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Extreme wettability materials, which can enable high-efficiency oil/water separation, has become a widely discussed topic due to increasingly severe oil pollutions including frequent offshore oil-spills accidents and industrial oily wastewater emission. However, most of existing methods to prepare these materials involved complicated machining processes or dangerous operations, especially the use of corrosive or toxic chemicals. Herein, a novel and environment friendly method including mark electrochemical machining (MECM) and subsequent chemical immersion, was proposed to acquire micropore arrays on Al foil for efficient oil collection from oil/water mixtures. Micro-dimple arrays were generally fabricated by MECM process followed by CuCl2 immersion to make it through. Both simulation and experimental verification were conducted to elucidate how dimple structures varied with machining parameters. The micro-scale rectangular-shaped step-like structures on micropore arrays endowed as-prepared samples with excellent superhydrophibic and underwater superoleophobic properties. Moreover, oils with kinematic viscosities ranging from 0.41 to 74.4 cSt could be separated from water with separation efficiencies above 95%. The superhydrophilic Al foil still showed good durability through repeated oil/water separation tests, and retained its superhydrophilicity even after the storage in water for 120 hours. Therefore, this novel and green method gives researchers new insights into functional materials preparation for practical oil/water separation. [ABSTRACT FROM AUTHOR]

The unique microstructures of bulk metallic glasses (BMGs) provide them with excellent mechanical, physical, and chemical properties, having important applications in the fields of medical devices, military equipment, aerospace, etc. However, the superb mechanical properties also contribute to poor machinability of the BMGs. Currently, researchers have proposed to improve the machinability by single-point diamond turning, laser-assisted machining and ultrasonic vibration-assisted machining, but their plasticity and viscous flow remain unchanged, thus restraining further enhancement of surface quality. Atmospheric pressure cold plasma jet (APCPJ), which is rich in active particles, can effectively ameliorate material machinability by modulating material properties. In this paper, we propose to use the APCPJ to regulate the properties of BMGs, and carry out nanoindentation, nanoscratching, and micro-milling experiments to investigate the influence mechanisms of APCPJ on the material properties and cutting process. The results demonstrate that after modified by APCPJ, plastic deformability of the BMGs is improved due to the increase of free volume content; meanwhile, the viscous flow is inhibited. The micro-milling experiments indicate that under the conditions of feed rate V f = 500 μm/s, spindle speed n = 30,000 rpm, and cutting depth a p = 5 μm, the improvement effect of APCPJ on the cutting process is relatively optimum. The surface roughness Ra of the Zr-based BMG and Ti-based BMG obtained by APCPJ are respectively 0.076 μm and 0.081 μm, which can be reduced by 37.7 % and 38.2 % compared with dry micro-milling. The cutting forces F z in the direction of cutting depth are also reduced by 30.9 % and 23.3 %, respectively. The APCPJ-assisted micro-milling method proposed in this work may ameliorate the machining quality of BMGs and promote the application of BMGs and APCPJ-assisted machining technology in aerospace and precision machining. [ABSTRACT FROM AUTHOR]

Superhydrophobic surfaces on mold steel substrates were fabricated via simple and environment-friendly electrochemical technology followed by fluoroalkylsilane (FAS) modification. The microstructure, crystal structure, chemical composition, and wettability of the sample surfaces were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and optical contact angle measuring instrument. The influences of current density and electrochemical machining time on wettability were also studied. The results show that, after the electrochemical processing, the mold steel substrates were covered with a layer of passive films, which have micro/nano binary rough structures composed of rugged plateau structures and rupture-like shapes. Before fluorination, the obtained sample surfaces showed superhydrophilicity (the water contact angles were almost 0°), while the sample surfaces became superhydrophobic (the water contact angles were 167.2° and the water rolling angles were 4.3°) after fluorination. The proposed method is simple, economical and environmental-friendly, and has great potential for large-scale industrial applications. [ABSTRACT FROM AUTHOR]

Surface textures, such as micro pillar arrays, greatly promote the developments of many advanced fields. As many methods have been applied to fabricate the micro pillar arrays on silicon and polymer substrates, it is a still challenge to fabricate micro pillar arrays on metals. In this paper, through-mask electrochemical micromachining (TMEMM) was employed to fabricate micro pillar arrays on aluminum (Al) substrate. The effects of the direct and pulsed currents on surface morphology of the micro pillar arrays were investigated, and the ordered micro pillar arrays with different top diameters were obtained at the pulsed currents. Then, the influences of the current densities on the morphology of the micro pillar arrays were studied, and the largest etching anisotropy factor (EF) was obtained at a current density of 1 A/cm2. Finally, the wettability of the as-prepared micro pillar arrays with low surface energy modification was investigated. When the top diameters were 50– 90 μm and the heights were larger than 35 μm, all the micro pillar arrays obtained at different current densities showed superhydrophobicity with water contact angle larger than 150°. Unlabelled Image • Micro pillar arrays were fabricated by through-mask electrochemical micromachining. • Duty cycles and frequencies of etching currents affect pillar morphology seriously. • The larger etching anisotropy factor is obtained at low current densities. • Superhydrophobicity is obtained with suitable parameters. [ABSTRACT FROM AUTHOR]