# Multifunctional Graphene-Concrete Composites: Performance and Mechanisms
## 3 Results and Discussion
### Material Characterization  
As shown in Figure 5a, the two-dimensional lamellar structure of the graphene material is clearly visible, exhibiting areas of light and dark contrast. This variation is attributed to interactions between the graphene and the substrate, as well as thermal stress and other factors that lead to the formation of folds and ripples.  
X-ray diffraction (XRD) analysis was conducted using a 20 kV X-ray diffractometer (model DX-2700 BH) produced by Dandong Haoyuan Instrument Co., Ltd. located in Dandong City, China, with a 20 range from 10 to 70 degrees. As depicted in Figure 5b, a narrower half-height width typically indicates a larger grain size and fewer lattice defects, suggesting that the graphene possesses a higher degree of crystallinity. Furthermore, a sharp diffraction peak is observed at an angle of 26.3\({}^{\circ}\), corresponding to the graphene crystal surface. According to calculations based on Bragg's law, the interlayer spacing of the graphene is approximately 0.34 nm.  
Figure 4: (**a**) A physical image of the experimental process. (**b**) A schematic diagram of the experimental process.  
Raman spectroscopy is an effective technique for assessing the quality of graphene by characterizing its bonding structure. Raman analysis was conducted using a LabRam HR 800 Raman spectrometer produced by HORIBA Jobin Yvon Company located in Paris, France, with a scanning range of 0 to 4000 cm\({}^{-1}\). As illustrated in Figure 5c, the Raman spectrum of graphene exhibits three characteristic peaks: the D peak at 1318 cm\({}^{-1}\), the G peak at 1580 cm\({}^{-1}\), and the 2D peak at 2628 cm\({}^{-1}\)[34]. The D peak is relatively weak and corresponds to the vibrations of sp\({}^{3}\) hybridized carbon atoms, which are typically associated with defects or edges in the graphene lattice. In contrast, the G peak is the sharpest and most intense, representing the fundamental lattice vibration mode of graphene, arising from the in-plane vibrations of sp\({}^{2}\) hybridized carbon atoms. The 2D peak is a symmetric single peak that results from a biphonon resonance process; it possesses high intensity and serves as a key indicator for determining the number of graphene layers. The intensity ratios (I(D)/I(G)) and (I(2D)/I(G)) are used to assess the quality of graphene. The intensity ratio of the D-band to the G-band, I(D)/I(G) = 0.47, indicates a low defect density and high crystallinity, confirming the better quality of the CVD-grown graphene. Furthermore, the intensity ratio of the 2D-band to the G-band, I(2D)/I(G) = 0.48, suggests the multi-layer structural characteristics of the graphene studied [35,36]. S multilayer graphene exhibits high potential in the field of photothermal conversion due to its broadband light absorption, efficient electron phonon coupling, and controllable number of layers.  
X-ray photoelectron spectroscopy (XPS) analysis was conducted using a PHI Quantera XPS system to determine the elemental composition of the graphene. As presented in Figure 6, curve fitting of the high-resolution XPS spectra revealed peak intensities for the elements O, N, and C at 20,455.58, 54,383.66, and 215,663.8, respectively, with corresponding binding energies of 532.36 eV for O, 399.26 eV for N, and 284.83 eV for C. The C1s spectral peak is particularly significant, as it represents the 1 s electron binding energy of carbon atoms in graphene. The symmetry and sharpness of the C1s peak indicate that the carbon atoms are in a highly uniform sp\({}^{2}\) hybridization state and exhibit good crystallinity.