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High-performance anti-wear polyetheretherketone/polytetrafluoroethylene (PEEK/PTFE) blends have drawn much attention over the past few years, owing to their wide range of potential applications. However, a convenient and effective method to prepare such blends with superior mechanical and tribological properties is still lacking. In this work, we propose a promising approach that uses melt-processable PTFE (MP PTFE), instead of conventional PTFE, to prepare anti-wear blends. MP PTFE, with melt flow abilities under appropriate conditions, can disperse homogeneously in PEEK, enhancing both the mechanical and tribological properties of the PEEK/PTFE blend. To prove this postulation, in this work, both MP PTFE and commercial PTFE were blended with PEEK, separately, and the effects of PTFE type and content on the tensile and tribological properties of the blends were studied. The results showed that, although the addition of commercial PTFE to PEEK could increase the wear resistance, it decreased the tensile strength of PEEK significantly. Compared to the blends with commercial PTFE, the blends with MP PTFE exhibited better tribological performance and higher tensile strength for PTFE content below 10 wt%. It was confirmed that the better dispersion of MP PTFE in PEEK endowed the blends with higher tensile strength. The surface analysis indicated that the MP PTFE could readily migrate to and enrich the surfaces of the blends. The relatively high PTFE content on the surface favored the formation of tribo-films, enhancing the tribological properties of the blends.

Silicon (Si) anodes display high specific capacity but mostly suffer from poor cycling ability owing to their dramatic volume expansion during the discharge/charge process. An effort was devoted to...

In order to recognize the characteristic thermal transitions of polytetrafluoroethylene (PTFE) occurring at 19 °C and 30 °C, PTFE is irradiated on electron beam accelerator at room temperature and analyzed by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results suggest that the two transition temperatures decrease considerably with increasing irradiation doses. Based on the results of structural analysis, the decrease of the two transition temperatures is supposed to be highly relevant to the structural changes. In particular, the content and structure of the side groups generated in PTFE are responsible for the variations of the two thermal transitions after irradiation, offering fundamental insights into the reaction mechanisms of PTFE during irradiation.

Commercialization of silicon (Si) anodes remains a significant challenge due to their severe volume change and low intrinsic conductivity during cycling. To address the limitations, we herein report a facile strategy to design and prepare nitrogen-doped yolk-shell Si@void@C/CNTs microspheres via spray drying followed by carbonization and etching procedure. In the resulting architecture, the constructed void could act as a volumetric expansion-relieved space, which not only provides a buffer area for adapting the volume expansion of Si nanoparticles, but also significantly facilitates ions transport and offers more ion-accessible area upon cycling. The randomly interlinked carbon nanotubes (CNTs) networks, together with the N-rich amorphous carbon matrix cooperatively provide fast electron transport pathways and high electrical conductivity. Benefitting from the synergistic features, Si@void@C/CNTs anode exhibits a high discharge capacity of 1034 mA h/g at 200 mA/g after 500 cycles, and stable cycling performance with a reversible capacity of 680 mA h/g at 500 mA/g after 500 cycles, and superior rate capability of 204 mA h/g at 4 A/g. The novel approach proposed for Si anodes demonstrates promising prospects in developing high-capacity anode materials for next-generation lithium-ion batteries.

To study the effect of irradiation on PTFE structure and prepare modified PTFE micropowder, PTFE was irradiated with dose up to 4 MGy in oxygen at room temperature. The structures of both irradiated and unirradiated PTFE samples were comparatively characterized by IR, XPS, Raman spectra and XRD measurement. The results showed that new groups of acyl fluoride (COF), carboxylic acid (COOH) and trifluoromethyl (CF3) were formed under heavy radiation exposure in oxygen. In addition, the expansion of crystallite size or crystal lattice was first reported for the irradiated PTFE. The formation of new chemical groups and the expansion of crystallite size were elucidated by structural changes occurring in irradiation.

