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Cr(VI) in wastewater poses a serious threat to human health, so there is an urgent need to remove it using a cost-effective way. Herein, we report a composite electrode material of homemade paulownia biochar and MoS2 (PBC@MoS2) for the efficient and selective removal of Cr(VI) from wastewater. PBC@MoS2 has an excellent ability to selectively remove Cr(VI) by electrosorption under the coexistence of different anions and cations (385.74 mg g−1 at voltage = 1.2 V, spacing = 1 mm, and initial concentration = 60 mg L−1). It can achieve 98.75% desorption and regeneration of the electrode within 1 h, and after 5 cycles of adsorption/desorption, it still maintains 97.02% of the original adsorption capacity. The characterization analysis shows that the removal process of Cr(VI) has both electrosorption and reduction effects, which can reduce 85.4% of the highly toxic Cr(VI) to the less toxic Cr(III). This is facilitated by the large specific surface area and special two-dimensional sheet structure of PBC@MoS2 composites. The results of this work can provide data support for the design of high-performance CDI systems for the removal of Cr(VI) from wastewater. [ABSTRACT FROM AUTHOR]

Abstract The process of nanocontact including indentation and retraction between a large Ni tip and a Cu substrate is investigated using quasicontinuum (QC) method. The multiscale model reveals that significant plastic deformation occurs during the process of nanocontact between Ni tip and Cu substrate. Plastic deformation is observed in an area as large as 20 nm wide and 10 nm thick beneath Ni tip during the indentation and retraction. Also, plastic deformation at a deep position in the Cu substrate does not disappear after the neck failure. The analysis of generalized planar fault energy curve shows that there is a strong tendency for deformation twinning in Cu substrate. However, deformation twinning will be retarded during indentation due to the high stress intensity caused by stepped surface of Ni tip. The abrupt drop of load curve during tip retraction is attributed to the two different fracture mechanisms. One is atomic rearrangement near the interface of Ni tip and Cu substrate at the initial stage of neck fracture, the other is shear behavior of adjacent {111} planes at the necking point. A comparison of the critical load and critical contact radius for neck fracture is also made between theoretical values and our numerical results.

Abstract Nanoindentation processes in single crystal Ag thin film under different crystallographic orientations and various indenter widths are simulated by the quasicontinuum method. The nanoindentation deformation processes under influences of crystalline anisotropy and indenter size are investigated about hardness, load distribution, critical load for first dislocation emission and strain energy under the indenter. The simulation results are compared with previous experimental results and Rice-Thomson (R-T) dislocation model solution. It is shown that entirely different dislocation activities are presented under the effect of crystalline anisotropy during nanoindentation. The sharp load drops in the load–displacement curves are caused by the different dislocation activities. Both crystalline anisotropy and indenter size are found to have distinct effect on hardness, contact stress distribution, critical load for first dislocation emission and strain energy under the indenter. The above quantities are decreased at the indenter into Ag thin film along the crystal orientation with more favorable slip directions that easy trigger slip systems; whereas those will increase at the indenter into Ag thin film along the crystal orientation with less or without favorable slip directions that hard trigger slip systems. The results are shown to be in good agreement with experimental results and R-T dislocation model solution.