Characterisation tools development for PEM electrolysers

Electrochemical impedance spectroscopy (EIS), current interrupt (CI) and current mapping (CM) were investigated as in-situ characterisation tools for PEM electrolysers. A 25 cm² cell with titanium anode and carbon cathode plates were utilised in this study. A commercial MEA consisting of 1 mg IrO₂/cm² on the anode and 0.3 mg Pt/cm² on the cathode was used. The electrocatalyst was deposited on Nafion^® membranes. The electrochemical losses in a PEM electrolyser namely: activation, ohmic and mass transfer losses were identified using EIS and CI and both the advantages and disadvantages of the methods were discussed. The current distribution over the membrane electrode assembly (MEA) at different current densities was measured using the current mapping method. It is also shown that under the given experimental conditions the current density decreases along the serpentine flow field.     

Growth and characterization of non-c-axis-oriented SrBi2Ta2O9 epitaxial thin films on Si(100) substrates with SrRuO3 bottom electrodes

Abstract

We have successfully grown non-c-axis-oriented epitaxial ferroelectric SrBi₂Ta₂O₉ (SBT) films with (116) and (103) orientations on Si(100) substrates using epitaxial (110)- and (111)-oriented SrRuO₃ (SRO) bottom electrodes, respectively. The SRO orientations have been induced by coating the Si(100) substrates with epitaxial YSZ(100) and MgO(111)/ YSZ(100) buffer layers, respectively. All films were sequentially grown by pulsed laser deposition. Specific in-plane orientations of the epitaxial SBT films were found, which are in turn determined by specific in-plane orientations of the epitaxial SRO bottom electrodes. These include a diagonal rectangle-on-cube epitaxy of SRO(110) on YSZ(100) and a triangle-on-triangle epitaxy of SRO(111) on MgO(111).     

Structure and crystallization kinetics of a Cu50Zr45Ti5 glassy alloy

The crystallization kinetics and structure changes in a melt-spun Cu₅₀Zr₄₅Ti₅ glassy alloy on heating were investigated by X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and differential isothermal calorimetry. The glassy phase in the Cu₅₀Zr₄₅Ti₅ alloy was crystallized forming Cu₁₀Zr₇ and CuZr₂ phases upon thermal annealing. The activation energy for crystallization obtained by the Arrhenius equation was 435 kJ/mol. The crystallization process took place by nucleation and growth mechanism, and an Avrami exponent of about 3.3 may indicate a three-dimensional interface-controlled growth of nuclei with a decreasing nucleation rate.     

Fluorescent dye encapsulated ZnO particles with cell-specific toxicity for potential use in biomedical applications

Fluorescein isothiocyanate (FITC)-encapsulated SiO₂ core-shell particles with a nanoscale ZnO finishing layer have been synthesized for the first time as multifunctional “smart” nanostructures. Detailed characterization studies confirmed the formation of an outer ZnO layer on the SiO₂–FITC core. These ~200 nm sized particles showed promise toward cell imaging and cellular uptake studies using the bacterium Escherichia coli and Jurkat cancer cells, respectively. The FITC encapsulated ZnO particles demonstrated excellent selectivity in preferentially killing Jurkat cancer cells with minimal toxicity to normal primary immune cells (18% and 75% viability remaining, respectively, after exposure to 60 μg/ml) and inhibited the growth of both gram-positive and gram-negative bacteria at concentrations ≥250–500 μg/ml (for Staphylococcus aureus and Escherichia coli, respectively). These results indicate that the novel FITC encapsulated multifunctional particles with nanoscale ZnO surface layer can be used as smart nanostructures for particle tracking, cell imaging, antibacterial treatments and cancer therapy.     

Photorhabdus luminescens TccC3 Toxin Targets the Dynamic Population of F-Actin and Impairs Cell Cortex Integrity

Due to its essential role in cellular processes, actin is a common target for bacterial toxins. One such toxin, TccC3, is an effector domain of the ABC-toxin produced by entomopathogenic bacteria of Photorhabdus spp. Unlike other actin-targeting toxins, TccC3 uniquely ADP-ribosylates actin at Thr-148, resulting in the formation of actin aggregates and inhibition of phagocytosis. It has been shown that the fully modified F-actin is resistant to depolymerization by cofilin and gelsolin, but their effects on partially modified actin were not explored. We found that only F-actin unprotected by tropomyosin is the physiological TccC3 substrate. Yet, ADP-ribosylated G-actin can be produced upon cofilin-accelerated F-actin depolymerization, which was only mildly inhibited in partially modified actin. The affinity of TccC3-ADP-ribosylated G-actin for profilin and thymosin-β4 was weakened moderately but sufficiently to potentiate spontaneous polymerization in their presence. Interestingly, the Arp2/3-mediated nucleation was also potentiated by T148-ADP-ribosylation. Notably, even partially modified actin showed reduced bundling by plastins and α-actinin. In agreement with the role of these and other tandem calponin-homology domain actin organizers in the assembly of the cortical actin network, TccC3 induced intense membrane blebbing in cultured cells. Overall, our data suggest that TccC3 imposes a complex action on the cytoskeleton by affecting F-actin nucleation, recycling, and interaction with actin-binding proteins involved in the integration of actin filaments with each other and cellular elements.     

Hydrogen Storage in Carbon and Oxygen Co-Doped Porous Boron Nitrides

Fuel cell vehicles powered by hydrogen are particularly attractive and competitive among rapidly developing new energy-driven automobiles. One critical problem for this type of vehicles is the high cost for hydrogen storage due to the lack of efficient and low-pressure hydrogen storage technologies. In the frame of development of hydrogen physisorption-relied materials, attention has mostly been paid to the textural designs of porous materials, including specific surface area, pore volume, and pore size. However, based on the hydrogen physisorption mechanism, hydrogen adsorption energy on a material surface is another key factor with regard to hydrogen uptake capacity. Herein, solid experimental evidences are provided and it is also proven that the chemical states of porous boron nitride (BN) materials remarkably affect their hydrogen adsorption performances. The developed carbon and oxygen co-doped BN microsponges exhibit the hydrogen uptake capacity per specific surface area of 2.5–4.7 times larger than those of undoped BN structures. These results show the importance of chemical state modulations on the future designs of high-performance hydrogen adsorbents based on physisorption approaches.     

Densely Interconnected Porous BN Frameworks for Multifunctional and Isotropically Thermoconductive Polymer Composites

Ideal materials for modern electronics packaging should be highly thermoconductive. This may be achieved through designing multifunctional polymer composites. Such composites may generally be achieved via effective embedment of functional inorganic fillers into desirable polymeric bodies. Herein, two types of high‐performance 3D h‐BN porous frameworks (3D‐BN), namely, h‐BN nanorod‐assembled networks and nanosheet‐interconnected frameworks, are successfully created via an in situ carbothermal reduction chemical vapor deposition substitution reaction using carbon‐based nanorod‐interconnected networks as templates. These 3D‐BN porous materials with densely interlinked frameworks, excellent mechanical robustness and integrity, highly isotropous and multiple heat transfer paths, enable reliable fabrications of diverse 3D‐BN/polymer porous composites. The composites exhibit combinatorial multifunctional properties, such as excellent mechanical strength, light weight, ultralow coefficient of thermal expansion, highly isotropic thermal conductivities (≈26–51 multiples of pristine polymers), relatively low dielectric constants and super‐low dielectric losses, and high resistance to softening at elevated temperatures. In addition, the regarded 3D‐BN frameworks are easily recycled from their polymer composites, and may be reliably reutilized for multifunctional reuse. Thus, these materials should be valuable for new‐era advanced electronic packaging and related applications.