Developing high-capacity anode materials is urgent for next-generation lithium-ion batteries (LIBs) with the increasing need of larger scale applications. In order to obtain suitable anode materials, nitrogen-doped porous carbon microspheres (NPCMs) were prepared via spray drying followed by carbonization using chitosan as both carbon and nitrogen sources. The structure and properties of NPCMs were characterized by thermogravimetric, Raman spectroscopic, x-ray diffraction, scanning electron microscopic, transmission electron microscopic as well as x-ray photoelectron spectroscopic analysis, and the electrochemical performance of NPCM electrodes were also evaluated. The results show that the diameter of the obtained microspheres is 1-7 μm. When used as the anode material, the NPCMs display a reversible capacity of 443 mAh g-1 at 100 mA g-1 after 120 cycles and maintain a high capacity of 377 mAh g-1 at 1 A g-1 after 500 cycles. Even at a high current density of 4 A g-1, a discharge capacity of 256 mAh g-1 can also be obtained. The excellent rate performance and long cycle life of the electrode might be ascribed to the nitrogen-doping, porous and amorphous structure of NPCMs. The results suggest that the prepared NPCMs have the potential to be used as a promising anode material for high-capacity LIBs.

This prospective randomized study compared acute and chronic anterior cruciate ligament (ACL) reconstruction using ligament advanced reinforcement system (LARS) artificial ligament in young active adults with a 5-year follow-up.Fifty-five patients were enrolled in this study and divided into two groups based on the elapsed time between the injury and reconstruction: the acute group (3-7 weeks) and the chronic group (6-11 months). The clinical outcomes were evaluated using the Lysholm knee scoring scale, the Tegner activity rating, a KT-1000 Arthrometer, and the International Knee Documentation Committee (IKDC) scoring system. Isokinetic strength of the quadriceps and hamstring was assessed using the Biodex System 3 isokinetic dynamometer.Anterior laxity was decreased and quadriceps/hamstring muscle strength was increased in the acute group compared to the chronic group (p0.05). There were no statistically significant differences in Lysholm scores, Tegner activity scores, and the IKDC evaluation form between the two groups.These results suggest that earlier ACL reconstruction using a LARS artificial ligament may provide an advantage in the treatment and rehabilitation of ACL rupture.

In the previous articles concerning the treatment of poly(tetrafluoroethylene) (PTFE) with potassium permanganate/nitric acid mixture, the conversion of a hydrophobic to a hydrophilic surface was partially assigned to the defluorination of PTFE and then the introduction of carbonyl and hydroxyl groups into the defluorinated sites. In the present work, PTFE sheets were treated with potassium permanganate/nitric acid, and the surfaces before and after treatment were comparatively characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface sediments of the treated PTFE were also determined by atomic absorption spectroscopy (AAS). The results indicate that the conversion of the hydrophobicity to the hydrophilicity on the modified PTFE surface is mainly due to the deposition of hydrophilic manganese oxides which covered the fluorocarbon surface, and no detectable chemical reactions of PTFE occur in the treating process.

Poly(phenylene sulfide ether) and poly(phenylene sulfoxide ether sulfide ether) (PPSOESE) were successfully prepared and their structures were proved by several analytical techniques in the present work. The molecular weight (MW) of PPSOESE, a soluble polymer in common organic solvent at room temperature, was determined by gel permeation chromatography. Based on the conversion reaction of the two polymers, the MW of PPSE was calculated and correlated with its intrinsic viscosity. As a result, the Mark-Houwink equation for PPSE was concluded. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The perfluorinated ethylene-propylene (FEP) having unstable end groups (–COOH, –COF and –CF=CF2) were stabilized via esterification with short-chain alcohols. The effect of different alcohols on the esterification of FEP was evaluated by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis with mass spectrometry (TGA-MS). The results of IR indicated that the end-capping using methanol at 140 °C (FEP-M140) got the much better effect in converting the labile end groups of FEP into –COOCH3 group with high stability, which was further proven by TG-MS that more weight loss together with more evolved CO2 gas for FEP compared with FEP-M140 were detected. It was very visual that more bubbles caused by the evolved gas distributed in FEP than FEP-M140 films during hot processing, further confirming the end-capped FEP displayed better thermal stability than the uncapped one.

