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The production of high-performance carbon fibers relies heavily on the structural transformations of polyacrylonitrile (PAN) fiber during processing. In this article differential scanning calorimetry (DSC), synchrotron small-angle X-ray scattering (SAXS), and synchrotron wide-angle X-ray diffraction (WAXD) were used to study the changes of the thermal properties, voids and crystal structure of the PAN precursor fibers on industrial lines during the continuous processing stages, i.e., after the treatment in the coagulation bath, after stretching in boiling water and after stretching in high-temperature steam. The findings of this study suggest that after boiling water stretching the molecular chain motion of the PAN precursor fiber weaken, resulting in the expansion of the voids. After high-temperature steam stretching the voids became elliptical and oriented in the stretching direction. Although the boiling water stretching process partially damaged the (100) crystal planes of the PAN precursor fibers, it does not hinder their overall crystalline structure. The high stretching ratio primarily affected the orientation of the molecular chains. This orientation, even in the context of partial crystal plane disruption, further promoted the crystallization of the (100) crystal planes in the fibers. These experiments explored the correlation between the processing technology and fiber structure transformation of PAN-based carbon fibers, resulting in producing a guide for the preparation of high-performance carbon fibers with fewer defects. [ABSTRACT FROM AUTHOR]

A series of Polyacrylonitrile (PAN) co- or terpolymers as PAN-based carbon fiber precursors was prepared using methyl acrylate (MA) as neutral comonomer and fumaric acid (fa) or maleic acid (ma) as acidic comonomer which is trans/cis isomer, respectively. In order to establish the optimized condition of polymerization, PAN polymers with different acrylonitrile weight ratios (92, 94, and 96 wt%) were synthesized with appropriate yield via stepwise solution polymerization system. The efficiency of cyclization reaction of PAN polymers containing fa or ma were dramatically improved as compared to PAN homopolymer, and initiation of cyclization showed a rapid progress at 210 °C despite short thermal treatment time during thermal oxidative stabilization (TOS). Additionally, the char yield of PAN co- or terpolymers was reasonable value which was similar to PAN homopolymer. [ABSTRACT FROM AUTHOR]

Nanomaterials are solid systems composed of 1–100 nm particles. These systems usually include nanomaterial sensors, nanomolecules, imaging technology, drug transportation, and DNA delivery. Therefore, nanomaterials are widely used in biomedicine, biochemical analysis, mechanics, and magnetism. Based on the above background, this paper mainly studies the application of nanomaterials in the repair of basketball sports ligament injury. In this paper, the nanomaterials used in medical treatment were analyzed, and the polyacrylonitrile based carbon fiber was selected to replace the anterior cruciate ligament (ACL). In this paper, based on polyacrylonitrile based carbon fiber for ACL replacement surgery in rabbits, the drawer test, IKDC score, and Lysholm score were compared between the rabbits after operation and those in the control group. The experiment proved that the function of the left knee joint was gradually restored after the ACL was excised and replaced by polyacrylonitrile based carbon fiber. After 8 weeks, the function of the left knee joint recovered 90%, which proved the feasibility of polyacrylonitrile based carbon fiber in the repair of anterior cruciate ligament injury. [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]

PAN-based carbon fiber is a type of brittle material whose fracture surface has a structure peculiar to brittle materials. The tensile strength of a carbon fiber is determined by the strength of weak links in the fiber to a large extent. Since fracture surface is a type of weak link, the fracture surfaces of PAN-based carbon fibers were investigated in this article. SEM (Scanning Electron Microscopy) micrographs of selected carbon fibers with different tensile strengths were analyzed on computer and the fractal dimensions of fracture surfaces were obtained on the basis of fractal theories. The relationship between the tensile strength of PAN-based carbon fiber and the fractal dimension of its fracture surface was demonstrated. [ABSTRACT FROM PUBLISHER]

A new solid-phase extraction method utilising polyacrylonitrile activated carbon fibres (PAN-ACFs) as adsorbent was developed for the preconcentration of trace metal ions prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The PAN-ACFs oxidised with nitric acid were characterised by FT-IR, XRD, SEM and BET analysis. Then the resulting PAN-ACFs were used as solid-phase adsorbent for simultaneously determination of trace Al(III), Be(II), Bi(III), Cr(III), Cu(II), Fe(III) and Pb(II) ions in aqueous solutions. The influences of the analytical parameters on the recoveries of the studied ions were investigated. The optimum experimental conditions of the proposed method were pH: 6.0; eluent concentration and volume: 3.0 mL of 1.5 mol L−1nitric acid; flow rates of sample and eluent solution: 1.5 mL min−1. The preconcentration factors were found to be 67 for Al(III), Bi(III); 83 for Cr(III), Cu(II), Fe(III) and 50 for Be(II), Pb(II). The precision of this method was in range of 1.5%~3.5% and the detection limit of this metal ions was between 0.06~1.50 μg L−1. The developed method was validated by the analysis of a certified reference sample and successfully applied to the determination of trace metal ions in water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Composite nanofibers composed of polyacrylonitrile (PAN)-based carbon nanofibers and bioactive glass (BG) nanoparticles have been prepared by electrospinning and in situ sintering. Morphology observation showed that the BG nanoparticles of size 20-50 nm were uniformly distributed on the surface of composite nanofibers with 350 nm average diameter after carbonization. Biological mineralization indicated the formation of apatite-like layer on the surface of composite nanofibers, in which the composition of carbonate hydroxyapatite was proved by FTIR and XRD analysis. Cell growth dynamics according to cellular morphology, CCK.-8 assay, and alkaline phosphatase activity assay exhibited better cell adhesion, proliferation, and osteogenic induction of bone marrow-derived mesenchymal stem cells cultured on the composite nanofibers, which suggested the higher bioactivity of composite nanofibers compared to pure PAN-based carbon nanofibers. [ABSTRACT FROM AUTHOR]

The effect of atmospheric-pressure plasma treatment on high strength PAN-based carbon fibers had been studied in terms of fiber surface energetics and mode I and II interlaminar fracture toughness of unidirectional carbon fibers/epoxy matrix composites. The surface characterization of plasma treated carbon fibers was investigated by X-ray photoelectron spectroscopy (XPS) and contact angles. As a result, the plasma treatment changed the surface properties of the carbon fibers, mainly through formation of oxygen functional groups like hydroxyl, carbonyl, and carboxyl groups. According to contact angle measurements, it was observed that plasma treatment led to an increase in surface free energy of the fibers, mainly due to the increase of its specific component. Fracture toughness test results employing double-cantilever beam (DCB) and end notched flexure (ENF) specimens also showed that the increase in specific components or hydrogen bonding between the –OH groups on carbon fibers and the =O ring in epoxy matrix resins played an important role in improving the degree of adhesion at interfaces, resulting in an increase in the interfacial fracture toughness of the composites studied. [ABSTRACT FROM AUTHOR]