Incorporation Fe considerably adjusts Pt electronic structure and further lowers the binding strength of CO intermediates on Pt sites. Moreover, ordered PtFe structure exhibits stronger strain, ...ligand and synergistic effect between Pt and Fe compared to the disordered PtFe due to the favorable crystallographic phase.
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•Pt can be converted to structure-controlled PtFe via NaCl space-confined annealing.•PtFe structure can be regulated from disorder to order via altering Fe content.•The geometric/electronic nature in ordered and disordered PtFe is quite different.•The strain, charge and synergistic effect in ordered PtFe structure is stronger.
Rationally regulating compositions and atomic arrangements is essential to tune the geometric and electronic structures of Pt alloy nanoparticles (NPs), thus largely optimizing their electrocatalytic performance towards methanol oxidation reaction (MOR). Herein, we present a facile alloying-ordering strategy to directly convert pure Pt NPs into size-controlled PtFe ordered intermetallic NPs by virtue of thermal interdiffusions under an easily-removable NaCl cover. And the disordered counterparts can be also obtained by simply varying the feeding contents of Fe precursors. Experimental results indicate that incorporating Fe considerably adjusts Pt electronic structure and further lowers the binding strength of CO intermediates on Pt sites. Moreover, the strain, ligand and synergistic effect between Pt and Fe are much stronger in ordered PtFe catalyst than in the disordered one, endowing the ordered PtFe with an obvious higher activity, stability and anti-CO poisoning for methanol oxidation as compared to disordered PtFe as well as commercial Pt/C.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Herein, 25 kinds of polytetrafluoroethylene (PTFE) composites with solid-liquid synergetic self-lubricating property were prepared by filling PTFE matrix with hollow SiO2 particles and lubricating ...oil (PAO6). Hollow SiO2 particles containing PAO6 acting as lubricating fillers were applied to enhance the tribological performances of PTFE matrix. The generated PTFE composites displayed solid-liquid synergetic self-lubricating property and could achieve ultralow friction. Factors such as the cold-pressed pressure and the SiO2 content that affect the tribological performance of the composites were investigated in detail. The compactness of the composites was enhanced when the cold-pressed pressure increased. The porosity of the composite with 25 wt% SiO2 decreased from 38.2% to 14.3% when the cold-pressed pressure was increased from 10 MPa to 50 MPa. As the cold-pressed pressure was increased, the antiwear performance of the composites was enhanced but their antifriction performance become worse. The composites containing PAO6 achieved lower coefficient of friction (COF) and smaller wear rates than composites without PAO6. The COF value decreased from 0.143 (pure PTFE) to an ultralow value of 0.037 (composite 5%-10 MPa-oil). The enhanced antifriction performance of the composite was associated with the synergistic lubricating effect of the liquid lubricant of PAO6 and the lubrication of the PTFE matrix. All the prepared PTFE/SiO2/PAO6 composites exhibited excellent antifriction performance and improved antiwear property and thus can be used to fabricate a new kind of self-lubricating materials.
Fig. Solid-liquid synergetic self-lubricating mechanism of PTFE/SiO2/PAO6 composites. Display omitted
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PTFE is used as an inner coating material in non-stick cookware. This unique polymer coating prevents food from sticking in the pans during the cooking process. Such cookware is also easy to wash. At ...normal cooking temperatures, PTFE-coated cookware releases various gases and chemicals that present mild to severe toxicity. Only few studies describe the toxicity of PTFE but without solid conclusions. The toxicity and fate of ingested PTFE coatings are also not understood. Moreover, the emerging, persistent, and well-known toxic environmental pollutant PFOA is also used in the synthesis of PTFA. There are some reports where PFOA was detected in the gas phase released from the cooking utensils under normal cooking temperatures. Due to toxicity concerns, PFOA has been replaced with other chemicals such as GenX, but these new alternatives are also suspected to have similar toxicity. Therefore, more extensive and systematic research efforts are required to respond the prevailing dogma about human exposure and toxic effects to PTFE, PFOA, and GenX and other alternatives.
