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Journal Central

In recent years, flame synthesis has absorbed a great deal of attention as a combustion methodfor the production of metal oxide nanoparticles, carbon nanotubes, and other related carbonnanostructures, over the existing conventional methods. Flame synthesis is an energyefficient,scalable, cost-effective, rapid and continuous process, where flame provides thenecessary chemical species for the nucleation of carbon structures (feed stock or precursor)and the energy for the production of carbon nanostructures. The production yield can beoptimized by altering various parameters such as fuel profile, equivalence ratio, catalystchemistry and structure, burner configuration and residence time. In the present report, diffusionand premixed flame synthesis methods are reviewed to develop a better understandingof factors affecting the morphology, positioning, purity, uniformity and scalability forthe development of carbon nanotubes along with their correlated carbonaceous derivativenanostructures.

The process of oxidizing polyacrylonitrile (PAN)-based carbon fibers converts them into aninfusible and non-flammable state prior to carbonization. This represents one of the mostimportant stages in determining the mechanical properties of the final carbon fibers, but themost commonly used methods, such as thermal treatment (200°C to 300°C), tend to wastea great deal of process time, money, and energy. There is therefore a need to develop moreadvanced oxidation methods for PAN precursor fibers. In this review, we assess the viabilityof electron beam, gamma-ray, ultra-violet, and plasma treatments with a view to advancingthese areas of research and their industrial application.

The breakthrough behaviour of activated charcoal cloth samples against an oxygenanalogue (OA) of sulphur mustard has been studied using the modified Wheeler equation. Activated charcoal cloth samples having different surface area values in the range of 481to 1290 m2/g were used for this purpose. Breakthrough behaviour was found to dependon the properties of the activated charcoal cloth, properties of the OA and the adsorptionconditions. Activated charcoal cloth with a high surface area of 1290 m2/g, relatively largesurface density of 160 g/m2 and coarser fiber structure exhibited better kinetic saturationcapacity value, 0.19 g/g, against OA vapours when compared to others, thus confirming itspotential use in foldable masks for protection against chemical warfare agents.

The prime objective of this research was to study the influence of hot-pressing pressureand matrix-to-reinforcement ratio on the densification of short-carbon-fiber-reinforced, randomlyoriented carbon/carbon-composite. Secondary objectives included determination ofthe physical and mechanical properties of the resulting composite. The ‘hybrid carbon-fiberreinforcedmesophase-pitch-derived carbon-matrix’ composite was fabricated by hot pressing. During hot pressing, pressure was varied from 5 to 20 MPa, and reinforcement wt%from 30 to 70. Densification of all the compacts was carried at low impregnation pressurewith phenolic resin. The effect of the impregnation cycles was determined using measurementsof microstructure and density. The results showed that effective densification stronglydepended on the hot-pressing pressure and reinforcement wt%. Furthermore, results showedthat compacts processed at lower hot-pressing pressure, and at higher reinforcement wt%,gained density gradually during three densification cycles and showed the symptoms of furthergains with additional densification cycles. In contrast, samples that were hot-pressed atmoderate pressure and at moderate reinforcement wt%, achieved maximum density withinthree densification cycles. Furthermore, examination of microstructure revealed the formationof cracks in samples processed at lower pressure and with low reinforcement wt%.

In this study, in order to improve the thermal and electrical properties of epoxy/graphene nanoplatelets (GNPs), surface modifications of GNPs are conducted using silane coupling agents. Three silane coupling agents, i.e. 2-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane (ETMOS), 3-glycidoxypropyltriethoxysilane (GPTS), and 3-glycidoxypropyltrimethoxysilane (GPTMS), were used. Among theses, GPTMS exhibits the best modification performance for fabricating GNP-incorporated epoxy composites. The effect of the silanization is evaluated using transmission electron microscopy (TEM), scanning electron microscopy, thermogravimetric analysis, and energy dispersive X-ray spectroscopy. The electrical and thermal conductivities are characterized. The epoxy/silanized GNPs exhibits higher thermal and electrical properties than the epoxy/raw GNPs due to the improved dispersion state of the GNPs in the epoxy matrix. The TEM microphotographs and Turbiscan data demonstrate that the silane molecules grafted onto the GNP surface improve the GNP dispersion in the epoxy.

