In this study, it was found that an ancient bronze sword had special microstructures, i.e., a tin (Sn)-rich layer (Sn: 38.51 wt.%), that was around 0.1–0.3 mm in thickness in the bronze substrate (Sn: 18.57 wt.%). This sword was unearthed from the same Chu tombs of the “Sword of Gou Jian”, and dated back to the late Spring and Autumn Period (496 BC–464 BC). The experimental and theoretical analyses revealed that (1) the Sn-rich layer exhibited higher microhardness (around 650 HV) than the sword body (around 300 HV); (2) the Sn-rich layer showed a brittle fracture due to the formation of a large amount of α + δ eutectoid, while the sword body was of good toughness due to a large amount of α-Cu solid solution phase; and (3) theoretical calculations of Sn diffusion in the Cu substrate indicated that this Sn-rich layer could have been formed within several hours or several days if the temperature was above 600 °C. Therefore, this sword was proposed to be a novel kind of composite bronze sword, and the possible manufacturing technique was a surface treatment called “dip or wipe tinning” or tin amalgam, which was widely used in the Bronze Age. Technically, this process possesses more advantages than the well-known two-times casting for making the “double-colour” or bi-metallic composite bronze sword. This research showed that the materials processing level was beyond our expectations for ancient China 2500 years ago.

Antibacterial and antifungal activity

This paper reports the results of a full-scale field test that was conducted to assess the performance of the use of wet-milling cement and chemical compound grouting in the same hole to reinforce a flexural fracture zone. Wet-milling cement and chemical compound grouting methods were used to treat a layer of the flexural fracture zone with a thickness of 19 m. The procedures of the cement–chemical compound grouting method were described in detail, and the results of the normal water pressure test, fatigue water pressure test, failure water pressure test, and shear wave velocity test suggested that the working effects in the epoxy testing area were better than those in the acrylic acid salt test area, which further indicated that the cement–chemical compound grouting method was feasible. In addition, the improvement mechanism of the cement–chemical compound grouting technology was studied; this method is beneficial for solving the problem of the reinforcement effect not being ideal in practical engineering and further improving the compactness of dam structures.

The degradation of stone surfaces resulting from natural aging and environmental factors poses significant challenges to material durability and esthetics. This review systematically summarizes recent advances in composite protective materials designed to enhance stone surface preservation. It focuses on the classifications and fundamental properties of organic polymer-based materials, inorganic nanocomposites, and multifunctional protective coatings, emphasizing their physicochemical, mechanical, and environmental performance. The review further analyzes case studies across various stone substrates, such as marble, limestone, sandstone, and granite, highlighting substrate-specific coating compatibility and protective effectiveness against water ingress, biological colonization, graffiti, and pollutant deposition. Critical factors influencing protective performance, including stone mineralogy, coating composition, environmental conditions, and application protocols, are elucidated. Finally, existing challenges and future research directions are identified, underscoring the need for environmentally friendly, multifunctional, and durable composite coatings with enhanced substrate adaptability and simplified application processes.

This study evaluates the performance degradation of spray rigid polyurethane foam (RPUF) insulation on reservoir dam structures under multi-physics coupling conditions. Focusing on characteristic environmental exposures in Hot Summer and Cold Winter (HSCW) climate zones, accelerated aging tests simulating coupled temperature–humidity effects were conducted to comparatively analyze the thermal resistance and durability evolution between unprotected and encapsulated RPUF configurations. Scanning electron microscopy (SEM), infrared spectroscopy (IR), and other methods were used to characterize and analyze the structure of RPUF. Research has shown that in HSCW climate zones, the thermal conductivity of RPUF gradually increases with the number of degradation cycles, and the insulation performance decreases, mainly due to the damage of the pore structure caused by temperature aging and the combined effect of moisture absorption aging. In comparison, the RPUF after protection can effectively slow down the rate and degree of decline of its insulation performance. On this basis, a time-varying prediction model for the thermal conductivity of RPUF under long-term service in HSCW climate environments was fitted, providing a scientific basis for the durability evaluation of reservoir dam insulation.