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Cr1.8Ti0.2O3+z (CTO) particles were grown by a sol–gel route followed by two thermal treatments at 1273 K. Magnetic susceptibility studies showed a para- to antiferromagnetic transition at around 3...

This study aims to better understand the Fe role in the hydrogen sorption kinetics of Mg–Fe composites. Mg-8 mol% Fe nanocomposites produced by high energy reactive milling (RM) for 10 h resulted in MgH2 mixed with free Fe and a low fraction of Mg2FeH6. Increasing milling time to 24 h allowed formation of a high fraction of Mg2FeH6 mixed with MgH2. The hydrogen absorption/desorption behavior of the nanocomposites reactive milled for 10 and 24 h was investigated by in-situ synchrotron X-ray diffraction, thermal analyses and kinetics measurements in Sieverts-type apparatus. It was found that both 10 and 24 h milled nanocomposites presents extremely fast hydrogen absorption/desorption kinetics in relatively mild conditions, i.e., 300–350 °C under 10 bar H2 for absorption and 0.13 bar H2 for desorption. Nanocomposites with MgH2, low Fe fraction and no Mg2FeH6 are suggested to be the most appropriate solution for hydrogen storage under the mild conditions studied.

In this work, we propose the use of regular branching of polyurethanes as a way to regulate chain dynamics and govern crystallization in highly dense hydrogen-bonded systems. As a result, robust and healable polyurethanes can be obtained. To this end, we synthesized a range of aliphatic propane diol derivatives with alkyl branches ranging from butyl (C4) to octadecanyl (C18). The series of brush polyurethanes was synthesized by polyaddition of the diols and hexamethylene diisocyanate. Polyurethanes with very short (C 4) and very long (C = 18) brush lengths did not lead to any significant healing due to crystallization. An intermediate amorphous regime appears for polymers with middle branch lengths (C = 4 to 8) showing a fine control of material toughness. For these systems, the side chain length regulates tube dilation, and significant macroscopic healing of cut samples was observed and studied in detail using melt rheology and tensile testing. Despite the high healing degrees observed immediately after repair, it was found that samples with medium to long length brushes lost their interfacial strength at the healed site after being heated to the healing temperature for some time after the optimal time to reach full healing. Dedicated testing suggests that annealed samples, while keeping initial tackiness, are not able to completely heal the cut interface. We attribute such behavior to annealing-induced interfacial crystallization promoted by the aliphatic branches. Interestingly, no such loss of healing due to annealing was observed for samples synthesized with C4 and C7 diols, which is identified as the optimal healing regime. These results point at the positive effect of branching on healing, provided that a critical chain length is not surpassed, as well as the need to study healing behavior long after the optimal healing times.

Ordered-hexagonal silica materials, such as Mobil crystalline material-41 and Santa Barbara amorphous-15, have important applications in heterogeneous catalysis and biomass conversion due to their chemical stability and mesoporous structure. Low-temperature grafting (LG) is one of the most common functionalization methods used to modify the acidity/basicity or hydrophobicity/hydrophilicity of the surface. However, the materials prepared by this method are prone to leaching of functional groups into the reaction medium. The exact nature of the leaching phenomenon has not been fully addressed in the literature. In this contribution, we have investigated this process at the molecular level by combining well-controlled reaction experiments and several characterization techniques (Fourier transform infrared, 1H-29Si cross-polarization magic-angle spinning NMR, X-ray diffraction, thermogravimetric analysis, and N2 adsorption-desorption). We have found that leaching is originated by the presence of terminal surface silanols, which render the catalysts susceptible to the attack of water and polar compounds. Hence, instead of simple detaching of functional groups, leaching can be better described as a partial dissolution of the surface layers of the silica, which of course also removes the functional groups during this process. Therefore, an effective strategy to minimize leaching is to reduce the density of free silanols via full functionalization of the surface. We propose a novel silylation method, high-temperature grafting, which allows the grafting process to be conducted at high temperatures (180 °C) under solvent-free conditions. By this method, a more complete silylation of surface silanols can be obtained. Consequently, the samples prepared by this high-temperature grafting method show to be highly stable during acid-catalyzed alkylation reaction, conducted under severe conditions (high temperature and in the presence of polar solvents).

Natural materials provide an increasingly important role model for the development and processing of next-generation polymers. The velvet worm Euperipatoides rowelli hunts using a projectile, mechanoresponsive adhesive slime that rapidly and reversibly transitions into stiff glassy polymer fibers following shearing and drying. However, the molecular mechanism underlying this mechanoresponsive behavior is still unclear. Previous work showed the slime to be an emulsion of nanoscale charge-stabilized condensed droplets comprised primarily of large phosphorylated proteins, which under mechanical shear coalesce and self-organize into nano- and microfibrils that can be drawn into macroscopic fibers. Here, we utilize wide-angle X-ray diffraction and vibrational spectroscopy coupled with in situ shear deformation to explore the contribution of protein conformation and mechanical forces to the fiber formation process. Although previously believed to be unstructured, our findings indicate that the main phosphorylated protein component possesses a significant β-crystalline structure in the storage phase and that shear-induced partial unfolding of the protein is a key first step in the rapid self-organization of nanodroplets into fibers. The insights gained here have relevance for sustainable production of advanced polymeric materials.

The elastic modulus of corrosion product (Ecp) has been reported with significant variations in the literature. This study aims to investigate the Ecp of naturally-generated chloride-induced corrosion products formed in different concrete mixes. Microstructural characterization was conducted through nano-indentation, electron microscopy and Raman spectroscopy. The corrosion products were mainly composed of a goethite matrix with portions of maghemite, independently of the concrete composition. Microscopic analysis suggest that layers of corrosion products grow at different times and under different physico-chemical conditions. Our measurements showed that Ecp varied between 80−100 GPa, which can be suggested for numerical models of corrosion induced cracking.

