High-efficiency 2D nanosheet exfoliation by a solid suspension-improving method

Two-dimensional (2D) materials with mono or few layers have wide application prospects, including electronic, optoelectronic, and interface functional coatings in addition to energy conversion and storage applications. However, the exfoliation of such materials is still challenging due to their low yield, high cost, and poor ecological safety in preparation. Herein, a safe and efficient solid suspension-improving method was proposed to exfoliate hexagonal boron nitride nanosheets (hBNNSs) in a large yield. The method entails adding a permeation barrier layer in the solvothermal kettle, thus prolonging the contact time between the solvent and hexagonal boron nitride (hBN) nanosheetand improving the stripping efficiency without the need for mechanical agitation. In addition, the proposed method selectively utilizes a matching solvent that can reduce the stripping energy of the material and employs a high-temperature steam shearing process. Compared with other methods, the exfoliating yield of hBNNSs is up to 42.3% at 150°C for 12 h, and the strategy is applicable to other 2D materials. In application, the ionic conductivity of a PEO/hBNNSs composite electrolytes reached 2.18×10−4 S cm−1 at 60°C. Overall, a versatile and effective method for stripping 2D materials in addition to a new safe energy management strategy were provided.

Simulation of flow field characteristics in scheelite leaching tank with H2SO4–H3PO4

Digesting scheelite by using H2SO4–H3PO4 is an environment-friendly and low-cost technology. The key approach to achieving efficient scheelite decomposition involves providing a good environment with uniform material composition for the growth of calcium sulfate. Therefore, numerical simulation of gypsum particle suspensions in a square stirred tank with a frame-type agitator for leaching scheelite was investigated. Simulated optimized results showed that the homogeneity of a multiphase flow system increased with the speed of the agitator. Reducing off-bottom clearance eased the dispersion of gypsum into the liquid. Adding baffles increased turbulence intensity and axial velocity in the tank, which eased solid suspension. The suspension improved, together with increases in the torque and power requirements of the agitator when the speed changed and baffled were added. However, when the solid suspension improved, the stirring torque and power slightly decreased, under a different off-bottom clearance of the agitator. Meanwhile, with residence time distribution as an evaluation criterion, the experimental results verified that the flow characteristics of the solid particles improved after optimization. This study can provide a theoretical basis and guidance for the optimization of the design and enlargement test of the stirred tank for leaching scheelite with sulfuric–phosphorous mixed acid.

Scaling seismic fault thickness from the laboratory to the field

<p>Pseudotachylytes originate from the solidification of frictional melt, which transiently forms and lubricates the fault plane during an earthquake. Here we observe how the pseudotachylyte thickness <em>a</em> scales with the relative displacement <em>D</em> both at the laboratory and field scales, for measured slip varying from microns to meters, over six orders of magnitude. Considering all the data jointly, a bend appears in the scaling relationship when slip and thickness reach ∼1 mm and 100 µm, respectively, i.e. <em>M</em><sub>W</sub> > 1. This bend can be attributed to the melt thickness reaching a steady‐state value due to melting dynamics under shear heating, as is suggested by the solution of a Stefan problem with a migrating boundary. Each increment of fault is heating up due to fast shearing near the rupture tip and starting cooling by thermal diffusion upon rupture. The building and sustainability of a connected melt layer depends on this energy balance. For plurimillimetric thicknesses (<em>a</em> > 1 mm), melt thickness growth reflects in first approximation the rate of shear heating which appears to decay in <em>D</em><sup>−1/2</sup> to <em>D</em><sup>−1</sup>, likely due to melt lubrication controlled by melt + solid suspension viscosity and mobility. The pseudotachylyte thickness scales with moment <em>M</em><sub>0</sub> and magnitude <em>M</em><sub>W</sub>; therefore, thickness alone may be used to estimate magnitude on fossil faults in the field in the absence of displacement markers within a reasonable error margin.</p>

Nonwoven Bio-Based Membranes for Removal of Micropollutants from Aqueous Water

The aim of this paper is to obtain two types of bio-based membranes by electrospinning process: one based on polylactic acid (PLA), and PLA/polyhydroxybutyrate (PHB), and the second by coating the PLA/PHB membrane with chitosan (CS) and CS/activated coal (AC), respectively for removal of micropollutants from aqueous water. The designed bio-based electrospun membranes were analyzed through scanning electron microscopy (SEM), attenuated total reflectance (ATR) - Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), the removal of solid suspension and Pb (II) from aqueous water. The quality of filtrates was evaluated by physical-chemical methods, while the retaining of Pb (II) from wastewaters was reported.

A virtual test bench for determining the loads in the air suspension of the rear trolley of a truck at the early stages of design

To determine the maximum loads acting in the rear air suspension of a truck at the early stages of design there was used computer modeling based on solving equations of dynamics of solids and implemented in the Recurdyn software. The components of the developed virtual test bench, includ-ing hinges, power connections, drive axles, a wheel-hub assembly with a wheel and a support plat-form, are considered in detail. The test bench is controlled using a mathematical model created in the environment for calculating the dynamics of rigid bodies and associated with a solid suspension model by standard software tools of the application. The test bench is controlled using a mathemati-cal model created in the environment for calculating the dynamics of rigid bodies and associated with a solid suspension model by standard software tools of the application. The use of such a test bench makes it possible to determine the loads in the hinges and power connections of the suspen-sion, to determine the mutual positions of the links for each load mode, to increase the accuracy of the calculation of loads in comparison with the flat kinematic and force calculation. The mathemati-cal model of the virtual test bench allows to carry out numerous parametric studies of the suspension without the involvement of expensive full-scale prototypes. This makes it possible at the early stages of design to determine all hazardous modes, select rational parameters of the elements, and reduce design costs. The paper shows the results of modeling the operation of a virtual test bench with an air suspen-sion in the most typical loading modes, identifying the most dangerous modes. The efficiency and adequacy of the mathematical model of the suspension was proved. Examples of determining the force in all the joints of the structure, the choice of maximum loads for design calculations when designing the air suspension of vehicle were shown.