Annual Review of Materials Research - Current Issue

With the increasing global demand for net-zero carbon emissions, actions to address climate change have gained momentum among policymakers and the public. The urgent need for a sustainable economy is underscored by the mounting waste crisis in landfills and oceans. However, the proliferation of distributed electronic devices poses a significant challenge due to the resulting electronic waste. To combat this issue, the development of sustainable and environmentally friendly materials for these devices is imperative. Cellulose, an abundant and CO2-neutral substance with a long history of diverse applications, holds great potential. By integrating electrically interactive components with cellulosic materials, innovative biobased composites have been created, enabling the fabrication of bulk electroactive paper and the establishment of new, potentially more sustainable manufacturing processes for electronic devices. This review explores recent advances in bulk electroactive paper, including the fundamental interactions between its constituents, manufacturing techniques, and large-scale applications in the field of electronics. Furthermore, it addresses the importance and challenges of scaling up production of electroactive paper, highlighting the need for further research and development.

Molecular architectures known as bottlebrush polymers provide unique opportunities to tune the structure and properties of soft materials with applications ranging from rubbers to thin films and composites. This review addresses recent developments and future opportunities in the field with an emphasis on materials science enabled by contemporary bottlebrush chemistry.

Polymers undergoing controlled degradation are of significant current interest. Among the classes of degradable polymers, self-immolative polymers (SIPs) are attracting increasing attention due to their ability to completely depolymerize from end to end following the cleavage of their endcap or backbone. Their amplified responses to stimuli, along with their ability to readily tune the stimulus to which they respond by changing only their endcap, are useful features for a variety of applications. This review covers the major classes of SIPs, including poly(benzyl carbamate)s, poly(benzyl ether)s, polyphthalaldehydes, polyglyoxylates, polydisulfides, polythioesters, and their related derivatives along with their endcaps. Distinctive features of their syntheses and depolymerizations are discussed. Applications of SIPs including imaging and sensing, therapeutics, gels, micro- and nanopatterning, transient or recyclable materials, and adhesives are described. We conclude with some challenges and future perspectives for the field.

Polymer vesicles and lipid nanoparticles are supramolecular structures with similar physicochemical properties that are self-assembled from different amphiphilic molecules. Because of their efficient drug encapsulation capability, they are good candidates for drug delivery systems. In recent years, nanoparticles with different compositions, sizes, and morphologies have been applied to the delivery of a wide variety of different therapeutic molecules, such as nucleic acids, proteins, and enzymes; their remarkable chemical versatility allows for customization to specific biological applications. In this review, design approaches for polymer vesicles and lipid nanoparticles are summarized with representative examples in terms of their physicochemical properties (size, shape, and mechanical features), preparation strategies (film rehydration, solvent switch, and nanoprecipitation), and applications (with a focus on diagnosis, imaging, and RNA-based therapy). Finally, the challenges limiting the transition from laboratory to clinical application and future perspectives are discussed.

In chemistry and biochemistry, chirality represents the structural asymmetry characterized by nonsuperimposable mirror images for a material such as DNA. In physics, however, chirality commonly refers to the spin–momentum locking of a particle or quasiparticle in the momentum space. While seemingly disconnected, structural chirality in molecules and crystals can drive electronic chirality through orbital–momentum locking; that is, chirality can be transferred from the atomic geometry to electronic orbitals. Electronic chirality provides an insightful understanding of chirality-induced spin selectivity, in which electrons exhibit salient spin polarization after going through a chiral material, and electrical magnetochiral anisotropy, which is characterized by diode-like transport. It further gives rise to new phenomena, such as anomalous circularly polarized light emission, in which the light handedness relies on the emission direction. These chirality-driven effects will generate broad impacts for fundamental science and technology applications in spintronics, optoelectronics, and biochemistry.

This article examines recent advances in the field of antiferromagnetic spintronics from the perspective of potential device realization and applications. We discuss advances in the electrical control of antiferromagnetic order by current-induced spin–orbit torques, particularly in antiferromagnetic thin films interfaced with heavy metals. We also review possible scenarios for using voltage-controlled magnetic anisotropy as a more efficient mechanism to control antiferromagnetic order in thin films with perpendicular magnetic anisotropy. Next, we discuss the problem of electrical detection (i.e., readout) of antiferromagnetic order and highlight recent experimental advances in realizing anomalous Hall and tunneling magnetoresistance effects in thin films and tunnel junctions, respectively, which are based on noncollinear antiferromagnets. Understanding the domain structure and dynamics of antiferromagnetic materials is essential for engineering their properties for applications. For this reason, we then provide an overview of imaging techniques as well as micromagnetic simulation approaches for antiferromagnets. Finally, we present a perspective on potential applications of antiferromagnets for magnetic memory devices, terahertz sources, and detectors.