A hyphenated optical-electrochemical technique and image analysis protocol is used to quantify global and local (intermetallic) corrosion process and kinetics. Our findings reveal an early stage (< 60 s) composition-dependent hierarchical local activation of all IMs that can be attributed to IM dealloying. This is followed by local trenching initiated at matrix locations adjacent to regions of the IMs previously dealloyed, which in turn develops into concentric trenching around the IMs. These stages have quantifiable activation times and kinetics. While dealloying kinetics are found to be strongly dependent on IM composition and slightly dependent on IM size in the case of the S-phases, trenching kinetics are IM composition and size independent.

The effects of the soft block fraction and H-bond state in thermoplastic polyurethanes on autonomous entropy-driven scratch closure and barrier restoration are studied. To this aim, comparable polyurethanes with different segmentation states are applied as organic coatings on plain carbon steel plates, scratched under very well-controlled conditions, and the scratch closure and sealing kinetics are studied in detail. The scratch closure is measured optically, while the barrier restoration is probed by the accelerated cyclic electrochemical technique (ACET). Scratch closure, attributed to entropic elastic recovery (EER), is followed in a marked two-step process by barrier restoration governed by local viscous flow and the state of the interfacial hydrogen bonding. Polyurethanes with a lower soft phase fraction lead to a higher urea/urethane ratio, which in turn influences the healing efficiency of each healing step. Interestingly, softer polyurethanes leading to efficient crack closure were unable to sufficiently restore barrier properties. The present work highlights the critical role of the soft/hard block and urea/urethane H-bond state content on crack closure and barrier restoration of anticorrosive organic coatings and points at design rules for the design of more efficient corrosion-protective self-healing polyurethanes.

The use of rheology and terminal flow relaxation times to predict healing behavior at long healing times is by now quite well accepted. In this work we go one step further and explore the use of macro-rheology (in particular the stored work of deformation) to predict the early stage interfacial healing properties (fracture resistance) of a set of self-healing polyurethanes. The interfacial healing is measured by single edge notch fracture experiments, using short healing times and a low healing temperature to exclude the effect of long range molecular motion on mechanical properties restoration. The systems based on aromatic diisocyanates show high fracture resistance after healing, while very limited restoration of the mechanical properties is observed for aliphatic and cycloaliphatic based polyurethanes. Linear sweep rheology and time-temperature-superposition allow obtaining the macro-rheological master curve and the mechanical relaxation spectra (H(t)). The application of a recently established deconvolution protocol to the H(t) gives the characteristic relaxation times and stored works of deformation associated to individual dynamic processes such as segmental motion, reversible bonds, and terminal flow. It is found that the calculated stored works of deformation related to the reversible bond relaxation reproduce the trend observed by fracture resistance at healed interfaces and reveal a qualitative correspondence between reversible bonds work of deformation and interfacial healing fracture resistance. Moreover, the method seems to point to the existence of a threshold interfacial work of deformation below which no efficient load transfer can be observed.

Earlier studies on cerium-loaded naturally occurring silica microparticles (i.e., diatomaceous earth) demonstrated the potential to efficiently protect small scratches in epoxy-coated AA2024-T3 panels during relatively short immersion times. The current work investigates the potential of such inhibitor-loaded microparticles to protect wide and deep scribes (up to 1 mm wide) in long-time immersion testing and during cyclic (wet/dry) conditions. For this, cerium nitrate and 2,5-dimercaptothiadiazole (DMTD) were used as inorganic and organic corrosion inhibitors. The corrosion protection was evaluated using a hyphenated real-time optics/electrochemistry method and two individual local techniques measuring oxygen concentration and electrochemical impedance (LEIM) inside the scribe. SEM/EDS was used to analyze the samples after exposure. The results show significant levels of corrosion protection at damaged locations at low cerium concentrations (3.7 wt % Ce3+ relative to the total coating mass) during 30 days of immersion in salt solution. However, for a given scribe geometry, the protection was found to be dependent on the electrolyte volume with larger electrolyte/exposed metal ratios leading to short protection time. A partial replacement of the Ce3+ by DMTD in the microcarriers resulted in a higher degree of passivation than when DMTD was used alone. Wet/dry cyclic exposure tests showed that cyclic conditions can increase the buildup of stable inhibitor-containing layers in the case of cerium-loaded silica microparticles. This underlines the need for more research using wet/dry exposure conditions.

Structural stability is a pivotal property required for Nb2O5 to be applied as a solid-acid catalyst in heterogeneous catalytic reactions. When combined with Ni, Nb2O5 produces cheap and active hyd...

Real-time optical analysis is used to improve the interpretation of electrochemical noise signals (EN). The concept is presented for the case of AA2024-T3 under immersion in various NaCl concentrations. An in-house developed optical-electrochemical technique allowed for high spatiotemporal resolution and was used to visualize and quantify surface changes in parallel with monitoring EN signals. EN analysis was performed in the time-frequency domain using continuous wavelet transform (CWT). Correlations between the two procedures enabled the identification of corrosion processes in time, such as de-alloying, etching, pitting and subsurface corrosion. Besides this, optical measurements at higher magnification were used to analyse a smaller section of the exposed metal with a spatial resolution below 1 μm. This enabled the quantification on the size, number and nearest neighbor distance of local corrosion events, such as pits and corrosion rings. The set-up and optical protocol allowed for the first time (i) to establish a direct relationship between EN signals and the occurrence of specific localized corrosion phenomena and (ii) an in-situ highly-resolved monitoring of local corrosion processes. As a final result of the optical analysis we introduce a straightforward illustration that allows the direct identification of EN features to macroscopic local corrosion phenomena.

