Polytetrafluoroethylene (PTFE) exhibits excellent potential under aqueous lubrication due to its low water absorption, low friction, and good corrosion resistance. However, its poor wear resistance limits its application. In this paper, PTFE was reinforced with different kinds of ceramic particles, and the physical properties were tested using various methods. The tribological behavior of PTFE composites sliding against a super duplex stainless steel was investigated under deionized water and seawater lubrication. The worn surface was examined by scanning electron microscopy, energy-dispersive spectroscopy, and 3D topography. All four kinds of ceramic fillers promoted the crystallinity of the PTFE matrix. Particle-reinforced PTFE showed better tribological performance under seawater than under deionized water. The fragility of ceramic particles played an important role in the anti-wear performance of the PTFE composites. Breaking and shedding of Si 3 N 4 or SiO 2 particles would generate and aggravate abrasive wear between friction pairs. With the good crush resistance of SiC particles and seawater lubrication effect, the wear rate of the composite decreased by 80% in seawater compared with pure PTFE. The h-BN-filled PTFE showed a good and stable tribological performance under water and seawater because of the low interlaminar shear strength of h-BN.
Polytetrafluoroethylene (PTFE) is a self-lubricating matrix material with low friction coefficient and corrosion resistance but high wear rate. Ceramic particle fillers could effectively improve the tribological properties of PTFE-based composites, reduce its wear rate. However, there has been much debate about anti-wear mechanisms for particle fillers, which mainly focus on wear resistance micromechanism and mechanochemistry approach. In this paper, four kinds of PTFE-based composites filled with micrometer-sized ceramic particles (SiC, Si 3 N 4 , SiO 2 and h-BN) were prepared and tested to explore their tribology properties using a pin-on-disk tribometer. The filler proportions ranged from 5 to 20 wt% in 5 wt% increments were added. The worn surfaces of the composites and transfer films attached on the steel disk were examined by Scanning electron microscopy (SEM), energydispersive x-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) and 3D topographies. Ultralow wear was observed on the PTFE/SiO 2 and PTFE/Si 3 N 4 composites in wear tests, which was attributed to tribochemistry. There were protection films formed on the worn surface, which hindered further transfer of the composites. Meanwhile, adhesion of the transfer film was enhanced by metalchelate salts of perfluorinated carboxylic acids formed by tribo-chemical reactions. The wear rate of PTFE decreased by three orders of magnitude (from 6.25 * 10 −4 to 2.21 * 10 −7 mm 3 /(Nm)) after addition of 20 wt% SiO 2 particles. No chemical reaction was observed on the worn surface of PTFE/ SiC and PTFE/h-BN composites.
As a third-generation semiconductor, silicon carbide power devices are expected to be superior to those made of silicon because of their high voltage resistance, low loss, and high efficiency. So understanding the technology for polishing wafers of silicon carbide is important, which includes studying the structure of the liquid on the surface of silicon carbide. Using molecular dynamics based on Lennard-Jones field, the structure of a water film contained within two silicon carbide (〈001〉 and 〈110〉) walls was analyzed, and found that layers of water appear and change depending on the distance between the two walls. When a double-layer water structure forms, it is affected by the temperature and shear velocity. The conclusion is that when the temperature increases or the shear velocity increases, the double-layer water structure easily transforms into a single-layer water structure, and the pressure between the two solid surfaces gradually falls and may even become negative. This phenomenon significantly depends on the distance between the two silicon carbide walls.
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