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The CNC/PAN composite nanofiber film with high porosity and pure water permeability was prepared by simple electrospinning technology, using concentrated sulfuric acid hydrolyzed skim cotton with high mechanical strength and crystallinity as the reinforcing phase, and combining with polyacrylonitrile (PAN) with good thermal stability and chemical stability. The effect of CNC addition on the properties of the film was investigated through various characterizations, and the results showed that compared with pure PAN, the CNC/PAN composite nanofiber film had good thermal stability, better mechanical properties and hydrophilicity. The changes of thickness, porosity and permeation flux of pure water before and after the use of the film were explored, the oil-water separation performance of the film was analyzed, and its application in the field of water treatment was expanded. [ABSTRACT FROM AUTHOR]

The main objective of the work was to create a layer of carbon nanofibre on the surface of the NiTi shape memory alloy. The coating process was carried out in three stages. First, polyacrylonitrile was deposited by electrospinning. Then it was stabilized at temperatures up to 250°C. The last stage was the carbonization performed below 1000°C. The microstructure of the obtained coatings was observed using a scanning electron microscope. The X-ray diffraction techniques were applied to analyze the coating structure. After the polyacrylonitrile deposition, the fibers had an average diameter of about 280 nm, and the final fibers were almost twice as tiny. The applied steps also changed the phase and crystalline state of the fibers, finally leading to the formation of amorphous-nanocrystalline graphite. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to prepare a spherical modifier-modified activated carbon fiber of high specific capacitance intended for electrode materials of supercapacitor. Design/methodology/approach: In this study, phenolic-based microspheres are taken as modifiers to prepare PAN-based fiber composites by electrospinning, pre-oxidation and carbonization. Pearl-chain structures appear in RFC/ACF composites, and pure polyacrylonitrile fibers show a dense network. The shape and cross-linking degree are large. After the addition of the phenolic-based microspheres, the composite material exhibits a layered pearlite chain structure with a large porosity, and the RFC/ACF composite material is derived because of the existence of a large number of bead chain structures in the composite material. The density increases, the volume declines and the mass after being assembled into a supercapacitor as a positive electrode material decreases. The specific surface area of RFC/ACF composites is increased as compared to pure fibers. The increase in specific surface area could facilitate the diffusion of electrolyte ions in the material. Owing to the large number of bead chains, plenty of pore channels are provided for the diffusion of electrolyte ions, which is conducive to enhancing the electrochemical performance of the composite and improving the RFC/ACF composite and the specific capacitance of the material. The methods of electrochemical testing on symmetric supercapacitors (as positive electrodes) are three-electrode cyclic voltammetry, alternating current impedance and cycle stability. Findings: The specific capacitance value of the composite material was found to be 389.2 F/g, and the specific capacitance of the electrode operating at a higher current density of 20 mA/cm2 was 11.87 F/g (the amount of the microsphere modifier added was 0.3 g). Using this material as a positive electrode to assemble into asymmetrical supercapacitor, after 2,000 cycles, the specific capacitance retention rate was 87.46 per cent, indicating excellent cycle stability performance. This result can be attributed to the fact that the modifier embedded in the fiber changes the porosity between the fibers, while improving the utilization of the carbon fibers and making it easier for electrolyte ions to enter the interior of the composites, thereby increasing the capacitance of the composites. Originality/value: The modified PAN-based activated carbon fibers in the study had high specific surface area and significantly high specific capacitance, which makes it applicable as an efficient and environment-friendly absorbent, as well as an advanced electrode material for supercapacitor. [ABSTRACT FROM AUTHOR]

This paper reports the molecular organization and mechanical properties of electrospun, post-drawn polyacrylonitrile (PAN) nanofibers. Without post-drawing, the polymer chain was kinked and oriented in hexagonal crystalline structures. Immediate post-drawing in the semi-solid state disrupted the crystal structures and chain kink at maximum draw ratio. Structural re-orientation at maximum draw resulted in a 500% increase in Young's modulus and a 100% increase in ultimate tensile strength. By applying post-drawing to electrospinning it may be possible to obtain PAN fibers and PAN-derived carbon fibers with enhanced mechanical properties compared to available fabrication technologies. [ABSTRACT FROM AUTHOR]

In this study, novel polyacrylonitrile (PAN) nanofiber adsorbent modified with 6-amino-1-hexanethiol hydrochloride (Ahh) was synthesized by electrospinning method and evaluated as an adsorbent for removing thorium (IV) (Th4+) ion from aqueous solution. The PAN/Ahh was characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET). Response surface methodology (RSM) was utilized in the optimization of Th4+ adsorption in terms of (i.e., initial Ahh concentration, pH, the initial metal ion concentration, and contact time). To ensure the validity of the model, the statistical measures were investigated, thus to specify that the developed model is proper. In addition, the adsorption kinetics was well defined by the pseudo-second-order equation, while the Langmuir model better fit the adsorption isotherms. The adsorption capacity of PAN/Ahh was 499 mg Th4+ g–1 composite, leads to 98.5% removal at 25°C. Moreover, thermodynamic parameters were determined which point out the natural and endothermic nature of the reactions. The loaded Th4+ can be easily regenerated with HNO³/HCl and the PAN/Ahh could be used repeatedly without any significant reduction in its adsorption capacity. The desorption level of Th4+ from the PAN/Ahh was more than 94%. [ABSTRACT FROM AUTHOR]

Airborne dust particles has become an ever-increasing environmental concern and is also a threat to public health, leading the way in the development of fibrous materials with fascinating features like high filtration efficiency and low pressure drop. To enhance the filtration efficiency of fibrous material, particularly for submicron-sized particles, here we report a promising and versatile electret polyacrylonitrile-silicon dioxide (PAN-SiO2) fibrous membrane, considering the higher particle capture efficiency for an electret filter compared to a conventional fibrous filter. The chemical bond nonwoven and spun bond nonwoven substrates were used as support material to enhance the mechanical property and also the handling property of the as developed electrospun nanofibrous membrane. In this research work, SiO2 is identified as the potential material for developing electret filter due to its dipolar nature. The concentrations of SiO2 nanoparticles (NPs) were varied to achieve better filtration efficiency. The morphology of fibrous membrane, its air permeability, areal density and thickness properties were analyzed as per standard test methods. The filter fabrics were developed and its filtration performance and pressure drop were also characterized. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) particles were immobilized on electrospun polyacrylonitrile (PAN) nanofibers (NFs) to form PAN@PANI NFs via in situ polymerization at room temperature. Then, ZnO was deposited on the surface of PAN@PANI NFs by atomic layer deposition (ALD) to form PAN@PANI@ZnO NFs. The PANI and ZnO contents were well controlled by adjusting the polymerization time and the number of ALD cycles, respectively. The obtained PAN@PANI@ZnO NFs exhibited higher photocatalytic activity for the degradation of methylene blue under ultraviolet light irradiation than PAN@PANI and PAN@ZnO NFs, and the first-order degradation rate constant ( k app ) of PAN@PANI@ZnO NFs formed with 400 ALD cycles was greater than that of PAN@ZnO NFs formed with 400 ALD cycles by a factor of 2.1. The enhanced photocatalytic activity is shown to originate from the improved charge separation of photogenerated electrons and holes due to the formation of ZnO/PANI heterojunctions in PAN@PANI@ZnO NFs. The obtained PAN@PANI@ZnO photocatalysts are easily recycled with little decrease in photocatalytic activity because of their macroscopic mat structure and flexibility. [ABSTRACT FROM AUTHOR]

