Preparation of pH-responsive reversible wettable surfaces and application for oil-water separation.

With the continuous development of society, the discharge of oily wastewater in daily life and industry has gradually increased, causing considerable damage to the environment, and how to effectively treat oily wastewater is an urgent problem. In this paper, a simple method is proposed to prepare superhydrophobic stainless steel mesh with pH response. The relationship between the ratio of mixed thiols and the surface wettability was explored, as well as the morphology, chemical composition, and pH-responsive mechanism of the stainless steel mesh surface were analyzed, and the separation efficiency, recycling ability, and backwashing ability of the mesh were explored by oil-water separation experiments. It was found that when the molar fraction of 11-mercaptoundecanoic acid and 1-decanethiol in the mixed mercaptan was 2:3, the water contact angle of the surface at this point was 156.5 ± 1°, with pH response characteristics and good oil-water separation efficiency, backwashing and recycling capabilities.

Study on the Microstructure and Properties of Welded Joints of Laser Shock Peening on HC420LA Low-Alloy High-Tensile Steel.

Laser shock peening is a promising surface strengthening technology that can effectively improve the mechanical properties of materials. This paper is based on the laser shock peening process for HC420LA low-alloy high-strength steel weldments. Contrast analysis of the evolution of the microstructure, residual stress distribution and mechanical properties of the welded joints before and after the laser shock peening on each region is carried out; a combination of tensile fracture and impact toughness fracture morphology analyses of laser shock peening on the welded joint strength and toughness regulation mechanism are also completed. The results show that the laser shock peening can refine the microstructure of the welded joint effectively, the microhardness of all areas of the joint increases and the weld residual tensile stresses are transformed into beneficial residual compressive stresses, affecting a layer depth of 600 µm. In addition, the strength and impact toughness of welded joints of HC420LA low-alloy high-strength steel are improved.

Effect of Laser Quenching-Shock Peening Strengthening on the Microstructure and Mechanical Properties of Cr12MoV Steel.

The automobile covering parts mold is a key piece of equipment in the automobile industry, and its drawbead is the core element that affects the life of the mold and the quality of the parts made. Due to the complex structure of the mold cavity for covering parts, there exist differences between material flow characteristics, load conditions, stress strain, failure forms and so on in the surface of different parts of its drawbead and the different directions of the same part of the drawbead, thus putting forward new requirements for material strengthening. For the differentiated lose efficacy forms of the dangerous end faces of the tension bars, this study carried out research into the effect of laser quenching-shock peening strengthening (LQ-LSP) on the organization, plastic deformation resistance and wear resistance of Cr12MoV steel. It was shown that the microhardness (722.30 HV) and residual stress (-383.84 MPa) of the specimens were further enhanced after laser quenching-shock peening composite strengthening. The residual austenite content of the specimen was reduced to 0.8%, and the eutectic carbide distribution morphology was improved. After three rounds of laser composite peening, the specimens had the smallest displacement of the nanoindentation load-depth curve, which exhibited the greatest nanohardness (20.0 Pa) and modulus of elasticity (565.25 Pa), while reducing the coefficient of friction (0.61) and surface roughness (0.152 Ra). The smooth and flat surface of the specimen with shallow and narrow plow grooves improved the resistance of Cr12MoV steel to plastic deformation and wear.

Influence of reaction parameters on the fate of nitrogen during the supercritical water gasification of dewatered sewage sludge.

This study investigated the effects of different parameters on the fate of nitrogen (N) in products after supercritical water gasification (SCWG) of dewatered sewage sludge (DSS). N distribution and morphology were most affected by temperature, followed by reaction time and heating rate, while reaction pressure had little effect on them. In terms of specific performance, higher temperature, longer reaction time, and slower heating rate were beneficial to the increase of NH4+-N content in the liquid phase. Compared with raw sludge, after SCWG, the solid phase contained more inorganic-N and less protein-N, a certain proportion of quaternary-N and nitrile-N. The proportion of N-containing compounds in the biocrude phase was between 0.26%-20.34%, suggesting the importance of more research on N in the biocrude phase. The recovery rate of N in all samples was between 64.34%-93.82%. The major proportion of N (42.27%-60.91%) was transformed into the liquid phase, while the remaining entered the solid phase (10.54%-21.45%) and the biocrude phase (6.18%-15.78%). These findings are helpful to better understand the principle of N distribution in products of DSS after SCWG and provide some new ideas for reducing N-containing by-product formation in the future.

Anisotropic Enhancement of Second-Harmonic Generation in Monolayer and Bilayer MoS2 by Integrating with TiO2 Nanowires.

The ability to design and enhance the nonlinear optical responses in two-dimensional (2D) transition-metal dichalcogenides (TMDCs) is both of fundamental interest and highly desirable for developing TMDC-based nonlinear optical applications, such as nonlinear convertors and optical modulators. Here, we report for the first time a strong anisotropic enhancement of optical second-harmonic generation (SHG) in monolayer molybdenum disulfide (MoS2) by integrating with one-dimensional (1D) titanium dioxide nanowires (NWs). The SHG signal from the MoS2/NW hybrid structures is over 2 orders of magnitude stronger than that in the bare monolayer MoS2. Polarized SHG measurements revealed a giant anisotropy in SHG response of the MoS2/NW hybrid. The pattern of the anisotropic SHG depends highly on the stacking angle between the nanowire direction and the MoS2 crystal orientation, which is attributed to the 1D NW-induced directional strain fields in the layered MoS2. A similar effect has also been observed in bilayer MoS2/NW hybrid structure, further proving the proposed scenario. This work provides an effective approach to selectively and directionally designing the nonlinear optical response of layered TMDCs, paving the way for developing high-performance, anisotropic nonlinear photonic nanodevices.