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The toxic nature of acetaldehyde renders its removal from a wide range of materials highly desirable. Removal of low-concentration acetaldehyde (a group 1 carcinogenic volatile organic compound) using an adsorbent of cellulose-based activated carbon fiber modified by amine functional group (A@CACF-H) is proposed, using 2 ppm of acetaldehyde balanced with N2/O2 (79/21% v/v) observed under continuous flow, with a total flow rate of 100 mL/min over 50 mg of A@CACF-H. The effective removal of the targeted acetaldehyde is achieved by introducing the functionalized amine at optimized content. The removal mechanism of A@CACF-H is elucidated using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (2D-GC TOF-MS), indicating the efficacy of the proposed acetaldehyde removal method. [ABSTRACT FROM AUTHOR]

An isotropic pitch which has a relatively high softening point and an excellent spinnability for general performance carbon fiber was successfully prepared through the low-temperature co-carbonization with ethylene bottom oil (EO). The special bromination and dehydrobromination reaction of the mixed biotar and EO was adapted at a relatively low temperature for minimizing the phase separation of the two raw materials. The optimized reaction conditions for bromination and dehydrobromination were the heat treatments at 110 °C for 1 h with 20 wt% of Br addition and at 320 °C for 3 h under N atmosphere, respectively. After removal of volatile matters by thin layer evaporation at 350 °C, the target spinnable isotropic pitch, which has a relatively softening point of 205 °C and excellent spinnability, was successfully obtained with high synthetic yield of 45 wt%. The carbon fiber fabricated using the obtained isotropic pitch precursor showed an enormous tensile strength of 1200 MPa by heat treatment alone at 800 °C for 5 min. [ABSTRACT FROM AUTHOR]

The structural changes as functions of spinning conditions and heat treatments were investigated with respect to the structural feature of PAN-based carbon fibers by scanning tunneling microscopy (STM). The distinct granule structure on the cross section of both high tensile strength and high modulus carbon fibers was observed by SEM, while slender granule-shape domain on the longitudinal surface was revealed by STM. A structure model was proposed, which depicted that the PAN-based carbon fiber was a heterogeneous structure composed of aggregated mesostructural domains. These domains were closely arranged into spiral form along fiber axis, allowing the fibers have high strength and good elongation. The initial shape and size of domains was determined by the precursor composition and spinning conditions and also strongly depended on the heat-treated temperature and stretching conditions. The smaller or slender domain, the higher tensile strength obtained for fibers. We expect that the PAN-based carbon fiber with better performance should be produced by optimizing the size and shape of these domains. [ABSTRACT FROM AUTHOR]

The structure of carbon nanofiber (CNF) with platelet texture was found to be constructed by a primary structural unit named carbon nano-rod by the authors through comprehensive examination of X-ray diffraction (XRD), high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HR-TEM), and scanning tunneling microscopy (STM). Single carbon nano-rod resembles multi-walled carbon nanotube with 4–5 graphene sheets nested (ca. 2.5nm diameters), but appears to have a hypothetical transverse of hexagonal shape with the inner diameter corresponding to the interlayer spacing. Three-dimensional model of CNF was suggested based on the carbon nano-rods, which are densely stacked perpendicular to the fiber axis to form a typical platelet CNF. Such a structural concept of CNF gives novel views on the correlation between structure and properties of CNFs for potential applications. [Copyright &y& Elsevier]

Selective and efficient synthesis of thin carbon nanofibers (CNF) of fish bone-like texture with diameter below 40 nm was shown at low temperatures (673–873 K) from an ethylene and hydrogen (4:1) mixture, using Ni–Fe alloys supported on carbon blacks of relatively small surface area. A particular alloy of a Ni–Fe (8:2 w/w) was highly dispersed to produce thinner fibers at 753 K than Ni alone or Ni–Fe catalysts of other compositions on carbon black, although the fiber yield was similar when the Ni content was more than 60%. It must be noted that unsupported alloy showed activity when the Ni content was higher than 75% at the same temperature. Catalyst particles were observed by using TEM and XRD to confirm the roles of carbon black and alloy composition on dispersion of the catalyst, even if the catalyst particle was degraded into a finer one at the growth of CNF. Carbon black of smaller surface area carries the catalyst particles on its surface to be active for CNF synthesis. [Copyright &y& Elsevier]

