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The work presents results on the manufacture and comparative assessment of the structure and microstructure parameters of polyacrylonitrile polymer (PAN)-based carbon nano- and micro-fibers. Using the same polymer solution, PAN na...
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The work presents results on the manufacture and comparative assessment of the structure and microstructure parameters of polyacrylonitrile polymer (PAN)-based carbon nano- and micro-fibers. Using the same polymer solution, PAN nano- and microfibers were obtained. The PAN nanofibers were obtained by electrospinning, and microfibers were spun using the conventional solution-spinning method. The PAN-based fiber precursors were annealed to 1000 degrees C, 2000 degrees C and to 2800 degrees C. Using X-ray diffraction and Raman spectroscopy, the structural and microstructural parameters of both types of carbon fibers were examined. The morphology of PAN nanofibers and carbon nanofibers (CNF) were studied by SEM. Both types of ex-PAN carbon fibers (nano and micro) have similar the c-axis spacing (d(002)) values and crystallite sizes after heat treatment to 2000 degrees C presenting turbostratic structure. HR-TEM images of low temperature CNF show uniform microstructure with the misoriented small carbon crystallites along the fiber axis. The ratio of the integrated intensities of the D and G peaks for carbon nanofibers after heat treatment at 2000 degrees C was distinctly higher in comparison to carbon microfibers (CF). After additional annealing the fibers to 2800 degrees C a better structural ordering show CNF. The crystallite sizes (L-c, L-a) in CNF were distinctly higher in comparison to the crystallites in CF. CF consist of two carbon components, whereas CNF contain three carbon components varying in structural and microstructural parameters. One of carbon phases in CNF was found to have the interlayer spacing close to graphite, i.e. 402=0.335 nm. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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Through the pyrolysis of acetylene at 250 degrees C, large quantities of carbon nanofiber bundles (CNFBs), curved carbon nanofibers (CCNFs) and helical carbon nanofibers (HCNFs) can be synthesized selectively by controlling the Fe...
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Through the pyrolysis of acetylene at 250 degrees C, large quantities of carbon nanofiber bundles (CNFBs), curved carbon nanofibers (CCNFs) and helical carbon nanofibers (HCNFs) can be synthesized selectively by controlling the Fe:Cu molar ratio of Fe-Cu nanoparticles. In this study, the systematic experimental results indicated that the Cu content in the Fe-Cu nanoparticles and pyrolysis temperature had great impact on the yield and structure of the final samples. Moreover, the transmission electron microscopic observation indicated that the catalyst nanoparticles were enwrapped tightly by graphite layers, and the obtained HCNFs show good magnetic property. Compared to the methods reported in the literature, the approach described herein has the advantages of being simple, low-cost, and environment-friendly. It is suitable for the controllable and mass production of CNFBs, CCNFs and HCNFs.
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Abstract With the recent advancement in nanoscience and nanotechnology, carbon nanomaterials have achieved great attention owing to their unique physico‐chemical, mechanical, thermal, and electrical properties. Amongst carbon nan...
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Abstract With the recent advancement in nanoscience and nanotechnology, carbon nanomaterials have achieved great attention owing to their unique physico‐chemical, mechanical, thermal, and electrical properties. Amongst carbon nanomaterials, carbon nanofibers (CNF) depict a high surface‐to‐volume ratio, enhanced porosity, high mechanical strength, and low weight (light). Carbon nanofibers‐based nanocomposites (CNFN) have been developed for diverse applications. This review illustrates the recent progress in (a) the CNF synthesis via chemical vapor deposition (CVD) or electrospinning, (b) their functionalization with metals and metal oxides nanoparticles, polymers, alloys, and (c) their applications in environmental, industrial, and biomedical domains. Moreover, this study will be helpful for readers to understand CNF production, including the latest trends and fabrication techniques to obtain efficient, cost‐effective, eco‐friendly CNFN, having enhanced surface area with maximum selectivity, reproducibility, and multi‐potential applications.
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Concrete is the most widely used construction material, and carbon nanofibers have many advantages in both mechanical and electrical properties such as high strength, high Young's modulus and high conductivity. In this paper, the ...
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Concrete is the most widely used construction material, and carbon nanofibers have many advantages in both mechanical and electrical properties such as high strength, high Young's modulus and high conductivity. In this paper, the mechanical and electrical properties of concrete containing carbon nanofibers (CNF) are experimentally studied. The test results indicate that the compressive strength and per cent reduction in electrical resistance while loading concrete containing CNF are much greater than those of plain concrete. Finally, a reasonable concentration of CNF is obtained for use in concrete which not only enhances compressive strength, but also improves the electrical properties required for strain monitoring, damage evaluation and self-health monitoring of concrete.
