[en] Graphical abstract: The composites prepared with the thermal treatment process of stabilization at 280 °C for 4 h with a heating rate of 2 °C min"−"1 in air followed by carbonization at 800 °C for 14 h with a heating rate of 2 °C min"−"1 in argon exhibit the optimal electrochemical properties. - Highlights: • Binder-free LiFePO_4–CNF composite cathode materials are prepared. • The conductive carbon and LiFePO_4 formation take place simultaneously during thermal treatment. • The reaction behavior of the LiFePO_4 precursors during thermal treatment are investigated. • Different thermal treatment processes would generate different electrochemical performance. • Cycling performance and rate capability are improved with a suitable thermal treatment condition. - Abstract: Binder-free LiFePO_4–carbon nanofiber (LiFePO_4–CNF) composites as lithium-ion battery cathode materials are fabricated by electrospinning and subsequent thermal treatments. The thermal decomposition behavior of the electrospun LiFePO_4 precursor–polyacrylonitrile (LiFePO_4 precursor–PAN) nanofiber composites and the reaction of the LiFePO_4 precursors during thermal treatment are investigated. The effects of thermal treatment parameters such as heating rate, temperature, and duration for stabilization and carbonization on the microstructure, morphology, carbon content, crystal structure of the composites, and electrochemical performance of the resultant half-cell are also studied. When the electrospun LiFePO_4 precursor–PAN nanofiber composites are first stabilized in air at 280 °C for 4 h with a heating rate of 2 °C min"−"1 and then carbonized in argon at 800 °C for 14 h with a heating rate of 2 °C min"−"1, the obtained LiFePO_4–CNF composites exhibit optimal electrochemical properties in terms of a higher initial discharge capacity, more stable charge–discharge cycle behavior, and better rate performance. The initial discharge capacity of the composites is 146.3 mA h g"−"1 at a rate of 0.5 C, while exhibiting a stable cycle performance up to 100 cycles. The results demonstrated that the LiFePO_4–CNF composite cathode materials could be a promising candidate for next-generation lithium-ion batteries and the thermal treatment process is a critical step to prepare LiFePO_4–CNF composites with optimal performances

[en] Highlights: • Two-element microstrip antennas were integrated into cylindrical 3D woven composites. • The cylindrical 3DIMAs with the radii of 75, 60, 45 mm were demonstrated. • Electromagnetic performance was simulated and matched well with the tested results. • 3DIMAs-AFd was subjected lower negative impact under the curvature structures. Three dimensional integrated microstrip antennas (3DIMA) can carry substantial external load while functioning as antennas. In this study, cylindrical two-element antennas integrated in three dimensional orthogonal woven glass fiber/epoxy composites with various curvatures are fabricated. The effects of the cylindrical curvature on the electromagnetic performance of the 3DIMAs are simulated using High Frequency Structural Simulator and verified experimentally. The results show that all cylindrical 3DIMAs, with different radii of curvature, namely 75, 60, and 45 mm, exhibit utility return losses of − 20 dB. However, their resonant frequencies and gains are significantly influenced by the curvature as well as the arrangement of the curvature and feeding directions. When the curvature of the cylindrical structure was along the feeding direction of the antenna, the 3DIMAs showed more stable resonant frequencies (around 1.5 GHz), gain values (from 2.37 dB to 1.44 dB) and proper radiation patterns, compared with the antenna with the curvature perpendicular to the feeding direction.

[en] This study investigates the influence of the He/O₂ atmospheric pressure plasma jet (APPJ) and ultrasound treatment on desizing of the blended sizes of starch phosphate and polyvinyl alcohol (PVA) on cotton fabrics. The AFM and SEM results indicate that APPJ treatment can increase the surface roughness of the sized fabrics. The SEM results also reveal that the fiber surfaces are nearly as clean as unsized fiber surfaces after 35 s treatment followed by ultrasound desizing for 20 min at 60 °C. X-ray photoelectron spectroscopy (XPS) analysis indicates that oxygen-based functional groups increase on the surfaces of the plasma treated sized fabrics. The PDR of the sized fabrics treated by APPJ dramatically increases when ultrasound was introduced during the desizing process, and the desizing time and temperature are greatly reduced. Wickability analysis reveals that the capillary height of the fabrics treated by plasma and ultrasound was higher than that of the fabrics treated by plasma and hot washing under different plasma exposure time. Therefore, the combination of the APPJ and ultrasound has shown higher effectiveness in desizing and provides an alternative approach that decreases the water, energy and chemicals consumption.

