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Abstract: Turbostratic carbon nanofibers (CNFs) with a rough surface, open pore walls, and a defect structure were continuously produced by the thermal decomposition of alcohol in the presence of an iron catalyst and a sulfur promoter at 1100°C under a nitrogen atmosphere in a vertical chemical vapor deposition reactor. A graphite exfoliation technique using intercalation and thermal shock was employed to expand the graphene layers of the as-produced turbostratic CNFs. The hydrogen storage capacity of the turbostratic CNF samples was measured using the volumetric method with a pressure of up to 1MPa at 77K. The hydrogen storage capacities of the as-produced and exfoliated turbostratic CNFs were 1.5 and 5wt%, respectively. The defects on the surface and expandable graphitic structure are considered important keys to increasing the hydrogen uptake in turbostratic CNFs. [Copyright &y& Elsevier]

Abstract: Silicon carbide nanowires (SiCNWs) were synthesized in large quantity using a thermal process with carbon nanotube (CNT)/Si–SiO2 (carbon nanotubes grown on Si–SiO2 core–shell substrates) at 1300°C in an argon atmosphere. The characterization shows that the SiCNWs covered with a thin layer of amorphous SiO2 had diameters of 30–70nm and lengths of 4–10μm. The growth mechanism of the SiCNWs is proposed to be the combination of the chemical vapor deposition (CVD) method and the CNTs confined reaction method. According to the Kubelka–Munk plot, the band gap energy for the SiCNWs was 2.8eV. The Mott–Schottky plot shows that the flat-band potential of the SiCNWs was −0.46V versus NHE and that the material exhibited n-type conductivity. The photoluminescence analysis of the SiCNWs revealed two wide bands of emission peaks centered at about 390 and 470nm (CIE value: x=0.18, y=0.24). [Copyright &y& Elsevier]

An 80-cm long tubular carbon coated membrane was fabricated by chemical vapor deposition (CVD) of methane on a multilayered porous ceramic substrate at a temperature of 1000 °C. The deposition of pyrocarbon on the membrane generated a carbon film, the nature of which not only reduced the pore size of the membrane but also changed the physical properties of the membrane, including its hydrophobicity, electrical conductivity, and thermal conductivity. To ensure a uniform deposition of carbon on the membrane, a CVD apparatus equipped with process piping was employed to periodically reverse the direction of the gas flow in the reactor. The CVD experiments were then conducted by varying parameters such as the rate of flow of the gas mixture (methane and nitrogen), the percentage concentration of methane, and so on. To analyze the uniformity of the carbon film, we measured the electrical resistance of the membrane and the permeation of six gases through the sectioned membranes. In the range of our study, it was found that the flow rate of the gas mixture and the alternation of the direction of the gas flow were two important factors for determining the uniformity of the carbon deposit in the membranes. Observation by scanning electron microscope (SEM) and measurement of the nitrogen permeation of the membranes revealed that fabrication of uniform carbon coated ceramic membranes with a desired pore size is possible for applications involving microfiltration, ultrafiltration, and nanofiltration. In addition, the utilization of the superior properties of the membranes such as hydrophobicity and electrical conductivity were suggested for enhancing the degree of separation of the membranes. [Copyright &y& Elsevier]

Abstract: Thin-walled carbon nanotubes (TWCNTs) were synthesized using a zirconium (Zr) plate by cold-wall chemical vapor deposition of a mixture gas consisting of C2H2 and H2 under a pressure of 1.20torr. The Zr plate was used for the formation of Zr nanocatalysts during the thermal process and used as substrate to eliminate the effects of interactions between catalyst and substrate during CNT synthesis. The TWCNTs were 4–9nm in diameter and a few micrometers long. Nanometer-sized defects on the Zr bulk material may have a low melting temperature, allowing them to form droplet-like catalysts and achieve high carbon solubility for the formation of CNTs. [Copyright &y& Elsevier]

Abstract: High-purity carbon spheres were continuously produced by pyrolysis of acetylene at 1000 °C under a nitrogen atmosphere in a vertical chemical vapor deposition reactor. The produced carbon spheres had diameters in the range of 200–500 nm and were perfectly spherical in shape with rough surfaces. High resolution transmission electron microscopy analysis revealed that the carbon spheres were constructed of heavily distorted graphene layers. The results of the X-ray diffraction pattern and Raman spectra also confirmed that the presence of disordered graphene layers was due to a low graphitization degree. In addition, thermal stability and thermal oxidation of carbon spheres were studied. The results found that the surface of the carbon spheres could be modified and the amount of oxygen-containing functional groups increased after oxidation. In summary, the method provided a catalyst-free, substrate-free, hydrogen-free, and cost-effective synthesis for continuous production of carbon spheres. [Copyright &y& Elsevier]

Abstract: Ultraviolet and visible-light-responsive titania was synthesized and employed in the NO x photomineralization. A thermal decomposition reaction of titanium isopropoxide was carried out with a metal-organic chemical vapor deposition (MOCVD), enabling continuous production of TiO2 nanoparticles. Carbon-containing titanium dioxide with the anatase phase prepared at 500°C under nitrogen atmosphere exhibited high photocatalytic activity for NO oxidation under visible-light illumination. Experimental results indicate that up to 48% removal of NO x can be achieved in a continuous flow type of reaction system under visible-light illumination (green LED). The chamber temperature in this MOCVD process plays an important role in lattice structure formation, and also affected TiO2 carbon content. The carbonaceous species on the TiO2 surface, shown by X-ray diffractometry (XRD), and Raman, UV–vis, and X-ray photoelectron spectroscopies (XPS), is important to the visible-light absorption and visible-light-catalytic mineralization of NO x . [Copyright &y& Elsevier]

Abstract: Multiwalled carbon nanotubes (MWNTs) were synthesized using a chemical vapor deposition floating feed method in a vertical reactor. Effects of the preparation variables on the average diameter of carbon nanotubes were systematically examined using the fractional factorial design (FFD), path of the steepest ascent, and central composite design (CCD) coupled with the response surface methodology. From the FFD study, the main and interactive effects of reaction temperature, methane flow rate, and chamber pressure were concluded to be the key factors influencing the diameter of MWNTs. Two empirical models, representing the dependence of the diameter of carbon nanotubes at the vicinities around maximum (420nm) and minimum (15nm) on the reaction temperature and methane flow rate, were constructed in two independent CCD studies. These models, shown as contour diagrams, indicated that the diameter of carbon nanotubes generally increased with increasing reaction temperature and methane flow rate. Based on both models, the diameter of MWNTs from 15 to 420nm can be controlled precisely by using a continuous CVD fabrication method. [Copyright &y& Elsevier]