We report the preparation of sulfonated reduced graphene oxide (SRGO) by the sulfonationof graphene oxide followed by radiation-induced chemical reduction. Graphene oxideprepared by the well-known modified Hummer's method was sulfonated with the aryldiazonium salt of sulfanilic acid. Sulfonated graphene oxide (SGO) dispersed in ethanolwas subsequently reduced by γ-ray irradiation at various absorbed doses to produce SRGO. The results of optical, chemical, and thermal analyses revealed that SRGO was successfullyprepared by γ-ray irradiation-induced chemical reduction of the SGO suspension. Moreover,the electrical conductivity of SRGO was increased up to 2.94 S/cm with an increase of theabsorbed dose.

High crystallinity coke-based activated carbon (hc-AC) is prepared using a potassium hydroxidesolution to adsorb carbon dioxide (CO2). The CO2 adsorption characteristics of theprepared hc-AC are investigated at different temperatures. The X-ray diffraction patternsindicate that pitch-based cokes prepared under high temperature and pressure have a highcrystal structure. The textural properties of hc-AC indicate that it consists mainly of slit-likepores. Compared to other textural forms of AC that have higher pore volumes, this slit-poreshapedhc-AC exhibits higher CO2 adsorption due to the similar shape between its pores andCO2 molecules. Additionally, in these high-crystallinity cokes, the main factor affecting CO2adsorption at lower temperature is the pore structure, whereas the presence of oxygen functionalgroups on the surface has a greater impact on CO2 adsorption at higher temperature.

Carbonate-type organic electrolytes were prepared using propylene carbonate (PC) and dimethylcarbonate (DMC) as a solvent, quaternary ammonium salts, and by adding differentcontents of 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMImBF4). Cyclic voltammetryand linear sweep voltammetry were performed to analyze conducting behaviors. The surfacecharacterizations were analyzed by scanning electron microscopy method and X-ray photoelectronspectroscopy. From the experimental results, increasing the EMImBF4 content increasedthe ionic conductivity and reduced bulk resistance and interfacial resistance. In particular,after adding 15 vol% EMImBF4 in 0.2 M SBPBF4 PC/DMC electrolyte, the organicelectrolyte showed superior capacitance and interfacial resistance. However, when EMImBF4content exceeded 15 vol%, the capacitance was saturated and the voltage range decreased.

Carbon aerogel is a porous carbon material possessing high porosity and high specific surfacearea. Nitrogen doping reduced the specific surface area and micropores, but it furnishedbasic sites to improve the CO2 selectivity. In this work, N-doped carbon aerogels were preparedwith different ratios of resorcinol/melamine by using the sol-gel method. The morphologicalproperties were characterized by scanning electron microscopy (SEM). Nitrogencontent was studied by X-ray photoelectron spectroscopy (XPS) and the specific surfacearea and micropore volume were analyzed by N2 adsorption-desorption isotherms at 77 K. The CO2 adsorption capacity was investigated by CO2 adsorption-desorption isotherms at298 K and 1 bar. Melamine containing N-doped CAs showed a high nitrogen content (5.54wt.%). The prepared N-doped CAs exhibited a high CO2 capture capacity of 118.77 mg/g (atresorcinol/melamine = 1:0.3). Therefore, we confirmed that the CO2 adsorption capacity wasstrongly affected by the nitrogen moieties.

In this study, carbonized fibers were prepared by using acidically cross-linked LDPE fibers. The surface morphologies of the carbonized fibers were observed by SEM. The effects of cross-linking process temperatures were studied using thermal analyses such as DSC and TGA. The melting and heating enthalpy of the fibers decreased as the cross-linking temperature increased. The cross-linked fibers had a carbonization yield of over 50%. From SEM results the highest yield of carbonized LDPE-based fibers was obtained by cross-linking at a sulfate temperature (170oC). As a result, carbonation yield of the carbonized fibers was found to depend on the functions of the cross-linking ratio of the LDPE precursors.