Various reaction mechanisms such as cyclization, oxidation, dehydrogenation, and crosslinking are studied during stabilization of electrospun polyacrylonitrile nanofibers using different in situ techniques such as differential scanning calorimetry (DSC), shrinkage measurement, and dynamic mechanical analysis (DMA). DSC results show that oxidation preferentially occurs in cyclized structure. It is also found that the cyclization reaction has the highest activation energy followed by oxidation/dehydrogenation and crosslinking reactions. In situ shrinkage measurement and DMA data are used to study the extent of cyclization and cross‐linking reactions, respectively, in air. Comparing the in situ shrinkage measurement with DSC data, it is found that cyclization reaction in air progresses in two different mechanisms such as radical cyclization, which depends only on the temperature and ionic cyclization, which is limited by the rate of oxygen diffusion. It is found that complete cyclization time occurs at about 189 min for isothermal heat treatment at 260°C with 5°C/min ramp, while cross‐linking reaction becomes dominant at 132 min. POLYM. ENG. SCI., 58:1315–1321, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

ABSTRACT: Needleless electrospinning technology was an effective processing method which can fabricate large scale nanofibers. We first developed a novel double rings slit spinneret to overcome the shortcomings of current needleless electrospinning spinnerets. The solution of the flow rate was controlled accurately by peristaltic control pump. Response surface methodology was adopted to investigate the influence of the processing parameters on the morphology and diameter of nanofibers. The main spinning processing parameters comprised solution concentration, applied voltage, collection distance and solution flow rate. The analysis of variance was used to evaluate response surface reduced quadratic model for nanofiber diameter. The linear and quadratic coefficients were obtained. The morphology of nanofibers was observed by scanning electron microscopy. Effects of different processing parameters on the nanofiber mean diameter have been discussed. Predicated values have a good agreement with actual values for nanofiber diameter. Actual nanofiber diameter ranges from129.15 to 404.70 nm with different process parameters. Mechanical properties of nanofiber membrane have been investigated. High quality and high throughout nanofiber could be continuously produced. This novel needleless electrospinning spinneret has a great potential for large scale nanofibers production to promote electrospinning technology development. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46407. [ABSTRACT FROM AUTHOR]

ABSTRACT: Porous carbon materials represent prospective materials for absorbers, filters, and electronic applications. Carbon fibers with high surface areas can be produced from polyacrylonitrile and spun as thin fibers from solution. The resulting polymer fibers are first stabilized to obtain conjugated ribbons and then carbonized to graphitic structures in a second high‐temperature step in an inert atmosphere. In this study, we investigated a previously described fast laser‐heating process that delivered fibers with a higher crystallinity and surface area compared to the thermally carbonized fibers. In a subsequent KOH‐activation step, the crystalline domains were exfoliated, and the surface of the fibers became macroporous. This led to a reduced specific surface area but a higher capacitance compared to thermally carbonized nanofibers. We report the electrochemical properties of the electrochemical cells and discuss their potential applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46398. [ABSTRACT FROM AUTHOR]

This study investigated the electrochemical detection of specific nucleic acid hybridization sequences using a nanofiber-coated pencil graphite biosensor. The biosensor was developed to detect Val66Met single point mutations in the brain-derived neurotrophic factor gene, which is frequently observed in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and bipolar disorder. The oxidation signal of the most electroactive and stable DNA base, i.e., guanine, was used at approximately +1.0 V. Pencil graphite electrode (PGE) surfaces were coated with polyacrylonitrile nanofibers by electrospinning. Cyclic voltammetry was applied to the nanofiber-coated PGE to pretreat its surfaces. The application of cyclic voltammetry to the nanofiber-coated PGE surfaces before attaching the probe yielded a four fold increase in the oxidation signal for guanine compared with that using the untreated and uncoated PGE surface. The signal reductions were 70% for hybridization, 10% for non-complementary binding, and 14% for a single mismatch compared with the probe. The differences in full match, non-complementary, and mismatch binding indicated that the biosensor selectively detected the target, and that it was possible to determine hybridization in about 65 min. The detection limit was 0.19 μg/ml at a target concentration of 10 ppm. [ABSTRACT FROM AUTHOR]

Electrospinning is a simple, versatile, and cost-effective technology which generates ultrasound fibers with high surface area to volume ratio, porosity and tunable porosity. Solution and processing parameters such as viscosity, molecular weight, concentration of the polymer, applied voltage, distance from tip to collector, conductivity, significantly affect the fiber morphology. An optimization of these parameters is required to obtain materials with desired properties for specific applications. In this study we synthesized electrospun fibers with different concentrations of PAN, our purpose being the obtaining of carbon fibers, needed for producing the gas diffusion layers for Proton Exchange Membrane Fuel Cell. The electrospun fibers obtained were subjected to carbonization at two different temperatures, 1200°C and 1400°C, in order to establish the temperature influence on removing all non-carbonaceous matter and to obtain a sample with higher carbon concentration and pure carbonaceous material. [ABSTRACT FROM AUTHOR]

