Polyacrylonitrile Matrix Research Articles

HYGIENIC EFFICIENCY OF WASTEWATER TREATMENT USING POLYMERIC ION-EXCHANGE MATERIALS

Polymeric fibrous ion-exchange materials based on polyacrylonitrile matrix, produced in the form of cation-exchanger KN-1 and anion-exchanger AS-1 were the object of the study. We studied the sorption properties of these materials to heavy metal salts and products of their chemical transformation with flotation reagents. According to obtained results, exchange processes have high speed and materials are characterized by high value of absorption – up to 250 mg/g. The introduction of a cascade filtration scheme ensures the treatment of highly contaminated multicomponent industrial wastewater to levels that comply with the hygienic requirements. The advantages of the materials under study are the possibility of their repeated regeneration (by acid and alkali) without losing their original properties and the possibility of concentrating the desorbed metals for the purpose of their recycling again.

Carbon fibers from polyacrylonitrile/cellulose nanocrystal nanocomposite fibers

Polyacrylonitrile (PAN) fibers containing up to 40 wt% cellulose nanocrystals (CNC) have been successfully stabilized and carbonized to make carbon fibers. Under the batch process, PAN/CNC based carbon fibers exhibit a tensile strength in the range of 1.8–2.3 GPa, and tensile modulus in the range of 220–265 GPa, which are comparable to the control PAN-based carbon fibers. Based on the transmission electron microscopy study, individually distributed CNC regions surrounded by PAN matrix were observed in the stabilized and carbonized fibers. Carbonized fibers show two distinct stabilized and carbonized regions. This study shows that biphasic carbon fibers can be made from the PAN/CNC system.

Lithium‐Ion Batteries: Metal–Organic Gel‐Derived FexOy/Nitrogen‐Doped Carbon Films for Enhanced Lithium Storage (Small 3/2019)

In article number 1804058, Xian-He Bu and co-workers prepare flexible FexOy/nitrogen-doped carbon (FexOy/NC-MOG) electrode by facile electrospinning of Fe-based metal–organic gels (MOGs) followed by high-temperature carbonization. The tiny FexOy active sites are dispersed in nitrogen-doped carbon substrates due to the homogeneous distribution of Fe-based MOGs in the polyacrylonitrile matrix. The special design of FexOy/NC-MOG guarantees its good electrochemical stability in lithium-ion batteries.

Machine-Washable Smart Textiles with Photothermal and Antibacterial Activities from Nanocomposite Fibers of Conjugated Polymer Nanoparticles and Polyacrylonitrile.

Smart textiles based on conjugated polymers have been highlighted as promising fabrics that can intelligently respond to environmental stimuli based on the electrical properties of polymer semiconductors. However, there has been limited interest in the photothermal properties of conjugated polymers that can be applied to smart textiles. We prepared nanoparticles by assembling a conjugated polymer with a fatty acid via an emulsion process and nanocomposite fibers by distributing the conjugated polymer nanoparticles in a polyacrylonitrile matrix. We then fabricated the textiles using the fibers. The resulting fabrics based on nanocomposite fibers show a temperature increase to 50 °C in 10 min under white light irradiation because of efficient photothermal conversion by the conjugated polymer light harvester, while the temperature of a pristine polyacrylonitrile fabric increases to only 35 °C. In addition, excellent antimicrobial activity was confirmed by a 99.9% decrease in the populations of Staphylococcus aureus and Escherichia coli over 24 h because of the effect of the fatty acid in the nanocomposite films and fabrics. Furthermore, the fabric showed efficient durability after a laundry test, suggesting the usefulness of these smart textiles based on conjugated polymer nanoparticles for practical applications.

