Multiwalled MWNTs

Carbon nanotubes prepared by several methods are mixed with nanoparticles, amorphous carbon, fullerenes, and other contaminants [1576]. Nanotubes isolated from the mixture contain single-walled (SWNT) as well as multiwalled (MWNT) nanotubes. In general, the diameter of a SWNT is on the order of several nanometers, but the length can be several microns. Thus far, spectroscopic (mainly Raman) studies have been focused on SWNTs of small diameters (<2nm) that become metallic or semiconducting depending on their diameter and chirality. Chemical and physical... 

Carbon nanohibes [multiwall (MWNT) Engineered Nanoparticles Layered silica... 

Recently, TsHs has been encapsulated within single-walled (SWNTs) and multiwalled carbon nanotubes (MWNTs) with internal diameters of 0.8-8 nm. It was shown that the best results were obtained when the internal diameters (1.4—1.5 nm for SWNTs and 1.0-3.0 nm for MWNTs) slightly exceeded the diameter of TsHs (1.2 nm). T8H8 was introduced in the gas phase and reacted with the nanotubes through van der Waals interactions. ... 

Another interesting type of novel carbons applicable for supercapacitors, consists of a carbon/carbon composite using nanotubes as a perfect backbone for carbonized polyacrylonitrile. Multiwalled carbon nanotubes (MWNTs), due to their entanglement form an interconnected network of open mesopores, which makes them optimal for assuring good mechanical properties of the electrodes while allowing an easy diffusion of ions. 

In view of the conductive and electrocatalytic features of carbon nanotubes (CNTs), AChE and choline oxidases (COx) have been covalently coimmobilized on multiwall carbon nanotubes (MWNTs) for the preparation of an organophosphorus pesticide (OP) biosensor [40, 41], Another OP biosensor has also been constructed by adsorption of AChE on MWNTs modified thick film [8], More recently AChE has been covalently linked with MWNTs doped glutaraldehyde cross-linked chitosan composite film [11], in which biopolymer chitosan provides biocompatible nature to the enzyme and MWNTs improve the conductive nature of chitosan. Even though these enzyme immobilization techniques have been reported in the last three decades, no method can be commonly used for all the enzymes by retaining their complete activity. 

Multivariate curve resolution, 6 54—56 Multivariate linear regression, 6 32—35 Multivariate optical elements (MOE), 6 68 Multiwalled carbon nanotubes (MWCNTs), 77 48, 49 22 720 26 737. See also Carbon nanotubes (CNTs) Multiwall nanotubes (MWNTs) synthesis of, 26 806 Multiwall fullerenes, 12 231 Multiwall nanotubes (MWNTs), 12 232 Multiwall paper bags, 78 11 Multiway analysis, 6 57-63 Multiyear profitability analysis, 9 535-537 Multiyear venture analysis, 0 537-544 sample, 9 542-S44 Mummification, 5 749 Mumps vaccine, 25 490 491 Mumps virus, 3 137 Municipal biosolids, as biomass, 3 684 Municipal distribution, potential for saline water use in, 26 55-56 Municipal effluents, disposal of, 26 54 Municipal landfill leachate, chemicals found in, 25 876t... 

Fig. 12.3 Fabrication of the nanocomposite paper units for battery, (a) Schematic of the battery assembled by using nanocomposite film units. The nanocomposite unit comprises LiPF6 electrolyte and multiwalled carbon nanotube (MWNT) embedded inside cellulose paper. A thin extra layer of cellulose covers the top of the MWNT array. Ti/Au thin film deposited on the exposed MWNT acts as a current collector. In the battery, a thin Li electrode film is added onto the nanocomposite, (b) Cross-sectional SEM image of the nanocomposite paper showing MWNT protruding from the cel-lulose-RTIL ([bmlm] [Cl]) thin films (scale bar, 2pm). The schematic displays the partial exposure of MWNT. A supercapacitor is prepared by putting two sheets of nanocomposite paper together at the cellulose exposed side and using the MWNTs on the external surfaces as electrodes, (c) Photographs of the nanocomposite units demonstrating mechanical flexibility. Flat sheet (top), partially rolled (middle), and completely rolled up inside a capillary (bottom) are shown (See Color Plates)...

Fig. 12.3 Fabrication of the nanocomposite paper units for battery, (a) Schematic of the battery assembled by using nanocomposite film units. The nanocomposite unit comprises LiPF6 electrolyte and multiwalled carbon nanotube (MWNT) embedded inside cellulose paper. A thin extra layer of cellulose covers the top of the MWNT array. Ti/Au thin film deposited on the exposed MWNT acts as a current collector. In the battery, a thin Li electrode film is added onto the nanocomposite.