This study investigates the microstructure and mechanical properties of electrospun nanofibers from polyacrylonitrile (PAN)‐dimethylformamide (DMF) solution at different relative humidity (RH) in the range from 14% to 60% and two different temperatures (20°C and 40°C). Nanofibers produced at low RH (22% or less at 20°C) exhibit relatively smooth surface and solid core, whereas at higher RH (30% or higher at 20°C) rough surface and porous core are observed. The resulting morphology is explained by means of H2O/DMF/PAN ternary phase diagram. At higher RH, the water diffusion into polymer‐solution jet brings thermodynamic instability into the system leading to separation of polymer‐rich phase and polymer‐lean phase, where the later contributes to porosity. Higher process temperature (40°C) yields larger miscibility area in the ternary phase diagram leading to formation of porous structure at relatively higher RH (40%). Tensile strength of nanofibrous yarns is found to vary from 80 MPa to 130 MPa depending on the processing temperature and RH. The amount of porosity is found to affect the tensile properties of nanofibers most significantly, although diameter and crystallinity play important role. Annealing is found to alleviate surface roughness and porosity and increase crystallinity. Tensile strength of nanofibrous yarns is found to improve by up to 25% after annealing. POLYM. ENG. SCI., 58:998–1009, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Polyacrylonitrile/graphene (PAN/GP) composite nanofiber filaments were spun continuously by a homemade eight‐needle electrospinning device with an auxiliary electrode, and then, yarns were obtained by plying and successive twisting. Subsequently, the composite yarns were stabilized at 250–280°C for 1–2 h and then carbonized at 800–1100°C for 1–3 h. The diameter of yarns significantly decreased by over 60% after carbonization and the structure became more compact. The optimum stabilization conditions were at 270°C with holding for 1.5 h. The addition of GP at a low mass fraction (<1%) promoted the formation of ladder‐like structures and ordered graphitic structures during stabilization and carbonization. It seems there were defects in the pristine CNF, and the addition of GP reduced the defects. The conductivity of the composite CNF yarn sharply increased with the increase of GP content to 1%, and then decreased. The maximum value was 66.44 ± 13.16 S/cm at 1100°C held for 3 h. The mechanical properties for composite CNF yarns were performed. The maximum stress and modulus were 59.49 MPa and 14.63 GPa, respectively. POLYM. ENG. SCI., 58:903–912, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In this study, a novel resonance light scattering (RLS) sensor was synthesized using polyacrylonitrile nanofibers decorated with magnetic carbon dots (MCDs@NFs) nanocomposite and applied for famotidine (FMD) determination. The MCDs@NFs nanocomposite was synthesized by combining electrospinning and a simple one-step hydrothermal method. Different methods were applied in order to characterize the MCDs@NFs nanocomposite such as: scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Light scattering properties of the synthesized nanocomposite in the presence or absence of FMD have been selected as the detection signal considering the fact that FMD addition increases the RLS intensities of the system. Thus, the prepared nanocomposite was employed as a RLS sensor to detect FMD. A linear response was observed under the optimal conditions in range of 0.15–50.0 μmol L −1 with detection limit of 0.04 μmol L −1 . The MCDs@NFs nanocomposite was effectively capable in determining FMD in real samples and the results were close to those results obtained by reversed-phase HPLC method (RP-HPLC). [ABSTRACT FROM AUTHOR]

In this paper, the cellulose/polyacrylonitrile(PAN) composite nanofibers were prepared via electrospinning technique firstly. Then, cellulose/PAN/Cu nanofibers were fabricated with antibacterial function by loading Cu(II) ions. The morphology, mechanical properties and hydrophilicity of nanofibers was characterized. Antibacterial performance of cellulose/PAN/Cu nanofiber with against Staphylococcus aureus and Escherichia coli were evaluated. The results showed that the cellulose/PAN/Cu nanofiber demonstrated excellent mechanical property and antibacterial activity when the concentration of Cu(II) ions is set to be 0.01 mol/L. [ABSTRACT FROM AUTHOR]

ABSTRACT Varying amounts of exfoliated graphene oxide (GO) are systematically incorporated into nanoscale polyacrylonitrile (PAN) fibers via an electrospinning method. Subsequent treatment of the PAN-GO composite nanofibers under a moderate temperature and high pressure leads to the formation of membrane sheets with enhanced mechanical properties. scanning electron microscope, Fourier transform infrared spectroscopy, and contact angle measurements confirm the successful incorporation of the GO into the PAN nanofiber membranes whose diameter, porosity, and pore size are notably influenced by the amount of the GO content. These composite membranes also exhibit a gradual reduction in the water contact angle as a function of the hydrophilic GO content, resulting in a beneficial property for water purification. In addition, the proper integration of GO into the PAN nanofibers improves the protein rejection rate and water flux during the filtration process, which indicates the possibility of utilizing these types of composite membranes in water treatment systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45858. [ABSTRACT FROM AUTHOR]

Silver nanoparticles-attached zinc oxide (ZnO) nanorods on polyacrylonitrile/indium tin oxide (Ag-ZnO-PAN/ITO) nanofibres with three-dimensional (3D) hierarchical nanostructures were facilely prepared via electrospinning followed by hydrothermal synthesis of ZnO nanorods and silver attachment with the assistance of polydopamine (PDA) thin layer. ZnO nanorods with different dimensions and silver nanoparticles with different loadings were introduced. The morphologies and structures of the nanostructures were studied by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and thermogravimetric analyzer (TGA). The effect of Ag-ZnO-PAN/ITO nanofibres with different loadings of ZnO nanorods and silver nanoparticles on their antibacterial activity against Escherichia coli and Pseudomonas aeruginosa was investigated. It is shown that the hybrid nanofibres exhibit excellent antibacterial capability. The hierarchical structure benefits the attachment of a large amount of silver nanoparticles due to its large surface area, and the deposited PDA thin layer helps improve the structure stability for long-term antibacterial application through firmly anchoring silver nanoparticles onto the surface. This work offers an effective and straightforward “all-solution” strategy to incorporate Ag-ZnO combination into nanofibrous PAN. Moreover, the hierarchical nanostructure integrates the antibacterial function of both ZnO and silver, and renders itself a promising candidate as for sportswear and equipment. [ABSTRACT FROM AUTHOR]

In this work, polymer nanofibers (PAN/n-OMMT clay) were successfully produced by using an electrospinning process. The PAN/n-OMMT nanofibers were studied as an oil and solvent absorbent material due to their super hydrophobicity and super oleophilic properties. The generated composite nanofibers were found to have a very high oil and solvent absorption capacity in the case of 3% n-OMMT clay loading. It showed excellent absorption capacity up to 160 times its own weight for motor oil. The findings reported in this work might provide a fast and facile approach for the removal of oils and organic solvents on water surfaces. [ABSTRACT FROM AUTHOR]

ABSTRACT Amidoxime-modified polyacrylonitrile nanofibrous films (AOPAN NFs) were prepared via an electrospinning technique. The traditional preparation methods for amidoximated polyacrylonitrile (AOPAN) solution were changed and improved. First, the PAN solution was modified by hydroxylamine hydrochloride to produce an AOPAN solution, and then, a small amount of inhibitor was added to the AOPAN solution for electrospinning. We found that the crosslinking of the AOPAN solution was inhibited by the addition of a small amount of inhibitor; at the same time, the storage time of the AOPAN solution was prolonged. In addition, the prepared AOPAN solution was electrospun into nanofibrous films, which could be used as excellent adsorption materials for Cu(II), Pb(II), and methyl orange (MO) after drying. The maximal adsorption capacities for Cu(II), Pb(II), and MO were 143.47, 178.57, and 68.07 mg/g, respectively. The adsorption capacities of the nanofibrous films were more than 50% that of the first adsorption after four recycling runs; this indicated the reusability of the nanofibrous films for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45697. [ABSTRACT FROM AUTHOR]

