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The dissolution behaviors of the precipitates in FB2 steel after solid solution treatment at 900, 1000, and 1100 °C for 8 h and at 1100 °C for 2, 5, and 10 h are studied by optical microscopy, scanning electron microscopy, X‐ray diffraction, and electrolytic extraction experiments. In the experimental results, it is shown that with the increase of solid solution temperature, the precipitates dissolve obviously, and the martensite lath bundle size and grain size increase. After solid solution treatment at 1000 °C, M23C6 dissolves completely. After solid solution treatment at 1100 °C, BN is generated. With the extension of solid solution time, the precipitates dissolve significantly, the grain size increases, and the number density and volume fraction decrease. From the perspective of microstructure, precipitates evolution, and energy saving, the best solid solution process for FB2 steel is 1100 °C for 8 h. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE)/Kevlar fabric or fabric composites with excellent tribological properties have been considered as important materials used in bearings and bushing, for years. The components’ (PTFE, Kevlar, and the gap between PTFE and Kevlar) distribution of the PTFE/Kevlar fabric is uneven due to the textile structure controlling the wear process and behavior. The components’ area ratio on the worn surface varying with the wear depth was analyzed not only by the wear experiment, but also by the theoretical calculations with our previous wear geometry model. The wear process and behavior of the PTFE/Kevlar twill fabric were investigated under dry sliding conditions against AISI 1045 steel by using a ring-on-plate tribometer. The morphologies of the worn surface were observed by the confocal laser scanning microscopy (CLSM). The wear process of the PTFE/Kevlar twill fabric was divided into five layers according to the distribution characteristics of Kevlar. It showed that the friction coefficients and wear rates changed with the wear depth, the order of the antiwear performance of the previous three layers was Layer III>Layer II>Layer I due to the area ratio variation of PTFE and Kevlar with the wear depth.

The paper g describes a model meant for analysis of the wear geometry of plain woven fabric composites. The referred model consists of a mathematical description of plain woven fabric based on Peirce’s model coupled with a stratified method for the solution of the wear geometry. The evolutions of the wear area ratio of weft yarn, warp yarn and matrix resin on the worn surface are simulated by MatLab software in combination of warp and weft yarn diameters, warp and weft yarn-to-yarn distances, fabric structure phases (SPs). By comparing theoretical and experimental results from the PTFE/Kevlar fabric wear experiment, it can be concluded that the model can present a trend of the component area ratio variations along with the thickness of fabric, but has a inherently large error in quantitative analysis as an idealized model.

It is of great significance to improve the tribological performances of self-lubricating system to reduce the exfoliation of abrasive particles. In this work, tribological performances of Si3N4–PTFE–EP self-lubricating composites with surface-modified micro/nano-Si3N4 (20 nm, 100 nm, 500 nm, 1–3 μm, and 10 μm) prepared by high-pressure (3 GPa) compression molding are investigated systematically. The results show that although the surface modification of nano-Si3N4 can improve tribological performances of Si3N4–PTFE–EP composite, Si3N4 particle size is the more critical factor. When Si3N4 particle size is 10 μm, the tribological performances of 70M–Si3N4–30PTFE–EP, 50M–Si3N4–50PTFE–EP, and 30M–Si3N4–70PTFE–EP composites are optimal. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) layered bismuth (Bi) with a thickness-dependent direct bandgap (0–0.55 eV) has attracted ever-increasing research interest in electronics, energy storage and conversion devices. However, few-layer Bi nanosheets (NSs) are easily oxidized under ambient conditions. Searching for a convenient and low-cost strategy to produce high-quality few-layer NSs in large scale is of great importance to prompt its practical applications. Herein we report that the liquid-phase exfoliation method with acetone solvent is suitable for fabricating 2D thin and low-oxidized Bi NSs. Next, we assemble the produced Bi NSs into all-solid-state supercapacitors (ASSPs). The as-prepared devices exhibit a volumetric capacitance of 36.8 F cm−3, together with excellent volumetric energy and power densities. The volumetric capacity can be further enhanced up to 68.7 F cm−3 by compositing with CNTs. The maximum volumetric energy and power densities are 9.5 mW h cm−3 and 203.2 W cm−3, respectively. Moreover, we demonstrate that the Bi/CNT devices exhibit outstanding flexibility (79.0% retention of the initial capacitance at 180° bending) and superior cycling stability (82.2% retention of the initial capacitance after 20 000 cycles), demonstrating the great potential of Bi/CNTs for high-performance flexible ASSPs. [ABSTRACT FROM AUTHOR]

