Current Opinion in Solid State & Materials Science最新文献

The concept of alloying has evolved over the centuries and in the past decade and a half, the emergence of the high entropy alloying concept has completely changed our perception of alloy design. This alloying strategy has been found to exhibit exciting properties such as high strength, excellent corrosion resistance, high cryogenic fracture toughness, thermal stability, and irradiation resistance. While the fcc-structured equiatomic CrMnFeCoNi has been very popular over the years, the discovery of the superior properties by a ternary CoNiCr alloy, kick-started a new era for medium-entropy alloy-focused research in the last 5–10 years due to the realization that “medium is better”. Here we review the recent progress made in the development of medium entropy alloys from a binary CoNi building block (CoNi-M, where M is Fe, Cr, or V), which are prototype systems of medium-entropy alloys. We discuss the relationship between their microstructure and properties (mainly mechanical ones), and how the stacking fault energy, and/or short-range order (SRO) determines the corresponding deformation mechanism. The influence of minor-alloying on their crystal structure and variations in deformation modes are critically discussed. Lastly, some insights and challenges are outlined.

One of the main challenges in the laser powder bed fusion (LPBF) process is making dense and defect-free components. These porosity defects are dependent upon the melt pool geometry and the processing conditions. Power-velocity (PV) processing maps can aid in visualizing the effects of LPBF processing variables and mapping different defect regimes such as lack-of-fusion, under-melting, balling, and keyholing. This work presents an assessment of existing analytical equations and models that provide an estimate of the melt pool geometry as a function of material properties. The melt pool equations are then combined with defect criteria to provide a quick approximation of the PV processing maps for a variety of materials. Finally, the predictions of these processing maps are compared with experimental data from the literature. The predictive processing maps can be computed quickly and can be coupled with dimensionless numbers and high-throughput (HT) experiments for validation. The present work provides a boundary framework for designing the optimal processing parameters for new metals and alloys based on existing analytical solutions.

Titanium (Ti) and its alloys are attractive for a wide variety of structural and functional applications owing to excellent specific strength, toughness and stiffness, and corrosion resistance. However, if exposed to hydrogen sources, these alloys are susceptible to hydride formation in the form of TiH_x (0 < x ≤ 2), leading to crack initiation and mechanical failure due to lattice deformation and stress accumulation. The kinetics of the hydriding process depends on several factors, including the critical saturation threshold for hydrogen within Ti, the specific interaction of hydrogen with protective surface oxide, the rates of mass transport, and the kinetics of nucleation and phase transformation. Unfortunately, key knowledge gaps and challenges remain regarding the details of these coupled processes, which take place across vast ranges of time and length scales and are often difficult to probe directly. This work reviews recent advances in multiscale characterization and modeling efforts in Ti hydriding. We identify unanswered questions and key challenges, propose new perspectives on how to solve these remaining issues, and close knowledge gaps by discussing and demonstrating specific opportunities for integrating advanced characterization and multiscale modeling to elucidate chemistry and composition, microstructure phenomena, and macroscale performance and testing.

The emergence and spread of antimicrobial resistance call for the development of antibacterial substances that may be able to circumvent the resistance mechanisms of bacteria. To this end, intensive research efforts have been directed toward non-antibiotic materials with antibacterial potency. In particular, single-element inorganic nanomaterials have demonstrated promising activity against bacteria, and prominent examples of single-element inorganic nanomaterials include silver (Ag) nanoparticles, 0-, 1- and 2-dimensional carbon nanomaterials, and 2-dimensional black phosphorous (BP) nanosheets. With activity modes distinct from those of commercial antibiotics, these single-element inorganic nanomaterials have demonstrated activity against antibiotic-resistant bacterial strains and may delay the emergence of resistance in bacteria. In this review, we focus on silver (Ag) nanoparticles, 0-, 1- and 2-dimensional carbon nanomaterials, and 2-dimensional black phosphorous (BP) nanosheets, and discuss their antibacterial potency, factors that influence their antibacterial performances, as well as their cytotoxicity to mammalian cells.

Mucus is an essential barrier material that separates organisms from the outside world. This slippery material regulates the transport of nutrients, drugs, gases, and pathogens toward the cell surface. The surface of the cell itself is coated in a mucus-like barrier of glycoproteins and glycolipids. Mucin glycoproteins are the primary component of mucus and the epithelial glycocalyx. Aberrant mucin production is implicated in diverse disease states from cancer and inflammation to pre-term birth and infection. Biological mucins are inherently heterogenous in structure, which has challenged understanding their molecular functions as a barrier and as biochemically active proteins. Therefore, many synthetic materials have been developed as artificial mucins with precisely tunable structures. This review highlights advances in design and synthesis of artificial mucins and their application in biomedical studies of mucin chemistry, biology, and physics.

Manipulating self-assembled structures through shape-control of constitute particles is a fascinating yet quite challenging route to make new functional materials that can be used in a variety of applications. Toward this goal, the physics underlying the relation between the shape of constitute building blocks and their self-assembled structures (shape-structure relation) is the key and need to be better understood first. With the advances in particle fabrication techniques, our library of available anisotropic building blocks has expanded enormously, which opens up new opportunities for studying the shape-structure relation. There have been extensive studies performed to explore the self-assembly of anisotropic building blocks and tremendous progress has been made. In this mini-review, we will report recent progress on the self-assembly of non-spherical colloids both in experiments and in simulations. We focus on the self-assembly of polygonal platelets with a variety of shapes in two dimensions including regular polygonal shapes and a specific type of shape, kite-shape. Associated models that are helpful to understand the shape-structure relation are also summarized. We conclude this review with a brief discussion of current challenges in the field.

Cellulose nanocrystals are natural nanomaterials with a high aspect ratio, high specific area, excellent stability, and favorable optical performances. Cellulose nanocrystals can form cholesteric liquid crystals through a left-handed spiral arrangement. The suspension liquid of cellulose nanocrystals can retain the chiral cholesteric structure in the solid film after being completely dried, leading to the appearance of Bragg reflection and bright structural color in the visible spectrum. By changing the conditions or mixing with polymers, the cellulose nanocrystals film will show different structural colors due to the change of pitch. The film can cover almost the entire visible spectrum, which can be applied to various aspects such as sensing, anti-counterfeiting, detection, and so on. In this review, we elaborated on the synthesis and properties of cellulose nanocrystals materials and introduced the mechanism of structural color formation, as well as the current research progress and applications. Cellulose nanocrystals have become a hot spot in the field of structural color, and provide more research value for providing a cheap, easy-to-obtain, green-friendly, and high-biocompatibility natural photonic material.

The Glass Genome has only started to be explored. To advance the next generation design of glasses, both physics-informed and data-driven models must be widely available and understood. The most common difficulty in materials modeling is determining which are the simplest approaches appropriate for understanding and predicting key properties. The structure and properties of any material, including its thermodynamics and kinetics, originate from its underlying statistical mechanics. In this work, we present a tutorial view of statistical mechanical modeling of glass, covering structural predictions, structure-property relationships, and the complex kinetics of the glass-forming systems. While the approach presented herein is general and can be applied to any liquid or glassy system, we select calcium silicates as a specific example for this step-by-step review. We hope that this tutorial will be especially beneficial to those who are new to the modeling of glass-forming materials. A list of open questions related to the modeling techniques is also discussed.