The diverse and fascinating properties of transition metal oxides stem from the strongly correlated electronic degrees of freedom; the scientific challenge and range of possible applications of these materials have caused fascination among physicists and materials scientists, thus capturing research efforts for nearly a century. Here, we focus on the binary V x O y and the ternary perovskite AVO3 and review the key aspects from the underlying physical framework and their basic properties, recent strides made in thin-film synthesis, to recent efforts to implement vanadium-based oxides for practical applications that augment existing technologies, which surpass limitations of conventional materials.

Considered as a less hazardous piezoelectric material, potassium sodium niobate (KNN) has been in the fore of the search for replacement of lead (Pb) zirconate titanate for piezoelectrics applications. Here, we challenge the environmental credentials of KNN due to the presence of ~60 wt% Nb2O5, a substance much less toxic to humans than Pb oxide, but whose mining and extraction cause significant environmental damage.

Electronic performance in semiconducting polymers has improved dramatically in recent years owing to a host of novel materials and processing techniques. Our understanding of the factors governing charge transport in these materials has also been enhanced through advancements in both experimental and computational techniques, with disorder appearing to play a central role. In this prospective, we propose that disorder is an inextricable aspect of polymer morphology which need not be highly detrimental to charge transport if it is embraced and planned for. We discuss emerging guidelines for the synthesis of polymers which are resilient to disorder and present our vision for how future advances in processing and molecular design will provide a path toward further increases in charge-carrier mobility.

Robust evidences are presented showing that the Raman mode around 250 cm−1 in the Sb2Se3 thin films does not belong to this binary compound. The laser power density dependence of the Raman spectrum revealed the formation of Sb2O3 for high values of laser intensity power density excitation under normal atmospheric conditions. To complement this study, the Sb2Se3 films were characterized by x-ray diffraction during in situ annealing. Both these measurements showed that the Sb2Se3 compound can be replaced by Sb2O3. A heat-assisted chemical process explains these findings. Furthermore, Raman conditions required to perform precise measurements are described.

Due to the special crystal structures and electron configurations, high-entropy alloys (HEAs) are expected to have favorable activities for electrocatalytic reactions. In this paper, a set of oxygen evolution reaction (OER) criteria are applied for the HEA-based electrocatalyst design. Specifically, FeNiMnCrCu HEA is predicted to have a better OER performance than the baseline FeCoNiCrAl HEA. To demonstrate this design approach, both FeNiMnCrCu and FeCoNiCrAl samples are prepared and tested. Their crystal structures and electrocatalytic performance are examined. This paper demonstrates the potential of using finely tuned HEAs for OER applications.

The separation of oil–water mixtures is a widely utilized unit operation, used for handling a wide variety of mixtures from industry including: petroleum drilling and refining, fracking, waste-water treatment, mining, metal fabrication and machining, textile and leather processing, and rendering. Membrane-based methods have become increasingly attractive for the separation of oil–water mixtures because they are relatively energy-efficient, can be readily used to separate a variety of industrial feed streams, and provide consistent permeate quality. In this perspective, we discuss the design strategies for membranes with selective wettability i.e., membranes that are either selectively wet by, or prevent wetting by, the oil or water phase. The design strategies include the parameterization of two important physical characteristics: the surface porosity and the breakthrough pressure. We also discuss how they are related for membranes with a periodic geometry. On the basis of this understanding, we explore principles that allow for the systematic design of membranes with selective wettability. A review of the current literature on the separation of oil–water mixtures using membranes with differing wettabilities is also presented. Finally, we conclude by discussing the current challenges and outlook for the future of the field.

The current COVID-19 pandemic has caused the shortage of personal protective equipment (PPE) where improvised manufacturing in particular 3D printing has addressed many needs. This prospective discusses the current global crisis, then follows the wide interest in addressing the shortage of medical devices and PPEs used for treatment and protection against pathogens. An overview of the 3D printing process with polymer materials is given followed by the different 3D printing projects of PPEs and medical devices that emerged for the pandemic (including validation/testing). The potential for rapid prototyping with different polymer materials and eventual high-throughput production is emphasized.

