An Effective Method for Hybrid CNT/GNP Dispersion and Its Effects on the Mechanical, Microstructural, Thermal, and Electrical Properties of Multifunctional Cementitious Composites

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.

Ultra-Sensitive Affordable Cementitious Composite with High Mechanical and Microstructural Performances by Hybrid CNT/GNP

“…Nowadays, a successful feasible and compatible technique for hybrid CNT + GNP dispersion in aqueous suspension to be used in multifunctional cementitious composites has been developed by 10% Pluronic F-127 with the addition of TBP through 3 h sonication (80 w, 45 kHz) at 40 • C [32]. In this route, first TBP (50 wt.% of Pluronic) was completely dissolved in 225 mL water for 12 h using a magnetic stirrer at 800 rpm/min.…”

“…As the nanoscale cracks grow and expand over time, larger micro-scale cracks can develop, which may cause structural failures [4][5][6]. Timely detection of these intrinsic damages in initial phases can prevent their progression and the Table 1 summarizes the characteristics of the GNPs and multi-wall carbon nanotubes MWCNTs as provided by the manufacturer [32]. The Morphology of GNP + CNTs (dry mix) was characterized using a scanning electron microscope as depicted in Figure 1.…”

“…According to previous research, to prevent formation of any porosities caused by surfactant function, tributyl phosphate (TBP) with ½ of surfactant weight ratio was used as antifoam [23]. Their chemical structures are presented in Figure 2 [32]. The ordinary Portland cement type I (CEM I 42.5R) and CEN Standard sand (EN 196-1 and ISO 679: 2009) were used to prepare mortar mixtures.…”

“…The ordinary Portland cement type I (CEM I 42.5R) and CEN Standard sand (EN 196-1 and ISO 679: 2009) were used to prepare mortar mixtures. The chemical composition and grain size curve of cement and sand are presented in Tables 2 and 3, and Figure 3 [32]. For CNTs and GNPs dispersion in aqua suspension, a non-covalent surfactant (Pluronic F-127) was used in this study.…”

“…Their chemical structures are presented in Figure 2 Table 2. Particle size distribution of the sand [32].…”