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•Effect of fibrillated PTFE and PTFE particles on TPU foam was compared.•Rheological behavior of TPU/PTFE composites under CO2 was investigated.•Fibrillated PTFE decreased shrinkage ...ratio of TPU foam to some extent.•0.5 wt% fibrillated PTFE enhanced compressive strength of TPU foam by 100%.•PTFE made TPU change from hydrophilic to hydrophobic.
Effects of different morphologies and contents of polytetrafluorethylene (PTFE) on the foaming and rheological behavior of thermoplastic polyurethane (TPU) and mechanical properties of TPU/PTFE composite foams were investigated. High-pressure rheological test results showed that fibrillated PTFE had a more significant effect on the reinforcement of TPU than PTFE particles. In addition, the TPU/fibrillated PTFE composite foam exhibited good compression recovery properties, and its compressive strength was 109% that of TPU/PTFE composite foam with PTFE particles. Furthermore, with increasing PTFE content, TPU/PTFE foams exhibited higher compressive strength and good compression recovery properties. Retention of maximum stress was approximately 90%, and the strain recovery rate of the TPU/PTFE foam was approximately 80% of the initial value after 50 compression cycles. Moreover, the shrinkage ratio of the TPU foam decreased with increasing PTFE content, and fibrillated PTFE enhanced the hydrophobicity of TPU.
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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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•A novel carbon nanotube immobilized PTFE membrane is presented for water desalination via DCMD.•Functionalization of CNTs enhanced water vapor flux.•Mechanism of water vapor ...transport in the presence of CNTs is proposed.•The presence of CNTs prevented the drop in water vapor flux at higher salt concentration.
Carbon nanotube (CNT) enhanced direct contact membrane distillation (DCMD) is presented for water desalination. We investigated the immobilization of CNTs on a polytetrafluoroethylene (PTFE) membrane. The presence of CNTs on the hydrophobic membrane favorably altered the water–membrane interactions to promote water vapor transport while preventing salt water penetration into the membrane pores. For a salt concentration of 34,000mgl−1 and at 70°C, the CNT incorporation led to a 54% enhancement in permeate flux, which was as high as 69kg/m2h.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Polytetrafluoroethylene (PTFE) is an attractive membrane material due to its superior chemical resistance, thermal stability and strong hydrophobicity. However, PTFE hollow fiber membranes are ...challenging to produce by conventional technique due to the high solvent resistance and high melt viscosity of PTFE. In this study, novel PTFE hollow fiber membranes composed of pure PTFE nanofibers were firstly fabricated via a scalable and environment-friendly method based on emulsion electrospinning with a non-rotating collector and followed by a high-temperature sintering process. The effects of PTFE/PEO mass ratio and sintering temperature on the morphologies and properties of the resulting membranes were investigated. The prepared PTFE hollow fiber membrane shows the excellent characteristics combining the advantages of both electrospun nanofibers membrane and hollow fiber membrane, such as high porosity (more than 82%), self-supporting and superhydrophobicity. The membrane sintered at 380 °C present the highest mechanical strength, which shows the tensile strength, Young's modulus, strain at break of 30.5 Mpa, 53 Mpa, and 315%, respectively. The permeate flux of the prepared PTFE hollow fiber membrane is about 4.6–8.8 times as that of the commercial PTFE hollow fiber membranes, as well as is approximately 3.2–11.6 times higher than the date of the reported PTFE hollow fiber membranes. Additionally, the prepared membrane shows high and stable flux in long-term and rising salinity experiments, indicating it is very promising for membrane distillation (MD) application and even for the treatment of hyper-saline wastewater.
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•Novel hollow fiber membranes composed of pure PTFE nanofibers.•Scalable and environment-friendly method was proposed.•Membranes are high porous, self-supporting and superhydrophobic.•3.2–11.6 times higher than the flux of reported PTFE hollow fiber membranes.•Stable and high flux in treatment of hyper-saline wastewater.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•PTFE hollow fiber membrane was fabricated via electrospinning with no organic solvent.•Pullulan was used as the carrier of the PTFE for electrospinning.•The prepared membrane shows high porous, ...superhydrophobicity and high LEP.•The KOE of the prepared membrane is 1.6–2.4 times higher than commercial membrane.
