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| Author(s): |
Leonardo Dantas Machado
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin |
| Defense date: | 2013-09-24 |
| Examining board members: |
Douglas Soares Galvão;
Antonio Gomes de Souza Filho;
Roberto Mendonça Faria;
Luiz Eduardo Moreira Carvalho de Oliveira;
Ricardo Luís Doretto
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| Advisor: | Douglas Soares Galvão |
| Abstract | |
Low-dimensional carbon nanostructures have been a hot topic of research, but many challenges remain. One is to _nd new low-dimensional materials. Another is to create macroscopic assemblies and devices that make use of the exceptional properties of nanostructures like carbon nanotubes (CNT) and graphene. From a theoretical point of view, there is a need both to explain and to predict new materials and assemblies. These studies need to be carried out in different scales, with different tools. In this thesis, five problems were studied, spanning four scales: (i) We showed how porous graphene can be converted to Biphenylene Carbon by dehydrogenation. We used DFT on a scale of ~ 1 nm. (ii) We showed that the graphynes ?, ? and ? oxidate at different rates, with only the latter being resistant to oxidation. We used a reactive force field on a scale of ~ 10 nm. (iii) We studied the self organization of CNTs in serpentines on stepped substrates. We showed that besides the steps the only ingredients needed are a long enough CNT and a forward impulse. We used a non reactive force field on a scale of _ 100 nm. (iv) We simulated the assembly of yarns from CNT forests by pulling tubes from model forests. We showed that during the pulling the larger bundles in the forest are brought together by the smaller ones. We also proposed that a degree of amorphous carbon might be beneficial to yarn drawing. We used a non reactive force field on a scale of ~ 100 nm. (v) We found that the torsional actuation of carbon nanotube yarns should not scale well with increasing diameters using finite element models. We also showed that a mechanism that was proposed to explain the increase in tensile actuation in certain situations was not in accordance with linear elasticity. We used continuum models on a scale of ~ 100 µm. By making use of different methods to study many scales, many problems can be treated, and the development of new methods and advances in hardware and in algorithms mean that even more problems should be tractable in the future (AU) | |
| FAPESP's process: | 09/51693-0 - Multi-scale study of structural and mechanical properties of carbon nanotube forests and fibers |
| Grantee: | Leonardo Dantas Machado |
| Support Opportunities: | Scholarships in Brazil - Doctorate |