Oxygen permeation measurements are performed on dense samples of CaTi0.85Fe0.15O3-δ, CaTi0.75Fe0.15Mg0.05O3-δ and CaTi0.75Fe0.15Mn0.10O3-δ in combination with density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) in order to assess Mg and Mn as dopants for improving the O2 permeability of CaTi1-xFexO3-δ based oxygen separation membranes. The oxygen permeation measurements were carried out at temperatures ranging between 700-1000 °C with feed side oxygen partial pressures between 0.01-1 bar. The O2 permeability was experimentally found to be highest for the Mn doped sample over the whole temperature range, reaching 4.2×10 -3 ml min -1 cm -1 at 900 °C and 0.21 bar O2 in the feed which corresponds to a 40% increase over the Fe-doped sample and similar to reported values for x=0.2. While the O2 permeability of the Mg doped sample was also higher than the Fe-doped sample, it approached that of the Fe-doped sample above 900 °C. According to the DFT calculations, Mn introduces electronic states within the band gap and will predominately exist in the effectively negative charge state, as indicated by XPS measurements. Mn may therefore improve the ionic and electronic conductivity of CTF based membranes. The results are discussed in terms of the limiting species for ambipolar transport and O2 permeability, i.e., oxygen vacancies and electronic charge carriers.

The three-dimensional structure of silica diatom frustules offers a great potential as nanoporous material for several nanotechnological applications, but the starting point for these applications is the ability to obtain clean frustules with sufficient mechanical strength and intact structure. Here, frustules from the diatoms Coscinodiscus centralis Ehrenberg and C. wailesii Gran et Angst are characterized with respect to their structural integrity, content of residual organic biomaterial and their mechanical properties after two cleaning methods using either hydrogen peroxide as oxidizing agent or a combination of a surfactant (sodium dodecyl sulphate) and a complexing agent. Fluorescence microscopy and energy dispersive spectroscopy (SEM/EDS) analysis revealed clear differences regarding the amount of organic residual within the frustules depending on the cleaning process, with little organic material left after the oxidizing method. This method, however, induced a partial cracking of the frustules suggesting an embrittlement due to the cleaning. Nanoindentation confirmed this and showed that the oxidizing method resulted in more brittle frustules compared to the surfactant/complexing method. More efficient cleaning of organic biomaterial may result in more fragile frustules, and the choice of cleaning method must be based on the planned application.

Transparent and homogeneous hybrid aminopropyl silane-based coatings on steel were prepared by the sol-gel method using hydrolyzed -APS as a precursor. The coatings were fabricated by dip coating, and the effect of pH, water/silane ratio and solvent/silane ratio during the coating process was investigated with respect to thermal stability, coating thickness, roughness, contact angle and abrasion resistance. The thickness of the coatings was controlled by the preparation conditions as well as the viscosity of the sols and varied between 0.17 and 4.1 µm. The coatings were in general smooth and the roughness in the order of a few nm. The coatings possessed hydrophilic character with contact angles of water from 65 to 80 °, while organic pentadecane wetted the coatings. The abrasion resistance improved with decreasing pH of the water used during hydrolysis of the silane. The abrasion resistant properties of the coatings were characterized with respect to delamination and smearing. Thicker coatings were delaminated while thinner coatings were smeared and displayed lubricating properties. The coatings were thermally stable up to 350 °C, and also displayed a low pore volume and a low surface area.

No abstract

A non-nucleophilic electrolyte for rechargeable Mgion batteries is developed by the reaction of magnesium bis(diisopropyl)amide and 1-ethyl-3-methylimidazolium tetrachloroaluminate ionic liquid in tetrahydrofuran solvent. The electrolyte shows excellent reversibility and Coulombic efficiency for the Mg deposition/stripping process at room temperature on several working electrodes such as Mo, graphite, and stainless steel. Additionally, the electrolyte shows high anodic stability with Mo as the cathode current collector, with no corrosion detected even after 48 h at 4.5 V versus (Mg/Mg 2+ ). An exceptional cyclability in a full cell configuration using a Chevrel phase Mo 6 S 8 cathode is achieved with a capacity retention of more than 80% for over 300 cycles at a 15 mA g −1 specific current, making this electrolyte an excellent candidate for rechargeable Mg-ion batteries.