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The graphene/carbon nanotube (CNT) hybrids are considered as one of the most advanced nanostructures with intrinsically self-dispersion properties for large-volume applications. However, owing to the limited understanding on the complex growth mechanism and non-linear kinetics, rational design of growth procedures and related multiphase reactors for the production of the hybrids remain great challenges...
Introducing graphene protuberances covalently bonded with the graphene sheets is a straightforward strategy to avoid the stacking of graphene layers. The as-obtained unstacked double-layer templated graphene (DTG) is expected to fully demonstrate intrinsic properties of graphene assemblies if its detailed structure and component can be well controlled. Herein, both the lateral size and graphene protuberance...
A family of layered double hydroxides (LDHs) with varied Fe contents were employed as catalyst precursors for the controllable bulk growth of few-layer graphene/single-walled carbon nanotube (G/SWCNT) hybrids in a fluidized-bed reactor through chemical vapor deposition of methane at 950°C. All the G/SWCNT hybrids exhibited the morphology of SWCNTs interlinked with graphene layers. The purity, thermal...
Herringbone carbon nanofibers (CNFs) were efficiently produced by chemical vapor deposition on Ni nanoparticles derived from layered double hydroxide (LDH) precursors. The as-obtained CNFs with a diameter ranging from 40 to 60nm demonstrated herringbone morphologies when they grew on Ni/Al LDH derived catalysts both in the fixed-bed and fluidized-bed reactor. The Ni/Mg/Al, Ni/Cu/Al, as well as Ni/Mo/Mg/Al...
CoMgAl layered double hydroxides were prepared as catalysts for the in situ synchronous growth of graphene and single-walled carbon nanotubes (SWCNTs) from methane by chemical vapor deposition. The as-calcined CoMgAl layered double oxide (LDO) flakes served as the template for the deposition of graphene, and Co nanoparticles (NPs) embedded on the LDOs catalyzed the growth of SWCNTs. After the removal...
Self-organization of nitrogen-doped carbon nanotube (N-CNT) double helices was achieved by chemical vapor deposition (CVD) with Fe–Mg–Al layered double hydroxides (LDHs) as the catalyst precursor. The as-obtained N-CNT double helix exhibited a closely packed nanostructure with a catalyst flake on the tip, which connected the two CNT strands on both sides of the flake. A mechanism for the self-organization...
Single-walled carbon nanotube (SWCNT) double helices were fabricated with directly synthesized FeMoMgAl layered double hydroxide flakes as the catalyst precursor. The as-obtained SWCNT double helices were closely packed, while the screw pitches of the double helices were tunable from 2 to 10μm. Straight millimeter-length SWCNT yarns can be obtained by further stretching the SWCNT double helices.
A simple method is reported for the fast growth of millimeter-tall aligned carbon nanotubes (CNTs). Two silicon substrates were stacked with catalyst layers face to face and CNT growth occurred between them. Based on in situ monitoring, the growth rate of aligned CNTs in stacked area was found to be much (over one magnitude) higher than that in the area with a single substrate. The phenomenon was...
Natural sepiolite mineral was used as a catalyst and catalyst support for the efficient growth of single-walled carbon nanotubes (SWCNTs). With the introduction of hydrogen, uniform active metal nanoparticles can be formed in the fibrous structure of sepiolite ore. High-quality SWCNTs with few defects and a large aspect ratio (over 10 4 ) were synthesized. The structure of the CNTs was modified...
A family of layered double hydroxides (LDHs), such as Fe/Mg/Al, Co/Mg/Al, and Ni/Mg/Al LDHs, were used as catalysts for the efficient growth of single-walled carbon nanotubes (SWCNTs) in a fluidized bed reactor. The LDH flakes were agglomerated into clusters with sizes ranging from 50 to 200μm, and they can be easily fluidized with a gas velocity ranging from 2.3 to 24cm/s. After calcination and reduction,...
A parametric study investigating the impacts of loading amount of active phase, growth temperature, H 2 reduction, space velocity, and apparent gas velocity on the intercalated growth of vertically aligned carbon nanotube (CNT) arrays among lamellar catalyst was performed. A series of Fe/Mo/vermiculite catalysts with Fe/vermiculite ratio of 0.0075–0.300 were tested. Metal particles were dispersed...
Free standing vertically-aligned carbon nanotube (CNT) arrays were released from a quartz substrate on a large scale by using CO 2 as an oxidative reagent to weaken the array–substrate interaction and facilitate their harvest. During the oxidation process, amorphous carbon and carbon in contact with metallic particles were preferentially etched, leading to the easy release of high quality...
Large amount of vertically aligned carbon nanotube (CNT) arrays were grown among the layers of vermiculite in a fluidized bed reactor. The vermiculite, which was 100–300μm in diameter and merely 50–100μm thick, served as catalyst carrier. The Fe/Mo active phase was randomly distributed among the layers of vermiculite. The catalyst shows good fluidization characteristics, and can easily be fluidized...
Fluffy carbon nanotubes (CNTs), which are cotton-like macroscopic structures, are obtained by simple high-speed shearing of vertically aligned CNT (VACNT) arrays. The fluffy CNTs are composed of CNT bundles with a diameter of several micrometers, and have an extremely low apparent density of 3–10g/L. A requisite for their formation is the alignment of CNTs in the initial array. The shear between the...
Vertically aligned carbon nanotube (VACNT) arrays grown on ceramic spheres are obtained from ethylene using a floating catalysis process. The exhaust gas mainly contains light gaseous hydrocarbons, which decreases the contamination at the outlet of the reactor. Linear synchronous growth of the VACNT arrays is demonstrated and the morphology evolution of VACNT array grown on spheres is shown. The VACNT...
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