Current Opinion in Solid State & Materials Science最新文献

Heterostructured materials comprised of relatively soft/hard disparate phases typically exhibit composite strengthening but lack plastic deformability at ambient temperatures. However, heterostructured systems comprised of nanoscale phases can simultaneously enhance yield strength and strain hardening, thereby promoting uniform distribution of plastic flow. In this review, the atomic-scale deformation mechanisms in model systems of eutectic alloys, Al-Al₂Cu and Al-Si, refined to nanoscales via laser rapid solidification are discussed, and compared with literature on multi-component (high entropy) eutectics such as Ni-Al-Fe-based with Cr and/or Co additions. The nano-lamellar Al-Al₂Cu structures exhibit unit defect mechanisms not reported in monolithic Al₂Cu intermetallic: localized shear on {0 1 1} and shear-induced faults on {1 2 1} planes, constrained by closely-spaced dislocation arrays in Al confined by Al/Al₂Cu interfaces. The unexpected plasticity mechanisms are enabled by slip continuity in nanoscale Al-Al₂Cu eutectics associated with the orientation relationship and interface habit planes. In nano-fibrous Al-Si eutectic, tensile ductility at strength approaching 600 MPa is observed resulting from dislocation plasticity in the nano-Al channels and cracking in Si nanofibers. Molecular dynamics simulations show that Al dislocations easily cross-slip (screw) or climb (edge) along Al-Si interfaces, making slip transmission difficult. The propagation of nano-cracks is suppressed by surrounding strain hardening Al, retaining good ductility of the sample, in spite of lack of direct slip transmission. The critical unit mechanisms of slip transmission and interface-enabled plasticity observed in nanoscale eutectic binary systems can also explain the strength-ductility relationship in multi-component eutectics and homogeneously distributed plastic flow with increasing microstructural heterogeneity.

Recent advancements in electronics have renewed the interest in high strain rate nanoindentation testing, resulting in the development of new high strain rate nanoindentation test equipment and test methodologies. In this work, the current state-of-the-art in high strain rate nanoindentation testing is critically reviewed, with focus on three key aspects - the testing equipment's dynamic mechanical and electronic response, test methodology, and post-processing of raw data to obtain hardness and strain rate. The challenges in instrument hardware design and post-test data analysis are discussed, along with optimal strain rate window for accurate high strain rate measurements. Specific focus will be on instrumented high strain rate testing using self-similar indenters at strain rates in excess of 100 s⁻¹, wherein load and depth of penetration into the sample are both measured or applied.

2D materials are enabling disruptive advancements in electronic and photonic devices yielding to the development of sensing and wearable materials and in the field of energy production and storage as key components of photovoltaic technology and batteries. Nevertheless, little attention has been paid to TMDs and oxides that contain vanadium, as it is the case of vanadium disulfide (VS₂) and vanadium dioxide (VO₂). In this study we review the synthesis and characterization using Raman spectroscopy of VS₂ and its oxidized states. Laser-induced oxidation occurring during the Raman experiments in ambient conditions is described and plateau values of laser power levels to induce oxidation are provided. Furthermore, tip-enhanced Raman spectroscopy (TERS) spectra and maps are conducted to reveal at the single flake level the onset of oxidation mechanisms at the surface of the 2D platelets.

Optogenetic approaches enable light-mediated control of cellular activities using genetically encoded photoreceptors. While optogenetic technology is already well established in neuroscience and fundamental research, the implementation of optogenetic tools in bacteriology is still emerging. Engineered bacteria with the specific optogenetic system that function at the transcriptional or post-translational level can sense and respond to light, allowing optogenetic control of bacterial behaviors. In this review, we give a brief overview of available optogenetic systems, including their mode of action, classification, and engineering strategies, and focus on optogenetic control of bacterial behaviors with the highlight of strategies for use of optogenetic systems.

Powering wearable bioelectronics with decent skin conformability and wearing comfort is highly desired. Fiber batteries could provide an attractive alternative to traditional rigid ones and present a compelling solution to this problem. In this review, we will discuss the various classes of fiber batteries, including lithium batteries, zinc batteries, and other types of fiber batteries. We will then report the latest research progress on each battery category through its working mechanism, materials usage, structure design, and wearable applications. Finally, we provide insights into current challenges and future applications of fiber batteries, aiming to promote the development of low-cost and high-performance fiber battery technologies for wearable bioelectronics.

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.

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.