Boron complexes of π-extended nitroxide ligands exhibiting three-state redox processes and near-infrared-II (NIR-II) absorption properties.

Persistent radicals have attracted increasing attention owing to their fascinating properties, including multi-step redox and long-wavelength absorption characteristics. In this study, boron complexes with π-extended nitroxide ligands were synthesised via Buchwald-Hartwig amination reactions of the corresponding boron-nitroxide complex and diarylamines. These nitroxide complexes exhibited two-step and reversible one-electron oxidation processes, suggesting stable redox triads involving anionic aminoxide, neutral nitroxide-radical, and cationic oxoammonium ligands. Cationic boron complexes of the nitroxide radical ligands were obtained via chemical oxidation of the aminoxide complexes and structurally characterised. The cationic nitroxide-radical complexes exhibited strong absorptions at approximately 1100 nm, demonstrating their potential as near-infrared (NIR)-II-active functional dyes.

Finite element analysis of the fracture statistics of self-healing ceramics.

Self-healing materials have been recognized as a promising type of next-generation materials. Among them, self-healing ceramics play a particularly important role, and understanding them better is necessary. Therefore, in this study, we applied the oxidation kinetics-based constitutive model to finite element analysis of a series of damage-healing processes in self-healing ceramics (alumina/SiC composites). In the finite element analysis, the data on the microstructure distribution, such as relative density, size and aspect ratio of pores, and grain size, were taken as input values and reflected onto the parameters of a continuum damage model using a fracture mechanical model. We then performed a 3-point bending analysis, to consider both the self-healing effect under certain temperature and oxygen partial pressure conditions and scatter of the strength of the ceramics. Our results confirmed that the proposed methodology can reasonably reproduce both strength recovery and damage propagation behavior in self-healing ceramics.