Growth of carbon nanotubes (CNTs) on metallic underlayers by diffusion plasma-enhanced chemical vapour deposition (DPECVD)

Here, we demonstrate the low-temperature (480–612 °C) synthesis of carbon nanotubes (CNTs) on different metallic underlayers (i.e., NiV, Ir, Ag, Pt, W, and Ta) using diffusion (dc) plasma-enhanced (~20 W, −600 V) chemical vapour deposition (DPECVD). The catalyst used is bi-layered Fe/Al and the feedstock used is a mixture of C₂H₂ and NH₃ (1:4). The crucial component is the diffusion of radical ions and hydrogen generated such as H₂/H⁺/H₂⁺/NH₃⁺/CH₂⁺/C₂H₂⁺ (which are confirmed by in-situ mass spectroscopy) from the nozzle, where it is inserted for most effective plasma diffusion between a substrate and a gas distributor.     

FLUIDIZATION OF CARBON NANOTUBES

Carbon nanotubes (CNTs) can be fluidized in the form of fluidlike agglomerates made of many three-dimensional sub-agglomerates, having a multi-stage agglomerate (MSA) structure and containing large amounts of twisting CNTs of micrometer magnitude.     

Synthesis and modification of multi-walled carbon nano-tubes (MWCNTs) for water treatment applications

Synthesis of MWCNTs by chemical vapor deposition (CVD) of acetylene is investigated at different temperatures. Fe-Co/CaCO₃ catalyst/support prepared by wet impregnation method is used. CaCO₃ was found to be a good support as a high selective material for deposition of CNTs with high purity. The effect of temperature on catalyst/support phases and crystal size was identified by using XRD. The crystallite size was decreased with increase temperature. The effect of growing time and temperature on carbon yield was studied and the deposited MWCNTs increased with temperature. The structure and purity of synthesized CNTs at different temperatures was examined by TEM and the effect of temperature on the surface area of the synthesized MWCNTs was investigated, the surface area decreased as the temperature increased. The prepared CNTs were purified using chemical oxidation method and the effect of acid treatment on CNTs surface was examined by TEM and SEM. The function groups produced at CNTs surface were investigated by using FTIR spectroscopy also the effect of CNTs preparation temperature on FTIR spectra was studied. The functionalized CNTs were used for adsorption of some heavy metals and for removal of some organic dyes from water.     

CeO_2-TiO_2/MWCNTs复合光催化剂的制备及性能

以四氯化钛、硝酸铈为原料,以碳纳米管为载体,通过溶胶-凝胶法结合超临界干燥技术制备CeO2-TiO2/MWCNTs复合光催化剂。利用热重分析(TG)、X射线衍射(XRD)、扫描电子显微镜(SEM)、傅里叶红外光谱(FT-IR)等手段对催化剂进行表征。结果表明,超临界干燥避免了催化剂的团聚,TiO2为锐钛矿型,平均粒径为12nm。4h后对甲基橙、亚甲基蓝和苯酚的降解率分别为99.14%、98.98%、98.56%,TOC的去除率为73.84%、74.56%、84.82%。     

First Principles Simulation of Molecular Oxygen Adsorption on SiC Nanotubes

We study the binding of molecular oxygen to a （5, 0） single walled SiC nanotube, by means of density functional calculations. The center of a hexagon of silicon and carbon atoms in sites on SiCNT surfaces is the most stable adsorption site for 02 molecule, with a binding energy of -38.22 eV and an average Si-O binding distance of 1.698 A. We have also tested the stability of the 02-adsorbed SiCNT/CNT with ab initio molecular dynamics simulation which have been carried out at room temperature. Furthermore, the adsorption of 02 on the single walled carbon nanotubes has been investigated. Our first-principles calculations predict that the 02 adsorptive capability of silicon carbide nanotubes is much better than that of carbon nanotubes. This might have potential for gas detection and energy storage.     