Lithium-ion batteries (LIBs) are now widely exploited for multiple applications, from portable electronics to electric vehicles and storage of renewable energy. Along with improving battery performance, current research efforts are focused on diminishing the levelized cost of energy storage (LCOS), which has become increasingly important in light of the development of LIBs for large transport vehicles and power grid energy storage applications. Since LCOS depends on the battery's lifetime, understanding the mechanisms responsible for battery degradation and developing strategies to increase the lifetime of LIBs is very important. In this review, the latest developments related to the performance and degradation of the most common LIBs on the market are reviewed. The numerous processes underlying LIB degradation are described in terms of three degradation loss modes: loss of lithium inventory (LLI), active positive electrode material loss and degradation, and active negative electrode material loss and degradation. A strong emphasis is placed on the most recent strategies and tactics for LIB degradation mitigation.

Beta-gallium oxide (β-Ga2O3) is a material with a history of research and development spanning about 70 years; however, it has attracted little attention as a semiconductor for a long time. The situation has changed completely in the last ten years, and the world has seen increasing demand for active research and development of both materials and devices. Many of its distinctive physical properties are attributed to its very large bandgap energy of 4.5 eV. Another important feature is that it is possible to grow large bulk single crystals by melt growth. In this article, we first discuss the important physical properties of β-Ga2O3 for electronic device applications, followed by bulk melt growth and thin-film epitaxial growth technologies. Then, state-of-the-art β-Ga2O3 transistor and diode technologies are discussed.

Current high-energy-density Li-ion batteries use stoichiometric Li 3d transition metal oxides as positive electrodes, which are conventionally described purely by transition-metal redox during routine operating windows. Their practical specific capacities (mAh/g) may be increased by widening their operational voltage window, using Li-excess compositions, or a combination of the two, both of which have shown increasing evidence of O participation in the charge-compensation mechanism. Understanding how this influences the electrochemical performance of these cathodes has been of great interest. Therefore, this review summarizes the current understanding of O participation in alkali-ion battery cathode charge compensation. Particular scrutiny is applied to the experimental observations and theoretical models used to explain the consequences of O participation in charge compensation. The charge-compensation mechanism of LiNiO2 is revisited to highlight the role of O hole formation during delithiation and is discussed within the wider context of Li-excess cathodes.

The fundamentals of our understanding of fatigue crack propagation were formed more than 60 years ago by Paul C. Paris. Since then, the run toward new metallic materials and alloys with ever finer-grained microstructures has had a large impact on research. Along with enormous variation of the microstructural length scales (i.e., grain size), the essential parameters for the description of fatigue crack growth, such as the crack propagation rate and plastic zone size, also exhibit an immense change from the subnanometer to the micrometer regime. These enormous variations in the fatigue crack growth behavior's controlling parameters motivate this contribution. This article presents an overview of the effect of grain size, from the millimeter to the nanometer grain-size regime, on fatigue crack propagation of mainly ductile metals and alloys with an attempt to summarize the most important findings and underlying physical phenomena, including with respect to selected materials such as pure iron, nickel, and austenitic and pearlitic steel.

Steel production accounts for approximately 8% of all global CO2 emissions, with the primary steelmaking route using iron ores contributing approximately 80% of those emissions, mainly due to the use of fossil-based reductants and fuel. Hydrogen-based reduction of iron oxide is an alternative for primary synthesis. However, to counteract global warming, decarbonization of the steel sector must proceed much faster than the ongoing transition kinetics in primary steelmaking. Insufficient supply of green hydrogen is a particular bottleneck. Realizing a higher fraction of secondary steelmaking is thus gaining momentum as a sustainable alternative to primary production. Steel production from scrap is well established for long products (rails, bars, wire), but there are two main challenges. First, there is not sufficient scrap available to satisfy market needs. Today, only one-third of global steel demand can be met by secondary metallurgy using scrap since many steel products have a lifetime of several decades. However, scrap availability will increase to about two-thirds of total demand by 2050 such that this sector will grow massively in the next decades. Second, scrap is often too contaminated to produce high-performance sheet steels. This is a serious obstacle because advanced products demand explicit low-tolerance specifications for safety-critical and high-strength steels, such as for electric vehicles, energy conversion and grids, high-speed trains, sustainable buildings, and infrastructure. Therefore, we review the metallurgical and microstructural challenges and opportunities for producing high-performance sheet steels via secondary synthesis. Focus is placed on the thermodynamic, kinetic, chemical, and microstructural fundamentals as well as the effects of scrap-related impurities on steel properties.