Starting from experimental macro-rheological data, we develop a fitting protocol that succeeded in the separation of the overlapping relaxation phenomena in the dissipative regime for a set of intrinsic healing polymers healing most effectively near their glass transition temperature T g . To allow for a proper deconvolution, the rheological master curves are converted to a relaxation spectrum (H(τ)) and this is fitted using an optimized mechanical model, e.g. the Maxwell-Weichert model. The deconvolution of overlapping segmental mobility and reversible interactions is successfully demonstrated for a set of polyimide and polyamide polymers containing none, one and two reversible dynamic features near-T g . Through the fitting parameters, the relaxation timescale of each feature and their apparent process enthalpies are obtained. The quantitative data obtained using the fitting protocol are then compared to macroscopic healing results. As a result, a clear correspondence between the energy stored by the system to accomplish reversible (e.g. H-bonds, π-π) and chain interdiffusion relaxation transitions and the healing efficiency of such polymers are obtained. The implementation of this protocol allows for a clearer identification of the relevant mechanisms in self-healing polymers and paves the way for the development of more efficiently healable polymeric systems.

Superabsorbent polymers (SAPs) are well known for their ability to absorb and hold high water amounts accompanied by a high volume expansion. In this work we show the benefits of this underlying property of SAPs to induce underwater crack closure with subsequent barrier restoration in damaged protective coatings. For the proof of concept, three layer epoxy-polyester (EP) powder coating systems were developed and applied on carbon steel. In these systems the middle EP layer (also called functional layer) contained crosslinked acrylamide/acrylic acid copolymer SAPs in different amounts ranging from 0 to 40 wt%. The capability of the SAPs to close damages and extend barrier and corrosion protection was evaluated by electrochemical impedance spectroscopy (EIS), NaCl aqueous solution immersion test and optical microscopy. It was found that coatings loaded with a 20 wt% SAP led to the best overall corrosion protection for the studied systems. In order to proof the potential use of this extrinsic healing concept for multiple healing events wet-dry cycles on scratched systems were performed and the corrosion performance was followed by EIS. Although not yet optimal, the results show the potential of the concept for multiple healing events under wet-dry conditions.

Remote access to XAFS beamlines is an attractive option to reduce costs and provide an access route for educational and collaborative purposes. Any degree of automation of the operations, even if partial and limited to routine procedures, allows simplification of the remote user interface with significant improvement in the overall beamline efficiency. Here, some useful steps towards achieving this goal are introduced and the experience in this regard at the XAFS beamlines at LNLS and Diamond is described., Although remote access to beamline synchrotron facilities is now a common operation mode at macromolecular crystallography beamlines thanks to substantial efforts in automated processes for sample preparation and handling, experiment planning and analysis, this is still not the case for XAFS beamlines. Here the experience and developments undertaken at LNLS and Diamond in automation are described, in an attempt to tackle the specific challenges posed by the high variability in experimental conditions and configurations that XAFS measurements require.

Miscible S-SBR (solution styrene–butadiene copolymer)/BR (polybutadiene homopolymer) blends are used in multiple applications like modern passenger car tire treads. Despite their miscibility, there is a problem to predict tire performance due to dynamical heterogeneities present in the S-SBR/BR blends. On the one hand, S-SBR/BR blends have a thermorheologically complex behavior, which complicates the prediction of the temperature- and frequency-dependence of material properties. On the other hand, due to differences in the polarity of the individual components, the extender oils used in the elastomeric compounds could distribute unequally within the blends, where little is known about how oils interact with the two polymers. In this work a combination of Differential Scanning Calorimetry, Dynamic Mechanical Analysis, and Broadband Dielectric Spectroscopy (BDS) is used to clarify: (i) the thermorheological complexity of S-SBR/BR blends, (ii) the effect of the extender oil on the blend. The broad frequency operation of BDS allows for the analysis of the S-SBR and BR component dynamics and the effect of the oil on each of them within an S-SBR/BR (50/50) blend. Based on the discretization of individual component dynamics in the blend, conclusive remarks are made on the effect of the extender oil for either component in the blend. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 842–854., The authors are indebted to H&R €Olwerke Schindler GmbH (Hamburg, Germany) for their scientific, financial, and materials support of the current project as well as the permission to publish this work. M. Hernandez acknowledges the European Commission for a Marie Curie Fellowship (PIEF-GA-2013– 623379). The authors also acknowledge J. Bijleveld (TU Delft) for the DSC measurements.

In this study, the MgZrTiFe0.5Co0.5Ni0.5 high entropy alloy was processed by high-energy ball milling under both argon and hydrogen atmospheres. The hydrogen storage behavior of the samples was evaluated by combination of thermal analyses and in-situ synchrotron powder X-ray diffraction. It is shown that this alloy forms a body-centered cubic (BCC) structure when milled under argon pressure. The BCC phase is capable to absorb up to 1.2%wt. of hydrogen and during absorption it undergoes a phase transition forming a face-centered cubic (FCC) high entropy hydride. This FCC hydride can be directly synthesized by high-energy ball milling under hydrogen pressure.

This work reports on the development of a novel polymer blend with thermally triggered shape memory and self-healing properties. Blends were prepared by mixing a self-healing ionomer (Surlyn 9520) and polycyclooctene (with and without crosslinking agent) in different ratios. The regions of thermal activation were determined by thermogravimetric analysis, differential scanning calorimetry and oscillatory shear rheology. Consecutively, the shape memory and self-healing behaviour were investigated by a torsion procedure and tensile testing respectively. It was found that ionomer/crosslinked polycyclooctene blends of 70/30 wt% lead to polymers showing partial macroscopic healing and repeatable shape memory characteristics. The new polymer system shows both dual and triple shape memory behaviour and a near to 100% stiffness recovery after healing of crosscuts at standard ionomer healing conditions. Furthermore, the relation between terminal relaxation and self-healing in blends is shown. This study introduces a triple shape memory polymer with self-healing properties by a blending strategy thereby clearing the path for more durable materials based on shape memory properties.

