Preparation Of Multi-walled Carbon Nanotubes Research Articles

Preparation of MWCNT reinforced epoxy nanocomposite and examination of its mechanical properties

Multiwalled carbon nanotube (MWCNT) reinforced and unfilled epoxy resins were prepared. Viscosity tests were run on the MWCNT filled and unfilled resins, comparative tensile, three point bending and Charpy impact tests were performed. The viscosity of MWCNT filled epoxy resin has increased by from three to one order of magnitude from the lowest to higher shear rate compared to unfilled epoxy. Owing to this, the simple cast specimen preparation was not applicable in the case of MWCNT filled epoxy; instead of that, a resin injection method was used. According to the results of the mechanical tests, tensile strength has decreased by 4·6% caused probably indirectly by nanotube filling of the resin, but Young's modulus, bending modulus and Charpy impact strength, which characterise resistance against dynamic loads, have increased by 12, 10 and 20% respectively.

Effects of post-treatments on microstructure and hydrogen storage performance of the carbon nano-tubes prepared via a metal dusting process

Preparation of multi-wall carbon nano-tubes (CNTs) is successfully demonstrated via a metal dusting (MD) process, in which a steel coupon and CO–CO 2 mixed gas are the only reactants needed. During the process, fresh Fe–Ni nano-particles are produced spontaneously and continuously from the steel, and consequently catalyze the growth of the CNTs. Post-treatments, including heating in air at 550 °C and etching in boiling nitric acid, are used to purify the as-prepared multi-wall CNTs. The microstructure modification due to the post-treatments are examined with a transmission electron microscopy. The possibility of utilizing the MD-produced CNTs as a hydrogen storage material is also explored in this study.

Mechanical and electrical properties of multi-wall carbon nanotube/poly(lactic acid) composites

The preparation of multi-walled carbon nanotube (MWCNT)/polylactide (PLA) composites is described. High electrical conductivity can be achieved at a low carbon nanotube loading. When only 0.5 parts per hundred parts of resin (phr) modified multi-walled carbon nanotube was added to low-crystalline PLA (LC-PLA), the surface resistance of the composite fell from 5.46×10 15 to 2.61×10 2 Ω (by 10 13 order). The degree of crystallinity of PLA can influence the electrical property of MWCNT/PLA composites apparently. MWCNT dispersion was enhanced by covalent or hydrogen bonding between modified multi-walled carbon nanotube and PLA. The flexural strengths of pristine LC-PLA and 4 phr modified multi-walled carbon nanotube/LC-PLA composites are 102.3 and 120.2 MPa, respectively (representing a difference of 17.5%).

Multi-walled carbon nanotube reinforced poly ( l-lactic acid) nanocomposites enhanced by water-crosslinking reaction

The preparation of multi-walled carbon nanotube (MWCNT)/poly ( l-lactic acid) (PLLA) composites is described. Water-crosslinking technique was adopted to improve the physical characteristics of the nanocomposites. X-ray diffraction results showed that the crystalline of PLLA can be transformed to a natural poly(lactic acid) semicrystalline after water-crosslinking reaction. From differential scanning calorimeter (DSC) study, PLLA crystallization temperature decreases as the increasing of water-crosslinking time. High heat deflection temperature (HDT) of nanocomposite can be achieved at a low carbon nanotube loading and under water-crosslinking reaction. The HDT of PLA was raised from 62 to 106 °C when 1 phr MWCNT was added to PLLA. The composite after water-crosslinking treatment had exhibited better mechanical properties than the non-crosslinked composite because of strong chemical intra-molecular bonding. Also from thermogravimetric analysis (TGA) study, the thermal degradation temperature of the nanocomposite increases with the increasing of water-crosslinking time.

