Localized Corrosion and Stress Corrosion Cracking Behavior of AA7003 in a 3.5 wt% NaCl Aqueous Solution

The microstructure,localized corrosion (LC) and stress corrosion cracking (SCC) behavior of 7003 aluminum alloy (AA7003) under various aging treatments (peak aging (PA),double peak aging (DPA),regression and re-aging (RRA)) were investigated by means of transmission electron microscope (TEM),scanning electron microscopy (SEM),electrochemical impendence spectroscopy (EIS) and slow strain rate tensile test.The results of TEM showed a discontinuous distribution of grain boundary precipitates of AA7003 under DPA and RRA treatments,which is beneficial for increasing the resistance of LC and SCC.Meanwhile,LC was found initiating firstly on intermetallics which caused the dissolution of surrounding matrix,then pitting holes were formed and developed into matrix.In addition,the SCC process of AA7003 could be divided into two stages,i e,initial pre-cracking and breeding cracking.The EIS analysis,cross-section morphologies and fracture surfaces of specimens indicated that DPA and RRA treatments significantly decreased the crack growth rate during breeding cracking stage,especially for RRA treatment.

Post-treatment by an ionic tetrabutylammonium hexafluorophosphate for improved efficiency and stability of perovskite solar cells

Interface engineering is an effective way to improve efficiency and long-term stability of perovskite solar cells(PSCs).Herein,an ionic compound tetrabutylammonium hexafluorophosphate(TP6)is adopted to passivate surface defects of the perovskite film.It is found that TP6 effectively reduced the surface defects,especially at the grain boundaries where the defects are abundant.Meanwhile,the exposed long alkyl chains and fluorine atoms in the TP6 enhanced the moisture stability of the perovskite film due to its strong hydrophobicity.In addition,the driving force of charge carrier separation and transport is increased by enlarged built-in potential.Consequently,the power conversion efficiency(PCE)of PSCs is significantly improved from 20.59% to 22.41%by increased open-circuit voltage(V_(oc))and fill factor(FF).The unencapsulated device with TP6 treatment exhibits better stability than the control device,and the PCE retains-80%of its initial PCE after 30 days under 15%-25%relative humidity in storage,while the PCE of the control device declines by more than 50%.

Photothermal materials for efficient solar powered steam generation

Solar powered steam generation is an emerging area in the field o f energy harvest and sustainable technologies.The nano-structured photothermal materials are able to harvest energy from the full solar spectrum and convert it to heat with high efficiency.Moreover,the materials and structures for heat management as well as the mass transportation are also brought to the forefront.Several groups have reported their materials and structures as solutions for high performance devices,a few creatively coupled other physical fields with solar energy to achieve even better results.This paper provides a systematic review on the recent developments in photothermal nanomaterial discovery,material selection,structural design and mass/heat management,as well as their applications in seawater desalination and fresh water production from waste water with free solar energy.It also discusses current technical challenges and likely future developments.This article will help to stimulate novel ideas and new designs for the photothermal materials,towards efficient,low cost practical solar-driven clean water production.