Browsing by Subject "Multi-walled carbon nanotubes"
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Item Flame retardant polyamide 6 nanocomposites and nanofibers : processing and characterization(2012-05) Yin, Xiaoli; Koo, Joseph H.; Krifa, MouradPolyamide 6 (PA6) was melt-blended with an intumescent flame retardant (FR) and nanoparticles (multi-wall carbon nanotubes [MWNTs] and nanoclays) to produce multi-component FR-PA6 nanocomposites. Thermal, flammability properties, char residue morphology, and mechanical properties of FR-PA6 nanocomposites were characterized. The flame retardant properties were enhanced according to UL 94 and microscale combustion calorimeter (MCC) measurements, whereas the thermal stability was decreased. Mechanical properties of the bulk material, especially elongation at break, were severely reduced, with the exception of tensile modulus which increased significantly. FR-PA6 nanofibers were processed via electrospinning. Electrospinnability, morphology of the nanofibers, combustion, and thermal properties were also analyzed. As for the bulk-form nanocomposite, improved combustion properties of these nanofibers were successfully achieved though thermal stability was compromised. With proper FR additive, the synergism between MWNTs and nanoclays was observed in PA6 resin.Item I-V transport measurements of a single unsupported MWCNT under various bending deformations(2008-05) Kim, Suenne; de Lozanne, Alejandro L.The first part of this dissertation is an introduction describing a brief historical background of carbon nanotubes (CNTs) and their pseudo 1D structure responsible for many exotic electronic properties. The second part describes our experimental setup. The third part is about the growing of Multi-Walled Carbon Nanotubes (MWCNTs) by the chemical vapor deposition (CVD) method. Then the fourth part demonstrates a simple but reliable method to make firm contact junctions between MWCNTs and metals such as tungsten (W). The novel point of our method consists, after making a mechanical preliminary contact at a selected MWCNT, in applying a series of voltage pulses across the contact. Thin oxide layers that may form between the MWCNT and the W wire, are removed in steps by the resistive heating and electron impact during the application of each voltage pulse. Furthermore, this simple process of contact welding in steps does not bring about any permanent change in the electronic transport properties of the MWCNTs. The fifth part discusses our bending experiments. We apply a uniform and continuous bending to a selected MWCNT at room and liquid nitrogen temperatures to study the strain effect on the electrical transport in the MWCNT. There are a few published experimental works related to the bending deformation; however, this is the first study of electronic transport properties in continuous bending and releasing deformations. We observed a saturation behavior with the MWCNT and also found the bending deformation causing an anomalous change in the saturation behavior. In the sixth part we depict some interesting phenomena due to the stretching deformation of MWCNT, where we were able to propose a simple model for electron localization induced by the deformation. The last part deals with the formation of the "X-junction" between two MWCNTs. A strong X-junction can be formed simply by means of the e-beam inside the Scanning Electron Microscope (SEM). The X-junctions may form the basic elements of nano-electronic circuits such as various metal-insulator junctions, quantum dots, and similar devices.