Thermal degradation of poly(phenylene sulfide ether) (PPSE) was investigated by using thermogravimetry (TG) under air and nitrogen atmosphere. It was found that the existence of oxygen depressed the thermal stability of PPSE and changed the mechanism of thermal degradation. The influences of molecular weight and heating rate on the decomposition of PPSE were also investigated under N2 atmosphere. The results showed that the thermal stability of PPSE was excellent and can be further enhanced by increasing molecular weight. A simple kinetic model concerning two parallel reactions in overall temperature range was proposed to describe the thermal degradation process of PPSE in nitrogen. Kinetic analysis of the dynamic TG curves for PPSE was carried out by using Kissinger, Flynn–Wall–Ozawa, and Coats–Redfern methods. The kinetics of PPSE degradation displayed that the two parallel reactions were in accordance with the first-order equation. The kinetic model was further validated by comparing the experimental and calculated results. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

High molecular weight poly(phenylene sulfide ether) (PPSE) was successfully synthesized by reaction of 4,4′-dihydroxy diphenyl sulfide with 4,4′-dichloro diphenyl sulfide in N-methyl-2-pyrrolidone (NMP). The influence of polymerization conditions on the intrinsic viscosity and yield of PPSE was investigated and the optimized reaction condition was concluded. Reactions at about 180°C for 6 h along with sodium benzoate as an additive and monomer concentration of 0.588 mol/L NMP were found to produce the highest intrinsic viscosity (0.55 dL/g). Longer reaction time and/or higher temperature reduced the intrinsic viscosity and yield of the resulting product, probably due to side reactions, such as reductive dehalogenation and chemical degradation. X-ray diffraction indicated that the polymer possessed of orthorhombic cell and had a high crystallinity of 65.8%. The high molecular weight PPSE is a crystalline polymer with Tm of 252°C and Tmc of 224°C. The polymer shows good chemical resistance, but is soluble in organic amide, halo-hydrocarbon and oxohydrocarbon solvent at a temperature over 150°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

A homogenous membrane composed of chitosan (CS), sodium carboxymethyl cellulose (NaCMC) and nano hydroxyapatite (n-HA) was prepared by a gradual electrostatic assembling (GEA) method. The physical and chemical properties of the membranes with different n-HA contents and CS/NaCMC ratios were characterized by Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and mechanical test. The schematic formation mechanism of the membrane was discussed. The results show that GEA is an effective method to prepare the polyelectrolyte complex (PEC) membrane, in which oppositely charged CS-NaCMC polysaccharides can assemble mildly and gradually through electrostatic interaction to form the membrane framework, while the filled n-HA crystals can regulate the structure stability of the composite membrane. The optimum preparation condition for the PEC membrane can be fixed to a content of 60 wt% n-HA, an equivalent amount of CS to NaCMC and a drying temperature of 60°C. The PEC membrane may have good prospect for guided bone regeneration.

The recent observations of unusual superconductive effects in highly oriented pyrolytic graphite (HOPG) and twisted bi-layer, tri-layer and multilayer graphene materials have attracted an important attention. In this work we present a novel investigation on the relationship between structural ordering and magnetism in HOPG. Orientation dependent X-ray diffraction and temperature dependent magnetometry allowed for the identification of those HOPG samples exhibiting a long-range ordering along the c-axis. ZFC and FC magnetic curves acquired from T ~ 2 K to 300 K revealed a significant temperature-dependent variation of the diamagnetic component. By analyzing the ZFC/FC magnetic-curves (through magnetic moment subtraction methods) we identify the presence of a weak magnetic transition in the T range from 200 K to 2 K. The possible origin of the observed magnetization-trend is interpreted in relation to contributions arising from 1) disorder-rich locally-twisted-interfaces and 2) those internal graphitic sublattices exhibiting negative thermal expansion. Interestingly, magnetization against field measurements acquired at T ~ 50 K (max. field of 150 Oe) revealed the presence of a weak ferromagnetic-like hysteresis. Disappearance of the unusual ZFC/FC signal-splitting was instead found in those magnetic curves acquired from other HOPG samples with higher degree of disorder (short-range-ordering along the c-axis). This second category of samples was found to exhibit a disorder-mediated re-entrant spin-glass-like ferromagnetic behavior.