We herein report a fascinating carbon aerogel that has a unique framework structure consisting of one-dimensional (i.e. nanofibers) and two-dimensional (i.e. graphene) carbon nanomaterials. Such a carbon aerogel was prepared by carbonization of electrospun polyacrylonitrile with graphene oxide sheets (GO). The nanofiber-graphene interconnection within the aerogel considerably enhances the electrochemical characteristics. The aerogel showed an electrosorption capacity of 15.7 mg g −1 in 500 mg L −1 NaCl solution, and the CDI cell exhibited stable performance over 100 cycles. Moreover, the carbon aerogel has good electrical conductivity and faster electron transfer rate. Such a cross-linked porous aerogel may provide a new strategy for highly efficient CDI applications. [ABSTRACT FROM AUTHOR]

A modified bubble electrospinning by placing a positively charged ring between the bubble and the parallel electrode collector was presented to fabricate highly aligned nanofibers. The theoretical and experimental analyses were carried out to study formation mechanism of highly aligned nanofibers using the modified bubble electrospinning. The results showed the modified bubble electrospinning could decrease the nanofiber diameter, enhance the diameter distribution, and improve the nanofiber alignment. [ABSTRACT FROM AUTHOR]

Metal-organic framework (MOF) nanocrystalline materials have received great attention because of their application in heterogeneous catalysis. However, they suffer from poor separation from reaction mixtures in practical applications. In this study, we report the first cobalt metal-organic framework containing zeolitic imidazolate framework (ZIF)-67 nanoparticles immobilized on electrospun polyacrylonitrile (PAN) nanofibers, which was used as a composite catalyst (ZIF-67/PAN) for activating peroxymonosulfate (PMS). Detailed characterization showed that the ZIF-67/PAN nanofibers possessed a flexible one-dimensional structure. To demonstrate the catalytic performance of the ZIF-67/PAN nanofibers, the activation of PMS for the catalytic degradation of acid yellow-17 (AY) was chosen as the model catalytic reaction. The results show that 95.1% of AY (500 mg L −1 ) was removed by ZIF-67/PAN in 10 min, which is much higher than many other PMS catalyst. More interestingly, the flexible ZIF-67/PAN composite nanofibers catalysts were not only easy to separate from solution but they also retained high catalytic stability. The influencing factors for PMS activation were also investigated, including the catalyst dosage, reaction temperature, solution pH, and doping with competing organic molecules. The degradation mechanism was elucidated by electron paramagnetic resonance experiments. This work provides a new sight into the fabrication of high-performance MOF catalysts with outstanding recycling properties, which may promote the use of MOF materials in more practical applications. [ABSTRACT FROM AUTHOR]

Hierarchically structured, nanoparticle-on-nanofiber composite membranes were successfully prepared by electrospray of titanium dioxide (TiO 2 ) suspensions and electrospinning of polyacrylonitrile (PAN) solution simultaneously. The results showed that the TiO 2 nanoparticles were highly dispersed on the surface of PAN nanofibers to construct hierarchical nanostructures, which could not only endow the composite membrane with high photocatalytic activity but also further improve the filter efficiency of the composite membrane. Furthermore, the photocatalytic activities and filter efficiencies of composite membranes could be further tuned by controlling the TiO 2 /PAN mass ratios. Our study indicated that the combination of TiO 2 nanoparticles and PAN nanofibers via simultaneous electrospinning-spray offers a new strategy to construct advanced multifunctional TiO 2 /PAN membranes with hierarchical nanostructures, which could not only perform well in decomposing toluene but also remove particulate matter in air effectively. [ABSTRACT FROM AUTHOR]

ABSTRACT A systematic study using design of experiments was applied in order to map out the thermal stabilization of electrospun polyacrylonitrile mats and to investigate how oxidation and cyclization reactions are affected by rate, temperature, and time in an oxidative environment. Cyclization indexes were estimated by a simple methodology based on differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy data. Values of enthalpy and relative intensities of bands assigned to CN and CN bonds were used on calculation. The statistical planning applied in this study was important to show that not always longest treatment is effective to stabilize polyacrylonitrile, but also samples obtained in less than 3 h presented low values of exothermic peak on DSC, values of cyclization indexes near to 90%, both from DSC and Fourier transform infrared spectroscopy techniques, reduced weight loss in thermogravimetric analysis and O/C ratio higher than 10% by X-ray photoelectron spectroscopy, that are appreciated characteristics to a precursor of high-performance carbon materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45458. [ABSTRACT FROM AUTHOR]

ABSTRACT Continuous carbon nanofibers had been widely studied based on different processing methods and precursors. Especially, electrospinning was introduced as a versatile method for fabricating ultrathin fibers. However, as the limitation of precursor, pitch had not been well studied due to its viscosity and miscibility problem. A comprehensive study on the electrospinning of the blends [pitch and polyacrylonitrile (PAN)] was explored. Thermodynamic miscibility was studied by using differential scanning calorimeter. Fourier transfer infrared spectroscopy was used to show interaction and potential reaction between pitch and PAN molecules. Finally, smooth, continuous, and cylindrical carbon nanofibers were successfully fabricated by electrospinning technique. Based on Raman analysis result, the addition of pitch enhanced the carbon crystallite which improved the overall electrical conductivity and modulus of nanofibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45388. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) nanomaterials have gained attention in energy conversion, storage, and catalyst due to the unique physical and chemical properties. Electrospinning is a kind of simple, versatile, and cost-effective technology to fabricate 1D functional nanofibers. Herein, electrospun polyacrylonitrile (PAN), melamine, and ferric chloride hexahydrate (FeCl 3 ·6H 2 O) composite nanofibers are used as template, and polythiophene (PT) are prepared by photopolymerization technology on the surface of electrospun nanofibers as shell part of fibers. Then, the core–shell nanofibers are pyrolyzed and converted into Fe–S/N–C nanofibers, which can be used as catalysts for ORR due to the metal and S-/N-codoped structure and unique 1D structure which provided facile pathways for efficient mass transport and charge transfer. The ORR electrocatalytic ability of Fe–S/N–C nanofibers is tested and present excellent property, especially in stability and methanol crossover. The electrocatalytic ability of sample is comparable to that of 20 wt% Pt/C benchmarks. These results offer an easy pathway for exploring metal-heteroatom-codoped carbon nanofibers applicable for ORR catalyst. [ABSTRACT FROM AUTHOR]

