Size Of Multi-walled Carbon Nanotubes Research Articles

Substrate Effects on the Growth of Multiwalled Carbon Nanotubes by Thermal Chemical Vapor Deposition

Chemical and Materials Engineering Department, University of Alberta, Edmonton, Alberta T6G 2V4, CanadaDifferent shapes and sizes of multiwalled carbon nanotubes (MWCNTs) were prepared by the thermal chemicalvapor deposition (CVD) process using ferrocene and toluene on conducting (cobalt/silicon), semiconducting(silicon) and insulating (quartz) substrates to investigate the change in surface morphology, microstructure andelectron “eld emission properties. The lengths and diameters of the MWCNTs were estimated from the scanningand transmission electron microscopy, revealing that although the lengths were not identical, changing withinm, there was no signi“cant change in diameter. The I

Thermal performance of a novel heat transfer fluid containing multiwalled carbon nanotubes and microencapsulated phase change materials

Three new heat transfer fluids consisting of combinations of multi-walled carbon nanotubes (MWCNT) and microencapsulated phase change materials (MPCMs) were formulated, and tested in a turbulent flow heat transfer loop. Stable nanofluids have been prepared using different sizes of multi-walled carbon nanotubes and their thermal properties like thermal conductivity, viscosity and heat transfer coefficient have been measured. Microencapsulated phase change material slurries containing octadecane as phase change material have been tested to determine their durability and viscosity. A blend of MPCM slurry with MWCNT nanofluid has also been prepared to form a new heat transfer fluid that exhibits unique thermophysical properties including non-Newtonian viscous behavior. Heat transfer experiments have also been conducted to determine heat transfer coefficient and pressure drop values of the MWCNT nanofluids, MPCM slurries, and blends of MWCNT with MPCM under turbulent flow and constant heat flux conditions. The heat transfer results of the MPCM slurry containing octadecane was in good agreement with the published results. A maximum thermal conductivity enhancement of 8.1% was obtained for MWCNTs with diameter of 60–100 nm and length 0.5–40 μm. Heat transfer results indicate that MWCNT nanofluid exhibits a convective heat transfer enhancement in the range of 20–25% in turbulent flow conditions. The blend of MPCMs and MWCNTs was highly viscous and displayed a non-Newtonian shear thinning behavior. Due to its high viscosity, the blend exhibited laminar behavior and lower heat transfer rate, though the maximum local heat transfer coefficient achieved by the blend was comparable to that obtained with MPCM slurry alone. The pressure drop of the blend was also lower than that of the MWCNT nanofluid.

Novel fabrication of silica nanotubes using multi-walled carbon nanotubes as template

Silica nanotubes were synthesized using multi-walled carbon nanotubes (MWCNTs) as template. The as-obtained samples were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM) and photoluminescent (PL) spectroscopy. The results indicate that the thickness of the outer walls is about 10 nm and the inner diameter is completely dependent on the size of MWCNTs. The as-fabricated silica nanotubes emit a strong violet light under excitation of 250 nm.

Assessment of the dermal and ocular irritation potential of multi-walled carbon nanotubes by using in vitro and in vivo methods

In view of increase in the manufacture of various nanomaterials runs the risk of increased human exposure, in vitro screening will serve as a preliminary method to assess possible risk in animal studies. We attempted to know whether the validated in vitro alternative models established for chemicals, drugs, pesticides are suitable for nanomaterials, since these materials differ largely and may interfere with commonly used test systems.In vitro and in vivo studies on ocular and dermal irritation were carried out with two different sizes of multi-walled carbon nanotubes (MWCNT). The results of acute eye irritation toxicity studies with two different sizes of MWCNT in rabbits demonstrated reversible conjunctival redness and discharge and exhibited minimal concern while acute dermal irritation studies indicated that MWCNT of two sizes were non-irritant to the skin of rabbits. Both the sizes of MWCNT revealed non-irritant result in HE-CAM test. In vitro skin (EPISKIN) irritation studies revealed that two sizes of MWCNT are non-irritant to skin. In conclusion this work purports, the future of alternative research lies in the validation of the methodology for nanomaterials.