Schematic of the hydrogen fuel cell architecture using an ultra-low Pt loading thin-film Pt/ MWNT catalyst layer (MWNT = multiwalled nanotube). (Reproduced with permission from Tang, J. M. et al. Journal of Physical Chemistry C 2007 111 17901-17904. Copyright 2007 American Chemical Society.)...

A single-walled carbon nanotube (S WNT) is a single graphene sheet rolled up in a seamless cylinder, whose diameter is of the order of few nanometers (Fig. 4.12). A double-walled carbon nanotube (DWNT) consists of rolled two graphene layers, and a multiwall carbon nanotube (MWNT) exhibits several co-axial rolls of graphene sheets, one sitting in each other and separated by about 0.35 nm. 

An other interesting strategy is the modification of the surface of the electrodes with multiwalled carbon nanotubes (MWNTs) or single-walled carbon nanotubes (SWNTs) [13,32]. The MWNTs are grown on the electrodes covered with a nickel catalyst film by plasma-enhanced chemical vapour deposition and encapsulated in Si02 dielectrics with only the end exposed at the surface to form an inlaid nanoelectrode array [13]. In the other case, commercial SWNTs are deposited on SPE surface by evaporation [32], The carbon nanotubes are functionalised with ssDNA probes by covalent attachment. This kind of modification shows a very efficient hybridisation and, moreover, the carbon nanotubes improve the analytical signal. 

The first carbon nanotubes discovered in nature, such as those produced in Iijima s experiments, were multiwalled nanotuhes (MWNT). Multiwalled nanotuhes consist of a number of concentric carbon cylinders, a set of tubes nested inside each other. They are somewhat complex systems that are relatively difficult to study. An important step forward in research on carbon nanotuhes occurred in 1993, when scientists learned how to make single-walled nanotubes (SWNT). Using the simpler SWNTs, scientists have learned quite rapidly a great deal about the electrical conductivity, tensile strength, flexibility, toughness, and other physical properties of carbon nanotuhes. 

There are multiwalled carbon nanotubes (MWNTs), each consisting of ten inner tubes or more. In a carbon MWNT, the spacing between two adjacent coaxial zigzag tubes (m, 0) and ( 2, 0) is Ad/2 = (0.123/tt)( 2 - i). However, this cannot be made to be close to c/2 = 0.335 nm (the interlayer separation... 

In practice, defect-free coaxial nanotubes rarely occur in experimental preparations. The observed structures include the capped, bent, and toroidal SWNTs, as well as the capped and bent, branched, and helical MWNTs. Figure 14.1.11 shows the HRTEM micrograph of a helical multiwalled carbon nanotube which incorporates a small number of five- and seven-membered rings into the graphene sheets of the nanotube surfaces. 

Coating by a thin layer of PPy has been realized on multiwalled nanotubes (MWNT) [29,91,93], well-aligned MWNT [85] and single-wall nanotubes (SWNT) [88], When MWNT are oxidized, their surface is covered with oxygenated functionalities, which can be used as anionic dopant of a PPy film electrodeposited on the MWNT [94], These films are notably less brittle and more adhesive to the electrode than those formed using an aqueous electrolyte as source of counterion. 

Researchers in the Lille group have also been successful in preparing yarns from polypropyl-ene/multiwalled carbon nanotubes (MWNT) (1% and 2% by mass) nanocomposites.6-86 Fabrics knitted from these yarns were tested by cone calorimetry. PHRR reduced by 50% for a fraction of nanotubes of only 1 wt % but the TTI of the nanocomposite was shorter. This is shown in Figure 24.9. 

For large scale production of carbon nanotubes and nanofibers chemical vapor deposition (CVD) method is most effective. Acetylene, ethylene, propylene, methane, natural gas (consisting predominantly of propane), carbon monoxide were used as a source of carbon [ 1 -8] (in view of large number of publications on CNT synthesis these references are selected arbitrary). Ethylene and possibly propylene are most convenient carbon sources for mass synthesis of high quality multiwall CNT (MWNT). 

We have created pilot installation for CVD production of multiwall carbon nanotubes from ethylene in industrial scale. MWNT produced by this process have average diameter 12-20 nm, surface area near 200-500 m2/g, mass content of minerals 6-20% for non-purified NT and <1% for purified NT. Electron images of MWNT samples with different surface area (200, 390, and 500 m2/g) are shown in Figs. 1-3. 

Abstract. It is shown that reinforcement of PTFE by 15% of multiwall carbon nanotubes (MWNT) results in more than 2 times increase of strength parameters compared to starting PTFE matrix. Non-trivial temperature dependences of electrical resistance and thermal electromotive force were observed. Percolation threshold determined from dependence of the composite specific resistance on MWNT concentration was near 6% mass. Concentration and nature of oxygen-containing MWNT surface groups influence the strength parameters of the composite material. 

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