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A subchronic inhalation toxicity study of inhaled vapor grown carbon nanofibers (CNF) (VGCF-H) was conducted in male and female Sprague Dawley rats. The CNF test sample was composed of > 99.5% carbon with virtually no catalyst met...
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A subchronic inhalation toxicity study of inhaled vapor grown carbon nanofibers (CNF) (VGCF-H) was conducted in male and female Sprague Dawley rats. The CNF test sample was composed of > 99.5% carbon with virtually no catalyst metals; Brunauer, Emmett, and Teller (BET) surface area measurements of 13.8 m2/g; and mean lengths and diameters of 5.8 μm and 158 nm, respectively. Four groups of rats per sex were exposed nose-only, 6 h/day, for 5 days/week to target concentrations of 0, 0.50, 2.5, or 25 mg/m3 VGCF-H over a 90-day period and evaluated 1 day later. Assessments included conventional clinical and histopathological methods, bronchoalveolar lavage fluid (BALF) analysis, and cell proliferation (CP) studies of the terminal bronchiole (TB), alveolar duct (AD), and subpleural regions of the respiratory tract. In addition, groups of 0 and 25 mg/m3 exposed rats were evaluated at 3 months postexposure (PE). Aerosol exposures of rats to 0.54 (4.9 f/cc), 2.5 (56 f/cc), and 25 (252 f/cc) mg/m. 3 of VGCF-H CNFs produced concentration-related small, detectable accumulation of extrapulmonary fibers with no adverse tissue effects. At the two highest concentrations, inflammation of the TB and AD regions of the respiratory tract was noted wherein fiber-laden alveolar macrophages had accumulated. This finding was characterized by minimal infiltrates of inflammatory cells in rats exposed to 2.5mg/m. 3 CNF, inflammation along with some thickening of interstitial walls, and hypertrophy/hyperplasia of type II epithelial cells, graded as slight for the 25mg/m. 3 concentration. At 3 months PE, the inflammation in the high dose was reduced. No adverse effects were observed at 0.54mg/m. 3. BALF and CP endpoint increases versus controls were noted at 25mg/m. 3 VGCF-H but not different from control values at 0.54 or 2.5mg/m. 3. After 90 days PE, BALF biomarkers were still increased at 25mg/m. 3, indicating that the inflammatory response was not fully resolved. Greater than 90% of CNF-exposed, BALF-recovered alveolar macrophages from the 25 and 2.5mg/m. 3 exposure groups contained nanofibers (> 60% for 0.5mg/m. 3). A nonspecific inflammatory response was also noted in the nasal passages. The no-observed-adverse-effect level for VGCF-H nanofibers was considered to be 0.54mg/m. 3 (4.9 fibers/cc) for male and female rats, based on the minimal inflammation in the terminal bronchiole and alveolar duct areas of the lungs at 2.5mg/m. 3 exposures. It is noteworthy that the histopathology observations at the 2.5mg/m. 3 exposure level did not correlate with the CP or BALF data at that exposure concentration. In addition, the results with CNF are compared with published findings of 90-day inhalation studies in rats with carbon nanotubes, and hypotheses are presented for potency differences based on CNT physicochemical characteristics. Finally, the (lack of) relevance of CNF for the high aspect ratio nanomaterials/fiber paradigm is discussed.
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Polyacrylonitrile (PAN)-based composite nanofibers incorporated with high-percentage inexpensive pitch were successfully prepared by a simple electrospinning technique. Low-softening-point naphthalene pitch (NP) has the merit of h...
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Polyacrylonitrile (PAN)-based composite nanofibers incorporated with high-percentage inexpensive pitch were successfully prepared by a simple electrospinning technique. Low-softening-point naphthalene pitch (NP) has the merit of high solubility but inevitably brings about preoxidation problem. Thus the influence of different preoxidation strategies on the morphology, composition, and structure of composite nanofibers was systematically investigated. The results show that there exists a ternary phase diagram consisting of PAN-pitch-solvent and a suitable apparent viscosity of homogeneous solution, which favors the smooth electrospinning and good adjustment for the diameter of carbon nanofibers (100-500 nm). The crystallinity, crystalline order, and electrical conduction of composite nanofibers are enhanced by incorporating graphitizable NP, for example, the electrical resistance of 50% NP-PAN composite nanofiber films after 800 degrees C carbonization decreases about 30%. Both increasing the oxidation temperature and extending the oxidation time are beneficial to the oxidative stabilization of composite nanofibers with a suitable NP percentage below 50%. Gradient heating (240-340 degrees C) and pressurized (0.08 MPa) preoxidations could accelerate the oxidative stabilization of composite nanofibers with a high NP percentage up to 110% and significantly shorten the oxidation time by half. Therefore, this study paves the road for facile preparation of cost-competitive carbon nanofibers with controllable morphology, structure, and properties.
