Improving the energy efficiency of mechanical systems and reducing the usage of lubricant oils and related additives are challenging tasks of the 21st century. Consequently, the application of ...tribopolymers increases due to their easy processing (injection moulding) and lower density (mass reduction). Among them are the poly(ether-ether-ketone) (PEEK) and the poly(aryl-ether-ketone) (PAEK) with outstanding mechanical properties, and poly(tetrafluorethylene) (PTFE), a solid lubricant. This work produced powder-like PAEK + PTFE blends (2%–30% PTFE) by low and high-energy grinding processes; then, the specimens were shaped by hot pressing. The morphology and composition of the post-grinding particles were analysed by white light interferometry (WLI), scanning electron microscopy (SEM) and X-ray dispersive energy spectroscopy (EDS). The fractography and thermal analysis of the specimens were performed via SEM-EDS and differential scanning calorimetry (DSC). For tribological evaluation, reciprocating (2Hz, 10 mm) cylinder-on-flat tests were conducted to determine the lubricious regime duration, the friction coefficient (COF) during the steady-state regime, and wear rates, where the worn volumes (specimen and counterbody) were measured by WLI. High-energy grinding leads to smaller and more plastically deformed particles. In addition, the incorporation of PTFE into PAEK is more homogeneous with a higher crystalline degree. The self-lubricating effect is manifested from 5% of PTFE, and the best results are reached for 15% of solid lubricant, with an average wear rate of 9.4 × 10−16 mᶟ/Nm and COF of 0.08, against 5.3 × 10−14 mᶟ/nm and 0.32 for pure PAEK, respectively.
•The two mixing methods used to produce the blend (PAEK + PTFE) resulted in completely different blends structural morphology.•But high energy method induces the formation of polymers with higher crystallinity degrees.•Higher tribological performance was reached from 5% of PTFE concentration.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Conventional textiles keep the body warm and provide an aesthetic appearance for human beings, while they are insufficient for military and civil applications in harsh environments. Multifunctional ...textiles that are capable of creating infrared (IR) camouflage, electromagnetic interference (EMI) shielding, and personal warming by interacting with both IR and microwave electromagnetic waves (EMWs) are developed. The inorganic–organic polytetrafluoroethylene (PTFE)/Ag/PTFE (IO‐PAP) building blocks are deposited on the polyurethane (PU)‐coated textiles using an eco‐friendly magnetron sputtering technique, where a smooth and durable Ag layer is grown, circumventing the large roughness and less connection between fibers in conventional textiles. Using the IO‐PAP building blocks, the ultralow IR emissivity and the ultrahigh microwave reflectance are achieved for effective IR camouflage and EMI shielding, respectively, together with satisfactory mechanical robustness. The EMI shielding effectiveness is further improved to 73 dB through employing a Fabry–Pérot‐based double‐sided PAP (D‐PAP) architecture. The D‐PAP‐coated textiles also exhibit personal warming, increasing the skin temperature by 2.7 °C compared with conventional cotton through reflecting thermal radiation of human bodies and mitigating radiative heat loss from textiles. This work will inspire the ultra‐band EMW engineering of textiles for realizing advanced functionalities in a way of eco‐friendly and scalable manufacture.