Catalytically grown carbon nanofiber (CNF) was activated with KOH to attain a high surface area with porous structure. The structural change of CNFs through KOH activation was investigated by using SEM, TEM and XRD. KOH activation was found to be effective to develop particular pore sizes on the CNF surface, increasing the surface area of CNF. The increase of surface area in KOH activation of CNF is first ascribed to local broadening of graphene interstices or local burn-off of graphenes, which limit the surface area increase of CNF with the fiber structure maintained. The activation under severe conditions caused to destroy the fiber structure of CNF. Activated CNFs were applied as an electrode for electrical double layer capacitors to be compared to active carbon fibers in terms of the surface properties. [Copyright &y& Elsevier]

The morphological changes of Fe–Ni catalyst for the preparation of carbon nanofiber (CNF) were examined at 5 steps; (1) the precipitation of Fe–Ni carbonate from Fe–Ni nitrate solution, (2) the calcination of Fe–Ni carbonate into Fe–Ni oxide, (3) the reduction of Fe–Ni oxide, (4) the second reduction of Fe–Ni metal before the growth of CNF, and (5) the reaction with CO/H2 for the growth of CNF. The Fe–Ni fine particle was formed from the Fe–Ni aggregate through the second reduction and successive CNF growth from CO/H2. The temperature of these two steps is the most important factor which determines the size and shape of the Fe–Ni fine particle as a catalyst for CNF growth. The lower temperature of 580 °C provided hexagonal particles with very smooth surface sized around 100–200 nm which allowed the growth of platelet CNFs of the same diameter and cross-sectional shape of the formed catalyst particle. At the higher temperature of 630 °C, the Fe–Ni aggregate was found to give the very fine Fe–Ni particles by the two steps; the first step did the Fe–Ni particle sized around 100–500 nm which was successively degraded into smaller particles sized around 20–40 nm, thinner tubular CNFs growing with the contact of CO/H2. Such smaller particles definitely originated from as-precipitated Fe–Ni carbonate through the steps. The metal particle on the top of CNF was almost exclusively composed of Fe although the catalyst particle before the growth of CNFs carried around 65% of iron and 35% of nickel. The preferential activity of Fe to CO gas may cause such the selectivity. The major role of Ni in the present reaction should be limited to provide the uniform particle of Fe. Controlling the size of the Fe–Ni particle through the reduction and reaction steps was proved to be a key factor to determine the dimension and structure of resultant CNF. [Copyright &y& Elsevier]

An inexpensive and general-purpose carbon fiber was prepared using coal tar pitch. In contrast to the solvent extraction process employing expensive solvents, a low-cost centrifugal separation method facilitated the reduction of loss due to the pitch purification and an overall yield increase. The coal tar pitch purified by centrifugation and subsequently co-carbonized with pyrolysis fuel oil improved in spinnability. Moreover, the resulting spinnable pitch had a softening point of 250 °C. The obtained carbon fibers were heat-treated at 1000 °C for 5 min, resulting in a tensile strength of approximately 1000 MPa and an average diameter of 9 μm. In this study, we present an effective method for obtaining low-cost general-purpose isotropic carbon fibers. [ABSTRACT FROM AUTHOR]

Oxidation–stabilization using pressurized air flows of 0.5 and 1.0 MPa could successfully shorten the total stabilization time to less than 60 min for manufacturing mesophase pitch-based carbon fibers without deteriorating mechanical performance. Notably, the carbonized fiber heat-treated at 1000 °C for 30 min, which was oxidative–stabilized at 260 °C without soaking time with a heating rate of 2.0 °C/min using 100 mL/min of pressurized air flow of 0.5 MPa (total stabilization time: 55 min), showed excellent tensile strength and Young′s modulus of 3.4 and 177 GPa, respectively, which were higher than those of carbonized fiber oxidation–stabilized at 270 °C without soaking time with a heating rate of 0.5 °C/min using 100 mL/min of atmospheric air flow (total stabilization time: 300 min). Activation energies for oxidation reactions in stabilization using pressurized air flows were much lower than those of oxidation reactions using atmospheric air flow because of the higher oxidation diffusion from the outer surface into the center part of pitch fibers for the use of the pressurized air flows of 0.5 and 1.0 MPa than the atmospheric one. The higher oxygen diffusivities resulted in a more homogeneous distribution of oxygen weight uptake across the transverse section of mesophase pitch fibers, and allowed the improvement of the mechanical properties. [ABSTRACT FROM AUTHOR]

