A novel hierarchical metamaterial with tunable negative Poisson’s ratio is designed by a re-entrant representative unit cell (RUC), which consists of star-shaped subordinate cells. The in-plane mechanical behaviors of star-re-entrant hierarchical metamaterial are studied thoroughly by finite element method, non-dimensional effective moduli and effective Poisson’s ratios (PR) are obtained, then parameters of cell length, inclined angle, thickness for star subordinate cell as well as the amount of subordinate cell along x, y directions for re-entrant RUC are applied as adjustable design variables to explore structure-property relations. Finally, the effects of the design parameters on mechanical behavior and relative density are systematically investigated, which indicate that high specific stiffness and large auxetic deformation can be remarkably enhanced and manipulated through combining parameters of both subordinate cell and parent RUC. It is believed that the new hierarchical metamaterial reported here will provide more opportunities to design multifunctional lightweight materials that are promising for various engineering applications.

Recycling aluminosilicate-based solid wastes is imperative to realize the sustainable development of constructions. By using alkali activation technology, aluminosilicate-based solid wastes, such as furnace slag, fly ash, red mud, and most of the bio-ashes, can be turned into alternative binder materials to Portland cement to reduce the carbon footprint of the construction and maintenance activities of concrete structures. In this paper, the chemistry involved in the formation of alkali-activated materials (AAMs) and the influential factors of their properties are briefly reviewed. The commonly used methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), nuclear magnetic resonance spectroscopy (NMR), and X-ray pair distribution function technology, to characterize the microstructure of AAMs are introduced. Typical characterization results of AAMs are shown and the limitations of each method are discussed. The main challenges, such as shrinkage, creep, efflorescence, carbonation, alkali–silica reaction, and chloride ingress, to conquer for a wider application of AAMs are reviewed. It is shown that several performances of AAMs under certain circumstances seem to be less satisfactory than traditional portland cement systems. Existing strategies to improve these performances are reviewed, and recommendations for future studies are given.

Phosphogypsum (PG) is an industrial waste from the production of phosphoric acid and phosphate fertilizer. Disposal and landfill of PG pose significant environmental problems due to its hazardous components. Although many researchers have explored the possibility of PG recycling, challenges still exist before it can be high-effectively reused. In particular, a great deal of recent attention has been attracted to explore using PG as raw material to manufacture sustainable composites. The impurities movement, recycling efficiency, and environmental impacts have to be further investigated. This review article summarized the state of the art of the purification process, application areas, and the environmental impacts of PG waste. The main challenges and potential application approaches were discussed. This article is focused on reviewing the details of the PG reusing which benefits the readers on learning the knowledge from previous efforts. The main challenges of reusing PG were discussed from the chemical, physical, and materials perspectives.

Due to its high power, high efficiency, low pollution, and compact size, permanent-magnet synchronous motors (PMSMs) have been widely used in a variety of fields, including electric vehicles, aerospace, wind turbines, and marine devices, which are used in renewable, sustainable, and environmentally friendly energy resources. However, in these practical scenarios, the motor operating conditions are complex and variable. Under high-temperature and high-current conditions, PMSMs may experience demagnetization failures, not only leading to performance degradation but also inducing unexpected failures of the motors. To reduce the risk of unexpected losses caused by demagnetization faults and improve the safety and reliability of motor systems, it is necessary to apply automated monitoring of the magnet flux of the motor’s permanent magnets and achieve real-time diagnosis of early demagnetization faults, ensuring the safe operation of the motor. This review article tries to summarize the current detection methods of the automated monitoring of demagnetization faults in PMSMs. The main online monitoring technologies from both practical and academic perspectives are summarized and their benefits and challenges are reviewed. Finally, the research trends and suggestions for future improvements are provided. This review article not only sheds light on the origins of the automated monitoring of demagnetization faults but also helps to design highly effective and sustainable permanent-magnet synchronous motors.