Probing the charge injection and dissipation in graphene oxide–epoxy composite

The inorganic filler can modify the electrical and dielectric properties of polymeric composites. However, it is challenging to understand the local charge injection and dissipation in composites through traditional characterization at nanoscale. In this work, we provide a potential mapping of the charge injection and dissipation in the local area of graphene oxide/epoxy resin (GO/EP) composite under various biases by Kelvin probe force microscopy (KPFM) with high spatial resolution. Thus, an improved KPFM experimental setup is used to inject charges at the fixed point to demonstrate surface charge dissipation around the interface between GO and EP. It is found that the charge is more easily injected into the GO/EP nanocomposites and dissipates more quickly in nanocomposite than in neat epoxy resins. Meanwhile, the electrons diffuse more rapidly than holes in pure EP and nanocomposites. The faster charge injection and dissipation of GO/EP composite are ascribed to the filler of GO which has much higher conductivity than that of neat epoxy. This work offers significant insights into the understanding of charge injection and dissipation in dielectric composites.

Modeling the electrical energy discharged by lightning flashes using capacitors for application with lightning datasets

This study employed a parallel plate capacitor model by which the electrostatic energy of lightning flashes could be estimated by considering only their physical dimensions and breakdown electric fields in two simulated storms. The capacitor model has previously been used to approximate total stormelectrostatic energy but is modified here to use the geometry of individual lightning flashes to mimic the local charge configuration where flashes were initiated. The energy discharged may then be diagnosed without context of a storm’s entire charge structure. The capacitor model was evaluated using simulated flashes from two storms modeled by the National Severe Storms Laboratory’s Collaborative Model for Multi-scale Atmospheric Simulation (COMMAS). Initial capacitor model estimates followed the temporal evolution of the flash discharge energy of COMMAS for each storm but demonstrated the need to account for an adjustment factor to represent the fraction of energy a flash dissipates, as this model assumes the entire pre-flash energy is discharged by a flash. Individual values of were obtained simply by using the ratio of the COMMAS flash to capacitor energy. Median values were selected to represent the flash populations for each storm, and were in range of = 0.019−0.021. Application of aligned the magnitudes of the capacitor model discharge energy estimates to those of COMMAS and to those estimated in previous studies. Therefore, by considering a within range of , application of the capacitor model for observed lightning datasets is suggested.

Synthesis and Characterization of Magnesium Vanadates as Potential Mg-ion Cathode Materials Through an Ab Initio Guided Carbothermal Reduction Approach

Many technologically relevant transition metal oxides for advanced energy storage and catalysis feature reduced transition metal (TM) oxides and are often nontrivial to prepare because of the need to control the reducing nature of the atmosphere in which they are synthesized. In this work, we show that an ab initio predictive synthesis strategy can be used to produce multiple gram-scale products of various MgVxOy-type phases (δ-MgV2O5, spinel MgV2O4, and MgVO3) containing V3+ or V4+ relevant for Mg-ion battery cathodes. Characterization of these phases using 25Mg solid-state NMR spectroscopy illustrates the potential of 25Mg NMR for studying reversible magnesiation and local charge distributions. Rotor-Assisted Population Transfer is used as a much needed signal-to-noise enhancement technique. The ab initio guided synthesis approach is seen as a step forward towards a predictive synthesis strategy for targeting specific complex TM oxides with variable oxidation states of technological importance.