Isocyanate-Terminated Poly(ethylene Oxide)

Isocyanate-terminated polyethylene oxide (PEO) was prepared by reaction of hydroxyl-terminated PEO of different molecular weights and toluene diisocyanate (TDI), at a molar ratio of 1:2. Reaction was carried out with and without catalyst (dibutyltin dilaurate). When catalyst was used, some chain extension accompanied the endcapping reaction. When endcapping reaction was carried out without catalyst, chain extension was minimal as determined from endgroup analysis and viscosity measurements. It was also found that secondary reactions of the terminal isocyanate groups led to further increase in solution viscosity after completion of the endcapping reaction.     

Liquid‐Free Lithium–Oxygen Batteries

Non‐aqueous lithium–oxygen batteries are considered as most advanced power sources, albeit they are facing numerous challenges concerning almost each cell component. Herein, we diverge from the conventional and traditional liquid‐based non‐aqueous Li–O₂ batteries to a Li–O₂ system based on a solid polymer electrolyte (SPE‐) and operated at a temperature higher than the melting point of the polymer electrolyte, where useful and most applicable conductivity values are easily achieved. The proposed SPE‐based Li‐O₂ cell is compared to Li–O₂ cells based on ethylene glycol dimethyl ether (glyme) through potentiodynamic and galvanostatic studies, showing a higher cell discharge voltage by 80 mV and most significantly, a charge voltage lower by 400 mV. The solid‐state battery demonstrated a comparable discharge‐specific capacity to glyme‐based Li–O₂ cells when discharged at the same current density. The results shown here demonstrate that the safer PEO‐based Li–O₂ battery is highly advantageous and can potentially replace the contingent of liquid‐based cells upon further investigation.     

A Pd/C‐CeO2 Anode Catalyst for High‐Performance Platinum‐Free Anion Exchange Membrane Fuel Cells

One of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM‐FCs). The anion exchange membrane fuel cell (AEM‐FC) has long been proposed as a solution as non‐Pt metals may be employed. Despite this, few examples of Pt‐free AEM‐FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt‐free AEM‐FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt‐free AEM‐FC that employs a mixed carbon‐CeO₂ supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM‐FC tests run on dry H₂ and pure air show peak power densities of more than 500 mW cm^?2.     

Conditions for practicing compressive Fresnel holography

Recent works have applied diffraction-based wave propagation for compressive imaging applications. In this Letter, we derive the theoretical bounds on the performance of compressive imaging systems based on Fresnel wave propagation, and we show that it is related to the imaging sensor's physical attributes, illumination wavelength, and working distance.     

Spatial periodic forcing can displace patterns it is intended to control

Spatial periodic forcing of pattern-forming systems is an important, but lightly studied, method of controlling patterns. It can be used to control the amplitude and wave number of one-dimensional periodic patterns, to stabilize unstable patterns, and to induce them below instability onset. We show that, although in one spatial dimension the forcing acts to reinforce the patterns, in two dimensions it acts to destabilize or displace them by inducing two-dimensional rectangular and oblique patterns.