A novel polyacrylonitrile (PAN) nanofibrous membrane conjugated with platinum nanoparticles (PtNPs) was fabricated by electrospinning and electrostatic assembly techniques. In this procedure, PAN was electrospun with 3-aminopropyltriethoxysilane (APS) together as precursor materials. First, amine groups were introduced onto PAN nanofibers, and then the as-prepared negative-charged platinum nanoparticles (PtNPs) were conjugated onto the surface of the amino-modified PAN nanofibers uniformly by the electrostatic interaction-mediated assembly. The fabricated PAN-PtNPs hybrid nanofibrous membrane was further utilized to modify the glassy carbon electrodes and was used for the fabrication of a non-enzymatic amperometric sensor to detect hydrogen peroxide (H2O2). The electrochemical results indicated that, due to the uniform dispersion of PtNPs and the electrostatic interaction between amine groups and PtNPs, the fabricated PAN-PtNPs nanofibrous membrane-based electrochemical sensor showed excellent electrocatalytic activity toward H2O2, and the chronoamperometry measurements illustrated that the fabricated sensor had a high sensitivity for detecting H2O2. It is anticipated that the strategies used in this work will not only guide the design and fabrication of functional polymeric nanofiber-based biomaterials and nanodevices, but also extend their potential applications in energy storage, cytology, and tissue engineering. [ABSTRACT FROM AUTHOR]

Electrospinning is a new type of free-end spinning built on the electric field. The electric force of polyacrylonitrile (PAN) polymer solution overcomes the surface tension of the solution, and then it causes wave and forms jet flow. In the process of injection, the solution is evaporated or solidified, eventually forming a fiber on the receiving device. Different from ordinary single needle head, in the study, a new type of 3D free surface spinneret is used to produce multiple jets at the same time, and this will greatly improve production efficiency. In the paper, the model of 3D free surface is analyzed by the theory of fluid mechanics. The relationship among the wave length, surface tension and the electric field is obtained. After the mechanical analysis on the stable period of the jet, the relationship between the jet radius and the distance from the spinneret to jet is carried out. At the same time the relationship between the jet velocity and the tensile force is carried out. After mechanics analyzing on the unstable period of the jet, it can be concluded that the radius of the jet is inversely proportional to one half power of the distance from the jet to the spinneret, and the electrostatic spinning jet's velocity is directly proportional to one half power of the tensile force. After the mechanical analysis of the unstable period of the electrospinning jet, it can be concluded that the radius of the jet is inversely proportional to one fourth power of the jet intercept point distance. [ABSTRACT FROM AUTHOR]

In this study, composite nanofibers from a solution of polyacrylonitrile (PAN), functionalized multi-walled carbon nanotubes (f-MWCNTs), and silver nitrate (AgNO3) in dimethylsulfoxide were successfully produced by the electrospinning method. Aqueous solution of hydrazinium hydroxide was used for the chemical reduction of silver ions. The effects of the simultaneous use of carbon nanotubes (either pristine or amine-functionalized) and silver nitrate in different percentages and the application of chemical reduction on the properties of the nanocomposite nanowebs were investigated. FTIR, SEM, conductivity meter, tensile tester, XRD, and DSC were used for the characterization. Antibacterial activities of the nanocomposite nanowebs were determined against S. Aureus. Full factorial experimental design was utilized in order to be able to evaluate the contributions of the selected factors (f-MWCNT content, AgNO3 content, and application of reduction process) to the variations in ultimate tensile strength, elongation, and conductivity of the composite nanowebs. Analysis of variance (ANOVA) and multiple comparisons were carried out to evaluate the average nanofiber diameters and mechanical properties. PAN/f-MWCNTs/AgNPs nanowebs displayed enhanced conductivity and antimicrobial properties particularly when the chemical reduction process was applied. Besides they showed improved crystallinity compared with pure PAN nanofibers. While the reduction process made the highest contribution to the ultimate tensile strength, elongation, and conductivity of the nanowebs, f-MWCNT content had negligible effect on conductivity of the nanowebs. Considering all the results obtained in this study, composite nanofiber webs of PAN with 1 w% f-MWCNTs and 1 w%AgNO3 can be suggested for use as antistatic and antibacterial filaments. [ABSTRACT FROM AUTHOR]

In order to enhance hydrogen storage capacity of carbonaceous materials through metal modification, FeNiCr-carbon composites were prepared by calcination of Fe, Ni and Cr-containing polyacrylonitrile (PAN) fibers fabricated by electrospinning method. Fe (III), Ni (II) and Cr (III) acetylacetonates (M (acac) n ) were selected as metal sources. Increase of specific surface area and formation of micropores were observed on heat decomposition of M (acac) n particularly through introduction of steam. Maximal hydrogen content, 1.62 mass%, was obtained at 77 K under 0.8 MPa of hydrogen for a FeNiCr-carbon composite, which contained about 15.5 mass% of metals and had specific surface area of 501 m 2 g −1 . The hydrogen content exceeded the hydrogen physisorption limit, 2.34 mass% per 1000 m 2 g −1 , which was calculated on the basis of the commensurate–incommensurate transition with an enhancing factor ρ of 1.126. After hydrogenation at 653 K, no hydrogen desorption peaks were observed for FeNiCr powders derived from M (acac) n , and one peak at 828 K for a carbonaceous sample prepared from unmodified PAN fibers. From the most promising FeNiCr-carbon composite, another peak was recorded at 752 K in addition to the peak at 828 K. The former would be originated from hydrogen on novel sorption sites additionally created on the composite formation. [ABSTRACT FROM AUTHOR]

Humic acid is creatively selected as an anode material in sodium ion batteries. Bio-based carbon fibers (H-CF) are fabricated from polyacrylonitrile (PAN) − humic acid (HA) via simple eletrospinning followed by stabilization and carbonization. The heat-treatment temperature (HTT) is optimized based on analysis of material structures and electrochemical performances. Due to unique composite networks and oxygenic functionalities, the H-CF anode obtained at 1300 °C has a large reversible capacity of 261.3 mAh g −1 (current density: 0.02 A g −1 , initial efficiency: 69.6%). The anode also presents good cycle stability (249.6 mAh g −1 reversible capacity at 0.1 A g −1 with capacity retention of 92.8% over 100 cycles) and good rate capability (208.6 mAh g −1 at 0.2 A g −1 and 81.7 mAh g −1 at 1 A g −1 ). It is proved that humic acid can serve as a robust precursor for high-performance anode of sodium ion batteries. [ABSTRACT FROM AUTHOR]