Multifunctional textiles are developed for infrared camouflage, microwave electromagnetic interference shielding, and personal warming by simultaneous interaction with infrared and microwave electromagnetic waves. An eco‐friendly magnetron sputtering technique is employed to prepare an inorganic‐organic polytetrafluoroethylene (PTFE)/Ag/PTFE (IO‐PAP) multilayer structure on the polyurethane‐coated textiles, circumventing the problems of textile's multi‐functionalization due to large roughness and less connection between fibers.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A gas diffusion layer (GDL) is the key component in a proton exchange membrane fuel cell (PEMFC), where transportation of reactants and oxidants to electrodes and removal of water from the cell ...occur. Accurate prediction of the effective transport properties of GDL is important in understanding its effects on PEMFC performance. However, prediction of GDL behavior is challenging because of the complex geometries involved. Hence, microstructure modelling of GDL is highly beneficial in this condition. This article reviews numerous research endeavors that focused on GDL modelling and the parameters that affect the GDL microstructure. This review aims to understand how each parameter affected the GDL performance. The highlighted parameters in this article are fiber diameter, GDL thickness, porosity, and the effect of polytetrafluoroethylene (PTFE).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this research, the novel materials based on polyamide (PA), polytetrafluoroethylene (PTFE), and olefinic oil molecules are produced as a solid lubricant in metal‐plastic sliding contacts or ...sacrificial elements in metal–metal sliding contacts. For these applications, high durability of the compound material combined with low wear is required for long‐term use under high friction and mechanical loads. Earlier studies of IPF have shown that chemical bonding between the polymer matrix and the solid lubricant is mandatory to meet these requirements. For this purpose, the compounds are fabricated by a novel two‐step reactive processing procedure based on radiation‐modified PTFE, which exhibits reactive‐functional groups (COOH) and persistent perfluoroalkyl‐(peroxy)‐radicals (COO·). The PA‐PTFE‐oil‐cb compound materials (cb: chemically bonded) are analyzed by differential scanning calorimetry (DSC) concerning breaking down behavior and Fourier‐transform infrared spectroscopy with regards to the chemical covalent bonding state between the three components. Results of scanning electron microscopy investigations in correlation with DSC show that chemical bonding between PA and PTFE‐oil‐cb leads to a homogeneous distribution of solid lubricant particles in the three various PA matrices. Due to the chemical coupling, the compounds offer almost comparable or improved mechanical properties in the case of toughness compared to non‐modified PA.
This project's scope is the development of novel chemically bonded tribomaterials based on polyamides (PAs), irradiated polytetrafluoroethylene (PTFE), and oil molecules. The materials are processed by a two‐step of reactive‐extrusion. This article presents the compound's morphology, crystallization behavior, and mechanical properties. It was found that PA12‐(Z7321) offered the best coupling degree and is the best suitable matrix polymer for chemical coupling PA‐PTFE‐oil.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Polyimide (PI)-MoS2/PTFE composite was fabricated and its tribological properties were investigated under different conditions, i.e., vacuum, ex-situ AO irradiation and in-situ AO irradiation. The ...friction pair was 400 C ball on the disk of this composite. By using SEM, AFM, XPS and angle-resolved XPS, the characterizations of morphology, topography and chemical components at the sliding interface were studied comprehensively. Because the effects were just limited into the very top surface, the ex-situ AO irradiation didn’t deteriorate the tribological properties. Nevertheless, in-situ AO irradiation persistently interfered the formation of shear layer at the track and transfer film at the scar as the sliding was proceeded, which resulted in severe deterioration of the tribological performance. It was determined there were negative synergistic effects between friction and AO irradiation, which suggested in-situ friction under AO environment was more scientific and practical for the investigation of exposed lubricants in LEO.
•Friction behaviours of PI-MoS2/PTFE composite was investigated by a combination of a vacuum tribometer and an AO irradiation device.•A strong negative synergistic effect on the tribological interface from the friction and AO irradiation.
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GEOZS, IJS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZAGLJ
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•OH untilization rate was greatly enhanced at pulse current mode.•Energy-saving was up to 76.0% under pulse current with similar removal performance.•Mechanism and superiority of ...pulse electrochemical oxidation have been elaborated.•The impact of mass transfer was systematacially evaluated using a DCBR.