In this work, we studied the cation occupancy of bimagnetic CoO/Co1−xZnxFe2O4 core/shell nanoparticles by means of X-ray absorption and Mossbauer spectroscopies, which provide element-sensitive information at the atomic scale. Our results indicate that, although the spinel ferrite forms a multi-grain shell, the Zn cations occupy solely tetrahedral sites, while the Co cations are mostly in the octahedral site. On the other hand, the Fe cations are distributed in both tetrahedral and octahedral sites for all concentrations. Also the results provide evidence for a Zn-deficient spinel with an excess of Co cations in the shell, whose origin is further rationalized in terms of the two-step synthesis process. In overall, this work gives a description of the cation occupancy in the core/shell nanoparticles and can serve as a guide to the interpretation of the magnetic properties of complex bimagnetic systems for future technological applications.

The macroscopic interfacial healing behaviour in a series of urea-urethane networks as function of the hydrogen bonds and disulphides content is presented. The polymers were prepared with different crosslinking densities but with the same amount of dynamic covalent bonds (disulphide linkages). Tensile and fracture measurements were adopted to evaluate the degree of recovery of the mechanical properties after damage. Healing kinetics and healing efficiencies were quantitatively determined as a function of network composition, healing temperature and contact time. Finally, the recovery of mechanical properties was correlated with the viscoelastic response of the networks through rheological measurements and time-temperature superposition principle (TTS). The application of the TTS approach on both fracture healing and DMTA and subsequent mathematical descriptive model led to a better understanding of the influence of polymer architecture and that of the amount of reversible groups on the healing process.

The use of micron sized nanoporous diatom algae exoskeletons for inhibitor storage and sustained corrosion protection of coated aluminium structures upon damage is presented. In this concept the algae exoskeleton allows local inhibitor loading, limits the interaction between the cerium and the epoxy/amine coating and allows for diffusion-controlled release of the inhibitor when needed. The inhibitor release and corrosion protection by loaded exoskeletons was evaluated by UV/Vis spectrometry, a home-built optical-electrochemical setup, and Raman spectroscopy. Although this concept has been proven for a cerium-epoxy-aluminium alloy system the main underlying principle can be extrapolated to other inhibitor-coating-metal systems.

The main aim of this work is to study the respective contribution of the hard and soft blocks of a metal-ligand containing block copolymer to the self-healing behavior. To this aim, different block copolymers containing terpyridine were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. These block copolymers consisted of polystyrene as the hard block, n-butyl acrylate (BA) as soft block and terpyridine units as the ligand moiety placed at different locations in the soft block. These block copolymers were complexed with manganese(II) chloride to introduce transient crosslinks and, thus, self-healing behavior. Homopolymers with the hard and soft block only were also synthesized and tested. A quasi-irreversible crosslinking, i.e. by using nickel(II) nitrate, was performed in order to study the dynamics of the permanently (strongly) crosslinked network. Rheological master curves were generated enabling the determination of the terminal flow in these networks and the reversibility of the supramolecular interactions. Additionally, the macroscopic scratch healing behavior and the molecular mobility of the polymer chains in these supramolecular networks were investigated. A kinetic study of the scratch healing was performed to determine the similarities in temperature dependence for rheological relaxations and macroscopic scratch healing. In our previous work, we have explored the effect of strength of the reversible metal-ligand interaction and the effect of changing the ratio of hard to soft block. This work goes further in separating the individual contributions of the hard and soft blocks as well as the reversible interactions and to reveal their relative importance in the complex phenomenon of scratch healing.

Hexagonal boron nitride is a 2D material whose single-layer allotrope has not been intensively studied despite being the substrate for graphene electronics. Its transparency and stronger interlayer adhesion with respect to graphene makes it difficult to work with, and few applications have been proposed. We have developed a transfer technique for this extra-adhesive material that does not require its visual localization, and fabricated mechanical resonators made out of chemical vapor-deposited single-layer hexagonal boron nitride. The suspended material was initially contaminated with polymer residues from the transfer, and the devices showed an unexpected tensioning when cooling them to 3 K. After cleaning in harsh environments with air at 450 °C and ozone, the temperature dependence changed with f 0 Q products reaching 2 × 1010 Hz at room temperature. This work paves the way to the realization of highly sensitive mechanical systems based on hexagonal boron nitride, which could be used as an alternative material to SiN for optomechanics experiments at room temperature. An improved transfer method allows easy placement of highly transparent and strongly adhesive hexagonal boron nitride on target substrates. A team led by Santiago J. Cartamil-Bueno at Delft University of Technology developed a technique that enables the transfer of large-area, single-layer hexagonal boron nitride films grown by chemical vapor deposition onto a substrate of choice, whilst not requiring optical visualization. Following an additional cleaning step, the atomically thin membranes were transferred onto circular microcavities patterned on a silicon oxide substrate, resulting in the formation of suspended drums. Cleaning in harsh environments using a mixture of air and ozone is instrumental to a substantial improvement in the quality factor of the drums, indicating that undesired contamination causes damping of the mechanical motion. These results show promise for the development of sensitive hexagonal boron nitride resonators.

