Materials Engineering Research

Shape memory alloys are a unique class of materials that are capable of large reversible deformations under external stimuli such as stress or temperature. The present study examines the phase transformations and mechanical responses of NiTi and NiTiHf shape memory alloys under the loading of a spherical indenter by using a finite element model. It is found that the indentation unloading curves exhibit distinct changes in slopes due to the reversible phase transformations in the SMAs. The normalized contact stiffness (F/S²) of the SMAs varies with the indentation load (depth) as opposed to being constant for conventional single-phase materials. The load-induced phase transformation that occurred under the spherical indenter was simulated numerically. It is observed that the phase transformation phenomenon in the SMA induced by an indentation load is distinctly different from that induced by a uniaxial load. A pointed indenter produces a localized deformation, resulting in a stress (load) gradient in the specimen. As a result, the transformation of phases in SMAs induced by an indenter can only be partially completed. The overall modulus of the SMAs varies continuously with the indentation load (depth) as the average volumetric fraction of the martensite phase varies. For NiTi (E_a > E_m), the modulus decreases with the depth, while for NiTiHf (E_a < E_m), the modulus increases with the depth. The predicted young modules during indentation modeling agree well with experimental results. Finally, the phase transformation of the SMAs under the indenter is not affected by the post-yield behavior of the materials.

Lithium-ion (Li-ion) batteries have become the leading energy storage technology, powering a wide range of applications in today's electrified world. This comprehensive review paper delves into the current challenges and innovative solutions driving the supercharged future of lithium-ion batteries. It scrutinizes the limitations of energy density in existing batteries, exploring advanced electrode materials and designs that promise higher capacity. Safety concerns take center stage, with a focus on cutting-edge thermal management systems and materials. The imperative of sustainable sourcing is addressed, highlighting alternative materials and recycling strategies for a greener supply chain. Transformative breakthroughs, such as solid-state electrolytes and emerging battery chemistries, offer glimpses of the future. The paper also examines the applications and market perspectives of lithium-ion batteries in electric vehicles, portable electronics, and renewable energy storage. It concludes by emphasizing the transformative potential of lithium-ion batteries in accelerating the energy revolution and paving the way for a sustainable energy future.

Although lithium-ion batteries have gained widespread use in high-performance and mobile industries, concerns about their safety due to the low boiling point of their organic liquid electrolyte have posed challenges to their further development. In response, solid polymer electrolytes have emerged as a promising alternative, characterized by low flammability, flexibility, and high safety relative to liquid electrolytes. However, commercialization has been hindered by limitations in Li-ion conductivity and mechanical properties. Recent research efforts have focused on addressing these limitations to improve the performance and safety of polymer-based Li-ion batteries. This review discusses the utilization of polymer materials to enhance battery safety and overcome previous challenges, with a particular emphasis on the design of robust artificial interfaces to increase battery stability. Furthermore, we discuss the prospects for the future of polymer-based battery industries.