مطالعه بر روی خصوصیات پراکندگی، مکانیکی و بافت صفحات گرافن
Abstract
1- Introduction
2- Materials and methods
3- Results and discussion
4- Discussion
5- Conclusions
References
Abstract
In this study, the influences of ultrasonic and surfactants on the dispersion of graphene sheets in water were evaluated using UV–vis spectroscopy, and homogenous dispersions of graphene sheets in water were obtained by using sodium dodecyl benzene sulfonate (SDBS). Then, the highly dispersed graphene sheets were introduced to cement paste through high-speed mixing, and the mechanical and microstructural properties of graphene-modified cement material was evaluated. Experiment results indicated that the addition of 0.025 wt% graphene sheets increased the 7-day composite compressive strength by 14.9%, the flexural strength by 23.6% and direct tensile strength by 15.2%. X-ray diffraction (XRD) analysis showed that the addition of graphene sheets lowered the orientation index of calcium hydroxide (CH) crystals significantly. Moreover, mercury intrusion porosimetry (MIP) and microscope imaging (SEM) indicated that a high degree of dispersion of graphene sheets was achieved, and the two-dimensional graphene sheets promote hydration and suppress the extension process of cracks.
Introduction
As a main component of concrete, cement is the most widely used binder material in the world. However, one of cementitious materials’ biggest drawbacks is their quasi-brittle nature and poor resistance to crack formation. Thus, many studies have been carried out to combine nano-fiber with cementitious composites to enhance their microstructure and mechanical properties, and results showed a small amount of carbon nanotubes (CNTs) can restrain the propagation of microcracks and improve the fracture toughness of the nanocomposites [1–3]. However, CNTs tend to agglomerate, hindering their dispersion in solvents because of their super high length-diameter ratio [4]. As a two-dimensional nanomaterial, graphene is the basic structural element of other allotropes, including graphite, CNTs and fullerenes [5,6]. The theoretical specific surface area (SSA) of graphene can reach 2630 m2 /g, which is much larger than that reported to date for CNTs [7]. In addition, it has an intrinsic tensile strength of 130 GPa and a Young’s modulus of 1 TPa [8]. Due to its remarkable mechanical performance, great attention is paid to the graphene as the nano reinforcing material in cement with greatest potential. Development of aqueous dispersions incorporating higher concentrations of graphene sheets would facilitate scalable production of graphene sheets modified concrete [9]. Thorough dispersion of graphene sheets in water is the key first step toward achieving uniform dispersions of graphene within cementitious composites [10]. Different surface treatments have been investigated for improving the hydrophilic property of graphene. Current processing methods involve acid treatment [2], oxidation via heating [11], ozone treatment [12] and silane treatment [13].