Graphical abstract, Highlights • A 3D printed phantom was designed and fabricated to validate photoacoustic contrast agents. • Methylene blue was used as a contrast agent to validate the performance metrics of the phantom under the PA imaging system. • The signal inherent to different types of tubing was quantified. • India Ink and lipids were added to the media to simulate tissue absorption. • The signal at multiple distances from the laser focal point was measured., We report a new approach to preparing phantoms using 3D printing. This device supports plastic tubing containing the contrast agent and is immersed in a solution with absorption or scattering properties that mimic tissue. Up to 12 tubing samples could be placed in the device with sample-to-sample spacing as low as 0.3 mm and at a constant distance from the transducer (±0.16 mm), which is critical in validating photoacoustic contrast agents. We also studied different types of tubing and found that tubing with a larger outside diameter has more inherent signal. Both 40% India Ink and lipids in the immersion media modulated the signal. Finally, we created a depth phantom and found that signal decayed following a linear relationship (R2 = 0.997) with respect to distance from the focal point. We include computer-assisted drafting code the community can use to print this phantom or customized versions of this phantom.

Light sailing is the only existing in-space propulsion technology that could allow us to visit other star systems in a human lifespan. In order to best harness radiation pressure, light sails need to be highly reflective, lightweight and mechanically robust. This is traditionally achieved by the use of nanometer-thin reflective layers supported by a micrometer-thick substrate that endows them with the necessary sturdiness. This combination usually results in a sail mass that is too high to be efficiently used for extrasolar exploration. Here, we propose a potentially scalable sail design that combines a hollow substrate with an atomically-thin 2D material which, thanks to its ultimately low surface density, allows reducing the mass contribution of the substrate. To demonstrate the potential of such sails, we have studied the laser-induced displacement of graphene-on-copper sails in vacuum and in microgravity. In these conditions, 0.25 mg samples are accelerated by using lasers of different wavelengths (450 and 655 nm) and power ( 0.1 − 1 W). The measured thrust is one order of magnitude larger than the theoretical calculations for radiation pressure alone. This calls for further theoretical studies and increases the interest of graphene as light-sail material.

Oxides with proton conductivity have a great potential for applications in environmental energy technology. Despite the BaCe0.4Zr0.4Y0.2O3−δ (BCZY) perovskites being well-known proton conductors, it is a challenge to determine the optimal operating temperature range where the energy applications benefit most from this unique property. The protonic transport properties strongly depend on crystal structure and local distortions in the participating cation coordination sphere, according to related temperatures and gas feed. The transport and crystallographic properties of BCZY were simultaneously studied by impedance spectroscopy (IS) and synchrotron X-ray diffraction (S-XRD). A strong correlation between conductivity and the lattice parameter, corresponding in principle to a cubic symmetry, was observed, mainly between 400 and 700 °C. The protonic conductivity range was analyzed by the H/D isotopic effect on the impedance spectra, which helped to identify protonic conduction as the governing transport mechanism below 600 °C, while the transport via oxygen vacancies dominates above this temperature. In order to assess the real crystallographic structure, the simultaneous refinement of laboratory XRD and neutron diffraction (ND) patterns was performed. According to this, BCZY changes from rhombohedral symmetry below 400 °C to cubic at 600 °C in a second-order phase transition. Complementary quasielastic neutron scattering (QENS) enables us to determine a protonic jump length of 3.1 Å, which matches the O–O distances in the octahedral oxygen coordination sphere around the cations. These results support the protonic self-diffusion through proton hopping between intraoctahedral O sites as the main transport mechanism up to 600 °C., This work was supported by Agencia Nacional de Promocion de Ciencia y Tecnologia (ANPCyT) PICT-2016-2965 and PICT2014-1849, CONICET PIP-2015-0565, LNLS (Brazil), under proposals 20150099 and 20170278, and ILL (France) under proposal 7-03-168. L. Giebeler is grateful to the German Federal Ministry of Education and Research (BMBF) and the Argentinian Ministry of Science and Technology (MinCyT) for funding in the bilateral project DeFLeST (01DN14002). J. A. Alonso thanks the Spanish Ministry for Science, Innovation and Universities for funding the Project MAT2017-84496-R.

Recently, there has been growing interest in multi-principal element alloys for hydrogen storage. However, most of the papers published so far report compositions based only on transition metal elements, which limit the gravimetric storage capacities due to their densities. Since Mg is a low-density element promising for hydrogen storage, the study of Mg-containing multi-principal element compositions is opportune. In the present work, we report for the first time the structural characterization and hydrogen storage properties of the A2B type MgTiNbCr0.5Mn0.5Ni0.5 alloy and its derivative Mg0.68TiNbNi0.55 alloy. These Mg-containing multi-principal element alloys form major BCC phase (W-type, Im 3 ¯ m) and major FCC hydride (MH2 with CaF2-type structure) when synthesized by mechanical alloying (MA) and reactive milling (RM), respectively. Hydrogen is desorbed from both RM samples in two steps, with some overlap, from different hydrides formed during synthesis. The microstructure of the Mg0.68TiNbNi0.55 composition is more homogeneous (less secondary phases), but both alloys present a total gravimetric capacity of around 1.6 wt% H2.

International audience; The mean oxidation state of cationic elements in Pr2NiO4+δ was studied using XANES measurements versus temperature in air. Unexpectedly, praseodymium is solely found as Pr3+ while Pr4+ was also foreseeable. Pr3+ cation is well accommodated in the large rare-earth site with the nine-fold coordination in this K2NiF4 – T-type structure; conversely, the small size of the Pr4+ cation seems not compatible with this site. Moreover, XANES measurements show a progressive decrease of the mean oxidation state of nickel ions when the temperature increases. It is directly correlated to the decrease of the oxygen over-stoichiometry of the material evidenced by TGA measurements.