Rechargeable magnesium (Mg) battery has been considered as a promising candidate for future battery generations because of its potential high-energy density, its safety features and low cost. The challenges lying ahead for the realization of Mg battery in general are to develop proper electrolytes fulfilling a multitude of requirements and to discover cathode materials enabling high-energy Mg batteries. The combination of Mg anode with a sulfur cathode is one of the promising electrochemical couples due to its advantages of safety, low costs, and a high theoretical energy density of over 3200 Wh/L. However, the research on magnesium–sulfur (Mg–S) battery is just at its beginning and the development of suitable electrolytes has been the key challenge for further improvement, and, thus, in the focus of recent research. In this review, we highlight the recent progress achieved in Mg electrolytes and Mg–S batteries and discuss the major technical issues, which must be resolved for the improvement of Mg–S batteries.

By solving the problems in the previous pragmatic method [Scr. Mater.90–91, 53–56 (2014)] and including the interdiffusion flux as the criteria, an augmented numerical inverse method was proposed and realized in a house-made code. The proposed augmented numerical inverse method was successfully applied to high-throughput determination of the composition-dependent interdiffusivities in different solid solution alloys ranging from binary, ternary to multicomponent systems by using a single diffusion couple. Moreover, the advance features of the augmented numerical inverse method were also demonstrated.

More than two decades of III-N materials research has led to the production of visible spectrum commercial light-emitting diodes (LEDs) and laser diodes (LDs). Commercial c-plane LEDs are currently limited by efficiency droop which describes the decline in efficiency with increasing input current density. Laser-based sources, however, provide peak efficiencies at much higher current densities and may circumvent efficiency droop limitations. The potential benefits of non-basal plane (NBP) orientations could accelerate the evolution of solid-state lighting from LED to LD sources. Here, we review the progress in long-wavelength (440–590 nm) NBP quantum well LD research and discuss applications in solid-state lighting, visible light communication and smart lighting.

Low-propagation-loss silicon wire waveguides are key components of optical integrated circuits. In this paper, we clarified, through assessment of the relationship between waveguide loss and fabrication technology that high-resolution lithography and an adjusted lithography process window are important for low-loss waveguides. The silicon wire waveguides fabricated by high-resolution lithography technology using ArF immersion lithography process showed world-record low propagation losses of 0.40 dB/cm for the C-band and 1.28 dB/cm for the O-band. Analysis with Barwicz and Haus's theory indicated that sidewall scattering is the main cause of propagation loss even in such low-loss waveguides.

There is a genuine need to shorten the development period for new materials with desired properties. In this work, machine learning (ML) was conducted on a dataset of the elastic moduli of 219 bulk-metallic glasses (BMGs) and another dataset of the critical casting diameters (Dmax) of 442 BMGs. The resulting ML model predicted the moduli and Dmax of BMGs in good agreement with most experimentally measured values, and the model even identified some errors reported in the literature. This work indicates the great potential of ML in design of advanced materials with target properties.

We use first-principles calculations based on density functional theory to investigate the interplay between oxygen vacancies, A-site cation size/tolerance factor, epitaxial strain, ferroelectricity, and magnetism in the perovskite manganite series, AMnO3 (A = Ca2+, Sr2+, Ba2+). We find that, as expected, increasing the volume through either chemical pressure or tensile strain generally lowers the formation energy of neutral oxygen vacancies consistent with their established tendency to expand the lattice. Increased volume also favors polar distortions, both because competing rotations of the oxygen octahedra are suppressed and because Coulomb repulsion associated with cation off-centering is reduced. Interestingly, the presence of ferroelectric polarization favors ferromagnetic (FM) over antiferromagnetic (AFM) ordering due to suppressed AFM superexchange as the polar distortion bends the Mn–O–Mn bond angles away from the optimal 180°. Intriguingly, we find that polar distortions compete with the formation of oxygen vacancies, which have a higher formation energy in the polar phases; conversely the presence of oxygen vacancies suppresses the onset of polarization. In contrast, oxygen vacancy formation energies are lower for FM than AFM orderings of the same structure type. Our findings suggest a rich and complex phase diagram, in which defect chemistry, polarization, structure, and magnetism can be modified using chemical potential, stress or pressure, and electric or magnetic fields.

