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The electronic properties of as-prepared and purified DWNT films were tested using the four-probe method. The resistivity of the purified DWNT films is about 1 mΩ cm at room temperature and has a positive dρ/dT above 55 K, which shows a good metallic property. The electrical resistivities of the purified DWNT films are quite similar to those of the SWNT bundles and acid-treated SWNTs. Our results...
Multi-walled carbon nanotubes (MWNTs) with different mean outer diameters in the range of 13-53 nm, synthesized by the catalytic decomposition of hydrocarbons using a floating catalyst method, were purified and pretreated with the same procedure for volumetric hydrogen adsorption/desorption measurements. It was found that the hydrogen storage capacity of the purified and pretreated MWNTs was proportional...
We investigated the growth of multi-wall carbon nanotubes (CNTs) catalyzed by SiO 2 -supported Co-Mo bi-metallic catalyst in flowing CO at 700 o C. We found that both Co and Mo are present in catalytic particles at the tips of CNTs, but their compositions vary from one catalytic particle to another and significantly deviate from the initial mixing composition. The Co concentration...
The synthesis of carbon nanotubes (CNTs) from ethylene decomposition by Fe/Al 2 O 3 and Fe/Ni/Al 2 O 3 catalysts (Fe:Ni=10:1) is studied. A small amount of nickel introduced into the catalyst can significantly increase the yield of CNTs, but the nanotubes change from straight tubes with concentric parallel carbon sheets to helical tubes of the fish-bone type. Raman...
Agglomerated carbon nanotubes (CNTs) were synthesized by catalytic pyrolysis of propylene on Fe/Mo/Al 2 O 3 catalysts in a nano-agglomerate fluidized-bed reactor (NAFBR) of 196 mm I.D. The macroscopic properties and microstructure of the CNTs and their evolution were systematically characterized by high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy...
The formation process of an amorphous carbon nanotube (α-CNT) from poly-(tetrafluoroethylene) using ferrous chloride was investigated by observing the TEM images of the isolated intermediates and conducting in situ TEM observation of its formation. These observations revealed unique features of the nanotube growth process through a series of steps; the growth of the core whisker, the deposition of...
The chemical vapor deposition of the pyrocarbon from a CH 4 +H 2 mixture is investigated using nanofilamentous substrates. The process consists of growing carbon nanotubes via a catalytic process, which then are thickened by pyrolytic carbon deposition to reach diameters in the nanometer to micrometer range. A key characteristic of the experimental reactor used was the long length...
1 3 C NMR spectra and spin-lattice relaxation times were measured for single-wall carbon nanotubes with 99.9 and 50.0% 13 C enrichments and natural abundance (1.1% 13 C) prepared by catalytic decomposition of CH 4 . The 13 C isotropic shift is about 116 ppm from tetramethylsilane, being estimated from magic-angle-spinning (MAS) spectra. The value...
A novel composite membrane consisting of an activated carbon membrane with filamentous carbon, applicable to water treatment, was fabricated by a combination of conventional carbonization and thermal deposition. The carbonization was performed after dipping a ceramic support in a latex polymer followed by the application of ferric sulfate [Fe 2 (SO 4 ) 3 .nH 2 O] catalyst...
A catalyst prepared from the pyrolysis of Co and Mg nitrates and citric acid after their co-dissolution in water was used for carbon deposition from CO. Good yields of nanotubes or nanofilaments were obtained over catalysts which had been reduced by H 2 without preliminary treatment at high temperature. Nanotubes with 10 or more cylindrical carbon layers were obtained from pure CO or from...
Platinum (Pt) electrocatalyst was electrochemically dispersed on well-aligned carbon nanotube (CNT) arrays by a potential-step method. The structure and elemental composition of the resulting Pt/CNT electrode were characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The electrocatalytic properties of the Pt/CNT electrode for oxygen...
A facile method is proposed to use LaNi 2 hydrogen storage alloy as a catalyst precursor to produce metallic nickel filled carbon nanotubes. Multi-walled carbon nanotubes filled with long continuous nickel nanowire with several microns in length are synthesized through chemical vapor deposition at low temperature (550 o C). It is more efficient to fill Ni nanowires into nanotubes after...
Carbon nanofibers (CNFs) of high graphitization degree were prepared by a CVD process at 550-700 o C. They showed different structures according to catalyst and preparation temperatures. The structure of CNF prepared from CO/H 2 over an iron catalyst was controlled from platelet (P) to tubular (T) by raising the decomposition temperature from 550 to 700 o C. The CNFs prepared...
The structure of carbon micro- and nanotubes synthesized by the plasma-enhanced (PE) PE-CVD technique has been investigated by SEM, TEM, SAED and HRTEM. It is shown that tubes are formed by structurally defective versions of conical graphene layers. There are three types of tubes; (1) with a straight inner channel, (2) with a straight channel but helical walls, (3) with a helical channel. In some...
Pyrolytic carbon layers were deposited from methane on planar substrates (pyrolytic boron nitride) at various residence times, methane pressures and deposition temperatures. The depositions were performed in a cavity oriented perpendicular to the gas flow. The small surface area/reactor volume ratio of the reactor geometry allows depositions in the growth and nucleation mechanism. Transmission electron...
We present the results on the fabrication and characterization of high-quality transparent heterojunction between n-type ZnO film and p-type diamond single crystalline film on the substrate of diamond bulk single crystal. The results indicated that the current density of the fabricated p-n junction reaches 110 A/m 2 when the forward bias voltage is 2.5 V, and the turn-on voltage value is about...
Single-walled carbon nanotube networks grown on SiO 2 pillars were studied by means of scanning photoemission microscopy. The individual nanotubes or nanotube bundles growing from the pillar tops were observed in C 1s images. Band bending near catalytic Fe/nanotube contacts in an end-bonded configuration was studied by measuring C 1s spectra along the tube axes. Within our experimental resolution,...
The catalytic chemical vapor deposition (CCVD) method in which the outer furnace is replaced by the high frequency induction heating (IH) has been used for synthesis of carbon nanostructures. Using different catalysts, various types of carbon nanofibers were obtained, with the absence of the catalyst particles at their tip as a common characteristic. The IH mode combined with the CCVD method seems...
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