Thin films of aligned carbon nanotubes (CNTs) have several interesting properties including the ability to transport ions, electrons, and thermal energy. The current study employed molecular dynamics (MD) simulations to determine the effect of varying functionalization topologies of CNTs on their deposition characteristics under applied electric fields of varying strength. The results indicate that the dynamics of CNT alignment along the direction of applied electric field is relatively faster and smoother in case of pristine CNTs compared to that of functionalized CNTs. Considering CNTs of identical length, pristine CNTs are aligned the closest to the direction of the electric field followed by side-functionalized and end-functionalized CNTs with the total alignment time being roughly similar. With increase in the strength of electric field, E, total alignment time decreases and is inversely proportional to E 2. The final alignment angle (θ∞) and extent of oscillatory response in the case of side- and end-functionalized CNTs are diminished. In contrast with the alignment dynamics, the migration dynamics of pristine CNTs, which tend to agglomerate, is slower and shows some discontinuity compared to the functionalized CNTs. Analysis of the final structure of the deposited CNTs indicate that side-functionalized CNTs produce the most uniformly aligned deposit at relatively weaker electric fields followed by end-functionalized, and pristine CNTs, due partly to their greater extent of solvation, and are therefore a better choice for deposition of uniform CNT films on substrates.
Effective hybrid graphene/carbon nanotubes field emitters by electrophoretic depositionMyriad applications, including sensors and supercapacitors, employ substrates decorated with patterned carbon nanotubes (CNTs) in order to leverage the significant anisotropy in their properties. In the present study, a unique continuum mechanics based model was developed to predict the alignment and migration timescales of CNTs for realistic lab-scale electrophoretic deposition (EPD), which is a popular technique to create aligned deposits of pristine and functionalized CNTs without embedded catalysts. This model was initially validated based on results from molecular dynamics simulations to check for mutual consistency. EPD is a complex process that involves electrophoretic alignment and migration of CNTs towards the substrate, displacement of solvent molecules from the surface of substrate by overcoming an energy barrier, followed by deposition. We simulated ACOOH functionalized CNTs of varying length under a range of applied electric fields (1 V/nm to 5 V/nm) to understand the mechanics of electrophoretic alignment and deposition. The dynamics of alignment and deposition were related to the molecular interactions between the various constituents by calculating friction parameters. The results from the parametric study, which is limited to length scales accessible to molecular dynamics simulations, was scaled up to CNTs of micrometer-scale length by comparing the results with solutions to the continuum scale model. The results indicate that the timescale for rotational alignment of realistic CNTs is of the order of seconds and several orders of magnitudes faster compared to the timescale for migration, which is of the order of thousands of seconds for a channel of diameter of 100 lm. V C 2014 AIP Publishing LLC. [http://dx.
synopsisIn the course of a project on the application of polymers for rock bonding and reinforcement of coal mine structures, the adhesion of epoxy resins to shale mine rock was studied by infrared and Mossbauer spectroscopy. Two types of bonding were identified: primary bonds between silicates and polymer, and hydrogen bonds from organic compounds on the surface of the shale to oxygen in the polymer. These bonds contribute to the adhesive' strength when epoxy resins are used to bind shale. The bonding model, when applied to furfuryl dcohol and polyester resins, predicts inferior binding in the shale system.
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