This study focused on the electrochemical oxidation of Acid Blue 9 (AB 9) under direct and pulse current modes using a Ti/SnO2-Sb/α,β-Polytetrafluoroethylene-Fe-PbO2 (PTFE-Fe-PbO2) anode. The results showed that 99.0% of AB 9 and 68.9% of COD could be eliminated at initial pH of 5, initial AB 9 concentration of 100 mg L-1, pulse frequency of 4000 Hz, current density of 20 mA cm−2 and pulse duty cycle of 50% after 120 min of electrolysis. The pulse electrochemical oxidation of AB 9 at the investigated conditions followed pseudo-first-order kinetics. Compared with the direct current mode, 76.0% of energy consumption could be saved at pulse current mode. The effect of mass transfer and electrode distance on the pulse electrochemical oxidation of AB 9 was also investigated in terms of mass transfer coefficient and effectiveness factor, the results showed that the reduced electrode distance was beneficial to improve the mass transfer and oxidation efficiency, as well as the energy efficiency. LC-MS analysis revealed that benzenesulfonate group, C-N and C-S bonds in AB 9 molecule were initially cleaved under the attack of ⋅OH, then some carboxylic acids were formed and eventually mineralized to CO2 and H2O. Therefore, pulse electrochemical oxidation with a PTFE-Fe-PbO2 electrode might be a promising alternative to enhance the practicability of electrochemical treatment for dye wastewater.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•PDA/PTFE and PDA/PTFE + 0.25 wt% graphite particle coatings were applied to 60NiTi.•The coatings reduced the coefficient of friction by 7.2 times.•The coatings reduced the wear rate ...of 60NiTi and the counterface ball substantially.•Adding only 0.25 wt% graphite particles to PTFE increased the durability 2.4 times.•The enhanced coating adhesion and transfer film are key reasons for the improvement.
60NiTi has unique combinations of high shock load and corrosion resistance, which is suitable for load-bearing applications exposed to chemically aggressive environments. However, it exhibits poor tribological properties in dry sliding contact conditions. Polydopamine (PDA)/polytetrafluoroethylene (PTFE) coatings are shown to reduce friction and wear of 60NiTi significantly. In this study, using Si3N4 balls as the counterface material, the effects of adding graphite particles (GrP) to the PTFE layers of the PDA/PTFE coatings on the sliding properties of 60NiTi were studied. The obtained results were compared to those of the PDA/PTFE coated and uncoated 60NiTi. The results showed that both types of coatings significantly decreased the coefficient of friction (COF) and wear of the 60NiTi substrates and the wear of the counterface balls. The PDA/PTFE + 0.25 wt% GrP coatings have less porosity and approximately 2.4 times durability when compared to the PDA/PTFE coatings. Scratch tests on the coated surfaces also revealed better adhesion strength, higher load-carrying capacity, and enhanced transfer films on the counterface balls for the PDA/PTFE + 0.25 wt% GrP coatings. The less porosity, the enhanced adhesion strength, and the transfer film contributed to the longer wear life of PDA/PTFE + 0.25 wt% GrP coatings on 60NiTi.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper, various dry lubricants made of a polyamide (PA) matrix and two different grades of radiation-modified PTFE, which are chemically bonded to the matrix by reactive melt extrusion, are ...examined regarding their tribological suitability and compared to a PA-PTFE reference compound with non-modified PTFE. For this purpose, a block-on-ring test rig was used under ambient conditions, where the block made of dry lubricant is sliding on a steel ring made of 16MnCr5 with constant sliding speed. Results of tribological tests on the block-on-ring test rig such as wear and friction depending on the contact pressure are presented. In addition to that, analyses of the layer formation of the lubricants on steel counterparts are shown. An essential finding of the investigations is that the mass thickness on the tribologically stressed surfaces to be lubricated with the dry lubricant is not directly related to the compound wear, but rather depends on the pressure in the steel-compound contact. Furthermore, examinations showed that an increase of pressure in the block-ring contact does not lead to an increase of the amount of dry lubricant material on the steel surface.
•Irradiated PTFE significantly affects the tribological behavior of Polyamide (PA).•Compounds based on the PA46 matrix wear less than compounds with PA66 matrix.•The coupling grade of PTFE to PA influences the tribological behaviour of compounds.•The lubricant quantity deposited on steel doesn't correlate with the lubricant wear.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
