124-FEDER-037302). This work is funded also by FEDER funds through the Operational Programme for Competitiveness Factors - COMPETE and by National Funds through FCT - Foundation for Science and Technology under the grant PEST-C/EQB/LA0006/2013/37285., info:eu-repo/semantics/publishedVersion

Under a Creative Commons license.-- et al., The ceramic industry is an industrial sector in need of significant process changes, which may benefit from innovative technologies such as laser sintering of ceramic tiles. Such innovations result in a considerable research gap within exposure assessment studies for process-generated ultrafine and nanoparticles. This study addresses this issue aiming to characterise particle formation, release mechanisms and their impact on personal exposure during a tile sintering activity in an industrial-scale pilot plant, as a follow-up of a previous study in a laboratory-scale plant. In addition, possible particle transformations in the exhaust system, the potential for particle release to the outdoor environment, and the effectiveness of the filtration system were also assessed. For this purpose, a tiered measurement strategy was conducted. The main findings evidence that nanoparticle emission patterns were strongly linked to temperature and tile chemical composition, and mainly independent of the laser treatment. Also, new particle formation (from gaseous precursors) events were detected, with nanoparticles 87% efficiency in particle number concentrations removal., This work was supported by the European Commission FP7 (FP7-PEOPLE-2012-ITN) Marie Curie ITN project no. 315760 (HEXACOMM) and by the Spanish MINECO (PCIN-2015-173-C02-01) under the frame of SIINN, the ERA-NET for a Safe Implementation of Innovative Nanoscience and Nanotechnology, through SIINN-ERANET project CERASAFE (id.:16). Additional support was provided by LIFE projects AIRUSE (LIFE11 ENV/ES/584), CERAMGLASS (LIFE11 ENV/ES/560) and LASERFIRING (LIFE09 ENV/ES/435).

Vinyltrimethoxysilane (VTMS), methyltrimethoxysilane (MTMS) and tetramethylorthosilicate (TMOS) were mixed in a one-step basic catalyzed sol–gel chemistry, to produce flexible and good thermal insulator silica-based aerogels. Moreover, mechanical reinforcement of the aerogels with a polymer phase was accomplished via free radical polymerization using either the macromer poly(ethylene glycol) diacrylate (PEG-DA) or the monomer 2-(dimethylamino)ethyl methacrylate (DMAEMA), the latter case resulting in the grafting of PDMAEMA. Both the influence of using a monomer or a macromer and of applying two different polymer grafting approaches—one-pot synthesis or gel soaking—on the aerogels’ final properties were analyzed. It was concluded that gel soaking strongly limits the diffusion of the organic moieties, creating heterogeneous materials. This approach led to denser and less hydrophobic aerogels with worse mechanical properties. The incorporation of low amounts of polymer with one-pot synthesis led to an improvement in the aerogels properties, making them less dense, more flexible and better insulators. The one-pot method also allowed to obtain aerogels with a very well-defined microstructure, due to the porogen role of the polymer, hence generating homogenous materials. It was found that the major differences in the aerogels properties occurred with different grafting approaches and not with different polymer phases, and the molecular weight of the organic moieties was not determinant for the materials homogeneity, in the studied cases. The obtained bulk densities ranged from 122 to 181 kg m−3, the thermal conductivity from 0.050 to 0.072 W m−1 K−1 and the modulus achieved 327 kPa. The addition of DMAEMA generated the best results when using the one-pot approach, providing the lightest and uncommonly flexible thermal insulator aerogels (modulus of ~70 kPa).

This paper reports the development of new unsaturated polyesters resins (UPRs) based on soybean oil and coconut oil. Unsaturated polyesters (UPs) were firstly synthesized by polycondensation from renewable monomers and were further crosslinked using styrene. The chemical structure of the new UPs was confirmed by attenuated total reflectance Fourier Transform Infrared (ATR-FTIR) and by proton Nuclear Magnetic Resonance (1H NMR) spectroscopies. The thermal and mechanical properties of the UPs and UPRs were studied by thermogravimetric analysis (TGA) and by dynamic mechanical thermal analysis (DMTA) to evaluate the impact of the incorporation of renewable monomers in the properties of the materials. TGA analysis revealed that bio-based UPs are thermally stable until temperatures of 250 °C. The Tg values obtained for these new UPs varied between −11 °C and 2 °C, being the UP composed by bio-based soybean oil and propylene glycol the resin with the highest Tg. As expected, after crosslinking UPRs showed to be thermally more stable than the UPs. The DMTA analysis revealed that the E' and the Tg could be easily tailored by varying the monomers in the formulation.