The tribological performance of ceramic–polymer composites prepared by high-pressure (3 GPa) compression molding of silicon nitride (Si3N4) and polytetrafluoroethylene (PTFE) with epoxy resin (EP) binder was investigated under dry friction conditions. Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy, and energy-dispersive spectroscopy (EDS) were utilized to characterize Si3N4-PTFE-EP composites. The Vickers hardness and shore hardness were tested and the thermal stability was evaluated by thermogravimetric analysis (TGA). The results indicate that the lowest wear rate reaches 10−7 mm3 (Nm)−1 and the lowest friction coefficient is about 0.06. With an increase in the PTFE mass fraction, the main wear form gradually changes from abrasive wear to adhesive wear, but fatigue wear always exists. [ABSTRACT FROM AUTHOR]

Frictional failure is inevitable for friction pairs. A common sense about the frictional failure of steel-polymer composite friction pair is that the polymer composites are the primary failure part rather than the steel counterpart. However, an opposite case was newly found in the case of fabric self-lubricating liner (Kevlar/PTFE hybrid composite) spherical plain-bearing under elevated load: the steel counterbody suffered a fatigue failure before the fabric composite fails, which resulted in the final failure of the bearing. This paper investigated such fatigue failure of surface chrome plated 45# steel by systematically studying the wear characteristics of 45# steel and fabric composite, the stress distribution of the 45# steel and fatigue features within cross section of the 45# steel. Results showed that wear characteristics of both fabric composite and 45# steel exhibited regional characters. Failure mechanism of the 45# steel was found to be fatigue failure (mainly fatigue pitting), which was revealed by mathematical analysis of the stress distribution of the 45# steel and the fatigue cracks found within subsurface of the cross section of the 45# steel. [ABSTRACT FROM AUTHOR]

Yarn twist in textile technology is an important characteristic since it considerably affects the properties of knitted or woven fabrics. Many researchers have investigated the effect of staple-spun yarn twist on the properties of the yarns and fabrics. However, the effects of twist level of Kevlar® 29 filament yarn on the properties of yarn and its resin-impregnated self-lubricating fabric liner are not fully known yet. In this study, we have investigated the effects of Kevlar® 29 twist level on the tensile and tribological properties of the fabric liner (Kevlar® 29/polytetrafluoroethylene fabric-resin composite). Two unexpected findings about the effect of yarn twist have been observed, namely (1) asynchronous twist effect on the yarn’s and the liner’s tensile strength and (2) dissimilar yarn twist effect on the liner’s performance. These findings are mainly attributed to the synergic contributions of the yarn twist and strength and the interaction of the resin with the yarn orientation in the woven fabric structure of the liner. [ABSTRACT FROM AUTHOR]

The filling combination of polytetrafluoroethylene (PTFE)/Cu/Al2O3 filled poly(methyl methacrylate) (PMMA) based composites aiming at low friction and wear is optimized based on L9(34) by Taguchi method. The worn morphologies of PMMA based composites are analyzed by scanning electron microscopy (SEM). The PTFE transfer film and the wear debris on the steel ball surface are analyzed by SEM and X‐ray spectroscopy. It is observed that the friction and wear of PMMA can be obviously decreased by filling with PTFE, Cu, and Al2O3. PTFE has the most significant but Cu has the negligibly smallest contribution on both the friction coefficient and the wear rate. The lower friction coefficient (<0.2) appears by the combination of the mass ratio of PTFE larger than about 4.5% and the mass ratio of Al2O3 lower than ∼7.5%. The lower wear rate (<5 × 10−5 mm3/Nm) appears by the combination of the mass ratio of PTFE larger than about 5% and the mass ratio of Al2O3 lower than ∼8%, but it does not include that PTFE is greater than about 8.5% and Al2O3 is less than about 1.5%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46705. [ABSTRACT FROM AUTHOR]

The influence of strain rate on dynamic softening and texture orientation of Ti55511 in the β single-phase region are investigated. Hot compression experiments were enforced at 880–920°C, strain rates of 0.001–1 s−1 and the strain of 0.60. The continuous dynamic recrystallization mainly happens at 0.001–0.01 s−1, which is generated by the progressive rotation of the subgrain orientation, and accompanied by discontinuous dynamic recrystallization that is generated by the strain induced boundary migration. DDRX grains with HAGB migration nucleation bulge are produced at higher strain rates of 0.1–1 s−1. DRV is the main deformation mechanism. The DRX nucleation mechanism corresponding to different strain rates plays an important effect on the type and intensity of β texture. The {111}//Z texture consumed by recrystallized grains gradually transforms to {110}//Z and {100}//Z textures at a low strain rate, leading to the diminishment of {111}//Z texture strength slightly. Meanwhile, {110} <1-1x> and cube texture {100} <001> occur to transform with the increasing strain rate. The degree of plastic deformation of <111> and <110> grains is larger and the degree of CDRX is higher. The {110} <111> slip system can accelerate the drastic dislocation interaction to turn <111> soft orientation to <100> hard orientation. [ABSTRACT FROM AUTHOR]