Selective hydrogenation of cinnamaldehyde to cinnamyl alcohol with carbon nanotubes supported Pt-Co catalysts

The Pt-Co catalysts supported on carbon nanotubes (CNTs) have been prepared by wet impregnation and the selective hydrogenation of cinnamaldehyde (CMA) to the corresponding cinnamyl alcohol (CMO) over the catalysts has been studied in ethanol at different reaction conditions. The results show that Pt-0.17 wt%Co/CNTs catalyst exhibits the highest activity and selectivity at a reaction temperature of 60 °C under a pressure of around 2.5 MPa, and 92.4% for the conversion of CMA and 93.6% for the selectivity of CMA to CMO, respectively. The selective hydrogenation for the CO double bond in CMA would be improved as increasing the H₂ pressure, and the selective hydrogenation for the CC double bond in CMA is enhanced as increasing the reaction temperature. In addition, these catalysts have also been characterized using transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), H₂-temperature programmed reduction (H₂-TPR) and H₂-temperature programmed desorption (H₂-TPD) techniques. The results show that Pt particles are dispersed more homogeneously on the outer surface of the nanotubes, while the strong interaction between Pt and Co would improve the increasing of activated hydrogen number because of the hydrogen spillover from reduced Pt⁰ onto CNTs and increase the catalytic activity and selectivity of CMA to CMO.     

Darcy–Forchheimer 3D flow of carbon nanotubes with homogeneous and heterogeneous reactions

This article deals with Darcy–Forchheimer three dimensional (3D) flow of water-based carbon nanotubes (CNTs) with heterogeneous–homogeneous reactions. A bidirectional nonlinear extendable surface has been employed to create the flow. Flow in porous space is represented by Darcy–Forchheimer expression. Heat transfer mechanism is explored through convective heating. Equal diffusion coefficients are considered for both auto catalyst and reactants. Results for single-wall (SWCNT) and multi-wall (MWCNT) carbon nanotubes have been presented and compared. The diminishment of partial differential framework into nonlinear ordinary differential framework is made through suitable transformations. Optimal homotopy scheme is used for arrangements development of governing flow problem. Optimal homotopic solution expressions for velocities and temperature are studied through plots by considering various estimations of physical variables. Moreover the surface drag coefficients and heat transfer rate are analyzed through plots.     

Preparation of Sn films deposited on carbon nanotubes

In this work carbon nanotubes were first grown on copper substrate by chemical vapor deposition method. The Sn deposits were then deposited on the surface of as-grown carbon nanotubes by three different methods: electroplating, electroless plating and displacing methods. The Sn deposits on CNTs surface were characterized by both scanning electron microscope and field emission scanning electron microscope. The compositions of Sn deposits were analyzed by energy dispersive X-ray spectroscope. The results showed that both electroless plating and displacing deposits can but the electroplating deposits cannot cover on the surface of CNTs. Besides C, Sn, Ni and Pd, the electroless deposits also contain element of oxygen and the displacing deposits also contain elements of copper and oxygen.     

Remarkably enhanced photocatalytic activity by sulfur-doped titanium dioxide in nanohybrids with carbon nanotubes

TiO₂ doped S nanohybrids with carbon nanotubes (CNTs) were synthesized with CNTs, thiourea and TiO₂ nanoparticles. The result indicated that the TiO₂ nanoparticles with about 8 nm in size are attached on the sidewall of CNTs. The nanohybrids material can absorb at longer wavelength and the absorption even covers the whole range of visible region than that only TiO₂ nanoparticles. Application of the catalysts to photocatalytic degradation of methylene blue (MB) was tested under visible light irradiation. The result suggests that a high MB degradation activity of S-TiO₂/CNTs due to a reduce band gap of TiO₂ when S is doped, and the decrease in the possibility of electron–hole recombination by CNTs. In addition, the density functional-theory (DFT) calculations of the electronic band structures and density of states (DOS) to understand the bonding states between TiO₂ and CNTs, proved that the TiO₂/CNTs system is stable.     

Preparation of Carbon Nanotubes with High Yield and Narrow Diameter Distribution from C2H2 over LaCu0.2Ni0.8Ox

Carbon nanotubes (CNTs) were prepared by decomposition of C2H2 over newly developed LaCu0.2Ni0.8Ox in the temperature range from 600 to 850℃. The effect of the reaction temperature on the yield of CNTs was investigated in detail. At 680℃,the yield of CNTs reaches 17g/g.catal, or so. The morphology of CNTs was examined by TEM. The diameter of CNTs rangs from 9 nm to 14 nm.