Petroleum residues are produced as by-products of petroleum refining. Recently, various effective non-fuel uses of petroleum residues have been considered toward a carbon-neutral society. Pyrolysis fuel oil (PFO) is one of the petroleum residues. Advanced utilization of PFO for future non-combustion applications is required. In this study, Mesophase pitch-based carbon fibers (MPCF) were successfully produced from PFO. Spinnable mesophase pitch (SMP), a precursor of MPCF, was prepared using PFO as a raw material through the pressurized heat treatment at 420°C-430 °C. PFO is from the naphtha catalytic cracking process for ethylene production and is mainly composed of 2–4 condensed polycyclic aromatic hydrocarbons (PAHs). The high temperature pressurized heat treatment could result in the PFO-derived SMPs with yield of 23.0 wt% and excellent spinnability. On the other hand, without pressurized heat treatment, the yield was 8.5 wt%. This indicates that pressurized heat treatment significantly contributed to the yield improvement. In addition, the preference for the conversion of PFO molecules into highly condensed PAHs via cata-condensation during pressurized heat treatment at 420°C-430 °C was observed, which may be the main reason for the high yield and excellent spinnability of the resulting SMPs. As a result, the obtained PFO-derived SMPs though the such high-temperature pressurized heat treatment provided the typical radial-random transversal textures and general mechanical performances of MPCF: The tensile strength and Young's modulus of the PFO-derived MPCF graphitized at 2400 °C showed high values of 1.9–2.7 GPa and 554–635 GPa, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Spinnable mesophase pitch with high pitch yield of more than 50 wt% was successfully prepared using direct bitumen coal extracted fraction through the three-step process of hydrogenation, N 2 blowing heat treatment, and thin-layer evaporation. The prepared mesophase pitch was smoothly spun to the fibrous form and could be converted into mesophase pitch-based carbonized and graphitized fibers through the usual oxidative stabilization, carbonization, and graphitization. The prepared mesophase pitch based carbon fibers showed typical random transversal structures with mechanical performances, tensile strengths of 1.83 GPa and 3.00 GPa, Young's moduli of 133 GPa and 450 GPa, and elongation properties of 1.37% and 0.68% after heat treatments at 1000 °C for 30 min and 2800 °C for 10 min, respectively. The relatively high-molecular-weight and well-developed polynuclear aromatic molecular structure of hypercoal is the likely reason for the high mesophase pitch yield. The meaning of each preparation processes, hydrogenation, N 2 blowing heat treatment and thin layered evaporation, was discussed in detail. We anticipate that the success of high-yield mesophase pitch manufacturing using hypercoal as raw material will be an important key to innovatively reduce the production cost of mesophase pitch-based carbon fiber. Image 1 [ABSTRACT FROM AUTHOR]

Coal extract produced by solvent extraction of low-rank coal is not suitable for spinning due to its high oxygen content. In order to effectively overcome this limitation, soft pitch was produced by co-carbonization of coal extract and petroleum residues. The decrease in oxygen content was confirmed by physical property analyses of the soft pitches blended at different mixing ratios. A bridge/hydroaromatic structure of the soft pitch was observed during the co-carbonization. The produced spinnable pitch had a high spinnability and a softening point of 230 °C. This spinnable pitch, prepared by solvent extraction of low-rank coal, showed excellent spinnability and was heat-treated at 800 °C for 5 min to produce isotropic carbon fibers having diameters of 7 μm and a tensile strength of 1189 MPa. Thus, the co-carbonization of coal extract and petroleum residue is an effective method for the production of inexpensive spinnable pitch for isotropic carbon-fiber manufacture. Image 10895 [ABSTRACT FROM AUTHOR]

A cost-effective method for producing an isotropic pitch-based carbon fiber using the 1-methylnaphthalene (MN) soluble fraction of Hyper-coal (HPC) was newly developed. The extent of MN fractionation was controlled by altering the fractionation temperatures. The MN soluble fraction obtained from HPC at 60 °C had excellent spinnability after the removal of volatile matter by thin layer evaporation. Additionally, the fiber that was subsequently derived from the MN soluble fraction had satisfactory mechanical properties with an averaged tensile strength of 1150 MPa after heating to 800 °C for 5 min. [ABSTRACT FROM AUTHOR]

Highlights: [•] Activated carbon fiber with mild activation condition is useful as adsorbent for polar pollutants. [•] Diverse variations are investigated for developing an effective adsorbent. [•] Surface functional group is the most important factor for capacity as a adsorbent. [•] Surface functional groups on ACFs are investigated using micro-ATR FTIR. [Copyright &y& Elsevier]