Interphase Development in Polyacrylonitrile/SWNT Nanocomposite and Its Effect on Cyclization and Carbonization for Tuning Carbon Structures

In this study, the self-stiffening behavior of polyacrylonitrile (PAN)/carbon nanotube (CNT) nanocomposites is used to develop the interphase structure. Instead of multi-walled carbon nanotubes (MWNTs), single-walled carbon nanotubes (SWNTs) were used, since they provide much more interfacial area with PAN matrix. The effects of SWNT content (0–1.5 wt %) and temperature on the structural development of PAN/SWNT nanocomposites during dynamic straining were compared for processing optimization. Using this unique dynamic straining method, we were able to tune the structures, especially the interphase of PAN/SWNT nanocomposites. The degree of crystallinity of nanocomposite could be improved from 54.3 to 58.5% after dynamic straining for 12 h, and the activation of the PAN glass transition increased from 434 to 1192 kJ/mol. The thermal behaviors of PAN and PAN/SWNT films with various degrees of crystallinity were compared by differential scanning calorimeter and thermal gravimetric analysis. The relationships ...

Fabrication of Conductive Macroporous Structures Through Nano-phase Separation Method

Thermoelectric power generation performance is characterized on the basis of the figure of merit, which tends to be high in thermoelectric materials with high electrical conductivity and low thermal conductivity. Porous structures cause phonon scattering, which decreases thermal conductivity. In this study, we fabricated porous structures for thermoelectric devices via nano-phase separation of silica particles from a polyacrylonitrile (PAN) matrix via a sol–gel process. The porosity was determined by control of silica particle size with various the mixing ratio of tetraethylorthosilicate as the precursor of silica particles to PAN. High electrical conductivity was maintained by subsequent carbonization of the PAN matrix in spited of a high porosity. As the results, the conductive porous structures having porosity from 13.9 to 83.3 (%) was successfully fabricated, keeping their electrical conductivities.

Influence of graphene oxide sheets on the pore structure and filtration performance of a novel graphene oxide/silica/polyacrylonitrile mixed matrix membrane

The novel graphene oxide (GO)/silica (SiO2)/polyacrylonitrile (PAN) mixed matrix membranes (MMMs) with high filtration flux and excellent antifouling performance were designed and fabricated in situ by the method of non-solvent induced phase separation (NIPS) from the precursor of PAN hybridized with GO, tetraethoxysilane and 3-aminopropyltriethoxysilane. The influences of GO sheets on the pore and chemical structure, hydrophilic nature and filtration performance of derived GO/SiO2/PAN MMMs were investigated by the scanning electron microscopy, field emission scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray, Fourier transform infrared spectrometer, pure water contact angles and filtration performance. Results indicated that in situ incorporation of GO sheets and SiO2 molecules into PAN matrix via NIPS reconstructs the porous structure of derived GO/SiO2/PAN MMMs with the upright finger-like holes, porous bottom, thinner top layer and high porosity. The spontaneous surface migration or segregation of hydrophilic GO sheets and SiO2 molecules as well as their synergistic interaction occurred during NIPS greatly ameliorate the top surface structure and property of derived membranes with smoother surface, uniform pore structure and good hydrophilicity. The derived GO/SiO2/PAN MMMs exhibit a high water filtration flux of 387 L m−2 h−1 with the bull serum albumin rejection rate up to 99% and significant enhancement of antifouling performance.

Synthesis and Properties of Photoluminescent Carbon Quantum Dot/Polyacrylonitrile Composite Nanofibers

Carbon quantum dot (CQD)/polyacrylonitrile (PAN) composite nanofibers were fabricated using the electrospinning procedure. The composite nanofibers were characterized by scanning electron microscopy, Fourier transformation infrared spectroscopy, UV–visible spectroscopy, fluorescence spectrophotometry, fluorescence microscopy, and reflection spectrophotometry. The produced CQD/PAN composite nanofibers exhibited multicolor emission under different excitation energies, which could be attributed to the presence of CQDs embedded inside the PAN matrix. Fluorescence microscopic images confirmed the uniform dispersion and the photoluminescence behavior of the composite CQD/PAN nanofibers. The produced nanofibers could be easily fabricated and potentially used in a variety of applications like photochemical reactions, biological imaging, and optoelectronic devices.