Conventional electrochemical capacitors are usually made from activated carbon microfiber electrode, which has relatively low electrochemical capacitance. To improve performance of electrochemical capacitor, carbon nanotube (CNT) was used to incorporate in carbon microfiber. Firstly, CNT was coated with ultra-thin polyacrylonitrile (PAN) film coating using the admicellar polymerization technique to improve its dispersion in PAN matrix. Secondly, the mix solution of admicellar-modified CNT (Ad-CNT) and PAN in N,N -dimethylformamide (DMF) was prepared to produce microfiber by electrospinning. Lastly, microfiber was collected as a sheet, which was then stabilized and carbonized to be used as an electrode. The fabricated electrode using Ad-CNT/PAN was analyzed by SEM and TEM. SEM images show that the microfiber was uniform with approximately 2 μm average diameter. TEM images display well alignment and good dispersion of Ad-CNT in the matrix. The electrode made from Ad-CNT/PAN exhibited a high specific capacitance of 125 F g −1 at a scan rate of 3 mV s −1 (based on cyclic voltammetry) and 82 F g −1 at a specific current of 1 A g −1 (based on galvanostatic charge/discharge). The percentage of relative specific capacitance retention of the prepared electrode was 70% after 1000 cycles. The results clearly show that the Ad-CNT played an effective role in improving dispersion in electrode leading to increase in electrical conductivity as well as electrical capacitance of the capacitor. [ABSTRACT FROM AUTHOR]

In the electrospinning process, a modified parallel electrode method (MPEM), conducted by placing a positively charged ring between the needle and the parallel electrode collector, was used to fabricate highly aligned carbon nanotubes/polyacrylonitrile (CNTs/PAN) composite nanofibers. Characterizations of the samples--such as morphology, the degree of alignment, and mechanical and conductive properties--were investigated by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), universal testing machine, high-resistance meter, and other methods. The results showed the MPEM could improve the alignment and uniformity of electrospun CNTs/PAN composite nanofibers, and enhance their mechanical and conductive properties. This meant the successful preparation of highly aligned CNT-reinforced PAN nanofibers with enhanced physical properties, suggesting their potential application in appliances and communication areas. [ABSTRACT FROM AUTHOR]

Electrospun fibers of mixed polyacrylonitrile/polyvinyl pyrrolidine (PAN/PVP) sheath and silicone oil core were obtained by coaxial electrospinning. PVP and silicone oil were then removed from the coaxial electrospun fibers via phase separation and carbonization processes, respectively, to make the hollow-porous multilayered ultrafine carbon fibers. The relationship between the morphology and electrochemical performance of ultrafine carbon fibers was investigated. Results show that the supercapacitor based on electrode of hollow-porous multilayered ultrafine carbon fibers exhibits high conductivity, fast ion diffusion, high specific capacitance (231.6 F·g −1 ), high charging/discharging efficiency (99.7%), and low internal resistance (0.2 Ω) using tetraethylammonium tetrafluoroborate in acetonitrile as electrolyte. Additionally, this work also demonstrates a great potential in the preparation of carbon nano-materials with graphene-like multilayer structure. [ABSTRACT FROM AUTHOR]

In this study, a self-assembly of miniaturized pipette-tip-based solid-phase extraction for the simultaneous extraction of nitroaromatic compounds was developed, with electrospun polyacrylonitrile nanofibers used as sorbents. The electrospun polyacrylonitrile nanofibers were characterized by scanning electron microscopy, FTIR analysis and surface area analysis. Good linearities for the four nitroaromatic compounds (2,6-dinitrotoluene, 2-nitrotoluene, 3-nitrotoluene, and 4-nitrotoluene) were obtained in a range of 250-1000 μg/L with coefficients of determination > 0.99. The limits of detection of these analytes were between 21 and 38 μg/L. The results showed that the pipette-tip-based solid-phase extraction was effective in extracting nitrotoluenes in the pH regime of environmental interest (≈ 6). The investigation also revealed that the optimum mass of electrospun polyacrylonitrile nanofibers sorbent was 15 mg and 20 aspirating/dispensing cycles gave the maximum recovery of nitrotoluenes with 200 μL acetonitrile as the best eluting solvent. Moreover, the performance of the present method was studied for the extraction and determination of nitroaromatic compounds in real environmental water samples and good recoveries ranging from 70 to 115% were found, and respective relative standard deviations of <12% were obtained. [ABSTRACT FROM AUTHOR]

This paper reports the electrochemical properties of various silver-manganese oxide carbon nanofiber-based composites (AgO x -MnO x /CNF). The various polyacrylonitrile (PAN)-based solutions; PAN, AgNO 3 /PAN, Mn(NO 3 ) 2 /PAN, and AgNO 3 Mn(NO 3 ) 2 /PAN were dissolved in N , N -dimethylformamide (DMF) as the precursors. The four-nozzle electrospinning system was employed to obtain nanofibers. The electrospun precursors were calcined using a tubular quartz furnace including stabilization, carbonization, and activation under air, argon, and CO 2 atmosphere, respectively. The calcined samples were named as CNF, AgO x /CNF, MnO x /CNF, AgO x - MnO x /CNF dependent on each composite. Morphological, structural, textural properties were characterized, and supercapacitor performances were studied by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The calcined fibers were obtained as a paper-like sheet thickness of ∼30–60 μm, they had several diameters of ∼237–643 nm depending on each composite. Among the samples, the AgO x -MnO x /CNF which had a high specific surface area of 812 m 2 g −1 expressed the highest specific capacitance of nearly 204 F g −1 and energy density of ∼28 mW h g −1 at a power density of ∼250 mW g −1 . Moreover, it also displayed imposing cycling capability of more than 99% after 1000 cycles of charge/discharge. In addition, the other remarkable results have been also discussed. [ABSTRACT FROM AUTHOR]

The coal based activated carbon nanofibers (CBACFs) were prepared by electrospinning a mixture of polyacrylonitrile (PAN) and acid treated coal. Cadmium sulfide (CdS) nanoparticles loaded on CBACFs were fabricated by solvothermal method. The obtained samples were characterized by FESEM, TEM, and XRD. The results reveal that the CdS nanoparticles are homogeneously dispersed on the surfaces of CBACFs. The CdS/CBACFs nanocomposites exhibited higher photoactivity for photodegradation of methyl blue (MB) under visible light irradiation than pure CdS nanoparticles. CBACFs can be used as low cost support materials for the preparation of nanocomposites with high photocatalytic activity. [ABSTRACT FROM AUTHOR]

