Search

Micro-milling is a low-cost, efficient, and high-precision machining method for manufacturing tiny parts, and has significant application value in various fields. In order to meet the high-accuracy requirements, several composite micro-milling methods have been proposed. However, these methods cannot change surface characteristics of materials, and poor permeability of cooling medium on the tool-workpiece interface remains unsolved. Atmospheric pressure plasma jet can efficiently improve surface wettability without obviously changing surface microstructures and may have promising application potential in machining of difficult-to-cut materials. Here, we propose to induce atmospheric pressure plasma jet to the micro-milling area to improve machinability and surface quality of TC4 titanium alloy. The influences of plasma jet on material wettability and mechanical property are firstly investigated by conducting plasma modification and tensile experiments. Then, micro-milling experiments of TC4 titanium alloy are performed under different atmospheres (dry, nitrogen jet, plasma jet, minimum quantity lubrication, and plasma jet + minimum quantity lubrication). The experimental results indicate that plasma jet can promote material fracture of TC4 titanium alloy, as well as reduce cutting force and cutting temperature, thereby obtaining better surface quality. [ABSTRACT FROM AUTHOR]

High-strength alloys have significant application values in aerospace industry due to their excellent mechanical properties. However, grinding of these alloys, which is generally used for precision machining, suffers from problems like high grinding temperature and poor surface quality. Having relatively lower grinding temperature and smaller grinding force, micro-grinding is a high-efficient manufacturing method for precision machining of difficult-to-cut materials. Nevertheless, the side effects induced by current composite grinding methods, such as temperature gradient and chatter marks, tend to be more obvious in the micro-machining process. Atmospheric pressure plasma jet (APPJ) can effectively improve metal surface wettability without changing surface structures. On the other hand, minimum quantity lubrication (MQL) can more efficiently cool and lubricate the grinding area. Here, we propose to induce APPJ and MQL cooling media into the micro-grinding area, and adjust the cooling and lubricating characteristics. Quenched GCr15 workpieces are machined under five different conditions (dry micro-grinding, nitrogen jet assisted micro-grinding, APPJ assisted micro-grinding, MQL assisted micro-grinding, and APPJ+MQL assisted micro-grinding), and grinding temperature, grinding force, surface roughness, and surface morphology of workpieces in each group are investigated and analyzed. The results indicate that APPJ can reduce grinding force and that APPJ+MQL micro-grinding can obtain surfaces with much better surface quality. Tensile experiments demonstrate that APPJ can reduce material elongation rate and promote material fracture, which contributes to its positive effect on the micro-grinding process. The environmentally-friendly method is expected to have promising application potentials in machining of difficult-to-cut materials. [ABSTRACT FROM AUTHOR]

Oil/water separation has attracted more attention with the dramatic increasing of oil spill accidents and arbitrarily discharged oily industrial water. However, many reported materials with controllable wettability for on-demand oil/water separation of both heavy and light oil/water mixtures involve complicated devices and dangerous fabrication processes. Herein, we propose a simple, environmentally friendly and high-efficient method to fabricate Al mesh with controllable wettability. Heavy oil can be separated with a high efficiency of 99% in oil-removing mode. For light oil, the separation efficiency can also reach up to 99% in water-removing mode. Additionally, surface wettability of the mesh can be conversed from superhydrophobicity to superhydrophilicity by atmospheric pressure plasma jet (APPJ) and heating, thereby realizing continuous bidirectional separation. Therefore, this work provides a facile, green, and efficient way for on-demand oil/water separation and finds a promising solution for oil pollution problems. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy Inconel 718 is one of the hardest materials owing to its high hardness and additional physical properties. It is the most commonly used superalloy in gas turbine, aerospace, and automobile sectors. Micro-milling is generally employed for precision manufacturing of tiny structures, but it is difficult to obtain good surface quality with micro-milling Inconel 718 because of its excellent mechanical properties like high strength and hardness. Atmospheric pressure cold plasma jet can effectively improve surface wettability without changing surface micromorphology, which is expected to have positive lubricating effects in micro-machining of difficult-to-cut materials. In addition, minimum quantity lubrication can induce coolants into the machining area more efficiently, and is especially appropriate for micro-machining. In this paper, we propose a composite micro-milling method combining plasma jet and minimum quantity lubrication to machine Inconel 718. The effect of plasma jet on machinability is investigated by performing micro-milling experiments under different atmospheres (dry, nitrogen jet, plasma jet, minimum quantity lubrication, and plasma + minimum quantity lubrication). Surface roughness, cutting forces, and residual stress are the measures using corresponding techniques. The results indicate that the atmospheric pressure cold plasma jet can efficiently improve surface quality and reduce cutting forces of Inconel 718. [ABSTRACT FROM AUTHOR]

