High-entropy carbides are a nascent group of ceramics that are promising for high-temperature applications due to the combination of good stability, high hardness (H), high strength, and superior creep resistance that they display. Due to high melting points and low lattice diffusion coefficients, however, the high-entropy carbides are usually difficult to consolidate to a nearly full density. To cope with this challenge, herein, binary carbides including TiC, V₈C₇, NbC, Mo₂C, and WC with different carbon stoichiometry were used to prepare dense high-entropy (TiVNbMoW)C_4.375, and the influence of carbon vacancy on formation ability and mechanical properties of carbon-deficient high-entropy (TiVNbMoW)C_4.375 were investigated. Intriguingly, although the starting binary carbides have different crystal structures and carbon stoichiometry, the as-prepared high-entropy material showed a rock-salt structure with a relatively high density (98.1%) and good mechanical properties with hardness of 19.4±0.4 GPa and fracture toughness (K_IC) of 4.02 MPa·m^1/2. More importantly, the high-entropy (TiVNbMoW)C_4.375 exhibited low coefficient of friction (COF) at room temperature (RT) and 800 ℃. Wear rate (W) gradually increased with the temperature rising, which were attributed to the formation of low-hardness oxidation films at high temperatures to aggravate wear. At 800 ℃, lubricating films formed from sufficient oxidation products of V₂O₅ and MoO₃ effectively improved tribological behavior of the high-entropy (TiVNbMoW)C_4.375. Wear mechanisms were mainly abrasive wear resulting from grain pullout and brittle fracture as well as oxidation wear generated from high-temperature reactions. These results are useful as valuable guidance and reference to the synthesis of high-entropy ceramics (HECs) for sliding parts under high-temperature serving conditions.

High-entropy boride ceramics demonstrate outstanding high-temperature stability, positioning them as promising candidates for reliable performance in extreme environments. However, their inherent limitation lies in relatively low fracture toughness, coupled with the unclear elucidation of high-temperature tribological behaviors. To address these challenges, high-entropy (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂ (HEB) ceramics are utlized as the matrix material in the current investigation, while hexagonal boron nitride (h-BN) is introduced as a type of toughening and lubricating phase to develop HEB-hBN composite ceramics. The toughening and high-temperature self-lubrication of the composites are achieved by leveraging the high aspect ratio, lamellar microstructure, and interlayer slip characteristics of h-BN. Results indicate that h-BN enhances the fracture toughness of the composite ceramics by nearly 70%, attributed to the optimization of the crack growth path through its lamellar microstructure and facilitating crack deflection and bridging mechanisms due to its high aspect ratio. Moreover, through interlayer slip effects, h-BN collaborates with B₂O₃ and metal oxides generated from high-temperature oxidation, forming a gradient tribofilm in conjunction with other synergistic lubrication mechanisms. This synergistic interaction results in a nearly 40% reduction in the friction coefficient of the composite ceramics, accompanied by an approximately 60% decrease in wear rate under high-temperature friction conditions at 1000 °C. Under extreme friction environments ranging from 1000 °C to 1200 °C, the composite ceramic maintains a friction coefficient consistently below 0.30, with the wear rate stably sustained at an order of magnitude of 10^-5 mm³/(N·m).

As an excellent light metal material, titanium alloy has an important application in high technology equipment. In this study, the composite lubrication structure was prepared on the titanium alloy surface by combining the surface texture, thermal oxidation layer, and polytetrafluoroethylene (PTFE)-based lubricating coating. The effect of texture parameters and thermal oxidation layer on the fretting wear behavior of the composite lubrication structure was evaluated under a load of 50 N. The results showed that the PTFE-based lubricating coating on the textured surface showed excellent friction-reduction and anti-wear effect compared with the coating on the single smooth surface and thermal oxidation surface. The introduction of a thermal oxidation layer on the textured surface further improved the fretting wear life of lubrication coating. The friction coefficient and wear rate can be as low as 0.242 and 2.3 × 10⁻⁵ mm³·N⁻¹m⁻¹, respectively, under dry fretting contact conditions. Compared with the untextured surface, the longevity of the composite lubrication structure is extended by more than 90%.

Wearable pressure sensors show significant potential in areas such as health monitoring, electronic skin and human–computer interaction. However, achieving a balance between a wide sensing range and high sensitivity while simultaneously reducing manufacturing costs and simplifying fabrication processes remains a significant challenge for wearable pressure sensors. In this study, pressure sensors based on an MXene/Ag NFs coated cotton fabric (MACF) were prepared by a simple dip-coating technique. The hydroxyl groups in the cotton fabric interact with the hydrophilic groups on the MXene nanosheets, promoting strong adhesion between the two materials and forming a practical conductive pathway. The MACF sensor adopts a sandwich structure, demonstrating excellent performance, including a wide sensing range (0–60 kPa), high sensitivity (1.45 kPa⁻¹, 0–10 kPa), and stable responses over 410 cycles. The working mechanism of the MACF sensor is discussed in detail. Notably, the sensor maintains stable sensing performance under extreme humidity (40–80 RH%) and temperature conditions (20–100 °C). Furthermore, the sensor successfully detects and differentiates various human physiological signals, such as finger movements and wrist pulses. This study presents a simple fabrication method that achieves a balance between sensitivity and sensing range in cotton fabric-based sensors, demonstrating promising potential for applications in flexible wearable devices, electronic skins, and bionic robots.