Within the present study, polyacrylonitrile (PAN) nanofibers were produced by electrospinning technique. The surface of the webs was then modified by three different sources of amine-containing compounds, including diethylamine, diethylenetriamine, and triethylenetetramine. Chemical, morphological, and surface properties of nanofibers were investigated by attenuated total internal reflection (ATR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The maximum grafting yield of amine groups to PAN nanofibers was calculated by the gravimetric method. The ATR results indicated that amide groups were formed on the fiber surface by a chemical reaction between the nitrile groups of PAN and the amine groups of amine-containing compounds. The SEM images showed a rough, conglutinated, and intertwined surface morphology of nanofibers induced by amine-containing materials. The AFM results showed that after the functionalization process, the surfaces of the PAN nanofiber were rougher when compared with untreated PAN nanofiber. Finally, their dye removal ability was evaluated using UV–vis spectroscopy using Direct red 80 (DR80) and Direct red 23 (DR23) as model compounds. The amounts of the dye adsorbed onto the functionalized PAN nanofibers (FPAN) were influenced by the initial pH, FPAN dosage, contact time, and the initial concentration of the dye solutions. It was found that both dyes adsorption followed the Langmuir isotherm. In addition, adsorption kinetics of both dyes was found to conform to pseudo-second-order kinetics. We finally found that the functionalized PAN nanofibers were good candidates for anionic dye adsorption from colored wastewater with high dye adsorption capacity [ABSTRACT FROM AUTHOR]

Electrospun fibrous membranes find place in diverse applications like sensors, filters, fuel cell membranes, scaffolds for tissue engineering, organic electronics etc. The objectives of present work are to electrospun polyacrylonitrile (PAN) nanofibers and PAN-CNT nanocomposite nanofibers and convert into carbon nanofiber and carbon-CNT composite nanofiber. The work was divided into two parts, development of nanofibers and composite nanofiber. The PAN nanofibers were produced from 9 wt% PAN solution by electrospinning technique. In another case PAN-CNT composite nanofibers were developed from different concentrations of MWCNTs (1-3 wt%) in 9 wt% PAN solution by electrospinning. Both types of nanofibers were undergone through oxidation, stabilization, carbonization and graphitization. At each stage of processing of carbon and carbon-CNT composite nanofibers were characterized by SEM, AFM, TGA and XRD. It was observed that diameter of nanofiber varies with processing parameters such as applied voltage tip to collector distance, flow rate of solution and polymer concentrations etc. while in case of PAN-CNT composite nanofiber diameter decreases with increasing concentration of CNT in PAN solution. Also with stabilization, carbonization and graphitization diameter of nanofiber decreases. SEM images shows that the minimum fiber diameter in case of 3 wt% of CNT solution because as viscosity increases it reduces the phase separation of PAN and solvent and as a consequence increases in the fiber diameter. AFM images shows that surface of film is irregular which give idea about mat type orientation of fibers. XRD results show that degree of graphitization increases on increasing CNT concentration because of additional stresses exerting on the nanofiber surface in the immediate vicinity of CNTs. TGA results shows wt loss decreases as CNT concentration increases in fibers. [ABSTRACT FROM AUTHOR]

The objective of this experimental study is to produce a nanofibrous membrane functionalized with adsorbent particles called metal organic framework (MOF) in order to adsorb CO from a gas source. Therefore, Polyacrylonitrile (PAN) was chosen as the precursor for nanofibers and HKUST-1, a Cu-based MOF, was chosen as adsorbent. The experimental process consists of electrospinning PAN solution blended with HKUST-1 to produce a nanofibrous mat as working substrates. The fibers were collected in a cylindrical canister model. SEM image of this mat showed nanofibers with the presence of small adsorbent particles, impregnated into the as-spun fibers discretely. To increase the amount of MOF particles for effectual gas adsorption, a secondary solvothermal process of producing MOF particles on the fibers was required. This process consists of multiple growth cycles of HKUST-1 particles by using a sol-gel precursor. SEM images showed uniform distribution of porous MOF particles of 2-4 µm in size on the fiber surface. Energy dispersive spectroscopy report of the fiber confirmed the presence of MOF particles through the identification of characteristic Copper elemental peaks of HKUST-1. To determine the thermal stability of the fibrous membrane, Thermogravimetric analysis of HKUST-1 consisting of PAN fiber was performed where a total weight loss of 40% between 210 and 360 °C was observed, hence proving the high-temperature durability of the synthesized membrane. BET surface area of the fiber membrane was measured as 540.73 m/g. The fiber membrane was then placed into an experimental test bench containing a mixed gas inflow of CO and N. Using non-dispersive infrared CO sensors connected to the inlet and outlet port of the bench, significant reduction of CO in concentration was measured. Comparative IR spectroscopic analysis between the gas-treated and gas untreated fiber samples showed the presence of characteristic peak in the vicinity of 2300 and 2400 cm which verifies the adsorption of CO. [ABSTRACT FROM AUTHOR]

One-dimensional PAN-based carbon nanofibers were prepared by electrospinning in combination with a high-temperature carbonization process. The prepared PAN-based nanofibers were characterized by a high aspect ratio. The microwave absorption property was adjusted by controlling the carbonization temperature. The carbonization temperature affected the degree of graphitization, which directly affected the dielectric loss and further improved the microwave absorption properties of PAN-based carbon nanofibers. The PAN-based carbon fibers were optimized in terms of both maximum reflection loss (RL min) and effective absorption bandwidth (EAB) after carbonization at 800 °C. The PAN-based carbon fiber/paraffin composites containing 10 wt% filler exhibited excellent absorption performance with a maximum reflection loss of − 12.75 dB and an effective absorption bandwidth of 4.88 GHz (13.12–18 GHz) at 2.2 mm, which basically covered the Ku-band (12.88–17.88 GHz). When the absorber thickness was 2.4 mm, the reflection loss at 14.4 GHz was − 11.39 dB, and the maximum effective absorption bandwidth was 5.04 GHz (11.92–16.96 GHz). PAN-based carbon nanofibers showed excellent absorption properties due to the dielectric loss in cooperation with good impedance matching. [Display omitted] [ABSTRACT FROM AUTHOR]

Aligned electrospun nanofibrous bundle was used as the raw material for pretreatment, preoxidation and carbonization processes to prepare carbon nanofibers in a procedure temperature-controlled sintering furnace. Effect of carbonization temperature on themorphology and structural performance of nanofiberswas investigated in present study. Results showed that R1 (the relative intensity radio between Disordered peak and Graphite peak) of nanofibers carbonized at 1000 °C is 0.90, carbon content is up to 85.67%, conductivity is 105.44 S·cm-1, Young's modulus is 68.8 ± 0.42 GPa, and fiber strength is 306.0 ± 9.0 MPa, all of which endow the fibers with a superior comprehensive property. [ABSTRACT FROM AUTHOR]

