Pseudopolymorphic Phase Engineering for Improved Thermoelectric Performance in Copper Sulfides.

Polymorphism (and its extended form - pseudopolymorphism) in solids is ubiquitous in mineralogy, crystallography, chemistry/biochemistry, materials science, and the pharmaceutical industries. Despite the difficulty of controlling (pseudo-)polymorphism, the realization of specific (pseudo-)polymorphic phases and associated boundary structures is an efficient route to enhance material performance for energy conversion and electromechanical applications. Here, this work applies the pseudopolymorphic phase (PP) concept to a thermoelectric copper sulfide, Cu S (x ≤ 0.

Nanoscale ductile fracture and associated atomistic mechanisms in a body-centered cubic refractory metal.

Understanding the competing modes of brittle versus ductile fracture is critical for preventing the failure of body-centered cubic (BCC) refractory metals. Despite decades of intensive investigations, the nanoscale fracture processes and associated atomistic mechanisms in BCC metals remain elusive due to insufficient atomic-scale experimental evidence. Here, we perform in situ atomic-resolution observations of nanoscale fracture in single crystals of BCC Mo.

Direct observation of tensile-strain-induced nanoscale magnetic hardening.

Magnetoelasticity is the bond between magnetism and mechanics, but the intricate mechanisms via which magnetic states change due to mechanical strain remain poorly understood. Here, we provide direct nanoscale observations of how tensile strain modifies magnetic domains in a ferromagnetic Ni thin plate using in situ Fresnel defocus imaging, off-axis electron holography and a bimetallic deformation device. We present quantitative measurements of magnetic domain wall structure and its transformations as a function of strain.

Is there more to bitcoin mining than carbon emissions?

Critics decry cryptocurrency mining as a huge waste of energy, while proponents insist on claiming that it is a green industry. Is Bitcoin mining really worth the energy it consumes? The high power consumption of cryptocurrency mining has become the latest global flashpoint. In this paper, we define the Mining Domestic Production (MDP) as a method to account for the final outcome of the Bitcoin mining industry's production activities in a certain period time, calculate the carbon emission per unit output value of the Bitcoin mining industry in China, and compare it with three other traditional industries.

Tracking the sliding of grain boundaries at the atomic scale.

Grain boundaries (GBs) play an important role in the mechanical behavior of polycrystalline materials. Despite decades of investigation, the atomic-scale dynamic processes of GB deformation remain elusive, particularly for the GBs in polycrystals, which are commonly of the asymmetric and general type. We conducted an in situ atomic-resolution study to reveal how sliding-dominant deformation is accomplished at general tilt GBs in platinum bicrystals.

A hybrid with distributed pooling blockchain protocol for image storage.

As a distributed storage scheme, the blockchain network lacks storage space has been a long-term concern in this field. At present, there are relatively few research on algorithms and protocols to reduce the storage requirement of blockchain, and the existing research has limitations such as sacrificing fault tolerance performance and raising time cost, which need to be further improved. Facing the above problems, this paper proposes a protocol based on Distributed Image Storage Protocol (DISP), which can effectively improve blockchain storage space and reduces computational costs in the help of InterPlanetary File System (IPFS).

Direct Atomic-Scale Observation of Ultrasmall Ag Nanowires that Exhibit fcc, bcc, and hcp Structures under Bending.

Metals usually have three crystal structures: face-centered cubic (fcc), body-centered cubic (bcc), and hexagonal-close packed (hcp) structures. Typically, metals exhibit only one of these structures at room temperature. Mechanical processing can cause phase transition in metals, however, metals that exhibit all the three crystal structures have rarely been approached, even when hydrostatic pressure or shock conditions are applied.

Atomistic Mechanism of Stress-Induced Combined Slip and Diffusion in Sub-5 Nanometer-Sized Ag Nanowires.

With continuous minimization of nanodevices, the dimensions of metallic materials used in nanodevices decrease to a few nanometers. Understanding the structural stability and deformation behavior of these small-sized metallic materials is important for their practical applications. Here we report our atomic-resolution observation of the deformation processes of Ag nanowires with widths of ∼3 nm.

Surface Energy Driven Liquid-Drop-Like Pseudoelastic Behaviors and In Situ Atomistic Mechanisms of Small-Sized Face-Centered-Cubic Metals.

The elastic strain of conventional metals is usually below ∼1%. As the metals' sizes decrease to approximate a few nanometers, their elastic strains can approach ∼8%, and they usually exhibit pseudoelastic strain that can be as large as ∼35%. Previous studies suggested that the pseudoelastic behaviors of nanocrystals were attributed to distinctive mechanisms, including the release of stored elastic energies, the temperature-enhanced surface diffusion, etc.

New twinning route in face-centered cubic nanocrystalline metals.

Twin nucleation in a face-centered cubic crystal is believed to be accomplished through the formation of twinning partial dislocations on consecutive atomic planes. Twinning should thus be highly unfavorable in face-centered cubic metals with high twin-fault energy barriers, such as Al, Ni, and Pt, but instead is often observed. Here, we report an in situ atomic-scale observation of twin nucleation in nanocrystalline Pt.

Mechanically Driven Grain Boundary Formation in Nickel Nanowires.

Metallic nanomaterials are widely used in micro/nanodevices. However, the mechanically driven microstructure evolution in these nanomaterials is not clearly understood, particularly when large stress and strain gradients are present. Here, we report the in situ bending experiment of Ni nanowires containing nanoscale twin lamellae using high-resolution transmission electron microscopy.

Size effect on the deformation mechanisms of nanocrystalline platinum thin films.

This paper reports a study of time-resolved deformation process at the atomic scale of a nanocrystalline Pt thin film captured in situ under a transmission electron microscope. The main mechanism of plastic deformation was found to evolve from full dislocation activity-enabled plasticity in large grains (with grain size d > 10 nm), to partial dislocation plasticity in smaller grains (with grain size 10 nm < d < 6 nm), and grain boundary-mediated plasticity in the matrix with grain sizes d < 6 nm. The critical grain size for the transition from full dislocation activity to partial dislocation activity was estimated based on consideration of stacking fault energy.