Chemically engineered alloy anode enabling fully reversible conversion reaction: Design of C-Sn bonded aerofilm anode

Designing as freestanding electrodes using conversion-type materials is a promising strategy enabling high energy density of batteries because that can minimize the consumption of inactive materials in combination with a...

Sodium-Vanadium Bronze Na9V14O35: An Electrode Material for Na-Ion Batteries

Na9V14O35 (η-NaxV2O5) has been synthesized via solid-state reaction in an evacuated sealed silica ampoule and tested as electroactive material for Na-ion batteries. According to powder X-ray diffraction, electron diffraction and atomic resolution scanning transmission electron microscopy, Na9V14O35 adopts a monoclinic structure consisting of layers of corner- and edge-sharing VO5 tetragonal pyramids and VO4 tetrahedra with Na cations positioned between the layers, and can be considered as sodium vanadium(IV,V) oxovanadate Na9V104.1+O19(V5+O4)4. Behavior of Na9V14O35 as a positive and negative electrode in Na half-cells was investigated by galvanostatic cycling against metallic Na, synchrotron powder X-ray diffraction and electron energy loss spectroscopy. Being charged to 4.6 V vs. Na+/Na, almost 3 Na can be extracted per Na9V14O35 formula, resulting in electrochemical capacity of ~60 mAh g−1. Upon discharge below 1 V, Na9V14O35 uptakes sodium up to Na:V = 1:1 ratio that is accompanied by drastic elongation of the separation between the layers of the VO4 tetrahedra and VO5 tetragonal pyramids and volume increase of about 31%. Below 0.25 V, the ordered layered Na9V14O35 structure transforms into a rock-salt type disordered structure and ultimately into amorphous products of a conversion reaction at 0.1 V. The discharge capacity of 490 mAh g−1 delivered at first cycle due to the conversion reaction fades with the number of charge-discharge cycles.

Spraying and Mixing Characteristics of Urea in a Static Mixer Applied Marine SCR System

The most effective de-NOx technology in marine diesel applications is the urea-based selective catalytic reduction (SCR) system. The urea-SCR system works by injecting a urea solution into exhaust gas and converting this to NH3 and CO2. The injection, mixing, and NH3 conversion reaction behavior of the urea-water solution all have a decisive effect on the performance of the system. To improve de-NOx efficiency, it is important to provide enough time and distance for NH3 conversion and uniform distribution prior to the solution entering the catalyst. In this study, therefore, the characteristics of gas flow, NH3 conversion, and its distribution are investigated with a static mixer by means of numerical methods, providing a special advantage to ship manufacturing companies through the optimization of the urea-SCR system. The results show that the inclusion of the mixer induces strong turbulence and promotes the NH3 conversion reaction across a wider region compared to the case without the mixer. The mean temperature is 10 °C lower due to the activated endothermic urea-NH3 conversion reaction and the NH3 concentration is 80 PPM higher at 1D than those without the mixer. Moreover, the uniformity of NH3 distribution improved by 25% with the mixer, meaning that the de-NOx reaction can take place across all aspects of the catalyst thus maximizing performance. In other words, ship manufacturing companies have degrees of freedom in designing post-processing solutions for emissions by minimizing the use of the reduction agent or the size of the SCR system.