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Layered MAX phases possess distinctive chemical, physical, electrical, and mechanical properties due to their amalgamation of metallic and ceramic characteristics. Understanding the corrosion mechanisms of MAX phases in various extreme environments is crucial. This paper commenced by scrutinizing synthesis techniques for MAX phase powders, thin films, and bulk materials, with a focus on fabrication processes and formation mechanisms. Subsequently, it delved into corrosion & oxidation mechanisms in diverse environments, emphasized their unique self-healing properties, and outlined future research directions. This comprehensive and systematic review aims to furnish researchers with effective guidance for selecting MAX phases based on different application environments. [ABSTRACT FROM AUTHOR]

The application of portable aluminum‐air batteries (AABs) in extreme environments is an inevitable demand for future development. Aqueous electrolyte freezing is a major challenge for low‐temperature operations. Conventionally, enlightened by the organic system in metal ion batteries, blindly increasing the concentration is regarded as an efficient technique to reduce the freezing point (FP). However, the underlying contradiction between the adjusting mechanism of the FP and OH− transportation is ignored. Herein, the aqueous alkali solution of CsOH is researched as a prototype to disclose the intrinsic conductive behavior and related solvent structure evolution. Different from these inorganic electrolyte systems, the concept of a critical anti‐freezing concentration (CFC) is proposed based on a specific temperature. The relationship between hydrogen bond reconstruction and de‐solvation behavior is analyzed. A high conductivity is obtained at −30 °C, which is also a recorded value in an intrinsic aqueous AAB. The homogenous dissolution of the Al anode is also observed. As a general rule, the CFC concept is also applied in both the KOH and NaOH systems. [ABSTRACT FROM AUTHOR]

The Hall-Petch strengthening coefficient of face-centered cubic alloys has the potential to increase. Herein, we experimentally determined an unconventionally large Hall-Petch coefficient equal to 1100 MPa·µm1/2 and a large lattice friction stress for novel Co0.95Cr0.8Fe0.25Ni1.8Mo0.475 high-entropy alloys (Mo0.475 HEAs). Detailed microstructural characterizations showed Mo segregation at grain boundaries (GBs) and no apparent nano-clustering in the matrix. With the increased Mo content, Mo segregating at GBs is an unexpected outcome. The unconventionally large Hall-Petch coefficient is ascribed to the newly generated effect due to Mo segregation at GBs, besides the factors in the grain interior, e.g. the increased solid-solution strengthening. This study is dedicated to enriching the diversity of Hall-Petch strengthening mechanisms for the development of high-strength materials. [ABSTRACT FROM AUTHOR]

The main bottleneck against industrial utilization of sodium ion batteries (SIBs) is the lack of high‐capacity electrodes to rival those of the benchmark lithium ion batteries (LIBs). Here in this work, we have developed an economical method for in situ fabrication of nanocomposites made of crystalline few‐layer graphene sheets loaded with ultrafine SnO2 nanocrystals, using short exposure of microwave to xerogel of graphene oxide (GO) and tin tetrachloride containing minute catalyzing dispersoids of chemically reduced GO (RGO). The resultant nanocomposites (SnO2@MWG) enabled significantly quickened redox processes as SIB anode, which led to remarkable full anode‐specific capacity reaching 538 mAh g−1 at 0.05 A g−1 (about 1.45 times of the theoretical capacity of graphite for the LIB), in addition to outstanding rate performance over prolonged charge–discharge cycling. Anodes based on the optimized SnO2@MWG delivered stable performance over 2000 cycles even at a high current density of 5 A g−1, and capacity retention of over 70.4% was maintained at a high areal loading of 3.4 mg cm−2, highly desirable for high energy density SIBs to rival the current benchmark LIBs. [ABSTRACT FROM AUTHOR]

Nb-doped TiO2 (NTO) thin films were sputtered on glass substrate followed by a simple annealing process in air. The photoelectric cooperative optimization was discussed based on the structural, optical and electrical characteristics. The influence of oxygen flow during deposition on materials chemistry and performance was analyzed. Hall measurement showed a strong dependence of transparent conductivity on the oxygen flow. Oxygen vacancies are related to the phase transitions from the rutile to anatase TiO2 during annealing. The chemical states of Nb, Ti and O before and after annealing were discussed. The achievement of optimized transparent conductivity was resultant from the fine-tuning of the doped chemistry and special interplay of dopants and host lattice. [ABSTRACT FROM AUTHOR]