Enhanced electrochemical performance of sulfur/polyacrylonitrile composite by carbon coating for lithium/sulfur batteries

A carbon-coated sulfur/polyacrylonitrile (C@S/PAN) core-shell structured composite is successfully prepared via a novel solution processing method. The sulfur/polyacrylonitrile (S/PAN) core particle has a diameter of ~ 100 nm, whereas the carbon shell is about 2 nm thick. The as-prepared C@S/PAN composite shows outstanding electrochemical performance in lithium/sulfur (Li/S) batteries delivering a high initial discharge capacity of 1416 mAh g−1. Furthermore, it exhibits ~ 89% retention of the initial reversible capacity over 200 cycles at a constant current rate of 0.1 C. The improved performance contributed by the unique composition and the core-shell structure, wherein carbon matrix can also withstand the volume change of sulfur during the process of charging and discharging as well as provide channels for electron transport. In addition, polyacrylonitrile (PAN) matrix suppresses the shuttle effect by the covalent bonding between sulfur (S) and carbon (C) in the PAN matrix.

Effects of Amino-Functionalized Carbon Nanotubes on the Crystal Structure and Thermal Properties of Polyacrylonitrile Homopolymer Microspheres.

Amino-functionalized multi-walled carbon nanotube (amino-CNT)/polyacrylonitrile (PAN) microspheres with diameter of about 300–400 nm were prepared by in situ polymerization under aqueous solution. The morphology, crystal structure, and thermal properties of amino-CNTs on a PAN homopolymer were investigated by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, X-ray diffraction, and differential scanning calorimetry. The results showed that the amino-CNTs had a significant influence on the morphology of microspheres, and the PAN matrix were grafted onto the surface of amino-CNTs with interfacial bonding between them. The XRD studies showed that the crystal size of amino-CNT/PAN microspheres with lower crystallinity was bigger than in the control PAN homopolymer. The analysis of thermal properties indicated that the amino-CNT/PAN microspheres with lower glass transition temperature had a lower initial temperature and velocity of evolving heat during the exothermic processing as compared with the PAN homopolymer. These results suggested that the incorporation of amino-CNTs into the PAN homopolymer matrix was beneficial for controlling the heat released during the stabilization processing.

Thermosensitive luminous fiber based on reversible thermochromic crystal violet lactone pigment

The aim of this work is to investigate the luminescence color changes of thermosensitive luminous fibers (TLFs). These TLFs are comprised of rare-earth luminescent materials as the luminescence sources, reversible thermochromic crystal violet lactone (CVL) pigment as the luminescence conversion agent, and polyacrylonitrile (PAN) as the matrix. It was found that the TFLs could not only change their color, but also convert the luminescence upon temperature change based on a structural transformation of the CVL pigment. X-ray diffraction (XRD) measurements indicated that rare-earth luminescent materials maintained their basic crystal structure and the CVL pigment was not destroyed by the process of spinning. The scanning electron microscopy (SEM) images of TLFs at the microcosmic angle showed that the CVL pigments were evenly distributed in the PAN matrix and formed a luminescence filter on the surface of the fiber. The differential scanning calorimetry (DSC) and thermogravimetry (TGA and DTG) results indicate that the TLFs possess satisfactory thermostability below 212.6 °C. The color and luminescence of the TLFs were accurately exhibited on the CIE 1931 chromaticity coordinates. The thermosensitive capability of TLFs was qualitatively verified by observing them in water at 40 °C and it was found that the fibers had brilliant luminescence and vivid thermosensitivity.

Novel polyacrylonitrile/potassium sodium niobate composites with superior dielectric and thermal properties

Abstract Polyacrylonitrile (PAN) matrix composites dispersed with potassium sodium niobate (KNN) with volume fraction of 0–30% were prepared by ball milling followed by hot pressing. Density of composites followed the rule of mixture. Good dispersion of KNN particles in PAN matrix was confirmed using SEM. Composite containing 30 vol% KNN in PAN matrix recorded 342% increase in dielectric constant with a low dissipation factor of 0.18 w.r.t. neat PAN matrix. There was slight decrease in the dC resistivity of PAN/KNN composites with increase in KNN concentration but all the compositions showed the values of the order of 109 Ω–m, maintaining their insulating nature. Thermal stability of PAN was improved by incorporation of KNN with char yield at 800 °C going up from 24.8% to 60.9% and temperature for 10 wt% loss (T10) going up from 353 °C to 394 °C.

