Fly Ash-Incorporated Polystyrene Nanofiber Membrane as a Fire-Retardant Material: Valorization of Discarded Materials.

Reusing or recycling waste into new useful materials is essential for environmental protection. Herein, we used discarded polystyrene (PS) and fly-ash (FA) particles and a fabricated fly-ash incorporated polystyrene fiber (FA/PS fiber) composite. The electrospinning process produced continuous PS fibers with a good distribution of FA particles. The prepared nanofibers were characterized by state-of-the-art techniques. The performances of the composite nanofibers were tested for fire-retardant applications. We observed that the incorporation of FA particles into the PS fibers led to an improvement in the performance of the composite as compared to the pristine PS fibers. This study showed an important strategy in using waste materials to produce functional nanofibers through an economical procedure. We believe that the strategy presented in this paper can be extended to other waste materials for obtaining nanofiber membranes for various environmental applications.

A Facile Fabrication of Ordered Mesoporous Carbons Derived from Phenolic Resin and Mesophase Pitch via a Self-Assembly Method.

Ordered and disordered mesoporous structures were synthesized by a self-assembly method using a mixture of phenolic resin and petroleum-based mesophase pitch as the starting materials, amphiphilic triblock copolymer F127 as a soft template, hydrochloric acid as a catalyst, and distilled water as a solvent. Then, mesoporous carbons were obtained via autoclave method at low temperature (60 °C) and then carbonization at a relatively low temperature (600 °C), respectively. X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) analyses revealed that the porous carbons with a mesophase pitch content of approximately 10 wt% showed a highly ordered hexagonal mesostructure with a highly uniform pore size of ca. 5.0 nm. In addition, the mesoporous carbons prepared by self-assembly and low-temperature autoclave methods exhibited the amorphous or crystalline carbon structures with higher specific surface area (SSA) of 756 m2/s and pore volume of 0.63 cm3/g, depending on the synthesis method. As a result, mesoporous carbons having a high SSA were successfully prepared by changing the mixing ratio of mesophase pitch and phenolic resin. The electrochemical properties of as-obtained mesoporous carbon materials were investigated. Further, the OMC-meso-10 electrode delivered the maximum SC of about 241 F/g at an applied current density of 1 A/g, which was higher than those of the MC-10 (~104 F/g) and OMC-20 (~115 F/g).

Silicon Carbide Nanostructures as Potential Carbide Material for Electrochemical Supercapacitors: A Review.

Silicon carbide (SiC) is a very promising carbide material with various applications such as electrochemical supercapacitors, photocatalysis, microwave absorption, field-effect transistors, and sensors. Due to its enticing advantages of high thermal stability, outstanding chemical stability, high thermal conductivity, and excellent mechanical behavior, it is used as a potential candidate in various fields such as supercapacitors, water-splitting, photocatalysis, biomedical, sensors, and so on. This review mainly describes the various synthesis techniques of nanostructured SiC (0D, 1D, 2D, and 3D) and its properties. Thereafter, the ongoing research trends in electrochemical supercapacitor electrodes are fully excavated. Finally, the outlook of future research directions, key obstacles, and possible solutions are emphasized.

Preparation and Characterization of Carbon Fibers from Lyocell Precursors Grafted with Polyacrylamide via Electron-Beam Irradiation.

Carbon fibers, which act as reinforcements in many applications, are often obtained from polyacrylonitrile (PAN). However, their production is expensive and results in waste problems. Therefore, we focused on producing carbon fibers from lyocell, a cellulose-based material, and analyzed the effects of the process parameters on their mechanical properties and carbon yields. Lyocell was initially grafted with polyacrylamide (PAM) via electron-beam irradiation (EBI) and was subsequently stabilized and carbonized. Thermal analysis showed that PAM grafting increased the carbon yields to 20% at 1000 °C when compared to that of raw lyocell, which degraded completely at about 600 °C. Stabilization further increased this yield to 55%. The morphology of the produced carbon fibers was highly dependent on PAM concentration, with fibers obtained at concentrations ≤0.5 wt.% exhibiting clear, rigid, and round cross-sections with smooth surfaces, whereas fibers obtained from 2 and 4 wt.% showed peeling surfaces and attachment between individual fibers due to high viscosity of PAM. These features affected the mechanical properties of the fibers. In this study, carbon fibers of the highest tensile strength (1.39 GPa) were produced with 0.5 wt.% PAM, thereby establishing the feasibility of using EBI-induced PAM grafting on lyocell fabrics to produce high-performance carbon fibers with good yields.

Synthesis and Characterization of ZnO-TiO2/Carbon Fiber Composite with Enhanced Photocatalytic Properties.

Herein, we prepared a novel photocatalytic ZnO-TiO2 loaded carbon nanofibers composites (ZnO-TiO2-CNFs) via electrospinning technique followed by a hydrothermal process. At first, the electrospun TiO2 NP-embedded carbon nanofibers (TiO2-CNFs) were achieved using electrospinning and a carbonization process. Next, the ZnO particles were grown into the TiO2-CNFs via hydrothermal treatment. The morphology, structure, and chemical compositions were studied using state-of-the-art techniques. The photocatalytic performance of the ZnO-TiO2-CNFs composite was studied using degrading methylene blue (MB) under UV-light irradiation for three successive cycles. It was noticed that the ZnO-TiO2-CNFs nanocomposite showed better MB removal properties than that of other formulations, which might be due to the synergistic effects of carbon nanofibers and utilized metal oxides (ZnO and TiO2). The adsorption characteristic of carbon fibers and matched band potentials of ZnO and TiO2 combinedly help to boost the overall photocatalytic performance of the ZnO-TiO2-CNFs composite. The obtained results from this study indicated that it can be an economical and environmentally friendly photocatalyst.

