213 / 2022-06-07 16:53:17

A general approach to exfoliate and disperse 2D nanomaterials for improving cement hydration and chloride binding

2D nanomaterials; Graphene quantum dots; Dispersion; Hydration; Chloride binding.

Tremendous progress has been made in the employment of two-dimensional (2D) nanomaterials in cement composites. However, poor dispersion of 2D nanomaterials immensely hinder their extensive use. To address these issues, in this work, a simple and general method for exfoliating 2D nanomaterials (GO, CLDH, CN) which use graphene quantum dots (GQDs) and low-power ultrasonic treatment was elaborately designed to efficiently delaminate and disperse 2D nanomaterials, and investigate the effects of 2D nanomaterial dispersion on cement hydration and chloride binding properties in depth (Fig. 1). The addition of GQDs significantly improves the material's dispersibility, as evidenced by its morphological and structural characteristics, compared to 2D nanomaterials without GQDs-assisted exfoliating. The exfoliation mechanism of GQDs acting on 2D nanomaterials is reasonably proposed based on their properties and the dispersion results of three 2D nanomaterials. Furthermore, the effect of the dispersion method on cement hydration was investigated, and a correlation was established between the dispersion parameters of 2D nanomaterials, cement mechanical properties, and cement hydration degree. More importantly, highly dispersed 2D nanomaterials (G-GO、G-CLDH and G-CN) was more propitious to accelerate cement hydration and refine microstructure, thereby dramatically boosting the compressive strength of cement paste at 7-day curing by 43% , 52% and 46% compared with that of GO、CLDH and CN, respectively. And the 2D nanomaterials assisted by GQDs exfoliation can generally increase the chloride ion curing capacity of cement-based materials by 50%, compared with the control group. This research shows that GQDs have a great deal of potential for dispersing 2D nanomaterials, that they can significantly enhance the poor dispersibility of 2D nanomaterials currently used to reinforce cement-based materials, and that they can pave the way for the effective application of 2D nanomaterials to cement-based materials.