Nanocomposite films of cobalt-containing polyacrylonitrile as a basis of gas-sensitive material for resistive type sensors

The structure of the metal-carbon nanocomposite based on cobalt-containing polyacrylonitrile (PAN) is studied. The morphology of a surface with the theory of selforganization was analysed. The elemental composition, chemical and electronic states of the elements composing the material films are determined by the X-ray photoelectron spectroscopy (XPS) method. The X-ray diffraction (XRD) method shows that the obtained materials contain crystalline inclusions of CoO, Co3O4 and CoO (OH) in the organic matrix of PAN. Gas-sensitive characteristics of the obtained films.

Orientation and interfacial stress transfer of cellulose nanocrystal nanocomposite fibers

Orientation and interfacial stress transfer in cellulose nanocrystals (CNC) reinforced polyacrylonitrile (PAN) nanocomposite fibers were determined by Raman spectroscopy. The 1095 cm−1 Raman band was used to quantify the orientation of CNC in composite fiber. Under VV (vertical/vertical) mode, polar plots of all composite fibers showed a two-fold symmetry. Under VH (vertical/horizontal) mode, it showed a four-fold symmetry. The CNCs are highly oriented in the composite fiber, which is confirmed by second and fourth order orientation parameters:〈P2(cosθ)〉 and〈P4(cosθ)〉. The 1095 cm−1 Raman band shift under uniaxial deformation was used to characterize the interfacial shear stress transfer between PAN matrix and CNCs.

Electrospinning fabrication and in situ mechanical investigation of individual graphene nanoribbon reinforced carbon nanofiber

Graphene nanoribbons (GNRs) with opened edges and less structural defects are embedded in polyacrylonitrile (PAN)-based carbon nanofibers (CNFs) by electrospinning followed by stabilization and carbonization. GNRs not only can be used as one-dimensional nanofillers, but also act as nanoplatelet template to promote the formation of graphitic carbon in PAN matrix. X-ray diffraction, Raman spectroscopy and N2 absorption are used to analyze the microstructure of GNR-reinforced CNFs. In situ tensile test using a micromechanical device inside a scanning electron microscope (SEM) is carried out to evaluate the mechanical performance of individual GNR-reinforced CNF. The tensile strength and elastic modulus of CNFs reinforced by 2 wt% GNRs with a diameter of ∼160 nm are 3.52 GPa and 70.07 GPa, respectively, which are higher than those of pristine PAN CNFs with similar size, i.e. 2.44 GPa and 28.97 GPa. The rough fracture surface for all GNR-reinforced CNFs suggests that the GNRs can dramatically toughen the fibers. A sword-in-sheath failure is observed in 4 wt% GNR reinforced CNFs, confirming that GNRs are entirely embedded and well aligned along the fiber axis. This study demonstrates the potential of GNRs as a promising reinforcement to improve the formation of graphitic carbon and mechanical performance of CNFs.

Preparation of novel composites based on hydrophilized and functionalized polyacrylonitrile membrane-immobilized NZVI for reductive transformation of metronidazole

For the first time, hydrophilized and functionalized polyacrylonitrile (PAN) membrane was synthesized via two-stage process, addition of polyvinyl alcohol and in situ polymerization of acrylic acid (AA), and nano zero-valent iron (NZVI) was incorporated within modified membrane. The as-prepared PAA/PAN-NZVI (PPN) composites possessed superior reactivity for metronidazole (MNZ) with transformation ratio 2.03 and reaction rate 4.77 times higher than that by bare NZVI. Meanwhile, the enhanced stability and recyclability of PPN composites were maintained over repeated cycles. The major advantages of synthetic method lie in the remarkably increased loading and decreased agglomeration of NZVI. Moreover, with hydrophilized and functionalized synthesis processes of membrane, the potential risk of released iron ions was not a concern due to strong chelation of grafted carboxyl groups. Analyses of morphological characteristics (FE-SEM), chemical structure (FTIR), element valence and groups (XPS) of samples confirmed the successful graft of carboxylic acid groups and formation of a uniform iron nanoparticles coating onto PAN matrix. The reaction kinetics of MNZ with PPN composites were well-described by a two-parameter pseudo-first-order decay model with activation energy of 29.5kJ/mol. The co-solutes except humic acid had a negligible effect on MNZ transformation. Determination of intermediates revealed that nitro reduction, N-denitration and hydroxyethyl cleavage were the main pathways for transformation of MNZ. The findings suggest that the novel composites possess huge potential for antibiotics wastewater treatment.

