Interfacial Engineering of Na3V2(PO4)2O2F Cathode for Low-Temperature (-40 °C) Sodium-Ion Batteries.

Na3V2(PO4)2O2F (NVPOF) is considered a promising cathode material for sodium-ion batteries (SIBs) on account of its attractive electrochemical properties such as high theoretical capacity, stable structure, and high working platform. Nevertheless, the inevitable interface problems like sluggish interfacial electrochemical reaction kinetics and poor interfacial ion storage capacity seriously hinder its application. Construction of chemical bonding is a highly effective way to solve interface problems. Herein, NVPOF with interfacial V-F-C bonding (CB-NVPOF) is developed. The CB-NVPOF cathode exhibits high rate capability (65 mA h g-1 at 40C) and long-term cycling stability (a capacity retention of 77% after 2000 cycles at 20C). Furthermore, it shows impressive electrochemical performance at temperatures as low as -40 °C, delivering a capacity of 56 mA h g-1 at 10C and a capacity retention of ∼80% after 500 cycles at 2C. The interfacial V-F-C bond engineering significantly advances the electronic conductivity, Na+ diffusion, as well as interface compatibility at -40 °C. This study provides a novel idea for improving the electrochemical performance of NVPOF-based cathodes for SIBs aiming for low-temperature applications.

Oblique laser shock peening effect of the FGH95 superalloy with a PCA and comprehensive index.

As a metal surface strengthening technology, oblique laser shock peening uses the force effect of pulsed laser beams to significantly improve the mechanical properties of materials and prolong service life. However, the processing of metal parts still requires a high cost for testing the quality of the finished product. At present, there is no systematic and complete measurement method or evaluation system for the finished products of oblique laser shock peening technology. In this paper, a principal component analysis method and a comprehensive index method are organically combined to construct a method for evaluating the effect of oblique laser shock peening of FGH95 superalloy turbine disks. We measured 10 real data of FGH95 superalloy specimens after oblique laser shock peening by using the orthogonal test method and verified the data. Based on the evaluation results, we put forward a series of suggestions to improve the quality of oblique laser shock peening of FGH95 high-temperature turbine disks, providing a certain reference and guidance for processing FGH95 superalloy turbine disks.