Different block copolymers containing terpyridine were synthesized applying the reversible addition–fragmentation chain transfer (RAFT) polymerization. The block copolymers contain polystyrene as hard block, and the soft block consists of n-butyl acrylate (BA) as well as terpyridine units as ligand. These block copolymers were further cross-linked with several metal salts in order to tune the self-healing behavior. Metallopolymers cross-linked with manganese(II) chloride featured the best self-healing behavior. Furthermore, a two-step mechanism behind the self-healing process of these metallopolymers could be attributed to each block of the copolymer and was studied extensively. In addition, rheological parameters were determined and correlated with the other results.

A new polymeric material utilizing a highly efficient as well as reversible thiol-ene click reaction is presented. For this purpose, a trithiol is reacted with a bisbenzylcyanoacetamide derivative resulting in the formation of a dynamic polymer network. The self-healing ability of this novel material is tested by scratch healing experiments. Healing is found to take place from 60 °C onward. The underlying healing mechanism is studied in detail using temperature-dependent Raman spectroscopy confirming the reversible opening of the thiol-ene adducts. Additionally, the thermal and mechanical properties are investigated by differential scanning calorimetry, thermogravimetric analysis, and rheological measurements proving the network formation as well as its reversibility during the thermal treatment.

In the last years several intrinsic and extrinsic healing coatings have been presented in the literature. While extrinsic coatings have attracted more attention when dealing with electrochemical characterization techniques, protective intrinsic healing coatings have mainly been analyzed by traditional electrochemical impedance spectroscopy (EIS). In this article we introduce the potential use of the AC/DC/AC accelerated electrochemical protocol as a suitable tool for the fast evaluation of the goodness of the polymer-polymer interface (i.e. scar) in a healed scratch. For the purpose we employed a hybrid healable dual network coating containing disulfide linkages as the responsible reversible groups for the necessary local mobility and subsequent scratch interface sealing. The results obtained show the high discriminating power of AC/DC/AC of the level of interface sealing at the scratch in much faster times than traditional EIS.

An in-situ hyphenated optical and electrochemical method for the real-time study of corrosion and corrosion inhibition processes is presented and validated for the case of AA2024-T3 exposed to two NaCl concentrations and six inhibitors. During testing, 5 μm resolution optical images of the exposed surface are obtained in parallel to electrochemical impedance measurements using a home-made 3D printed electrochemical cell. This method allowed obtaining both optical and electrochemical information of the studied surface with high time correlation. A data treatment analysis of the optical images was established thereby allowing the identification and quantification of corrosion-features related to intermetallic corrosion (e.g. trenching and meta-stable pitting) and co-operative corrosion (e.g. corrosion-rings, domes and surface-oxides) on a spatiotemporal scale, generally only observed through the use of ex-situ methods such as SEM. In addition, the study of the long-term corrosion inhibition of six inhibitors at concentrations ranging from 10−3 M to 10−6 M allowed quantifying inhibition kinetics as well as identifying different inhibitor and concentration dependent mechanisms (e.g. Cerium and DEDTC vs. Lithium) and decreasing incongruences between impedance and inhibition behaviour (e.g. DMTD). As a result, the use of quantifiable in-situ optical analysis is confirmed as a powerful tool to better interpret electrochemical signals or monitor electrochemical-dependent surface phenomena.

Single-phased La0.6Sr0.4Co1-yFeyO3-d (y = 0.2, 0.5, 0.8) nanorods exhibiting the rhombohedral perovskite-type phase were synthesized by a pore-wetting technique. We studied their chemical composition, crystal and electronic structures, morphology and hyperfine properties as a function of the Co/Fe content of the samples. Our results demonstrate that Co cations exhibit a slightly lower oxidation state than Fe ones, resulting in a higher oxygen non-stoichiometry d for Co-rich samples. In addition, the values of d determined in this work for nanostructured samples are much higher than those reported in the literature for bulk materials. This can be attributed to the high degree of defects in nanomaterials and is probably one important factor in the high electrochemical performance for the oxygen reduction reaction of nanostructured La0.6Sr0.4Co1-yFeyO3-d IT-SOFC cathodes, which have been reported in a previous work. Keywords: electrode materials; nanostructured materials; X-ray diffraction; NEXAFS; M\"ossbauer spectroscopy, Comment: 18 pages, 8 figures, accepted for publication

In this work, a new concept is introduced for active corrosion protection at damaged sites aiming at overcoming existing limitations of currently proposed strategies based on dispersed inhibitor-loaded nanocontainers in coatings. The underlying principle is based on the formation of low-density and/or humidity responsive interconnected paths of inhibitor in the coating, what is called inhibiting nanonetworks. Such an approach allows for (on-demand) long-term local supply of corrosion inhibitor at the damage site. For the proof-of-concept, water responsive inhibiting nanonetworks based on polyvinyl alcohol and two known efficient corrosion inhibitors for AA2024-T3 (cerium chloride and lithium carbonate) using electrospinning are developed. The inhibiting nanonetworks are obtained by subsequently embedding the electrospun fiber mats in thermoset epoxy coatings applied on AA2024-T3. The coated panels are scratched and exposed to NaCl solutions for a month while continuously monitoring the protective properties electrochemically and optically in a hyphenated setup. The effect of the corrosion inhibitor type and the partial crosslinking of the mat on release and protection are analyzed. Protection levels at relatively big damaged sites are obtained for at least a month immersion thereby proving the benefits of high inhibitor quantities continuously released in time.