[en] The effect of fiber-resin interfacial structures (especially three-dimensional (3D) structures) on the delamination resistance of L-shaped beam composites was investigated via hinged loading tensile tests. Four types of structures were woven, and the corresponding reinforced epoxy composites were manufactured through a vacuum-assisted resin infusion (VARI) process. The results revealed that the two-dimensional (2D) laminate and 3D shallow-straight woven composite (3DSSWC) had the similar interlaminar strength and failed via delamination. However, compared with the resistance of these composites, a significantly higher delamination resistance was realized for a 3D orthogonal woven composite (3DOWC) and a 3D shallow-bend woven composite (3DSBWC). This high resistance resulted from the reinforcing fibers (i.e., Z-yarns) in the Z-direction and the considerable yarn waviness of the 3DOWC and the 3DSBWC, respectively. The failure mode of 3DOWC was characterized by interlayer delamination and Z-yarn or weft yarn breakage. Moreover, the failure mode of 3DSBWC was dominated by delamination and weft yarn breakage. Therefore, the 3D orthogonal (3DOW) and 3D shallow-bend (3DSBW) woven structures were quite effective in resisting delamination and, of the structures considered, the 3DSBW structure yielded the best L-shaped beam composite.

[en] Polyethylene (PE) films are treated using an atmospheric pressure plasma jet (APPJ) with He or He/O_2 gas for different periods of time. The influence of gas type on the plasma-polymer interactions is studied. The surface contact angle of the PE film can be effectively lowered to 58° after 20 s of He/O_2 plasma treatment and then remains almost unchanged for longer treatment durations, while, for He plasma treatment, the film surface contact angle drops gradually to 47° when the time reaches 120 s. Atomic force microscopy (AFM) results show that the root mean square (RMS) roughness was significantly higher for the He/O_2 plasma treated samples than for the He plasma treated counterparts, and the surface topography of the He/O_2 plasma treated PE films displays evenly distributed dome-shaped small protuberances. Chemical composition analysis reveals that the He plasma treated samples have a higher oxygen content but a clearly lower percentage of −COO than the comparable He/O_2 treated samples, suggesting that differences exist in the mode of incorporating oxygen between the two gas condition plasma treatments. Electron spin resonance (ESR) results show that the free radical concentrations of the He plasma treated samples were clearly higher than those of the He/O_2 plasma treated ones with other conditions unchanged. (paper)

[en] A conformal load-bearing antenna structure (CLAS) combines the antenna into a composite structure such that it can carry the designed load while functioning as an antenna. In this paper, two types of new 3D integrated microstrip antennas (3DIMAs) with different feeding methods are designed to work at the radar L-band. Different from the conventional CLAS, the radiating patch and the ground plane of the 3DIMA are both composed of woven conductive wires and are bonded into the 3D composite physically by Z-yarns, greatly improving the damage tolerance of the antenna. The return loss of the coaxial-fed antenna is −13.15 dB with a resonant frequency of 1.872 GHz, while that of the microstrip-fed antenna is −31.50 dB with a resonant frequency of 1.33 GHz. Both of the 3DIMAs have similar radiation patterns to that of the traditionally designed microstrip antenna. In addition, an experimental investigation of the impact response of the coaxial-fed 3DIMA was carried out and the results showed the radiation pattern had almost no change even when the antenna received an impact energy of 15 J, exhibiting superior impact resistance to that of a conventional microstrip antenna

[en] This study is designed to systematically investigate how various factors, such as treatment duration, output power, oxygen gas flux, jet to substrate distance, and moisture regain, influence atmospheric pressure plasma etching rate of polyamide 6 (PA 6) films. The etching rate increased as the output power, oxygen gas flux, and moisture regain increased. As the treatment time increased, the etching rate increased first and then decreased. When the substrate was too close or too far from the nozzle, the etching rate was almost not measurable. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) show an increased surface roughness after the plasma treatment. X-ray photoelectron spectroscopy (XPS) shows a decreased carbon content and an increased oxygen content after the plasma treatment. T-peel strength shows an improved bonding strength between the PA 6 films and an adhesive tape after the plasma treatment.