Preparation of multi-walled carbon nanotubes grafted with synthetic poly(l-lysine) through surface-initiated ring-opening polymerization

A surface-initiated ring-opening polymerization approach was used to functionalize multi-walled carbon nanotubes (MWNTs) with linear poly(l-lysine) (PLL). The oxidized MWNTs, which resulted from the treatment of MWNTs with mixed concentrated sulfuric acid and nitric acid, were converted into amino-functionalized MWNTs (MWNT-NH2) by the amidation of carboxylic group on MWNT surface with excess 1,6-diaminohexane. Surface-initiated ring-opening polymerization of ɛ-(benzyloxycarbonyl)-l-lysine N-carboxyanhydride with MWNT-NH2 as the initiator resulted in MWNTs grafted with poly(ɛ-(benzyloxycarbonyl)-l-lysine) (MWNT-g-PLys(Z)). After the acidolysis of benzylcarbamate group of the grafting poly(ɛ-(benzyloxycarbonyl)-l-lysine) chain, water-soluble MWNTs grafted with PLL (MWNT-g-PLL) were obtained. The successful grafting was confirmed by Fourier transform infrared spectroscopy, thermal gravimetric analysis, X-ray photoelectron spectroscopy, elemental analyses, high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy. HRTEM indicates that MWNTs were enveloped by PLL layer. The as-prepared MWNT-g-PLys(Z) and MWNT-g-PLL exhibited excellent ability to disperse homogeneously in THF and water, respectively.

A comparative study of alcohols and ketones as carbon precursor for multi-walled carbon nanotube growth

A comparative study of the growth of multi-walled carbon nanotubes (MWCNTs) from the vapors of methanal, 2-propanone, ethanol, 2-butanone, and 2-propanol was carried out aiming at detecting the role of the carbon source in the quality of the nanotubes. The growth was carried out with a catalyst mixture of Mn and Co salts impregnated in zeolite powder, using a fixed-bed reactor under atmospheric pressure at a temperature of 600 °C. The samples were characterized by High-resolution transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, and thermal analysis. Both the presence of amorphous carbon in the raw sample and the structural characteristics of the MWCNTs depend on the kind of solvent employed in the growth. The role of CH 3 and OH radicals in the MWCNT obtained in this work was determined. Acetone (2-propanone) was found to be the best solvent for the preparation of MWCNTs.

Preparation of multi-walled carbon nanotube supported TiO 2 and its photocatalytic activity in the reduction of CO 2 with H 2O

Multi-walled carbon nanotube (MWCNT) supported TiO 2 composite catalysts were prepared by sol–gel and hydrothermal methods. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy and N 2-adsorption analysis were carried out to characterize the composite catalysts. In using the sol–gel method, the MWCNTs were coated with anatase TiO 2 nanoparticles, and by the hydrothermal method, rutile TiO 2 nanorods were uniformly deposited on the MWCNTs. The photocatalytic activities of the composite catalysts were evaluated by the reduction of CO 2 with H 2O. The results indicate that the addition of an appropriate amount of MWCNTs as supports for TiO 2 could remarkably improve the efficiency of the photocatalytic reaction. The composite catalysts prepared by the sol–gel method lead to the main formation of C 2H 5OH, while HCOOH is found to be the major product on the sample prepared by the hydrothermal method.

Catalytic Chemical Vapor Deposition Preparation of Multi-wall Carbon Nanotubes with Cone-like Heads

Abstract Carbon nanotubes were prepared by catalytic chemical vapor deposition using washable catalyst support of barium and calcium chlorides. It was found that under this experimental condition, carbon nanotubes with cone-like heads are formed. This special shape guarantees easier diffusion and transfer inside the carbon nanotubes due to larger orifices.

Synthesis and characterization of carbon nanotube/polypyrrole core–shell nanocomposites via in situ inverse microemulsion

AbstractWe demonstrate here a feasible approach to the preparation of multiwalled carbon nanotube (MWNT)/polypyrrole (PPy) core–shell nanowires by in situ inverse microemulsion. Transmission electron microscopy and scanning electron microscopy showed that the carbon nanotubes were uniformly coated with a PPy layer with a thickness of several to several tens of nanometers, depending on the MWNT content. Fourier transform infrared spectra suggested that there was strong interaction between the π‐bonded surface of the carbon nanotubes and the conjugated structure of the PPy shell layer. The thermal stability and electrical conductivity of the MWNT/PPy composites were examined with thermogravimetric analysis and a conventional four‐probe method. In comparison with pure PPy, the decomposition temperature of the MWNT/PPy (1 wt % MWNT) composites increased from 305 to 335 °C, and the electrical conductivity of the MWNT/PPy (1 wt % MWNT) composites increased by 1 order of magnitude. The current–voltage curves of the MWNT/PPy nanocomposites followed Ohm's law, reflecting the metallic character of the MWNT/PPy nanocomposites. The cyclic voltammetry measurements revealed that PPy/MWNT composites showed an enhancement in the specific charge capacity with respect to that of pure PPy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6105–6115, 2005