ABSTRACT Composite nanofiber meshes of well-aligned polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP) nanofibers containing multiwalled carbon nanotubes (MWCNTs) were successfully fabricated by a magnetic-field-assisted electrospinning (MFAES) technology, which was confirmed to be a favorable method for preparation of aligned composite nanofibers in this article. The MFAES experiments showed that the diameters of composite nanofibers decreased first and then increased with the increase of voltage and MWCNTs content. With the increase of voltage, the degree of alignment of the composite nanofibers decreased, whereas it increased with increasing MWCNTs concentration. Transmission electron microscopy observation showed that MWCNTs were parallel and oriented along the axes of the nanofibers under the low concentration. A maximum enhancement of 178% in tensile strength was manifested by adding 2 wt % MWCNTs in well-aligned composite nanofibers. In addition, the storage modulus of PAN/PVP/MWCNTs composite nanofibers was significantly higher than that of the PAN/PVP nanofibers. Besides, due to the highly ordered alignment structure, the composite nanofiber meshes showed large anisotropic surface resistance, that is, the surface resistance of the composite nanofiber films along the fiber axis was about 10 times smaller than that perpendicular to the axis direction. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41995. [ABSTRACT FROM AUTHOR]

A mechanically robust and high-capacity oil sorbent is prepared by electrospinning a blend of polystyrene (PS) and polyacrylonitrile (PAN). The morphology, oil sorption capacity and mechanical property of the fibers formed in different compositions are investigated in detail. It is shown that the oil sorption capacity is a result of both the chemical composition and the specific surface area which related to diameter size. The addition of PAN as a component in fibrous sorbents can significantly improve the mechanical properties of PS fibers. Moreover, the oil sorption capacity increases with decreasing fiber diameter. The results also show that the maximum sorption capacities of the PS/PAN sorbent for pump oil, peanut oil, diesel, and gasoline were 194.85, 131.70, 66.75, and 43.38 g g −1 , respectively. Additionally, the sorbent exhibits quick oil sorption speed as well as high buoyancy, which make it a promising candidate for use as an oil spill cleanup sorbent. [ABSTRACT FROM AUTHOR]

Novel lignin-chitosan polyelectrolyte fibres were produced through a reactive electrospinning process. Polyelectrolyte formation between the anionic lignin and cationic chitosan was controlled through the pH of the solution. Through manipulating the polyelectrolyte complex formation, fibres could be effectively produced from two biopolymers, which are normally very difficult to electrospin on their own. Though minimal amounts of the petroleum-derived polyethylene oxide were introduced into the solution to enhance the spinnability of the polyelectrolyte solution, it could be easily removed from the fibres post spinning by washing with water. Thus, pure biopolymer fibres could be produced. The optimum composition of lignin to chitosan was identified through SEM, FTIR and TGA analysis of the electrospun fibres. Fluorescence spectra of the electrospun fibres reveal the homogeneous distribution of lignin and chitosan components throughout the fibre network. [ABSTRACT FROM AUTHOR]

Abstract: A modified electrospinning setup was used to manufacture uniaxially aligned nanofiber yarns. Compared with the traditional electrospinning setup, two oppositely placed metal needles were employed and applied with positive and negative voltages respectively. Meanwhile, a neutral metal disc and hollow metal rod were placed oppositely in the middle of the two needles. Nanofibers ejected from two needles were oriented in the gap between the metal disc and the tapered sharp end of hollow metal rod. A nanofiber bundle was obtained and twisted by rotating the metal disc and fastening the hollow metal rod. After passing through the hollow metal rod, a yarn was continuously wound by a rotating take-up roll. The morphologies of polyacrylonitrile (PAN) nanofiber yarns were characterized. It was found that well-aligned nanofiber yarns with the diameters varying from 52μm to 105μm were fabricated successfully by turning PAN concentrations. In addition, the mechanical behavior test showed that the yarns possessed proper mechanical properties, which could be used for potential applications such as composites and tissue engineering. [Copyright &y& Elsevier]

Electrospun carbon nanofibers were activated with melamine–polyacrylonitrile [melamine‐blended carbon nanofibers (MACNFs)] for use as a fibrous adsorbent for indoor CO2 removal. Although, melamine doping was intended solely to incorporate basic nitrogen functionalities on the nanofibers, it also shortened fabrication time, conserving time, and energy cost. The specific surface area and microporosity of the fibers were enhanced from 412 m2 g−1 and 0.1646 cm3 g−1 to 547 m2 g−1 and 0.220 cm3 g−1, respectively, upon final CO2 activation of the nanofibers. With the chemical properties, we observed significant tethering of pyridine functionality. The sample, MACNF‐7 (10 mL of polymer solution doped with 0.7 g of melamine), provided the optimum melamine doping condition to achieve the highest CO2 adsorption capacity of 3.15 mmol g−1. The adsorption performance was based on simultaneous improvement in microporosity (physical) and surface basicity (chemical) properties of the adsorbent. However, in a binary mixture with nitrogen, the selective adsorption of CO2 showed the predominance of the improved surface basicity over microporosity. The highest CO2 selective capture (1.22 mmol g−1) was occurred for a CO2:N2 ratio of 0.15:0.85, with a selectivity of 58.19 at 273 K. In a regeneration test, stable and robust performance was achieved more than five cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47747. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanofibers (CNF) produced from pyrolysis of electrospun polyacrylonitrile (PAN) precursor has received a great amount of attention due to their promising potentials. However, there are limited studies on the electrical properties of the CNF, especially at high‐frequency range. In this study, CNF from PAN precursor were produced by electrospinning technique. Characterizations of the nanofibers were carried out in terms of physical, dielectric, and chemical properties. The stabilization of nanofibers took place at 240°C whilst carbonization process took place at temperatures of 800°C, 1000°C, and 1200°C, respectively. In terms of physical properties, the color of the nanofiber webs changed from white to brown and black, after stabilization and carbonization process accompanied by significant reduction in average fiber diameter. Dielectric analysis of the nanofibers was obtained by measuring the wave propagation characteristics at frequency range of 1 GHz to 10 GHz. Higher dielectric constants of the material were observed for fibers processed at higher carbonization temperatures. Good conductivity was also observed with loss tangent value that is higher than 1. The results were correlated with FTIR transmittance results, indicating greater amount of carbon are present in the nanofiber material. From the findings, the unique behavior of the nanofibers makes it practically potential for sensor applications. Explorations of future research in this area are to be sought. [ABSTRACT FROM AUTHOR]