One-pot approach for synthesis of multi-layered nanosheets of N-dopped graphene derived from chitosan for reinforcing cement mortar

Abstract

The synthesis of graphene via traditional methods has several drawbacks, such as the release of poisonous gases, Most of these techniques are time-consuming and tedious, besides the absence of control over the structural composition of graphene during synthesis. In this study, a facile approach for the synthesis of graphene densely doped with nitrogen (N-dopped graphene (NG)) from novel precursor chitosan throughout the direct solvothermal treatment of chitosan under mild circumstances at 250 °C and 270 °C. Cetyltrimethylammonium bromide (CTAB) and ammonia are utilized as structural directing agents. FTIR, XRD, CHNS/O elemental analysis, XPS, and Raman spectroscopy are utilized to elucidate the chemical composition and purity of N-dopped graphene. The surface morphology of NG is studied by using SEM, HR-TEM, and selected area electron diffraction (SAED). The results approved that, the one-pot, single-step approach is a simple and cost-effective technique for producing a high throughput of NG, of charming microstructure features, including good graphitization, low oxidation state, good exfoliation level, and very extended lateral dimension sheets. Profound visions on the growing mechanism have been proposed. The incorporation effect of NG to cement mortar is also studied. Two percentages of NG 0.05 wt% and, 0.10 wt% from the total cement mass were utilized. A microstructural investigation of incorporated NG on cement mortar is studied by conducting AFM, and SEM. Furthermore, workability and mechanical characterizations including, compressive strength, and flexural strength are investigated. Also, the dynamic mechanical parameters including storage modulus and loss factor are studied. It is noticed that the workability decreased from 14.8 % to 7.8 % with the addition of 0.05 wt% and 0.1 wt% NG respectively. However, the maximum increments of the compressive strength were 35 % for the mortar containing 0.1 wt% NG and flexural strength increased three times than the unmodified one. Also, the cement mortar containing 0.1 wt% NG has a storage modulus of 12 MPa compared to unmodified 1 MPa and has the lowest loss factor (damping coefficient). These results verified that incorporating NG nanosheets in cement has a positive effect on reinforcing cement mortar.

Keywords: Cement mortar; Chitosan; DMA; Graphene; Mechanical properties; Nanosheets.