The origin and chronology of medieval silver coins based on the analysis of chemical composition

Medieval Central Europe coins – the Saxon coins, also called as the Otto and Adelheid denarii, as well as the Polish ones, the Władysław Herman and Bolesław Śmiały coins – were examined to determine their provenance and dating. Their attribution and chronology often constitute a serious problem for historians and numismatists. For hundreds of years, coins were in uncontrolled conditions and in variable environment. Destructed and inhomogeneous surface were the effect of corrosion processes. Electron microscopy with energy dispersive X-ray analysis (scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS)), X-ray fluorescence (XRF) analysis (energy dispersive X-ray fluorescence (EDXRF) and total reflection X-ray fluorescence (TXRF)), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were applied. The results of these investigations are significant for our knowledge of the history of Central European coinage, especially of Polish coinage

Agglutination of single catalyst particles during fluid catalytic cracking as observed by X-ray nanotomography

Metal accumulation at the catalyst particle surface plays a role in particle agglutination during fluid catalytic cracking

Using X‑ray Microscopy To Understand How Nanoporous Materials Can Be Used To Reduce the Large Volume Change in Alloy Anodes

Tin metal is an attractive negative electrode material to replace graphite in Li-ion batteries due to its high energy density. However, tin undergoes a large volume change upon alloying with Li, which pulverizes the particles, and ultimately leads to short cycling lifetimes. Nevertheless, nanoporous materials have been shown to extend battery life well past what is observed in nonporous material. Despite the exciting potential of porous alloying anodes to significantly increase the energy density in Li-ion batteries, the fundamental physics of how nanoscale architectures accommodate the electrochemically induced volume changes are poorly understood. Here, operando transmission X-ray microscopy has been used to develop an understanding of the mechanisms that govern the enhanced cycling stability in nanoporous tin. We found that in comparison to dense tin, nanoporous tin undergoes a 6-fold smaller areal expansion after lithiation, as a result of the internal porosity and unique nanoscale architecture. The expansion is also more gradual in nanoporous tin compared to the dense material. The nanoscale resolution of the microscope used in this study is ∼30 nm, which allowed us to directly observe the pore structure during lithiation and delithiation. We found that nanoporous tin remains porous during the first insertion and desinsertion cycle. This observation is key, as fully closed pores could lead to mechanical instability, electrolyte inaccessibility, and short lifetimes. While tin was chosen for this study because of its high X-ray contrast, the results of this work should be general to other alloy-type systems, such as Si, that also suffer from volume change based cycling degradation

Mechanism of Na+ Insertion in Alkali Vanadates and Its Influence on Battery Performance

Sodium-ion batteries may become an alternative to the widespread lithium-ion technology due to cost and kinetic advantages provided that cyclability is improved. For this purpose, the interplay between electrochemical and structural processes is key and is demonstrated in this work for Na2.46V6O16 (NVO) and Li2.55V6O16 employing operando synchrotron X-ray diffraction. When NVO is cycled between 4.0 and 1.6 V, Na-ions reversibly occupy two crystallographic sites, which results in remarkable cyclability. Upon discharge to 1.0 V, however, Na-ions occupy also interstitial sites, inducing irreversible structural change with some loss of crystallinity concomitant with a decrease in capacity. Capacity fading increases with the ionic radius of the alkali ions (K+ > Na+ > Li+), suggesting that smaller ions stabilize the structure. This correlation of structural variation and electrochemical performance suggests a route toward improving cycling stability of a sodium-ion battery. Its essence is a minor Li+-retention in the A2+xV6O16 structure. Even though the majority of Li-ions are replaced by the abundant Na+, the residual Li-ions (≈10%) are sufficient to stabilize the layered structure, diminishing the irreversible structural damage. These results pave the way for further exploitation of the role of small ions in lattice stabilization that increases cycling performance.NRF (Natl Research Foundation, S’pore)Accepted versio

Reversible Multivalent (Monovalent, Divalent, Trivalent) Ion Insertion in Open Framework Materials

solution. Reversible electrochemical insertion of ions into materials would present a valuable alternative to these existing technologies because of the ease of cycling and reuse. Moreover, the reversible insertion of monovalent ions has been thoroughly explored because of its relevance to intercalation battery electrodes, including electrodes for nickel-metal hydride and lithium-ion batteries. The physical and electrochemical properties of PB analogues have been explored thoroughly. The reversible electrochemical insertion of multivalent ions into materials has promising applications in many fi elds, including batteries, seawater desalination, element purifi cation, and wastewater treatment. However, fi nding materials that allow for the insertion of multivalent ions with fast kinetics and stable cycling has proven diffi cult because of strong electrostatic interactions between the highly charged insertion ions and atoms in the host framework. Here, an open framework nanomaterial, copper hexacyanoferrate, in the Prussian Blue family is presented that allows for the reversible insertion of a wide variety of monovalent, divalent, and trivalent ions (such as Rb + , Pb 2+ , Al 3+ , and Y 3+ ) in aqueous solution beyond that achieved in previous studies. Electrochemical measurements demonstrate the unprecedented kinetics of multivalent ion insertion associated with this material. Synchrotron X-ray diffraction experiments point toward a novel vacancy-mediated ion insertion mechanism that reduces electrostatic repulsion and helps to facilitate the observed rapid ion insertion. The results suggest a new approach to multi valent ion insertion that may help to advance the understanding of this complex phenomenon