Development of Novel Nanomaterials for Lithium-Air and Sodium-Air Batteries

Lithium-air and sodium-air batteries are promising energy storage systems for future smart grids and electric vehicles due to their extremely high theoretical energy densities. However, electrode material development and architecture design for cathode as well as the battery cycleability are big challenges for these batteries. This research aims at developing various novel nanomaterials with desired morphology and structure as cathode materials for lithium-air and sodium-air batteries. For lithium-air batteries, various carbon nanostructured cathodes were developed. They include: (1) Carbon black nanoparticles were treated under ammonia and carbon dioxide/hydrogen atmospheres and the surface area, porosity, defects, nitrogen-doping, and functional groups were modulated. These parameters for battery performance were investigated and it was found that the surface area of mesopores rather than others played an important role for the discharge capacity due to the passivation effect of discharge products. (2) One-dimensional (1D) nitrogen-doped carbon nanotubes (N-CNTs) electrode showed 50% higher of discharge capacity and better electrocatalytic activity for discharge product decomposition than pristine carbon nanotubes (CNTs) electrode. (3) Two-dimensional (2D) graphene nanosheets (GNSs) electrode delivered extremely high discharge capacity compared to porous carbon blacks due to the ideal porosity which increased the electrolyte wetting and oxygen diffusion, improving the efficiency of reactions. (4) Nitrogen-doped graphene nanosheets (N-GNSs) exhibited 1.5 times higher of electrocatalytic activity for oxygen reduction reaction than GNSs, further improved 40% of the discharge capacity. In addition, the morphology of discharge products was changed due to the defects and functional groups introduced by nitrogen doping. (5) The correlation between discharge product morphology and battery performance for sulphur-doped GNSs was studied and it was found that the discharge product contained structural defects such as oxygen and/or lithium vacancies resulting in different charge performance. In terms of exploring catalysts which have potential for improving battery cycleability, a facile rapid microwave-assisted hydrothermal method was developed and it was shown that the morphology and crystallinity of MnO2 were easily controlled by adjusting the reaction parameters. For sodium-air battery cathode, it was also found that N-GNSs showed higher electrocatalytic activity for oxygen reduction reaction and oxygen evolution reaction, resulting in improving discharge and charge performance

The Operating Efficiency Evaluation of the Highway Network Under Accident Conditions

AbstractIn order to improve the running safety of highway, to minimize traffic delay, and to avoid the secondary traffic accident, it is essential to evaluate the operating efficiency of the highway network under accident conditions. This article selects the time reliability as evaluation index and compares the index value of the highway network under normal, accident conditions and after emergency traffic organizations. Differences are used to perform an analysis on the impact on traffic of the accident, the result of the emergency traffic organization and the recovery degree of the transport. The paper provides some basis for the traffic organization plan optimization of the road network under the accident conditions

Adiabatic compressed air energy storage with packed bed thermal energy storage

AbstractThe majority of articles on Adiabatic Compressed Air Energy Storage (A-CAES) so far have focussed on the use of indirect-contact heat exchangers and a thermal fluid in which to store the compression heat. While packed beds have been suggested, a detailed analysis of A-CAES with packed beds is lacking in the available literature. This paper presents such an analysis. We develop a numerical model of an A-CAES system with packed beds and validate it against analytical solutions. Our results suggest that an efficiency in excess of 70% should be achievable, which is higher than many of the previous estimates for A-CAES systems using indirect-contact heat exchangers. We carry out an exergy analysis for a single charge–storage–discharge cycle to see where the main losses are likely to transpire and we find that the main losses occur in the compressors and expanders (accounting for nearly 20% of the work input) rather than in the packed beds. The system is then simulated for continuous cycling and it is found that the build-up of leftover heat from previous cycles in the packed beds results in higher steady state temperature profiles of the packed beds. This leads to a small reduction (<0.5%) in efficiency for continuous operation

Optimizing Laguerre expansion based deconvolution methods for analysing bi-exponential fluorescence lifetime images

Fast deconvolution is an essential step to calibrate instrument responses in big fluorescence lifetime imaging microscopy (FLIM) image analysis. This paper examined a computationally effective least squares deconvolution method based on Laguerre expansion (LSD-LE), recently developed for clinical diagnosis applications, and proposed new criteria for selecting Laguerre basis functions (LBFs) without considering the mutual orthonormalities between LBFs. Compared with the previously reported LSD-LE, the improved LSD-LE allows to use a higher laser repetition rate, reducing the acquisition time per measurement. Moreover, we extended it, for the first time, to analyze bi-exponential fluorescence decays for more general FLIM-FRET applications. The proposed method was tested on both synthesized bi-exponential and realistic FLIM data for studying the endocytosis of gold nanorods in Hek293 cells. Compared with the previously reported constrained LSD-LE, it shows promising results

In Situ Mineralization of Magnetite Nanoparticles in Chitosan Hydrogel

Based on chelation effect between iron ions and amino groups of chitosan, in situ mineralization of magnetite nanoparticles in chitosan hydrogel under ambient conditions was proposed. The chelation effect between iron ions and amino groups in CS–Fe complex, which led to that chitosan hydrogel exerted a crucial control on the magnetite mineralization, was proved by X-ray photoelectron spectrum. The composition, morphology and size of the mineralized magnetite nanoparticles were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy and thermal gravity. The mineralized nanoparticles were nonstoichiometric magnetite with a unit formula of Fe2.85O4and coated by a thin layer of chitosan. The mineralized magnetite nanoparticles with mean diameter of 13 nm dispersed in chitosan hydrogel uniformly. Magnetization measurement indicated that superparamagnetism behavior was exhibited. These magnetite nanoparticles mineralized in chitosan hydrogel have potential applications in the field of biotechnology. Moreover, this method can also be used to synthesize other kinds of inorganic nanoparticles, such as ZnO, Fe2O3and hydroxyapatite