Carbon nanotube synthesis and parametric study using CaCO 3 nanocrystals as catalyst support by CVD

The preparation of multi-walled carbon nanotubes (MWCNTs) by chemical vapor deposition (CVD) method using nanocrystalline CaCO 3 as metal catalyst support was investigated, where acetylene was used as carbon source, and Co, Fe and Ni, as well as their bimetallic compounds as the active component of the catalyst. The smaller size of the CaCO 3 support led to a much higher yield of CNTs than previously reported. It was noteworthy that the best performance was Fe-Co nanoparticles, which gave a high yield of CNTs, as judged by experimental results. Growth temperature affected catalytic activity and the disintegration of the support. The raw product was purified to a high level, with little damage on the CNT structure, as confirmed by thermal gravimetric (TG), micro-Raman and transmission electron microscopy (TEM) analyses.

The preparation of multi-walled carbon nanotubes with a Ni–P coating by an electroless deposition process

The multi-walled carbon nanotubes (MWCNTs, mean diameter: 100–200 nm) with nickel–phosphorous (Ni–P) coatings were obtained by an electroless deposition process. To prepare the MWCNTs covered with continual Ni–P layers, a pre-treatment procedure comprised of acid-cleaning, sensitization and activation has been developed. The resulting MWCNTs have a uniform distribution of the Ni–P layers coated on the MWCNTs with the fibrous appearance maintained. X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations revealed that the as-coated MWCNTs were comprised of the amorphous Ni–P layers and inner carbon nanotubes covered with the Ni–P layers. These amorphous Ni–P-coated MWCNTs were used as precursors for preparing MWCNTs with nanocrystalline Ni–P(crystalline Ni and Ni 3P intermetallic compound) layers by the heat-treatment above 400 °C, which were determined by differential scanning calorimeter (DSC) and XRD studies. The results of this work provide an effective electrochemical method for preparing powdery MWCNTs with Ni–P layer as new composite materials from the aqueous solution.

Studies on the Preparation and Characterisation of Carbon Nanostructures

We present a study on the preparation of multiwalled carbon nanotubes (MWCNT) using chemical vapour deposition (CVD). The CVD produced MWCNT and single wall carbon nanotubes (SWCNT) produced with a laser ablation technique were then chemically modified by substituting carbon atoms with boron and nitrogen atoms. The morphology and the crystal structure of the new class of nanostructures were analyzed by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Investigation on preparation of multiwalled carbon nanotubes by DC arc discharge under N 2 atmosphere

MWCNTs and SWCNT bands were prepared and carbon nanostructures were formed by DC arc discharge under N 2 atmosphere. The effects of nitrogen pressure and flow rate on the yield and morphology of CNTs, and morphology of carbon nanostructures were investigated separately. SEM, HR-TEM, EDX in SEM and TEM, and XRD were performed to characterize the products. It was found that MWCNTs and SWCNTs bands exist in the inner core of the cathode deposit, but the former one is the main product. The suitable N 2 atmosphere should be in the region of 200–300 Torr, and the N 2 flow rate should be smaller than 350 mL/min. The inner diameter and the length of growth of MWCNTs obviously increases with the increase of the N 2 pressure from 0 to 900 Torr, but the change of outside diameter of MWCNTs does not show a good regularity. Both the inner and outside diameters of MWCNTs slightly decrease with the increase of the N 2 flow rate from 0 to 1000 mL/min. Right angle structure of SWCNT band and graphite layers in MWCNT was observed. It is very possible that a little amount of nitrogen atoms has doped into MWCNTs. Several different carbon nanostructures were observed in the products collected from the different parts in the DC arc discharge apparatus.