Polytetrafluoroethylene (PTFE) is increasingly used in membrane applications due to its excellent thermal stability, resistance to chemical degradation and strong hydrophobicity. However, it is difficult to prepare high flux membranes by conventional technology due to its high melt viscosity and solvent resistance. Here, a environment-friendly technology is used to fabricate PTFE hollow fiber membrane via emulsion electrospinning. Pullulan is dope into the PTFE emulsion and employ as the binder of PTFE particles to facilitate the formation of the as-spun PTFE-Pullulan hollow fiber membrane. The expected PTFE hollow fiber membrane is obtained after sintering of the as-spun membrane. No organic solvent is used and no pollutant is discharged during the preparation process. The prepared PTFE hollow fiber membrane shows excellent properties such as superhydrophobicity (contact angle > 150°), high porosity (85%) and excellent mechanical properties (Young's modulus of 39 MPa and fracture strain of 245%). In the deamination test, the experimental mass transfer coefficient of the PTFE hollow fiber membrane reaches 2.4*10−5 m/s when the pH is 11, which is 1.6–2.4 times as that of the commercial membrane. The self-made PTFE hollow fiber membrane shows great potential in the application of membrane deamination.
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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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•Tribocatalysis of homogeneous material was revealed for the first time.•Rubbing multi-size PTFE particles can degrade organic pollutants.•The multi-size PTFE tribocatalysis has high ...durability for degradation of pollutants.•Tribocatalytic mechanism of homogeneous material was proposed.•The tribocatalytically degraded pathway of pollutants was studied.
Recently, tribocatalysis driven by mechanical energy has been developed by rubbing two kinds of different materials. In this work, we firstly demonstrated that the friction of the single material also could initiate the tribocatalysis for degrading organic dyes. Under magnetic stirring, the multi-size granular polytetrafluoroethylene (PTFE) particles were triboelectrically charged, among which the collision between large and small particles would cause high energy electrons on large particles to transfer to small ones. These triboelectric charges on PTFE particles could react with adsorbed oxygen molecules or water to generate reactive oxygen species, and then promoted the degradation process of organic dyes together with oxidant holes. We further investigated the experimental parameters, such as stirring speed, size and quantity of stirring bar, to optimize the tribocatalytic performance. What’s more, the PTFE tribocatalysis possessed high durability for multiple recycling runs with > 90% degradation efficiency of Rhodamine B, as well as well universality for eliminating other pollutants. Finally, we proposed a plausible tribocatalytic mechanism of multi-size granular PTFE according to the detected reactive oxygen species and the determined intermediates. This study provides new insights into tribocatalysis, and demonstrates that the single material with different particle sizes can also be used as catalyst to drive tribocatalytic process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The tribological properties of hybrid polytetrafluoroethylene (PTFE)/aramid fibers 1414 (Kevlar) fabric self-lubricating composite under different conditions was studied. To improve tribological ...properties and the bonding performance of PTFE, the hybrid Kevlar/PTFE fabrics were treated by sodium-naphthalene complex liquid. PTFE/Kevlar fabric composite was prepared by phenolic-epoxy (6:4) resin. Tribological properties of the composite, friction coefficient and wear amount, were analyzed using varying loads and speeds on a friction and wear testing machine. Worn surface morphology and transfer film were observed by Scanning electron microscopy (SEM). The results showed that the coefficient of friction decreased with the decrease of load and the increase of rotating speed. In addition, the composites with higher PTFE content showed better lubricating behavior. The friction coefficient of the composites reinforced by modified fabrics were more stable and the PTFE transfer film remains more complete.
•The hybrid PTFE/Kevlar fabric self-lubricating composites were prepared.•The PTFE surface was carbonized by the treatment, while, Physical properties of Kevlar were not affected.•The surface treatment improves the friction coefficient stability and the PTFE transfer film completeness.•Friction coefficient and the amount of wear increases as the speed increases, however, the contrary is the case with increases of the load.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