Abstract: Removal of atmospheric NO to harmless N2 was successfully achieved through the continuous oxidation and reduction of NO into N2 using pitch-based activated carbon fiber (ACF), in which TiO2 and urea were co-supported. The combination of TiO2 and urea on the ACF gave high oxidation and reduction of NO. The TiO2 photocatalyst converted NO into NO2, which was immediately passed over urea on the ACF and reduced into harmless N2. Humidity seemed to accelerate the desorption of NO2 from the TiO2 surface, but did not affect the NO oxidation, indicating that humidity did not interfere with the reaction of NO into N2. The ACF system described is potentially very useful for the harmless removal of NO in the atmosphere near the roadside of urban area using natural wind effectively. [Copyright &y& Elsevier]

Abstract: Polyaniline coated carbon nanofiber was fabricated using one-step vapor deposition polymerization technique. Fourier transform infrared (FT-IR) spectra and transmission electron microscope (TEM) images indicated that uniform and ultrathin conducting polymer layers were formed on the carbon nanofiber surfaces regardless of the coating thickness. It was also confirmed that the thickness of polyaniline layer could be conveniently tuned by the feeding amount of monomer. The coating thickness was dependent on initiator/monomer ratio, the vacuum pressure of reaction chamber and polymerization temperature. Among them, the vacuum pressure was a major factor to control the coating thickness of polyaniline onto the carbon nanofiber surface. In addition, the electrochemical analysis demonstrated that polyaniline coated carbon nanofiber showed an improved performance as supercapacitor. The specific capacitance of polyaniline coated carbon nanofiber exhibited a maximum value of 264F/g when the thickness of polyaniline layer was ca. 20nm. [Copyright &y& Elsevier]

Two ethylene tar-derived isotropic pitch-based fibers were prepared from nitrogen-distilled pitch (NDP) and air-blown pitch (ABP). The resultant fibers were carbonized at different temperatures to investigate the effect of the oxygen-introduced pitch precursor on the properties and structure evolution of fibers during carbonization and graphitization. The tensile strength of the ABP-derived carbon fibers (A-CFs) was higher than that of the NDP-derived carbon fibers (N-CFs) below 1200 °C because more gas was released from the N-CFs during carbonization. However, the mechanical properties of the A-CFs and N-CFs decreased significantly at 1400 °C, which resulted from defects that were produced by the removal of oxygen-containing gas. Above 1400 °C, the mechanical properties improved slightly, and the interlayer spacing decreased with an increase in heat-treatment temperature for two series fibers as a result of the rearrangement and development of microcrystallites. The A-CFs had a lower Young's modulus and a higher electrical resistivity than the N-CFs, because the cross-linked structure in the oxygen-introduced pitch precursor impeded the orientation of its fibers during carbonization and graphitization. Unlabelled Image • The tensile strength of the A-CFs was higher than that of the N-CFs below 1200°C. • Less gas was released from the A-CFs because its pitch precursor contained more stable C O. • The A-CFs had a larger d 002 and a smaller L c compared with the N-CF. • Oxygen-introduced pitch-based CFs had a higher electrical resistivities at a high graphitization temperature. [ABSTRACT FROM AUTHOR]

In this study, spinnable isotropic pitches (IPs) were produced by pyrolytic oils of biomass and polystyrene (PS) with ethylene bottom oil (EBO or pyrolysis fuel oil: PFO) through bromination/dehydrobromination reaction. To develop spinnable pitches, four different tars were produced and hybrid pitches were synthesized using different PFO blending ratios and bromine amounts. Results showed that PFO improves spinnability and pitch yield considerably. Furthermore, pitches with the same softening point (S.P.) were produced from different precursors and spinning, stabilization and carbonization were performed to produce general-performance carbon fiber (CF). In order to explain the structure-property relationship of the products, mechanical, morphological and chemical characterization were done by TOF-MS, elemental analysis, 13C-NMR and SEM-EDX. Thus, a comparison between the characteristics of CFs was made disregarding the S.P.s and more insight into the effect of EBO was gained. Mechanical properties of CFs found to be reasonable, considering typical tensile values of IP-based CFs. Image 1 • Isotropic hybrid pitches were prepared using biomass, PS and PFO for the first time. • Pitches were synthesized via thermal bromination/dehydrobromination reaction. • Effects of precursor, blending ratio and Br amount on pitch characteristics were assessed. • Spinnable hybrid pitches were converted to carbon fiber after stabilization and carbonization.. • Effects of precursor and pitch synthesis were revealed together with the structure-property relationship of CFs. [ABSTRACT FROM AUTHOR]