Jinkai Xu

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.

Superhydrophobic surface prepared by micromilling and grinding on aluminium alloy

An efficient method for processing superhydrophobic surface is presented in this paper, which can realise the microstructure machining on a large area. First, the microgroove arrays were processed by high speed precision micromilling machine on the surface of the aluminium alloy. Then, the surface of the microgroove was ground by 1000 # electrostatic sand alumina water resistant abrasive belt. The machined surface topography was observed by SEM, which showed that the microgroove arrays were uniform. The contact angles of the water on the microgroove arrays were measured in different directions. In the parallel direction, the contact angle of microgroove arrays is 142±0·5°, whereas in the vertical direction, it arrives 160±0·6°. The above values of contact angle mean that a stable superhydrophobic metallic surface was prepared by the micromilling and grinding.

Experimental study of surface roughness effects on wettability

In this paper, we present a method to fabricate aluminum alloy 5083 surfaces with different surface roughness using reciprocating type high speed wire cut electrical discharge machining (HS-WEDM). Observe the processed surface by ultra-depth three-dimensional scanning system, obviously notice that craters and bumps were uniformly distributed in the surface which is machined by HS-WEDM. And the size of craters and bumps are relevant to the parameters of the pulse power supply. Then we obtain a surface with static contact angle of 136° and draw a changing trends curve of the static contact angle along with surface roughness by measuring the surface roughness and static contact angle respectively. It has provided experimental basis and theoretical foundation for fabricating aluminum alloy super-hydrophobic surface by HS-WEDM.

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.

An investigation on drilling micro holes in different processes using micro-EDM

Microparts are widely used for aerospace, medical and other special industries. Due to the limitation of cutting tools and processing technology, and cost a lot, it is difficult to machining for conventional mechanical process especially for the micro holes in the materials with high strength and hardness. Yet it is a highly efficient machining process using micro-EDM, because of its non-contact mode. SUS 304 possess excellence corrosion resistance and heat resistance while it is hard to machine, this paper will do a series of research on the SUS 304 material about drilling micro holes using micro-EDM. From the comparative analysis of three different processes about drilling holes, it shows that using cutting edge electrode and layered milling processes effectively decrease the taper angle under keeping the precision of holes, the cutting edge electrode produces better material removal rate(MRR), and layered milling with different layered numbers have different influence on the machining performance.

A comparative investigation of drilling and milling micro holes using micro-EDM

Micro Electrical Discharge Machining (micro-EDM), is one of the most important technologies for the machining of difficult-to-cut materials, and it can be considered as one of the most promising manufacturing process for fabricating micro holes. Micro-EDM is suitable for machining micro holes, while it is still hard to machining holes with high depth. The study will make a research on drilling and milling holes using micro-EDM, the milling process shows better performance especially for the holes with high depth to diameter ratio; while drilling process could gain higher processing speed and better geometrical properties of the micro-holes.

Model of micro-cutting and analysis of micro cutting force

The forces acting on the rake and flank face are analyzed in details, through investigating the mechanism of the cutting surface formation according to the characteristics of micro-cutting. The relationship of rounded edge radius and cutting force is presented. The model of micro-cutting is established and the relationship between the cutting forces and the main parameters are obtained. The mechanism of micro-cutting is exploded theoretically, which is significant in cutting tools material choosing and cutting tools edge improving.

Study on Fault-tolerant Filter Algorithm for Integrated Navigation System

The fault-tolerance of multi-sensor system is analyzed in this paper. Based on studying the existing methods, the information sharing coefficient method based on the expert system is proposed. The theoretical analysis and simulation show that this method can effectively improve the fault-tolerant performance of the fault-free subsystem and reduce the computation load of the whole system.

Study on mild and severe wear of 7075 aluminum alloys by high-speed wire electrical discharge machining

The recast and the carbon layers were fabricated on 7075Al alloys surface by the high-speed wire electrical discharge machining (HS-WEDM) technologyunder various working parameters. The mechanical properties and friction behaviors of the layers were investigated by UMT. 7075 Al alloys were used to do dry sliding wear tests on a pin-ondisk wear tester at room temperature under various contact pressures. 7075 Al alloys had almost the same wear regularity as a function of sliding velocity and rated frequency. The hardness of recast layer was improved. And this method can enhance durability of 7075 Al alloy effectively.The transition to severe wear occurred at a higher load (12N) for asmachined samples, compared with 7075 matrix (9N), the as-machined samples exhibited lower wear rates within the tested loading range.

Micro hardness analysis of colorful oxide film formation on titanium by using WEDM-HS process

This paper introduces the machining method and machining principle for the coloring technology of titanium alloy surface by WEDM-HS (High-speed Wire Electrical Discharge Machining), we can get the relationship between the pulse voltage and film thickness through the experiment, the different thickness of the film will generate different color on titanium alloy surface, moreover, the thickness and the color on titanium alloy surface can be changed by adjusting the processing parameters. This paper analyzed the micro hardness of titanium alloy surface before and after processing, the experimental results show that the micro hardness of titanium alloy after processing were higher than the matrix, and with the increase of coloring film thickness, the micro hardness will increase.