Abstract
This paper reports a study undertaken to achieve a compatible and affordable technique for the high-quality dispersion of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) in an aqueous suspension to be used in multifunctional cementitious composites. In this research work, two noncovalent surfactants with different dispersion mechanisms (Pluronic F-127 (nonionic) and sodium dodecylbenzene sulfonate (SDBS) (ionic)) were used. We evaluated the influences of various factors on the dispersion quality, such as the surfactant concentration, sonication time, and temperature using UV-visible spectroscopy, optical microscopic image analysis, zeta potentials, and particle size measurement. The effect of tributyl phosphate (TBP) used as an antifoam agent was also evaluated. The optimum suspensions of each surfactant were used to produce cementitious composites, and their mechanical, microstructural, electrical, and thermal behaviors were assessed and analyzed. The best dispersed CNT+GNP aqueous suspensions using Pluronic and SDBS were obtained for concentrations of 10% and 5%, respectively, with 3 hours of sonication, at 40°C, with TBP used for both surfactants. The results also demonstrate that cementitious composites reinforced with CNT+GNP/Pluronic showed better mechanical performance and microstructural characteristics due to the higher quality of the dispersion and the increasing hydration rate. Composites prepared with an SDBS suspension demonstrated lower electrical and thermal conductivities compared to those of the Pluronic suspension due to changes in the intrinsic properties of CNTs and GNPs by the SDBS dispersion mechanism.
Highlights
Various types of multifunctional cementitious composites employing carbon fillers have attracted widespread attention due to their potential applications, including monitoring, thermal management, and transportation [1,2,3,4]
The UV-Vis absorption spectra diagrams for the carbon nanotubes (CNTs)+graphene nanoplatelets (GNPs) suspensions prepared with Pluronic F-127 and Sodium dodecylbenzene sulfonate (SDBS) surfactants are displayed in Figures 4 and 5
The results indicate that the dispersion of CNT+GNP particles was strongly dependent on the surfactant concentration, and the best dispersion occurred with 10% of Pluronic and 5% of SDBS
Summary
Various types of multifunctional cementitious composites employing carbon fillers have attracted widespread attention due to their potential applications, including monitoring, thermal management, and transportation [1,2,3,4]. In many cases, the potential applications of GNPs and CNTs are limited due to their high aspect ratio and large specific surface, which leads to large van der Waals forces and strong π -π interactions originating entanglement and agglomeration [9] This is important in multifunctional cementitious composites that normally use high concentrations of nanofillers to obtain higher electrical or thermal efficiency [10] (causing agglomerate formation and reducing their mechanical and microstructural performance [11]), since the physical properties are of significant importance in multifunctional cementitious composites [12]. The effects of Pluronic F-127 and SDBS on the stability of prepared suspensions of 1% CNT+GNP (0.5 wt% CNT and 0.5 wt% GNP) were evaluated for various concentrations, ultrasonication times, and temperatures and for the presence of tributyl phosphate (TBP, as an antifoam agent) in order to propose a compatible and affordable method for high-quality dispersions of CNT+GNP in multifunctional cementitious composites. We evaluated the effects of the optimally dispersed CNT+GNP suspensions on the microstructure and mechanical, thermal, and electrical behaviors of the cementitious composites, to ensure the efficiency of the technique and the absence of adverse effects
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