A series of 18 ruthenium(II) polypyridyl complexes were synthesized and evaluated under electrochemically oxidative conditions, which generates the Ru(III) oxidation state and mimics the harsh conditions experienced during the kinetically limited regime that can occur in dye-sensitized solar cells (DSSCs) and dye-sensitized photo-electrosynthesis cells, to further develop fundamental insights into the factors governing molecular sensitizer surface stability in aqueous 0.1 M HClO4. Both desorption and oxidatively induced ligand substitution were observed on planar fluorine-doped tin oxide (FTO) electrodes, with a dependence on the E1/2 Ru(III/II) redox potential dictating the comparative ratios of the processes. Complexes such as RuP4OMe (E1/2 = 0.91 vs Ag/AgCl) displayed virtually only desorption, while complexes such as RuPbpz (E1/2 > 1.62 V vs Ag/AgCl) displayed only chemical decomposition. Comparing isomers of 4,4′- and 5,5′-disubstituted-2,2′-bipyridine ancillary ligands, a dramatic increase in the ra...

We use a scalable optical technique to characterize more than 21000 circular nanomechanical devices made out of suspended single- and double-layer graphene on cavities with different diameters ($D$) and depths ($g$). To maximize the contrast between suspended and broken membranes we used a model for selecting the optimal color filter. The method enables parallel and automatized image processing for yield statistics. We find the survival probability to be correlated to a structural mechanics scaling parameter given by $D^4/g^3$. Moreover, we extract a median adhesion energy of $\Gamma =$ 0.9 J/m$^2$ between the membrane and the native SiO$_2$ at the bottom of the cavities., Comment: 7 pages, 5 figures

In the current paper the corrosion inhibition synergy between Ce3+ loaded NaY-zeolite (NaY-Ce) and 2-Mercaptobenzothiazole (MBT) loaded Zn-Al layered double hydroxide (LDH-MBT) containers is presented. Solutions and water-borne epoxy coatings containing different ratios of the two loaded carriers were prepared and their protection of AA2024-T3 and damaged coatings characterized using global and local electrochemical techniques and other complementary tools. The coatings containing container-combinations showed exceptional corrosion protection over a broad range of NaY-Ce:LDH-MBT weight ratios, with 90:10 being the optimal. The current work landmarks the need for synergetic inhibiting studies devoted to carrier-inhibitor systems in coatings.

We report a novel yet simple 3D-printed tubing holder for characterizing photoacoustic contrast agents. This device supports up to 12 plastic tubing with sample-to-sample spacing as low as 0.3 mm and provides a consistent distance (± 0.12 mm) between the tubing and the transducer, which is critical for validating photoacoustic contrast agents. An immersion media containing both 40% India ink and lipid that mimics tissue scattered the incident irradiation. We further studied different types of tubing and distance between tubing and transducer. Statistical analysis shows that tubing with a larger outside diameter has more inherent signal, and the signal decayed following a linear relationship (R2=0.997) with respect to distance from the laser focal point. We finally provide a computer-assisted drafting code for the community to customize and print their own phantoms.

Recent demands for polymers with autonomous self-healing properties are being constantly raised due to the need for high-performance and reliable materials. So far, the advances in this field are limited to the production of self-healing materials requiring a high energy input. Therefore there is an urgent need to develop self-healing polymer systems, in which healing can be easily and specifically induced by external stimuli for economical and viable applications. In the current work we demonstrate, for the first time to our knowledge, the possibility to heal local macroscopic damage by a confined temperature increase arising from the Joule effect. The damage healing is promoted by the resistance to an electrical current at the crack tip. This new concept is studied on thermo-reversible and electrically conductive poly(ester-urethane)/carbon nanotube nanocomposites derived from thermo-reversible Diels–Alder reactions between furfuryl- and maleimide-functionalized poly(e-caprolactone) (PCL)-based precursors. Electrically conductive materials are then obtained after incorporating multi-walled carbon nanotubes into the thermo-reversible networks using reactive extrusion. Under mild electrical conditions, temperature in the range of the retro-Diels–Alder reaction can be obtained near the damaged site. The obtained results reveal the potential of this new approach for healing materials locally while maintaining the overall material properties.

Two sulfonated aramids, poly(2,2′-disulfonylbenzidine terephthalamide) (PBDT) and poly(2,2′-disulfonylbenzidine isophthalamide) (PBDI), were synthesized with the aim to explore their unique morphology for proton exchange membrane applications. Due to the different polymer structures, PBDT forms a nematic liquid crystal, whereas PBDI is isotropic. Both polymers show excellent thermal stabilities ( T d 5 % >400 °C), high storage moduli (E′=3–15 GPa) and crosslinked films are flexible and easy to handle. Pulsed-field-gradient NMR diffusometry reveals that the in-plane water diffusion in the nematic PBDT membrane is as high as 3.3×10−10 m2/s, whereas the diffusion in amorphous PBDI is only 2.5×10−10 m2/s. Whereas neat and crosslinked PBDI shows isotropic diffusion, neat PBDT shows a high diffusion anisotropy (D∥/D⊥=3.0), which increases as a function of crosslink density (D∥/D⊥=4.6 at 80% crosslinking). This diffusion anisotropy is substantially higher than that typically observed for low molecular weight liquid crystals and for oriented polymeric conductors such as Nafion® (D∥/D⊥~2.0). The nematic order in the PBDT membrane also promotes directed ionic conductivity, i.e. Na+ conductivity in PBDT is 2.24×10−2 S/cm and 1.67×10−2 S/cm for PBDI, respectively. We propose that the rigid-rod PBDT chains form nano-scale hydrophilic channels, which act as pathways for transporting water molecules and ions.

