MICROSCOPIC CORROSION STUDIES OF DUPLEX STAINLESS STEELS

Electrochemical scanning tunneling microscopy and scanning electrochemical microscopy have been used for in situ monitoring of localized corrosion processes of different Duplex stainless steels (DSS) in acidic chloride solutions. The techniques allow imaging of local dissolution events with micrometer resolution, as opposed to conventional electrochemical techniques, which only give an overall view of the corrosion behavior. In addition, combined scanning Kelvin probe force microscopy and magnetic force microscopy were used for mapping the Volta potential variation over the surface of DSSs. A significant difference in Volta potential between the austenite and ferrite phases suggests galvanic interaction between the phases. A compositional gradient appears within 2 micrometers across the phase boundary, as seen with scanning Auger microscopy (SAM). In all, the studies suggest that higher alloyed DSS exhibit a more homogeneous dissolution behavior than lower alloyed DSS, due to higher and more similar corrosion resistance of the two phases, and enhanced resistance of the ferrite/austenite phase boundary regions.

Whole-brain Optical Imaging:A Powerful Tool for Precise Brain Mapping at the Mesoscopic Level

The mammalian brain is a highly complex network that consists of millions to billions of densely-interconnected neurons.Precise dissection of neural circuits at the mesoscopic level can provide important structural information for understanding the brain.Optical approaches can achieve submicron lateral resolution and achieve“optical sectioning”by a variety of means,which has the natural advantage of allowing the observation of neural circuits at the mesoscopic level.Automated whole-brain optical imaging methods based on tissue clearing or histological sectioning surpass the limitation of optical imaging depth in biological tissues and can provide delicate structural information in a large volume of tissues.Combined with various fluorescent labeling techniques,whole-brain optical imaging methods have shown great potential in the brain-wide quantitative profiling of cells,circuits,and blood vessels.In this review,we summarize the principles and implementations of various whole-brain optical imaging methods and provide some concepts regarding their future development.

3D X-ray microscopy with a CsPbBr3 nanowire scintillator

X-ray microscopy is an essential imaging method in many scientific fields,which can be extended to three-dimensional(3D)using tomography.Recently,metal halide perovskite(MHP)nanomaterials have become a promising candidate for X-ray scintillators,due to their high light yield,high spatial resolution,and easy fabrication.Tomography requires many projections and therefore scintillators with excellent stability.This is challenging for MHPs,which often suffer from fast degradation under X-ray irradiation and ambient conditions.Here,we demonstrate that MHP scintillators of CsPbBr3 nanowires(diameter:60 nm,length:5–9μm)grown in anodized aluminum oxide(CsPbBr3 NW/AAO)have sufficient stability for X-ray micro-tomography.A tomogram was taken with a Cu X-ray source over 41 h(dose 4.2 Gyair).During this period the scintillator brightness fluctuated less than 5%,which enabled a successful reconstruction.A long-term study with 2 weeks of continuous X-ray exposure(37.5 Gyair)showed less than 14%fluctuations in brightness and no long-term degradation,despite variations in the ambient relative humidity from 7.4%RH to 34.2%RH.The resolution was stable at(180±20)lp·mm−1,i.e.,about 2.8 micron.This demonstrates that CsPbBr3 NW/AAO scintillators are promising candidates for high resolution X-ray imaging detectors.