Melanin (from the Greek μέλας, mélas, black) is a biopigment ubiquitous in flora and fauna, featuring broadband optical absorption, hydration-dependent electrical response, ion-binding affinity as well as antioxidative and radical-scavenging properties. In the human body, photoprotection in the skin and ion flux regulation in the brain are some biofunctional roles played by melanin. Here we discuss the progress in melanin research that underpins emerging technologies in energy storage/conversion, ion separation/water treatment, sunscreens, and bioelectronics. The melanin research aims at developing approaches to explore natural materials, well beyond melanin, which might serve as a prototype benign material for sustainable technologies.

Conjugated polymers are being considered for use at the interface between hard inorganic metallic and semiconducting electrodes and soft biological tissues. These organic materials have properties that are intermediate to these two extremes, and their chemistry, structure, and performance can be precisely manipulated over a large range. Examples of current interest included copolymers of poly(3,4-ethylene dioxythiophene) and poly(3,4-propylene dioxythiophene). This paper will review past efforts, recent activities, and future possibilities in this rapidly expanding area of materials research and technology.

Depolymerizable polymers are stimuli-responsive materials triggered to depolymerize rapidly and completely into their constituent monomers on command. Applications include triggerable vehicles for controlled release, restructurable materials, disappearing or sacrificial composites, and lithographic resists. Owing to their widespread utility, significant efforts have aimed to prepare and explore depolymerizable polymers and their corresponding triggers. This “Prospective” highlights advances since their discovery over a half-century ago, discusses methods in their preparation, and presents recent developments in triggered depolymerization. It also surveys applications that harness these polymers’ unique properties, while offering insights into research directions that may contribute to progress in this dynamic field.

Biogenic minerals often contain inorganic and organic impurities that are believed to harden and toughen the material. However, because of the complexity of these systems, it is difficult to deconvolute the effect of each of these impurities on the hardness of the material. We have created single-crystal samples with a range of magnesium concentrations and measured their hardness while controlling for orientation. We find that hardness increases linearly with magnesium content and that magnesium impurities could account for ~20% of the increased hardness in biogenic calcite from the mollusk Atrina rigida when compared with pure geologic calcite.

Silver nanoparticle inks printed on temperature-sensitive substrates can be converted into structures with high electrical conductivities within fractions of a second by photonic flash sintering. The key principle is the selective heating of the ink by the absorption of strongly focused pulsed light for which the substrate is transparent. The influence of process parameters like intensity and flashing frequency on the sintering speed is investigated. Furthermore, a setup is demonstrated for monitoring the temperature development in an ink during flash sintering, revealing that the substrate's glass transition point is exceeded only for very short time intervals, which prevents deformation.

Nanostructured cerium oxide (CeO2) with outstanding physical and chemical properties has attracted extensive interests over the past few decades in environment and energy-related applications. With controllable synthesis of nanostructured CeO2, much more features were technologically brought out from defect chemistry to structure-derived effects. This review highlights recent progress on the synthesis and characterization of nanostructured ceria-based materials as well as the traditional and new applications. Specifically, several typical applications based on the desired ceria nanostructures are focused to showcase the importance of nanostructure-derived effects. Moreover, some challenges and perspectives on the nanostructured ceria are presented, such as defects controlling and retainment, scale-up fabrication, and monolithic devices. Hopefully, this review can provide an improved understanding of nanostructured CeO2 and offer new opportunities to promote the further research and applications in the future.

Composites are ubiquitous throughout nature and often display both high strength and toughness, despite the use of simple base constituents. In the hopes of recreating the high-performance of natural composites, numerical methods such as finite element method (FEM) are often used to calculate the mechanical properties of composites. However, the vast design space of composites and computational cost of numerical methods limit the application of high-throughput computing for optimizing composite design, especially when considering the entire failure path. In this work, the authors leverage deep learning (DL) to predict material properties (stiffness, strength, and toughness) calculated by FEM, motivated by DL's significantly faster inference speed. Results of this study demonstrate potential for DL to accelerate composite design optimization.