Hard carbon derived from coconut shells,walnut shells,and corn silk biomass waste exhibiting high capacity for Na-ion batteries

In recent years,hard carbon materials have gained significant interest as anode materials for Na-ion batteries.Biomass waste is considered one of the most interesting,renewable,available,and cost-effective precursor to obtain hard carbon(HC);however,HC properties must be finely tuned to achieve performance comparable to those provided by Li-ion batteries.In this work,three biomass wastes(coconut shells,walnut shells,and corn silk) were evaluated as potential precursors for HC preparation involving a pyrolysis process and subsequent acid washing to remove the inorganic impurities.All obtained materials exhibited low and similar specific surface areas(<10 m^(2)·g^(-1)), but they presented different structures and surface functionalities.The walnut shell HC possessed a lower amount of inorganic impurities and oxygen-based functional groups compared to the coconut shell and corn silk HCs,leading to higher initial coulombic efficiency(iCE).The structural organization was higher in the case of the walnut shell HC,while the corn silk HC revealed a heterogeneous structure combining both highly disordered carbon and localized graphitized domains.All HCs delivered high initial reversible capacities between 293 and 315 mAh g^(-1) at 50 mA g^(-1) current rate,which remained rather stable during long-term cycling.The best capacity(293 mAh g^(-1) after 100 charge/discharge cycles) and highest capacity retention(93%) was achieved in walnut HCs in half-cells,which could be associated with its higher sp2 C content,better organized structure,and fewer impurities.An "adsorption-insertion" Na storage mechanism is suggested based on several techniques.The walnut HCs exhibited an attractive energy density of 279 Wh/kg when tested in full cells.

The Influence of Gravity on Single Crystallization in Large Volume Drops

The chemical, physical, and biological properties of more than two millions of proteins which follow to be synthesized by Pharmaceutical Industry, can be anticipated (by using their XRD diffrac-tograms) if they will be grown from aqueous drops as high quality, large volume single-crystals. This is not a simple task and usually the growing process is seen as art rather than a science. The growing is expensive, time consuming, and finally an amorphous aggregate may result instead one single-crystal. In this article, we show for the first time how one single crystal can be grown in large volume hanging drops through their fast evaporation. The single nucleation is determined by choosing the proper sense of gravitational force relative to the drop triple line contact. In a special configuration, single-crystals of glycine and threonine were rapidly grown.

Exploring fs-laser irradiation damage subthreshold behavior of dielectric mirrors via electrical measurements

With ultrafast laser systems reaching presently 10 PW peak power or operating at high repetition rates,research towards ensuring the long-term,trouble-free performance of all laser-exposed optical components is critical.Our work is focused on providing insight into the optical material behavior at fluences below the standardized laser-induced damage threshold(LIDT)value by implementing a simultaneous dual analysis of surface emitted particles using a Langmuir probe(LP)and the target current(TC).HfO_(2) and ZrO_(2) thin films deposited on fused silica substrates by pulsed laser deposition at various O_(2) pressures for defect and stoichiometry control were irradiated by Gaussian,ultrashort laser pulses(800 nm,10 Hz,70 fs)in a wide range of fluences.Both TC and LP collected signals were in good agreement with the existing theoretical description of laser–matter interaction at an ultrashort time scale.Our approach for an in situ LIDT monitoring system provides measurable signals for below-threshold irradiation conditions that indicate the endurance limit of the optical surfaces in the single-shot energy scanning mode.The LIDT value extracted from the LP-TC system is in line with the multipulse statistical analysis done with ISO 21254-2:2011(E).The implementation of the LP and TC as on-shot diagnostic tools for optical components will have a significant impact on the reliability of next-generation ultrafast and high-power laser systems.