Zhongxu Lian

Fabrication and applications of two- and three-dimensional curved surfaces with robust underwater superoleophobic properties

In this work, a method for the fabrication of two- and three-dimensional curved surfaces with robust underwater superoleophobicity is reported for the first time on light alloys (including 5083 Al and TC4 Ti alloys) through the high speed wire electrical discharge machining (HS-WEDM). The surface morphology and compositions were characterized by scanning electron microscope and energy-dispersive X-ray spectrometer. The results showed that rough structures and a layer of oxidization were created on the light alloys by HS-WEDM cutting. The two- and three-dimensional structured curved surfaces after an ethanol immersion exhibited the extreme underwater superoleophobic property with the high oil contact angle and low oil sliding angle. More importantly, the underwater superoleophobic surfaces with the three-dimensional curved features could have many new applications. In order to use the potential functions, the durability of the fabricated samples was tested and the results showed that the samples still exhibited the underwater superoleophobic property after the underwater storage and physical mechanism tests. Additionally, this method is versatile, simple, environment-friendly, and cost-effective.

Nanosecond Laser-Induced Underwater Superoleophobic and Underoil Superhydrophobic Mesh for Oil/Water Separation

Materials with special wettability have drawn considerable attention especially in the practical application for the separation and recovery of the oily wastewater, whereas there still remain challenges of the high-cost materials, significant time, and complicated production equipment. Here, a simple method to fabricate the underwater superoleophobic and underoil superhydrophobic brass mesh via the nanosecond laser ablation is reported for the first time, which provided the micro-/nanoscale hierarchical structures. This mesh is superhydrophilic and superoleophilic in air but superoleophobic under water and superhydrophobic under oil. On the basis of the special wettability of the as-fabricated mesh, we demonstrate a proof of the light or heavy oil/water separation, and the excellent separation efficiencies (>96%) and the superior water/oil breakthrough pressure coupled with the high water/oil flux are achieved. Moreover, the nanosecond laser technique is simple and economical, and it is advisable for the large-area and mass fabrication of the underwater superoleophobic and underoil superhydrophobic mesh in the large-scale oil/water separation.

Research on Homogenization and Surface Integrity of Ti-6Al-4V Alloy by Longitudinal-Torsional Coupled Ultrasonic Vibration Ball-End Milling

This paper aims to study the surface homogenization and integrity of Ti-6Al4V alloy by longitudinal-torsional coupled ultrasonic vibration assisted ball-end milling. A method of continuous processing between the flat surface and freeform surface connection is proposed by using ultrasonic vibration assisted ball-end precision milling, during this process, it is not necessary to exchange the cutting tool. The way has been explored for changing the homogenization of surface on Ti-6Al-4V by ultrasonic vibration-assisted milling (UVAM). Cutting experiments employing three parameters, cutting speed, feed rate and depth of cut and two types of machining forms using ballend milling with UVAM and conventional milling (CM) respectively. The high frequency cutting force, finished surface roughness, topography and residual stresses on the surface and tool wear have been measured by advanced instruments. Particularly, adopting the high frequency cutting force measurement system, it is concluded cutting force in ball-end milling decreased significantly using UVAM as against CM. Moreover, the surface roughness by UVAM with ball-end milling is much better than the CM at a high cutting speed. However, an opposite trend is observed at a low cutting speed. Especially, there is a steep decrease from Ra 0.828 μm average value at 4000 rpm to Ra 0.129 μm average value at 5000 rpm. At the same time, the homogenization of surface roughness and residual stresses decrease significantly in UVAM as compared to which in CM when taking the transversal-longitudinal ratio into consideration. Cutting experiments and measuring results are demonstrated the validity and feasibility of UVAM with ball-end milling, and this method enjoys significant advantages compared to CM process.

Anisotropic hydrophobic surface fabricated by microstructuring of aluminum alloy using high speed micro-milling

This paper put the microstructures of rice leaf surface as bionic object, grating micro-arrays were processed on 7075 aluminum alloy surface by high speed micro-milling machining (HSMM). The micromorphologies and hydrophobic properties of specimen surfaces were studied adopting scanning electron microscopy and contact angle (CA) goniometer, and analyzing its hydrophobic mechanism. Results show that hydrophobic surfaces is successfully fabricated only by building grating micro-array structures on aluminum alloy surface using HSMM without modifying any chemical substances, the contact angle on aluminum alloy surface increased maximally to 152. 83° from 63.27° before processing. Furthermore, the contact angle on specimen surfaces appear anisotropic wettability, which the contact angle difference of two direction is about 40°~60°. In addition, the hydrophobicity and super-hydrophobicity on aluminum alloy surface is a coupling function result by both submillimetre regular grating arrays and many irregular nanoscale pits and projections distributing on submillimetre grooves surface.

HS-WEDM machining of superamphiphobic al surfaces and effect of the droplet size on wettability

In this study, superamphiphobic (SAP) aluminum (Al) alloy 5083 surfaces were produced with water/oil high contact angle (CA) greater than 150° and low sliding angle (SA). A simple and environmentally friendly technology of the high speed wire electrical discharge machining (HS-WEDM) was used to introduce submillimeter-, micro- and nano-scale structures, respectively, which resulted in a hierarchical morphology. Surface energy was reduced by coating with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) on the structured surfaces. The CAs approaching 154.80° for water, 154.55° for glycerol, and 153.92° for ethylene glycol were obtained after building hierarchical structures by HS-WEDM. The fundamental wettability models were used to explain the experimental results. The effect of the droplet size on the wettability of surfaces was also investigated. In addition, the SAP property of the Al surfaces is still exhibited after the stability, immersion, finger pressure and ultrasonic cleaning tests. SAP Al surfaces could see many wide potential applications including self-cleaning, anti-corrosion, anti-fouling, anti-icing and oil transportation.

Cicada wing with adhesive superhydrophobicity and their biomimetic fabrication

Cicada is hymenoptera insect. It is found that cicada wing exhibit super-hydrophobicity and a high adhesive force with water, which is different from lotus leaf. The water contact angle (WCA) on cicada wing is 145.81±4.83°. The water droplet does not slide on the cicada wing surface when the surface is tilted at 90°. Observed from the SEM data, the cicada wing surface is covered by the columnar structure in regularly rule. To copy the wettability of cicada wing surfaces, we report a new approach for fabricating a super-hydrophobic surface on copper substrate using reciprocating type high speed wire cut electrical discharge machining (HS-WEDM). The resultant samples were characterized by scanning electron microscopy (SEM) and contact angle measuring instrument, It was found that water contact angle of the resulting surface was increased from 82.11° to 152.91±4.02°, realizing the transition from the hydrophilic to super-hydrophobic. When the sample is tilted at 90°, the water droplet does not roll off from the surface or even upside down, indicating the resulting surface has a high adhesive force to water. The resulting surface were covered with composite structures composed of micro-scale diamond cylinder structure and concave and protuberance, and nano-scale granular structure, which was the reason of super-hydrophobicity and high adhesive force of copper surface. Moreover, new copper oxide generated in the process of HS-WEDM is another reason of copper surface.