Abstract
The interfacial adhesion between asphalt binder and carbon nanotubes (CNTs) depends on many nanoscopic properties such as diffusion of SARA molecules on CNTs surface. Functionalization of CNTs with Oxygens (O=CNTs), hydroxyl groups (HO–CNTs), and hydrogens (H–CNTs) has been an effective way to modify the surface properties of CNTs and ultimately the macroscopic properties of the CNT-composites. This paper presents the effect of different dosages of oxygenated and hydrogenated CNTs on the adhesion and diffusion of SARA molecules on CNTs’ surfaces. First, reactive molecular dynamics simulation is used to oxygenate and hydrogenate CNTs up to a certain dosage. Next, it is employed to model the interaction and diffusion of SARA molecules with the functionalized CNTs. We employ the steer molecular dynamic (SMD) and Einstein formula to calculate the adhesion and diffusion properties. The results demonstrate that hydrogenation has little effect on the adhesion energy, while oxygenation can increase adhesion energy up to 100% for 25% dosage. The diffusion coefficient dramatically drops for both oxygenated and hydrogenated CNTs, with lower values for the latter. We observe that for hydrogenated and oxygenated CNTs at different dosages, asphaltene, resin, aromatic, and saturate molecules have the highest to lowest values, respectively.
Highlights
Since their discovery in 1991, many researchers have extensively studied carbon nanotubes (CNTs) for their exceptional properties such as low density, high mechanical properties, and outstanding electronic properties [1]
There has been a great interest in employing CNT, graphene, graphene oxide (GO)- and polymer grafted graphene as modifiers to improve fatigue life and performance of asphalt binders [11,12,13,14,15]
After constructing the model of hydrogenated and oxygenated SARA-CNT, the system is minimized by using a conjugate gradient (CG) and Hessian-free truncated Newton algorithm methods for 100,000 steps and is equilibrated at 300 K for 1000 ps with 0.25 fs timestep in NVT ensemble using Nosé-Hoover thermostat
Summary
Since their discovery in 1991, many researchers have extensively studied carbon nanotubes (CNTs) for their exceptional properties such as low density, high mechanical properties, and outstanding electronic properties [1]. Functionalization of CNTs with oxygens (O=CNTs), hydroxyl groups (HO–CNTs), and hydrogens (H–CNTs) have been introduced by many researchers for different applications such as purification, biosensor [4,5,6], hydrogen storage, and semiconductors [7,8,9,10] The functionalized atoms such as oxygens change the intrinsic properties of CNTs through change in sp atomic structure and improve interfacial adhesion and solubility [2]. Many researchers have employed molecular dynamic (MD) to study the properties of the binder at the nanoscale [17,26], diffusion of SARA molecules on various aggregates [20,23,24,25,27,28,29], interactions of GrapheneSARA [30], the interactions of SARA-CNTs and CNTs-aggregate [16,31]. Functionated CNT and GO can be separated in the solution due to their hydrophilic attributes and reduce their cost [33]
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