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Herein, we report a facile and scalable method of synthesizing NiMoO4 nanoparticle embedded mesoporous hollow carbon nanofibers by electrospinning. We have synthesized four different NiMoO4-carbon composite nanostructures, each co...
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Herein, we report a facile and scalable method of synthesizing NiMoO4 nanoparticle embedded mesoporous hollow carbon nanofibers by electrospinning. We have synthesized four different NiMoO4-carbon composite nanostructures, each containing a different composition of NiMoO4 and carbon. Amongst these, the composite nanostructure with 50% (wt.) of NiMoO4 displayed an excellent specific capacity of 575 C g(-1) (1438 F g(-1)) at 1 A g(-1) current density and a capacity retention of 88% after 3000 cycles; while the pure electrospun NiMoO4 nanofibers displayed a specific capacity of 385 C g(-1) (836 F g(-1)) and a capacity retention of only 72%. An asymmetric supercapacitor fabricated from this composite nanostructure and activated carbon displayed a high specific capacity of 135 C g(-1) (85 F g(-1)) at 1 A g(-1) and a capacity retention of 92% after 3000 cycles. A high energy density of 30 WhKg(-1) and a power density of 403 WKg(-1) have been achieved. The enhanced capacity of the NiMoO4-carbon composite nanofibers could be attributed to the mesoporous size of the hollow carbon nanofibers (similar to 3.4 nm), their high specific surface area (similar to 253 m(2) g(-1)) and the increased reactivity due to the nanosized metal oxide particles. The improved cyclability can be attributed to the structural stability gained by embedment of the particles into the hollow carbon matrix that acts as a buffer during the volume changes of the cycling process. Furthermore, the encapsulation of the particles by the onion-like graphitic carbon layers prevents the particles from dislodging from the carbon matrix. The synergistic effects from NiMoO4 and carbon enhances the performance that could not be obtained by either of these components alone. These results show that these NiMoO4-carbon composite nanofibers could be promising materials for high performance supercapacitors. (C) 2017 Elsevier Ltd. All rights reserved.
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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 carboni...
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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 the morphology and structural performance of nanofibers was investigated in present study. Results showed that R_1 (the relative intensity radio between Disordered peak and Graphite peak) of nanofibers carbonized at 1000 ℃ 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.
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A new carbon nanofibrous mat with necklace-like structures have been prepared by carbonization of cellulose/carbon black (CB) nanofibers through electrospinning of cellulose acetate/CB blend solution followed by deacetylation. The...
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A new carbon nanofibrous mat with necklace-like structures have been prepared by carbonization of cellulose/carbon black (CB) nanofibers through electrospinning of cellulose acetate/CB blend solution followed by deacetylation. The effect of carbon black on the thermal stability of the precursor and morphology of the CNFs were investigated using thermogravimetric analysis, field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy. The FE-SEM images showed that cellulose derived CNFs form matrix for accomplishing necklace-like fibers containing spherical CB nanoparticles with diameter between 30 and 60 nm after heating of cellulose/CB nanofibers. It is demonstrated that the incorporation of CB particles increases the electrical conductivity from 1.4 to 16 mS and carbon yield from 12 to 30%. Carbon nanofibers based on cellulose/CB was evaluated as a suitable adsorbent for removal of methylene blue (MB) from water. The final dye removal was found to be 97% at the initial MB concentration of 20 mg L-1. This study suggests a new carbon nanofiber structure that will be potentially useful for energy applications and water treatment.
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Electrospun hemoglobin (Hb) microbelts were used as a novel precursor to produce a new class of carbon nanofibers (Hb-CNFs) containing Fe species (Fe_2O_3 and/or Fe-N_4 moiety). The Hb-CNFs modified glassy carbon electrode (Hb-CNF...
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Electrospun hemoglobin (Hb) microbelts were used as a novel precursor to produce a new class of carbon nanofibers (Hb-CNFs) containing Fe species (Fe_2O_3 and/or Fe-N_4 moiety). The Hb-CNFs modified glassy carbon electrode (Hb-CNFs/GCE) exhibits significant oxidation/reduction towards H_2O_2. The observed H_2O_2 oxidation/reduction starting at ca. +0.26 V and +0.15 V (vs. Ag/AgCl) are significantly lower than the values observed at other CNFs modified GCE. The Hb-CNFs/GCE was also applied to the amperometric detection of H_2O_2 and the results showed fast response, high sensitivity, excellent reproducibility, good selectivity, and wide dynamic range with good limit of detection.
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