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sialon

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[交流] 提供九篇碳纳米管复合材料方面的博士论文

Nanotube/polymer composites: Tailoring the interface for improved mechanical properties.
by Eitan, Amram (Ami).;,Ph.D.
Source: Dissertation Abstracts International, Volume: 65-02, Section: B, page: 0973.;Adviser: Linda S. Schadler.

Abstract:The discovery of carbon nanotubes introduced exciting opportunities in many scientific and technological fields. In particular, their high elastic modulus and their extremely high aspect ratio make carbon nanotubes an optimal candidate as a reinforcing agent in composite materials. The goal of the present research is to prepare uniform multi-walled carbon nanotube (MWNT)-polycarbonate composites, to explore their mechanical properties, and to investigate the reinforcement mechanisms that govern the mechanical properties. Surface modification of the MWNT was first developed to control the interactions between the MWNT and the polymer. As received (AR) and surface modified (EP) MWNT were embedded in bisphenol A polycarbonate by a solution-based process. Tensile tests of the composites showed an increase of the Young's modulus of the composite by 70% due to 5 weight % AR-MWNT compared to pure polycarbonate, whereas EP-MWNT composites of the same loading showed an increase of 95%. Yielding was preserved in all samples. Viscoelastic studies of AR-MWNT composites conducted by dynamic mechanical analysis suggest the existence of an immobilized polymer region caused by the incorporation of the MWNT. This immobilized polymer was detected by the broadening of the loss modulus peak towards higher temperatures, and by the broadening of the relaxation spectra towards longer relaxation times. The existence of an immobilized polymer layer was confirmed by electron microscopic examination of the fracture surface of the composites. The viscoelastic behavior of the EP-MWNT composites showed broadening as well as shifting of the loss modulus peak towards higher temperatures, and shifting of the relaxation spectra, toward lower frequencies. These findings are interpreted by the better inter-mixing that occurs between the immobilized polymer and the bulk polymer in the surface-modified MWNT composites, which affects the behavior of the bulk polymer. This mechanism was reinforced by load transfer studies conducted by strain-sensitive Raman spectroscopy of the composites. Better load transfer efficiency was measured in the EP-MWNT composites as compared to AR-MWNT composites. Based on the present research, reinforcement mechanisms are suggested in nanotube-polymer composites: (i) An adsorbed polymer, which is stiffer than the bulk polymer, increases the actual volume fraction of the reinforcing agent; (ii) Entanglements between the adsorbed polymer layer and the bulk polymer chains make the load transfer between the polymer and the reinforcement more efficient. The differences between the reinforcement mechanisms of traditional fiber composites and nano-filled polymer composites are discussed.

需要者可到我的共享信箱去下载 sialon@56.com;
我还有几篇关于碳纳米管复合材料的博士论文，如果有需求，我会陆续上传的！

[ Last edited by sialon on 2006-4-7 at 20:22 ]

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Single walled carbon nanotubes: Suspension in aqueous/surfactant media and chirality controlled synthesis on surfaces.
by Moore, Valerie C.;,Ph.D.
Source: Dissertation Abstracts International, Volume: 66-03, Section: B, page: 1490.;Adviser: Richard E. Smalley.

Abstract:Single walled carbon nanotube (SWNT) researchers have many obstacles to overcome before SWNTs become commercially applicable including two equally important but separate issues: suspending pristine, individual SWNTs in water and chirality controlled synthesis. The first part of this thesis describes how to suspend, analyze, and manipulate individually suspended SWNTs in twenty four different surfactants and polymers. The second part of this thesis explains how to attach a metal nanoparticle to the open end of a short SWNT and seamlessly grow the same chirality SWNT.;Suspending pristine, individual SWNTs in water is critical for some composite material applications and any biological application. This research characterizes the spectral properties and the ability to suspend individual SWNTs for over twenty surfactants and polymers. In addition, methods for concentrating and purifying the SWNT suspensions are detailed. Finally, three examples applications of these SWNT suspensions in material and biomedical application are described.;Being able to synthesize chirality-specific SWNTs in bulk quantities is critical for chirality specific SWNT applications. Currently, the problem lies with the initial SWNT nucleation; there is no control. The method for controlling SWNT chirality proposed in this thesis is a templated growth model using an existing SWNT as the template. A new catalyst particle is attached to the end of a SWNT creating a SWNTcat. During growth the carbon addition is directed through the catalyst to the existing SWNT resulting in seamless, chirality consistent growth. To test the models validity, a proof of concept was carried out on surfaces where the growth could be monitored by atomic force microscopy (AFM). The SWNTcats were prepared with a variety of catalysts in several solvents. Straight, seamless growth of the SWNTcat was seen with a variety of growth conditions proving this is a viable route to large scale synthesis of chirality-specific SWNT production.