The isothermal bainitic transformation kinetics, microstructure, and mechanical properties of the quenched low-carbon high-strength steel have been investigated via dilatometric measurements, microstructural characterization, and mechanical tests. The results show that the pre-transformed isothermal bainite promotes martensitic transformation, increasing the martensitic transformation temperature, and enhancing the transformation rate. The microstructure of the 400 °C isothermal steel consists predominantly of lath bainite ferrite with dot/slender M-A constituents, whereas the steel treated at 450 °C contains a combination of martensite/lath bainite and granular bainite. The presence of massive M-A constituents contributes to brittle fracture as these constituents tend to promote crack initiation. Hence, the 450 °C treatment, which leads to the formation of massive M-A constituents, induces brittleness, while the finer M-A constituents formed at 400 °C exert minimal influence on the toughness and result in a more stable microstructure owing to their small size and the surrounding fine lath microstructure. The differences in microstructure and properties between the steels treated at 400 °C and 450 °C illustrate the importance of controlling the quenching cooling rate in the high-temperature bainitic transformation region during thick plate quenching processes.

Hydrogels, especially Polyvinyl alcohols, have received extensive attention as alternative materials for articular cartilage. Aiming at the problems such as low strength and poor toughness of polyvinyl alcohol hydrogels in practical applications, an enhancement and modification strategy is proposed. Sodium alginate fibers were introduced into polyvinyl alcohol hydrogel network through physical blending and freezing/thawing methods. The prepared composite hydrogels exhibited a three-dimensional porous network structure similar to that of human articular cartilage. The mechanical and tribological properties of hydrogels have been significantly improved, due to the multiple hydrogen bonding interaction between sodium alginate fibers and polyvinyl alcohol. Most importantly, under a load of 2 N, the friction coefficient of the PVA/0.4SA hydrogel can remain stable at 0.02 when lubricated in PBS buffer for 1 h. This work provides a novel design strategy for the development of high-performance polyvinyl alcohol hydrogels.

A novel strategy was adopted to enhance the energy storage properties of materials through constructing a vacancy defect. BaTi_1−xCu_xO_3−x (abbreviated as BTCx, x = 0–0.05) ceramics were prepared. The influences of Cu doping on structure and electrical properties were systematically investigated in this study. The result reveals that the oxygen vacancies in BTCx ceramics can inhibit grain growth and improve breakdown strength. Notably, as Cu content increases, the abundance of oxygen vacancies of the BTCx ceramics intensifies the relaxor behavior and induces double hysteresis loops with high energy storage performance. The excellent energy storage density of 1.34 J/cm³ and efficiency of 90.1% were achieved for BTC3 ceramics at 180 kV/cm, which indicates that the outstanding energy storage properties of BTCx ceramics make them have broad application prospects in advanced pulse power capacitors.

Traditional artificial joints mainly face the challenges of severe wear and aseptic loosening, which limits their application as joint bearing interfaces under high-stress loading conditions. To improve this problem, inspired by the gradient modulus structure of natural cartilage/subchondral bone and the inherent negative charge characteristics of the surface, a negatively charged hydrogel layer was adhered to a porous Ti6Al4V surface through a combination of ultraviolet irradiation and freeze–thaw cycles. The cross-sectional SEM image exhibited that the hydrogel layer was closely bonded to the hard substrate. After physical doping with SBMA, the lubrication performance of the composite bearing interface was significantly improved, primarily attributable to the biphasic lubrication of the hydrogel layer and the hydration lubrication mechanism of SBMA.

The (1−x)Ba_0.96Ca_0.04TiO₃-xBa(Mg_1/3Nb_2/3)O₃ (x = 0–0.20) lead-free ceramics were prepared through the chemical-furnace-assisted combustion synthesis (abbreviated as CFACS). The phase structure, microstructure, dielectric, and piezoelectric properties were systematically investigated. Phase analysis revealed the coexistence of orthorhombic and tetragonal phases in the vicinity of x = 0.07. More importantly, the composition with x = 0.07 exhibited optimal overall electrical properties, including a high piezoelectric coefficient (d₃₃) of 495 pC/N, the planar electromechanical coupling factor (K_p) of 41.9%, and the Curie temperature (T_c) of 123.7 °C. In addition, the average grain size was observed to progressively decrease with increasing x.