Redox-Active Metaphosphate-Like Terminals Enable High-Capacity MXene Anodes for Ultrafast Na-Ion Storage

D transition metal carbides and/or nitrides, so-called MXenes, are noted as ideal fast-charging cation-intercalation electrode materials, which nevertheless suffer from limited specific capacities. Herein, it is reported that constructing redox-active phosphorus−oxygen terminals can be an attractive strategy for Nb$_4$C$_3$ MXenes to remarkably boost their specific capacities for ultrafast Na$^+$ storage. As revealed, redox-active terminals with a stoichiometric formula of PO$_2$- display a metaphosphate-like configuration with each P atom sustaining three P-O bonds and one P=O dangling bond. Compared with conventional O-terminals, metaphosphate-like terminals empower Nb$_4$C$_3$ (denoted PO$_2$-Nb$_4$C$_3$) with considerably enriched carrier density (fourfold), improved conductivity (12.3-fold at 300 K), additional redox-active sites, boosted Nb redox depth, nondeclined Na$^+$-diffusion capability, and buffered internal stress during Na$^+$ intercalation/de-intercalation. Consequently, compared with O-terminated Nb$_4$C$_3$, PO$_2$-Nb$_4$C$_3$ exhibits a doubled Na$^+$-storage capacity (221.0 mAh g$^{-1}$), well-retained fast-charging capability (4.9 min at 80% capacity retention), significantly promoted cycle life (nondegraded capacity over 2000 cycles), and justified feasibility for assembling energy−power-balanced Na-ion capacitors. This study unveils that the molecular-level design of MXene terminals provides opportunities for developing simultaneously high-capacity and fast-charging electrodes, alleviating the energy−power tradeoff typical for energy-storage devices

Equipment and methods for rapid analysis of PWO full-sized scintillation crystal radiation hardness during mass production

The mass production of lead tungstate crystals (PWO) for the Compact Muon Solenoid (CMS) Project at CERN began at the Bogoroditsk Techno- Chemical Plant (BTCP, Tula Region, Russia) in 2000. Mass production technology, developed in recent years, is based on a set of methods and instrumentation for crystal growth and machining, as well as quality control and certification of crystals. One of the most crucial categories of tolerances is the radiation hardness of crystals. Control of the PWO radiation hardness during the mass production phase requires a reliable, easy-to-use measuring tool with high productivity. A semiautomatic spectrometric setup for PWO radiation hardness monitoring was developed and tested at CERN. After final crosschecks, the setup was put into operation at BTCP. (13 refs)

Equipment and methods for rapid analysis of PWO full size scintillation crystals radiation hardness at mass production

This year an extensive R&D on lead tungstate crystals has entered into the pre-production phase at the Bogoroditsk Techno-Chemical Plant (BTCP). Laboratory small-scale PWO crystal growth technology, which has been tuned and optimised over the last years, is transforming now into an industrial technology of mass production. This mass production technology is based on a set of methods and instrumentation for crystal growth, machining, crystal quality control and certification. According to the specification on lead tungstate pre-production crystals, one of the most important categories of tolerance is the radiation hardness. Control of the PWO radiation hardness at the pre-production phase requires reliability and an easy to use measuring tool with a high productivity. A semi- automatic spectrometric setup for PWO radiation hardness monitoring has been developed and tested at the X5 CERN irradiation facility. After final crosschecks the setup was set into operation at the BTCP. Together with several other methods this setup covers a full range of radiation damage phenomena in PWO crystals. (5 refs)

Fundamental and Applied Studies of Molecular Plasmas Using Infrared Absorption Techniques

Over the past few years mid infrared absorption spectroscopy (MIR-AS) over the region from 3 to 20 ?m has progressed considerably as a powerful diagnostic technique for in situ studies of the fundamental physics and chemistry of molecular plasmas. The increasing interest in processing plasmas containing hydrocarbons, fluorocarbons, nitrogen oxides and organo-silicon compounds has led to further applications of MIR-AS because most of these compounds and their decomposition products are infrared active. MIR-AS provides a means of determining the absolute concentrations of the ground states of stable and transient molecular species at time resolutions below a micro second, which is of particular importance for the investigation of reaction kinetics and dynamics. Information about gas temperature and population densities can also be derived from MIR-AS measurements. Since plasmas with molecular feed gases are used in many applications such as thin film deposition, semiconductor processing, surface activation and cleaning, and materials and waste treatment, this has stimulated the adaptation of MIR-AS techniques to industrial requirements including the development of new diagnostic equipment. The aim of the present chapter is fourfold: (i) to briefly summarize the basic principles of infrared absorption spectroscopy and related instrumentation, (ii) to report on recent achievements in our understanding of molecular phenomena in plasmas using different types of MIR-AS techniques, (iii) to describe examples of industrial process monitoring in the mid infrared and (iv) to discuss the potential of advanced instrumentation based on quantum cascade lasers (QCLs) for plasma diagnostics