Al-containing MAX phase ceramic has demonstrated great potential in the field of high-performance low-voltage electrical contact material. Elucidating the anti-arc erosion mechanism of the MAX phase is crucial for further improving performance, but it is not well-understood. In this study, Ag/Ti₃AlC₂ electrical contact material was synthesized by powder metallurgy and examined by nanoindentation techniques such as constant loading rate indentation, creep testing, and continuous stiffness measurements. Our results indicated a gradual degradation in the nano-mechanical properties of the Ti₃AlC₂ reinforcing phase with increasing arc erosion times, although the rate of this degradation appeared to decelerate over arc erosion times. Specifically, continuous stiffness measurements highlighted the uneven mechanical properties within Ti₃AlC₂, attributing this heterogeneity to the phase’s decomposition. During the early (1–100 times) and intermediate (100–1000 times) stages of arc erosion, the decline in the nano-mechanical properties of Ti₃AlC₂ was primarily ascribed to the decomposition of Ti₃AlC₂ and limited surface oxidation. During the later stage of arc erosion (1000–6200 times), the inner region of Ti₃AlC₂ also sustained arc damage, but a thick oxide layer formed on its surface, enhancing the mechanical properties and overall arc erosion resistance of the Ag/Ti₃AlC₂.

One-dimensional (1D) metals are highly conductive and tend to form networks that facilitate electron hopping and migration. Hence, they have tremendous potential as microwave-absorbing (MA) materials. Traditionally, 1D metals are mainly precious metals such as gold, silver, nickel, and their preparation methods often have low yield and are not environmentally friendly, which has limited the exploration in this area. Herein, the unique nanolaminate structure and chemical bond characteristics of Ti₂SnC MAX phase is successfully taken advantages for large-scale preparation of Sn whiskers, and then, core-sheath Sn/SnO_x heterojunctions are obtained by simply annealing at different temperatures. The heterojunction annealed at 500 ℃ possesses favorable MA performance with an effective absorption bandwidth of 5.3 GHz (only 1.7 mm) and a minimum reflection loss value of −51.97 dB; its maximum radar cross section (RCS) reduction value is 29.59 dB·m², confirming its excellent electromagnetic wave attenuation ability. Off-axis electron holography is used to visually characterize the distribution of charge density at the cylindrical heterogenous interface, confirming the enhanced interfacial polarization effect. Given the diversity of MAX phases and the advantages of the fabrication method (e.g., green, inexpensive, and easily scalable), this work provides significant guidance for the design of 1D metal-based absorbers.

The achievement of chemical diversity and performance regulation of MAX phases primarily relies on solid solution approaches. However, the reported A-site solid solution is undervalued due to their expected chemical disorder and compliance with Vegard’s law, as well as discontinuous composition and poor purity. Herein, we synthesized high-purity Ti₂(Sn_xAl_1−x)C (x = 0–1) solid solution by the feasible pressureless sintering, enabling us to investigate their property evolution upon the A-site composition. The formation mechanism of Ti₂(Sn_xAl_1−x)C was revealed by thermal analysis, and crystal parameters were determined by Rietveld refinement of X-ray diffraction (XRD). The lattice constant (a) adheres to Vegard’s law, while the lattice constant (c) and internal free parameter (z_M) have noticeable deviations from the law, which is caused by the significant nonlinear distortion of Ti₆C octahedron as Al atoms are substituted by Sn atoms. Also, the deviation also results in nonlinear changes in their physicochemical properties, which means that the solid solution often exhibits better performance than end members, such as hardness, electrical conductivity, and corrosion resistance. This work offers insights into the deviation from Vegard’s law observed in the A-site solid solution and indicates that the solid solution with enhanced performance may be obtained by tuning the A-site composition.

MAX phases (Ti₃SiC₂, Ti₃AlC₂, V₂AlC, Ti₄AlN₃, etc.) are layered ternary carbides/nitrides, which are generally processed and researched as structure ceramics. Selectively removing A layer from MAX phases, MXenes (Ti₃C₂, V₂C, Mo₂C, etc.) with two-dimensional (2D) structure can be prepared. The MXenes are electrically conductive and hydrophilic, which are promising as functional materials in many areas. This article reviews the milestones and the latest progress in the research of MAX phases and MXenes, from the perspective of ceramic science. Especially, this article focuses on the conversion from MAX phases to MXenes. First, we summarize the microstructure, preparation, properties, and applications of MAX phases. Among the various properties, the crack healing properties of MAX phase are highlighted. Thereafter, the critical issues on MXene research, including the preparation process, microstructure, MXene composites, and application of MXenes, are reviewed. Among the various applications, this review focuses on two selected applications: energy storage and electromagnetic interference shielding. Moreover, new research directions and future trends on MAX phases and MXenes are also discussed.