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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]

Possessing excellent properties including good biocompatibility, high strength, and stiffness, polyether‐ether‐ketone (PEEK) has significant application values in medical and industrial fields. However, the relatively poor wettability and low adhesion limit its further applications. Atmospheric pressure plasma jet (APPJ) has been utilized for adjusting PEEK properties, but better hydrophilization effect and time stability after treatment are still urgently needed. In this paper, we employ a water‐mixing nitrogen (N2H2O) APPJ to process PEEK, and surface wettability can be effectively improved (contact angle ~18° within 2 min, distance between sample and nozzle outlet: 10 mm) without inducing obvious microstructure damages. Additionally, after storing for 40 days, the sample treated by N2H2O APPJ also possessed better wettability (~54°) compared with that treated by N2 APPJ (~65°). On the basis of this low‐damage and high‐efficient modification method, we perform aging experiments under different conditions (different temperatures 25, −10°C; and low vacuum condition: 50 kPa) to determine a relatively optimum storing condition for this method. The experiment results indicate that low temperature and vacuum are conducive to retaining the plasma‐induced wettability (~34°). The treatment method and storing conditions for PEEK presented here may facilitate the application of PEEK in various fields. [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]

[Display omitted] • A new type of oxygen mixing cold plasma jet is developed to modify metal materials. • The plasma jet can treat various metal materials to be superhydrophilic within 20 s. • The high-efficiency plasma treatment does not cause serious structural damages. • Mechanisms leading to the high-efficiency treatment are systematically studied. Engineering metal materials have been widely developed and applied in aviation, aerospace and biomedicine fields. Wettability improvement of these materials can alleviate problems caused by low adhesion and poor bioactivity, thereby facilitating their practical applications. Compared with other methods, atmospheric pressure cold plasma treatment has better versatility and can efficiently improve wettability without causing serious damages, and has therefore been widely used in polymer hydrophilization. However, when treating metal materials, the cold plasma may induce surface breakdown or have low efficiency. In this paper, we developed a new cold plasma jet by mixing oxygen into working gas to achieve high-efficiency and low-damage modification. When oxygen mixing ratio was 0.4 %, the cold plasma jet could modify TC4 titanium alloy surface to be superhydrophilic within 20 s, which was much more efficient than traditional plasma jet (120 s). We then further investigated the mechanism contributing to higher efficiency, and found that the oxygen-mixing plasma jet did not cause serious damages, while generating more polar groups by higher-concentration active particles, as confirmed by surface energy calculation and optical emission spectra. Besides titanium alloy, the oxygen-mixing plasma jet could also achieve rapid hydrophilization of various engineering metal materials, showing promising application prospects. [ABSTRACT FROM AUTHOR]

Frequently-occurring oil spills and wastewater discharge pose great threats to ecological environment and economy. Although various extreme wettability materials have been designed for separations of oil/water mixtures, most of them tend to involve toxic chemical reagents, thus resulting in second pollution to the environment. This paper develops polydimethylsiloxane (PDMS) meshes with excellent chemical stability, reversible super-wettability and good reusability for efficient gravity-driven oil/water separation. Superhydrophobic PDMS meshes can be fabricated by directly constructing microstructures via laser-textured aluminum sheet templates, and heavy oils/water mixtures can thus be separated. After treated by atmospheric-pressure plasma jet for just 2 mins, the superhydrophobic PDMS meshes become superhydrophilic-underwater-superoleophobic, and separation of light oils/water mixtures can be thereby achieved. More interestingly, the plasma-treated superhydrophilic meshes can recover to be superhydrophobic by heating under 80 °C for 20 mins. Therefore, PDMS meshes with reversible super-wettability can be efficiently prepared, and the separation efficiencies for various heavy/light oils and water mixtures are all above 96%. In addition, the prepared PDMS meshes show excellent separation ability under harsh conditions including hot water, acidic and salty conditions, having great application potential in oil/water separation field. [Display omitted] [ABSTRACT FROM AUTHOR]