Electrochemical capacitor improvement fabricated by carbon microfiber composite with admicellar-modified carbon nanotube

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 125Fg−1 at a scan rate of 3mVs−1 (based on cyclic voltammetry) and 82Fg−1 at a specific current of 1Ag−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.

Chemical Bonding Specifics of Hybrid Metal-Polymer Nanocomposites Based on Cobalt Nanoparticles and Polyacrylonitrile: X-Ray Spectroscopy Investigation

The cobalt-containing polyacrylonitrile (PAN) films were fabricated using IR-pyrolysis under low vacuum conditions. It was found that Co/PAN films have a porous structure and cobalt nanoparticles with size 0.1-0.2 μm embedded into PAN matrix. Besides, as a result of interaction between PAN matrix and Co ions unsaturation in the polymer backbone is observed caused by the transformation of the C≡N triple bond to a C=N double bond. At the same time formation of Co-N bond is observed.

One Step Synthesis of Au Nanoparticle-Cyclized Polyacrylonitrile Composite Films and Their Use in Organic Nano-Floating Gate Memory Applications

In this study, we synthesized Au nanoparticles (AuNPs) in polyacrylonitrile (PAN) thin films using a simple annealing process in the solid phase. The synthetic conditions were systematically controlled and optimized by varying the concentration of the Au salt solution and the annealing temperature. X-ray photoelectron spectroscopy (XPS) confirmed their chemical state, and transmission electron microscopy (TEM) verified the successful synthesis, size, and density of AuNPs. Au nanoparticles were generated from the thermal decomposition of the Au salt and stabilized during the cyclization of the PAN matrix. For actual device applications, previous synthetic techniques have required the synthesis of AuNPs in a liquid phase and an additional process to form the thin film layer, such as spin-coating, dip-coating, Langmuir-Blodgett, or high vacuum deposition. In contrast, our one-step synthesis could produce gold nanoparticles from the Au salt contained in a solid matrix with an easy heat treatment. The PAN:AuNPs composite was used as the charge trap layer of an organic nano-floating gate memory (ONFGM). The memory devices exhibited a high on/off ratio (over 106), large hysteresis windows (76.7 V), and a stable endurance performance (>3000 cycles), indicating that our stabilized PAN:AuNPs composite film is a potential charge trap medium for next generation organic nano-floating gate memory transistors.

Manufacturing and investigation of physical properties of polyacrylonitrile nanofibre composites with SiO2, TiO2 and Bi2O3 nanoparticles.

The aim of this study was to produce nanocomposite polymer fibres, consisting of a matrix of polyacrylonitrile (PAN) and a reinforcing phase in the form of SiO2/TiO2/Bi2O3 nanoparticles, by electrospinning the solution. The effect of the nanoparticles and the electrospinning process parameters on the morphology and physical properties of the obtained composite nanofibres was then examined. The morphology of the fibres and the dispersion of nanoparticles in their volume were examined using scanning electron microscopy (SEM). All of the physical properties, which included the band gap width, dielectric constant and refractive index, were tested and plotted against the concentration by weight of the used reinforcing phase, which was as follows: 0%, 4%, 8% and 12% for each type of nanoparticles. The width of the band gap was determined on the basis of the absorption spectra of radiation (UV–vis) and ellipsometry methods. Spectroscopic ellipsometry has been used in order to determine the dielectric constant, refractive index and the thickness of the obtained fibrous mats.