Journal of Materiomics最新文献

Transition metal nitrides (TMNs) have gained widespread application in protecting structural components due to their high strength and hardness. However, TMNs still have the challenge of structural instability and mechanical deterioration caused by oxidation under harsh high temperature conditions. Herein, we present a strategy combining component regulation with high-entropy engineering to develop an advanced high-temperature Al-containing high-entropy nitrides (HENs) material. To prevent the phase decomposition of AlN within the (NbMoTaWAl)N, theoretical simulations were employed to determine a critical atomic percent of 25.0% Al for maintaining the stability of the high-entropy structure. Ensuing experimental synthesis creates three NbMoTaWAlN films with varying Al content: a high-entropy film with 0.0% Al (HEN), a high-entropy film with 21.2% Al (HEN-Al), and an amorphous transition metal nitride film with 30.2% Al (a-TMN-Al), validating key high-entropy engineering benchmarks. It is found that the unique HEN-Al film exhibits excellent oxidation resistance and high-temperature hardness, attributed to the uniform distribution of Al atoms in the robust high-entropy structure, which creates conditions for forming a dense and continuous Al₂O₃ barrier layer, effectively hindering the diffusion of oxygen into the film interior. This study provides new insights to develop a new generation of high-temperature protective materials.

Homogeneous void nucleation in metals containing arbitrary vacancies and interstitials has been reexamined, with corrections made to the original work by Katz and Wiedersich. The void size distributions derived previously missed an exponential modification function with void size as the exponent. As a result, void nucleation under a given vacancy supersaturation ratio is underestimated by orders of magnitude. The second improvement arises from the accuracy in calculating the vacancy arrival rate to a void. The present work proposes establishing a direct relationship between the vacancy arrival rate and the available self-diffusion coefficient. With these corrections and improvements, void nucleation in pure Fe is calculated as an example, and an analytic fitting formula is provided. The required vacancy supersaturation ratio and interstitial-to-vacancy flux ratio for void nucleation calculations can be easily obtained from an analytical solution of rate theory calculations, in which dislocation density and displacements per atom (dpa) rate are adjustable inputs. Alternatively, the nucleation rate calculation can be incorporated into rate theory calculations considering evolving dislocation densities, which leads to time-dependent void nucleation.

SrTi₂O₅ particles were claimed by Panda et al. in J. Materiomics 2023; 9:609 as a new lead-free ferroelectric material with orthorhombic symmetry and space group of Cmm2, being, therefore, employed as a base of piezoelectric energy harvesters. However, in this comment we express concerns regarding the presence of the piezoelectricity in the studied material and the interpretation of the structural, microstructural, and ferroelectric results in that publication as those associated with SrTi₂O₅. We also note that the presented dielectric results are contradictory and that many important details are missing.

Metasurface significantly enriches the light-matter interaction and promotes the development of planar optics. In recent years, with the rapid advancements of terahertz (THz) technology, THz devices with switchable and reconfigurable functions have been intensively pursued. Liquid crystal (LC), a unique soft matter that combines the fluidity of liquids and the order of crystals, is now indispensable in displays and spatial light modulations. LC is integrated with metasurfaces to realize dynamic THz devices and apparatuses as well. This review summarizes the research progress in LC based THz metadevices in three different respects: LC planar THz devices, LC integrated metal metasurfaces, and LC integrated dielectric metasurfaces. Various technologies for fabrications of LC microstructures and integrations of LCs with metal or dielectric metasurfaces are presented. The obtained LC metadevices exhibit excellent responsiveness to external stimulus such as electric fields, magnetic fields, heat, and light. By this means, the amplitude, frequency, phase as well as polarization of THz waves are dynamically manipulated. The LC based tunable THz metadevices will significantly improve THz applications in imaging, communication, and sensing.

Metadevices have emerged as a new element or system in recent years, from optics to mechanical science, showing superior performance and powerful application potential. In this study, a mechanical metadevice that capable of low-frequency vibration isolation, which is called metamaterial springs or metasprings, is proposed. Meanwhile, a modular design method is reported to obtain the customizable quasi-zero stiffness characteristic of the designed metaspring. As proof-of-concept, we demonstrate, both in simulations and experiments, the quasi-zero stiffness characteristics of the proposed metasprings using 3D-printed experimental specimens. Moreover, the low-frequency vibration isolation properties of the proposed metasprings is demonstrated both in vibration tests and automotive vibration tests. This work provides a new mechanical metadevice, that is, metasprings for low-frequency vibration isolation, as well as a modular design method for designing metasprings, which may revolutionize vibration isolation devices in the field of low-frequency vibration isolation.