Relationship Between Functionalized Multi-Walled Carbon Nanotubes and Damping Properties of Multi-Walled Carbon Nanotubes/Carbon Fiber-Reinforced Plastic Composites for Shaft.

The mechanical properties and damping behavior of carbon fiber-reinforced plastic composites with functionalized multi-walled carbon nanotubes were examined. The functionalized multi-walled carbon nanotubes were blended with epoxy resins to prepare multi-walled carbon nanotubes/carbon fiber-reinforced plastic composites. The dispersion properties of functionalized multi-walled carbon nanotubes in epoxy resins were examined using surface free energy. The mechanical properties of functionalized multi-walled carbon nanotubes/carbon fiber-reinforced plastic composites were measured by interlaminar shear strength and torsion strength. The functionalized multi-walled carbon nanotubes/carbon fiber-reinforced plastic composites had superior mechanical properties due to the increase in dispersion properties of functionalized multi-walled carbon nanotubes in epoxy resins. However, the tan delta values of damping behavior, analyzed by dynamic mechanical analysis, varied with the type of functional groups of functionalized multi-walled carbon nanotubes. The composites obtained from functionalized multi-walled carbon nanotubes obtained through spermidine amidation reaction and carbon fiber-reinforced plastic showed excellent tan delta values due to the flexible segments in side chains.

Enhanced Antibacterial Property of Sulfate-Doped Ag3PO4 Nanoparticles Supported on PAN Electrospun Nanofibers.

Heterojunction nanofibers of PAN decorated with sulfate doped Ag3PO4 nanoparticles (SO42--Ag3PO4/PAN electrospun nanofibers) were successfully fabricated by combining simple and versatile electrospinning technique with ion exchange reaction. The novel material possessing good flexibility could exhibit superior antibacterial property over sulfate undoped species (Ag3PO4/PAN electrospun nanofibers). FESEM, XRD, FTIR, XPS and DRS were applied to characterize the morphology, phase structure, bonding configuration, elemental composition, and optical properties of the as fabricated samples. FESEM characterization confirmed the successful incorporation of SO42--Ag3PO4 nanoparticles on PAN electrospun nanofibers. The doping of SO42- ions into Ag3PO4 crystal lattice by replacing PO43- ions can provide sufficient electron-hole separation capability to the SO42--Ag3PO4/PAN heterojunction to generate reactive oxygen species (ROS) under visible light irradiation and enhances its antibacterial performance. Finally, we hope this work may offer a new paradigm to design and fabricate other types of flexible self-supporting negative-ions-doped heterojunction nanofibers using electrospinning technique for bactericidal applications.

Carbon nanofibers wrapped with zinc oxide nano-flakes as promising electrode material for supercapacitors.

A combination of electrospinning technique and hydrothermal process was carried out to fabricate zinc oxide nano-flakes wrapped carbon nanofibers (ZnO/CNFs) composite as an effective electrode material for supercapacitor. The morphology of the as-synthesized composite clearly revealed that the carbon nanofibers were successfully wrapped with ZnO nano-flakes. The electrochemical performance of the as-synthesized nanocomposite electrode was evaluated by the cyclic voltammetry (CV), galvanostatic charge-discharge (GDC), and electrochemical impedance spectroscopy (EIS), and compared with the pristine ZnO nanofibers. It was found that the composite exhibited a higher specific capacitance (260 F/g) as compared to pristine ZnO NFs (118 F/g) at the scan rate of 5 mV/s. Furthermore, the ZnO/CNFs composite also exhibited good capacity retention (73.33%). The obtained results indicated great potential applications of ZnO/CNFs composite in developing energy storage devices with high energy and power densities. The present work might provide a new route for utilizing ZnO based composites for energy storage applications.

Electrochemical characterization of a carbon nanofiber electrode system hybridized with PEDOT-PSS.

In this work, electrochemical properties of a bilayer electrode system prepared from an electrically conducting polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), PEDOT-PSS coated carbon nanofibers (CNFs), have been investigated. The CNFs were used as supports for the deposition of PEDOT-PSS by a dip-coating technique to yield a bilayer electrode system. Electrodes prepared by such a method were used in supercapacitors operating in acidic (1 M H2SO4) electrolytes. The capacitance values were estimated by voltammetry and galvanostatic techniques with a three-electrode cell configuration. Due to the CNF's graphitic structure and the presence of exterior walls with numerous edges, a high specific surface area and easily accessible electrode/electrolyte interface were obtained, thus yielding good capacitance in the bilayer active materials. The capacitance for PEDOT-PSS coated CNF bilayer electrodes ranged from 80 to 180 F/g and the fabricated materials showed good cycling performance with high stability in aqueous electrolytes. This was probably due to enhanced access to the CNFs, leading to the generation of a double layer and, ultimately, higher values of the capacitance.