Severe plastic deformation and lateral flow during machining of pure iron surface resulted in relatively serious tool wear and poor surface quality. Although several methods proposed could improve machinability of pure iron to some extent, poor wettability and high plasticity of pure iron cannot be changed, and further improvement of surface quality may be therefore restrained. In this paper, we propose a new machining method using atmospheric pressure plasma jet to adjust material properties of pure iron during precision turning process. The influence mechanism of plasma jet on surface wettability of pure iron is investigated by plasma modification experiment, scanning electron microscope, and X-ray photoelectron spectroscopy. On the basis of the influence mechanism, precision turning experiments are performed under different lubricating conditions. The experimental results indicate that plasma jet can effectively improve pure iron surface wettability by changing surface composition while not influencing surface microstructures. Under plasma atmosphere, surface roughness and cutting force are obviously reduced, and tool wear is effectively alleviated. [ABSTRACT FROM AUTHOR]

Tubes are indispensable in our daily life, mechanical engineering and biomedical fields. However, the practical applications of tubes are sometimes limited by their poor wettability. Reported herein is hydrophilization of the tube inner wall by transferred atmospheric pressure plasma (TAPP). An Ar atmospheric pressure plasma jet (APPJ) is used to induce He TAPP inside polytetrafluoroethylene (PTFE) tube to perform inner wall surface modification. Optical emission spectrum (OES) is used to investigate the distribution of active species, which are known as enablers for surface modification, along the TAPP. Tubes’ surface properties demonstrate that after TAPP treatment, the wettability of the tube inner wall is well improved due to the decrease of surface roughness, the removal of surface fluorine and introduction of oxygen. Notably, a deep surface modification can significantly retard the aging of the obtained hydrophilicity. The results presented here clearly demonstrate the great potential of TAPP for surface modification of the inner wall of tube or other hollow bodies, and thus a uniform, effective and long-lasting surface modification of tube with any length can be easily realized by moving the tube along its axis. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE) has excellent properties and has been widely used in various fields. However, the PTFE surfaces have relatively poor wettability and adhesive property, which restrains their widespread applications. Although atmospheric-pressure plasma jets have been employed to treat the PTFE surfaces, hydrophilization effect and processing efficiency still need to be further improved. In this paper, we propose to add ammonia water into the working gas of the atmospheric-pressure plasma jets to better modify the PTFE surfaces. The influences of ammonia water contents on surface wettability and adhesive property of the PTFE surfaces were investigated by water contact angle (WCA) measurement and peel strength experiments, respectively. When the ammonia water-mixed ratio was 1%, a WCA of ∼19° was obtained after 120 s plasma treatment, which was much lower than that treated by pure helium plasma jet (∼29°) and untreated surface (∼101°). In addition, the adhesive property was also well improved by the ammonia water-mixed plasma jets: peel strength of the sample treated by the ammonia water-mixed plasma jet was respectively 119 N/m and 446 N/m larger than that of the sample treated by pure helium plasma jet and the untreated sample. • Ammonia water is added into working gas of plasma jets to better modify PTFE. • The ammonia-mixed plasma jets show much better hydrophilization effect than others. • Water contact angle decreases from ∼101° to ∼19° after 120s plasma treatment. • Peel strength with epoxy glue is improved by 431% after the treatment. [ABSTRACT FROM AUTHOR]