[en] The existence of moisture in the substrate material may influence the effect of atmospheric pressure plasma treatment. Our previous study has found that the employment of ethanol pretreatment and plasma treatment can effectively induce hydrophobic surface modification of cellulose fiber to enhance the compatibility to polypropylene (PP) matrix, and this study aims to investigate the influence of fiber moisture regain on the treatment effect of this technique. Ramie fibers with three different moisture regains (MR) (2.5, 6.1 and 23.5%) are pretreated with ethanol followed by atmospheric pressure plasma treatment. Scanning electron microscope (SEM) shows that the 2.5% MR group has the most significant plasma etching effect. X-ray photoelectron spectroscopy (XPS) analysis indicates an increase of C-C and a decrease of C-O bond in the plasma treated groups, and the largest raise of C-C bond for the 2.5% MR group. The water contact angles of the 2.5 and 6.1% MR groups increase, whereas no significant change is showed in the 23.5% MR group. The interfacial shear strengths (IFSS) measured by microbond pull-out test are raised by 44 and 25% when moisture regains are 2.5 and 6.1%, while presented no apparent improvement at high moisture regain of 23.5%. Therefore, it can be concluded that moisture regain has negative influence on the surface hydrophobization of ramie fibers in the improvement of adhesion property to PP matrix.

[en] The influence of the He/O₂ atmospheric pressure plasma jet pre-treatment on subsequent NaHCO₃ desizing of blends of starch phosphate and poly(vinyl alcohol) on cotton fabrics is investigated. Atomic force microscopy and scanning electron microscopy analysis indicate that the surface topography of the samples has significantly changed and the surface roughness increases with an increase in plasma exposure time. X-ray photoelectron spectroscopy analysis shows that a larger number of oxygen-containing polar groups are formed on the sized fabric surface after the plasma treatment. The results of the percent desizing ratio (PDR) indicate that the plasma pretreatment facilitated the blended sizes removal from the cotton fabrics in subsequent NaHCO₃ treatment and the PDR increases with prolonging plasma treatment time. The plasma technology is a promising pretreatment for desizing of blended sizes due to dramatically reduced desizing time.

[en] To alleviate the enormous volume change problem of tin-based anodes for lithium ion batteries (LIBs), carbon-coated tin dioxide (SnO_2) hollow nanofibers were prepared by means of single-spinneret electrospinning followed by calcination and hydrothermal treatment. By varying the concentration of glucose and the reaction time during the hydrothermal coating process, the final product with different carbon distribution and thickness could be obtained. Galvanostatic charge/discharge was carried out to evaluate them as potential anode materials for LIBs. It was shown that the main effect of carbon distribution was to control the capacity retention rate, and the carbon thickness played the important role in lithium insertion/extraction properties. The optimum composite nanofibers could be prepared with glucose concentration of 10 mg/ml and hydrothermal time of 20 h, the carbon content and the specific surface area of which were 26.15% and 29.4 m"2/g, respectively. And this anode with both the carbon core and deposited thin carbon skin was able to deliver a high reversible capacity of 704.6 mAhg"−"1 and the capacity retention could retain 68.2% after 80 cycles. - Graphical abstract: Based on the electrochemical properties of carbon-coated hollow SnO2 anodes, how the carbon distribution and carbon thickness affect their performance are disscussed in groups. - Highlights: • The hollow SnO_2 nanofibers were carbon-coated by hydrothermal process. • The controlled distribution and thickness of carbon layer can be obtained. • The main effect of carbon distribution was to control the capacity retention rate. • The carbon thickness played the important role in lithium insertion/extraction properties.