During occupational exposure studies, the use of conventional scanning mobility particle sizers (SMPS) provides high quality data but may convey transport and application limitations. New instruments aiming to overcome these limitations are being currently developed. The purpose of the present study was to compare the performance of the novel portable NanoScan SMPS TSI 3910 with that of two stationary SMPS instruments and one ultrafine condensation particle counter (UCPC) in a controlled atmosphere and for different particle types and concentrations. The results show that NanoScan tends to overestimate particle number concentrations with regard to the UCPC, particularly for agglomerated particles (ZnO, spark generated soot and diesel soot particles) with relative differences >20%. The best agreements between the internal reference values and measured number concentrations were obtained when measuring compact and spherical particles (NaCl and DEHS particles). With regard to particle diameter (modal size), results from NanoScan were comparable < [± 20%] to those measured by SMPSs for most of the aerosols measured. The findings of this study show that mobility particle sizers using unipolar and bipolar charging may be affected differently by particle size, morphologies, particle composition and concentration. While the sizing accuracy of the NanoScan SMPS was mostly within ±25%, it may miscount total particle number concentration by more than 50% (especially for agglomerated particles), thus making it unsuitable for occupational exposure assessments where high degree of accuracy is required (e.g., in tier 3). However, can be a useful instrument to obtain an estimate of the aerosol size distribution in indoor and workplace air, e.g., in tier 2., This work was supported by grants from the European Community's FP7 (FP7-PEOPLE-2012-ITN) no. 315760 (HEXACOMM project). Additional support was provided by European project nanoIndEx which is supported by the French National Funding Agency for Research (ANR), the German Federal Ministry of Education and Research (BMBF, IUTA grant no.: 03×0127A), the British Technology Strategy Board (TSB) and the Swiss TEMAS AG, under the frame of SIINN, the ERA-NET for a Safe Implementation of Innovative Nanoscience and Nanotechnology.

The relationship between electrical and morphological properties of annealed Nafion samples is investigated by X-ray diffraction (XRD), small angle X-ray scattering (SAXS), atomic force microscopy (AFM), and impedance spectroscopy. Experimental data reveal that the heat treatment at high temperature (T ∼130–140 °C) with low relative humidity (RH ∼0%) results in significant changes of Nafion such as increased crystallinity and decreased average distance of hydrophilic domains. Such effects were practically absent when the same heat treatment was carried out at high RH ∼100%. The effects of annealing with controlled RH were reflected in the polymer electrolyte fuel cell (PEFC) tests in which the measured performance was markedly reduced for Nafion samples annealed at low RH. Such a feature was related to decreased microstructural stability, water sorption and proton conductivity of the annealed membrane. The observed effects are relevant to evaluate degradation of Nafion during both fuel cell assembly and harsh PEFC operating conditions. Moreover, the experimental results contribute to advance the understanding of Nafion’s properties at high temperature for the development of high-performance ionomer membranes.

The preparation of high performance materials using renewable resources is a prime goal in materials science. Composites are amply recognized as an effective route to achieve a new portfolio of advanced materials with high performance. The comprehensive understanding of the structure/properties relationships is crucial to achieve such goal. Therefore, the detailed characterization of the viscoelastic properties of composites is an essential step in the development process. This review describes the use of Dynamic Mechanical Thermal Analysis (DMTA) in the viscoelastic characterization of composites, and a brief description about the utility of the DMTA in the study of their structure/properties relationships is given. The paper is focused on the discussion of the most relevant publications in the area.

The synthesis and characterisation of a novel family of unsaturated polyesters (UPs) and their crosslinked resins (UPRs) based on 2,5-furandicarboxylic acid (FDCA) are reported. Their original features stem from the use of FDCA as the aromatic monomer, and also from the fact that UPs are entirely based on renewable resources, oppositely to most reported materials which are typically based on petrochemicals or instead they are derived from both petrochemicals and a percentage of renewables. Additionally, instead of styrene, 2-hydroxyethylmethacrylate (HEMA) was used as the reactive solvent to obtain the UPRs. These novel resins showed adequate thermal and mechanical behavioural tendencies similar to petrochemical ones, namely high glass transition temperature (up to 104 degrees C) and good thermal stability (up to 230 degrees C). These characteristics enhance their prospects of being a successful renewable-based material.