Assessing the undrained strength cross-anisotropy of three tailings types

The cross-anisotropic nature of soil strength has been studied and documented for decades, including the increased propensity for cross-anisotropy in layered materials. However, current engineering practice for tailings storage facilities (TSFs) does not appear to generally include cross-anisotropy considerations in the development of shear strengths. This being despite the very common layering profile seen in subaerially-deposited tailings. To provide additional data to highlight the strength cross-anisotropy of tailings, high quality block samples from three TSFs were obtained and trimmed to enable Hollow Cylinder Torsional Shear tests to be sheared at principal stress angles of 0 and 45 degrees during undrained shearing. Consolidation procedures were carried out such that the drained rotation of principal stress angle that would precede potential undrained shear events for below-slope tailings was reasonably simulated. The results indicated the significant effects of cross-anisotropy on the undrained strength, instability stress ratio, contractive tendency and brittleness of each of the three tailings types. The magnitude of cross-anisotropy effects seen was generally consistent with previous published data on sands.

A Review of Properties, Synthesis and Applications on Lanthanum Copper Oxychalcogenides

The study of layered materials has been a significant and fascinating area due to their unique physical and chemical properties. Among various layered materials, lanthanum copper oxychalcogenides (LaCuOX (X=S, Se, Te)) have drawn a lot of attention of researchers. The study of LaCuOX was initially focused on the optoelectronic performance due to its excellent optical and electronic properties. Recently, it was found that the layered LaCuOX material also exhibits good thermoelectric properties, providing an opportunity to achieve high energy conversion efficiency through the thermoelectric effects. In this report, an overview of recent advances in LaCuOX research is provided, including crystal and electronic structure, synthetic methods, physical properties, practical applications as well as some strategies to optimize their transport properties. Theoretical and experimental results on LaCuOX crystals or thin films are both discussed in this report. Finally, the challenges and outlook for LaCuOX are evaluated based on current progress.

Functionally-oriented composite layered materials with martensitic transformations

The studies carried out show that the task of ensuring the reliability and expanding the functionality of products operating under multifactorial effects (temperature, force, deformation) can be successfully solved by functionally oriented surface composite materials with thermoelastic martensitic transformations (TMT). The authors proposed the technology of layer-by-layer synthesis of functionally-oriented composite layered materials with TMT in argon environment, implemented on patented equipment in a single technological cycle. This technology determines not only the novelty, but also the economic feasibility of technical solutions. We also suggested step-by-step methods of thermal and thermomechanical treatment of composite layered materials with TMT, which contribute to the structure stabilization while decreasing residual stress. On the basis of complex X-ray diffraction and electron microscopic studies, we determined the structural parameters of High Velocity Oxy-Fuel (HVOF) materials obtained by HVOF with subsequent thermal and thermomechanical treatment and ceramic materials ZrO2-Y2O3-CeO2-Al2O3 stabilized with Al2O3 with subsequent heat treatment. We investigated the microhardness of surface high-entropy and ceramic materials. Tests for "friction-wear" and mechanical high-cycle fatigue of steels with a composite surface laminate showed decrease in the wear rate and increase in the cyclic durability.

First-principles investigation of copper diffusion barrier performance in defective 2D layered materials

This paper investigates the diffusion barrier performance of 2D layered materials with pre-existing vacancy defects using first-principles density functional theory. Vacancy defects in 2D materials may give rise to a large amount of Cu accumulation, and consequently, the defect becomes a diffusion path for Cu. Five 2D layered structures are investigated as diffusion barriers for Cu, i.e., graphene with C vacancy, hBN with B/N vacancy, and MoS2 with Mo/2S vacancy. The calculated energy barriers using climbing image - nudged elastic band show that MoS2-V2S has the highest diffusion energy barrier among other 2D layers, followed by hBN-VN and graphene. The obtained energy barrier of Cu on defected layer is found to be proportional to the length of the diffusion path. Moreover, the diffusion of Cu through vacancy defects is found to modulate the electronic structures and magnetic properties of the 2D layer. The charge density difference shows that there exists a considerable charge transfer between Cu and barrier layer as quantified by Bader charge. Given the current need for an ultra-thin diffusion barrier layer, the obtained results contribute to the field of application of 2D materials as Cu diffusion barrier in the presence of mono-vacancy defects.

Microfluidic sensors based on two-dimensional materials for chemical and biological assessments

There has been an exponential increase in the number of studies of two-dimensional (2D) layered materials for sensing applications since the isolation of graphene in 2004. These materials serve as...

Layered macrocycles with flexibility and tunable dynamic properties for wide-range thermoresponsive color changes

Layered materials exhibit unique properties, such as intercalation and exfoliation, originating from the two-dimensional anisotropic nanostructures. A variety of inorganic and organic layered materials have been synthesized for design of...

Atomic-Scale Characterization of Structural Heterogeny in 2D TMD Layers

The heterogeneity features among 2-dimensional (2D) transition metal dichalcogenides (TMDs) layered materials endow them with distinctive properties for a vast array of novel applications. Their unique properties stem from the...

Preparation of biocompatible hydrogels reinforced by different nanosheets

Inclusion of different nanosheets derived from layered materials as a way to control the gelation of a hydrogel based on F127 tri-block copolymers functionalized with dimethacrylate (127-DMA).

NUMERICAL SIMULATION OF TRI-LAYERED MATERIALS UNDER CONTACT LOAD

Various biomedical components, such as dental crowns and hip prostheses, data processing devices, and other numerous mechanical components that transmit load through a mechanical contact, may benefit from a tri-layer design. The coating may be optimized for wear protection and corrosion prevention, whereas the intermediate layer provides increased adhesion between the outer layer and the substrate, and confines the crack propagation. The solution to the contact problem involving tri-layered materials can be pursued numerically with the finite element or the boundary element methods, but semi-analytical techniques benefitting from the efficiency of the fast Fourier transform (FFT) technique have also been successfully applied. At the heart of the FFT-assisted approach lie the frequency response functions (FRFs), which are analytical solutions for fundamental problems of elasticity such as the Boussinesq and Cerruti problems, but expressed in the frequency domain. Considering recent efforts and results in application of FFT to convolution calculations in contact problems, the displacement arising in a tri-layer configuration is computed in the frequency domain, and the contact problem is subsequently solved in the space domain using a state-of-the-art algorithm based on the conjugate gradient method. The method relies on the FRFs derived in the literature for tri-layered materials, and the efficiency and accuracy of computations in the frequency domain is assured by using the Discrete Convolution Fast Fourier Technique (DCFFT) with influence coefficients derived from the FRFs. The computer program reproduces well-known results for bi-layered materials. Numerical simulations are performed for various configurations in which the elastic properties of the layers, as well as the frictional coefficient, are varied. By using the newly advanced simulation technique, design recommendations may be advanced for the optimal configuration of tri-layered materials under contact load.