Multi-Million Fully Atomistic Molecular Dynamics Simulations of Yarn Formation from Carbon Nanotube Forests
- PDF / 941,999 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 84 Downloads / 378 Views
Multi-Million Fully Atomistic Molecular Dynamics Simulations of Yarn Formation from Carbon Nanotube Forests Leonardo D. Machado1, Sergio B. Legoas2 and Douglas S. Galvão1 1
Applied Physics Department, State University of Campinas, Campinas-SP, 13083-459, Brazil. Physics Department, Federal University of Roraima, Boa Vista-RR, 69304-000, Brazil.
2
ABSTRACT In this work we present preliminary results from multi-million fully atomistic classical molecular dynamics simulations carried out to test different existing mechanisms that have been proposed in the literature to explain the drawing of yarns from carbon nanotube forests. Despite the fact that it has been almost ten years since yarns were first drawn, there are still controversies on the mechanisms and necessary conditions that can produce yarns and sheets drawn from carbon nanotube forests. Moreover, few works have tried to understand at atomistic level the details of yarn drawing mechanisms, and no fully atomistic simulations have been carried out so far on this particular subject. Our preliminary results suggest that only direct van der Waals interactions among large bundles seem not to be enough to explain the yarn drawing process. Bundle interconnectors (such as small bundles connecting large bundles) were observed to play a critical role in our simulations. Depending on the topology of these interconnectors it was possible to observe from the simulations fibers/yarn formation from proposed structural models. These models were built based on structural information inferred from scanning electron microscopy data. INTRODUCTION The drawing of carbon nanotube (CNT) yarns and sheets from carbon nanotube (CNT) forests has continually gathered scientific attention since 2002 [1,2]. From the first works up to this day, many applications have been proposed for these materials, such as; polarizers [1], electronic textiles [3], flexible OLEDs [4], support for the weaving of functional powders [5], and torsional artificial muscles [6]. As these are very interesting materials, it is not surprising that much effort has been devoted to understand the details of the mechanisms and necessary conditions that makes a CNT forest drawable, i. e., that allow yarns and sheets to be drawn from it. The first condition proposed to identify drawable and non-drawable CNT forests was that the former was supposed to need to be superaligned [1]. Although there seems to be an agreement that alignment is important, other authors have suggested that good alignment is not enough to ensure drawability, and other factors might be as important, or even more important than it. For example, the overall density of the CNT forest [7], the density of small interconnecting bundles [8], the occurrence of bundle migration [9] and the amount of amorphous carbon in the forest [10,11], have all been identified as possible important factors. Also, the role of the entanglement at different parts of the forest has recently been characterized by measuring the force required to pull a small number of bundles
Data Loading...
