The intrinsic competition among multiple charge transfer (CT) pathways in copper-phenylacetylide (PhC₂Cu) has hindered the desirable development of its photoactive properties, whereas substantial spectral and temporal overlap among these pathways has obscured direct mechanistic understanding. Herein, hydrostatic pressure was employed as a clean and reversible external stimulus to continuously compress the one-dimensional Cu(I)–Cu(I) ladder in pristine PhC₂Cu without modifying its chemical composition. In situ high-pressure photoluminescence and transient absorption (TA) spectroscopy reveal a pressure-induced evolution of CT from copper to the acetylide carbon. High-pressure crystallographic analysis and X-ray absorption near-edge structure measurements (XANES) demonstrate that anisotropic contraction of the Cu(I) ladder reconstructs the copper coordination environment and consequently modulates the relative contributions of metal-to-ligand CT pathways. These structure-dependent electronic dynamics provide direct insight into the CT mechanism of PhC₂Cu and establish hydrostatic pressure as a general and non-destructive strategy for investigating CT processes in one-dimensional (1D) coordination compounds.

High-entropy carbide (HEC) ceramics exhibit exceptional potential surpassing that of conventional ceramics in terms of hardness, thermal stability, irradiation resistance, and oxidation resistance, thereby holding broad application prospects. Nevertheless, their intrinsic brittleness remains a critical bottleneck constraining engineering application. In this study, nano-SiC (n-SiC) was employed as a reinforcing phase to fabricate HEC-n-SiC composite ceramics via high-pressure high-temperature (HPHT) sintering. The results demonstrate that under the optimal sintering conditions of 5 GPa, 2000 ℃, and a holding time of 15 min, the specimens achieve the highest relative density and the finest grain size (135.6 nm). SiC is successfully dissolved into the high-entropy carbide lattice, forming a six-component solid solution. At an HEC:SiC molar ratio of 9:1, the material exhibits optimum comprehensive performance, with a hardness of 24.0 GPa and a fracture toughness of 10.2 MPa·m^1/2, achieving a synergistic enhancement of hardness and toughness. Crack morphology observations and TEM characterization reveal that the strengthening and toughening mechanisms predominantly include: n-SiC-induced lattice distortion giving rise to dislocations and stacking faults, which contribute to solid-solution strengthening, while simultaneously promoting crack deflection that dissipates additional fracture energy and thereby enhances toughness. This work extends the second-phase strengthening strategy from conventional “interfacial toughening” to “intra-lattice toughening”, providing a novel paradigm for the design and fabrication of high-performance high-entropy ceramics.

The preparation of dense Si₃N₄-based ceramics has attracted great attention because of the achievable improvements in their mechanical properties and high-temperature oxidation resistance. In this work, advanced dense boron-containing α/β-Si₃N₄/Si monoliths were prepared via a high pressure‒high temperature technique in which polymer-derived amorphous SiBN powders were used as raw materials. The crystallization behavior and phase transformation of the polymer-derived amorphous samples were studied in the temperature range from 1400 to 1800 °C. The results demonstrate that the incorporation of boron in the Si₃N₄ matrix suppresses the phase transformation from α-Si₃N₄ to β-Si₃N₄. Furthermore, the mechanical properties of the as-prepared samples were measured, and the maximum hardness and fracture toughness of boron-rich SiBN samples reached 14.8 GPa and 7.96 MPa·m^1/2, respectively. The hardness of the obtained boron-rich SiBN samples is stable up to 300 °C. In addition, the oxidation behavior of the samples prepared at 1400 and 1600 °C was investigated at 1400 °C for 50 h. The results show that the incorporation of boron significantly improved the oxidation resistance of the samples because of the formation of borosilicate/cristobalite. This work provides guidance for the synthesis of boron-containing α/β-Si₃N₄-based ceramics with excellent mechanical properties and oxidation resistance.