In this work the combination of ellipsometric porosimetry (EP) and electrochemical impedance spectroscopy (EIS) is extensively addressed in order to characterize the nano-porosity and further elucidate its influence on the water permeation properties of plasma enhanced-CVD SiO2 layers. Pores with diameter in the range of 0.27–0.6 nm are studied by adopting a multi-solvent/multi-ion approach, with EP and EIS, respectively. This combined study has brought to conclude that open pores larger than 0.42 nm are responsible for WVTR values in the range of 10−3-10−5 gm−2 day−1, while pores with diameter between 0.42–0.27 nm were found to drive the transition to excellent moisture barrier layers (10−6 gm−2 day−1). Moreover, it is shown that EIS is capable of detecting macro-scale defects, next to nano-porosity, being thus a powerful tool for the analysis of moisture barrier layers.

The aim of this work is to contribute to the understanding of the relationship between the timescales of molecular processes in ionomers and that of macroscale autonomous healing. For this purpose, poly(butyl acrylate-co-acrylic acid) model ionomers with varying fractions of cobalt counter ions were used. Three temperature dependent timescales were quantified and linked: (i) the terminal relaxation time (td) as determined by creep relaxation experiments; (ii) the supramolecular relaxation timescale (t) as determined by frequency sweeps in oscillatory shear rheology; and (iii) the macroscopic healing timescale (theal) as obtained by quantifying the time for full interfacial strength recovery for two ionomer surfaces brought in contact. Using the temperature dependent values of td, t, and theal, the activation energies of the ionic cluster formation, the flow of the polymer backbone, and the interfacial recovery respectively, were calculated. It was found that the kinetics of healing closely follows the timescales of network and cluster formation.

Pulsed laser deposition (PLD) was used to grow ZnO thin films on corning glass and silicon substrates at different oxygen pressures (1 y 10 mTorr). The structural analysis of the films was performed by X-ray diffraction and pulsed laser photoacoustic (PLPA) techniques. Both methods were employed to identify the minority zinc blende phase in the films. The relative difference between the structural changes detected in the films with the temperature increases was statistically analyzed. It was found that regardless of the substrate and the oxygen pressure used for the growth, the films exhibit a phase transition at 310 °C, which corresponds to the transformation of zinc blende structure to hexagonal wurtzite. The results demonstrate that the zinc blende phase in the films is present not only on cubic substrates but also on glass, and confirm that PLPA technique is a very sensitive method for the detection of minority phase changes.

The utilization of dynamic covalent and noncovalent bonds in polymeric materials offers the possibility to regenerate mechanical damage, inflicted on the material, and is therefore of great interest in the field of self-healing materials. For the design of a new class of self-healing materials, methacrylate containing copolymers with acylhydrazones as reversible covalent crosslinkers are utilized. The self-healing polymer networks are obtained by a bulk polymerization of an acylhydrazone crosslinker and commercially available methacrylates as comonomers to fine-tune the Tg of the systems. The influence of the amount of acylhydrazone crosslinker and the self-healing behavior of the polymers is studied in detail. Furthermore, the basic healing mechanism and the corresponding mechanical properties are analyzed.

In this work we report the effect of the hard block dianhydride structure on the overall properties of partially biobased semiaromatic polyimides. For the study, four polyimides were synthesized using aliphatic fatty dimer diamine (DD1) as the soft block and four different commercially available aromatic dianhydrides as the hard block: 4,4¿-(4,4¿-isopropylidenediphenoxy) bis(phthalic anhydride) (BPADA), 4,4¿-oxidiphthalic anhydride (ODPA), 4,4¿-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA), and 3,3¿,4,4¿-biphenyltetracarboxylic dianhydride (BPDA). The polymers synthesized were fully organo-soluble thermoplastic branched polyimides with glass transition temperatures close to room temperature. The detailed analysis took into account several aspects of the dianhydrides structure (planarity, rigidity, bridging group between the phtalimides, and electronic properties) and related them to the results obtained by differential scanning calorimetry, rheology, fluorescence and broadband dielectric spectroscopy. Moreover, the effects of physical parameters (crystallization and electronic interactions) on the relaxation behavior are discussed. Despite the presence of the bulky branched soft block given by the dimer diamine, all polyimides showed intermolecular charge transfer complexes, whose extent depends on the electronic properties of the dianhydride hard block. Furthermore, the results showed that polyimides containing flexible and bulky hard blocks turned out fully amorphous while the more rigid dianhydride (BPDA) led to a nanophase separated morphology with low degree of crystallinity resulting in constrained segmental relaxation with high effect on its mechanical response with the annealing time. This work represents the first detailed report on the development and characterization of polyimides based on a biobased fatty dimer diamine. The results highlight the potential of polymer property design by controlled engineering of the aromatic dianhydride blocks., We thank Professor Sybrand van der Zwaag for his continued interest in the work and valuable comments on the manuscript during its construction. The authors acknowledge the financial support from the Dutch IOP program on self-healing materials under Grant No. IOP-SHM-012036. We acknowledge our industrial partner Croda Nederland BV, especially the sustained support and valuable discussions with Dr. Angela Smits (Croda). Many thanks to Dr. Brian Richard Pauw (Bundesanstalt für Materialforschung und−prüfung, Berlin) for performing the SAXS measurements

This review outlines latest developments in the field of self-healing rubbers and elastomers, analyzing their potential application to natural rubber (NR). Different validated healing concepts are presented and the possibilities of applying them to NR are discussed. Research in this field should aim at modifying the chemical structure of NR as to enhance physical or chemical reversible interactions either intermolecular or intramolecular. The realization of better mechanical properties at relevant working conditions and with milder healing conditions remains a challenge for all self-healing rubbers. This overview should be seen as setting the conceptual framework for new developments with a more clearly defined industrial focus., M. Hernández thanks the European Commission for a Marie Curie Fellowship (PIEF-GA-2013- 623379) and the Spanish Ministry of Economy and Competitiveness for a research grant (MAT2015- 73392-JIN